Polyester film with adhesion-promoting layer, film article, optical laminate, laminate article, polarizing plate, panel, surface plate, image display panel, and image display device

Abstract

This polyester film with an adhesion-promoting layer includes a polyester film and an adhesion-promoting layer on the polyester film. The degree of in-plane orientation is 0.150 to 0.195. The average value of δq / δa of the surface of the adhesion-promoting layer is 1.80 or less. δa represents the arithmetic mean value of phase signals on the surface of the adhesion-promoting layer. δq represents a root mean square of phase signals on the surface of the adhesion-promoting layer.

Description

Polyester film with easy-adhesion layer, film article, optical laminate, laminate article, polarizing plate, panel, surface plate, image display panel, and image display device

[0001] The present disclosure relates to a polyester film with an easy-adhesion layer, a film article, an optical laminate, a laminate article, a polarizing plate, a panel, a faceplate, and an image display device.

[0002] Various optical laminates are arranged in image display devices such as liquid crystal display devices, organic EL display devices, micro LED display devices, mini LED display devices, quantum dot display devices, and laser hologram display devices for the purposes of improving image visibility and suppressing scratches on the device surface, etc. Optical laminates can also be arranged in show windows, painting covers, etc. for the purposes of improving the visibility of articles, protecting articles, etc.

[0003] An optical laminate includes a plastic film and a functional layer laminated on the plastic film. Many optical laminates include an easy-adhesion layer located on the plastic film. The easy-adhesion layer improves adhesion between the plastic film and the functional layer in the optical laminate. The plastic film is treated as a film with an easy-adhesion layer laminated thereon.

[0004] As a plastic film for an optical laminate, a triacetyl cellulose film with small optical anisotropy has been preferably used. However, TAC film has problems with mechanical strength. This problem becomes more pronounced in TAC films used in large-screen image display devices. In this specification, "triacetyl cellulose film" is also referred to as "TAC film."

[0005] Therefore, polyester films such as polyethylene terephthalate films have been proposed as an alternative to TAC films (see, for example, Patent Document 1). In this specification, "polyethylene terephthalate films" are also referred to as "PET films."

[0006] Image display devices such as liquid crystal display devices and organic EL display devices output polarized light. When a PET film is used in such image display devices, a rainbow interference pattern called rainbow unevenness may occur. The rainbow interference pattern is caused by the in-plane retardation of the PET film. The rainbow interference pattern reduces visibility. As a countermeasure against rainbow unevenness, it has been proposed to significantly increase the in-plane retardation of the PET film (for example, Patent Document 1).

[0007] A PET film with an extremely large in-plane retardation as disclosed in Patent Document 1 can be obtained by uniaxially stretching a PET film, but uniaxially stretched films have problems such as being prone to tearing in the stretching direction.

[0008] Contrary to Patent Document 1, one possible measure to address rainbow unevenness is to reduce the in-plane retardation of the PET film.

[0009] Patent Document 1: JP 2011-107198 A Patent Document 2: JP 2012-32819 A Patent Document 3: JP 2016-6530 A Patent Document 4: WO 2021 / 200884

[0010] A PET film having a small in-plane retardation can be obtained by, for example, reducing the stretching ratio, but the mechanical strength of the PET film is reduced when the stretching ratio is reduced.

[0011] The PET films described in Patent Documents 2 and 3 have a smaller in-plane retardation without reducing the stretching ratio compared to general-purpose biaxially stretched PET films. In the PET films described in Patent Documents 2 and 3, the in-plane retardation is reduced by, for example, reducing the difference in stretching ratio between the MD direction, which is the machine direction, and the TD direction, which is the width direction.

[0012] In a PET film in which the in-plane retardation is reduced without reducing the stretching ratio, and in a polyester film with an easy-adhesion layer containing this PET film, the planar orientation degree ΔP tends to be large. However, the present inventors have confirmed that a high planar orientation degree of a polyester film with an easy-adhesion layer causes other problems. In a polyester film with an easy-adhesion layer having a high planar orientation degree ΔP, the adhesion between the easy-adhesion layer and the polyester film may be reduced.

[0013] This problem can be solved by selecting the material for the easy-adhesion layer. However, this solution limits the range of material options for the easy-adhesion layer, which places constraints on product design. For this reason, this solution is not very practical. Furthermore, when optically designing the entire optical laminate, if an easy-adhesion layer made of a specific material is present on the PET film, this also places constraints on the material selection for the functional layer formed on the easy-adhesion layer.

[0014] The present disclosure aims to improve the adhesion between a polyester film and an easy-adhesion layer in a polyester film with an easy-adhesion layer having a high degree of planar orientation.

[0015] The invention described in Patent Document 4 aims to solve the same problems as those described above in the present disclosure. The optical laminate described in Patent Document 4 includes, in this order, a polyester film with an easy-adhesion layer, a concave-convex layer, and an antifouling layer. According to paragraphs 0073 and 0122 of Patent Document 4, the optical laminate of Patent Document 4 improves the adhesion between the easy-adhesion layer and the polyester film by utilizing the surface shape of the concave-convex layer and the slipperiness with the antifouling layer. That is, Patent Document 4 improves the adhesion between the easy-adhesion layer and the polyester film in an optical laminate in which a functional layer is laminated on a polyester film with an easy-adhesion layer. As is clear from the evaluation results of Comparative Example 6 described below, the polyester film with an easy-adhesion layer of Patent Document 4 fails to improve the adhesion between the easy-adhesion layer and the polyester film before the functional layer is laminated. As demonstrated in the examples described below, the present disclosure improves the adhesion between the easy-adhesion layer and the polyester film in a polyester film with an easy-adhesion layer before the functional layer is laminated on it.

[0016] According to one embodiment of the present disclosure, a film with an easy-adhesion layer comprises a polyester film and an easy-adhesion layer, the degree of planar orientation being 0.150 or more and 0.195 or less, and the average value of δq / δa on the surface of the easy-adhesion layer being 1.125 or more and 1.80 or less. <Calculation of the average value of δq / δa> A 10 μm × 10 μm area on the surface of the easy-adhesion layer is measured using the phase mode of an atomic force microscope. From this measurement, a distribution of phase signals on the surface of the easy-adhesion layer is obtained. The unit of the phase signal is [deg]. The arithmetic mean value of the phase signal shown in the following formula 1 is defined as δa. The root mean square of the phase signal shown in the following formula 2 is defined as δq. (In the following equations 1 and 2, the X and Y axes are placed on a reference surface indicating the average value of the phase signal, the Z axis is the axis perpendicular to the reference surface, and the curved surface of the phase signal is f(x, y). In the following equations 1 and 2, the size of the area where δa and δq are calculated is Lx and Ly. In the following equations 1 and 2, Ar = Lx × Ly.) Seven measurement and evaluation areas of 2 μm × 2 μm are selected from the measurement area of ​​10 μm × 10 μm. δa, δq, and δq / δa of the seven measurement and evaluation areas are calculated. The average value of δq / δa is calculated based on δq / δa at five locations, excluding the maximum and minimum values ​​from the δq / δa at the seven locations.

[0017] According to the present disclosure, in a polyester film with an easy-adhesion layer having a high degree of planar orientation, the adhesion between the polyester film and the easy-adhesion layer can be improved.

[0018] FIG. 1 is a diagram for explaining an embodiment of the present disclosure, and is a longitudinal sectional view showing an example of a polyester film with an easy-adhesion layer. FIG. 2 is a perspective view showing an example of a film article including a plurality of polyester films with easy-adhesion layers shown in FIG. 1. FIG. 3 is a diagram for explaining this embodiment, and is a longitudinal sectional view showing an example of an optical laminate. FIG. 4 is a perspective view showing an example of a laminate article including a plurality of optical laminates shown in FIG. 3. FIG. 5 is a sectional view showing an example of a polarizing plate including a polyester film with an easy-adhesion layer and an optical laminate. FIG. 6 is a sectional view showing an example of a panel including a polyester film with an easy-adhesion layer, and an example of a surface plate including a polyester film with an easy-adhesion layer and an optical laminate. FIG. 7 is a sectional view showing an example of an image display panel and an image display device including a polyester film with an easy-adhesion layer and an optical laminate. FIG. 8A is a diagram for explaining a bending test. FIG. 8B is a diagram for explaining a bending test. FIG. 8C is a diagram for explaining a bending test. FIG. 9 is a diagram schematically showing an optical laminate manufacturing apparatus used for conveyance evaluation.

[0019] One embodiment of the present disclosure relates to the following <1> to <19>.

[0020] <1> A polyester film with an easy-adhesion layer, comprising a polyester film and an easy-adhesion layer, wherein the degree of planar orientation is 0.150 or more and 0.195 or less, and the average value of δq / δa on the surface of the easy-adhesion layer is 1.125 or more and 1.80 or less. <Calculation of the average value of δq / δa> A 10 μm × 10 μm region on the surface of the easy-adhesion layer is measured using an atomic force microscope in phase mode. From this measurement, a distribution of phase signals on the surface of the easy-adhesion layer is obtained. The unit of the phase signal is [deg]. δa is the arithmetic mean value of the phase signal shown in the following formula 1. δq is the root mean square of the phase signal shown in the following formula 2. In the following formulas 1 and 2, the orthogonal coordinate axes X and Y are placed on a reference surface showing the average value of the phase signal, the axis perpendicular to the reference surface is the Z axis, and the curved surface of the phase signal is f(x, y). In the following formulas 1 and 2, the sizes of the regions for calculating δa and δq are Lx and Ly. In the following formulas 1 and 2, Ar = Lx x Ly. Seven measurement and evaluation regions of 2 μm x 2 μm are selected from a measurement region of 10 μm x 10 μm. δa, δq, and δq / δa are calculated for each of the seven measurement and evaluation regions. The maximum and minimum values ​​of δq / δa are excluded from the seven measurement and evaluation regions, and the average value of δq / δa is calculated based on the remaining five measurement and evaluation regions.

[0021] <2> The polyester film with an easy-adhesion layer according to <1>, wherein a coefficient of variation of δq / δa calculated based on the δq / δa values ​​at the five positions is 0.150 or less.

[0022] <3> The polyester film with an easy-adhesion layer according to <1> or <2>, wherein nx and ny satisfy the following relationship, where nx is the refractive index in the in-plane slow axis direction and ny is the refractive index in the in-plane direction perpendicular to the slow axis: nx - ny ≦ 0.0300

[0023] <4> The polyester film with an easy-adhesion layer according to any one of <1> to <3>, having a thickness of 10 μm or more and 75 μm or less.

[0024] <5> The polyester film with an easy-adhesion layer according to any one of <1> to <4>, wherein an in-plane retardation is 2000 nm or less.

[0025] <6> The polyester film with an easy-adhesion layer according to any one of <1> to <4>, wherein an in-plane retardation is 1,800 nm or more and 2,800 nm or less.

[0026] <7> The polyester film with an easy-adhesion layer according to any one of <1> to <6>, wherein the Nz coefficient is greater than 2.0.

[0027] <8> A film article comprising a plurality of the polyester films with an easy-adhesion layer according to any one of <1> to <7>.

[0028] <9> The film article according to <8>, which is wound around a winding axis.

[0029] <10> An optical laminate comprising the polyester film according to any one of <1> to <7>, and one or more functional layers on the easy-adhesion layer.

[0030] <11> The optical laminate according to <10>, wherein, of the one or more functional layers, a functional layer in contact with the easy-adhesion layer contains a cured product of an ionizing radiation-curable resin composition.

[0031] <12> The optical laminate according to <10> or <11>, wherein the surface of the optical laminate on the side having the functional layer has a contact angle with pure water of 80 degrees or more.

[0032] <13> A laminate article comprising a plurality of the optical laminates according to any one of <10> to <12>.

[0033] <14> The laminate article according to <13>, which is wound around a winding axis.

[0034] <15> A polarizing plate comprising a first transparent protective plate, a polarizer, and a second transparent protective plate in this order, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate according to any one of <10> to <12>, and the polyester film with an easy-adhesion layer is located between the functional layer and the polarizer.

[0035] <16> A panel comprising a support plate and the polyester film with an easy-adhesion layer according to any one of <1> to <7>.

[0036] <17> A surface plate comprising a support plate and the optical laminate according to any one of <10> to <12>, wherein the polyester film with an easy-adhesion layer is located between the functional layer and the support plate.

[0037] <18> An image display panel comprising a display element and the optical laminate according to any one of <10> to <12>.

[0038] <19> An image display device including the image display panel according to <18>.

[0039] The polyester film with an easy-adhesion layer, the film article, the optical laminate, the laminate article, the polarizing plate, the surface plate, the image display panel, and the image display device according to the present embodiment will be described below.

[0040] In this specification, the expression "AA to BB" as a numerical range means "not less than AA and not more than BB."

[0041] In this specification, multiple upper limit candidate values ​​and multiple lower limit candidate values ​​for a numerical range may be described in separate sentences. In this description, the numerical range may be constructed by combining any one upper limit candidate value and any one lower limit candidate value. As an example, consider the description, "Parameter B may be A1 or more, A2 or more, or A3 or more. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of parameter B may be A1 or more and A4 or less, A1 or more and A5 or less, A1 or more and A6 or less, A2 or more and A4 or less, A2 or more and A5 or less, A2 or more and A6 or less, A3 or more and A4 or less, A3 or more and A5 or less, or A3 or more and A6 or less.

[0042] <<<Polyester Film with Easy-Adhesion Layer>>> The polyester film with an easy-adhesion layer according to the present embodiment includes a polyester film and an easy-adhesion layer located on the polyester film.

[0043] FIG. 1 is a longitudinal cross-sectional view showing an example of a polyester film with an easy-adhesion layer. As shown in FIG. 1, the polyester film 15 with an easy-adhesion layer includes a first surface 15a and a second surface 15b. The first surface 15a and the second surface 15b may be a pair of main surfaces of the polyester film 15 with an easy-adhesion layer. The polyester film 15 with an easy-adhesion layer includes, in order from the first surface 15a to the second surface 15b, an easy-adhesion layer 25 and a polyester film 20. In the illustrated example, the first surface 15a is composed of the easy-adhesion layer 25. In the illustrated example, the second surface 15b is composed of the polyester film 20. The polyester film 15 with an easy-adhesion layer is used in an optical laminate 10.

[0044] The polyester film with an easy-adhesion layer according to the present embodiment includes the following features (A) and (B): As will be described later, the combination of features (A) and (B) can improve the adhesion between the polyester film and the easy-adhesion layer in a polyester film with an easy-adhesion layer having high mechanical strength.

[0045] Feature (A): Planar orientation degree ΔP is 0.150 or more and 0.195 or less

[0046] Feature (B): The average value of δq / δa on the surface of the easy-adhesion layer is 1.125 or more and 1.80 or less.

[0047] <Calculation of the average value of δq / δa in feature B> A 10 μm × 10 μm region on the surface of the easy-adhesion layer is measured using the phase mode of an atomic force microscope. From this measurement, a distribution of phase signals on the surface of the easy-adhesion layer is obtained. The unit of the phase signal is [deg]. The arithmetic mean value of the phase signal shown in the following formula 1 is defined as δa. The root mean square of the phase signal shown in the following formula 2 is defined as δq. In the following formulas 1 and 2, the orthogonal coordinate axes X and Y are placed on a reference surface showing the average value of the phase signal, the axis perpendicular to the reference surface is defined as the Z axis, and the curved surface of the phase signal is defined as f(x, y). In the following formulas 1 and 2, the sizes of the region in which δa and δq are calculated are defined as Lx and Ly. In the following formulas 1 and 2, Ar = Lx × Ly. Seven measurement and evaluation regions of 2 μm × 2 μm are selected from the 10 μm × 10 μm measurement region. The δa, δq, and δq / δa values ​​are calculated for each of the seven measurement evaluation regions. The average value of δq / δa is calculated based on the δq / δa values ​​for five locations, excluding the maximum and minimum values ​​from the δq / δa values ​​for the seven locations.

[0048]

[0049]

[0050] <<Characteristics of Polyester Film with Adhesion Layer>> <Characteristic (A): Planar Orientation Degree ΔP> The polyester film with an adhesion layer has the above-mentioned characteristic that the planar orientation degree ΔP is 0.150 or more and 0.195 or less.

[0051] The degree of planar orientation ΔP is expressed by "ΔP = ((nx + ny) / 2) - nz". "nx" is the refractive index in the slow axis direction in the plane of the polyester film with an easy-adhesion layer. "ny" is the refractive index in the fast axis direction in the plane of the polyester film with an easy-adhesion layer. "nz" is the refractive index in the thickness direction of the polyester film with an easy-adhesion layer. The slow axis is the direction with the highest refractive index in the plane of the polyester film with an easy-adhesion layer. The fast axis is the direction perpendicular to the slow axis in the plane of the polyester film with an easy-adhesion layer.

[0052] In this specification, the refractive indices such as nx, ny, and nz, the plane orientation degree ΔP, the in-plane retardation, and the thickness direction retardation are values ​​for light with a wavelength of 589 nm unless otherwise specified. In this specification, the in-plane retardation is also referred to as "Re." In this specification, the thickness direction retardation is also referred to as "Rth."

[0053] Feature (A) specifies that the plane orientation degree ΔP, expressed by "((nx + ny) / 2) - nz", is 0.150 or more and 0.195 or less. The plane orientation degree ΔP is a parameter indicating the strength of orientation of the entire surface of the target film-like member.

[0054] As defined as feature (A), a lower limit is set for the planar orientation degree ΔP. By setting a lower limit for the planar orientation degree ΔP, excellent mechanical strength can be imparted to the polyester film with an easy-adhesion layer. From this viewpoint, the planar orientation degree ΔP may be 0.150 or more, 0.151 or more, 0.154 or more, 0.156 or more, 1.58 or more, 0.161 or more, or 0.176 or more.

[0055] According to the studies of the present inventors, the following findings were obtained. By setting the planar orientation degree ΔP of the polyester film with an easy-adhesion layer to 0.150 or more, it was possible to improve the mechanical strength. Furthermore, it was found that when both feature (A) and feature (B) are satisfied, the puncture resistance and bending resistance, which are among the mechanical strengths, can be effectively improved. Puncture resistance and bending resistance are indicators of local mechanical properties, and puncture resistance is an indicator of a more local mechanical property than bending resistance. It was confirmed that when both feature (A) and feature (B) are satisfied, puncture resistance, which is an evaluation index of local mechanical strength, can be extremely effectively improved compared to overall mechanical strength. By improving puncture resistance, it is possible to impart impact resistance to the polyester film with an easy-adhesion layer and the optical laminate, and to suppress the occurrence of local damage to the polyester film with an easy-adhesion layer and the optical laminate, such as the formation of through holes.

[0056] For example, when handling, such as during the production of an optical laminate, the polyester film with an easy-adhesion layer is bent, which can cause localized damage to the polyester film with an easy-adhesion layer. For example, holes can be formed in the polyester film with an easy-adhesion layer. Recently, as display devices have become larger, optical laminates and polyester films with an easy-adhesion layer have also become larger. Since larger polyester films with an easy-adhesion layer can be bent with a large curvature, localized damage is likely to occur in the polyester film with an easy-adhesion layer. Furthermore, optical laminates including polyester films with an easy-adhesion layer are used for applications in which the film is folded during use, i.e., for foldable applications. Even when used in foldable applications, localized damage is likely to occur in the polyester film with an easy-adhesion layer.

[0057] Puncture resistance is a mechanical property that has become increasingly important in recent years. The present inventors have confirmed that the mechanical strength of a polyester film with an easy-adhesion layer can be improved by setting a lower limit for the planar orientation degree ΔP. When a lower limit for the planar orientation degree ΔP is set together with characteristic (B), puncture resistance can be improved. When characteristic (B) is satisfied, puncture resistance exhibits a stronger correlation with the planar orientation degree ΔP than when characteristic (B) is not satisfied.

[0058] Conventionally, attention has been focused on scratch resistance rather than pure mechanical strength as a mechanical property. Examples of evaluation tests for scratch resistance include pencil hardness and steel wool resistance. Scratch resistance does not necessarily correlate with puncture resistance. In fact, the present inventors have confirmed that polyester films with an easy-adhesion layer having high pencil hardness sometimes have insufficient puncture resistance. In light of these circumstances, the effect of stably improving puncture resistance by combining feature (A) and feature (B) is a unique effect that exceeds the range predicted from the current state of the art.

[0059] The details of the mechanism by which the combination of feature (A) and feature (B) improves puncture resistance are not clear. It is presumed that feature (A) improves the overall orientation, and feature (B) can homogenize the mechanical properties from a more local perspective than puncture resistance, thereby stably improving not only the overall mechanical strength but also more local bending resistance and puncture resistance, which is an evaluation index of more local mechanical strength than bending resistance. However, the present disclosure is not bound by this presumption.

[0060] In feature (A), the planar orientation degree ΔP has an upper limit. By setting an upper limit for the planar orientation degree ΔP, damage such as tearing or breakage of the polyester film with an easy-adhesion layer can be suppressed. If the planar orientation degree ΔP exceeds 0.195, the bending resistance and puncture resistance may be reduced. From this viewpoint, the planar orientation degree ΔP may be 0.195 or less, 0.193 or less, 0.191 or less, 0.189 or less, or 0.187.

[0061] The degree of planar orientation ΔP may be 0.150 to 0.195, 0.150 to 0.193, 0.150 to 0.191, 0.150 to 0.189, or 0.150 to 0.187. The degree of planar orientation ΔP may be 0.151 to 0.195, 0.151 to 0.193, 0.151 to 0.191, 0.151 to 0.189, or 0.151 to 0.187. The degree of planar orientation ΔP may be 0.154 or more and 0.195 or less, 0.154 or more and 0.193 or less, 0.154 or more and 0.191 or more, 0.154 or more and 0.189 or less, or 0.154 or more and 0.187 or less. The degree of planar orientation ΔP may be 0.156 or more and 0.195 or less, 0.156 or more and 0.193 or less, 0.156 or more and 0.191 or more, 0.156 or more and 0.189 or less, or 0.156 or more and 0.187 or less. The degree of planar orientation ΔP may be 0.158 or more and 0.195 or less, 0.158 or more and 0.193 or less, 0.158 or more and 0.191 or more, 0.158 or more and 0.189 or less, or 0.158 or more and 0.187 or less. The degree of planar orientation ΔP may be 0.161 to 0.195, 0.161 to 0.193, 0.161 to 0.191, 0.161 to 0.189, or 0.161 to 0.187. The degree of planar orientation ΔP may be 0.176 to 0.195, 0.158 to 0.193, 0.158 to 0.191, 0.158 to 0.189, or 0.158 to 0.187.

[0062] The nx, ny, nz, plane orientation degree ΔP, and the in-plane retardation Re and thickness direction retardation Rth of the polyester film with an easy-adhesion layer are values ​​determined using a retardation measurement device "RETS-100" manufactured by Otsuka Electronics Co., Ltd. Measurements are not performed on the easy-adhesion layer or polyester film peeled from the polyester film with an easy-adhesion layer, but on the polyester film with an easy-adhesion layer. The determination of each value using "RETS-100" is performed by the following steps (P1) to (P6).

[0063] (P1) First, before starting measurement, the light source is turned on for 60 minutes or more. By turning on the light source for 60 minutes, the output of the light source is stabilized. After that, the rotating analyzer method is selected, and the θ mode (a mode for measuring the angular phase difference and calculating Rth) is selected. By selecting the θ mode, the stage becomes a tilting rotating stage.

[0064] (P2) Next, the following measurement conditions are input into the measurement device. Retardation measurement range: rotary analyzer method Measurement spot diameter: φ5 mm Tilt angle range: -40° to 40° Measurement wavelength range: 400 to 800 nm Also, the "average refractive index N of the film" and "film thickness" are input. For the "average refractive index N of the film," the average refractive index of the polyester film contained in the polyester film with an easy-adhesion layer to be measured is input. When the polyester film used is a PET film, "1.617" is input as the "average refractive index N of the film." For the "film thickness," the thickness of the polyester film with an easy-adhesion layer, measured by the method described below, is input.

[0065] (P3) Then, background data is acquired without placing a sample in the measurement device. The measurement device is a closed system. Background data is acquired every time the light source is turned on.

[0066] (P4) Next, a sample is placed in the measuring device. When multiple samples are taken out from the polyester film with an easy-adhesion layer to be measured, the orientation of the multiple samples is aligned. Specifically, alignment is achieved by the following procedure. Arrows indicating the first reference direction and the first side in the first reference direction for the polyester film with an easy-adhesion layer to be measured are attached to each of the multiple samples taken out from the polyester film with an easy-adhesion layer. Arrows indicating the second reference direction and the first side in the second reference direction are attached to the sample stage on which the samples are sequentially placed. When each sample is placed on the sample stage, the first reference direction and the second reference direction are parallel, and the first side in the first reference direction and the first side in the second reference direction are aligned.

[0067] (P5) Measurement begins. First, the measurement device identifies the slow axis while rotating the sample 360°. Next, the measurement device presents options for the slow axis and fast axis, and the slow axis is selected. Once the slow axis is selected, the measurement device measures the retardation (Re) while rotating the sample stage around the slow axis. The measurement device measures the retardation (Re) for several wavelengths within the set measurement wavelength range (400 nm to 800 nm) at 10° increments within the set tilt angle range (-40° to 40°). Of the obtained measurements, the measurement value for a tilt angle of 0° and a wavelength of 589 nm is taken as the retardation (Re) value of the sample being measured.

[0068] (P6) Next, select the command "Display three-dimensional refractive index." At this time, a data table will be displayed, but this data table will not be used as the measurement result. Select the command "Set button." Then, enter the "average refractive index N of the film" and the "film thickness."

[0069] For "average refractive index N of film", input the average refractive index of the polyester film contained in the polyester film with an easy-adhesion layer to be measured. If the polyester film used is a PET film, "1.617" is input as the "average refractive index N of film". For "film thickness", input the thickness of the polyester film with an easy-adhesion layer measured by the method described below. This outputs the measured value for the polyester film with an easy-adhesion layer to be measured.

[0070] Here, measurement results of the refractive index nx, refractive index ny, refractive index nz, thickness direction retardation Rth, and plane orientation degree ΔP are obtained. Measurement results are output for each parameter at several wavelengths. Of the obtained measurement values, the measurement value at a wavelength of 589 nm is used as the refractive index nx, refractive index ny, refractive index nz, thickness direction retardation Rth, and plane orientation degree ΔP values ​​for the sample being measured.

[0071] Each of nx, ny, nz, ΔP, Re, and Rth is measured at seven locations. The maximum and minimum values ​​are excluded from the seven measured values, and the average value of the remaining five measured values ​​is calculated. This average value is used as each of the values ​​of nx, ny, nz, ΔP, Re, and Rth.

[0072] Before starting measurements of nx, ny, nz, the plane orientation degree ΔP, the in-plane retardation Re, and the thickness direction retardation Rth, the measurement sample is placed in a measurement environment of 23°C ± 2°C and 50% ± 5% relative humidity for 16 hours.

[0073] <Feature B: Average value of δq / δa> The polyester film with an easy-adhesion layer has the above-mentioned feature (B) that the average value of δq / δa on the surface of the easy-adhesion layer is 1.125 or more and 1.80 or less. The "average value of δq / δa" is specified as follows.

[0074] A 10 μm x 10 μm area on the surface of the easy-adhesion layer is measured using the phase mode of an atomic force microscope. In the example shown in FIG. 1, a 10 μm x 10 μm area on the surface of the first surface 15a is the measurement target. This measurement obtains a distribution of phase signals on the surface of the easy-adhesion layer. The unit of the phase signal is [deg]. "δa" is the arithmetic mean value of the phase signal shown in the following equation 1. "δq" is the root mean square of the phase signal shown in the following equation 2.

[0075] In the following formulas 1 and 2, the X and Y axes are placed on a reference surface indicating the average value of the phase signal, the axis perpendicular to the reference surface is the Z axis, and the curved surface of the phase signal is f(x, y). In the following formulas 1 and 2, the sizes of the regions for calculating δa and δq are Lx and Ly. In the following formulas 1 and 2, Ar = Lx × Ly.

[0076] Seven measurement and evaluation areas of 2 μm × 2 μm are selected from a measurement area of ​​10 μm × 10 μm. δa, δq, and δq / δa are calculated for each of the seven measurement and evaluation areas. The maximum and minimum values ​​of δq / δa are excluded from the seven measurement and evaluation areas, and the average value of δq / δa is calculated based on the remaining five measurement and evaluation areas. The calculated average value is the average value of δq / δa.

[0077] The seven measurement and evaluation regions may partially overlap, provided that the overlapping ratio between any one measurement and evaluation region and the other six measurement and evaluation regions is 25% or less in terms of the area of ​​the measurement and evaluation region.

[0078] Other measurement conditions for measuring the average value of δq / δa will be described later.

[0079]

[0080]

[0081] In the absence of an easy-adhesion layer, even if a functional layer is formed on a polyester film, the adhesion of an optical laminate having the polyester film and the functional layer cannot be improved. Also, even if an easy-adhesion layer is formed on a polyester film, if the average value of δq / δa on the surface of the easy-adhesion layer exceeds 1.80, the adhesion of an optical laminate having a polyester film, an easy-adhesion layer, and a functional layer in this order cannot be improved.

[0082] The technical significance of the average value of δq / δa on the surface of the adhesive layer will be explained below.

[0083] δa and δq are parameters related to the phase signal when a predetermined region on the surface of the easy-adhesion layer is measured in the phase mode of an atomic force microscope. The unit of the phase signal is [deg]. The phase signal indicates the viscoelasticity of the surface of the easy-adhesion layer. An atomic force microscope measures the physical properties of the surface by scanning the surface of the sample with a tiny probe attached to a leaf spring. In the phase mode, measurements are made while vibrating the probe, making it possible to map changes in the vibration phase within the plane. Therefore, in the phase mode, it is possible to map the contrast resulting from differences in the viscoelasticity of the surface components.

[0084] δa is the arithmetic mean value of the phase signal in a specified region. δq is the root mean square of the phase signal in a specified region. The root mean square emphasizes values ​​far from the arithmetic mean value. Even if the value of the arithmetic mean value δa is the same, if the variation in the phase signal in a specified region is large, the average value of the root mean square δq will be large. Even if the value of the arithmetic mean value δa is the same, if the variation in the phase signal in a specified region is large, the average value of δq / δa will be large. Conversely, even if the value of the arithmetic mean value δa is the same, if the variation in the phase signal in a specified region is small, the average value of δq / δa will be small. In other words, an easy-adhesion layer with a small arithmetic mean value of δq / δa has phase signals concentrated near the arithmetic mean value of the phase signal in a specified region, indicating small variation in the phase signal in the specified region. Since the phase signal indicates the viscoelasticity of the surface of the easy-adhesion layer, an easy-adhesion layer with a small average value of δq / δa indicates small changes in viscoelasticity in a specified region.

[0085] Note that the phase signal indicates the relative amount of change within the same image. Therefore, it is generally not possible to compare δa and δq of different samples. In this disclosure, we focus on δq / δa, which is the ratio of δa to δq. As described above, δq / δa is a parameter that indicates the phase variation within a sample and is a dimensionless parameter. Therefore, δq / δa can be said to be appropriate as a parameter for comparing the degree of phase variation between different samples.

[0086] As described above, an easy-adhesion layer having a small average value of δq / δa shows a small change in viscoelasticity in a predetermined region. A polyester film including an easy-adhesion layer having a small average value of δq / δa can improve the adhesion between the easy-adhesion layer and the polyester film. The adhesion of the optical laminate is thought to be improved for the following reasons.

[0087] When another component comes into contact with the functional layer of the optical laminate, a certain stress is generated. The stress is transmitted to the interface between the polyester film and the adhesive layer via the functional layer and the adhesive layer. The manner in which the stress is transmitted varies depending on the viscoelasticity of the adhesive layer. Therefore, if the in-plane viscoelasticity of the adhesive layer changes significantly, the magnitude of the stress transmitted to the interface between the polyester film and the adhesive layer will vary depending on the location within the plane. Therefore, if the average value of δq / δa of the adhesive layer is large, large stress is applied to specific locations within the plane, making the optical laminate more susceptible to interfacial delamination. On the other hand, if the average value of δq / δa of the adhesive layer is small, the stress is dispersed within the plane, which is thought to suppress interfacial delamination of the optical laminate and achieve high adhesion. It is understood that if the average value of δq / δa of the adhesive layer is small, it is less likely that a starting point for delamination will form. However, the present disclosure is not bound by this assumption.

[0088] One possible reason why the viscoelasticity of the adhesive layer varies from place to place is the compatibility of the components constituting the adhesive layer, etc. For example, the viscoelasticity of the adhesive layer can be made uniform by improving the compatibility of the components contained in the coating liquid used to form the adhesive layer.

[0089] The average value of δq / δa is affected by the compatibility of the coating liquid for forming the easy-adhesion layer and the phase separation state of the components contained in the coating liquid. For example, even if the resin composition constituting the easy-adhesion layer is the same, the average value of δq / δa can be adjusted depending on the compatibility of the coating liquid and the phase separation state of the components. The average value of δq / δa can also be adjusted by changing the phase separation state of the easy-adhesion layer depending on the drying conditions and curing conditions when forming a cured film from the coating liquid.

[0090] Another possible reason for the difference in viscoelasticity of the adhesive layer from place to place is the variation in molecular orientation of the polyester film. As will be described later, by increasing the Nz coefficient to more than 2.0, the viscoelasticity of the adhesive layer can be made uniform.

[0091] The average value of δq / δa may be 1.80 or less, 1.79 or less, 1.74 or less, 1.71 or less, 1.68 or less, 1.65 or less, 1.61 or less, 1.59 or less, 1.56 or less, or 1.38 or less. The smaller the average value of δq / δa, the more homogeneous the viscoelasticity of the surface of the easy-adhesion layer. By setting an upper limit to the average value of δq / δa, uniformity of the mechanical properties can be ensured, and the adhesion between the polyester film and the easy-adhesion layer can be improved.

[0092] If the viscoelasticity of the surface of the adhesive layer is too uniform, the components of the functional layer will not easily penetrate into the adhesive layer. Therefore, if the viscoelasticity of the surface of the adhesive layer is too uniform, the adhesion between the adhesive layer and the functional layer may be reduced. From this perspective, the average value of δq / δa may be 1.125 or more, 1.13 or more, 1.20 or more, 1.25 or more, 1.31 or more, or 1.33 or more.

[0093] The average value of δq / δa may be 1.125 or more and 1.80 or less, 1.125 or more and 1.77 or less, 1.125 or more and 1.74 or less, 1.125 or more and 1.71 or less, 1.125 or more and 1.68 or less, 1.125 or more and 1.65 or less, 1.125 or more and 1.61 or less, 1.125 or more and 1.59 or less, 1.125 or more and 1.56 or less, or 1.125 or more and 1.38 or less. The average value of δq / δa may be 1.13 or more and 1.80 or less, 1.13 or more and 1.77 or less, 1.13 or more and 1.74 or less, 1.13 or more and 1.71 or less, 1.13 or more and 1.68 or less, 1.13 or more and 1.65 or less, 1.13 or more and 1.61 or less, 1.13 or more and 1.59 or less, 1.13 or more and 1.56 or less, or 1.13 or more and 1.38 or less. The average value of δq / δa may be 1.20 or more and 1.80 or less, 1.20 or more and 1.77 or less, 1.20 or more and 1.74 or less, 1.20 or more and 1.71 or less, 1.20 or more and 1.68 or less, 1.20 or more and 1.65 or less, 1.20 or more and 1.61 or less, 1.20 or more and 1.59 or less, 1.20 or more and 1.56 or less, or 1.20 or more and 1.38 or less. The average value of δq / δa may be 1.25 or more and 1.80 or less, 1.25 or more and 1.77 or less, 1.25 or more and 1.74 or less, 1.25 or more and 1.71 or less, 1.25 or more and 1.68 or less, 1.25 or more and 1.65 or less, 1.25 or more and 1.61 or less, 1.25 or more and 1.59 or less, 1.25 or more and 1.56 or less, or 1.25 or more and 1.38 or less. The average value of δq / δa may be 1.31 or more and 1.80 or less, 1.31 or more and 1.77 or less, 1.31 or more and 1.74 or less, 1.31 or more and 1.71 or less, 1.31 or more and 1.68 or less, 1.31 or more and 1.65 or less, 1.31 or more and 1.61 or less, 1.31 or more and 1.59 or less, 1.31 or more and 1.56 or less, or 1.31 or more and 1.38 or less.The average value of δq / δa may be 1.33 or more and 1.80 or less, 1.33 or more and 1.77 or less, 1.33 or more and 1.74 or less, 1.33 or more and 1.71 or less, 1.33 or more and 1.68 or less, 1.33 or more and 1.65 or less, 1.33 or more and 1.61 or less, 1.33 or more and 1.59 or less, 1.33 or more and 1.56 or less, or 1.33 or more and 1.38 or less.

[0094] The average value of δq / δa on the surface of the adhesive layer is a value in a predetermined 10 μm × 10 μm region. The proportion of the area where the value of δq / δa is 1.80 or less in the total area of ​​the surface of the adhesive layer is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 98% or more, and most preferably 100%.

[0095] In the present disclosure, δa can be calculated using the above-mentioned Equation 1. Equation 1 uses the equation for arithmetic mean height in ISO 25178-2:2012. In the equation for arithmetic mean height in ISO 25178-2:2012, altitude is used as the data for the Z axis. In Equation 1, a phase signal [deg] is used as the data for the Z axis, rather than altitude. That is, δa and the arithmetic mean height in ISO 25178-2:2012 differ in that the former uses a phase signal [deg] as the data for the Z axis, while the latter uses altitude [μm] as the data for the Z axis.

[0096] In the present disclosure, δq can be calculated using Equation 2 above. Equation 2 uses the formula for root mean square height in ISO 25178-2:2012. The formula for root mean square height in ISO 25178-2:2012 uses altitude as the data for the Z axis. Equation 2 uses a phase signal [deg] instead of altitude as the data for the Z axis. That is, δq and the root mean square height in ISO 25178-2:2012 differ in that the former uses a phase signal [deg] as the data for the Z axis, while the latter uses altitude [μm] as the data for the Z axis.

[0097] The average value of δq / δa can be calculated by the following steps Q1 to Q4. (Q1) A 10 μm x 10 μm area on the surface of the adhesive layer is measured using an atomic force microscope in phase mode. As an example, when measuring using an SPM-9600 manufactured by Shimadzu Corporation, it is preferable to adjust the P gain, I gain, and offset. (Q2) Seven 2 μm x 2 μm measurement and evaluation areas are selected from the 10 μm x 10 μm measurement area. (Q3) δa, δq, and δq / δa are calculated within the seven selected measurement and evaluation areas. (Q4) The average value of δq / δa is calculated based on the δq / δa values ​​at five locations, excluding the maximum and minimum values ​​from the seven δq / δa values.

[0098] In the above A1, an example of the atomic force microscope is the product name "SPM-9600" manufactured by Shimadzu Corporation. Measurement using the atomic force microscope is not performed on the easy-adhesion layer peeled off from the polyester film with the easy-adhesion layer, but on the surface (first surface 15a) of the polyester film with the easy-adhesion layer.

[0099] In A2 above, the selected 2 μm x 2 μm region is selected from a region where the maximum height of the amplitude measured with an atomic force microscope is 90 nm or less. The maximum height is the maximum height Sz of ISO 25178-2:2012. By selecting the 2 μm x 2 μm region from a region where Sz is 90 nm or less, the effects of foreign matter and defects can be suppressed. The seven measurement and evaluation regions are preferably selected so that they do not overlap with each other, but they may overlap with each other. If the measurement and evaluation regions overlap, the overlap rate between any measurement and evaluation region and the other six measurement and evaluation regions is 25% or less based on the area of ​​the measurement and evaluation region. The overlap rate between any measurement and evaluation region and the other six measurement and evaluation regions is more preferably 12% or less, and even more preferably 5% or less.

[0100] In the above A2, the 2 μm × 2 μm measurement and evaluation area is selected from an area where the arithmetic mean height of the amplitude measured by the atomic force microscope is 10 nm or less in order to suppress the influence of foreign matter and defects. The arithmetic mean height is the arithmetic mean height Sa according to ISO 25178-2:2012.

[0101] As described above, the polyester film with an easy-adhesion layer according to the present embodiment has the above-mentioned features (A) and (B). Feature (A) enables the mechanical strength of the polyester film with an easy-adhesion layer to be improved. Feature (B) enables the adhesion between the easy-adhesion layer and the polyester film in the polyester film with an easy-adhesion layer to be improved. Therefore, the combination of features (A) and (B) can solve the problem of improving the adhesion between the polyester film and the easy-adhesion layer in a polyester film with an easy-adhesion layer having a high degree of planar orientation, and can also solve the problem of improving the adhesion between the polyester film and the easy-adhesion layer while imparting high mechanical strength to the polyester film with an easy-adhesion layer.

[0102] As already mentioned, the combination of feature (A) and feature (B) can stably improve the mechanical strength of the polyester film with an easy-adhesion layer, and in particular, the puncture resistance of the polyester film with an easy-adhesion layer can be stably improved. More specifically, the combination of feature (A) and feature (B) has a synergistic effect, which can stably improve local mechanical strength such as puncture resistance and bending resistance.

[0103] It is believed that setting a lower limit for the planar orientation degree ΔP can improve mechanical strength. Additionally, according to the inventors' studies, it was believed that setting an upper limit for the planar orientation degree ΔP can suppress damage such as tearing and breakage, and as a result, improve bending resistance and puncture resistance. However, even polyester films with easy-adhesion layers in which the planar orientation degree ΔP was adjusted according to feature (A) unexpectedly sometimes exhibited insufficient bending resistance and puncture resistance. Test samples with insufficient bending resistance and puncture resistance were only a portion of all test samples. The inventors' confirmation revealed that the average δq / δa values ​​for polyester films with easy-adhesion layers that exhibited insufficient bending resistance and puncture resistance did not satisfy feature (B).

[0104] When the average value of δq / δa for a polyester film with an easy-adhesion layer satisfying characteristic (A) increased, the bending resistance or puncture resistance of about 10% to 20% of samples obtained from the same polyester film with an easy-adhesion layer became insufficient. The detailed mechanism by which this phenomenon occurs is unknown, but the following factors are presumed.

[0105] When the average value of δq / δa is large, for example, when the average value of δq / δa exceeds 1.80, it is expected that phase separation of the easy-adhesion layer is progressing. It is presumed that aggregation occurs in the easy-adhesion layer where phase separation has occurred. Aggregation in the easy-adhesion layer can be the starting point of defects such as cracks and breaks.

[0106] Furthermore, when the average value of δq / δa is large, for example, when the average value of δq / δa exceeds 1.80, the viscoelasticity of the adhesive layer varies within the plane, and the penetration state of the coating liquid for forming the functional layer into the adhesive layer is also not uniform within the plane. When another component comes into contact with the functional layer of the optical laminate, a certain stress is generated. The stress is transmitted to the interface between the polyester film and the adhesive layer via the functional layer and the adhesive layer. Due to the uneven penetration state, the stress is not transmitted uniformly, and local cohesive failure may occur within the adhesive layer. Local cohesive failure within the adhesive layer may be the starting point for defects such as cracks and breaks.

[0107] When evaluating the bending resistance and puncture resistance, an external force is applied locally to the polyester film with an easy-adhesion layer and the optical laminate. It is presumed that the external force is concentrated at a more localized defective portion located within the localized region to which the external force is applied, which may cause unexpected damage. However, the present disclosure is not bound by this presumption.

[0108] By setting an upper limit to the average value of δq / δa, molecular orientation can be made sufficiently uniform and the occurrence of local defects can be sufficiently suppressed. By setting an upper limit to the average value of δq / δa of the polyester film with an easy-adhesion layer to which appropriate mechanical strength has been imparted by feature (A), excellent bending resistance and excellent puncture resistance can be stably imparted. In other words, it is possible to effectively suppress insufficient bending resistance and puncture resistance in some of the multiple test samples obtained from the evaluation subject.

[0109] As described above, in order to ensure more stable and excellent bending resistance and puncture resistance, an upper limit is set for the average value of δq / δa. The average value of δq / δa may be 1.80 or less, 1.79 or less, 1.74 or less, 1.71 or less, 1.68 or less, 1.65 or less, 1.61 or less, 1.59 or less, 1.56 or less, or 1.38 or less.

[0110] Furthermore, when the average value of δq / δa for a polyester film with an easy-adhesion layer that satisfies characteristic (A) becomes small, in a proportion of about 10% to 20% of samples obtained from the same polyester film with an easy-adhesion layer, although the sample did not break, test marks remained on the sample, and it was determined that the puncture resistance and bending resistance were insufficient. The detailed mechanism by which this phenomenon occurs is unknown, but the following factors are presumed.

[0111] When the average value of δq / δa is extremely small, for example, when the average value of δq / δa is less than 1.125, it is considered that the film quality of the easy-adhesion layer is very homogeneous and no phase separation occurs in the easy-adhesion layer.When a certain external force is repeatedly applied to such a homogeneous easy-adhesion layer, the external force is not dispersed in the polyester film with an easy-adhesion layer, which is a combination of a homogeneous easy-adhesion layer and a polyester film having characteristic (A), and the polyester film with an easy-adhesion layer is repeatedly subjected to the external force at a certain position.As a result, by repeatedly bending the polyester film with an easy-adhesion layer and the optical laminate at a certain position, it is expected that although the polyester film with an easy-adhesion layer does not break, microcracks will occur in the easy-adhesion layer, forming test marks as cloudy areas.

[0112] Furthermore, when the average value of δq / δa is extremely small, for example, when the average value of δq / δa is less than 1.125, puncture resistance may be insufficient even if characteristic (A) is satisfied. When the average value of δq / δa is extremely small, the film quality of the easy-adhesion layer becomes very homogeneous. Due to this homogeneity, an impact external force that should be evaluated by puncture resistance can be applied to a very small position on the polyester film with an easy-adhesion layer, which is a combination of a homogeneous easy-adhesion layer and a polyester film having characteristic (A), without being propagated and dispersed in the plane direction within the polyester film with an easy-adhesion layer. As a result, even if characteristic (A) is satisfied, it is expected that puncture resistance may be insufficient, although with a low probability.

[0113] By setting a lower limit for the average value of δq / δa, it is possible to prevent the easy-adhesion layer from becoming excessively homogeneous. By setting a lower limit for the average value of δq / δa of the polyester film with an easy-adhesion layer to which appropriate mechanical strength has been imparted by feature (A), it is possible to stably impart excellent bending resistance and excellent puncture resistance. In other words, it is possible to effectively prevent some of the multiple test samples obtained from the evaluation subject from having insufficient bending resistance.

[0114] As described above, in order to ensure more stable and excellent bending resistance and puncture resistance, a lower limit is set for the average value of δq / δa. The average value of δq / δa may be 1.125 or more, 1.13 or more, 1.20 or more, 1.25 or more, 1.31 or more, or 1.33 or more.

[0115] <Feature B1: Coefficient of variation of δq / δa> The polyester film with an easy-adhesion layer may further have the following feature (B1) in addition to the features (A) and (B): Feature (B1): The coefficient of variation of δq / δa calculated based on δq / δa at five points is 0.150 or less.

[0116] The "δq / δa at five locations" in feature (B1) is the "δq / δa at five locations" used when calculating the average value of δq / δa defined in feature (B). The coefficient of variation is obtained by dividing the standard deviation of the object by the average value of the object. The coefficient of variation is a dimensionless value of the standard deviation and has no unit. The coefficient of variation defined in feature (B1) is the value obtained by dividing the standard deviation of δq / δa at five locations by the average value of δq / δa at five locations.

[0117] By setting an upper limit to the coefficient of variation of δq / δa, the viscoelasticity can be homogenized among five measurement and evaluation regions of 2 μm × 2 μm. By setting the coefficient of variation of δq / δa to 0.150 or less, the viscoelasticity of the easy-adhesion layer can be further homogenized. This allows the stress applied to the polyester film with the easy-adhesion layer to be more evenly distributed in-plane. This makes it less likely that interlayer delamination will occur, further improving the adhesion between the easy-adhesion layer and the polyester film. Furthermore, the adhesion between the easy-adhesion layer and the functional layer in an optical laminate using this polyester film with the easy-adhesion layer can also be further improved. From the viewpoint of improving adhesion, the coefficient of variation of δq / δa may be 0.150 or less, 0.143 or less, 0.130 or less, 0.110 or less, or 0.093 or less.

[0118] If the coefficient of variation of δq / δa is too small, it may be difficult for the components of the functional layer to penetrate into the adhesive layer, and it may be possible that the adhesion between the adhesive layer and the functional layer cannot be sufficiently improved. From this viewpoint, the coefficient of variation of δq / δa may be 0.010 or more, 0.025 or more, 0.040 or more, or 0.049 or more.

[0119] The coefficient of variation of δq / δa may be 0.010 to 0.150, 0.010 to 0.143, 0.010 to 0.130, 0.010 to 0.110, or 0.010 to 0.090. The coefficient of variation of δq / δa may be 0.025 to 0.150, 0.025 to 0.143, 0.025 to 0.130, 0.025 to 0.110, or 0.025 to 0.090. The coefficient of variation of δq / δa may be 0.040 to 0.150, 0.040 to 0.143, 0.040 to 0.130, 0.040 to 0.110, or 0.040 to 0.090. The coefficient of variation of δq / δa may be 0.049 to 0.150, 0.049 to 0.143, 0.049 to 0.130, 0.049 to 0.110, or 0.049 to 0.090.

[0120] <Feature A1: nx - ny> The polyester film with an easy-adhesion layer may further have the following feature (A1) in addition to features (A) and (B). Feature (A1): In the polyester film with an easy-adhesion layer, when the refractive index in the slow axis direction in the plane of the polyester film with an easy-adhesion layer is defined as nx and the refractive index in the direction perpendicular to the slow axis in the same plane as ny, nx and ny satisfy the following relationship: nx - ny ≦ 0.0300

[0121] By setting nx-ny to 0.0300 or less, rainbow unevenness caused by in-plane retardation can be suppressed. nx-ny may be 0.0300 or less, 0.0250 or less, 0.0240 or less, or 0.0230 or less.

[0122] In this specification, unless otherwise specified, rainbow unevenness refers to rainbow unevenness as seen with the naked eye.

[0123] If the nx-ny of the polyester film with an easy-adhesion layer is too small, it is difficult to suppress blackout. From this viewpoint, nx-ny may be 0.0050 or more, 0.0080 or more, 0.0100 or more, 0.0120 or more, or 0.0130 or more. Blackout is a phenomenon in which the entire surface becomes dark when light that has passed through a polarizer and a polyester film in this order is viewed through a polarizer such as polarized sunglasses.

[0124] The value of nx-ny of the polyester film with an easy-adhesion layer may be 0.0050 or more and 0.0300 or less, 0.0050 or more and 0.0250 or less, 0.0050 or more and 0.0240 or less, or 0.0050 or more and 0.0230 or less. The value of nx-ny of the polyester film with an easy-adhesion layer may be 0.0080 or more and 0.0300 or less, 0.0080 or more and 0.0250 or less, 0.0080 or more and 0.0240 or less, or 0.0080 or more and 0.0230 or less. The value of nx-ny of the polyester film with an easy-adhesion layer may be 0.0100 or more and 0.0300 or less, 0.0100 or more and 0.0250 or less, 0.0100 or more and 0.0240 or less, or 0.0100 or more and 0.0230 or less. The value of nx-ny of the polyester film with an easy-adhesion layer may be 0.0120 or more and 0.0300 or less, 0.0120 or more and 0.0250 or less, 0.0120 or more and 0.0240 or less, or 0.0120 or more and 0.0230 or less. The value of nx-ny of the polyester film with an easy-adhesion layer may be 0.0130 or more and 0.0300 or less, 0.0130 or more and 0.0250 or less, 0.0130 or more and 0.0240 or less, or 0.0130 or more and 0.0230 or less.

[0125] <Feature A2: In-plane retardation Re> The polyester film with an easy-adhesion layer may further have the following feature (A2) in addition to the features (A) and (B): Feature (A2): The polyester film with an easy-adhesion layer has an in-plane retardation Re of 2000 nm or less.

[0126] The in-plane retardation Re is a numerical value obtained by "(nx-ny) x T [nm]", where T is the thickness [nm] of the polyester film with an easy-adhesion layer. By setting an upper limit to the in-plane retardation, rainbow unevenness can be suppressed. From this viewpoint, the in-plane retardation of the polyester film with an easy-adhesion layer may be 2000 nm or less, 1600 nm or less, 1400 nm or less, 1200 nm or less, 1148 nm or less, 1100 nm or less, 1000 nm or less, or 950 nm or less.

[0127] Rainbow unevenness can also be suppressed by adjusting the functional layer and the light source. Furthermore, there are applications in which rainbow unevenness is not important. Therefore, the in-plane retardation of the polyester film is not limited to 2000 nm or less, and may be greater than 2000 nm.

[0128] By setting a lower limit for the in-plane retardation of the polyester film with an easy-adhesion layer, blackout can be suppressed. This is because a polyester film with an average in-plane retardation of less than 50 nm can hardly disturb linearly polarized light and transmits linearly polarized light as is, while a polyester film with an average in-plane retardation of 50 nm or more can disturb linearly polarized light. From this perspective, the in-plane retardation of the polyester film with an easy-adhesion layer may be 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 400 nm or more, 450 nm or more, or 497 nm or more.

[0129] The in-plane retardation of the polyester film with an easy-adhesion layer may be 50 nm or more and 2000 nm or less, 50 nm or more and 1600 nm or less, 50 nm or more and 1400 nm or less, 50 nm or more and 1200 nm or less, 50 nm or more and 1148 nm or less, 50 nm or more and 1100 nm or less, 50 nm or more and 1000 nm or less, or 50 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 100 nm or more and 2000 nm or less, 100 nm or more and 1600 nm or less, 100 nm or more and 1400 nm or less, 100 nm or more and 1200 nm or less, 100 nm or more and 1148 nm or less, 100 nm or more and 1100 nm or less, 100 nm or more and 1000 nm or less, or 100 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 150 nm or more and 2000 nm or less, 150 nm or more and 1600 nm or less, 150 nm or more and 1400 nm or less, 150 nm or more and 1200 nm or less, 150 nm or more and 1148 nm or less, 150 nm or more and 1100 nm or less, 150 nm or more and 1000 nm or less, or 150 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 200 nm or more and 2000 nm or less, 200 nm or more and 1600 nm or less, 200 nm or more and 1400 nm or less, 200 nm or more and 1200 nm or less, 200 nm or more and 1148 nm or less, 200 nm or more and 1100 nm or less, 200 nm or more and 1000 nm or less, or 200 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 250 nm or more and 2000 nm or less, 250 nm or more and 1600 nm or less, 250 nm or more and 1400 nm or less, 250 nm or more and 1200 nm or less, 250 nm or more and 1148 nm or less, 250 nm or more and 1100 nm or less, 250 nm or more and 1000 nm or less, or 250 nm or more and 950 nm or less.The in-plane retardation of the polyester film with an easy-adhesion layer may be 300 nm or more and 2000 nm or less, 300 nm or more and 1600 nm or less, 300 nm or more and 1400 nm or less, 300 nm or more and 1200 nm or less, 300 nm or more and 1148 nm or less, 300 nm or more and 1100 nm or less, 300 nm or more and 1000 nm or less, or 300 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 400 nm or more and 2000 nm or less, 400 nm or more and 1600 nm or less, 400 nm or more and 1400 nm or less, 400 nm or more and 1200 nm or less, 400 nm or more and 1148 nm or less, 400 nm or more and 1100 nm or less, 400 nm or more and 1000 nm or less, or 400 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 450 nm or more and 2000 nm or less, 450 nm or more and 1600 nm or less, 450 nm or more and 1400 nm or less, 450 nm or more and 1200 nm or less, 450 nm or more and 1148 nm or less, 450 nm or more and 1100 nm or less, 450 nm or more and 1000 nm or less, or 450 nm or more and 950 nm or less. The in-plane retardation of the polyester film with an easy-adhesion layer may be 497 nm or more and 2000 nm or less, 497 nm or more and 1600 nm or less, 497 nm or more and 1400 nm or less, 497 nm or more and 1200 nm or less, 497 nm or more and 1148 nm or less, 497 nm or more and 1100 nm or less, 497 nm or more and 1000 nm or less, or 497 nm or more and 950 nm or less.

[0130] <Feature A2a: In-plane retardation Re> The polyester film with an easy-adhesion layer may further have the following feature (A2a) in addition to the features (A) and (B): Feature (A2a): The polyester film with an easy-adhesion layer has an in-plane retardation Re of 1800 nm or more and 2800 nm or less.

[0131] A polyester film with an easy-adhesion layer, in which the in-plane retardation Re is adjusted to 1,800 nm or more and 2,800 nm or less according to feature (A2a), has excellent transportability. As demonstrated in the transport tests for Reference Examples A to E described below, the amount of change in transport speed during transport varies depending on the in-plane retardation Re of the polyester film with an easy-adhesion layer. By setting the in-plane retardation Re to 1,800 nm or more and 2,800 nm or less, fluctuations in the transport speed of the polyester film with an easy-adhesion layer can be suppressed, allowing the polyester film with an easy-adhesion layer to be stably transported at a constant speed. As a result, scratches and other damage to the polyester film with an easy-adhesion layer due to fluctuations in the transport speed can be suppressed.

[0132] The details of why the conveying property changes depending on the in-plane retardation Re are unclear. However, it is presumed that by setting the in-plane retardation Re to 1800 nm or more and 2800 nm or less, the balance between the three-dimensional rigidity and hardness of the long polyester film with an easy-adhesion layer becomes good, and the conveying speed becomes stable. The present disclosure is not bound by this presumption.

[0133] <Feature A3: Thickness Direction Retardation Rth> The polyester film with an easy-adhesion layer may further have the following feature (A3) in addition to the features (A) and (B): Feature (A3): The thickness direction retardation Rth of the polyester film with an easy-adhesion layer is 2000 nm or more.

[0134] The thickness direction retardation Rth is a numerical value obtained by "((nx+ny) / 2-nz)×T [nm]", where T is the thickness [nm] of the polyester film with an easy-adhesion layer. By setting a lower limit for the thickness direction retardation Rth, blackout can be suppressed when viewed not only from the front direction but also from an oblique direction. From this viewpoint, the thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 2000 nm or more, 3000 nm or more, 4000 nm or more, or 5000 nm or more.

[0135] The thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 15,000 nm or less, 12,000 nm or less, or 9,000 nm or less, so that Re / Rth falls within the range described below.

[0136] The thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 2000 nm or more and 15000 nm or less, 2000 nm or more and 12000 nm or less, or 2000 nm or more and 9000 nm or less. The thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 3000 nm or more and 15000 nm or less, 3000 nm or more and 12000 nm or less, or 3000 nm or more and 9000 nm or less. The thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 4000 nm or more and 15000 nm or less, 4000 nm or more and 12000 nm or less, or 4000 nm or more and 9000 nm or less. The thickness direction retardation Rth of the polyester film with an easy-adhesion layer may be 5,000 nm or more and 15,000 nm or less, 5,000 nm or more and 12,000 nm or less, or 5,000 nm or more and 9,000 nm or less.

[0137] <Feature A4: Re / Rth> The polyester film with an easy-adhesion layer may further have the following feature (A4) in addition to the features (A) and (B): Feature (A4): Re / Rth is 0.01 or more and 0.20 or less.

[0138] A small Re / Rth means that the degree of stretching of the polyester film approaches uniform biaxiality. By setting an upper limit for Re / Rth, the mechanical strength of the polyester film with an easy-adhesion layer can be improved. Furthermore, by setting an upper limit for Re / Rth, it is possible to prevent wrinkles from occurring in the polyester film with an easy-adhesion layer due to environmental changes, which can adversely affect visibility. From these viewpoints, Re / Rth may be 0.20 or less, 0.17 or less, or 0.15 or less. In order to exert the effects of setting Re / Rth within a predetermined range, it is preferable that the in-plane retardation of the polyester film with an easy-adhesion layer be within the above range.

[0139] If Re / Rth is too small, the orientation in the XY plane is high, but the orientation in the Z-axis direction is low, and the film tends to be brittle in the film thickness direction. Therefore, if Re / Rth is too small, the polyester film with the easy-adhesion layer may break when the polyester film with the easy-adhesion layer is attached to an adherend or peeled off from an adherend. From these viewpoints, the polyester film preferably has an Re / Rth of 0.01 or more, more preferably 0.03 or more, more preferably 0.05 or more, and more preferably 0.06 or more.

[0140] The Re / Rth of the polyester film with an easy-adhesion layer may be 0.01 or more and 0.20 or less, 0.01 or more and 0.17 or less, or 0.01 or more and 0.15 or less. The Re / Rth of the polyester film with an easy-adhesion layer may be 0.03 or more and 0.20 or less, 0.03 or more and 0.17 or less, or 0.03 or more and 0.15 or less. The Re / Rth of the polyester film with an easy-adhesion layer may be 0.05 or more and 0.20 or less, 0.05 or more and 0.17 or less, or 0.05 or more and 0.15 or less. The Re / Rth of the polyester film with an easy-adhesion layer may be 0.06 or more and 0.20 or less, 0.06 or more and 0.17 or less, or 0.06 or more and 0.15 or less.

[0141] <Feature A5: Nz Coefficient> The polyester film with an easy-adhesion layer may further have the following feature (A5) in addition to the features (A) and (B): Feature (A5): The Nz coefficient is greater than 2.0.

[0142] The Nz coefficient is a value obtained by "(Rth / Re)+0.5". As already explained, "Rth" is the retardation in the thickness direction of the polyester film with an easy-adhesion layer. As already explained, "Re" is the in-plane retardation of the polyester film with an easy-adhesion layer.

[0143] The Nz coefficient becomes small when the polyester film is uniaxially stretched or nearly uniaxially stretched. Near-uniaxial stretching includes cases where the stretching ratio in the first axis and the stretching ratio in the second axis are significantly different. Feature (A5) sets a lower limit for the Nz coefficient. A polyester film with an easy-adhesion layer that satisfies feature (A5) can be obtained by stretching the film at a certain stretching ratio or higher in each of two orthogonal directions. That is, a polyester film with an easy-adhesion layer that has feature (A5) includes a biaxially stretched polyester film.

[0144] As used herein, "biaxially stretched" means that the Nz coefficient is greater than 2.0. As used herein, "uniaxially stretched" means that the Nz coefficient is 2.0 or less.

[0145] The numerical range of the average value of δq / δa is specified in Feature (B). From the viewpoint of setting the average value of δq / δa to the upper limit specified in Feature (B) or less, it is effective to make the molecular orientation of the polyester film uniform.

[0146] For example, when a uniaxially stretched or nearly uniaxially stretched polyester film is used, there is a direction in which it is stretched at a large stretch ratio. The molecular orientation of the polyester film is homogenized to a certain extent along this stretching direction. However, the molecular orientation of the polyester film along a direction nonparallel to the stretching direction, such as a direction perpendicular to the stretching direction, tends to be nonuniform. If the molecular orientation of the polyester film is nonuniform, the wettability of the coating liquid for forming the adhesive layer on the polyester film decreases, and the coating liquid may be repelled by the polyester film. Repelling of the coating liquid may result in in-plane variation in the mechanical properties of the adhesive layer produced from the coating liquid, and even defects may occur. As a result, the average value of δq / δa increases.

[0147] In a polyester film with an easy-adhesion layer using a uniaxially stretched or nearly uniaxially stretched polyester film, it is not easy to stably achieve a sufficiently small average value of δq / δa.In a polyester film with an easy-adhesion layer that does not have feature (A5), it is not easy to stably achieve a mean value of δq / δa equal to or less than the upper limit specified by feature (B).

[0148] A polyester film with an easy-adhesion layer that satisfies feature (A5) has a small in-plane birefringence (nx-ny). When the in-plane birefringence is small, the molecular orientation of the polyester film is uniform in-plane. The quality and characteristics of an easy-adhesion layer formed by directly applying a coating liquid to a polyester film are easily affected by the underlying polyester film, partly because the thickness of the easy-adhesion layer is typically thin, less than 1 μm. Forming an easy-adhesion layer by applying a coating liquid to a polyester film with uniform in-plane molecular orientation can make the easy-adhesion layer uniform. Furthermore, the wettability of the coating liquid for forming an easy-adhesion layer on a polyester film with uniform in-plane molecular orientation can be excellent throughout the entire area. This also contributes to the formation of a uniform easy-adhesion layer. As a result, the average value of δq / δa can be stably set to be equal to or less than the upper limit specified in feature (B), thereby suppressing changes in mechanical properties and viscoelasticity within the easy-adhesion layer.

[0149] In addition, feature (A5) not only contributes to the formation of a homogeneous adhesive layer as described above, but also homogenizes the properties of the polyester film with an adhesive layer. A polyester film with a large in-plane birefringence (nx-ny) can have a variable transmittance depending on the vibration direction of light. A polyester film with an adhesive layer that satisfies feature (A5) can maintain a constant transmittance regardless of direction. A polyester film with an adhesive layer that satisfies feature (A5) can reduce the need for precise positioning taking into account the slow axis and transmission axis. Satisfying feature (A5) can homogenize the mechanical properties of the polyester film with an adhesive layer.

[0150] <Thickness of Polyester Film with Easy-Adhesion Layer> A lower limit may be set for the thickness of the polyester film with easy-adhesion layer. By setting a lower limit for the thickness of the polyester film with easy-adhesion layer, high mechanical strength can be imparted to the polyester film with easy-adhesion layer. High puncture resistance can be imparted to the polyester film with easy-adhesion layer. From this perspective, the thickness of the polyester film with easy-adhesion layer may be 10 μm or more, 21 μm or more, 25 μm or more, or 30 μm or more. By setting the thickness of the polyester film to 10 μm or more, when another member comes into contact with the second surface 15b (see FIG. 3 ), which is the opposite side to the functional layer of the optical laminate, stress is less likely to be transmitted to the interface between the polyester film and the easy-adhesion layer. This allows the polyester film and the easy-adhesion layer to be maintained in a stable, tightly adhered state.

[0151] An upper limit may be set for the thickness of the polyester film with an easy-adhesion layer. By setting an upper limit for the thickness of the polyester film with an easy-adhesion layer, the in-plane retardation Re can be reduced, and flexibility and bendability can be improved. From these viewpoints, the thickness of the polyester film with an easy-adhesion layer may be 75 μm or less, 60 μm or less, 55 μm or less, or 50 μm or less.

[0152] The thickness of the polyester film with an easy-adhesion layer may be 10 μm or more and 75 μm or less, 10 μm or more and 60 μm or less, 10 μm or more and 55 μm or less, or 10 μm or more and 50 μm or less. The thickness of the polyester film with an easy-adhesion layer may be 21 μm or more and 75 μm or less, 21 μm or more and 60 μm or less, 21 μm or more and 55 μm or less, or 21 μm or more and 50 μm or less. The thickness of the polyester film with an easy-adhesion layer may be 25 μm or more and 75 μm or less, 25 μm or more and 60 μm or less, 25 μm or more and 55 μm or less, or 25 μm or more and 50 μm or less. The thickness of the polyester film with an easy-adhesion layer may be 30 μm or more and 75 μm or less, 30 μm or more and 60 μm or less, 30 μm or more and 55 μm or less, or 30 μm or more and 50 μm or less.

[0153] The thickness of a polyester film with an easy-adhesion layer that does not have a functional layer laminated thereon is determined using measurements taken at 20 measurement points using a film thickness meter. The largest, second largest, smallest, and second smallest measurements are excluded from the measurements at the 20 measurement points, and the average of the measurements at the remaining 16 measurement points is taken as the thickness of the polyester film with an easy-adhesion layer. Nikon's "DigiMicro" may be used as a film thickness meter. Nikon's "DigiMicro" may use the "MS-5C" + "MH-15M" as the "stand" + "main body" and the "TC-101A" as the "counter."

[0154] The thickness of the polyester film with an easy-adhesion layer incorporated into the optical laminate is determined using a scanning transmission electron microscope (STEM). The cross section of the polyester film with an easy-adhesion layer to be evaluated or an optical laminate including the polyester film with the easy-adhesion layer is observed using a scanning transmission electron microscope, and the thickness of the polyester film with an easy-adhesion layer is measured from the image observed with the scanning transmission electron microscope. A measurement sample is prepared in which the cross section of the polyester film with an easy-adhesion layer is exposed, so that cross-sectional observation is possible. A microtome is used to prepare the sample. An example of the microtome is a microtome manufactured by Leica. An example of the scanning electron microscope is the "product number: S4800" manufactured by Hitachi High-Technologies Corporation.

[0155] The thickness of the object to be measured is measured at seven measurement points by cross-sectional observation using a scanning electron microscope. The maximum and minimum measurement values ​​are excluded from the measurements at the seven measurement points, and the average value of the measurements at the remaining five measurement points is taken as the thickness of the polyester film with an easy-adhesion layer. The seven measurement points are seven points located on a straight line at a pitch of 10 μm.

[0156] Before starting the thickness measurement, the measurement sample is placed in a measurement environment for 16 hours, where the temperature is 23°C ± 2°C and the relative humidity is 50% ± 5%.

[0157] In order to obtain the above-mentioned in-plane retardation Re and thickness direction retardation Rth, the thickness of the polyester film with an easy-adhesion layer is required. The thickness of the polyester film with an easy-adhesion layer determined by the above-mentioned method is used to determine the in-plane retardation Re and thickness direction retardation Rth.

[0158] <Transmission haze of polyester film with easy-adhesion layer> The transmission haze of the polyester film with easy-adhesion layer may be 3.0% or less, 2.0% or less, or 1.0% or less. The transmission haze of the polyester film with easy-adhesion layer has no particular lower limit. The transmission haze of the polyester film with easy-adhesion layer may be 0% or more than 0%.

[0159] A D65 light source is used to measure transmission haze. Before measuring transmission haze, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. When measuring transmission haze, the angle of incidence on the measurement sample is 0°. The measurement environment for measuring transmission haze is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The measurement sample is placed in the measurement environment for 16 hours before starting measurement. Other measurement conditions for measuring transmission haze are in accordance with JIS K7136:2000. A haze meter (product number: HM-150) manufactured by Murakami Color Research Laboratory may also be used to measure transmission haze.

[0160] When measuring the transmission haze of the polyester film with the easy-adhesion layer, the incident surface is the main surface that is closer to the polyester film than the easy-adhesion layer. For example, in the example shown in Figure 1, the incident surface when measuring the transmission haze is the second surface 15b.

[0161] The transmission haze is the arithmetic mean value of five measurements taken at five measurement positions on the measurement object, the five measurement positions being spaced at least 10 mm apart from each other.

[0162] <Total Light Transmittance of Polyester Film with Easy-Adhesion Layer> The total light transmittance of the polyester film with an easy-adhesion layer may be 80% or more, 85% or more, or 90% or more. The total light transmittance of the polyester film with an easy-adhesion layer has no particular upper limit. The total light transmittance of the polyester film with an easy-adhesion layer may be 100% or less, or may be less than 100%.

[0163] A D65 light source is used to measure the total light transmittance. Before measuring the total light transmittance of the polyester film with an easy-adhesion layer, the D65 light source is turned on for 15 minutes to stabilize the output of the D65 light source. The angle of incidence on the measurement sample when measuring the total light transmittance is 0°. The measurement environment when measuring the total light transmittance is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the measurement environment for 16 hours before starting the measurement. Other measurement conditions when measuring the total light transmittance are in accordance with JIS K7361-1:1997. A haze meter (product number: HM-150) manufactured by Murakami Color Research Laboratory may also be used to measure the total light transmittance.

[0164] The incident surface when measuring the total light transmittance of the polyester film with the easy-adhesion layer is the main surface closer to the polyester film than the easy-adhesion layer. For example, in the example shown in Figure 1, the incident surface when measuring the total light transmittance is the second surface 15b.

[0165] The total light transmittance is the arithmetic mean value of five measurements taken at five measurement positions on the evaluation object, the five measurement positions being at least 10 mm apart from each other.

[0166] <Ultraviolet transmittance> The spectral transmittance of the polyester film with the easy-adhesion layer at a wavelength of 380 nm may be 20% or less, or 10% or less. The spectral transmittance of the polyester film with the easy-adhesion layer at a wavelength of 380 nm has no particular lower limit. The spectral transmittance of the polyester film with the easy-adhesion layer at a wavelength of 380 nm may be 0% or more than 0%.

[0167] The spectral transmittance of the polyester film with an easy-adhesion layer at a wavelength of 380 nm is measured in accordance with JIS Z 8722:2009. The angle of incidence on the measurement sample when measuring the spectral transmittance is 0°. The geometric conditions for irradiation and reception when measuring the spectral transmittance are the geometric condition f specified in JIS Z8722:2009 and conditions including the direction of regular transmission (0°:di). Before measuring the spectral transmittance, the light source is turned on for 15 minutes to stabilize the light source output. The measurement environment for measuring the spectral transmittance is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The measurement sample is placed in the measurement environment for 16 hours before starting the measurement. Other measurement conditions for measuring the spectral transmittance are in accordance with JIS Z8722:2009.

[0168] The incident surface when measuring the spectral transmittance of the polyester film with the easy-adhesion layer is the main surface closer to the polyester film than the easy-adhesion layer. For example, in the example shown in Figure 1, the incident surface when measuring the spectral transmittance is the second surface 15b.

[0169] The spectral transmittance is the arithmetic mean value of five measurements taken at five measurement positions on the evaluation object, the five measurement positions being at least 10 mm apart from each other.

[0170] <<Layer Configuration of Polyester Film with Easy-Adhesion Layer>> The polyester film with an easy-adhesion layer includes a polyester film and an easy-adhesion layer.

[0171] The polyester film with an easy-adhesion layer may include a single polyester film. The polyester film included in the polyester film with an easy-adhesion layer may be a single layer. In other words, the polyester film included in the polyester film with an easy-adhesion layer may include a single layer.

[0172] The polyester film with an easy-adhesion layer may include a plurality of polyester films. The polyester film included in the polyester film with an easy-adhesion layer may be multilayered. The polyester film included in the polyester film with an easy-adhesion layer may include a plurality of layers.

[0173] The polyester film with an easy-adhesion layer may include a single easy-adhesion layer. The polyester film with an easy-adhesion layer may include multiple easy-adhesion layers. Multiple easy-adhesion layers may be laminated on one side of the polyester film with an easy-adhesion layer. Multiple easy-adhesion layers may be laminated on one side and the other side of the polyester film with an easy-adhesion layer.

[0174] As described above, regardless of the layer structure of the polyester film with an easy-adhesion layer, the degree of planar orientation ΔP is measured for the polyester film with an easy-adhesion layer. Regardless of the layer structure of the polyester film with an easy-adhesion layer, the measurement of δq / δa using an atomic force microscope is not performed on the easy-adhesion layer peeled off from the polyester film with an easy-adhesion layer, but on the surface of the easy-adhesion layer in the polyester film with an easy-adhesion layer. For example, when multiple easy-adhesion layers are laminated on one side of the polyester film, the measurement of δq / δa using an atomic force microscope is performed on the surface of the easy-adhesion layer that constitutes one surface of the polyester film with an easy-adhesion layer.

[0175] <<Polyester Film>> The polyester film is a layer that supports the easy-adhesion layer. The polyester film is a layer that supports a functional layer on the easy-adhesion layer. The polyester film has physical properties and a configuration that can impart the above-mentioned physical properties and configuration to the polyester film with an easy-adhesion layer. The polyester film may have the same characteristics as the polyester film with an easy-adhesion layer, such as feature (A), feature (A1), feature (A2), feature (A3), and feature (A4). The polyester film may have the same characteristics as the above-mentioned polyester film with an easy-adhesion layer in terms of transmission haze, total light transmittance, and ultraviolet transmittance.

[0176] <Thickness of Polyester Film> In order to improve the mechanical strength, the thickness of the polyester film may be 10 μm or more, 21 μm or more, 25 μm or more, or 30 μm or more. By making the thickness of the polyester film 10 μm or more, when another member comes into contact with a surface of the optical laminate closer to the polyester film with the easy-adhesion layer than the functional layer and stress is generated, the stress can be made less likely to be transmitted to the interface between the polyester film and the easy-adhesion layer.

[0177] In order to reduce the in-plane retardation of the polyester film with the adhesive layer and to improve the bending resistance of the polyester film with the adhesive layer, an upper limit may be set for the thickness of the polyester film, which may be 75 μm or less, 60 μm or less, 55 μm or less, or 50 μm or less.

[0178] The thickness of the polyester film may be 10 μm or more and 75 μm or less, 10 μm or more and 60 μm or less, 10 μm or more and 55 μm or less, or 10 μm or more and 50 μm or less. The thickness of the polyester film may be 21 μm or more and 75 μm or less, 21 μm or more and 60 μm or less, 21 μm or more and 55 μm or less, or 21 μm or more and 50 μm or less. The thickness of the polyester film may be 25 μm or more and 75 μm or less, 25 μm or more and 60 μm or less, 25 μm or more and 55 μm or less, or 25 μm or more and 50 μm or less. The thickness of the polyester film may be 30 μm or more and 75 μm or less, 30 μm or more and 60 μm or less, 30 μm or more and 55 μm or less, or 30 μm or more and 50 μm or less.

[0179] <Raw Materials for Polyester Film> Examples of polyesters constituting the polyester film include homopolymers obtained by polycondensation of dicarboxylic acids and diols; copolymers obtained by polycondensation of one or more dicarboxylic acids and two or more diols; copolymers obtained by polycondensation of two or more dicarboxylic acids and one or more diols; and blend resins in which one or more homopolymers and one or more copolymers are mixed.

[0180] The polyester film may contain additives, such as ultraviolet absorbers, lubricating particles such as inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light-resistant agents, flame retardants, heat stabilizers, antioxidants, antigelling agents, and surfactants.

[0181] The raw materials for the polyester film may be newly synthesized, naturally occurring, recycled, or a mixture of two or more of these.

[0182] Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, and dodecanedicarboxylic acid.

[0183] Examples of diols include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0184] The polyester film may contain polyethylene terephthalate, which can impart high mechanical strength to the polyester film.

[0185] Examples of polymerization methods for polyethylene terephthalate include a direct polymerization method in which terephthalic acid is directly reacted with ethylene glycol, and, if necessary, other dicarboxylic acid components and diol components; and a transesterification method in which a dimethyl ester of terephthalic acid is transesterified with ethylene glycol. In the transesterification method, the dimethyl ester of terephthalic acid may contain a methyl ester of another dicarboxylic acid, if necessary. In the transesterification method, the ethylene glycol may contain another diol component, if necessary.

[0186] The intrinsic viscosity of polyethylene terephthalate may be 0.45 or more and 0.70 or less. By setting the intrinsic viscosity to 0.45 or more, the tear resistance of the polyester film with an easy-adhesion layer can be improved. By setting the intrinsic viscosity to 0.70 or less, an increase in filtration pressure can be suppressed, and filtration accuracy can be improved.

[0187] <Layer structure of polyester film> The polyester film may have a single layer structure. The polyester film may have a multilayer structure. That is, the polyester film may include a single layer. The polyester film may include multiple layers.

[0188] The single-layer structure is advantageous in that its stretching is easily controlled. Therefore, the easy-adhesion layer of the single-layer structure can increase the planar orientation degree ΔP of the polyester film with the easy-adhesion layer without reducing the stretching ratios in the machine direction and the width direction, and by making the stretching ratios in both directions close to each other. Therefore, the single-layer structure, which is easy to control the stretching, is preferred in that it can increase the planar orientation degree ΔP of the polyester film with the easy-adhesion layer.

[0189] On the other hand, multilayer polyester films are preferred because it is easy to achieve effects by changing the composition of each layer. For example, a laminated polyester film consisting of at least three layers formed by coextrusion may be used as a polyester film with an easy-adhesion layer. In this example, by using a polyester with a low oligomer content in the surface layers on both sides of the laminated polyester film, the amount of oligomer precipitation after heat treatment can be suppressed.

[0190] (Stretching of Polyester Film) In order to achieve the degree of planar orientation ΔP defined in the above-mentioned feature (A), the stretching ratios in the machine direction and the width direction may be made close to each other without decreasing them. The polyester film may be a stretched film or a biaxially stretched film.

[0191] - Sequential Biaxial Stretching - In sequential biaxial stretching, the cast film is stretched in the machine direction, and then the polyester film is stretched in the width direction.

[0192] Stretching in the machine direction is usually performed by the difference in peripheral speed between a pair of stretching rolls. Stretching in the machine direction may be performed in one stage, or may be performed in multiple stages using multiple pairs of stretching rolls. In order to suppress excessive variations in optical properties such as the planar orientation degree ΔP and in-plane retardation, multiple nip rolls may be placed close to the stretching roll. The stretching ratio in the machine direction may be 2 times or more and 15 times or less, and in order to suppress excessive variations in optical properties such as the planar orientation degree ΔP and in-plane retardation, it may be 2 times or more and 7 times or less, 3 times or more and 5 times or less, or 3 times or more and 4 times or less.

[0193] In order to suppress excessive variations in physical properties such as the degree of planar orientation ΔP and the in-plane retardation, the stretching temperature may be set to a temperature equal to or higher than the glass transition temperature of the resin and equal to or lower than the glass transition temperature + 100° C. The stretching temperature when stretching a PET film may be 70° C. or higher and 120° C. or lower, 80° C. or higher and 110° C. or lower, or 95° C. or higher and 110° C. or lower.

[0194] Regarding the stretching temperature, if the stretching section at low temperature is shortened by, for example, increasing the temperature of the polyester film quickly, the average in-plane retardation tends to be small, whereas if the stretching section at low temperature is lengthened by, for example, increasing the temperature of the polyester film slowly, the orientation tends to be enhanced, and the average in-plane retardation tends to be large.

[0195] A layer having functions such as lubricity and antistatic properties may be formed on the polyester film stretched in the machine direction by in-line coating or off-line coating. In this specification, the layer formed by in-line coating or off-line coating is not counted as part of the number of layers constituting the polyester film.

[0196] Stretching in the width direction is usually carried out using a tenter method. In this stretching method, the polyester film is stretched in the width direction by conveying the film while holding both ends with clips. The stretching ratio in the width direction may be 2 to 15 times. From the viewpoint of suppressing excessive variation in physical properties such as the planar orientation degree ΔP and in-plane retardation of the polyester film with an easy-adhesion layer, the stretching ratio in the width direction may be 2 to 7 times, 3 to 6 times, or 4 to 5 times. The stretching ratio in the width direction may be higher than the stretching ratio in the machine direction.

[0197] One of the stretching ratios in the machine direction and the width direction may be higher than the other while the Nz coefficient is greater than 2.0. The stretching ratios in the machine direction and the width direction may be approximately the same, and the Nz coefficient may be greater than 2.0. According to these examples, the molecular orientation of the polyester film becomes uniform. A polyester film with uniform molecular orientation has excellent coating suitability. A polyester film with uniform molecular orientation can suppress large in-plane changes in the viscoelasticity of an easy-adhesion layer formed on the polyester film. From the viewpoint of adjusting the average value of δq / δa within the numerical range specified in feature (B), the stretching ratios in the machine direction and the width direction may be adjusted so that the Nz coefficient is greater than 2.0.

[0198] The stretching temperature may be equal to or higher than the glass transition temperature of the resin and equal to or lower than the glass transition temperature + 120°C. The stretching temperature may increase from the upstream to the downstream of the polyester film. The difference between the upstream stretching temperature and the downstream stretching temperature may be 20°C or higher, 30°C or higher, 35°C or higher, or 40°C or higher. When stretching a PET film, the first-stage stretching temperature may be 80°C or higher and 120°C or lower, 90°C or higher and 110°C or lower, or 95°C or higher and 105°C or lower.

[0199] In order to impart flatness and dimensional stability to the polyester film with an easy-adhesion layer, the sequentially biaxially stretched polyester film may be heat-treated in a tenter at a temperature equal to or higher than the stretching temperature but lower than the melting point. In the case of a PET film, heat setting may be performed in the range of 150°C to 255°C, or in the range of 200°C to 250°C. In order to suppress excessive variations in physical properties such as the degree of planar orientation ΔP and in-plane retardation, additional stretching of 1% to 10% may be performed in the first half of the heat treatment.

[0200] The polyester film may be heat-treated and then slowly cooled to room temperature before being wound up. If necessary, a relaxation treatment or the like may be performed on the polyester film during the heat treatment or slow cooling. The relaxation rate during the heat treatment may be 0.5% to 5%, 0.5% to 3%, 0.8% to 2.5%, or 1% to 2% in order to suppress excessive variations in physical properties such as the planar orientation degree ΔP and the in-plane retardation. The relaxation rate during slow cooling may be 0.5% to 3%, 0.5% to 2%, 0.5% to 1.5%, or 0.5% to 1.0% in order to suppress excessive variations in physical properties such as the planar orientation degree ΔP and the in-plane retardation. The temperature during slow cooling may be 80°C or higher and 150°C or lower, 90°C or higher and 130°C or lower, 100°C or higher and 130°C or lower, or 100°C or higher and 120°C or lower, in order to improve the flatness.

[0201] The conveying speed during production of the stretched polyester film may be 100 m / s or more and 300 m / s or less.

[0202] -Simultaneous Biaxial Stretching- In simultaneous biaxial stretching, the cast film is introduced into a simultaneous biaxial tenter, and the polyester film is conveyed while being held at both ends with clips, and the polyester film is stretched simultaneously and / or stepwise in the machine direction and width direction. Examples of simultaneous biaxial stretching machines include pantograph type, screw type, drive motor type, and linear motor type. With the drive motor type or linear motor type, the stretching ratio can be changed as desired, and relaxation treatment can be performed at any location.

[0203] The area ratio of the simultaneous biaxial stretching may be 6 to 50 times. From the viewpoint of suppressing excessive variations in physical properties such as the degree of planar orientation ΔP and in-plane retardation, the area ratio may be 8 to 30 times, 9 to 25 times, 9 to 20 times, or 10 to 15 times. In simultaneous biaxial stretching, the above-mentioned area ratio may be achieved while the stretch ratio in the machine direction and the stretch ratio in the width direction are set to 2 to 15 times. In the case of simultaneous biaxial stretching, in order to suppress in-plane orientation differences, the stretch ratios in the machine direction and the width direction may be set to be approximately the same, and the stretching speeds in the machine direction and the width direction may also be set to be approximately the same.

[0204] In order to suppress excessive variations in physical properties such as the degree of planar orientation ΔP and the in-plane retardation, the stretching temperature in the simultaneous biaxial stretching may be set to a temperature equal to or higher than the glass transition temperature of the resin and equal to or lower than the glass transition temperature + 120° C. The stretching temperature in the simultaneous biaxial stretching of the PET film may be 80° C. or higher and 160° C. or lower, 90° C. or higher and 150° C. or lower, or 100° C. or higher and 140° C. or lower.

[0205] In order to impart flatness and dimensional stability to the polyester film with the easy-adhesion layer, the simultaneously biaxially stretched polyester film may be subsequently subjected to a heat treatment at a temperature equal to or higher than the stretching temperature but lower than the melting point in a heat setting chamber in a tenter. The heat treatment conditions for the simultaneously biaxially stretched polyester may be the same as the heat treatment conditions described above for the sequentially biaxially stretched polyester.

[0206] <<Adhesion Layer>> The polyester film with an adhesion layer according to this embodiment includes an adhesion layer. Furthermore, in the polyester film with an adhesion layer according to this embodiment, the average δq / δa value on the surface of the adhesion layer is 1.125 or more and 1.80 or less, thereby enhancing the adhesion between the polyester film and the adhesion layer. Furthermore, the average δq / δa value on the surface of the adhesion layer is 1.125 or more and 1.80 or less, thereby making it difficult for defects to originate in the polyester film with an adhesion layer, thereby stabilizing the mechanical strength. In addition to ensuring this stability, the satisfaction of feature (A) also allows for stable improvement in puncture resistance and bending resistance. The adhesion layer has properties and a configuration that can impart the above-described properties and configuration to the polyester film with an adhesion layer.

[0207] The resin constituting the easy-adhesion layer is not particularly limited. Examples of the resin constituting the easy-adhesion layer include thermoplastic resins and thermosetting resins such as polyester resins, polyurethane resins, and acrylic resins, and thermoplastic resins are exemplified. Examples of the thermoplastic resin include polyester resins, polyurethane resins, and resins containing both polyester and polyurethane components. Polyester resins, polyurethane resins, and resins containing both polyester and polyurethane components can reduce the refractive index difference between the polyester film and the easy-adhesion layer, and the refractive index difference between the easy-adhesion layer and the uneven layer.

[0208] The polyurethane component can contribute to improving adhesion. The polyurethane component does not easily increase coating film strength. From this perspective, both a polyester component and a polyurethane component may be included. However, if the polyurethane component is too much relative to the polyester component, phase separation is likely to occur. As a result, the average value of δq / δa and the coefficient of variation of δq / δa tend to increase. Furthermore, because the polyurethane component is soft, if the polyurethane component is too much, the average value of δq / δa and the coefficient of variation of δq / δa tend to increase due to differences in in-plane crosslink density. From this perspective, in a resin containing both a polyester component and a polyurethane component, the mass ratio of the polyester component to the polyurethane component may be 95:5 to 60:40, or may be 90:10 to 60:40.

[0209] The number average molecular weight of the resin constituting the easy-adhesion layer may be 10,000 or more, or 15,000 or more. The number average molecular weight of the resin constituting the easy-adhesion layer may be 100,000 or less, or 60,000 or less. By setting the number average molecular weight of the resin constituting the easy-adhesion layer within the above range, cohesive failure of the easy-adhesion layer can be suppressed.

[0210] The glass transition temperature of the resin constituting the easy-adhesion layer may be 30° C. or higher, 50° C. or higher, or 70° C. or higher. The glass transition temperature of the resin constituting the easy-adhesion layer may be 120° C. or lower, 110° C. or lower, or 90° C. or lower.

[0211] By setting the glass transition temperature of the resin constituting the easy-adhesion layer to 30°C or higher, it is possible to prevent the easy-adhesion layer from flowing due to heat during processing, thereby preventing internal stress from occurring. This makes it easy to adjust the average value of δq / δa and the coefficient of variation of δq / δa within the above-mentioned numerical range. Examples of heat during processing include heat during the drying process of the functional layer coating liquid and heat caused by heating when laminating the optical laminate to a polarizer.

[0212] By setting the glass transition temperature of the resin constituting the easy-adhesion layer to 120°C or less, it is possible to suppress the generation of stress due to the difference in thermal behavior between the easy-adhesion layer and the polyester film caused by heat during processing. The generation of cracks or the like in the easy-adhesion layer due to the stress can be suppressed. For these reasons, by setting the glass transition temperature of the resin constituting the easy-adhesion layer to 120°C or less, it is easy to adjust the average value of δq / δa and the coefficient of variation of δq / δa within the above-mentioned numerical ranges.

[0213] The adhesive layer may contain an additive. Examples of the additive include a refractive index adjuster, a dye, a pigment, a leveling agent, a UV absorber, an antioxidant, and a light stabilizer; and a crosslinking agent for adjusting hardness or viscosity. Examples of the crosslinking agent include non-yellowing XDI-based, IPDI-based, and HDI-based isocyanates, and ionizing radiation-curable polyfunctional monomers.

[0214] The adhesion layer may be formed by an in-line coating method in which coating is carried out during the formation of the polyester film, or by an off-line coating method in which coating is carried out after the formation of the polyester film.

[0215] In the inline coating method and the offline coating method, a coating liquid for an easy-adhesion layer containing components constituting the easy-adhesion layer may be used. For example, the easy-adhesion layer may be formed by applying the coating liquid for an easy-adhesion layer to a polyester film using a general-purpose coating method and drying it. In this case, the drying time may be 120 seconds or less, or may be 90 seconds or less. By setting the drying time to 120 seconds or less, phase separation of the components constituting the easy-adhesion layer can be suppressed. This makes it easy to adjust the average value of δq / δa and the coefficient of variation of δq / δa within the above-mentioned ranges. If the drying time is too short, the coating surface may become rough and the optical properties may be deteriorated. From these viewpoints, the drying time may be 15 seconds or more, or may be 20 seconds or more. The drying time can be adjusted by the drying temperature and drying air speed.

[0216] The direction of the drying air may be opposite to the transport direction of the polyester film. By making the direction of the drying air opposite to the transport direction of the polyester film, the drying time of the coating liquid for the easy-adhesion layer can be dramatically shortened without excessively increasing the drying temperature.

[0217] The drying temperature of the coating liquid for the easy-adhesion layer may be 50° C. or higher and 200° C. or lower, or 60° C. or higher and 150° C. or lower. By setting the drying temperature to 50° C. or higher, the drying time of the coating liquid for the easy-adhesion layer can be shortened, thereby suppressing phase separation of the components constituting the easy-adhesion layer. By setting the drying temperature to 200° C. or lower, thermal decomposition of the components constituting the easy-adhesion layer can be suppressed.

[0218] The coating liquid for the adhesive layer may contain a solvent. The solvent can dissolve the components constituting the adhesive layer in the coating liquid for the adhesive layer. The solvent can disperse the components constituting the adhesive layer in the coating liquid for the adhesive layer. The solvent can adjust the viscosity of the coating liquid for the adhesive layer.

[0219] Examples of solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; alcohols such as isopropanol, butanol, and cyclohexanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers such as propylene glycol monomethyl ether acetate; cellosolve acetates; sulfoxides such as dimethyl sulfoxide; amides such as dimethylformamide and dimethylacetamide; etc. The coating liquid for the easy-adhesion layer may contain one solvent or two or more of the solvents listed above.

[0220] If the drying time of the solvent in the coating liquid for the adhesive layer is too long, the components constituting the adhesive layer are likely to undergo phase separation. Therefore, the solvent in the coating liquid for the adhesive layer may contain a solvent with a high evaporation rate.

[0221] On the other hand, if the drying time of the solvent in the coating liquid for the easy-adhesion layer is too short, the coating surface is likely to become rough. Therefore, the coating liquid for the easy-adhesion layer may contain a solvent having an extremely fast evaporation rate and a solvent having an appropriately fast evaporation rate.

[0222] In this specification, a solvent having an extremely fast evaporation rate means a solvent having an evaporation rate of 280 or more, where the evaporation rate of butyl acetate is taken as 100. In addition, in this specification, a solvent having a moderately fast evaporation rate means a solvent having an evaporation rate of 150 or more but less than 280, where the evaporation rate of butyl acetate is taken as 100.

[0223] The evaporation rate of a solvent having an extremely fast evaporation rate may be 320 or more and 430 or less, or 340 or more and 400 or less. Examples of solvents having an extremely fast evaporation rate include methyl ethyl ketone with an evaporation rate of 370 and normal heptane with an evaporation rate of 362.

[0224] The evaporation rate of a solvent having a moderately fast evaporation rate may be 170 or more and 250 or less, or 180 or more and 220 or less. Examples of solvents having a moderately fast evaporation rate include toluene with an evaporation rate of 200 and propyl acetate with an evaporation rate of 214.

[0225] In the solvents of the coating liquid for the adhesive layer, the mass ratio of the solvent having an extremely fast evaporation rate to the solvent having an appropriately fast evaporation rate may be 50:50 to 90:10, or may be 70:30 to 85:15.

[0226] From the viewpoint of suppressing phase separation of the coating liquid for the adhesive layer, the solid content concentration of the coating liquid for the adhesive layer may be 2% by mass or more, or 4% by mass or more. The solid content concentration of the coating liquid for the adhesive layer may be 30% by mass or less, or 10% by mass or less. The solid content concentration of the coating liquid for the adhesive layer may be adjusted by the content of the solvent.

[0227] The composition of the coating liquid for the adhesive layer is not particularly limited. The coating liquid for the adhesive layer may be a solvent-based liquid. Compared with a water-based coating liquid for the adhesive layer, a solvent-based coating liquid for the adhesive layer can improve the adhesion between the adhesive layer and the polyester film after a moist heat resistance test.

[0228] It is believed that a water-based coating liquid for an easy-adhesion layer can reduce the environmental load. However, a water-based coating liquid for an easy-adhesion layer needs to be dried at a high temperature, and further needs to be dried at a high temperature for a long time. Therefore, it cannot be said that a water-based coating liquid for an easy-adhesion layer can contribute to reducing the environmental load. A water-based coating liquid for an easy-adhesion layer can reduce processing efficiency during mass production when compared with a solvent-based coating liquid for an easy-adhesion layer.

[0229] In a polyester film with an easy-adhesion layer that is used in a display device, a PVA resin can be added to the easy-adhesion layer for the purpose of improving adhesion with a polarizer. The PVA resin can be used as the main material of the polarizer. Poval manufactured by Kuraray is known as a raw material for polarizers. An example of Poval manufactured by Kuraray is the product name "PVA28-98" (formerly the product name "PVA-117"). The degree of polymerization of PVA28-98 (formerly the product name: PVA-117) is about 1700, and the molecular weight is 30,000 to 100,000.

[0230] The PVA resin added to the adhesion layer makes the coating liquid for the adhesion layer aqueous, and as a result, the addition of the PVA resin to the adhesion layer can reduce the adhesion between the adhesion layer and the polyester film.

[0231] The dry coating amount of the easy-adhesion layer is 0.05 g / m ２ 0.75g / m or more ２ The thickness of the easy-adhesion layer is not particularly limited. The thickness of the easy-adhesion layer may be 10 nm or more and 600 nm or less, 20 nm or more and 300 nm or less, or 50 nm or more and 200 nm or less. From the viewpoint of suppressing interference fringes, the thickness of the easy-adhesion layer may be thin.

[0232] The thickness of each layer included in the polyester film with an easy-adhesion layer or the optical laminate, for example, the thickness of the easy-adhesion layer and the functional layer, is measured in the same manner as the above-mentioned measurement method for measuring the thickness of the polyester film with an easy-adhesion layer incorporated in the optical laminate. That is, the cross section of the polyester film with an easy-adhesion layer or the optical laminate is observed with a scanning transmission electron microscope, and the thickness of the layer to be measured is measured from the image observed with the scanning transmission electron microscope. To enable cross-sectional observation, a measurement sample is prepared in which the cross section of the layer to be measured is exposed. A microtome is used to prepare the sample. An example of the microtome is a microtome manufactured by Leica. An example of the scanning electron microscope is the "Product No. S4800" manufactured by Hitachi High-Technologies Corporation.

[0233] The thickness of the layer to be measured is measured at 20 measurement points by cross-sectional observation using a scanning electron microscope. From the measurements at the 20 measurement points, the maximum measurement value, the second maximum measurement value, the minimum measurement value, and the second smallest measurement value are excluded, and the average value of the measurements at the remaining 16 measurement points is taken as the thickness of the layer to be measured. The 20 measurement points are located on a straight line at a pitch of 10 μm.

[0234] <<Size, Shape, etc. of Polyester Film with Easy-Adhesion Layer>> The polyester film with an easy-adhesion layer may be in the form of a sheet cut to a predetermined size. The size of the sheet is not particularly limited, but the maximum diameter is approximately 2 inches or more and 500 inches or less. The "maximum diameter" refers to the maximum length when any two points on the polyester film with an easy-adhesion layer are connected. For example, if the polyester film with an easy-adhesion layer is rectangular, the diagonal line of the rectangle is the maximum diameter. If the polyester film with an easy-adhesion layer is circular, the diameter of the circle is the maximum diameter.

[0235] The shape of the polyester film with an easy-adhesion layer is not particularly limited. Examples of the shape of the polyester film with an easy-adhesion layer include polygons such as triangles, rectangles, and pentagons, circles, and random, indeterminate shapes. When the polyester film with an easy-adhesion layer is rectangular, the aspect ratio is not particularly limited as long as it does not cause any problems as a display screen. The aspect ratio of the polyester film with an easy-adhesion layer may be horizontal:vertical = 1:1, 4:3, 16:10, 16:9, 2:1, 5:4, 11:8, etc.

[0236] <<<Film Article>>> According to the method for producing a polyester film with an easy-adhesion layer by a wet method using a coating liquid for an easy-adhesion layer, a long film article 15L including a large number of polyester films 15 with an easy-adhesion layer can be produced, as shown in Fig. 2. The width and length of the film article 15L are not particularly limited. The width of the film article 15L may be 500 mm or more and 8000 mm or less, and the length may be 100 m or more and 10000 m or less.

[0237] Individual polyester films 15 with an easy-adhesion layer may be obtained by cutting the long film article 15L to a predetermined size. The film article 15L may be cut into sheets according to the size of an image display device or the like. According to this example, film articles 15 with various dimensions can be obtained from the long film article 15L according to needs. Therefore, polyester films 15 with an easy-adhesion layer with various dimensions can be provided in a timely manner. When cutting, ends of the film article 15L whose physical properties are unstable may be excluded.

[0238] 2, the film article 15L may be handled as a film roll 15R wound around a winding core 16 about a winding axis RA. The film roll 15R improves the ease of handling of the film article 15L.

[0239] <<<Optical Laminate>>> The optical laminate according to this embodiment has one or more functional layers on the easy-adhesion layer of the easy-adhesion layer-attached polyester film according to this embodiment described above.

[0240] Fig. 3 is a longitudinal cross-sectional view showing an example of an optical laminate. As shown in Fig. 3, the optical laminate 10 includes a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b may be a pair of main surfaces of the optical laminate 10. The optical laminate 10 includes, in order from the first surface 10a to the second surface 10b, a functional layer 30 and a polyester film 15 with an easy-adhesion layer. The optical laminate 10 includes, in order from the first surface 10a to the second surface 10b, the functional layer 30, an easy-adhesion layer 25, and a polyester film 20.

[0241] In the example shown in Fig. 3, the first surface 10a is formed of a functional layer 30. In the example shown in Fig. 3, the second surface 10b is formed of a polyester film 20. In the example shown in Fig. 3, the second surface 10b of the optical laminate 10 is also the second surface 15b of the polyester film 15 with an easy-adhesion layer.

[0242] The optical laminate 10 is not limited to the illustrated example. The optical laminate 10 may include two or more functional layers.

[0243] <<Functional Layer>> The functional layer may have a single-layer structure or a multi-layer structure. Examples of layers constituting the functional layer include a hard coat layer, an antiglare layer, an antireflection layer, a selective wavelength absorption layer, an antifouling layer, and an antistatic layer. A single functional layer may have multiple functions.

[0244] Among the functional layers, the antireflection layer may have a single-layer structure or a multi-layer structure. A single-layer antireflection layer may be a single layer of a low refractive index layer. A multi-layer antireflection layer may include two layers, a high refractive index layer and a low refractive index layer, or may include three or more layers.

[0245] Examples of functional layers formed on the easy-adhesion layer include the following F1 to F7: F1: Single-layer structure of a hard coat layer F2: Single-layer structure of an antiglare layer F3: Multilayer structure having a hard coat layer and an antireflection layer in this order F4: Multilayer structure having an antiglare layer and an antireflection layer in this order F5: Multilayer structure having a hard coat layer and an antifouling layer in this order F6: Multilayer structure having an antiglare layer and an antifouling layer in this order F7: Multilayer structure having a hard coat layer, an antireflection layer, and an antifouling layer in this order

[0246] Of the one or more functional layers, the functional layer in contact with the easy-adhesion layer may contain a cured product of an ionizing radiation curable resin composition. The functional layer in contact with the easy-adhesion layer may be a hard coat layer or an anti-glare layer. If the functional layer in contact with the easy-adhesion layer contains a cured product of an ionizing radiation curable resin composition, the adhesion of the optical laminate may be reduced. However, in the optical laminate according to this embodiment, since the average value of δq / δa on the surface of the easy-adhesion layer is within the above-mentioned numerical range, the adhesion of the optical laminate can be improved even if the functional layer in contact with the easy-adhesion layer contains a cured product of an ionizing radiation curable resin composition. Furthermore, since the functional layer in contact with the easy-adhesion layer contains a cured product of an ionizing radiation curable resin composition, the mechanical strength of the optical laminate can be increased.

[0247] Of the one or more functional layers, the functional layer in contact with the easy-adhesion layer may contain a cured product of an ionizing radiation-curable resin composition and may have a thickness of 0.5 μm or more. By having the functional layer in contact with the easy-adhesion layer have such a configuration, the mechanical strength of the optical laminate can be increased. The thickness of the functional layer in contact with the easy-adhesion layer may be 1.0 μm or more, or 2.0 μm or more. The upper limit of the thickness of the functional layer in contact with the easy-adhesion layer may be 20.0 μm or less, 10.0 μm or less, 7.0 μm or less, or 5.0 μm or less. The functional layer in contact with the easy-adhesion layer may be a hard coat layer or an antiglare layer.

[0248] The thickness of the functional layer in contact with the easy-adhesion layer may be 0.5 μm or more and 20.0 μm or less, 0.5 μm or more and 10.0 μm or less, 0.5 μm or more and 7.0 μm or less, or 0.5 μm or more and 5.0 μm or less. The thickness of the functional layer in contact with the easy-adhesion layer may be 1.0 μm or more and 20.0 μm or less, 1.0 μm or more and 10.0 μm or less, 1.0 μm or more and 7.0 μm or less, or 1.0 μm or more and 5.0 μm or less. The thickness of the functional layer in contact with the easy-adhesion layer may be 2.0 μm or more and 20.0 μm or less, 2.0 μm or more and 10.0 μm or less, 2.0 μm or more and 7.0 μm or less, or 2.0 μm or more and 5.0 μm or less.

[0249] The contact angle with pure water on the surface of the optical laminate closer to the functional layer than the polyester film with an easy-adhesion layer, for example, the first surface 10a in the example shown in FIG. 3, may be 80 degrees or more, 85 degrees or more, 90 degrees or more, 95 degrees or more, or 100 degrees or more. By setting the contact angle to 80 degrees or more, other members become more easily slippery when they come into contact with the surface of the optical laminate. This makes it less likely that stress will be generated in the optical laminate. This improves the adhesion of the optical laminate. In other words, by laminating a functional layer with an adjusted contact angle on the easy-adhesion layer of the polyester film with an easy-adhesion layer according to this embodiment, in which the average value of δq / δa is within a predetermined range, the adhesion of the optical laminate can be further improved.

[0250] If the functional layer located on the outermost surface contains a large amount of antifouling agent, the contact angle of pure water can be increased. However, if the contact angle of pure water is too large, the physical properties of the optical laminate, such as surface hardness, may be reduced. From this perspective, the contact angle may be 130 degrees or less, or 120 degrees or less. In this specification, the contact angle refers to the static contact angle measured by the θ / 2 method. General-purpose pure water can be used as the pure water. The resistivity of the pure water is 0.1 MΩ cm or more and 15 MΩ cm or less.

[0251] The contact angle on the surface of the optical laminate constituted by the functional layer may be 80 degrees or more and 130 degrees or less, 80 degrees or more and 120 degrees or less, 85 degrees or more and 130 degrees or less, 85 degrees or more and 120 degrees or less, 90 degrees or more and 130 degrees or less, 90 degrees or more and 120 degrees or less, 95 degrees or more and 130 degrees or less, 95 degrees or more and 120 degrees or less, 100 degrees or more and 130 degrees or less, or 100 degrees or more and 120 degrees or less.

[0252] The functional layer may contain, for example, a binder resin and, if necessary, an additive. The thickness of the functional layer may be appropriately selected depending on the function to be imparted.

[0253] The functional layer may contain a cured product of a curable resin composition as a binder resin. Examples of the cured product of the curable resin composition include a cured product of a thermosetting resin composition and a cured product of an ionizing radiation curable resin composition. When the functional layer contains a cured product of an ionizing radiation curable resin composition, the mechanical strength can be effectively improved.

[0254] The proportion of the cured product of the curable resin composition relative to the total binder resin in the functional layer may be 60% by mass or more, 80% by mass or more, 90% by mass or more, or even 100% by mass.

[0255] The thermosetting resin composition contains at least a thermosetting resin. It is a thermosetting resin composition that hardens when heated. Examples of the thermosetting resin include acrylic resin, urethane resin, phenolic resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. A curing agent may be added to the thermosetting resin composition as needed.

[0256] The ionizing radiation-curable resin composition contains a compound having an ionizing radiation-curable functional group. In this specification, a "compound having an ionizing radiation-curable functional group" is also referred to as an "ionizing radiation-curable compound." Ionizing radiation is an electromagnetic wave or charged particle beam that has an energy quantum capable of polymerizing or crosslinking molecules. The ionizing radiation may be ultraviolet light or an electron beam. The ionizing radiation may be an electromagnetic wave such as X-rays or gamma rays, or a charged particle beam such as alpha rays or ion beams.

[0257] Examples of the ionizing radiation-curable functional group include ethylenically unsaturated bond groups such as a (meth)acryloyl group, a vinyl group, and an allyl group, as well as an epoxy group, an oxetanyl group, etc. The ionizing radiation-curable compound may be a compound having an ethylenically unsaturated bond group, a compound having two or more ethylenically unsaturated bond groups, or a polyfunctional (meth)acrylate compound having two or more ethylenically unsaturated bond groups.

[0258] As the polyfunctional (meth)acrylate compound, either a monomer or an oligomer can be used. The functional layer may contain a cured product of a polyfunctional (meth)acrylate oligomer as a binder resin. In particular, the functional layer in contact with the easy-adhesion layer may contain a cured product of a polyfunctional (meth)acrylate oligomer as a binder resin. The cured product of the polyfunctional (meth)acrylate oligomer can improve the surface hardness of the optical laminate while suppressing excessive cure shrinkage of the functional layer. Therefore, the mechanical strength of the optical laminate can be increased while improving the adhesion of the optical laminate.

[0259] In order to achieve a better balance between the mechanical strength and adhesion of the optical laminate, the polyfunctional (meth)acrylate compound may contain an oligomer and a monomer. The functional layer may contain, as a binder resin, a cured product of a polyfunctional (meth)acrylate oligomer and a cured product of a polyfunctional (meth)acrylate monomer. In particular, the functional layer in contact with the easy-adhesion layer may contain, as a binder resin, a cured product of a polyfunctional (meth)acrylate oligomer and a cured product of a polyfunctional (meth)acrylate monomer.

[0260] When an oligomer and a monomer are used as the polyfunctional (meth)acrylate compound, the mass ratio of the oligomer to the monomer may be 5:95 to 95:5, 50:50 to 85:15, or 60:40 to 80:20.

[0261] Examples of polyfunctional (meth)acrylate oligomers include (meth)acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, etc. Urethane (meth)acrylate can be obtained, for example, by reacting a polyhydric alcohol and an organic diisocyanate with a hydroxy (meth)acrylate.

[0262] The weight average molecular weight of the polyfunctional (meth)acrylate oligomer may be 500 or more, or 1000 or more. The weight average molecular weight of the polyfunctional (meth)acrylate oligomer may be 5000 or less, or 3000 or less. By setting the weight average molecular weight of the oligomer to 500 or more, excessive cure shrinkage of the functional layer can be suppressed. By setting the weight average molecular weight of the oligomer to 5000 or less, a decrease in mechanical strength can be suppressed. The weight average molecular weight of the polyfunctional (meth)acrylate oligomer may be 500 or more and 5000 or less, 500 or more and 3000 or less, 1000 or more and 5000 or less, or 1000 or more and 3000 or less.

[0263] In this specification, the weight average molecular weight and number average molecular weight refer to values ​​calculated as polystyrene measured by gel permeation chromatography.

[0264] Among the polyfunctional (meth)acrylate compounds, examples of bifunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, and 1,6-hexanediol diacrylate. Examples of trifunctional or higher functional (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. The molecular skeleton of the above (meth)acrylate monomer may be partially modified. For example, (meth)acrylate monomers modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, or the like may be used.

[0265] For the purpose of adjusting the viscosity of the functional layer coating liquid, a monofunctional (meth)acrylate may be added as an ionizing radiation-curable compound. Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate. One of the above ionizing radiation-curable compounds may be used alone. Two or more of the above ionizing radiation-curable compounds may be used in combination. In addition to the ionizing radiation-curable compound, a polymer may be added to the functional layer coating liquid to adjust the viscosity. The weight-average molecular weight of the polymer may be more than 5,000 and not more than 200,000.

[0266] When the ionizing radiation-curable compound is an ultraviolet-curable compound, the ionizing radiation-curable resin composition may contain additives such as a photopolymerization initiator and a photopolymerization accelerator. Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl dimethyl ketal, benzoyl benzoate, α-acyloxime ester, anthraquinone, halogenoketone, thioxanthone, etc. As the photopolymerization initiator, an α-hydroxyalkylphenone that is resistant to yellowing may be used.

[0267] The photopolymerization accelerator can reduce polymerization inhibition caused by air during curing and increase the curing rate. Examples of the photopolymerization accelerator include one or more selected from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc.

[0268] The functional layer may contain additives as needed. The additives may be appropriately selected from general-purpose materials depending on the function to be imparted to the functional layer. For example, a functional layer to be imparted with antiglare properties may contain organic particles and / or inorganic particles as additives. A functional layer to be imparted with antireflection properties may contain a refractive index adjuster such as a high refractive index material or a low refractive index material as additives. A functional layer to be imparted with antifouling properties may contain an antifouling agent as additives. Further examples of additives include antistatic agents, leveling agents, ultraviolet absorbers, dyes, pigments, conductive particles, flocculants, antifoaming agents, antioxidants, and light stabilizers.

[0269] <<Physical Properties of Optical Laminate>> The total light transmittance of the optical laminate may be 50% or more, 80% or more, or 90% or more. The incident surface when measuring the total light transmittance of the optical laminate is the main surface that is closer to the polyester film with the easy-adhesion layer than the functional layer. As an example, in the example shown in Figure 3, the incident surface when measuring the total light transmittance is the second surface 10b. The method for measuring the total light transmittance is as described above.

[0270] The transmission haze of the optical laminate may be 0.3% or more, 0.4% or more, or 0.5% or more. The transmission haze of the optical laminate may be 10% or less, 7% or less, or 5% or less. When measuring the transmission haze of the optical laminate, the incident surface is the main surface closer to the polyester film with the easy-adhesion layer than the functional layer, for example, the second surface 10b in the example shown in Figure 3. The method for measuring the transmission haze is as described above.

[0271] <<Size, shape, etc. of optical laminate>> The optical laminate may be in the form of a sheet cut to a predetermined size. The size of the sheet is not particularly limited. The maximum diameter of the optical laminate as a sheet may be approximately 2 inches or more and 500 inches or less. The "maximum diameter" is the maximum length when connecting any two points on the optical laminate. For example, if the optical laminate is rectangular, the diagonal line of the rectangle is the maximum diameter. If the optical laminate is circular, the diameter of the circle is the maximum diameter.

[0272] The shape of the optical laminate is not particularly limited. Examples of the shape of the optical laminate include polygons such as triangles, rectangles, and pentagons, circles, and random, indeterminate shapes. When the optical laminate has a rectangular shape, the aspect ratio of the optical laminate is not particularly limited as long as it does not cause any problems as a display screen. The optical laminate may have a width:length ratio of 1:1, 4:3, 16:10, 16:9, 2:1, 5:4, 11:8, etc.

[0273] <<<Laminate Article>>> According to the method for producing an optical laminate by a wet method using a functional layer coating liquid, a long laminate article 10L including a large number of optical laminates 10 can be produced, as shown in Fig. 4. The width and length of the laminate article 10L are not particularly limited. The width of the laminate article 10L may be 500 mm or more and 8000 mm or less, and the length may be 100 m or more and 10000 m or less.

[0274] Individual optical laminates 10 may be obtained by cutting the long laminate article 10L to a predetermined size. The laminate article 10L may be cut into sheets according to the size of an image display device or the like. According to this example, optical laminates 10 having various dimensions can be obtained from the long laminate article 10L according to needs. Therefore, optical laminates 10 having various dimensions can be provided in a timely manner. When cutting, laminate articles 10L with unstable physical properties may be excluded.

[0275] As shown in Fig. 4, the laminate article 10L may be handled as a laminate roll 10R wound around a winding core 11 about a winding axis RA. The laminate roll 10R can improve the handleability of the laminate article 10L.

[0276] <<<Polarizing Plate>>> The polarizing plate according to this embodiment includes the optical element described above.

[0277] Fig. 5 shows an example of a polarizing plate. The polarizing plate 40 shown in Fig. 5 includes a polarizer 41, a first transparent protective plate 42 arranged on one side of the polarizer 41, and a second transparent protective plate 43 arranged on the other side of the polarizer 41. At least one of the first transparent protective plate 42 and the second transparent protective plate 43 may be the optical laminate 10 according to the present embodiment described above. A polyester film 15 with an easy-adhesion layer is located between the functional layer 30 and the polarizer 41.

[0278] In the illustrated example, only the first transparent protective plate 42 is the polyester film with an easy-adhesion layer 15. Both the first transparent protective plate 42 and the second transparent protective plate 43 may be polyester films 15 with easy-adhesion layers.

[0279] <Polarizer> The polarizer may be a sheet-type polarizer. The sheet-type polarizer may be a resin film dyed with iodine or the like and stretched. Examples of resin films include polyvinyl alcohol films, polyvinyl formal films, polyvinyl acetal films, and saponified ethylene-vinyl acetate copolymer films. Examples of polarizers include wire-grid polarizers made of a large number of metal wires arranged in parallel, coated polarizers coated with lyotropic liquid crystals or dichroic guest-host materials, and multilayer thin-film polarizers. The polarizer may be a reflective polarizer. A reflective polarizer can reflect polarized light components that are not transmitted.

[0280] <Transparent protective plate> A first transparent protective plate may be disposed on one side of the polarizer. A second transparent protective plate may be disposed on the other side of the polarizer. At least one of the first transparent protective plate and the second transparent protective plate is the optical laminate according to the present embodiment described above.

[0281] Examples of the first transparent protective plate and the second transparent protective plate include plastic films and glass. Examples of plastic films include polyester films, polycarbonate films, cycloolefin polymer films, and acrylic films, as well as films obtained by stretching one or more of these. Stretched films can improve mechanical strength. Examples of glass include alkali glass, nitride glass, soda-lime glass, borosilicate glass, and lead glass. The glass serving as the transparent protective plate protecting the polarizer may also serve as another member of the image display device. For example, the glass substrate of the liquid crystal display element may also serve as the transparent protective plate protecting the polarizer.

[0282] The polarizer and the transparent protective plate may be bonded together via an adhesive. The adhesive may be a general-purpose adhesive or a PVA-based adhesive.

[0283] In the polarizing plate according to the present embodiment, both the first transparent protective plate and the second transparent protective plate may be the optical laminate according to the present embodiment described above. In the polarizing plate according to the present embodiment, one of the first transparent protective plate and the second transparent protective plate may be the optical laminate according to the present embodiment described above. When the polarizing plate according to the present embodiment is used as a polarizing plate to be disposed on the light exit surface side of a display element, the transparent protective plate on the light exit surface side of the polarizer may be the optical laminate according to the present embodiment described above. On the other hand, when the polarizing plate according to the present embodiment is used as a polarizing plate to be disposed on the opposite side to the light exit surface of a display element, the transparent protective plate on the opposite side to the light exit surface of the polarizer may be the optical laminate according to the present embodiment described above.

[0284] <<<<Panel, Surface Plate>>>> The panel according to this embodiment includes a support plate and a polyester film optical laminate with an easy-adhesion layer. The surface plate according to this embodiment includes a support plate and an optical laminate on the support plate.

[0285] Fig. 6 shows an example of a panel 50 and a surface plate 55. As shown in Fig. 6, the panel 50 includes a support plate 51 and a polyester film with an easy-adhesion layer according to the present embodiment. The polyester film with an easy-adhesion layer 15 may be bonded to the support plate 51. A bonding layer such as an adhesive layer or a pressure-sensitive adhesive layer may be disposed between the polyester film with an easy-adhesion layer 15 and the support plate 51. In the panel, the polyester film may be bonded to the support plate. In the panel, the easy-adhesion layer may be bonded to the support plate.

[0286] The panel 50 may include a functional layer 30. In this example, the panel 50 may include an optical laminate 15 including a polyester film 20 with an easy-adhesion layer, and a support plate 51. The panel 50 may be exposed as a member constituting the surface. The panel 50 does not have to be a member that is used in an exposed state.

[0287] As shown in Fig. 6, the surface plate 55 includes a support plate 51 and the optical laminate 10 according to this embodiment. The surface plate 55 is used in an exposed state as a member constituting the surface. The optical laminate 10 may be bonded to the support plate 51. A polyester film 15 with an easy-adhesion layer is located between the functional layer 30 and the support plate 51.

[0288] The panel and face plate according to the present embodiment may be used, for example, as a face plate for an image display device. The panel and face plate according to the present embodiment may be used as a member for protecting an article such as a clock or a painting. The panel or face plate according to the present embodiment may be used as a member for a show window or a showcase. The support plate may be a resin plate. The support plate may be a glass plate.

[0289] The surface plate for an image display device may be arranged so that the surface closer to the optical laminate than the support plate is located closest to the viewer. That is, the surface of the surface plate closer to the optical laminate than the support plate may face away from the display element. The surface plate for protecting an article may be arranged so that the surface closer to the optical laminate than the support plate faces away from the article.

[0290] A lower limit may be set for the thickness of the support. By setting a lower limit for the thickness of the support plate, mechanical strength can be imparted to the panel and the surface plate. From this perspective, the thickness of the support plate may be 10 μm or more. An upper limit may be set for the thickness of the support plate. By setting an upper limit for the thickness of the support plate, the panel and the surface plate can be prevented from becoming large and heavy. The thickness of the panel and the surface plate may be 5000 μm or less. In order to meet the recent demand for thinner image display devices, the thickness of the panel and the surface plate may be 1000 μm or less, 500 μm or less, or 100 μm or less. The thickness of the support plate may be 10 μm or more and 5000 μm or less, 10 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, or 10 μm or more and 100 μm or less.

[0291] <<<Image Display Panel>>> The image display panel according to the present embodiment includes a display element and an optical laminate. Fig. 7 shows an example of an image display panel. In the image display panel 60 shown in Fig. 7, the optical laminate 10 according to the present embodiment is disposed on a display element 61. A polyester film 15 with an easy-adhesion layer may be located between the display element 61 and the functional layer 30.

[0292] The optical laminate may be disposed in the image display panel such that a surface of the optical laminate closer to the functional layer than the polyester film with an easy-adhesion layer faces away from the display element. The optical laminate may constitute the outermost surface of the image display panel. The functional layer of the optical laminate may constitute the outermost surface of the image display panel.

[0293] Examples of the display element include a liquid crystal display element, an EL display element such as an organic EL display element or an inorganic EL display element, a plasma display element, etc. Examples of the display element include an LED display element such as a mini LED display element or a micro LED display element. Examples of the display element include a laser hologram display element. These display elements may have a touch panel function inside the display element.

[0294] Examples of the liquid crystal display system of the liquid crystal display element include the IPS system, VA system, multi-domain system, OCB system, STN system, TSTN system, and ferroelectric liquid crystal system. The display element, which is a liquid crystal display element, may be illuminated from behind by a backlight. The liquid crystal display element may be located between the optical laminate and the backlight. Examples of the backlight include a backlight using quantum dots and a backlight using white light-emitting diodes.

[0295] The image display panel may be a foldable image display panel, a rollable image display panel, or an image display panel with a touch panel.

[0296] The size of the image display panel is not particularly limited. The maximum diameter of the image display panel may be about 2 inches or more and 500 inches or less. The maximum diameter means the maximum length when connecting any two points on the surface of the image display panel.

[0297] <<<Image Display Device>>> The image display device according to this embodiment includes the image display panel according to this embodiment described above.

[0298] Fig. 7 shows an example of an image display device. In an image display device 65 shown in Fig. 7, the optical laminate 10 is configured on the outermost surface. As shown in Fig. 7, when the display element 61 is a liquid crystal display element, the image display device 65 may include a backlight 62 that illuminates the image display panel 60 from behind. As shown in Fig. 7, the display element 61 may be located between the backlight 62 and the optical laminate 10.

[0299] Preferably, the image display device of the present disclosure further includes a drive control unit electrically connected to the image display panel, and a housing that houses the image display panel, the drive control unit, and the like.

[0300] The image display device may include an effective display area. The effective display area is an area in which an image can be displayed. For example, if the image display device has a housing that surrounds the display element, the area inside the housing may be the effective display area. The size of the image display device is not particularly limited, but the maximum diameter of the effective display area is approximately 2 inches to 500 inches. The maximum diameter of the effective display area refers to the maximum length when any two points within the effective display area are connected. For example, if the effective display area is rectangular, the diagonal of the rectangle is the maximum diameter. If the effective display area is circular, the diameter of the circle is the maximum diameter.

[0301] EXAMPLES The present disclosure will be specifically described below with reference to Examples, Comparative Examples, and Reference Examples, but the present disclosure is not limited to the Examples.

[0302] <<<Evaluation and Measurement>>> The polyester films with an easy-adhesion layer and optical laminates obtained in the Examples, Comparative Examples, and Reference Examples were subjected to the following measurements and evaluations. The results are shown in Tables 1 and 2. Unless otherwise specified, the atmosphere during each measurement and evaluation was a temperature of 23±2°C and a relative humidity of 50±5. Samples used for measurement and evaluation were defect-free, clean, and flat. Unless otherwise specified, the target samples were placed in the atmosphere for 16 hours before the start of each measurement and evaluation.

[0303] <<1-1. Planar orientation degree ΔP>> Samples of 7 mm x 7 mm were cut out from the polyester films with easy-adhesion layers of the Examples, Comparative Examples, and Reference Examples. The planar orientation degree ΔP of the polyester films with easy-adhesion layers was measured by the above-mentioned method using a retardation measurement device "RETS-100" from Otsuka Electronics Co., Ltd. The measurement results of the planar orientation degree ΔP are shown in the "ΔP" column of Tables 1 and 2. The in-plane retardation Re was measured by the above-mentioned measurement method using the retardation measurement device "RETS-100". The measurement results of the in-plane retardation Re are shown in the "Re" column of Tables 1 and 2.

[0304] The Nz coefficient was calculated from the thickness direction retardation Rth and in-plane retardation Re values ​​obtained by the above-mentioned measurement method using the retardation measurement device "RETS-100." It was confirmed whether the calculated Nz coefficient for each example was greater than 2.0 or less than 2.0. The confirmation results are shown in the "2.0<Nz" column of Tables 1 and 2. If the Nz coefficient was greater than 2.0, "Y" was entered in the "2.0<Nz" column. If the Nz coefficient was 2.0 or less, "N" was entered in the "2.0<Nz" column.

[0305] The retardation "nx-ny" was measured by the above-mentioned measurement method using the retardation measurement device "RETS-100." For the polyester films with the easy-adhesion layer of all Examples, the "nx-ny" was 0.0300 or less.

[0306] <<1-2. Average value of δq / δa and coefficient of variation of δq / δa>> Samples of 5 mm x 5 mm were cut out from the polyester films with easy-adhesion layers of the Examples, Comparative Examples, and Reference Examples. Measurements of δq / δa were carried out using the method described above, and the average value of δq / δa and the coefficient of variation of δq / δa were measured. The measurement results of the average value of δq / δa are shown in the "Average value" column of "δq / δa" in Tables 1 and 2. The measurement results of the coefficient of variation of δq / δa are shown in the "Coefficient of variation" column of "δq / δa" in Tables 1 and 2.

[0307] For a sample cut out to 5 mm x 5 mm, a 10 μm x 10 μm region on the surface of the easy-adhesion layer was measured using an atomic force microscope in phase mode. Details of the measurement device and measurement conditions were as follows. Seven measurement and evaluation regions of 2 μm x 2 μm were selected from within the 10 μm x 10 μm measurement region. The seven regions were selected from regions where the maximum amplitude height was 90 nm or less and the arithmetic mean amplitude height was 10 nm or less, as measured with an atomic force microscope. δa, δq, and δq / δa were calculated for the seven measurement and evaluation regions. The average value of δq / δa and the coefficient of variation of δq / δa were calculated based on the δa and δq of the five measurement and evaluation regions obtained by excluding the maximum and minimum values ​​from the δq / δa of the seven regions.

[0308] In the measurement device described below, when a 2 μm × 2 μm measurement evaluation area is selected on the screen, the δa and δq of the selected measurement evaluation area are automatically displayed. However, due to the settings of the measurement device described below, the item corresponding to δa is displayed as "Ra" and the item corresponding to δq is displayed as "Rq" on the display screen of the measurement device described below.

[0309] <Measurement device> Shimadzu Corporation product name "SPM-9600" <Analysis software> SPM Manager <AFM analysis conditions> Tilt correction: Line fit <Cantilever used> Nanoworld Co., Ltd. product number "NCHR" (resonance frequency: 320 kHz, spring constant 42 N / m) <Measurement mode> Phase (In the "phase mode" of the above measurement device, not only phase but also amplitude is measured.)

[0310] <Measurement conditions> - Amplitude / phase - Sensitivity: x2 - Phase offset: 95.00 deg - XY control - Scanning range: 10.0000 μm - Scanning speed: 1.00 Hz - Number of pixels: 512 x 512 - Offset X: 0.0000 μm - Offset Y: 0.0000 μm - Scanning angle: 0.0000 deg - Z control - Operating point: 0.228 V - P gain: 0.001 - I gain: 15000.000 - Offset Z: 0.0630 μm

[0311] <<1-3. Adhesion>> An adhesion test was carried out according to the following procedure to evaluate the adhesion of the optical laminates of the Examples, Comparative Examples, and Reference Example 1.

[0312] Eleven linear notches extending vertically and eleven linear notches extending horizontally were formed using a cutter blade on the surface (first surface 10a in FIG. 3) formed by the hard coat layer of the optical laminates of Examples, Comparative Examples, and Reference Example 1. The optical laminates were divided into 100 grid-like areas by the eleven vertical notches and the eleven horizontal notches. The horizontal spacing between the eleven vertical notches was 1 mm. The vertical spacing between the eleven horizontal notches was 1 mm. The cutter blade was NT Corporation product number "BA-52P."

[0313] Next, a peel test was performed by attaching an adhesive tape (Nichiban Co., Ltd., product name "Cellotape (registered trademark)") to the surface constituted by the hard coat layer of the optical laminate divided into a grid pattern, and then peeling off the adhesive tape. This peel test was performed in accordance with the cross-cut method specified in JIS K5600-5-6:1999. The adhesion of the optical laminates of Examples, Comparative Examples, and Reference Example 1 was evaluated according to the following evaluation criteria. The evaluation results of adhesion are shown in the "Adhesion" column of Table 1.

[0314] <Evaluation criteria> AA: No peeled masses were found, and no masses with partial chipping were found. A: No peeled masses were found, and the quality was judged to be good, but some masses had partial chipping along the notches. B: Peeled masses were found.

[0315] <<1-4. Puncture Resistance>> A puncture test was carried out according to the following procedure to evaluate the puncture resistance of the optical layered bodies of the Examples, Comparative Examples, and Reference Example 1.

[0316] Using the polyester films with easy-adhesion layers of the Examples, Comparative Examples, and Reference Example 1, samples for puncture tests were prepared as follows. The samples for puncture tests contained, in this order, a PET film, an optically clear adhesive film (OCA), chemically strengthened glass, a heat seal layer, a polyester film with easy-adhesion layers, and a hard coat layer. When preparing the samples, care was taken to avoid any abnormalities such as wrinkles or the inclusion of foreign matter.

[0317] First, A4 size samples were cut out from the polyester films with an easy-adhesion layer of Examples, Comparative Examples, and Reference Example 1. A coating solution for a hard coat layer having the following formulation was applied onto the easy-adhesion layer of the polyester film with an easy-adhesion layer to form a coating film. The coating film was dried at 80°C for 60 seconds, and then irradiated with ultraviolet light at 200 mJ / cm. ２ The polyester film was cured by irradiating it with light. As a result, a hard coat layer was formed on the easy-adhesion layer. The hard coat layer had a thickness of 10 μm. Thereafter, a first laminate including the polyester film with the easy-adhesion layer and the hard coat layer was obtained by cutting out a piece having a size of 10 mm × 30 mm.

[0318] <Coating liquid for hard coat layer> Polyfunctional acrylate monomer 30 parts by mass (Nippon Kayaku Co., Ltd., trade name: PET-30) Photopolymerization initiator 2 parts by mass (IGM Resins B.V., trade name: Omnirad 184) Toluene 30 parts by mass Methyl ethyl ketone 33 parts by mass

[0319] Next, the following heat-sealable resin composition was applied to the surface of the first laminate made of polyester film to form a coating film. This coating film was dried at 70°C for 1 minute to form a heat-seal layer. In this way, a second laminate including a heat-seal layer, a polyester film with an easy-adhesion layer, and a hard coat layer was obtained.

[0320] <Composition of heat-sealable resin composition> Amorphous polyester resin (Vylon 560, manufactured by Toyobo Co., Ltd.) 100 parts by mass Hexanemethylene diisocyanate (Coronate 2203, manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 parts by mass Silane coupling agent (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by mass Fluorine-based leveling agent (F568, manufactured by DIC Corporation) 0.2 parts by mass (solid equivalent) Solvent (MEK) 310 parts by mass Solvent (toluene) 310 parts by mass

[0321] Next, the second laminate and the chemically strengthened glass were bonded by heat sealing using the heat seal layer of the second laminate. A "Desktop Roll Laminator B35A3" manufactured by ACCO Brands Japan was used for heat sealing. The roll temperature during heat sealing was 140°C to 149°C. The feed speed during heat sealing was 0.3 m / min. This resulted in a third laminate comprising chemically strengthened glass, a heat seal layer, a polyester film with an easy-adhesion layer, and a hard coat layer.

[0322] The chemically strengthened glass is glass whose mechanical properties have been strengthened by a chemical method, and has a compressive stress layer on its surface. The thickness of the chemically strengthened glass was 70 μm. When applied to a display device, the polyester film with an easy-adhesion layer and the optical laminate are bonded to the chemically strengthened glass having a thickness of about 70 μm. For example, the chemically strengthened glass having a thickness of about 70 μm is used in a foldable display element.

[0323] A PET film was bonded to the surface of the chemically strengthened glass of the third laminate via an optically transparent adhesive film. The thickness of the optically transparent adhesive film was 50 μm. The optically transparent adhesive film was "8146-2" manufactured by 3M. The thickness of the PET film was 100 μm. The PET film was "A4160" manufactured by Toyobo Co., Ltd. The PET film "A4160" includes a PET layer and an easy-adhesion layer provided only on one side of the PET layer. The surface of the PET film "A4160" formed by the easy-adhesion layer was brought into contact with the optically transparent adhesive film. As a result, a sample for puncture test was obtained.

[0324] In the puncture test, a pen was dropped vertically onto the puncture test sample from above to check for cracks in the chemically strengthened glass.

[0325] During the puncture test, the puncture test sample was placed on a metal plate so that the surface composed of the PET layer of the PET film "A4160" was in contact with the metal plate. The metal plate was placed on a horizontal table. It was confirmed that the puncture test sample was spread as far horizontally as possible. The metal plate was a SUS304 plate. A pen was dropped from each test height onto the center of the hard coat layer of the puncture test sample. The pen was dropped vertically onto the puncture test sample with its tip facing downwards. The pen used was a Zebra Blen 0.5BAS88-BK pen (weight 12 g, tip 0.5 mmφ) manufactured by Zebra.

[0326] The maximum test height (cm) at which no cracks occurred in the chemically strengthened glass of the puncture test sample was measured as the puncture strength. The test height is the vertical length from the outermost surface formed by the hard coat layer of the puncture test sample to the pen tip. The larger the maximum test height (cm) as puncture strength, the higher the puncture strength. In the puncture test, the height (test height) dropped every 1 cm was increased. A ruler was fixed to the metal plate. The ruler extended vertically. The test height in each test was visually confirmed using this ruler.

[0327] Cracks in the chemically strengthened glass were confirmed by visually observing the chemically strengthened glass from various angles in a 1000 lux bright room. The pen was used continuously unless there was a visual change in the pen tip. If a change in the pen tip was confirmed by visual observation or if ink leakage occurred, the pen was replaced with a new one.

[0328] For each polyester film with an easy-adhesion layer of each example, 10 samples for a puncture test were prepared. For each polyester film with an easy-adhesion layer of each example, 10 samples for a puncture test were tested. The puncture resistance of the polyester films with an easy-adhesion layer of Examples, Comparative Examples, and Reference Example 1 was evaluated according to the following evaluation criteria. The evaluation results for puncture resistance are shown in the "Puncture resistance" column of Table 1.

[0329] <Evaluation criteria> AAA: The maximum test height at which no cracks occurred for 10 puncture test samples was 25 cm or more. AA: The maximum test height at which no cracks occurred for 8 or more puncture test samples was 25 cm or more. However, this did not fall under the category of AAA. A: The maximum test height at which no cracks occurred for 8 or more puncture test samples was 20 cm or more. However, this did not fall under either the category of AAA or the category of AA. B: This did not fall under any of the categories of AAA, AA, or A.

[0330] <<1-5. Bending Resistance>> A bending test was carried out according to the following procedure to evaluate the bending resistance of the optical laminates of Examples, Comparative Examples, and Reference Example 1.

[0331] Rectangular samples were cut out from the optical laminates of Examples, Comparative Examples, and Reference Example 1. The short side of the sample was 30 mm. The long side of the sample was 100 mm. The short side of the sample was parallel to the slow axis. The long side of the sample was parallel to the fast axis. As described above, the slow axis and fast axis can be identified using the retardation measurement device "RETS-100" manufactured by Otsuka Electronics Co., Ltd., which is used to measure the plane orientation degree ΔP. By identifying the slow axis and fast axis of the optical laminate of each example using the retardation measurement device "RETS-100," the short side and long side of the sample were aligned with the slow axis and fast axis, respectively.

[0332] A continuous bending test of 180 degrees was carried out 100,000 times using a durability tester "DLDMLH-FS" manufactured by Yuasa System Co., Ltd. The bending speed was 120 times per minute. The detailed method of the bending test is as follows.

[0333] 8A to 8C, both longitudinal end portions 91 of sample 90 were fixed to a pair of fixing portions 80 of a durability tester. The end portions 91 were 10 mm long from the short sides of sample 90, and were fixed to fixing portions 80 of the durability tester.

[0334] 8A to 8C, the pair of fixing portions 80 are relatively movable in the horizontal direction, and the pair of fixing portions 80 can move toward each other and move away from each other.

[0335] In the folding test, the pair of fixing portions 80 was repeatedly moved toward each other and away from each other. As shown in FIG. 8B , the fixing portions 80 were moved toward each other. This caused the sample 90 of the optical laminate to be deformed and folded. As shown in FIG. 8C , the fixing portions 80 were moved toward each other until the distance between both ends 91 of the sample 90 was 7 mm. In the folded state shown in FIG. 8C , the sample was bent along an arc with a diameter of 7 mm. In the folded state, the folded tip 92 of the sample 90 did not protrude from between the pair of fixing portions 80. Then, the pair of fixing portions 80 were moved away from each other, and the sample 90 was unfolded as shown in FIG. 8A . The folding and unfolding of the sample was repeated 100,000 times. The sample 90 was folded 120 times per minute.

[0336] For each example of the optical laminate, 10 samples for the bending test were prepared. For each example of the optical laminate, 10 samples for the bending test were tested. After the bending test, the samples were visually evaluated according to the following criteria. The evaluation results of the bending resistance are shown in the "Bending resistance" column of Table 1.

[0337] <Evaluation Criteria> AAA: None of the 10 bending test samples broke, and no defects such as delamination were found. Careful observation of the 10 bending test samples revealed no abnormalities such as cloudiness. AA: None of the 10 bending test samples broke, and no defects such as delamination were found. One or two bending test samples were of a quality deemed acceptable, but slight cloudiness was detected upon careful observation. However, these did not qualify for the AAA rating. A: None of the 10 bending test samples broke, and no defects such as delamination were found. Three or more bending test samples were of a quality deemed acceptable, but slight cloudiness was detected upon careful observation. However, these did not qualify for either the AAA or AA rating. B: None of the 10 bending test samples broke, but some of the bending test samples had defects such as delamination. However, this did not fall under any of the following: AAA, AA, or A. BB: One or more samples for the bending test broke before the number of bending tests reached 100,000. However, this did not fall under any of the following: AAA, AA, A, or B.

[0338] <<1-6. Pencil Hardness>> The pencil hardness of the polyester film was measured for the polyester films with an easy-adhesion layer of each of the Examples, Comparative Examples, and Reference Example 1. The pencil hardness was measured on the surface of the polyester film with an easy-adhesion layer that was constituted by the polyester film (second surface 15b in FIG. 1 ).

[0339] An evaluation sample was cut out from the polyester film with an easy-adhesion layer of each example. The evaluation sample was rectangular. The short side of the rectangular shape was 50 mm and the long side was 100 mm. The rectangular sample was spread out on a pencil hardness tester so as not to cause wrinkles or warping. The two short sides of the spread sample were fixed to the pencil hardness tester using mending tape over the entire length of the short sides. The mending tape was manufactured by 3M under the trade name "810-3-18". The pencil hardness tester used was a pencil scratch hardness tester SH-V1 manufactured by Toyo Seiki Seisakusho Co., Ltd. The pencil scratch hardness tester SH-V1 was an electric type.

[0340] The following conditions were used to measure the pencil hardness. Other conditions were in accordance with the conditions specified in JIS K5600-5-4:1999. Pencil movement speed: 1 mm / s Pencil movement distance: 7 mm Temperature: 23°C ± 2°C Relative humidity: 50 ± 5% Pencil angle: 45 degrees Pencil movement direction (pencil scratch direction): The pencil movement direction was parallel to the slow axis direction of the polyester film with an easy-adhesion layer. The slow axis of each sample was identified in the same manner as in the bending test.

[0341] For each example, a pencil hardness test was performed five times using a pencil of each hardness. If the film was not scratched three or more times out of five tests using a pencil of a given hardness, the given hardness was considered to have passed. For each example sample, the pencil hardness test was continued until it failed, and the highest hardness that was considered to have passed was considered to be the pencil hardness for that example. The pencil hardness measurement results are shown in the "Pencil" column of Table 1.

[0342] <<1-7. Transmission Haze>> Samples measuring 5 cm x 10 cm were cut out from the optical sheets according to Examples, Comparative Examples, and Reference Example 1. The transmission haze of the polyester film with an easy-adhesion layer of each example was measured using the method described above. The transmission haze was measured using a haze meter "HM-150" manufactured by Murakami Color Research Laboratory. The transmission haze of the polyester films with an easy-adhesion layer of all examples was 1.0% or less.

[0343] <<1-8. Total Light Transmittance>> Samples measuring 5 cm x 10 cm were cut out from the optical sheets according to Examples, Comparative Examples, and Reference Example 1. The total light transmittance of the polyester film with an easy-adhesion layer of each example was measured using the method described above. The total light transmittance was measured using a haze meter "HM-150" manufactured by Murakami Color Research Laboratory. The total light transmittance of the polyester films with an easy-adhesion layer of all examples was 90% or higher.

[0344] <<1-9. Transportability>> For Reference Examples A to E, film articles 15L (see FIG. 2) were prepared from polyester films with an easy-adhesion layer, each having a width of 680 mm and a length of 500 m. Film article 15L was wound around winding core 16 to obtain film rolls 15R. Ten film rolls 15R were prepared for each of Reference Examples A to E.

[0345] A laminate article 10L was produced from a film article 15L using a manufacturing apparatus 70 for an optical laminate 10 shown in Fig. 9. The manufacturing apparatus 70 included a supplying apparatus 71, an applying apparatus 72, a drying apparatus 73, a curing apparatus 74, and a collecting apparatus 75. The manufacturing apparatus 70 produced the laminate article 10L from the film article 15L in a roll-to-roll manner. For each of Reference Examples A to E, ten film rolls 15R were used to produce ten laminate rolls 10R.

[0346] The supply device 71 rotatably held the film roll 15R. The supply device 71 rotated the winding core 16 to unwind the film article 15L from the film roll 15R. The coating device 72 coated the next hard coat layer coating liquid onto the film article 15L. The drying device 73 dried the coating film of the hard coat layer coating liquid on the film article 15L. The curing device 74 irradiated the coating film of the hard coat layer coating liquid with ultraviolet light to cure it. The recovery device 75 wound the laminate article 10L onto the winding core 16 and recovered it.

[0347] <Coating liquid for hard coat layer> Polyfunctional acrylate monomer 30 parts by mass (Nippon Kayaku Co., Ltd., trade name: PET-30) Photopolymerization initiator 2 parts by mass (IGM Resins B.V., trade name: Omnirad 184) Toluene 30 parts by mass Methyl ethyl ketone 33 parts by mass

[0348] The manufacturing apparatus 70 further included one suction roll. The suction roll 76 suction-holds the film material 15L. Therefore, the film material 15L can be transported without nip rolls. As shown in FIG. 9 , the suction roll 76 was located between the curing device 74 and the recovery device 75.

[0349] The suction roll 76 had the following specifications: Wrap angle: 180° Suction width: 500 mm Mesh size: 500 μm Suction angle: 90° Outer diameter: φ600 mm

[0350] The tension of the film article 15L supplied from the supply device 71 was set to 200 N. The tension of the laminate article 10L recovered by the recovery device 75 was set to 250 N. The peripheral speed of the conveying roller was measured using a rotary encoder attached to the suction roll. The conveying speed was set to 20 m / min. Other manufacturing conditions, such as the drying conditions in the drying device 73 and the curing conditions in the curing device 74, were the same as the conditions employed in the manufacturing method of the optical laminate according to Example 1.

[0351] When ten laminate rolls 10R were produced for each example, the change in peripheral speed measured by a rotary encoder was confirmed. The conveyance property for each example was evaluated according to the following evaluation criteria. The evaluation results of the conveyance property are shown in the "Conveyance property" column of Table 2.

[0352] <Evaluation Criteria> AA: During the production of 10 laminate rolls 10R, the peripheral speed was maintained at 20±0.3 m / min over 100% of the total length (500 m x 10 rolls). A: During the production of 10 laminate rolls 10R, the peripheral speed was maintained at 20±0.3 m / min over 80% or more but less than 100% of the total length (500 m x 10 rolls). B: During the production of 10 laminate rolls 10R, the peripheral speed was maintained at 20±0.3 m / min over 70% or more but less than 80% of the total length (500 m x 10 rolls). BB: During the production of 10 laminate rolls 10R, the peripheral speed was maintained at 20±0.3 m / min over less than 70% of the total length (500 m x 10 rolls).

[0353] In all of Reference Examples A to E, the change in peripheral speed was not so great as to cause a problem in mass production.

[0354] For Reference Example A, in which the in-plane retardation Re was 1512 nm, and Reference Example E, in which the in-plane retardation Re was 2934 nm, the peripheral speed measured by a rotary encoder was repeatedly decelerated and accelerated every 5 seconds between 19.6 m / min and 20.5 m / min. For Reference Example A and Reference Example E, abnormal noise occurred during transport of the polyester film with the easy-adhesion layer. Furthermore, for Reference Example A and Reference Example E, when transport became unstable, poor appearance such as scratches occurred on the film article 15L or the laminate article 10L.

[0355] In Reference Examples B to D, no abnormal noise was generated and the peripheral speed was stable. No defects in appearance such as scratches were observed on the film article 15L and the laminate article 10L.

[0356] <<<2. Optical Laminates According to Examples and Comparative Examples to be Evaluated>>> Optical laminates according to Examples 1 to 8, Comparative Examples 1 to 7, Reference Example 1, and Reference Examples A to E were produced as described below. The optical laminates included a polyester film with an easy-adhesion layer and a functional layer formed on the polyester film with an easy-adhesion layer. The polyester film with an easy-adhesion layer included a polyester film and an easy-adhesion layer formed on the polyester film using a coating liquid for an easy-adhesion layer. In each example, the polyester film was one selected from a plurality of PET films. In each example, one selected from a plurality of coating liquids for an easy-adhesion layer was used.

[0357] <<2-1. Preparation of Coating Liquid for Adhesion Layer>> Coating liquids A to D for adhesion layer were prepared as described below.

[0358] <2-1-1. Coating Solution A for Adhesion Layer> The following materials were mixed and subjected to an ester exchange reaction at 200°C for 2 hours to obtain Compound 1. Dimethyl terephthalate 110 parts by mass Ethylene glycol 30 parts by mass 1,4-butanediol 30 parts by mass Zinc acetate 0.1 part by mass Antimony trioxide 0.1 part by mass

[0359] Next, 4.0 parts by mass of fumaric acid was added to Compound 1, and an esterification reaction was carried out at 230°C for 2 hours. Next, a polycondensation reaction was carried out at 250°C under reduced pressure (3 to 6 mmHg) for 1 hour to obtain Compound 2. To Compound 2, 230 parts by mass of methyl ethyl ketone and 120 parts by mass of isopropyl alcohol were added as a solvent. Compound 2 and the solvent were stirred while being heated to 70°C, and Compound 2 was dissolved in the solvent to obtain Resin Solution 3.

[0360] 30 parts by mass of m-xylene diisocyanate was added to Resin Solution 3 and stirred for 3 hours. Then, the temperature of the reaction vessel was raised to 100°C, and methyl ethyl ketone and isopropyl alcohol were removed, thereby obtaining Resin 4 for easy adhesion.

[0361] The adhesive resin 4 was dissolved in a mixed solvent of methyl ethyl ketone and toluene in a mass ratio of 8:2. This resulted in an adhesive layer coating solution A having a solids content of 5 mass%. The mass ratio of the polyester component to the polyurethane component of the resin contained in the adhesive layer coating solution A was 8:2.

[0362] <2-1-2. Coating Solution B for Easy-Adhesion Layer> Coating Solution B for Easy-Adhesion Layer was obtained in the same manner as Coating Solution A for Easy-Adhesion Layer, except that the blending amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in Compound 1, and the amount of m-xylene diisocyanate added to Resin Solution 3 were changed to the amounts shown below. The mass ratio of the polyester component to the polyurethane component of the resin contained in Coating Solution B for Easy-Adhesion Layer was 7:3. Dimethyl terephthalate 100 parts by mass Ethylene glycol 28 parts by mass 1,4-butanediol 28 parts by mass m-xylene diisocyanate 46 parts by mass

[0363] <2-1-3. Coating Solution C for Easy-Adhesion Layer> Coating Solution C for Easy-Adhesion Layer was obtained in the same manner as Coating Solution A for Easy-Adhesion Layer, except that the blending amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in Compound 1, and the amount of m-xylene diisocyanate added to Resin Solution 3 were changed to the amounts shown below. The mass ratio of the polyester component to the polyurethane component of the resin contained in Coating Solution C for Easy-Adhesion Layer was 6:4. Dimethyl terephthalate 70 parts by mass Ethylene glycol 25 parts by mass 1,4-butanediol 25 parts by mass m-xylene diisocyanate 60 parts by mass

[0364] <2-1-4. Coating Solution D for Easy-Adhesion Layer> Coating Solution C for Easy-Adhesion Layer was obtained in the same manner as Coating Solution A for Easy-Adhesion Layer, except that the blending amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in Compound 1, and the amount of m-xylene diisocyanate added to Resin Solution 3 were changed to the amounts shown below. The mass ratio of the polyester component to the polyurethane component of the resin contained in Coating Solution C for Easy-Adhesion Layer was 4:6. Dimethyl terephthalate 30 parts by mass Ethylene glycol 23 parts by mass 1,4-butanediol 23 parts by mass m-xylene diisocyanate 89 parts by mass

[0365] 2-1-5. Coating Solution E for Adhesion Layer 15 g of polyvinyl alcohol was added little by little to 85 g of ion-exchanged water while stirring, and the mixture was heated to 70 to 90°C and stirred to prepare a PVA-A aqueous solution with a solids concentration of 15% by mass. The polyvinyl alcohol used was "PVA28-98" (formerly known as "PVA117") manufactured by Kuraray Co., Ltd.

[0366] A mixture of a PVA-A aqueous solution and a water-based polyurethane resin at a solids ratio of 60:40 was diluted with a solvent to obtain coating solution E for an easy-adhesion layer. The solids concentration of coating solution E for an easy-adhesion layer was 14.6% by mass. "Vylonal MD2000" manufactured by Toyobo MC Co., Ltd. was used as the water-based polyurethane resin. The solvent was a mixture of water and isopropanol at a mass ratio of 7:3.

[0367] <2-1-6. Coating Solution F for Easy-Adhesion Layer> A mixture of 33 parts by mass of polyester resin and 1 part by mass of crosslinking agent was diluted with a solvent to obtain Coating Solution F for Easy-Adhesion Layer. The solids concentration of Coating Solution F for Easy-Adhesion Layer was 10% by mass. The polyester resin used was "Vylon UR-1400" manufactured by Toyobo Co., Ltd. The crosslinking agent used was "Takenate D110N" manufactured by Mitsui Chemicals, Inc. The solvent was a mixture of methyl ethyl ketone and toluene in a mass ratio of 8:2.

[0368] <2-1-7. Coating Solution G for Easy-Adhesion Layer> A polyester-based water-dispersible urethane adhesive was diluted with a solvent to obtain Coating Solution G for Easy-Adhesion Layer. The solid content concentration of Coating Solution G for Easy-Adhesion Layer was 14.6% by mass. As the polyester-based water-dispersible urethane adhesive, "Superflex SF210" (solid content concentration 35%) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. was used. The solvent was a mixture of water and isopropanol in a mass ratio of 7:3.

[0369] <<2-2. Production and Preparation of PET Films>> The following PET films 1 to 6 were prepared as polyester films for the Examples, Comparative Examples, and Reference Examples.

[0370] <2-2-1. PET Film 1> 1 kg of PET (absorption center wavelength: 320 nm) and 0.1 kg of an ultraviolet absorber were melt-mixed in a kneader at 280°C to produce pellets containing the ultraviolet absorber. The ultraviolet absorber was 2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one). The pellets and PET with a melting point of 258°C were placed in a single-screw extruder, melt-kneaded at 290°C, and extruded through a T-die. The extruded PET was cast onto a casting drum with a controlled surface temperature to obtain a cast film. The amount of ultraviolet absorber in the cast film was 3 parts by mass per 100 parts by mass of PET.

[0371] The surface temperature of the casting drum was controlled as follows: the part where the resin extruded from the T-die adhered was set to 50°C, and the part where the resin peeled off was set to 25°C. The temperature was gradually reduced from the part where the resin adhered to the part where the resin peeled off.

[0372] The obtained casting film was heated with a group of rolls set at 120°C, and then stretched 5.1 times in the machine direction in the stretching section, followed by cooling. The machine direction length of the stretching section was 480 mm. Stretching roll A was located at the start point of the stretching section, and stretching roll B was located at the end point. Stretching roll A and stretching roll B each had two nip rolls. The casting film was stretched while being heated from both the front and back sides of the film with radiation heaters so that the film temperature at a point 180 mm from the start point of the 480 mm stretching section was 135°C. The time the casting film passed through the stretching section in the machine direction was 0.50 seconds.

[0373] The uniaxially stretched film was then introduced into a tenter. The uniaxially stretched film was preheated with a group of rolls set at 120°C, and then stretched 4.9 times in the width direction while being heat-treated with hot air at 105°C in the first stage and hot air at 136°C in the second stage. Here, when the width direction stretching section was divided into two, the film was stretched in two stages so that the stretch amount of the film at the midpoint of the width direction stretching section was 80% of the stretch amount at the end of the width direction stretching section. The stretch amount was calculated by subtracting the film width before stretching from the film width at the measurement point. The film stretched in the width direction was then heat-treated in the tenter in stages with hot air at heat treatment temperatures ranging from 180°C to 245°C. Subsequently, the width direction stretched film was subjected to a 1% relaxation treatment in the width direction under the same temperature conditions, and then rapidly cooled to 100°C and then subjected to a 1% relaxation treatment in the width direction. The relaxed PET film was wound up to obtain a biaxially stretched PET film 1 having a thickness of 40 μm.

[0374] <2-2-2. PET Film 2> Biaxially stretched PET film 2 was obtained in the same manner as PET film 1, except that the time during which the casting film passed through the stretching section in the machine direction was changed to 0.45 seconds.

[0375] <2-2-3. PET Film 3> Biaxially stretched PET film 2 was obtained in the same manner as PET film 1, except that the time during which the casting film passed through the stretching section in the machine direction was changed to 0.40 seconds.

[0376] <2-2-4. PET Film 4> Biaxially stretched PET film 4 was obtained in the same manner as PET film 1, except that the time during which the casting film passed through the stretching section in the machine direction was changed to 0.35 seconds.

[0377] <2-2-5. PET Film 5> Biaxially stretched PET film 4 was obtained in the same manner as PET film 1, except that the time during which the casting film passed through the stretching section in the machine direction was changed to 0.30 seconds.

[0378] <2-2-6. PET Film 6> Biaxially stretched PET film 6 was obtained in the same manner as PET film 1, except that the time during which the casting film passed through the stretching section in the machine direction was changed to 0.25 seconds.

[0379] 2-2-7. PET Film 7 A PET film with an easy-adhesion layer, "Cosmoshine A4160," available from Toyobo Co., Ltd., was prepared as PET film 7. This polyester film with an easy-adhesion layer included a biaxially stretched PET film and an easy-adhesion layer provided on one side of the biaxially stretched PET film. The thickness of the polyester film with an easy-adhesion layer used as PET film 7 was 38 μm.

[0380] 2-2-8. PET Film 8 PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.8 times and the stretching ratio in the width direction was changed to 4.4 times.

[0381] <2-2-9. PET Film 9> Biaxially stretched PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.5 times and the stretching ratio in the width direction was changed to 4.4 times.

[0382] <2-2-10. PET film 10> Biaxially stretched PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.5 times and the stretching ratio in the width direction was changed to 4.7 times.

[0383] <2-2-11. PET film 11> Biaxially stretched PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.3 times and the stretching ratio in the width direction was changed to 4.7 times.

[0384] <2-2-12. PET film 12> Biaxially stretched PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.3 times and the stretching ratio in the width direction was changed to 5.0 times.

[0385] <2-2-13. PET film 13> Biaxially stretched PET film 8 was obtained in the same manner as PET film 1, except that the stretching ratio in the machine direction was changed to 3.3 times and the stretching ratio in the width direction was changed to 5.1 times.

[0386] <<2-3. Preparation of polyester film with easy-adhesion layer, and optical laminate>> Polyester films with easy-adhesion layer and optical laminates according to Examples 1 to 8, Comparative Examples 1 to 4, Reference Example 1, and Reference Examples A to E were prepared using the above-described coating liquid for the easy-adhesion layer and PET film.

[0387] [Example 1] The above-mentioned coating solution A for an easy-adhesion layer was applied to a PET film 2 to form a coating film. The coating film was dried at 90°C for 60 seconds. As a result, an easy-adhesion layer having a thickness of 100 nm was formed, and a polyester film with an easy-adhesion layer of Example 1 was obtained.

[0388] A coating solution for a hard coat layer having the following formulation was applied onto the adhesive layer of the polyester film with the adhesive layer to form a coating film. The coating film was dried at 80° C. for 60 seconds and then irradiated with ultraviolet light at 200 mJ / cm ２ As a result, a hard coat layer having a dry thickness of 10 μm was formed on the easy-adhesion layer, and an optical layered body of Example 1 was obtained.

[0389] <Coating liquid for hard coat layer> Polyfunctional acrylate monomer 30 parts by mass (Nippon Kayaku Co., Ltd., trade name: PET-30) Photopolymerization initiator 2 parts by mass (IGM Resins B.V., trade name: Omnirad 184) Toluene 30 parts by mass Methyl ethyl ketone 33 parts by mass

[0390] Example 2 A polyester film with an easy-adhesion layer and an optical laminate of Example 2 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3.

[0391] Example 3 A polyester film with an easy-adhesion layer and an optical laminate of Example 3 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 4.

[0392] Example 4 A polyester film with an easy-adhesion layer and an optical laminate of Example 4 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 5.

[0393] [Example 5] A polyester film with an easy-adhesion layer and an optical laminate of Example 5 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3 and that coating liquid A for the easy-adhesion layer was changed to coating liquid B for the easy-adhesion layer.

[0394] [Example 6] The polyester film with an easy-adhesion layer and the optical laminate of Example 6 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3 and that coating liquid A for the easy-adhesion layer was changed to coating liquid C for the easy-adhesion layer.

[0395] [Example 7] The polyester film with an easy-adhesion layer and the optical laminate of Example 7 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 5, that coating liquid A for the easy-adhesion layer was changed to coating liquid B for the easy-adhesion layer, and that the drying conditions for drying the coating film of the coating liquid for the easy-adhesion layer were changed from 90°C for 60 seconds to 100°C for 60 seconds.

[0396] [Example 8] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 8 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3, that coating liquid A for the easy-adhesion layer was changed to coating liquid B for the easy-adhesion layer, and that the drying conditions for drying the coating film of the coating liquid for the easy-adhesion layer were changed from 90°C for 60 seconds to 110°C for 60 seconds.

[0397] Comparative Example 1 A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 1 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 1.

[0398] Comparative Example 2 A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 2 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 6.

[0399] [Comparative Example 3] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 3 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3 and that coating liquid A for easy-adhesion layer was changed to coating liquid D for easy-adhesion layer.

[0400] [Comparative Example 4] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 4 were obtained in the same manner as in Example 1, except that the PET film 2 and the easy-adhesion layer were changed to a commercially available PET film 7 (a polyester film with an easy-adhesion layer).

[0401] [Comparative Example 5] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 5 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3, Coating Liquid A for the easy-adhesion layer was changed to Coating Liquid E for the easy-adhesion layer, the application timing of Coating Liquid E for the easy-adhesion layer was changed, the application amount of Coating Liquid E for the easy-adhesion layer was changed, and the drying conditions for the coating film of Coating Liquid E for the easy-adhesion layer were changed. In Comparative Example 5, Coating Liquid E for the easy-adhesion layer was applied onto the uniaxially stretched film before stretching in the width direction. The uniaxially stretched film was stretched in the width direction together with the coating film of Coating Liquid E for the easy-adhesion layer. The coating amount of Coating Liquid E for the easy-adhesion layer was 0.2 g / m in terms of the mass of the easy-adhesion layer after drying. ２ The coating film was dried at 80° C. for 20 seconds.

[0402] [Comparative Example 6] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 6 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 3, that Coating Solution A for easy-adhesion layer was changed to Coating Solution F for easy-adhesion layer, that the drying conditions for the coating film of Coating Solution F for easy-adhesion layer were changed, and that the coating amount of Coating Solution F for easy-adhesion layer was changed. The drying conditions for the coating film were 70°C and 30 seconds. The coating amount of Coating Solution F for adhesive layer was 5 g / m in wet mass. ２ The mass of the easy-adhesion layer after drying was 0.5 g / m ２ It was decided.

[0403] [Comparative Example 7] A polyester film with an easy-adhesion layer and an optical laminate of Comparative Example 7 were obtained in the same manner as in Example 1, except that PET Film 2 was changed to PET Film 3, Coating Solution A for the easy-adhesion layer was changed to Coating Solution G for the easy-adhesion layer, the coating method for the coating film of Coating Solution G for the easy-adhesion layer was changed, the drying conditions for the coating film of Coating Solution G for the easy-adhesion layer were changed, and the coating amount of Coating Solution G for the easy-adhesion layer was changed. Coating Solution G for the easy-adhesion layer was applied using a coating tester with a gravure roll of mesh #200. The drying conditions for the coating film were 150°C and 1 minute. The coating amount of Coating Solution F for the adhesive layer was an amount sufficient to obtain an easy-adhesion layer with a thickness of 0.3 μm.

[0404] Reference Example 1 A polyester film with an easy-adhesion layer and an optical laminate of Reference Example 1 were obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 8.

[0405] Reference Example A A polyester film with an easy-adhesion layer of Reference Example A was obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 9.

[0406] Reference Example B A polyester film with an easy-adhesion layer of Reference Example B was obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 10.

[0407] Reference Example C A polyester film with an easy-adhesion layer of Reference Example C was obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 11.

[0408] Reference Example D A polyester film with an easy-adhesion layer of Reference Example D was obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 12.

[0409] Reference Example E A polyester film with an easy-adhesion layer of Reference Example E was obtained in the same manner as in Example 1, except that PET film 2 was changed to PET film 13.

[0410]

[0411]

[0412] By setting the average value of δq / δa to 1.125 or more and 1.80 or less according to feature (B), high adhesion could be imparted to the polyester film with an easy-adhesion layer and the optical laminate. By setting the planar orientation degree ΔP to the above-mentioned 0.150 or more and 0.195 or less according to feature (A), mechanical strength could be improved.

[0413] The planar orientation degree ΔP and stab resistance were correlated. However, the correlation between the planar orientation degree ΔP and stab resistance was not very strong, and was weaker than the correlation between the planar orientation degree ΔP and bending resistance. This can be understood from the fact that the stab resistance of Comparative Example 3, in which the planar orientation degree ΔP was 0.176, was lower than that of other examples having similar planar orientation degrees ΔP. ​​On the other hand, among samples in which the average value of δq / δa was 1.125 or more and 1.80 or less, the planar orientation degree ΔP and stab resistance exhibited a very strong correlation. From this point of view, it can be said that a heterogeneous effect can be obtained by combining the above-mentioned feature (A) regarding the planar orientation degree ΔP with the above-mentioned feature (B) regarding the average value of δq / δa.

[0414] More specifically, Comparative Example 3 has the same planar orientation degree ΔP as Examples 2, 5, and 6, and has a larger average value of δq / δa than Examples 2, 5, and 6. The evaluations of puncture resistance and bending resistance for Comparative Example 3 were poor, unlike Examples 2, 5, and 6. That is, by setting an upper limit on the average value of δq / δa in accordance with Feature (B) in addition to Feature (A), puncture resistance and bending resistance could be more stably improved.

[0415] One cause of this phenomenon is presumed to be that by setting an upper limit to the average value of δq / δa, the mechanical properties of the polyester film with an easy-adhesion layer become uniform, and the bending resistance, which is an evaluation index of more local mechanical strength, and the puncture resistance, which can be said to be an evaluation index of more local mechanical strength than the bending resistance, can be stably improved. However, the present disclosure is not bound by this presumption.

[0416] Similarly, Comparative Examples 5 to 7 have the same planar orientation degree ΔP as Example 2, but have smaller average values ​​of δq / δa than Example 2. The evaluations of the bending resistance and puncture resistance for Comparative Examples 5 to 7 were satisfactory, but lower than the evaluation for Example 2. That is, by setting a lower limit for the average value of δq / δa in accordance with Feature (B) in addition to Feature (A), the bending resistance and puncture resistance could be improved more stably.

[0417] It is presumed that one reason why the bending resistance can be stably improved is that by setting a lower limit for the average value of δq / δa, the mechanical properties of the polyester film with an easy-adhesion layer become too uniform, which can prevent repeated application of a load to a certain area.It is presumed that one reason why the puncture resistance can be stably improved is that by setting a lower limit for the average value of δq / δa, the mechanical properties of the polyester film with an easy-adhesion layer become too uniform, which can prevent concentrated application of an impact load to a very small position.However, the present disclosure is not bound by this presumption.

[0418] Note that in Examples 2, 5, 6, and Comparative Example 3, the ratio of the polyester component in the easy-adhesion layer decreased in that order. In Examples 2, 5, 6, and Comparative Example 3, the average value of δq / δa decreased in that order, and Comparative Example 3 showed insufficient adhesion. The ratio of the polyester component in the easy-adhesion layer of Comparative Example 6 was greater than the ratio of the polyester component in the easy-adhesion layer of Example 2. The average value of δq / δa in Comparative Example 6 was smaller than the average value of δq / δa in Example 2. However, the adhesion of Comparative Example 6 was evaluated as "B." This phenomenon is thought to be due to the fact that the viscoelasticity of the surface of the easy-adhesion layer in Comparative Example 6 was too homogeneous, resulting in reduced adhesion between the easy-adhesion layer and the functional layer. In other words, in Comparative Example 6, the adhesion between the easy-adhesion layer and the polyester film was improved, but the adhesion between the easy-adhesion layer and the functional layer was reduced. In Comparative Examples 5 and 7, as in Comparative Example 6, the average value of δq / δa was less than 1.125, and the adhesion evaluation was insufficient.

[0419] In addition to the features (A) and (B), the above-mentioned feature (B1) regarding the coefficient of variation of δq / δa enabled the adhesion of the polyester film with an easy-adhesion layer and the optical laminate to be more stably improved. This point can be understood from the evaluation results of the adhesion in Examples 5 and 8.

[0420] In Reference Example 1, in which the Nz coefficient was 2.0 or less, results were obtained that were judged to be good in all of adhesion, piercing resistance, bending resistance, and pencil hardness. However, when producing the polyester film with an easy-adhesion layer of Reference Example 1, the wettability of the coating liquid for the easy-adhesion layer on the PET film was reduced compared to other examples. Compared to other examples, the coefficient of variation of δq / δa was larger. Compared to Example 3, in which the planar orientation degree ΔP was similar, adhesion, piercing resistance, and bending resistance were all inferior.

[0421] 10: optical laminate, 10a: first surface, 10b: second surface, 10L: laminate article, 10R: laminate roll, 11: winding core, 15: polyester film with easy-adhesion layer, 15a: first surface, 15b: second surface, 15L: film article, 15R: film roll, 16: winding core, 20: polyester film, 25: easy-adhesion layer, 30: functional layer, 40: polarizing plate, 41: polarizer, 42: first transparent protective plate, 43: second transparent protective plate, 50: panel, 51: support, 55: surface plate, 60: image display panel, 61: display element, 65: image display device

Claims

1. A polyester film with an easy-adhesion layer, comprising a polyester film and an easy-adhesion layer, the degree of planar orientation being 0.150 to 0.195, and the average value of δq / δa on the surface of the easy-adhesion layer being 1.125 to 1.

80. <Calculation of the average value of δq / δa> A 10 μm×10 μm area on the surface of the easy-adhesion layer is measured in phase mode with an atomic force microscope. The phase signal distribution on the surface of the easy-adhesion layer is obtained by the above measurement. The unit of the phase signal is [deg]. The arithmetic mean value of the phase signal shown in the following formula 1 is defined as δa. The root mean square value of the phase signal shown in the following formula 2 is defined as δq. In the following formulas 1 and 2, the orthogonal coordinate axes X and Y are placed on a reference surface showing the average value of the phase signal, the axis perpendicular to the reference surface is the Z axis, and the curved surface of the phase signal is f(x, y). In the following formulas 1 and 2, the size of the area in which δa and δq are calculated is Lx and Ly. In the following formulas 1 and 2, Ar = Lx x Ly. Seven measurement evaluation areas of 2 μm x 2 μm are selected from within the measurement area of ​​10 μm x 10 μm. δa, δq, and δq / δa are calculated for each of the seven measurement evaluation areas. The maximum and minimum values ​​of the δq / δa at the seven points are excluded, and based on the δq / δa at five points, the average value of δq / δa is calculated.

2. The polyester film with an easy-adhesion layer according to claim 1, wherein the coefficient of variation of δq / δa calculated based on δq / δa at the five points is 0.150 or less.

3. The polyester film with an easy-adhesion layer according to claim 1, wherein nx and ny satisfy the following relationship when the refractive index in the in-plane slow axis direction is defined as nx and the refractive index in the in-plane direction perpendicular to the slow axis is defined as ny: nx-ny≦0.0300.

4. The polyester film with an easy-adhesion layer according to claim 1, having a thickness of 10 μm or more and 75 μm or less.

5. The polyester film with an easy-adhesion layer according to claim 1, having an in-plane retardation of 2000 nm or less.

6. A film article comprising a plurality of the polyester films with an easy-adhesion layer according to any one of claims 1 to 5.

7. The film article of claim 6, wound about a winding axis.

8. An optical laminate having one or more functional layers on the easy-adhesion layer of the polyester film according to any one of claims 1 to 5.

9. The optical laminate according to claim 8, wherein, of the one or more functional layers, the functional layer in contact with the adhesion layer contains a cured product of an ionizing radiation curable resin composition.

10. The optical laminate according to claim 8, wherein the surface of the optical laminate having the functional layer has a contact angle with pure water of 80 degrees or more.

11. A laminate article comprising a plurality of the optical laminates according to claim 8.

12. The laminate article of claim 11, wound about a winding axis.

13. A polarizing plate comprising, in this order, a first transparent protective plate, a polarizer, and a second transparent protective plate, wherein at least one of the first transparent protective plate and the second transparent protective plate is the optical laminate described in claim 8, and the polyester film with an easy-adhesion layer is positioned between the functional layer and the polarizer.

14. A panel comprising a support plate and the polyester film with an easy-adhesion layer according to any one of claims 1 to 5.

15. A surface plate comprising a support plate and the optical laminate according to claim 8, wherein the polyester film with an easy-adhesion layer is positioned between the functional layer and the support plate.

16. An image display panel comprising a display element and the optical laminate according to claim 8.

17. An image display device comprising the image display panel according to claim 16.

Images