Polyester film with easily adhesive layer, film article, optical laminate, laminate article, polarizing plate, panel, surface plate, image display panel, and image display device

Abstract

The polyester film with an easily adhesive layer comprises a polyester film and an easily adhesive layer on the polyester film. The degree of plane orientation is 0.150 or more and 0.195 or less. The average value of [delta] q / [delta] a on the surface of the easily adhesive layer is 1.80 or less. And delta a is the arithmetic mean value of the phase signals on the surface of the easily-adhesive layer. And delta q is the root-mean-square of the phase signal on the surface of the easy-to-adhere layer.

Description

Technical Field

[0001] This invention relates to polyester films with easy-to-adhere layers, film articles, optical laminates, laminated articles, polarizers, panels, surface plates, and image display devices. Background Technology

[0002] In image display devices such as liquid crystal displays, organic EL displays, micro LED displays, small LED displays, quantum dot displays, and laser holographic displays, various optical laminates are incorporated to improve image visibility and suppress damage to the device surface. Furthermore, optical laminates can also be incorporated into shop windows and painting covers to improve the visibility of items and protect them.

[0003] Optical laminates comprise a plastic film and functional layers overlapping the plastic film. Most optical laminates include an easy-adhesion layer located on the plastic film. The easy-adhesion layer improves the adhesion between the plastic film and the functional layers in the optical laminate. The plastic film is operated as a film with an easy-adhesion layer laminated on top of it.

[0004] As a plastic film used in optical laminates, triacetylcellulose (TAC) films with low optical anisotropy are preferred. However, TAC films have problems with mechanical strength. These problems become more pronounced in TAC films used in large-screen image display devices. In this specification, "triacetylcellulose film" will also be referred to as "TAC film".

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

[0006] Image display devices such as liquid crystal displays (LCDs) and organic EL displays output polarized light. When a PET film is used in such an image display device, a rainbow-like interference pattern, known as an iridescent spot, is generated. This iridescent interference pattern is caused by the in-plane phase difference of the PET film. The iridescent interference pattern reduces visibility. As a countermeasure against the iridescent spot, a method has been proposed to maximize the in-plane phase difference of the PET film (e.g., Patent Document 1).

[0007] The PET film with a large in-plane phase difference, as described in Patent Document 1, is obtained by unidirectionally stretching the PET film. However, unidirectionally stretched films have problems such as being prone to breakage in the stretching direction.

[0008] As a countermeasure against iris spots, contrary to Patent Document 1, a means of reducing the in-plane phase difference of the PET film was considered.

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-107198

[0010] Patent Document 2: Japanese Patent Application Publication No. 2012-32819

[0011] Patent Document 3: Japanese Patent Application Publication No. 2016-6530

[0012] Patent Document 4: International Publication No. 2021 / 200884

[0013] PET films with small in-plane phase differences can be obtained, for example, by reducing the stretch ratio. However, reducing the stretch ratio reduces the mechanical strength of the PET film.

[0014] Compared to conventional biaxially oriented PET films, the PET films described in Patent Documents 2 and 3 reduce in-plane phase difference without reducing the stretch ratio. The PET films described in Patent Documents 2 and 3 reduce the in-plane phase difference by reducing the stretch ratio difference between the MD direction (flow direction) and the TD direction (width direction).

[0015] For PET films that reduce in-plane phase difference without reducing stretch ratio, and for polyester films containing such PET films with easy-to-adhesive layers, the planar orientation degree ΔP tends to increase. However, the inventors of this application have confirmed that if the planar orientation degree of the polyester film with easy-to-adhesive layers is large, other adverse conditions arise. For polyester films with easy-to-adhesive layers and large planar orientation degree ΔP, sometimes the adhesion between the easy-to-adhesive layer and the polyester film decreases.

[0016] The aforementioned problems can be addressed by selecting the material for the easy-to-adhesive layer. However, the selection range of materials for the easy-to-adhesive layer is limited in these solutions, thus restricting product design. Therefore, these solutions lack practicality. Furthermore, in the case of overall optical design of optical laminates, if an easy-to-adhesive layer of a specific material exists on the PET film, the selection of materials for the functional layers formed on that easy-to-adhesive layer will also be constrained. Summary of the Invention

[0017] The purpose of this invention is to improve the adhesion between the polyester film and the easy-to-adhere layer in polyester films with a high degree of planar orientation and an easy-to-adhere layer.

[0018] It should be noted that the invention described in Patent Document 4 aims to solve the same problem as that described above in this invention. The optical laminate described in Patent Document 4 sequentially comprises a polyester film with an easy-to-adhere layer, a textured layer, and an anti-fouling layer. According to paragraphs 0073 and 0122 of Patent Document 4, the optical laminate of Patent Document 4 improves the adhesion between the easy-to-adhere layer and the polyester film through the surface shape of the textured layer and its slippage with the anti-fouling layer. That is, Patent Document 4 improves the adhesion between the easy-to-adhere layer and the polyester film in an optical laminate on which a functional layer is deposited on a polyester film with an easy-to-adhere layer. According to the evaluation results of Comparative Example 6 described later, the polyester film with an easy-to-adhere layer in Patent Document 4 cannot improve the adhesion between the easy-to-adhere layer and the polyester film before the functional layer is deposited. As demonstrated in the embodiments described later, this invention improves the adhesion between the easy-to-adhere layer and the polyester film in a polyester film with an easy-to-adhere layer before the functional layer is deposited.

[0019] According to one embodiment of the present invention, the film with the easy-to-adhere layer comprises a polyester film and an easy-to-adhere layer, the surface orientation degree is 0.150 or more and 0.195 or less, and the average value of δq / δa of the surface of the easy-to-adhere layer is 1.125 or more and 1.80 or less.

[0020] Calculation of the average value of δq / δa

[0021] A 10 μm × 10 μm region on the surface of the aforementioned easily bondable layer was measured using the phase mode of an atomic force microscope. The phase signal distribution on the surface of the easily bondable layer was obtained through this measurement. The unit of the phase signal is [deg].

[0022] Let the arithmetic mean of the phase signal shown in Equation 1 below be δa. Let the root mean square of the phase signal shown in Equation 2 below be δq.

[0023] (In Equations 1 and 2 below, rectangular coordinate axes X and Y are arranged on the reference surface representing the average value of the phase signal, the axis orthogonal to the reference surface is set as the Z axis, and the surface of the phase signal is set as f(x,y). In Equations 1 and 2 below, the size of the region for calculating δa and δq is set as Lx and Ly. In Equations 1 and 2 below, Ar = Lx × Ly.)

[0024] Seven 2μm×2μm measurement evaluation areas were selected from a 10μm×10μm measurement area. δa, δq, and δq / δa were calculated for each of these seven evaluation areas. Based on the five δq / δa values ​​remaining after excluding the maximum and minimum values ​​from the seven δq / δa values, the average value of δq / δa was calculated.

[0025] [Mathematical Expression 1]

[0026] [Mathematical Expression 2]

[0027] According to the present invention, in a polyester film with a highly oriented surface layer and an easy-to-adhere layer, the adhesion between the polyester film and the easy-to-adhere layer can be improved. Attached Figure Description

[0028] Figure 1 This is a diagram illustrating one embodiment of the present invention, showing a longitudinal cross-sectional view of an example of a polyester film with an easy-to-adhere layer.

[0029] Figure 2 It shows that it contains a plurality of Figure 1 A perspective view of an example of a polyester film article with an easy-to-adhere layer.

[0030] Figure 3 This is a diagram used to illustrate this embodiment, and it is a longitudinal cross-sectional view showing an example of an optical laminate.

[0031] Figure 4 It shows that it contains a plurality of Figure 3 A perspective view of an example of a laminated article of an optical laminate.

[0032] Figure 5 This is a cross-sectional view showing an example of a polarizer comprising a polyester film with an easy-to-adhere layer and an optical laminate.

[0033] Figure 6 This is a cross-sectional view showing an example of a panel comprising a polyester film with an easy-to-adhere layer and an example of a surface plate comprising a polyester film with an easy-to-adhere layer and an optical laminate.

[0034] Figure 7 This is a cross-sectional view showing an example of an image display panel and an image display device comprising a polyester film with an easy-to-adhere layer and an optical laminate.

[0035] Figure 8A This is a diagram used to illustrate a bending test.

[0036] Figure 8B This is a diagram used to illustrate a bending test.

[0037] Figure 8C This is a diagram used to illustrate a bending test.

[0038] Figure 9 This is a schematic diagram illustrating the manufacturing apparatus for optical laminates used in transportability evaluation. Detailed Implementation

[0039] One embodiment of the present invention relates to the following <1> ~ <19> .

[0040] <1>

[0041] A polyester film with an easy-to-adhere layer, comprising a polyester film and an easy-to-adhere layer, having an orientation degree of 0.150 or more and 0.195 or less, and an average value of δq / δa of the surface of the easy-to-adhere layer of 1.125 or more and 1.80 or less.

[0042] Calculation of the average value of δq / δa

[0043] A 10 μm × 10 μm region on the surface of the aforementioned easily bondable layer was measured using the phase mode of an atomic force microscope. The phase signal distribution on the surface of the easily bondable layer was obtained through this measurement. The unit of the phase signal is [deg].

[0044] Let δa be the arithmetic mean of the phase signal shown in Equation 1 below. Let δq be the root mean square of the phase signal shown in Equation 2 below. In Equations 1 and 2 below, rectangular coordinate axes X and Y are arranged on the reference surface representing the average value of the phase signal, the axis orthogonal to the reference surface is set as the Z axis, and the surface of the phase signal is set as f(x,y). In Equations 1 and 2 below, the size of the region for calculating δa and δq is set as Lx and Ly, respectively. In Equations 1 and 2 below, Ar = Lx × Ly.

[0045] Seven 2μm×2μm measurement evaluation areas were selected from a 10μm×10μm measurement area. δa, δq, and δq / δa were calculated for each of these seven evaluation areas. Based on the five δq / δa values ​​remaining after excluding the maximum and minimum values ​​from the seven δq / δa values, the average value of δq / δa was calculated.

[0046] [Mathematical Expression 3]

[0047] [Mathematical Expression 4]

[0048] <2>

[0049] according to <1> The polyester film with the easy-to-adhere layer, wherein the coefficient of variation of δq / δa calculated based on the above 5 δq / δa values ​​is less than 0.150.

[0050] <3>

[0051] according to <1> or <2> The polyester film with the easy-to-adhere layer, wherein when the refractive index in the slow axis direction in the same plane is defined as nx and the refractive index in the direction orthogonal to the slow axis in the same plane is defined as ny, nx and ny satisfy the following relationship.

[0052] nx - ny ≤ 0.0300

[0053] <4>

[0054] according to <1> ~ <3> The polyester film with an easy-to-adhere layer as described in any one of the above descriptions has a thickness of 10 μm or more and 75 μm or less.

[0055] <5>

[0056] according to <1> ~ <4> The polyester film with an easy-to-adhere layer as described in any one of the above statements has an in-plane phase difference of less than 2000 nm.

[0057] <6>

[0058] according to <1> ~ <4> The polyester film with an easy-to-adhere layer as described in any one of the above-mentioned methods has an in-plane phase difference of 1800 nm or more and 2800 nm or less.

[0059] <7>

[0060] according to <1> ~ <6> The polyester film with an easy-to-adhere layer as described in any one of the above examples has an Nz coefficient greater than 2.0.

[0061] <8>

[0062] A membrane article having a plurality of <1> ~ <7> The polyester film with an easy-to-adhere layer as described in any one of the following.

[0063] <9>

[0064] according to <8> The membrane article is formed by winding around the winding axis.

[0065] <10>

[0066] An optical laminate, which in <1> ~ <7> The polyester film described in any one of the above-mentioned easy-to-adhere layers has one or more functional layers.

[0067] <11>

[0068] according to <10> The optical laminate, wherein, among the more than one functional layer, the functional layer in contact with the easily bondable layer comprises a cured product of an ionizing radiation curable resin composition.

[0069] <12>

[0070] according to <10> or <11> The optical laminate, wherein the surface of the side of the optical laminate having the functional layer has a contact angle of 80 degrees or more with pure water.

[0071] <13>

[0072] A laminated article having a plurality of <10> ~ <12> The optical laminate as described in any one of the following.

[0073] <14>

[0074] according to <13> The laminated article is formed by winding around the winding axis.

[0075] <15>

[0076] A polarizer comprises, in sequence, a first transparent protective plate, a polarizing element, and a second transparent protective plate, wherein at least one of the first and second transparent protective plates is... <10> ~ <12> In any one of the optical laminates, the polyester film with the easy-to-adhere layer is located between the functional layer and the polarizing element.

[0077] <16>

[0078] A panel having a support plate and <1> ~ <7> The polyester film with an easy-to-adhere layer as described in any one of the following.

[0079] <17>

[0080] A surface panel having a support plate and <10> ~ <12> In any one of the optical laminates, the polyester film with the easy-to-adhere layer is located between the functional layer and the support plate.

[0081] <18>

[0082] An image display panel comprising display elements and <10> ~ <12> The optical laminate as described in any one of the following.

[0083] <19>

[0084] An image display device comprising <18> The aforementioned image display panel.

[0085] The following describes the polyester film with an easy-to-adhere layer, the film article, the optical laminate, the laminate article, the polarizer, the surface plate, the image display panel, and the image display device of this embodiment.

[0086] It should be noted that the description of the numerical range of "AA~BB" in this instruction manual refers to "above AA and below BB".

[0087] In this specification, the candidate upper limit and candidate lower limit values ​​for a numerical range are sometimes stated in different statements. In such statements, the numerical range can be constructed by combining any candidate upper limit value and any candidate lower limit value. For example, consider the statement: "Parameter B can be above A1, above A2, or above A3. Parameter B can be below A4, below A5, or below A6." In this example, the numerical range of parameter B can be above A1 and below A4, above A1 and below A5, above A1 and below A6, above A2 and below A4, above A2 and below A5, above A2 and below A6, above A3 and below A4, above A3 and below A5, or above A3 and below A6.

[0088] <<<Polyester film with easy-to-adhesion layer>>>

[0089] The polyester film with an easy-to-adhere layer in this embodiment includes a polyester film and an easy-to-adhere layer located on the polyester film.

[0090] Figure 1 This is a longitudinal cross-sectional view showing an example of a polyester film with an easy-to-adhere layer. For example... Figure 1 As shown, the polyester film 15 with an easy-to-adhere layer includes a first surface 15a and a second surface 15b. The first surface 15a and the second surface 15b can be a pair of main surfaces of the polyester film 15 with an easy-to-adhere layer. The polyester film 15 with an easy-to-adhere layer includes an easy-to-adhere layer 25 and a polyester film 20 sequentially from the first surface 15a toward the second surface 15b. In the illustrated example, the first surface 15a is composed of the easy-to-adhere layer 25. In the illustrated example, the second surface 15b is composed of the polyester film 20. The polyester film 15 with an easy-to-adhere layer is used in the optical laminate 10.

[0091] The polyester film with an easy-to-adhesive layer in this embodiment includes the following features (A) and (B). As described below, based on the combination of features (A) and (B), the adhesion between the polyester film and the easy-to-adhesive layer can be improved in a polyester film with an easy-to-adhesive layer that has high mechanical strength.

[0092] Feature (A): The degree of orientation ΔP is above 0.150 and below 0.195; Feature (B): The average value of δq / δa on the surface of the easily bonded layer is above 1.125 and below 1.80.

[0093] <Calculation of the average value of δq / δa in feature B>

[0094] A 10 μm × 10 μm region on the surface of the aforementioned easily bondable layer was measured using the phase mode of an atomic force microscope. The phase signal distribution on the surface of the easily bondable layer was obtained through this measurement. The unit of the phase signal is [deg].

[0095] Let δa be the arithmetic mean of the phase signal shown in Equation 1 below. Let δq be the root mean square of the phase signal shown in Equation 2 below. In Equations 1 and 2 below, rectangular coordinate axes X and Y are arranged on the reference surface representing the average value of the phase signal, the axis orthogonal to the reference surface is set as the Z axis, and the surface of the phase signal is set as f(x,y). In Equations 1 and 2 below, the size of the region for calculating δa and δq is set as Lx and Ly, respectively. In Equations 1 and 2 below, Ar = Lx × Ly.

[0096] Seven 2μm×2μm measurement evaluation areas were selected from a 10μm×10μm measurement area. δa, δq, and δq / δa were calculated for each of these seven evaluation areas. Based on the five δq / δa values ​​remaining after excluding the maximum and minimum values ​​from the seven δq / δa values, the average value of δq / δa was calculated.

[0097] [Mathematical Expression 5]

[0098] [Mathematical Expression 6]

[0099] <<Characteristics of Polyester Films with Easy-Adhesive Layers>>

[0100] <Feature (A): Surface orientation degree ΔP>

[0101] As the above features The polyester film with an easy-adhesion layer has a surface orientation degree ΔP of 0.150 or more and 0.195 or less.

[0102] The surface orientation degree ΔP is represented 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 in which the refractive index is highest in the plane of the polyester film with an easy-adhesion layer. The fast axis is the direction orthogonal to the slow axis in the plane of the polyester film with an easy-adhesion layer.

[0103] In the present specification, unless otherwise specified, the refractive indices nx, ny, and nz, the surface orientation degree ΔP, the in-plane retardation, and the thickness direction retardation are values for light having a wavelength of 589 nm. In the present specification, the in-plane retardation is also referred to as "Re". In the present specification, the thickness direction retardation is also referred to as "Rth".

[0104] In the feature (A), the surface orientation degree ΔP represented by "((nx + ny) / 2) - nz" is specified to be 0.150 or more and 0.195 or less. The surface orientation degree ΔP is a parameter indicating the strength of the orientation of the entire surface of the film-shaped member as the object.

[0105] As specified as the feature (A), the surface orientation degree ΔP is set to a lower limit. By setting the lower limit to the surface orientation degree ΔP, the polyester film with an easy-adhesion layer can be given excellent mechanical strength. From this viewpoint, the surface orientation degree ΔP can be 0.150 or more, can be 0.151 or more, can be 0.154 or more, can be 0.156 or more, can be 1.58 or more, can be 0.161 or more, or can be 0.176 or more.

[0106] According to the research by the present inventors, the following insights were obtained. By making the surface orientation degree ΔP of the polyester film with an easy-adhesion layer 0.150 or more, it is possible to improve the mechanical strength. It was further found that, in the case where the feature (A) is satisfied while the feature (B) is satisfied, it is possible to effectively improve the puncture resistance and the bending resistance in the mechanical strength. The puncture resistance and the bending resistance are indexes indicating the mechanical properties in a local region, and the puncture resistance is an index indicating the mechanical properties in a local region more than the bending resistance. It was confirmed that, in the case where the feature (A) is satisfied while the feature (B) is satisfied, it is possible to extremely effectively improve the puncture resistance, which is an evaluation index of the mechanical strength in a local region, compared to the overall mechanical strength. By improving the puncture resistance, it is possible to give the polyester film with an easy-adhesion layer and the optical laminate impact resistance, and it is possible to suppress the generation of local damage, such as the formation of a through hole, in the polyester film with an easy-adhesion layer and the optical laminate.

[0107] For example, in the production of the optical laminate, or the like, when the polyester film with an easy-adhesion layer is bent, a local damage can occur in the polyester film with an easy-adhesion layer. For example, a hole can be formed in the polyester film with an easy-adhesion layer. Recently, with the increase in size of display devices, the optical laminate, the polyester film with an easy-adhesion layer are also increasing in size. The polyester film with an easy-adhesion layer that is increasing in size can be bent with a large curvature, and thus the polyester film with an easy-adhesion layer is likely to be locally damaged. In addition, the optical laminate including the polyester film with an easy-adhesion layer is used in a foldable use, that is, a foldable use in which the optical laminate is folded in use. When used in the foldable use, the polyester film with an easy-adhesion layer is likely to be locally damaged.

[0108] Puncture resistance is a mechanical property that has increased in importance in recent years. The present inventors have confirmed that by setting a lower limit to the planar orientation degree ΔP, the mechanical strength of the polyester film with an easy-adhesion layer can be improved. In the case where the lower limit is set to the planar orientation degree ΔP while satisfying the characteristic (B), the puncture resistance can be improved. In the case where the characteristic (B) is satisfied, the puncture resistance shows a stronger correlation with the planar orientation degree ΔP than in the case where the characteristic (B) is not satisfied.

[0109] In the past, as a mechanical property, the focus was not so much on the pure mechanical strength as on scratch resistance. As an evaluation test of the scratch resistance, pencil hardness, steel wool resistance, and the like can be exemplified. The scratch resistance is not necessarily correlated with the puncture resistance. In fact, the present inventors have confirmed that sometimes the puncture resistance of the polyester film with an easy-adhesion layer having a high pencil hardness is insufficient. According to these backgrounds, the effect of being able to stably improve the puncture resistance by the combination of the characteristic (A) and the characteristic (B) is a different property effect that is beyond the range predictable from the current technical level.

[0110] The detailed mechanism by which the puncture resistance is improved by the combination of the characteristic (A) and the characteristic (B) is not clear. It is presumed that by the characteristic (A), the orientation is improved as a whole, and by the characteristic (B), the mechanical property can be homogenized from a more local perspective than the puncture resistance, so that not only the overall mechanical strength but also the more local bending resistance and the puncture resistance as an evaluation index of a mechanical strength that is more local than the bending resistance can be stably improved. However, the present application is not limited to the above presumption.

[0111] In the characteristic (A), the planar orientation degree ΔP is set to an upper limit. By setting the upper limit to the planar orientation degree ΔP, the damage such as cracking or breaking of the polyester film with an easy-adhesion layer can be suppressed. When the planar orientation degree ΔP exceeds 0.195, the bending resistance and the puncture resistance can decrease. From this viewpoint, the planar orientation degree ΔP can be 0.195 or less, can be 0.193 or less, can be 0.191 or less, can be 0.189 or less, or can be 0.187 or less.

[0112] The orientation degree ΔP can 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 orientation degree ΔP can 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 orientation degree ΔP can be 0.154 to 0.195, 0.154 to 0.193, 0.154 to 0.191, 0.154 to 0.189, or 0.154 to 0.187. The orientation degree ΔP can be 0.156 to 0.195, 0.156 to 0.193, 0.156 to 0.191, 0.156 to 0.189, or 0.156 to 0.187. The orientation degree ΔP can be 0.158 to 0.195, 0.158 to 0.193, 0.158 to 0.191, 0.158 to 0.189, or 0.158 to 0.187. The orientation degree ΔP can 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 orientation degree ΔP can be 0.176 or higher and 0.195 or lower, or 0.158 or higher and 0.193 or lower, or 0.158 or higher and 0.191 or higher, or 0.158 or higher and 0.189 or lower, or 0.158 or higher and 0.187 or lower.

[0113] The nx, ny, nz, planar orientation ΔP, and the in-plane phase difference Re and thickness direction phase difference Rth of the polyester film with the easy-to-adhesive layer (described later) were determined using Otsuka Electronics' "RETS-100" delay measurement device. The measurement was not performed on the easy-to-adhesive layer or the polyester film itself, but on the polyester film with the easy-to-adhesive layer. The determination of each value using the "RETS-100" was performed through the following steps (P1) to (P6).

[0114] (P1) First, before starting the measurement, ensure the light source is lit for at least 60 minutes. This allows the light source output to stabilize. Then, select the rotational polarization method and choose the θ mode (the mode for measuring the phase difference in the angular direction and calculating Rth). By selecting the θ mode, the stage becomes a tilting rotating stage.

[0115] (P2) Next, input the following measurement conditions into the measuring device.

[0116] Delay measurement range: Rotational polarization method

[0117] Determine the diameter of the light spot: 5mm

[0118] Tilt angle range: -40° to 40°

[0119] Measurement wavelength range: 400–800 nm

[0120] Additionally, regarding the input of "average refractive index N of the film" and "film thickness", for "average refractive index N of the film", enter the average refractive index of the polyester film contained in the easily bondable layer of the polyester film being measured. If the polyester film used is a PET film, enter "1.617" as "average refractive index N of the film". Regarding "film thickness", enter the thickness of the polyester film with the easily bondable layer as measured by the method described later.

[0121] (P3) Then, background data is acquired with no sample in the measuring device. The measuring device is a closed system. Background data is acquired each time the light source is turned on.

[0122] (P4) Next, the samples are placed in the measuring apparatus. When multiple samples are taken from the polyester film with the easy-to-adhesive layer that is the object of measurement, the multiple samples are aligned in orientation. Specifically, alignment is performed according to the following steps: Mark each of the multiple samples taken from the polyester film with the easy-to-adhesive layer with a first reference direction and an arrow indicating a first side in the first reference direction. Mark a second reference direction and an arrow indicating a first side in the second reference direction on the sample stage where the samples are arranged sequentially. When placing each sample on the sample stage, make the first reference direction and the second reference direction parallel, and align the first side in the first reference direction and the first side in the second reference direction.

[0123] (P5) Begin measurement. First, the measuring device rotates the sample 360° while determining the slow axis. Next, the measuring device prompts for options for slow and fast axes; therefore, the slow axis is selected. By selecting the slow axis, the measuring device rotates the sample stage around the slow axis while measuring the delay (Re). The measuring device measures the delay (Re) for several wavelengths within a set measurement wavelength range (400nm to 800nm) at each 10° angle within a set tilt angle range (-40° to 40°). The measurement value with a tilt angle of 0° and a wavelength of 589nm is taken as the delay (Re) value for the sample being measured.

[0124] (P6) Next, select the "Display 3D Refractive Index" command. A data table will be displayed, but it will not be used as the measurement result. Select the "Set" button. Then, enter the "Average Refractive Index N of the Film" and the "Film Thickness".

[0125] Regarding "Average Refractive Index N of the Film," enter the average refractive index of the polyester film containing the easy-to-adhesive layer, which is the object of the measurement. If the polyester film used is a PET film, enter "1.617" for "Average Refractive Index N of the Film." Regarding "Film Thickness," enter the thickness of the polyester film with the easy-to-adhesive layer, as measured by the method described later. The measured value for the polyester film with the easy-to-adhesive layer, which is the object of the measurement, will then be output.

[0126] Here, the refractive index nx, refractive index ny, refractive index nz, phase difference Rth in the thickness direction, and plane orientation degree ΔP are measured. The measurement results are input for each parameter with respect to several wavelengths. Among the obtained measurement values, the values ​​for wavelength 589nm are set as the values ​​of refractive index nx, refractive index ny, refractive index nz, phase difference Rth in the thickness direction, and plane orientation degree ΔP of the sample being measured.

[0127] nx, ny, nz, ΔP, Re, and Rth were measured at seven locations. The maximum and minimum values ​​were excluded from the seven measurements, and the average of the remaining five values ​​was calculated. This average was then used as the value for each of nx, ny, nz, ΔP, Re, and Rth.

[0128] Before determining nx, ny, nz, plane orientation degree ΔP, in-plane phase difference Re, and thickness direction phase difference Rth, the sample was prepared in the measurement environment for 16 hours. The measurement environment was set at a temperature of 23℃±2℃ and a relative humidity of 50%±5%.

[0129] <Feature B: Average value of δq / δa>

[0130] As described in feature (B), the polyester film with the easy-to-adhere layer has an average δq / δa value of 1.125 or higher and 1.80 or lower on the surface of the easy-to-adhere layer. The "average value of δq / δa" is determined as follows.

[0131] A 10 μm × 10 μm region on the surface of the easily bondable layer was measured using phase mode atomic force microscopy. Figure 1 In the example shown, a 10μm × 10μm region of the surface of the first surface 15a is used as the measurement object. This measurement yields the distribution of the phase signal on the surface of the easily bonded layer. The unit of the phase signal is [deg]. “δa” is the arithmetic mean of the phase signal shown in Equation 1 below. “δq” is the root mean square of the phase signal shown in Equation 2 below.

[0132] In Equations 1 and 2 below, rectangular coordinate axes X and Y are arranged on a reference surface representing the average value of the phase signal, the axis orthogonal to the reference surface is designated as the Z-axis, and the surface of the phase signal is designated as f(x,y). In Equations 1 and 2 below, the sizes of the regions for calculating δa and δq are designated as Lx and Ly, respectively. In Equations 1 and 2 below, Ar = Lx × Ly.

[0133] Seven 2μm × 2μm measurement evaluation areas were selected from a 10μm × 10μm measurement area. δa, δq, and δq / δa were calculated for each of these seven areas. Based on the five δq / δa values ​​remaining after excluding the maximum and minimum values ​​from the seven δq / δa values, the average value of δq / δa was calculated. This average value was then used as the average value of δq / δa.

[0134] The seven measurement and evaluation areas mentioned above can partially overlap. However, the overlap between any measurement and evaluation area and the other six measurement and evaluation areas shall be less than 25% based on the area of ​​the measurement and evaluation area.

[0135] Other measurement conditions used to determine the average value of δq / δa will be explained later.

[0136] [Mathematical Expression 7]

[0137] [Mathematical Expression 8]

[0138] Without an easy-adhesive layer, even if a functional layer is formed on the polyester film, good adhesion of the optical laminate consisting of the polyester film and the functional layer cannot be achieved. Furthermore, even if an easy-adhesive layer is formed on the polyester film, if the average value of δq / δa on the surface of the easy-adhesive layer exceeds 1.80, good adhesion of the optical laminate consisting of the polyester film, the easy-adhesive layer, and the functional layer in sequence cannot be achieved.

[0139] The technical significance of the average value of δq / δa on the surface of the easily bonded layer is explained below.

[0140] δa and δq are parameters related to the phase signal when measuring a specified area of ​​the surface of an easily bondable layer using the phase mode of atomic force microscopy. The unit of the phase signal is [deg]. The aforementioned phase signal represents the viscoelasticity of the easily bondable layer surface. Atomic force microscopy measures the surface properties of a sample by scanning the surface with a tiny probe mounted on a leaf spring. In phase mode, by vibrating the probe while performing the measurement, changes in the vibration phase within the surface can be mapped. Therefore, in phase mode, the contrast caused by viscoelastic differences in surface composition can be mapped.

[0141] δa is the arithmetic mean of the phase signal over a specified region. δq is the root mean square (RMS) of the phase signal over the specified region. The RMS emphasizes the deviation from the arithmetic mean. Even if the arithmetic mean δa is the same, a large deviation in the phase signal over the specified region will result in a larger average value of the RMS δq. Similarly, even if the arithmetic mean δa is the same, a large deviation in the phase signal over the specified region will result in a larger average value of δq / δa. Conversely, even if the arithmetic mean δa is the same, a small deviation in the phase signal over the specified region will result in a smaller average value of δq / δa. In other words, an easily bonded layer with a small arithmetic mean of δq / δa indicates that the phase signal over the specified region is concentrated near the arithmetic mean of the phase signal, suggesting a small deviation in the phase signal over the specified region. Since the phase signal represents the viscoelasticity of the easily bonded layer's surface, an easily bonded layer with a small average value of δq / δa indicates a small change in viscoelasticity over the specified region.

[0142] It should be noted that phase signals represent relative changes within the same image. Therefore, it is generally not possible to compare δa and δq of different samples. In this invention, we focus on the ratio of δa to δq, δq / δa. As mentioned above, δq / δa is a parameter representing the phase deviation within a sample and is a dimensionless parameter. Therefore, it can be said that δq / δa is appropriate as a parameter for comparing phase deviations between different samples.

[0143] As mentioned above, a low average δq / δa value in an easy-to-bond layer indicates a small variation in viscoelasticity within a specified region. Furthermore, polyester films containing easy-to-bond layers with low average δq / δa values ​​can improve the adhesion between the easy-to-bond layer and the polyester film. The good adhesion of optical laminates is considered to be due to the following reasons.

[0144] If other components come into contact with the functional layer of the optical laminate, a specified stress is generated. This stress is transmitted through the functional layer and the easy-adhesive layer to the interface between the polyester film and the easy-adhesive layer. The mode of stress transmission varies depending on the viscoelasticity value of the easy-adhesive layer. Therefore, when the in-plane viscoelasticity of the easy-adhesive layer varies greatly, the magnitude of the stress transmitted to the interface between the polyester film and the easy-adhesive layer varies depending on the in-plane location. Therefore, when the average δq / δa of the easy-adhesive layer is large, the optical laminate is prone to interfacial delamination by applying large stress to a specified location in the in-plane. On the other hand, it is believed that when the average δq / δa of the easy-adhesive layer is small, the stress is dispersed in-plane, thus suppressing interfacial delamination of the optical laminate and achieving high adhesion. It is understood that when the average δq / δa of the easy-adhesive layer is small, it is difficult to form a delamination initiation point. However, the present invention is not limited to this conjecture.

[0145] One reason why the viscoelasticity of the easy-to-adhesive layer varies depending on its location can be considered is the compatibility of the components constituting the easy-to-adhesive layer. For example, by improving the compatibility of the components contained in the coating liquid used to form the easy-to-adhesive layer, the viscoelasticity of the easy-to-adhesive layer can be homogenized.

[0146] The average value of δq / δa is affected by the compatibility of the coating liquid used to form the easy-to-bond layer and the phase separation state of the components contained in the coating liquid. For example, even if the resin composition constituting the easy-to-bond layer is the same, the average value of δq / δa can be adjusted by 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 the changes in the phase separation state of the easy-to-bond layer caused by the drying conditions and curing conditions during the formation of the cured film from the coating liquid.

[0147] As another reason why the viscoelasticity of the easy-to-bond layer varies depending on its location, the deviation in molecular orientation of the polyester film is taken into consideration. As will be described later, the viscoelasticity of the easy-to-bond layer can be homogenized by making the Nz coefficient greater than 2.0.

[0148] The average value of δq / δa can be below 1.80, 1.79, 1.74, 1.71, 1.68, 1.65, 1.61, 1.59, 1.56, or 1.38. The smaller the average value of δq / δa, the closer the viscoelasticity of the easy-to-bond layer surface is to homogeneity. By setting an upper limit on the average value of δq / δa, the homogenization of mechanical properties can be ensured, improving the adhesion between the polyester film and the easy-to-bond layer.

[0149] If the viscoelasticity of the easy-to-adhere layer surface is too homogeneous, the components of the functional layer will have difficulty penetrating into the easy-to-adhere layer. Therefore, if the viscoelasticity of the easy-to-adhere layer surface is too homogeneous, the adhesion between the easy-to-adhere layer and the functional layer will decrease. From this perspective, the average value of δq / δa can be above 1.125, above 1.13, above 1.20, above 1.25, above 1.31, or above 1.33.

[0150] The average value of δq / δa can be above 1.125 and below 1.80, above 1.125 and below 1.77, above 1.125 and below 1.74, above 1.125 and below 1.71, above 1.125 and below 1.68, above 1.125 and below 1.65, above 1.125 and below 1.61, above 1.125 and below 1.59, above 1.125 and below 1.56, or above 1.125 and below 1.38. The average value of δq / δa can be above 1.13 and below 1.80, above 1.13 and below 1.77, above 1.13 and below 1.74, above 1.13 and below 1.71, above 1.13 and below 1.68, above 1.13 and below 1.65, above 1.13 and below 1.61, above 1.13 and below 1.59, above 1.13 and below 1.56, or above 1.13 and below 1.38. The average value of δq / δa can be above 1.20 and below 1.80, above 1.20 and below 1.77, above 1.20 and below 1.74, above 1.20 and below 1.71, above 1.20 and below 1.68, above 1.20 and below 1.65, above 1.20 and below 1.61, above 1.20 and below 1.59, above 1.20 and below 1.56, or above 1.20 and below 1.38. The average value of δq / δa can be above 1.25 and below 1.80, above 1.25 and below 1.77, above 1.25 and below 1.74, above 1.25 and below 1.71, above 1.25 and below 1.68, above 1.25 and below 1.65, above 1.25 and below 1.61, above 1.25 and below 1.59, above 1.25 and below 1.56, or above 1.25 and below 1.38. The average value of δq / δa can be above 1.31 and below 1.80, above 1.31 and below 1.77, above 1.31 and below 1.74, above 1.31 and below 1.71, above 1.31 and below 1.68, above 1.31 and below 1.65, above 1.31 and below 1.61, above 1.31 and below 1.59, above 1.31 and below 1.56, or above 1.31 and below 1.38.The average value of δq / δa can be above 1.33 and below 1.80, above 1.33 and below 1.77, above 1.33 and below 1.74, above 1.33 and below 1.71, above 1.33 and below 1.68, above 1.33 and below 1.65, above 1.33 and below 1.61, above 1.33 and below 1.59, above 1.33 and below 1.56, or above 1.33 and below 1.38.

[0151] The average value of δq / δa on the surface of the aforementioned easy-to-adhere layer is the value within a specified 10μm × 10μm area. The proportion of the area with a δq / δa value of 1.80 or less in the total surface area of ​​the easy-to-adhere layer is preferably 80% or more, more preferably 90% or more, further preferably 95% or more, even more preferably 98% or more, and most preferably 100%.

[0152] In this invention, δa can be calculated using Equation 1 above. Equation 1 references the formula for the arithmetic mean height from ISO 25178-2:2012. In the formula for the arithmetic mean height of ISO 25178-2:2012, elevation is used as the data for the Z-axis. In Equation 1, the phase signal [deg] is used instead of elevation as the data for the Z-axis. That is, the difference between δa and the arithmetic mean height of ISO 25178-2:2012 is that the former uses the phase signal [deg] as the data for the Z-axis, while the latter uses the elevation [μm] as the data for the Z-axis.

[0153] In this invention, δq can be calculated using Equation 2 above. Equation 2 references the formula for the root mean square height from ISO 25178-2:2012. In the formula for the root mean square height of ISO 25178-2:2012, elevation is used as the data for the Z-axis. In Equation 2, the phase signal [deg] is used instead of elevation as the data for the Z-axis. That is, the difference between δq and the root mean square height of ISO 25178-2:2012 is that the former uses the phase signal [deg] as the data for the Z-axis, while the latter uses the elevation [μm] as the data for the Z-axis.

[0154] The average value of δq / δa can be calculated using the steps Q1 to Q4 below.

[0155] (Q1) A 10 μm × 10 μm region on the surface of the easily bondable layer is measured using the phase mode of an atomic force microscope. (As an example, when using a Shimadzu SPM-9600 microscope, it is preferable to adjust the P gain, I gain, and bias.)

[0156] (Q2) Seven 2μm×2μm measurement and evaluation areas were selected from the 10μm×10μm measurement area.

[0157] (Q3) Calculate δa, δq, and δq / δa within the selected 7 measurement and evaluation areas.

[0158] (Q4) Calculate the average value of δq / δa based on the 5 δq / δa values ​​after excluding the maximum and minimum values ​​from the 7 δq / δa values.

[0159] In Q1 above, an example of an atomic force microscope is the Shimadzu Corporation's product name "SPM-9600". The measurement using the atomic force microscope is not performed on the easy-to-adhesive layer that has been peeled off from the polyester film with the easy-to-adhesive layer, but on the surface of the polyester film with the easy-to-adhesive layer (first side 15a).

[0160] In Q2 above, the selected 2μm × 2μm region is chosen from areas where the maximum height of the amplitude measured using atomic force microscopy is 90nm or less. The maximum height is the maximum height Sz according to ISO 25178-2:2012. By selecting a 2μm × 2μm region from areas where Sz is 90nm or less, the influence of foreign matter and defects can be easily suppressed. The seven measurement evaluation regions are preferably selected in a non-overlapping manner, but overlap is also possible. It should be noted that, in the case of overlapping measurement evaluation regions, the overlap ratio between any one measurement evaluation region and the other six measurement evaluation regions is 25% or less based on the area of ​​the measurement evaluation region. More preferably, the overlap ratio between any one measurement evaluation region and the other six measurement evaluation regions is 12% or less, and even more preferably 5% or less.

[0161] In Q2 above, to suppress the influence of foreign matter and defects, the selected 2μm × 2μm measurement and evaluation region was chosen from areas where the arithmetic mean height of the amplitude measured using atomic force microscopy was less than 10nm. The arithmetic mean height was the arithmetic mean height Sa of ISO 25178-2:2012.

[0162] As explained above, the polyester film with an easy-to-adhesive layer in this embodiment has the aforementioned features (A) and (B). Feature (A) improves the mechanical strength of the polyester film with the easy-to-adhesive layer. Feature (B) improves the adhesion between the easy-to-adhesive layer and the polyester film in the polyester film with the easy-to-adhesive layer. Therefore, the combination of features (A) and (B) solves the problem of improving the adhesion between the polyester film and the easy-to-adhesive layer in a polyester film with a high degree of planar orientation. Furthermore, it also solves the problem of improving the adhesion between the polyester film and the easy-to-adhesive layer while imparting high mechanical strength to the polyester film with the easy-to-adhesive layer.

[0163] Furthermore, as described above, by combining features (A) and (B), the mechanical strength of the polyester film with the easy-to-adhere layer can be stably improved, particularly the puncture resistance of the polyester film with the easy-to-adhere layer. More specifically, through the synergistic effect of the combination of features (A) and (B), local mechanical strengths such as puncture resistance and flexural strength can be stably improved.

[0164] It is believed that setting a lower limit for the face orientation degree ΔP can improve mechanical strength. Furthermore, according to the inventors' research, setting an upper limit for the face orientation degree ΔP can suppress damage such as cracking and breakage, thereby improving flexural and puncture resistance. However, even with polyester films with an easy-to-adhere layer whose face orientation degree ΔP is adjusted according to feature (A), flexural and puncture resistance can sometimes be unexpectedly insufficient. Test samples with insufficient flexural and puncture resistance are part of all test samples. The inventors have confirmed that the average value of δq / δa of polyester films with an easy-to-adhere layer that have insufficient flexural and puncture resistance does not meet feature (B).

[0165] For polyester films with an easy-to-adhesive layer that meet characteristic (A), when the average value of δq / δa increases, approximately 10% to 20% of samples obtained from the same polyester film with an easy-to-adhesive layer exhibit insufficient flexural or puncture resistance. The detailed mechanism underlying this phenomenon is unclear, but it is speculated to be due to the following:

[0166] When the average value of δq / δa is large, for example, when the average value of δq / δa exceeds 1.80, phase separation of the easily bonded layer is expected. It is speculated that agglomeration occurs in the easily bonded layer where phase separation has taken place. Agglomeration within the easily bonded layer can become the starting point for defects such as cracks and fractures.

[0167] Furthermore, when the average value of δq / δa is large, for example, exceeding 1.80, the viscoelasticity of the easy-to-bond layer exhibits in-plane deviation, thus the penetration state of the coating liquid used to form the functional layer into the easy-to-bond layer is not constant in-plane. If other components come into contact with the functional layer of the optical laminate, a specified stress is generated. This stress is transmitted through the functional layer and the easy-to-bond layer to the interface between the polyester film and the easy-to-bond layer. Due to the non-uniformity of the penetration state, the stress transmission mode is also non-uniform, resulting in localized coagulation failure within the easy-to-bond layer. This localized coagulation failure within the easy-to-bond layer can become the starting point for defects such as cracks and fractures.

[0168] When evaluating flexural and puncture resistance, a localized external force is applied to polyester films and optical laminates with easily bondable layers. It is hypothesized that unexpected damage may occur because the external force is concentrated at more localized defect sites within the area where the force was applied. However, the present invention is not limited to this hypothesis.

[0169] By setting an upper limit on the average value of δq / δa, the molecular orientation can be made sufficiently uniform, and the generation of local defects can be effectively suppressed. By setting an upper limit on the average value of δq / δa of the polyester film with an easy-to-adhere layer that has been given appropriate mechanical strength by utilizing feature (A), excellent flexural strength and excellent puncture resistance can be stably imparted. That is, it is possible to effectively prevent the flexural strength and puncture resistance from becoming insufficient in a portion of the multiple test samples obtained from the evaluation object.

[0170] As mentioned above, from the viewpoint of more consistently ensuring excellent bending resistance and excellent puncture resistance, an upper limit is set for the average value of δq / δa. The average value of δq / δa can be below 1.80, below 1.79, below 1.74, below 1.71, below 1.68, below 1.65, below 1.61, below 1.59, below 1.56, or below 1.38.

[0171] Furthermore, for polyester films with an easy-to-adhere layer that meet characteristic (A), when the average value of δq / δa decreases, approximately 10% to 20% of samples obtained from the same polyester film with an easy-to-adhere layer, although not reaching the point of sample breakage, show test marks on the samples, indicating insufficient puncture resistance and flexural resistance. The detailed mechanism of this phenomenon is still unclear, but it is speculated to be due to the following:

[0172] It is believed that when the average value of δq / δa is extremely small, for example, when the average value of δq / δa is less than 1.125, the film quality of the easy-to-adhere layer is very homogeneous, and no phase separation occurs in the easy-to-adhere layer. When a certain external force is repeatedly applied to such a homogeneous easy-to-adhere layer, the external force is not dispersed within the polyester film with the easy-to-adhere layer, which is a combination of the homogeneous easy-to-adhere layer and the polyester film with characteristic (A), and the external force is repeatedly applied to a certain position of the polyester film with the easy-to-adhere layer. As a result, it is expected that by repeatedly bending the polyester film with the easy-to-adhere layer and the optical laminate at a certain position, although it will not lead to the breakage of the polyester film with the easy-to-adhere layer, tiny cracks will be generated in the easy-to-adhere layer, forming test marks as turbid areas.

[0173] 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, even if characteristic (A) is met, the puncture resistance will be insufficient. When the average value of δq / δa is extremely small, the film quality of the easy-to-adhere layer is very homogeneous. Due to this homogeneity, the impact force that should be evaluated by puncture resistance will not propagate and disperse along the surface direction within the polyester film with the easy-to-adhere layer, which is a combination of a homogeneous easy-to-adhere layer and a polyester film having characteristic (A), but will be concentrated at a very small location within the polyester film with the easy-to-adhere layer. As a result, even if characteristic (A) is met, although with low probability, the puncture resistance is expected to become insufficient.

[0174] By setting a lower limit on the average value of δq / δa, it is possible to prevent the easy-to-adhere layer from becoming overly homogeneous. By setting a lower limit on the average value of δq / δa of the polyester film with the easy-to-adhere layer, which has been endowed with appropriate mechanical strength using feature (A), excellent flexural strength and excellent puncture resistance can be stably imparted. That is, it is possible to effectively suppress insufficient flexural strength in a portion of a plurality of test samples obtained from the evaluation object.

[0175] As mentioned above, from the viewpoint of more consistently ensuring excellent bending resistance and excellent puncture resistance, a lower limit is set for the average value of δq / δa. The average value of δq / δa can be above 1.125, above 1.13, above 1.20, above 1.25, above 1.31, or above 1.33.

[0176] <Feature B1: Coefficient of variation of δq / δa>

[0177] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (B1).

[0178] Feature (B1): The coefficient of variation of δq / δa calculated based on 5 δq / δa values ​​is below 0.150.

[0179] In feature (B1), "δq / δa at 5 locations" refers to the "δq / δa at 5 locations" used when calculating the average value of δq / δa specified 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 units. The coefficient of variation specified in feature (B1) is the value obtained by dividing the standard deviation of δq / δa at 5 locations by the average value of δq / δa at 5 locations.

[0180] By setting an upper limit on the coefficient of variation of δq / δa, the viscoelasticity among the five measurement and evaluation areas of 2μm × 2μm can be homogenized. By keeping the coefficient of variation of δq / δa below 0.150, the viscoelasticity of the easy-to-bond layer can be further homogenized. This results in a more even distribution of stress applied to the polyester film with the easy-to-bond layer in the plane. Consequently, the initiation point of interlayer delamination is less likely to occur, further improving the adhesion between the easy-to-bond layer and the polyester film. Furthermore, the adhesion between the easy-to-bond layer and the functional layer in the optical laminate using this polyester film with the easy-to-bond layer can also be further improved. From the viewpoint of improving adhesion, the coefficient of variation of δq / δa can be below 0.150, below 0.143, below 0.130, below 0.110, or below 0.093.

[0181] If the coefficient of variation of δq / δa is too small, it is conceivable that the components of the functional layer will have difficulty penetrating into the easy-to-bond layer, thus failing to fully improve the adhesion between the easy-to-bond layer and the functional layer. From this perspective, the coefficient of variation of δq / δa can be above 0.010, above 0.025, above 0.040, or above 0.049.

[0182] The coefficient of variation of δq / δa can be above 0.010 and below 0.150, above 0.010 and below 0.143, above 0.010 and below 0.130, above 0.010 and below 0.110, or above 0.010 and below 0.090. The coefficient of variation of δq / δa can be above 0.025 and below 0.150, above 0.025 and below 0.143, above 0.025 and below 0.130, above 0.025 and below 0.110, or above 0.025 and below 0.090. The coefficient of variation of δq / δa can be above 0.040 and below 0.150, above 0.040 and below 0.143, above 0.040 and below 0.130, above 0.040 and below 0.110, or above 0.040 and below 0.090. The coefficient of variation of δq / δa can be above 0.049 and below 0.150, above 0.049 and below 0.143, above 0.049 and below 0.130, above 0.049 and below 0.110, or above 0.049 and below 0.090.

[0183] <Feature A1: nx-ny>

[0184] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A1).

[0185] Feature (A1): When the refractive index of the polyester film with the easy-to-adhesive layer in the slow axis direction in the plane of the polyester film with the easy-to-adhesive layer is defined as nx, and the refractive index in the direction orthogonal to the slow axis in the same plane is defined as ny, nx and ny satisfy the following relationship.

[0186] nx - ny ≤ 0.0300

[0187] By setting nx-ny to below 0.0300, rainbow spots caused by in-plane phase difference can be suppressed. nx-ny can be below 0.0300, below 0.0250, below 0.0240, or below 0.0230.

[0188] Unless otherwise specified, in this instruction manual, iris refers to the iris as seen with the naked eye.

[0189] If the nx-ny value of the polyester film with the easy-to-adhere layer is too small, it will be difficult to suppress black screen. From this point of view, nx-ny can be above 0.0050, above 0.0080, above 0.0100, above 0.0120, or above 0.0130. Black screen refers to the phenomenon that the entire surface darkens when light passes through polarizing elements and then the polyester film in sequence, as observed through polarizing sunglasses or other polarizing elements.

[0190] The nx-ny value of polyester film with an easy-to-adhere layer can be above 0.0050 and below 0.0300, above 0.0050 and below 0.0250, above 0.0050 and below 0.0240, or above 0.0050 and below 0.0230. The nx-ny value of polyester film with an easy-to-adhere layer can be above 0.0080 and below 0.0300, above 0.0080 and below 0.0250, above 0.0080 and below 0.0240, or above 0.0080 and below 0.0230. The nx-ny value of polyester film with an easy-to-adhere layer can be above 0.0100 and below 0.0300, above 0.0100 and below 0.0250, above 0.0100 and below 0.0240, or above 0.0100 and below 0.0230. The nx-ny value of polyester film with easy-to-adhere layer can be above 0.0120 and below 0.0300, above 0.0120 and below 0.0250, above 0.0120 and below 0.0240, or above 0.0120 and below 0.0230. The nx-ny value of polyester film with easy-to-adhere layer can be above 0.0130 and below 0.0300, above 0.0130 and below 0.0250, above 0.0130 and below 0.0240, or above 0.0130 and below 0.0230.

[0191] <Feature A2: In-plane phase difference Re>

[0192] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A2).

[0193] Feature (A2): The in-plane phase difference Re of the polyester film with the easy-to-adhere layer is less than 2000 nm.

[0194] The in-plane phase difference Re is a value obtained by "(nx-ny)×T[nm]", where T is the thickness of the polyester film with the easy-to-adhere layer [nm]. By setting an upper limit on the in-plane phase difference, iris spots can be suppressed. From this perspective, the in-plane phase difference of the polyester film with the easy-to-adhere layer can be below 2000nm, below 1600nm, below 1400nm, below 1200nm, below 1148nm, below 1100nm, below 1000nm, or below 950nm.

[0195] Iridescence can also be suppressed by adjusting the functional layer and the light source. Additionally, there are applications where iris distortion is not a primary concern. Therefore, the in-plane phase difference of polyester films is not limited to below 2000 nm and can also exceed 2000 nm.

[0196] By setting a lower limit on the in-plane phase difference of the polyester film with an easy-to-adhere layer, black screen can be suppressed. This is because polyester films with an average in-plane phase difference of less than 50 nm can hardly disturb linearly polarized light, allowing it to pass through directly. On the other hand, polyester films with an average in-plane phase difference of 50 nm or more will disturb linearly polarized light. From this perspective, the in-plane phase difference of the polyester film with the easy-to-adhere layer can be greater than 50 nm, greater than 100 nm, greater than 150 nm, greater than 200 nm, greater than 250 nm, greater than 300 nm, greater than 400 nm, greater than 450 nm, or greater than 497 nm.

[0197] The in-plane phase difference of the polyester film with the easy-to-adhere layer can be 50nm to 2000nm, 50nm to 1600nm, 50nm to 1400nm, 50nm to 1200nm, 50nm to 1148nm, 50nm to 1100nm, 50nm to 1000nm, or 50nm to 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can also be 100nm to 2000nm, 100nm to 1600nm, 100nm to 1400nm, 100nm to 1200nm, 100nm to 1148nm, 100nm to 1100nm, 100nm to 1000nm, or 100nm to 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can be between 150nm and 2000nm, between 150nm and 1600nm, between 150nm and 1400nm, between 150nm and 1200nm, between 150nm and 1148nm, between 150nm and 1100nm, between 150nm and 1000nm, or between 150nm and 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can also be between 200nm and 2000nm, between 200nm and 1600nm, between 200nm and 1400nm, between 200nm and 1200nm, between 200nm and 1148nm, between 200nm and 1100nm, between 200nm and 1000nm, or between 200nm and 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can be above 250nm and below 2000nm, above 250nm and below 1600nm, above 250nm and below 1400nm, above 250nm and below 1200nm, above 250nm and below 1148nm, above 250nm and below 1100nm, above 250nm and below 1000nm, or above 250nm and below 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can be above 300nm and below 2000nm, above 300nm and below 1600nm, above 300nm and below 1400nm, above 300nm and below 1200nm, above 300nm and below 1148nm, above 300nm and below 1100nm, above 300nm and below 1000nm, or above 300nm and below 950nm.The in-plane phase difference of the polyester film with the easy-to-adhere layer can be above 400nm and below 2000nm, above 400nm and below 1600nm, above 400nm and below 1400nm, above 400nm and below 1200nm, above 400nm and below 1148nm, above 400nm and below 1100nm, above 400nm and below 1000nm, or above 400nm and below 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can be above 450nm and below 2000nm, above 450nm and below 1600nm, above 450nm and below 1400nm, above 450nm and below 1200nm, above 450nm and below 1148nm, above 450nm and below 1100nm, above 450nm and below 1000nm, or above 450nm and below 950nm. The in-plane phase difference of the polyester film with the easy-to-adhere layer can be above 497nm and below 2000nm, above 497nm and below 1600nm, above 497nm and below 1400nm, above 497nm and below 1200nm, above 497nm and below 1148nm, above 497nm and below 1100nm, above 497nm and below 1000nm, or above 497nm and below 950nm.

[0198] <Feature A2a: In-plane phase difference Re>

[0199] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A2a).

[0200] Feature (A2a): The in-plane phase difference Re of the polyester film with the easy-to-adhere layer is above 1800nm ​​and below 2800nm.

[0201] According to characteristic (A2a), polyester films with easy-to-adhesive layers exhibit excellent transportability when the in-plane phase difference Re is adjusted to be between 1800 nm and 2800 nm. As demonstrated in the transport tests of Reference Examples A to E described later, the amount of change in transport speed varies depending on the in-plane phase difference Re of the polyester film with easy-to-adhesive layers. By setting the in-plane phase difference Re to between 1800 nm and 2800 nm, deviations in the transport speed of the polyester film with easy-to-adhesive layers can be suppressed, enabling stable transport of the polyester film with easy-to-adhesive layers at a constant speed. As a result, damage to the polyester film with easy-to-adhesive layers caused by deviations in transport speed can be suppressed.

[0202] The detailed reasons why transportability varies depending on the in-plane phase difference Re are not yet clear. However, it is speculated that by making the in-plane phase difference Re between 1800 nm and 2800 nm, the long strip of polyester film with an easy-to-adhere layer achieves a good balance between three-dimensional rigidity and hardness, resulting in stable transport speed. The present invention is not limited to this speculation.

[0203] Feature A3: Phase difference Rth in the thickness direction

[0204] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A3).

[0205] Feature (A3): The phase difference Rth in the thickness direction of the polyester film with the easy-to-adhere layer is greater than 2000nm.

[0206] The phase difference Rth in the thickness direction is obtained using the formula ((nx+ny) / 2-nz)×T[nm], where T is the thickness [nm] of the polyester film with the easy-to-adhere layer. By setting a lower limit for the phase difference Rth in the thickness direction, black screens can be suppressed not only when viewed from the front but also when viewed from a tilted angle. From this perspective, the phase difference Rth in the thickness direction of the polyester film with the easy-to-adhere layer can be above 2000nm, above 3000nm, above 4000nm, or above 5000nm.

[0207] In order to make Re / Rth fall within the range described later, the phase difference Rth in the thickness direction of the polyester film with the easy-to-adhere layer can be less than 15000 nm, less than 12000 nm, or less than 9000 nm.

[0208] The phase difference Rth in the thickness direction of the polyester film with an easy-to-adhere layer can be above 2000nm and below 15000nm, above 2000nm and below 12000nm, or above 2000nm and below 9000nm. The phase difference Rth in the thickness direction of the polyester film with an easy-to-adhere layer can be above 3000nm and below 15000nm, above 3000nm and below 12000nm, or above 3000nm and below 9000nm. The phase difference Rth in the thickness direction of the polyester film with an easy-to-adhere layer can be above 4000nm and below 15000nm, above 4000nm and below 12000nm, or above 4000nm and below 9000nm. The phase difference Rth in the thickness direction of the polyester film with an easy-to-adhere layer can be above 5000nm and below 15000nm, above 5000nm and below 12000nm, or above 5000nm and below 9000nm.

[0209] <Feature A4: Re / Rth>

[0210] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A4).

[0211] Feature (A4): Re / Rth is above 0.01 and below 0.20.

[0212] A low Re / Rth ratio implies that the polyester film exhibits near-uniform biaxial stretching. By setting an upper limit on Re / Rth, the mechanical strength of the polyester film with the easy-to-adhere layer can be improved. Furthermore, by setting an upper limit on Re / Rth, wrinkling of the polyester film with the easy-to-adhere layer under environmental changes can be suppressed, thus preventing adverse effects on visibility. From these perspectives, Re / Rth can be below 0.20, below 0.17, or below 0.15. To maximize the effect of achieving a Re / Rth within the specified range, the in-plane phase difference of the polyester film with the easy-to-adhere layer is preferably within the above-mentioned range.

[0213] If the Re / Rth ratio is too small, the orientation in the XY plane is high, while the orientation in the Z-axis direction is reduced, leading to a tendency to become brittle in the film thickness direction. Therefore, if the Re / Rth ratio is too small, the polyester film with the easy-to-adhere layer will break when it is applied to or peeled from the substrate. From these perspectives, the Re / Rth ratio of the polyester film is preferably 0.01 or higher, more preferably 0.03 or higher, more preferably 0.05 or higher, and even more preferably 0.06 or higher.

[0214] The Re / Rth of polyester film with an easy-to-adhesion layer can be 0.01 to 0.20, 0.01 to 0.17, or 0.01 to 0.15. The Re / Rth of polyester film with an easy-to-adhesion layer can be 0.03 to 0.20, 0.03 to 0.17, or 0.03 to 0.15. The Re / Rth of polyester film with an easy-to-adhesion layer can be 0.05 to 0.20, 0.05 to 0.17, or 0.05 to 0.15. The Re / Rth of polyester film with an easy-to-adhesion layer can be listed as 0.06 to 0.20, 0.06 to 0.17, or 0.06 to 0.15.

[0215] <Feature A5: Nz Coefficient>

[0216] In addition to features (A) and (B), polyester films with an easy-to-adhere layer may also have the following feature (A5).

[0217] Feature (A5): Nz coefficient is greater than 2.0.

[0218] The Nz coefficient is obtained by using "(Rth / Re) + 0.5". As mentioned above, "Rth" is the phase difference in the thickness direction of the polyester film with the easy-to-adhere layer. As mentioned above, "Re" is the in-plane phase difference of the polyester film with the easy-to-adhere layer.

[0219] The Nz coefficient decreases when the polyester film is uniaxially stretched or nearly uniaxially stretched. Nearly uniaxial stretching includes cases where the stretch ratios of the first and second axes are significantly different. In feature (A5), a lower limit is set for the Nz coefficient. A polyester film with an easy-to-adhere layer satisfying feature (A5) can be obtained by stretching in two orthogonal directions at a stretch ratio greater than a certain amount. That is, a polyester film with an easy-to-adhere layer having feature (A5) includes a biaxially oriented polyester film.

[0220] In this specification, "biaxial tension" refers to a coefficient of Nz greater than 2.0. In this specification, "uniaxial tension" refers to a coefficient of Nz less than 2.0.

[0221] Feature (B) specifies the numerical range of the average value of δq / δa. It is effective to ensure homogeneous molecular orientation of the polyester film by setting the average value of δq / δa below the upper limit specified in Feature (B).

[0222] For example, when using uniaxially stretched or near-uniaxially stretched polyester films, there are directions where the film is stretched at a large stretch ratio. Along this stretching direction, the molecular orientation of the polyester film is homogenized to some extent. However, along directions that are not parallel to this stretching direction, such as directions orthogonal to the stretching direction, the molecular orientation of the polyester film tends to become non-uniform. When the molecular orientation of the polyester film is non-uniform, the wettability of the coating liquid used to form the easy-to-adhere layer on the polyester film decreases, and the coating liquid is repelled on the polyester film. Due to the formation of pinholes in the coating liquid, the mechanical properties of the easy-to-adhere layer made by the coating liquid are non-uniform in plane, leading to defects. As a result, the average value of δq / δa increases.

[0223] For polyester films with an easy-to-adhesive layer that use uniaxially stretched or near-uniaxially stretched polyester films, it is not easy to stably and sufficiently reduce the average value of δq / δa. For polyester films with an easy-to-adhesive layer that do not have feature (A5), it is not easy to stably keep the average value of δq / δa below the upper limit specified in feature (B).

[0224] For a polyester film with an easy-to-adhesive layer that satisfies characteristic (A5), the in-plane birefringence (nx-ny) decreases. With a low in-plane birefringence, the molecular orientation of the polyester film becomes homogeneous in-plane. Regarding the quality and characteristics of the easy-to-adhesive layer formed by directly coating the coating liquid onto the polyester film, the thickness of the easy-to-adhesive layer is often thin, sometimes less than 1 μm, and is easily affected by the polyester film serving as the substrate. By coating the easy-to-adhesive layer onto a polyester film with homogeneous in-plane molecular orientation, the easy-to-adhesive layer can be made homogeneous. Furthermore, the wettability of the coating liquid used to form the easy-to-adhesive layer on a polyester film with homogeneous in-plane molecular orientation can become good throughout the entire area. From this perspective, a homogeneous easy-to-adhesive layer can also be formed. As a result, the average value of δq / δa can be stably set below the upper limit specified in characteristic (B), suppressing changes in the mechanical properties and viscoelasticity within the easy-to-adhesive layer.

[0225] Furthermore, feature (A5) not only contributes to the formation of a homogeneous, easily bondable layer as described above, but also homogenizes the properties of the polyester film with the easily bondable layer. The transmittance of a polyester film with high in-plane birefringence (nx-ny) varies depending on the direction of light vibration. With a polyester film with an easily bondable layer satisfying feature (A5), transmittance can be kept constant regardless of direction. With a polyester film with an easily bondable layer satisfying feature (A5), the necessity for precise positioning considering both the slow axis and the transmission axis can be reduced. By satisfying feature (A5), the mechanical properties of the polyester film with the easily bondable layer can be homogenized.

[0226] <Thickness of polyester film with easy-to-adhere layer>

[0227] A lower limit can be set for the thickness of the polyester film with the easy-to-adhere layer. By setting a lower limit for the thickness of the polyester film with the easy-to-adhere layer, high mechanical strength can be imparted to the polyester film with the easy-to-adhere layer. High puncture resistance can also be imparted to the polyester film with the easy-to-adhere layer. From this point of view, the thickness of the polyester film with the easy-to-adhere layer can 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, the second surface 15b (refer to) of the optical laminate becomes the side opposite to the functional layer. Figure 3 When in contact with other components, stress is not easily transmitted to the interface between the polyester film and the easy-to-adhere layer. Therefore, the polyester film and the easy-to-adhere layer can be maintained in a stable, tight bond.

[0228] An upper limit can be set for the thickness of the polyester film with the easy-to-adhere layer. By setting an upper limit for the thickness of the polyester film with the easy-to-adhere layer, the in-plane phase difference Re can be reduced, thereby improving flexibility and bendability. From these perspectives, the thickness of the polyester film with the easy-to-adhere layer can be less than 75 μm, less than 60 μm, less than 55 μm, or less than 50 μm.

[0229] The thickness of the polyester film with the easy-to-adhere layer can be 10μm to 75μm, 10μm to 60μm, 10μm to 55μm, or 10μm to 50μm. The thickness of the polyester film with the easy-to-adhere layer can be 21μm to 75μm, 21μm to 60μm, 21μm to 55μm, or 21μm to 50μm. The thickness of the polyester film with the easy-to-adhere layer can be 25μm to 75μm, 25μm to 60μm, 25μm to 55μm, or 25μm to 50μm. The thickness of the polyester film with the easy-to-adhere layer can be 30μm to 75μm, 30μm to 60μm, 30μm to 55μm, or 30μm to 50μm.

[0230] The thickness of the polyester film with the easy-to-bond layer but without the functional layer is determined using measurements taken at 20 measurement sites using a film thickness gauge. The largest, second-largest, smallest, and second-smallest measurements are excluded from the 20 sites, and the average of the remaining 16 measurements is taken as the thickness of the polyester film with the easy-to-bond layer. The film thickness gauge can be the Nikon brand "Digimicro". The Nikon brand "Digimicro" uses "MS-5C" + "MH-15M" as the stage and main body, and the counter can be "TC-101A".

[0231] The thickness of the polyester film with an easy-to-adhesive layer assembled in an optical laminate can be determined using a scanning transmission electron microscope (STEM). The cross-section of the polyester film with the easy-to-adhesive layer, which is the object of evaluation, and the optical laminate containing the polyester film with the easy-to-adhesive layer are observed using a scanning transmission electron microscope. The thickness of the polyester film with the easy-to-adhesive layer is measured based on the observation images from the scanning transmission electron microscope. To enable cross-sectional observation, a measurement sample exposing the cross-section of the polyester film with the easy-to-adhesive layer is prepared. A microtome is used for sample preparation. A microtome manufactured by Leica is used. An example of a scanning electron microscope is the "Model: S4800" manufactured by Hitachi High-Tech Co., Ltd.

[0232] The thickness of the object was measured at seven locations using cross-sectional observation with a scanning electron microscope. The largest and smallest values ​​were excluded from the seven measurements, and the average of the remaining five values ​​was taken as the thickness of the polyester film with the easy-to-adhere layer. The seven measurement locations were set at 10 μm intervals along a straight line.

[0233] Before starting the thickness measurement, the sample was placed in the measurement environment for 16 hours. The measurement environment was set at a temperature of 23℃±2℃ and a relative humidity of 50%±5%.

[0234] To obtain the values ​​of the in-plane phase difference Re and the phase difference Rth in the thickness direction, the thickness of the polyester film with the easy-to-adhere layer is required. The thickness of the polyester film with the easy-to-adhere layer, determined by the above method, is used to determine the values ​​of the in-plane phase difference Re and the phase difference Rth in the thickness direction.

[0235] <Transmittance and Haze of Polyester Film with Easy-to-Adhesive Layer>

[0236] The haze transmittance of polyester film with an easy-to-adhesive layer can be below 3.0%, below 2.0%, or below 1.0%. There is no specific lower limit for the haze transmittance of polyester film with an easy-to-adhesive layer. The haze transmittance of polyester film with an easy-to-adhesive layer can be 0% or greater than 0%.

[0237] A D65 light source was used for measuring transmitted haze. Before measuring transmitted haze, the D65 light source was lit for 15 minutes to allow its output to stabilize. The angle of incidence on the sample was set to 0°. The ambient temperature for measuring transmitted haze was set to 23℃±2℃ and relative humidity to 50%±5%. The sample was allowed to settle in the ambient temperature for 16 hours before measurement. Other measurement conditions followed JIS K7136:2000. A haze meter (model: HM-150) manufactured by Murakami Color Technology Research Institute can be used for measuring transmitted haze.

[0238] When measuring the haze transmittance of a polyester film with an easy-to-adhere layer, the incident surface is set to be closer to the main surface of the polyester film than the easy-to-adhere layer. As an example, in... Figure 1 In the example shown, the incident surface for measuring the transmitted haze is set as the second surface 15b.

[0239] The haze transmittance is set as the arithmetic mean of five measurements. These five measurements are taken at five locations on the object being measured. These five locations are spaced at least 10 mm apart.

[0240] Total light transmittance of polyester film with easy-to-adhere layer

[0241] The total light transmittance of polyester film with an easy-to-adhesive layer can be above 80%, above 85%, or above 90%. There is no specific upper limit to the total light transmittance of polyester film with an easy-to-adhesive layer. The total light transmittance of polyester film with an easy-to-adhesive layer can be below 100% or less than 100%.

[0242] A D65 light source was used for the determination of total light transmittance. Before measuring the total light transmittance of the polyester film with the easy-to-adhere layer, the D65 light source was lit for 15 minutes to allow the output to stabilize. The angle of incidence on the sample was set to 0° for the total light transmittance measurement. The ambient temperature for the total light transmittance measurement was set to 23℃±2℃ and 50%±5% relative humidity. The sample was allowed to settle in the ambient temperature for 16 hours before the measurement began. Other measurement conditions for the total light transmittance measurement followed JIS K7361-1:1997. A haze meter (model: HM-150) manufactured by Murakami Color Technology Research Institute can be used for the determination of total light transmittance.

[0243] When measuring the total light transmittance of a polyester film with an easy-to-adhere layer, the incident surface is set to be closer to the main surface of the polyester film than the easy-to-adhere layer. As an example, in... Figure 1 In the example shown, the incident surface for measuring the total light transmittance is set as the second surface 15b.

[0244] The total light transmittance was set as the arithmetic mean of five measurements. These five measurements were taken at five locations on the object being evaluated, spaced at least 10 mm apart.

[0245] <Ultraviolet transmittance>

[0246] The spectral transmittance of a polyester film with an easy-to-adhere layer at a wavelength of 380 nm can be below 20% or below 10%. There is no specific lower limit to the spectral transmittance of a polyester film with an easy-to-adhere layer at a wavelength of 380 nm. The spectral transmittance of a polyester film with an easy-to-adhere layer at a wavelength of 380 nm can be 0% or greater than 0%.

[0247] The spectral transmittance of the polyester film with an easy-to-adhere layer at a wavelength of 380 nm was set to the value determined according to JIS Z 8722:2009. The incident angle of the sample was set to 0° when measuring spectral transmittance. The irradiation and light reception geometry for measuring spectral transmittance was set to the geometry f specified in JIS Z8722:2009, including the condition for the positive transmission direction (0°: di). Before measuring spectral transmittance, the light source was lit for 15 minutes to allow the output to stabilize. The measurement environment for spectral transmittance was set to a temperature of 23℃±2℃ and a relative humidity of 50%±5%. The sample was placed in the measurement environment for 16 hours before the measurement began. Other measurement conditions for spectral transmittance were in accordance with JIS Z8722:2009.

[0248] When measuring the spectral transmittance of a polyester film with an easy-to-adhere layer, the incident plane is set to be closer to the main surface of the polyester film than the easy-to-adhere layer. As an example, in... Figure 1 In the example shown, the incident surface for measuring spectral transmittance is set as the second surface 15b.

[0249] The spectral transmittance was set as the arithmetic mean of five measurements. These five measurements were taken at five locations on the object being evaluated, spaced at least 10 mm apart.

[0250] <<Layer Composition of Polyester Film with Easy-to-Adhesive Layer>>

[0251] Polyester film with easy-to-adhesion layer consists of polyester film and easy-to-adhesion layer.

[0252] Polyester film with an easy-to-adhesion layer can consist of a single layer of polyester film. In other words, polyester film with an easy-to-adhesion layer can consist of a single layer of polyester film.

[0253] Polyester film with an easy-to-adhesive layer may also comprise multiple polyester films. The polyester film contained in a polyester film with an easy-to-adhesive layer may consist of multiple layers.

[0254] A polyester film with an easy-to-adhere layer may contain a single easy-to-adhere layer. A polyester film with an easy-to-adhere layer may also contain multiple easy-to-adhere layers. Multiple easy-to-adhere layers may be laminated on one side of the polyester film with an easy-to-adhere layer. Multiple easy-to-adhere layers may also be laminated on one side and another side of the polyester film with an easy-to-adhere layer.

[0255] As described above, regardless of the layer composition of the polyester film with the easy-to-adhere layer, the planar orientation degree ΔP is measured using the polyester film with the easy-to-adhere layer as the object. Regardless of the layer composition of the polyester film with the easy-to-adhere layer, the δq / δa measurement using atomic force microscopy is not performed on the easy-to-adhere layer peeled off from the polyester film, but rather on the surface of the easy-to-adhere layer within the polyester film. For example, if multiple easy-to-adhere layers are deposited on one surface of the polyester film, the δq / δa measurement using atomic force microscopy is performed on the surface of the easy-to-adhere layer constituting one surface of the polyester film with the easy-to-adhere layer.

[0256] <<Polyester Film>>

[0257] The polyester film is a layer that supports the easy-to-adhere layer. The polyester film is also a layer that supports the functional layers on top of the easy-to-adhere layer. The polyester film possesses the aforementioned physical properties and structure that impart the easy-to-adhere layer to the polyester film. Similar to the polyester film with the easy-to-adhere layer, the polyester film may also have characteristics (A), (A1), (A2), (A3), and (A4). Regarding haze transmission, total light transmittance, and ultraviolet transmittance, the polyester film may possess the same characteristics as the aforementioned polyester film with the easy-to-adhere layer.

[0258] <Thickness of polyester film>

[0259] To ensure good mechanical strength, the thickness of the polyester film can be 10 μm or more, 21 μm or more, 25 μm or more, or 30 μm or more. By making the polyester film thickness 10 μm or more, when the surface of the polyester film with the easy-to-adhere layer, which is closer to the functional layer of the optical laminate, comes into contact with other components and generates stress, the stress is less likely to be transmitted to the interface between the polyester film and the easy-to-adhere layer.

[0260] To reduce the in-plane phase difference of the polyester film with the easy-to-adhere layer and to ensure good bending resistance, an upper limit can be set on the thickness of the polyester film. The thickness of the polyester film can be less than 75 μm, less than 60 μm, less than 55 μm, or less than 50 μm.

[0261] The thickness of the polyester film can be between 10μm and 75μm, between 10μm and 60μm, between 10μm and 55μm, or between 10μm and 50μm. The thickness of the polyester film can also be between 21μm and 75μm, between 21μm and 60μm, between 21μm and 55μm, or between 21μm and 50μm. The thickness of the polyester film can also be between 25μm and 75μm, between 25μm and 60μm, between 25μm and 55μm, or between 25μm and 50μm. Finally, the thickness of the polyester film can be between 30μm and 75μm, between 30μm and 60μm, between 30μm and 55μm, or between 30μm and 50μm.

[0262] <Raw Materials for Polyester Film>

[0263] Examples of polyesters constituting polyester films 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 mixed resins formed by mixing one or more homopolymers and one or more copolymers.

[0264] Polyester films may contain additives. Examples of additives include UV absorbers, slippery particles such as inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, lightfast agents, flame retardants, heat stabilizers, antioxidants, antigelling agents, and surfactants.

[0265] The raw materials for polyester film can be newly synthesized raw materials, naturally derived raw materials, recycled raw materials, or a mixture of two or more of them.

[0266] Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylsulfone carboxylic acid, anthracene dicarboxylic 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-methyl adipic acid, trimethyl adipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, octanoic acid, dodecanedicarboxylic acid, etc.

[0267] Examples of diols include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanediethanol, 1,4-cyclohexanediethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0268] Polyester films can contain polyethylene terephthalate. Polyethylene terephthalate can impart high mechanical strength to polyester films.

[0269] Examples of polymerization methods for polyethylene terephthalate include: direct polymerization, in which terephthalic acid reacts directly with ethylene glycol and, as needed, other dicarboxylic acid components and glycol components; and transesterification, in which dimethyl terephthalate undergoes a transesterification reaction with ethylene glycol; etc. In the transesterification method, the dimethyl terephthalate may contain methyl esters of other dicarboxylic acids, as needed. Similarly, in the transesterification method, the ethylene glycol may contain other glycol components, as needed.

[0270] The intrinsic viscosity of polyethylene terephthalate (PET) can be between 0.45 and 0.70. Maintaining an intrinsic viscosity of 0.45 or higher improves the tear resistance of polyester films with easily bondable layers. Maintaining an intrinsic viscosity of 0.70 or lower suppresses pressure rise and improves filtration accuracy.

[0271] <Layer Composition of Polyester Film>

[0272] Polyester films can have a single-layer structure. Polyester films can also have a multi-layer structure. That is, a polyester film can contain a single layer. A polyester film can also contain multiple layers.

[0273] Single-layer structures excel in their ease of stretch control. Therefore, the easy-to-bond layer of a single-layer structure does not reduce the stretch ratio in the flow and width directions, and makes the stretch ratios in both directions similar, thereby increasing the planar orientation degree ΔP of the polyester film with the easy-to-bond layer. Therefore, a single-layer structure with easily controllable stretch is preferred in terms of increasing the planar orientation degree ΔP of the polyester film with the easy-to-bond layer.

[0274] On the other hand, multilayer polyester films are preferred in that they readily impart the effects that can be achieved by changing the composition of each layer. For example, a laminated polyester film consisting of at least three layers, formed by co-extrusion, can be used for a polyester film with an easy-to-adhere layer. In this example, by using 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.

[0275] (Stretching of polyester film)

[0276] To achieve the planar orientation degree ΔP specified in feature (A) above, the stretch ratios in the flow direction and width direction can be kept constant, and the stretch ratios in both directions can be made close. The polyester film can be a stretched film or a biaxially oriented film.

[0277] -Gradual bidirectional stretching-

[0278] In the progressive biaxial stretching process, after the cast film is stretched along the flow direction, the polyester film is stretched in the width direction.

[0279] Stretching in the flow direction is typically achieved using the difference in circumferential speed between a pair of stretching rollers. Stretching in the flow direction can be performed in one stage or in multiple stages using multiple stretching rollers. To suppress excessive deviations in optical properties such as planar orientation ΔP and in-plane phase difference, multiple pinch rollers can be brought close to the stretching rollers. The stretching ratio in the flow direction can be between 2 and 15 times, and to suppress excessive deviations in optical properties such as planar orientation ΔP and in-plane phase difference, it can be between 2 and 7 times, between 3 and 5 times, or between 3 and 4 times.

[0280] To suppress excessive deviations in physical properties such as planar orientation ΔP and in-plane phase difference, the stretching temperature can be set above the glass transition temperature of the resin but below it +100°C. The stretching temperature for PET film can be above 70°C and below 120°C, above 80°C and below 110°C, or above 95°C and below 110°C.

[0281] Regarding stretching temperature, if the polyester film is rapidly heated to shorten the stretching range at low temperatures, the average in-plane phase difference tends to decrease. On the other hand, if the polyester film is slowly heated to extend the stretching range at low temperatures, the orientation becomes higher, and the average in-plane phase difference tends to increase.

[0282] Layers with properties such as slip resistance and antistatic properties can be formed on a polyester film stretched along the flow direction by online or offline coating. In this specification, layers formed by online or offline coating are not counted as part of the total number of layers constituting the polyester film.

[0283] For stretching in the width direction, a tenter frame method is typically used. In this stretching method, the polyester film is fed while being held at both ends by clamps, stretching the polyester film along the width direction. The stretching ratio in the width direction can be more than 2 times and less than 15 times. From the viewpoint of suppressing excessive deviations in properties such as the planar orientation degree ΔP and in-plane phase difference of the polyester film with the easily adhesive layer, the stretching ratio in the width direction can be more than 2 times and less than 7 times, more than 3 times and less than 6 times, or more than 4 times and less than 5 times. It is also possible to make the stretching ratio in the width direction higher than the stretching ratio in the flow direction.

[0284] It is possible to achieve an Nz coefficient greater than 2.0 while simultaneously making one of the stretch ratios in the flow direction and the width direction higher than the other. Alternatively, the stretch ratios in the flow direction and the width direction can be made to the same degree, resulting in an Nz coefficient greater than 2.0. Based on these examples, the molecular orientation of the polyester film becomes homogeneous. Polyester films with uniform molecular orientation exhibit excellent coating adaptability. With polyester films of uniform molecular orientation, it is possible to suppress large in-plane variations in the viscoelasticity of the easily bondable layer formed on the polyester film. From the viewpoint of adjusting the average value of δq / δa to the numerical range specified in feature (B), the stretch ratios in the flow direction and the width direction can be adjusted to achieve an Nz coefficient greater than 2.0.

[0285] The stretching temperature can be above the glass transition temperature of the resin and below the glass transition temperature +120°C. The stretching temperature can increase from upstream to downstream of the polyester film. The difference between the upstream and downstream stretching temperatures can be above 20°C, above 30°C, above 35°C, or above 40°C. When stretching PET film, the stretching temperature of the first stage can be above 80°C and below 120°C, above 90°C and below 110°C, or above 95°C and below 105°C.

[0286] To impart planarity and dimensional stability to polyester films with easily bondable layers, the progressively biaxially stretched polyester film can be heat-treated in a tenter frame at a temperature above the stretching temperature but below the melting point. In the case of PET film, heat curing can be performed in a range of 150°C to 255°C, or in a range of 200°C to 250°C. To suppress excessive deviations in properties such as planar orientation ΔP and in-plane phase difference, an additional stretching of 1% to 10% can be performed during the first half of the heat treatment.

[0287] The polyester film can be wound up after heat treatment and subsequent slow cooling to room temperature. Depending on the needs, a relaxation treatment can be applied to the polyester film during heat treatment or slow cooling. To suppress excessive deviations in properties such as planar orientation ΔP and in-plane phase difference, the relaxation rate during heat treatment can be 0.5% to 5%, 0.5% to 3%, 0.8% to 2.5%, or 1% to 2%. Similarly, to suppress excessive deviations in properties such as planar orientation ΔP and in-plane phase difference, the relaxation rate during slow cooling can be 0.5% to 3%, 0.5% to 2%, 0.5% to 1.5%, or 0.5% to 1.0%. To ensure good planarity, the slow cooling temperature can be 80℃ to 150℃, 90℃ to 130℃, 100℃ to 130℃, or 100℃ to 120℃.

[0288] The conveying speed during the manufacturing of stretched polyester film can be between 100 m / s and 300 m / s.

[0289] -Synchronous biaxial stretching-

[0290] In synchronous biaxial stretching, the cast film is fed into a synchronous twin-screw tenter, and while the two ends of the polyester film are held by clamps, it is conveyed, and the polyester film is stretched synchronously and / or in stages in the flow direction and width direction. Examples of synchronous biaxial stretching machines include pantograph type, screw type, drive motor type, and linear motor type. Depending on the drive motor type or linear motor type, the stretch ratio can be arbitrarily changed, and relaxation processing can be performed in any location.

[0291] The area ratio of simultaneous biaxial stretching can be 6 to 50 times. From the viewpoint of suppressing excessive deviations in properties such as surface orientation degree ΔP and in-plane phase difference, the area ratio can 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 ratios can be achieved while keeping the stretching ratios in the flow direction and the width direction at 2 to 15 times. In the case of simultaneous biaxial stretching, in order to suppress in-plane orientation difference, the stretching ratios in the flow direction and the width direction can be approximately the same, while also keeping the stretching speeds in the flow direction and the width direction approximately the same.

[0292] To suppress excessive deviations in physical properties such as planar orientation ΔP and in-plane phase difference, the stretching temperature for simultaneous biaxial stretching can be set above the glass transition temperature of the resin but below it +120°C. The stretching temperature for simultaneous biaxial stretching of PET film can be above 80°C and below 160°C, above 90°C and below 150°C, or above 100°C and below 140°C.

[0293] To impart planarity and dimensional stability to the polyester film with the easy-to-adhere layer, the synchronously biaxially stretched polyester film can be further heat-treated in the heat-fixing chamber within the tenter frame at a temperature above the stretching temperature but below the melting point. The heat treatment conditions for the synchronously biaxially stretched polyester can be the same as those for the progressively biaxially stretched polyester described above.

[0294] <<Easy-adhesive layer>>

[0295] The polyester film with an easy-to-adhesive layer in this embodiment includes an easy-to-adhesive layer. Furthermore, in the polyester film with an easy-to-adhesive layer in this embodiment, by making the average value of δq / δa on the surface of the easy-to-adhesive layer between 1.125 and 1.80, the adhesion between the polyester film and the easy-to-adhesive layer can be strengthened. Additionally, by making the average value of δq / δa on the surface of the easy-to-adhesive layer between 1.125 and 1.80, the initiation point of defects in the polyester film with the easy-to-adhesive layer is less likely to occur, and the mechanical strength can be stabilized. By ensuring such stability while further satisfying characteristic (A), puncture resistance and flexural resistance can be steadily improved. The easy-to-adhesive layer has the aforementioned physical properties and structure to impart the above-mentioned physical properties and structure to the polyester film with the easy-to-adhesive layer.

[0296] The resin constituting the easy-bonding layer is not particularly limited. Examples of resins constituting the easy-bonding layer include thermoplastic resins and thermosetting resins such as polyester resins, polyurethane resins, and acrylic resins; thermoplastic resins are also an example. Examples of thermoplastic resins include polyester resins, polyurethane resins, and resins containing both polyester and polyurethane components. Using polyester resins, polyurethane resins, and resins containing both polyester and polyurethane components, it is possible to reduce the refractive index difference between the polyester film and the easy-bonding layer, as well as the refractive index difference between the easy-bonding layer and the uneven layer.

[0297] Polyurethane components can help improve adhesion. However, polyurethane components are not conducive to enhancing coating strength. From this perspective, both polyester and polyurethane components can be included. However, if the polyurethane component is excessive relative to the polyester component, phase separation is likely to occur. Therefore, the average value and coefficient of variation of δq / δa tend to increase. Furthermore, because polyurethane components are soft, if there is an excessive amount of polyurethane, the average value and coefficient of variation of δq / δa tend to increase due to differences in in-plane crosslinking density. From this perspective, in resins containing both polyester and polyurethane components, the mass ratio of polyester to polyurethane can be 95:5 to 60:40, or 90:10 to 60:40.

[0298] The number average molecular weight of the resin constituting the easy-to-adhere layer can be 10,000 or more, or 15,000 or more. Alternatively, the number average molecular weight of the resin constituting the easy-to-adhere layer can be less than 100,000, or less than 60,000. By ensuring that the number average molecular weight of the resin constituting the easy-to-adhere layer is within the above range, aggregation and damage to the easy-to-adhere layer can be suppressed.

[0299] The glass transition temperature of the resin constituting the easy-to-bond layer can be above 30°C, above 50°C, or above 70°C. The glass transition temperature of the resin constituting the easy-to-bond layer can be below 120°C, below 110°C, or below 90°C.

[0300] By setting the glass transition temperature of the resin constituting the easy-to-bond layer to 30°C or higher, it is possible to suppress the internal stress generated by the easy-to-bond layer due to flow caused by heat during the process. Consequently, the average value of δq / δa and the coefficient of variation of δq / δa can be easily adjusted to the aforementioned range. Examples of heat generated during the process include the heat generated during the drying process of the coating liquid for the functional layer and the heat generated when the optical laminate is bonded to the polarizing element.

[0301] By setting the glass transition temperature of the resin constituting the easy-to-bond layer to below 120°C, stress caused by the difference in thermal behavior between the easy-to-bond layer and the polyester film due to heat generated during the process can be suppressed. This suppresses cracking and other issues in the easy-to-bond layer caused by the aforementioned stress. Therefore, by setting the glass transition temperature of the resin constituting the easy-to-bond layer to below 120°C, the average value of δq / δa and the coefficient of variation of δq / δa can be easily adjusted to the aforementioned numerical range.

[0302] The easy-to-bond layer may contain additives. Examples of additives include refractive index modifiers, dyes, pigments, leveling agents, UV absorbers, antioxidants, and light stabilizers; and crosslinking agents used to adjust hardness or viscosity. Examples of crosslinking agents include non-yellowing XDI-based, IPDI-based, and HDI-based isocyanates, and ionizing radiation-cured multifunctional monomers.

[0303] The easy-to-adhesive layer can be formed by an online coating method during the polyester film fabrication process. Alternatively, it can be formed by an offline coating method after the polyester film has been fabricated.

[0304] In both online and offline coating methods, an easy-to-adhesive coating liquid containing components constituting the easy-to-adhesive layer can be used. For example, an easy-to-adhesive layer can be formed by coating an easy-to-adhesive layer coating liquid onto a polyester film using a general coating method and then drying it. In this case, the drying time can be 120 seconds or less, or 90 seconds or less. By keeping the drying time to 120 seconds or less, phase separation of the components constituting the easy-to-adhesive layer can be suppressed. Therefore, the average value of δq / δa and the coefficient of variation of δq / δa can be easily adjusted to the aforementioned range. If the drying time is too short, the coating surface will be rough, and the optical properties will be reduced. From these points of view, the drying time can be 15 seconds or more, or 20 seconds or more. The drying time can be adjusted by the drying temperature and the drying air velocity.

[0305] The direction of the drying air can be opposite to the direction of the polyester film transport. By making the direction of the drying air opposite to the direction of the polyester film transport, the drying time of the coating liquid for the easy-to-adhere layer can be significantly shortened without excessively increasing the drying temperature.

[0306] The drying temperature of the coating liquid for the easy-to-adhesive layer can be between 50°C and 200°C, or between 60°C and 150°C. By setting the drying temperature to 50°C or higher, the drying time of the coating liquid for the easy-to-adhesive layer can be shortened, thereby suppressing phase separation of the components constituting the easy-to-adhesive layer. By setting the drying temperature to 200°C or lower, the thermal decomposition of the components constituting the easy-to-adhesive layer can be suppressed.

[0307] The coating liquid for the easy-to-adhesive layer may contain a solvent. The solvent dissolves the components constituting the easy-to-adhesive layer within the coating liquid. The viscosity of the coating liquid can be adjusted by using a solvent that disperses the components constituting the easy-to-adhesive layer within it.

[0308] 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; carbon halogens such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; alcohols such as isopropanol, butanol, and cyclohexanol; cellosols such as methyl cellosol and ethyl cellosol; glycol ethers such as propylene glycol monomethyl ether acetate; acetic acid cellosols; sulfoxides such as dimethyl sulfoxide; and amides such as dimethylformamide and dimethylacetamide. The coating liquid for the easy-to-adhere layer may contain one solvent or two or more of the listed solvents.

[0309] If the drying time of the solvent in the coating solution for the easy-to-adhere layer is too long, the components constituting the easy-to-adhere layer are prone to phase separation. Therefore, the solvent in the coating solution for the easy-to-adhere layer can include solvents with a fast evaporation rate.

[0310] On the other hand, if the drying time of the solvent in the coating solution for the easy-to-adhere layer is too short, the surface of the coating film is prone to becoming rough. Therefore, the coating solution for the easy-to-adhere layer can contain solvents with extremely fast evaporation rates and solvents with moderately fast evaporation rates.

[0311] In this specification, a solvent with an extremely fast evaporation rate refers to a solvent whose evaporation rate is 280 or higher when the evaporation rate of butyl acetate is set to 100. Conversely, a solvent with a moderately fast evaporation rate refers to a solvent whose evaporation rate is 150 or higher and less than 280 when the evaporation rate of butyl acetate is set to 100.

[0312] Solvents with extremely fast evaporation rates can be between 320 and 430 °C, or between 340 and 400 °C. Examples of solvents with extremely fast evaporation rates include methyl ethyl ketone (MEK) with an evaporation rate of 370 °C and n-heptane with an evaporation rate of 362 °C.

[0313] Solvents with a moderately fast evaporation rate can have an evaporation rate of 170 to 250 or 180 to 220. Examples of solvents with a moderately fast evaporation rate include toluene with an evaporation rate of 200 and propyl acetate with an evaporation rate of 214.

[0314] In the solvent of the coating liquid for easy-to-adhere layers, the mass ratio of a solvent with an extremely fast evaporation rate to a solvent with a moderately fast evaporation rate can be 50:50 to 90:10, or 70:30 to 85:15.

[0315] From the perspective of suppressing phase separation in the coating liquid for easy-to-adhesive layers, the solid content concentration of the coating liquid for easy-to-adhesive layers can be 2% by mass or more, or 4% by mass or more. The solid content concentration of the coating liquid for easy-to-adhesive layers can be 30% by mass or less, or 10% by mass or less. The solid content concentration of the coating liquid for easy-to-adhesive layers can be adjusted by the solvent content.

[0316] There are no particular limitations on the composition of the coating liquid for the easy-to-adhesive layer. The coating liquid for the easy-to-adhesive layer can be solvent-based. Compared with water-based coating liquids for the easy-to-adhesive layer, solvent-based coating liquids for the easy-to-adhesive layer can improve the adhesion between the easy-to-adhesive layer and the polyester film after the damp heat resistance test.

[0317] It is believed that water-based easy-to-adhesive coating solutions can reduce environmental impact. However, water-based easy-to-adhesive coating solutions require high drying temperatures, and consequently, prolonged high-temperature drying times. Therefore, it cannot be said that water-based easy-to-adhesive coating solutions can help reduce environmental impact. Furthermore, compared to solvent-based easy-to-adhesive coating solutions, water-based solutions reduce processing efficiency during mass production.

[0318] For polyester films with an easy-to-adhere layer used in display devices, PVA resin can be added to the easy-to-adhere layer to improve adhesion to polarizing elements. PVA resin can be used as a main material for polarizing elements. POVAL manufactured by KURARAY is known as a raw material for polarizing elements. An example of POVAL manufactured by KURARAY is the product name "PVA28-98" (formerly "PVA-117"). PVA28-98 (formerly PVA-117) has a degree of polymerization of approximately 1700 and a molecular weight of 30,000 to 100,000.

[0319] The PVA resin added to the easy-to-adhere layer makes the coating liquid for the easy-to-adhere layer water-based. As a result, the adhesion between the easy-to-adhere layer and the polyester film is reduced by adding PVA resin to the easy-to-adhere layer.

[0320] The dry coating amount of the easy-to-adhere layer can be 0.05 g / m². 2 Above 0.75g / m2 The thickness of the easy-to-bond layer is not particularly limited. It can be 10nm to 600nm, 20nm to 300nm, or 50nm to 200nm. From the perspective of suppressing interference fringes, the thickness of the easy-to-bond layer can be made thinner.

[0321] The thicknesses of the polyester film with an easy-to-adhesive layer and the various layers contained in the optical laminate, such as the thicknesses of the easy-to-adhesive layer and the functional layer, are measured in the same manner as the method described above for measuring the thickness of the polyester film with an easy-to-adhesive layer assembled in the optical laminate. That is, the cross-section of the polyester film with an easy-to-adhesive layer and the optical laminate is observed using a scanning transmission electron microscope, and the thickness of the layer to be measured is determined based on the observation image based on the scanning transmission electron microscope. To enable cross-sectional observation, a measurement sample exposing the cross-section of the layer to be measured is prepared. A microtome is used in the preparation of the sample. An example of a microtome is a microtome manufactured by Leica. An example of a scanning electron microscope is the "Model: S4800" manufactured by Hitachi High-Tech Co., Ltd.

[0322] The thickness of the layer under test was measured at 20 sites using cross-sectional observation with a scanning electron microscope. The largest, second-largest, smallest, and second-smallest values ​​were excluded from the 20 measurements, and the average of the remaining 16 measurements was taken as the thickness of the layer under test. The 20 measurement sites were set at 10 μm intervals along a straight line.

[0323] <<Size, shape, etc. of polyester film with easy-to-adhere layer>>

[0324] Polyester film with an easy-to-bond layer can be cut into individual sheets of a specified size. There is no particular limitation on the size of the individual sheets, but the maximum diameter is approximately 2 inches to 500 inches. "Maximum diameter" refers to the maximum length that can be connected between any two points of the polyester film with the easy-to-bond layer. For example, if the polyester film with the easy-to-bond layer is rectangular, the diagonal of the rectangle is the maximum diameter. If the polyester film with the easy-to-bond layer is circular, the diameter of the circle is the maximum diameter.

[0325] The shape of the polyester film with the easy-to-adhesive layer is not particularly limited. Examples of shapes for polyester films with the easy-to-adhesive layer include polygons such as triangles, quadrilaterals, and pentagons, circles, and random amorphous shapes. When the polyester film with the easy-to-adhesive layer is quadrilateral, the aspect ratio is not particularly limited as long as it does not cause problems for the display image. The aspect ratio of the polyester film with the easy-to-adhesive layer can be 1:1, 4:3, 16:10, 16:9, 2:1, 5:4, 11:8, etc.

[0326] <<<Membrane Items>>>

[0327] A method for manufacturing polyester film with an easy-to-adhesive layer using a wet process with a coating liquid for the easy-to-adhesive layer, such as... Figure 2 As shown, a strip of film article 15L comprising a plurality of polyester films 15 with easy-to-adhere layers can be manufactured. The width and length of the film article 15L are not particularly limited. The width of the film article 15L can be 500 mm to 8000 mm, and the length can be 100 m to 10000 m.

[0328] By cutting the long strip of film article 15L into specified sizes, individual polyester films 15 with easy-to-adhere layers can be obtained. The film article 15L can be cut into single sheets according to the size of image display devices, etc. According to this example, film articles 15 of various sizes can be obtained from the long strip of film article 15L as needed. Therefore, polyester films 15 with easy-to-adhere layers of various sizes can be provided in a timely manner. During cutting, the ends of the film article 15L with unstable physical properties can be excluded.

[0329] like Figure 2 As shown, the membrane article 15L can be operated as a membrane roll 15R wound around the winding axis RA on the winding core 16. The operability of the membrane article 15L can be improved by the membrane roll 15R.

[0330] <<<Optical Laminates>>>

[0331] The optical laminate of this embodiment has one or more functional layers on the easy-to-adhere layer of the polyester film with the easy-to-adhere layer described in this embodiment.

[0332] Figure 3 This is a longitudinal cross-sectional view showing an example of an optical laminate. For example... Figure 3 As shown, the optical laminate 10 includes a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b can be a pair of main surfaces of the optical laminate 10. The optical laminate 10 sequentially includes a functional layer 30 and a polyester film 15 with an easy-to-adhere layer from the first surface 10a toward the second surface 10b. The optical laminate 10 sequentially includes a functional layer 30, an easy-to-adhere layer 25, and a polyester film 20 from the first surface 10a toward the second surface 10b.

[0333] exist Figure 3 In the example shown, the first surface 10a is composed of functional layer 30. Figure 3 In the example shown, the second side 10b is made of polyester film 20. Figure 3 In the example shown, the second surface 10b of the optical laminate 10 is also the second surface 15b of the polyester film 15 with an easy-to-adhere layer.

[0334] The optical layer 10 is not limited to the example shown in the figure. The optical layer 10 may also contain more than two functional layers.

[0335] <<Functional Layer>>

[0336] The functional layer can be a single layer or multiple layers. Examples of functional layers include hard coatings, anti-glare layers, anti-reflective layers, selective wavelength absorption layers, anti-fouling layers, and antistatic layers. A single functional layer can have multiple functions.

[0337] In functional layers, anti-reflective layers can be single-layered or multi-layered. A single-layer anti-reflective layer can be a low-refractive-index layer. A multi-layered anti-reflective layer can contain two layers (a high-refractive-index layer and a low-refractive-index layer), or it can contain three or more layers.

[0338] Examples of functional layers formed on an easily bondable layer include F1 to F7.

[0339] F1: Single-layer composition of hard coating

[0340] F2: Single-layer composition of the anti-glare layer

[0341] F3: Composed of multiple layers, including a hard coating and an anti-reflective layer.

[0342] F4: Composed of multiple layers, including an anti-glare layer and an anti-reflective layer.

[0343] F5: Composed of multiple layers, including a hard coating and an anti-fouling layer.

[0344] F6: Composed of multiple layers, including an anti-glare layer and an anti-fouling layer.

[0345] F7: Composed of multiple layers, including a hard coating, an anti-reflective layer, and an anti-fouling layer.

[0346] In one or more functional layers, the functional layer in contact with the easy-to-adhere layer may contain a cured product of an ionizing radiation-curing resin composition. The functional layer in contact with the easy-to-adhere layer may be a hard coating or an anti-glare layer. When the functional layer in contact with the easy-to-adhere layer contains a cured product of an ionizing radiation-curing resin composition, the adhesion of the optical laminate will decrease. However, in this embodiment, since the average value of δq / δa on the surface of the easy-to-adhere layer is within the aforementioned range, the adhesion of the optical laminate can be improved even if the functional layer in contact with the easy-to-adhere layer contains a cured product of an ionizing radiation-curing resin composition. Furthermore, by including a cured product of an ionizing radiation-curing resin composition in the functional layer in contact with the easy-to-adhere layer, the mechanical strength of the optical laminate can be improved.

[0347] In one or more functional layers, the functional layer in contact with the easy-to-adhere layer may comprise a cured product of an ionizing radiation-curable resin composition and have a thickness of 0.5 μm or more. By having the functional layer in contact with the easy-to-adhere layer have such a configuration, the mechanical strength of the optical laminate can be improved. The thickness of the functional layer in contact with the easy-to-adhere 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-to-adhere 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-to-adhere layer may be a hard coating or an anti-glare layer.

[0348] The thickness of the functional layer in contact with the easy-to-adhere layer can be 0.5μm to 20.0μm, 0.5μm to 10.0μm, 0.5μm to 7.0μm, or 0.5μm to 5.0μm. The thickness of the functional layer in contact with the easy-to-adhere layer can be 1.0μm to 20.0μm, 1.0μm to 10.0μm, 1.0μm to 7.0μm, or 1.0μm to 5.0μm. The thickness of the functional layer in contact with the easy-to-adhere layer can be 2.0μm to 20.0μm, 2.0μm to 10.0μm, 2.0μm to 7.0μm, or 2.0μm to 5.0μm.

[0349] Optical laminates are closer to the surface of the functional layer than polyester films with easy-to-bond layers, as an example. Figure 3 In the example shown, the contact angle of the first surface 10a with pure water can be 80 degrees or more, 85 degrees or more, 90 degrees or more, 95 degrees or more, or 100 degrees or more. By making the contact angle 80 degrees or more, other components can easily slide when in contact with the surface of the optical laminate. As a result, it is difficult for stress to be generated in the optical laminate. Therefore, the adhesion of the optical laminate can be improved. That is, by laminating a functional layer with an adjusted contact angle on the easy-adhesive layer of the polyester film with the easy-adhesive layer of this embodiment, where the average value of δq / δa is within a specified range, the adhesion of the optical laminate can be further improved.

[0350] If the outermost functional layer contains a large amount of antifouling agent, the contact angle of pure water can be increased. However, if the contact angle of pure water becomes too large, the surface hardness and other physical properties of the optical laminate will decrease. From this point of view, the contact angle can be less than 130 degrees or less than 120 degrees. 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. The resistivity of the pure water is set to be between 0.1 MΩ·cm and 15 MΩ·cm.

[0351] The contact angle of the surface of the optical laminate composed of functional layers can be above 80 degrees and below 130 degrees, above 80 degrees and below 120 degrees, above 85 degrees and below 130 degrees, above 85 degrees and below 120 degrees, above 90 degrees and below 130 degrees, above 90 degrees and below 120 degrees, above 95 degrees and below 130 degrees, above 95 degrees and below 120 degrees, above 100 degrees and below 130 degrees, or above 100 degrees and below 120 degrees.

[0352] The functional layer may include, for example, an adhesive resin and additives as needed. The thickness of the functional layer can be appropriately selected according to the intended function.

[0353] The functional layer may contain a cured product of a curable resin composition as an adhesive resin. Examples of cured products of curable resin compositions include cured products of thermosetting resin compositions and cured products of ionizing radiation-curable resin compositions. By including a cured product of an ionizing radiation-curable resin composition in the functional layer, mechanical strength can be effectively improved.

[0354] The proportion of the cured resin composition relative to the total adhesive resin of the functional layer can be 60% or more by mass, 80% or more by mass, 90% or more by mass, or 100% by mass.

[0355] A thermosetting resin composition is a thermosetting resin composition that contains at least a thermosetting resin and is cured by heating. Examples of thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins. A curing agent may be added to the thermosetting resin composition as needed.

[0356] The ionizing radiation curable resin composition contains a compound having ionizing radiation curable functional groups. In this specification, "a compound having ionizing radiation curable functional groups" is sometimes referred to as an "ionizing radiation curable compound." Ionizing radiation refers to electromagnetic waves or beams of charged particles containing energy quanta capable of polymerizing or cross-linking molecules. Ionizing radiation can be ultraviolet light or electron beams. Ionizing radiation can also be electromagnetic waves such as X-rays and gamma rays, or charged particle beams such as alpha rays and ion beams.

[0357] Examples of functional groups that can be cured by ionizing radiation include (meth)acryloyl, vinyl, allyl, and other olefinic unsaturated groups, as well as epoxy and oxetyl groups. Ionizing radiation-curable compounds can be compounds with olefinic unsaturated groups, compounds with two or more olefinic unsaturated groups, or polyfunctional (meth)acrylate compounds with two or more olefinic unsaturated groups.

[0358] As a multifunctional (meth)acrylate compound, either monomers or oligomers can be used. The functional layer can contain a cured multifunctional (meth)acrylate oligomer as an adhesive resin. In particular, the functional layer in contact with the easily bonded layer can contain a cured multifunctional (meth)acrylate oligomer as an adhesive resin. The cured multifunctional (meth)acrylate oligomer can suppress excessive curing shrinkage of the functional layer while maintaining good surface hardness of the optical laminate. Therefore, it is possible to improve the mechanical strength of the optical laminate while simultaneously improving its adhesion.

[0359] To achieve a better balance between mechanical strength and adhesion in optical laminates, oligomers and monomers can be incorporated as multifunctional (meth)acrylate compounds. The functional layer can contain cured products of multifunctional (meth)acrylate oligomers and cured products of multifunctional (meth)acrylate monomers as adhesive resins. In particular, the functional layer in contact with the easily bonded layer can contain cured products of multifunctional (meth)acrylate oligomers and cured products of multifunctional (meth)acrylate monomers as adhesive resins.

[0360] When using oligomers and monomers as multifunctional (meth)acrylate compounds, the mass ratio of oligomers to monomers can be 5:95 to 95:5, 50:50 to 85:15, or 60:40 to 80:20.

[0361] Examples of multifunctional (meth)acrylate oligomers include urethane (meth)acrylates, epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and other (meth)acrylate polymers. Uramate (meth)acrylates are obtained, for example, by reacting polyols and organic diisocyanates with hydroxy (meth)acrylates.

[0362] The weight-average molecular weight of multifunctional (meth)acrylate oligomers can be 500 or higher, or 1000 or higher. The weight-average molecular weight of multifunctional (meth)acrylate oligomers can also be 5000 or lower, or 3000 or lower. By ensuring the weight-average molecular weight of the oligomers is 500 or higher, excessive curing shrinkage of the functional layer can be suppressed. By ensuring the weight-average molecular weight of the oligomers is 500 or higher, 500 or higher, 3000 or lower, 1000 or higher, or 1000 or higher.

[0363] In this specification, weight-average molecular weight and number-average molecular weight refer to the converted values ​​of polystyrene determined by gel permeation chromatography.

[0364] Among multifunctional (meth)acrylate compounds, examples of difunctional (meth)acrylate monomers include ethylene glycol dimethacrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, and 1,6-hexanediol diacrylate. Examples of trifunctional or higher-functional (meth)acrylate monomers include trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol tetramethacrylate, and isocyanuric acid-modified trimethacrylate. A portion of the molecular skeleton of the above-mentioned (meth)acrylate monomers can be modified. For example, (meth)acrylate monomers modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl groups, cyclic alkyl groups, aromatic groups, bisphenols, etc., can be used.

[0365] For purposes such as adjusting the viscosity of the coating liquid for the functional layer, monofunctional (meth)acrylates can be added as ionizing radiation curing compounds. Examples of monofunctional (meth)acrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, and isobornyl methacrylate. One of the above-mentioned ionizing radiation curing compounds can be used alone. Two or more of the above-mentioned ionizing radiation curing compounds can also be used in combination. In addition to ionizing radiation curing compounds, polymers for adjusting viscosity can also be added to the coating liquid for the functional layer. The weight-average molecular weight of the polymer can exceed 5000 and be less than 200,000.

[0366] When the ionizing radiation curable compound is an ultraviolet-curable compound, the ionizing radiation curable resin composition may contain additives such as photopolymerization initiators and photopolymerization accelerators. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenyl ketone, mischlerone, benzoin, benzoyl dimethyl ether, benzoylbenzoate, α-acyl oxime ester, anthraquinone, haloketone, and thioxanthone derivatives. α-hydroxyalkylphenyl ketone, which is not prone to yellowing, may be used as the photopolymerization initiator.

[0367] Photopolymerization accelerators can reduce polymerization inhibition caused by air during curing and increase the curing speed. Examples of photopolymerization accelerators include one or more selected from isoamyl p-dimethylaminobenzoate, ethyl p-dimethylaminobenzoate, etc.

[0368] The functional layer may contain additives as needed. The additives may be appropriately selected from general materials based on the function imparted to the functional layer. For example, a functional layer imparting anti-glare properties may contain organic and / or inorganic particles as additives. A functional layer imparting anti-reflective properties may contain refractive index adjusting materials such as high-refractive-index and low-refractive-index materials as additives. A functional layer imparting antifouling properties may contain antifouling agents as additives. Furthermore, examples of additives include antistatic agents, leveling agents, UV absorbers, dyes, pigments, conductive particles, coagulants, defoamers, antioxidants, and light stabilizers.

[0369] <<Properties of Optical Laminates>>

[0370] The total light transmittance of optical laminates can be above 50%, above 80%, or above 90%. When measuring the total light transmittance of optical laminates, the incident surface is set to be closer to the main surface of the polyester film with the easy-to-bond layer than the functional layer. As an example, in... Figure 3 In the example shown, the incident surface for measuring the total light transmittance is set as the second surface 10b. The method for measuring the total light transmittance is as described above.

[0371] The transmittance haze of optical laminates can be above 0.3%, above 0.4%, or above 0.5%. The transmittance haze of optical laminates can be below 10%, below 7%, or below 5%. For a given transmittance haze of the optical laminate, the incident surface is set to be closer to the main surface of the polyester film with the easy-to-adhere layer than the functional layer. For example, in... Figure 3 In the example shown, the second surface 10b is used. The method for measuring the transmittance haze is as described above.

[0372] <<Size, shape, etc. of optical laminates>>

[0373] Optical laminates can be cut into single sheets of a specified size. There is no particular limitation on the size of a single sheet. The maximum diameter of a single optical laminate can be between 2 inches and approximately 500 inches. "Maximum diameter" refers to the maximum length that can be connected to any two points of the optical laminate. For example, in the case of a rectangular optical laminate, the diagonal of the rectangle is the maximum diameter. In the case of a circular optical laminate, the diameter of the circle is the maximum diameter.

[0374] There are no particular limitations on the shape of optical laminates. Examples of shapes for optical laminates include polygons such as triangles, quadrilaterals, and pentagons, circles, and random amorphous shapes. When the shape of the optical laminate is quadrilateral, the aspect ratio of the optical laminate is not particularly limited as long as it does not pose a problem for the display screen. It can be 1:1, 4:3, 16:10, 16:9, 2:1, 5:4, 11:8, etc.

[0375] <<<Laminated Items>>>

[0376] By means of a wet process for manufacturing optical laminates using a coating liquid for functional layers, such as Figure 4 As shown, it is possible to manufacture a strip-shaped laminated article 10L containing a plurality of optical laminates 10. The width and length of the laminated article 10L are not particularly limited. The width of the laminated article 10L can be more than 500 mm and less than 8000 mm, and the length can be more than 100 m and less than 10000 m.

[0377] By cutting the long strip of laminated article 10L into specified sizes, individual optical laminates 10 can be obtained. The laminated article 10L can be cut into individual sheets according to the size of the image display device, etc. According to this example, optical laminates 10 of various sizes can be obtained from the long strip of laminated article 10L as needed. Therefore, optical laminates 10 of various sizes can be provided in a timely manner. During cutting, laminated articles 10L with unstable physical properties can be excluded.

[0378] like Figure 4 As shown, the laminated article 10L can be operated as a laminated roll 10R wound around the winding axis RA and onto the winding core 11. The operability of the laminated article 10L can be improved by using the laminated roll 10R.

[0379] <<<Polarizing Plate>>>

[0380] The polarizer in this embodiment includes the optical elements described above.

[0381] Figure 5 An example of a polarizer is shown. Figure 5 The polarizer 40 shown includes a polarizing element 41, a first transparent protective plate 42 disposed on one side of the polarizing element 41, and a second transparent protective plate 43 disposed on the other side of the polarizing element 41. At least one of the first transparent protective plate 42 and the second transparent protective plate 43 can be the optical laminate 10 of this embodiment described above. A polyester film 15 with an easy-to-adhere layer is located between the functional layer 30 and the polarizing element 41.

[0382] In the illustrated example, only the first transparent protective plate 42 is a polyester film 15 with an easy-to-adhere layer. Alternatively, both the first transparent protective plate 42 and the second transparent protective plate 43 may be polyester films 15 with easy-to-adhere layers.

[0383] <Polarization element>

[0384] Polarizing elements can be sheet-type polarizing elements. Sheet-type polarizing elements can be resin films dyed and stretched using iodine or similar agents. Examples of resin films include polyvinyl alcohol films, polyvinyl alcohol formal films, polyvinyl alcohol acetal films, and ethylene-vinyl acetate copolymer saponified films. Examples of polarizing elements include wire grid-type polarizing elements composed of numerous parallel metal lines, coated polarizing elements coated with lyotropic liquid crystals or dichroic host-guest materials, and multilayer thin-film polarizing elements. Polarizing elements can also be reflective polarizing elements. Reflective polarizing elements can reflect non-transmissive polarizing components.

[0385] <Transparent Protective Panel>

[0386] A first transparent protective plate can be disposed on one side of the polarizing element. A second transparent protective plate can be disposed on the other side of the polarizing element. At least one of the first and second transparent protective plates is the optical laminate described in this embodiment.

[0387] Examples of first and second transparent protective plates include plastic films and glass. Examples of plastic films include polyester films, polycarbonate films, cyclic olefin polymer films, and acrylic films, as well as films stretched from one or more of these. Stretched films can improve mechanical strength. Examples of glass include alkaline glass, nitride glass, soda-lime glass, borosilicate glass, and lead glass. The glass used as a transparent protective plate for protecting polarizing elements can be used in conjunction with other components of the image display device. For example, a glass substrate for a liquid crystal display element can be used in conjunction with a transparent protective plate for protecting polarizing elements.

[0388] The polarizing element and the transparent protective plate can be bonded together using an adhesive. The adhesive can be a general-purpose adhesive or a PVA-based adhesive.

[0389] The polarizer in this embodiment can be either a first transparent protective plate or a second transparent protective plate, both of which are optical laminates as described in this embodiment. When the polarizer of this embodiment is used as a polarizer disposed on the light-emitting surface side of a display element, the transparent protective plate on the light-emitting surface side of the polarizing element can be an optical laminate as described in this embodiment. Conversely, when the polarizer of this embodiment is used as a polarizer disposed on the side of the display element opposite to the light-emitting surface, the transparent protective plate on the side of the polarizing element opposite to the light-emitting surface can be an optical laminate as described in this embodiment.

[0390] <<<Panel, Surface Panel>>>

[0391] The panel of this embodiment includes a support plate and an optical laminate of polyester film with an easy-to-adhere layer. The surface plate of this embodiment includes a support plate and an optical laminate on the support plate.

[0392] Figure 6 An example of panel 50 and surface plate 55 is shown. For example... Figure 6 As shown, panel 50 includes a support plate 51 and a polyester film with an easy-to-adhere layer according to this embodiment. The polyester film 15 with the easy-to-adhere layer can be bonded to the support plate 51. An adhesive layer, bonding layer, or other bonding layer can be disposed between the polyester film 15 with the easy-to-adhere layer and the support plate 51. In the panel, the polyester film can be bonded to the support plate. In the panel, the easy-to-adhere layer can be bonded to the support plate.

[0393] Panel 50 may include a functional layer 30. In this example, panel 50 may include an optical laminate 15 containing a polyester film 20 with an easy-to-adhere layer and a support plate 51. Panel 50 may be exposed as a component constituting a surface. Panel 50 may also not be an exposed component.

[0394] like Figure 6 As shown, the surface plate 55 includes a support plate 51 and the optical laminate 10 of this embodiment. The surface plate 55 is used in an exposed state as a component constituting the surface. The optical laminate 10 can be attached to the support plate 51. A polyester film 15 with an easy-to-adhere layer is located between the functional layer 30 and the support plate 51.

[0395] The panel and surface plate of this embodiment can be used, for example, as a surface plate for an image display device. The panel and surface plate of this embodiment can also be used as components for protecting items such as clocks and paintings. The panel or surface plate of this embodiment can also be used as components for shop windows and display cases. The support plate can be a resin board. The support plate can also be a glass plate.

[0396] The surface plate for an image display device can be configured such that the surface closer to the optical laminate than the support plate is located on the observer side. That is, the surface of the surface plate closer to the optical laminate than the support plate can face the side opposite to the display element. The surface plate for protecting an object can be configured such that the surface closer to the optical laminate than the support plate faces the side opposite to the object.

[0397] A lower limit can be set for the thickness of the support plate. By setting a lower limit for the thickness of the support plate, mechanical strength can be imparted to the panel and surface plate. From this perspective, the thickness of the support plate can be 10 μm or more. An upper limit can be set for the thickness of the support plate. By setting an upper limit for the thickness of the support plate, the large size and weight of the panel and surface plate can be suppressed. The thickness of the panel and surface plate can be 5000 μm or less. To meet the recent demand for thinner image display devices, the thickness of the panel and surface plate can be 1000 μm or less, 500 μm or less, or 100 μm or less. The thickness of the support plate can be 10 μm or more and 5000 μm or less, 10 μm or more and 100 μm or less.

[0398] <<<Image Display Panel>>>

[0399] The image display panel of this embodiment includes display elements and optical laminates. Figure 7 This shows an example of an image display panel. Figure 7 In the image display panel 60 shown, the optical laminate 10 of this embodiment is disposed on the display element 61. A polyester film 15 with an easy-to-adhere layer is located between the display element 61 and the functional layer 30.

[0400] Within an image display panel, an optically laminated material, compared to a polyester film with an easy-to-adhere layer, can have its side closer to the functional layer facing the opposite side to the display element. The optically laminate can form the outermost surface of the image display panel. The functional layer of the optically laminate can also form the outermost surface of the image display panel.

[0401] Examples of display elements include liquid crystal display elements, organic EL display elements, inorganic EL display elements, and plasma display elements. Examples of display elements include small LED display elements and micro LED display elements. Examples of display elements include laser holographic display elements. These display elements may also have touch panel functionality internally.

[0402] Examples of liquid crystal display methods, used as liquid crystal display elements, include IPS, VA, multi-domain, OCB, STN, TSTN, and ferroelectric liquid crystal displays. The display element, as a liquid crystal display element, can be illuminated from behind by a backlight. The liquid crystal display element can be located between the optical layer and the backlight. Examples of backlights include those using quantum dots and those using white light-emitting diodes.

[0403] The image display panel can be a foldable image display panel or a rollable image display panel. The image display panel can also be an image display panel with a touch panel.

[0404] There is no particular limitation on the size of the image display panel. The maximum diameter of the image display panel can be between 2 inches and approximately 500 inches. The maximum diameter refers to the maximum length that can be achieved by connecting any two points within the surface of the image display panel.

[0405] <<<Image Display Devices>>>

[0406] The image display device of this embodiment includes the image display panel described in this embodiment.

[0407] Figure 7 An example of an image display device is shown. Figure 7 In the image display device 65 shown, the optical laminate 10 is formed on the outermost surface. For example... Figure 7 As shown, 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. Figure 7 As shown, the display element 61 can be located between the backlight 62 and the optical layer 10.

[0408] The image display device of the present invention preferably further includes a drive control unit electrically connected to the image display panel and a housing for housing the image display panel and the drive control unit.

[0409] An image display device may include an effective display area. The effective display area is the area where an image can be displayed. For example, if the image display device has a housing surrounding the display element, the area inside the housing can be considered 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 connecting any two points within the effective display area. 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.

[0410] Example

[0411] The present invention will be specifically described below with reference to examples, comparative examples, and reference examples. The present invention is not limited to the examples.

[0412] <<<Evaluation, Measurement>>>

[0413] The following measurements and evaluations were performed on the polyester films with an easy-to-bond layer and the optical laminates obtained in the examples, comparative examples, and reference examples. The results are shown in Tables 1 and 2. Note that unless otherwise specified, the atmosphere for each measurement and evaluation was set to 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. Additionally, unless otherwise specified, the target samples were placed in the above atmosphere for 16 hours before the start of each measurement and evaluation.

[0414] <<1-1. In-plane orientation degree ΔP>

[0415] Samples of 7 mm × 7 mm were cut from the polyester films with an easy-to-bond layer of the examples, comparative examples, and reference examples. The in-plane orientation degree ΔP of the polyester films with an easy-to-bond layer was measured by the above method using the retardation measurement device “RETS-100” of Otsuka Electronics Co., Ltd. The measurement results of the in-plane orientation degree ΔP are shown in the “ΔP” column of Tables 1 and 2. The in-plane retardation Re was measured by the above 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.

[0416] Based on the values of the thickness-direction retardation Rth and the in-plane retardation Re obtained by the above measurement method using the retardation measurement device “RETS-100”, the Nz coefficient was calculated. It was confirmed whether the calculated Nz coefficient for each example was greater than 2.0 or 2.0 or less. The confirmation results are shown in the “2.0 < Nz” column of Tables 1 and 2. When the Nz coefficient is greater than 2.0, “Y” is entered in the “2.0 < Nz” column. When the Nz coefficient is 2.0 or less, “N” is entered in the “2.0 < Nz” column.

[0417] “nx - ny” was measured by the above measurement method using the retardation measurement device “RETS-100”. For the polyester films with an easy-to-bond layer of all the examples, “nx - ny” was 0.0300 or less.

[0418] <<1-2. Average value of δq / δa and coefficient of variation of δq / δa>>

[0419] Samples of 5 mm × 5 mm were cut from the polyester films with an easy-to-bond layer of the examples, comparative examples, and reference examples. By the above method, the measurement of δq / δa was performed to measure the average value of δq / δa and the coefficient of variation of δq / δa. 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.

[0420] Regarding the cut-out 5 mm × 5 mm sample, the 10 μm × 10 μm area of the surface of the easily adherable layer was measured using the phase mode of an atomic force microscope. The details of the measurement apparatus and measurement conditions are described below. From within the 10 μm × 10 μm measurement area, seven 2 μm × 2 μm measurement and evaluation areas were selected. These seven areas were selected from regions where the maximum height of the amplitude measured using the atomic force microscope was 90 nm or less and the arithmetic mean height of the amplitude was 10 nm or less. The δa, δq, and δq / δa of the above seven measurement and evaluation areas were calculated respectively. Based on the δa and δq of the five measurement and evaluation areas after excluding the maximum value and the minimum value from the above seven δq / δa, the average value and the coefficient of variation of δq / δa were calculated.

[0421] It should be noted that in the following measurement apparatus, when a 2 μm × 2 μm measurement and evaluation area is selected on the screen, the δa and δq of the selected measurement and evaluation area are automatically displayed. However, in order to set the following measurement apparatus, in the display screen of the following measurement apparatus, the item corresponding to δa is displayed as "Ra", and the item corresponding to δq is displayed as "Rq".

[0422] <Measurement apparatus>

[0423] The product name "SPM-9600" manufactured by Shimadzu Corporation

[0424] <Analysis software>

[0425] SPM manager

[0426] <AFM analysis conditions>

[0427] Tilt correction: Line fitting

[0428] <The cantilever used>

[0429] The model "NCHR" of NanoWorld Corporation

[0430] (Resonance frequency: 320 kHz, spring constant 42 N / m)

[0431] <Measurement mode>

[0432] Phase (In the "phase mode" of the above measurement apparatus, not only the phase but also the amplitude is measured.)

[0433] <Measurement conditions>

[0434] - Amplitude · Phase -

[0435] · Sensitivity: ×2

[0436] · Phase offset: 95.00 deg

[0437] -XY Control-

[0438] • Scan range: 10.0000μm

[0439] • Scan speed: 1.00Hz

[0440] • Pixel count: 512×512

[0441] • Bias X: 0.0000μm

[0442] • Bias Y: 0.0000μm

[0443] • Scanning angle: 0.0000deg

[0444] -Z control-

[0445] Operating point: 0.228V

[0446] •P gain: 0.001

[0447] • Gain: 15000.000

[0448] • Bias Z: 0.0630μm

[0449] <<1-3. Sealing>>

[0450] The following steps were performed to conduct a fit test and evaluate the fit of the optical laminates of Examples, Comparative Examples and Reference Example 1.

[0451] On the surface of the optical laminate in the embodiments, comparative examples, and reference example 1 that is composed of a hard coating layer ( Figure 3 On the first surface 10a), using the blade of a cutter, 11 longitudinally extending straight cutting lines and 11 transversely extending straight cutting lines are formed. These 11 longitudinal and 11 transverse cutting lines divide the optical laminate into a 100-grid checkerboard pattern. The 11 longitudinal cutting lines are spaced 1 mm apart laterally. The 11 transverse cutting lines are spaced 1 mm apart longitudinally. The blade of the cutter is NT Corporation's product number "BA-52P".

[0452] Next, adhesive tape (Mickey & Co., Ltd., product name "Cellotape (registered trademark)") was applied to the surface of the optical laminate divided into a checkerboard pattern and consisting of a hard coating. The adhesive tape was then peeled off, and a peel test was performed. This peel test was conducted according to the cross-cutting 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 the adhesion are shown in the "Adhesion" column of Table 1.

[0453] <Evaluation Criteria>

[0454] AA: There are no stripped cells, and there are no cells with partial defects.

[0455] A: There are no stripped cells, and the quality is judged to be acceptable, but there are cells with defects along the cutting line in a certain part.

[0456] B: There are stripped lattices.

[0457] <<1-4. Puncture Resistance>>

[0458] The puncture resistance of the optical laminates of Examples, Comparative Examples and Reference Example 1 was evaluated by performing puncture tests through the following steps.

[0459] Using the polyester film with an easy-to-adhesive layer from Examples, Comparative Examples, and Reference Example 1, samples for puncture tests were prepared as follows. The puncture test samples sequentially comprised a PET film, an optically clear adhesive film (OCA), chemically strengthened glass, a heat-sealing layer, a polyester film with an easy-to-adhesive layer, and a hard coating layer. When preparing the samples, care was taken to avoid wrinkles, the introduction of foreign matter, or other abnormalities.

[0460] First, A4-sized samples were cut from the polyester films with easy-to-adhesive layers of the Examples, Comparative Examples, and Reference Example 1. A hard coating solution of the following formulation was applied to the easy-to-adhesive layer of the polyester film to form a coated film. The coated film was dried at 80°C for 60 seconds, followed by irradiation with 200 mJ / cm². 2 The UV light is used to cure it. Through the above operations, a hard coating is formed on the easy-to-adhere layer. The thickness of the hard coating is 10 μm. Then, a 10 mm × 30 mm size is cut out, thereby obtaining a first laminate containing a polyester film with an easy-to-adhere layer and a hard coating.

[0461] <Coating solution for hard coating>

[0462] · 30 parts by weight of multifunctional acrylate monomer

[0463] (Nippon Kayaku Co., Ltd., Trade Name: PET-30)

[0464] · 2 parts by weight of photopolymerization initiator

[0465] (IGM Resins BV, Product Name: Omnirad 184)

[0466] 30 parts by weight of toluene

[0467] · 33 parts by weight of methyl ethyl ketone

[0468] Next, the heat-sealing resin composition described below is coated onto the surface of the first laminate, which is composed of a polyester film, to form a coated film. This coated film is then dried at 70°C for 1 minute to form a heat-sealing layer. Through these operations, a second laminate comprising a heat-sealing layer, a polyester film with an easy-to-adhere layer, and a hard coating layer is obtained.

[0469] <Composition of the heat-sealing resin composition>

[0470] • 100 parts by weight of amorphous polyester resin (Vylon 560, manufactured by Toyobo Co., Ltd.) • 5 parts by weight of hexamethylene diisocyanate (Coronate 2203, manufactured by Nippon Polyurethane Kogyo Co., Ltd.)

[0471] • Silane coupling agent (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by weight • Fluorine leveling agent (F568, manufactured by DIC) 0.2 parts by weight (solid conversion)

[0472] Solvent (MEK) 310 parts by weight

[0473] Solvent (toluene) 310 parts by weight

[0474] Next, the second laminate is bonded to the chemically strengthened glass using a heat-sealing layer. For heat sealing, an ACCO Brands Japan "Desktop Top Roll Laminator B35A3" is used. The roller temperature is set to 140°C–149°C. The feed speed is set to 0.3 m / min. Through these operations, a third laminate comprising chemically strengthened glass, a heat-sealing layer, a polyester film with an easy-to-bond layer, and a hard coating is obtained.

[0475] It should be noted that chemically strengthened glass is glass whose mechanical properties are strengthened through chemical methods, and it has a compressive stress layer on its surface. The thickness of chemically strengthened glass is set at 70 μm. Polyester films and optical laminates with easy-to-bond layers are bonded to chemically strengthened glass with a thickness of approximately 70 μm when applied to display devices. For example, chemically strengthened glass with a thickness of approximately 70 μm is used in foldable display elements.

[0476] A PET film is bonded to the surface of the third-layer composite, which is made of chemically strengthened glass, via an optically transparent adhesive film. The thickness of the optically transparent adhesive film is set to 50 μm. The optically transparent adhesive film is "8146-2" manufactured by 3M. The thickness of the PET film is set to 100 μm. The PET film is "A4160" manufactured by Toyobo. The PET film "A4160" consists of a PET layer and an easy-adhesive layer disposed only on one side of the PET layer. The side of the PET film "A4160" consisting of the easy-adhesive layer is brought into contact with the optically transparent adhesive film. Through the above operations, a sample for puncture testing is obtained.

[0477] As a puncture test, a pen is dropped vertically onto the puncture test sample to confirm whether the chemically strengthened glass has cracks.

[0478] During the puncture test, the puncture test sample was placed on the metal plate with the PET layer of the "A4160" PET film in contact with the metal plate. The metal plate was set on a horizontal platform. It was confirmed that the puncture test sample was extended as horizontally as possible. The metal plate was made of SUS304. A pen was dropped from various test heights onto the center of the hard coating of the puncture test sample. The pen tip was pointed downwards, and the pen was dropped vertically onto the puncture test sample. The pen was a BLEN0.5BAS88-BK (12g weight, 0.5mm tip) manufactured by Zebla. ).

[0479] The maximum test height (in cm) from which the chemically strengthened glass sample used in the puncture test did not crack is determined as the puncture strength. The test height is the vertical length from the outermost surface of the sample formed by the hard coating to the pen tip. A larger maximum test height (in cm) indicates higher puncture strength. In the puncture test, the drop height (test height) is increased by 1 cm. A ruler is fixed to a metal plate. The ruler extends vertically. Using this ruler, the test height in each test is visually confirmed.

[0480] The cracking of chemically strengthened glass is confirmed by visually observing it from various angles in a bright room at 1000 lux. A pen can be used continuously as long as the nib does not change under visual inspection. If a change in the nib is visually confirmed, or if ink leakage occurs, the pen should be replaced with a new one.

[0481] For each example of the polyester film with an easy-to-adhesive layer, 10 puncture test samples were prepared. The puncture resistance of the polyester films with easy-to-adhesive layers in the Examples, Comparative Examples, and Reference Example 1 was evaluated according to the following evaluation criteria. The evaluation results of the puncture resistance are shown in the "Puncture Resistance" column of Table 1.

[0482] <Evaluation Criteria>

[0483] AAA: The maximum test height at which no cracks were produced in 10 puncture test samples was 25 cm or more.

[0484] AA: The maximum test height at which no cracks were produced in samples tested with 8 or more punctures was 25 cm or more. However, this does not meet the AAA rating.

[0485] A: The maximum test height at which no cracks were produced in samples tested with 8 or more punctures is 20 cm or higher. However, neither AAA nor AA ratings are met.

[0486] B: Evaluations of AAA, AA, and A are all incorrect.

[0487] <<1-5. Bending Resistance>>

[0488] The bending resistance of the optical laminates of Examples, Comparative Examples and Reference Example 1 was evaluated by performing bending tests through the following steps.

[0489] Rectangular samples were cut 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 could be determined using the retardation measurement device "RETS-100" from Otsuka Electronics Co., Ltd., used in the measurement of the planar orientation degree ΔP. Using the retardation measurement device "RETS-100", the slow axis and fast axis of the optical laminates of each example were predetermined, thereby aligning the short side and long side of the sample with the slow axis and fast axis, respectively.

[0490] A durability testing machine, "DLDMLH-FS," manufactured by YUASA SYSTEM, was used to conduct 100,000 consecutive 180-degree bending tests. The bending speed was 120 times per minute. More detailed methods for the bending test are described below.

[0491] First, such as Figures 8A to 8C As shown, the two ends 91 of the sample 90 along its length are fixed to a pair of fixing parts 80 of the durability testing machine. The region of the sample 90 with a length of 10 mm from the short side is used as the end 91 and fixed to the fixing part 80 of the durability testing machine.

[0492] like Figures 8A to 8C As shown, the pair of fixed parts 80 are capable of moving relative to each other in the horizontal direction. The pair of fixed parts 80 can move towards each other or move away from each other.

[0493] In the bending test, the actions of bringing the pair of fixed parts 80 closer together and the actions of moving the pair of fixed parts 80 away from each other are repeatedly performed. For example... Figure 8B As shown, the fixed parts 80 are moved in a manner that brings them closer together. As a result, the optical laminate sample 90 deforms in a folding manner. Figure 8C As shown, the fixing parts 80 are brought close together to a position where the distance between the two ends 91 of the sample 90 is 7 mm. Figure 8C In the bent state shown, the sample is bent along an arc with a diameter of 7 mm. In the bent state, the bent front end 92 of the sample 90 does not protrude between the pair of fixing parts 80. Then, the pair of fixing parts 80 are moved away from each other, as shown. Figure 8AAs shown, sample 90 is unfolded. The bending and unfolding of the sample is repeated 100,000 times. Sample 90 is bent 120 times every minute.

[0494] For each example of an optical laminate, 10 samples were prepared for bending tests. The samples after the bending tests 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.

[0495] <Evaluation Criteria>

[0496] AAA: Of the 10 samples used in the bending test, none broke, and no defects such as delamination were observed. No abnormalities such as cloudiness were found in the 10 samples used in the bending test upon close inspection.

[0497] AA: For the 10 samples used in the bending test, no samples broke or showed defects such as delamination. For one or two samples used in the bending test, the quality was judged to be acceptable, but some cloudiness was observed upon close inspection. However, this does not meet the AAA rating.

[0498] A: For the 10 samples used in the bending test, no samples broke or showed defects such as delamination. For more than 3 samples used in the bending test, the quality was judged to be acceptable, but some cloudiness was observed upon close inspection. However, neither the AAA nor AA ratings were met.

[0499] B: Ten bending test samples did not break, but several bending test samples showed defects such as delamination. However, ratings AAA, AA, and A were not met.

[0500] BB: For more than one sample used in the bending test, fracture occurred before reaching 100,000 bending cycles. However, ratings AAA, AA, A, and B are all unsatisfactory.

[0501] <<1-6. Pencil Hardness>>

[0502] Regarding the polyester film with an easy-to-adhesive layer in Examples, Comparative Examples, and Reference Example 1, the pencil hardness of the polyester film was measured. The pencil hardness was measured on the surface of the polyester film composed of the easy-to-adhesive layer (…). Figure 1 The second side (15b) of the middle section was measured.

[0503] Evaluation samples were cut from the polyester film with the easy-to-adhere layer in each example. The evaluation samples were rectangular in shape. The shorter side of the rectangle was set to 50 mm, and the longer side to 100 mm. The rectangular samples were unfolded on a pencil hardness tester in a manner that prevented wrinkles and warping. The two shorter sides of the unfolded sample were fixed to the pencil hardness tester along their entire length using repair tape. The repair tape was "810-3-18" manufactured by 3M. The pencil hardness tester used was the SH-V1 pencil scratch hardness tester manufactured by Toyo Seiki Co., Ltd. The SH-V1 pencil scratch hardness tester was electric.

[0504] The following conditions are used to determine the hardness of pencils. Other conditions are as specified in JIS K5600-5-4:1999.

[0505] • Pencil moving speed: 1mm / s

[0506] • Pencil travel distance: 7mm

[0507] Temperature: 23℃±2℃

[0508] Relative humidity: 50±5%

[0509] • Pencil angle: 45 degrees

[0510] • Direction of pencil movement (direction of pencil scratching): The direction of pencil movement should be parallel to the slow axis direction of the polyester film with the easy-to-adhere layer. The slow axis of each sample is determined using the same method as the bending test.

[0511] For each example, five pencil hardness tests were conducted using pencils of various hardnesses. For a pencil of a specified hardness, the specified hardness was considered acceptable if the film remained undamaged in three or more of the five tests. For each example sample, tests were conducted until the pencil hardness test failed; the highest hardness deemed acceptable was taken as the pencil hardness for that example. The results of the pencil hardness measurements are shown in the "Pencil" column of Table 1.

[0512] <<1-7. Through the Fog>>

[0513] Samples measuring 5 cm × 10 cm were cut from the optical films of Examples, Comparative Examples, and Reference Example 1. The transmittance haze of the polyester film with the easy-to-adhere layer in each example was measured using the method described above. The transmittance haze was measured using a haze meter "HM-150" manufactured by Murakami Color Technology Research Institute. For all examples of polyester films with the easy-to-adhere layer, the transmittance haze was 1.0% or less.

[0514] <<1-8. Total Light Transmittance>>

[0515] Samples measuring 5 cm × 10 cm were cut from the optical films of Examples, Comparative Examples, and Reference Example 1. The total light transmittance of the polyester film with the easy-to-adhere layer in 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 Technology Research Institute. For all examples of polyester films with the easy-to-adhere layer, the total light transmittance was 90% or higher.

[0516] <<1-9. Transportability>>

[0517] For examples A through E, a 15L film article with an easy-to-adhere layer of polyester film with a width of 680mm and a length of 500m is produced (refer to...). Figure 2 Membrane roll 15R is obtained by winding membrane article 15L onto winding core 16. For reference examples A to E, 10 membrane rolls 15R are prepared respectively.

[0518] use Figure 9 The manufacturing apparatus 70 for the optical laminate 10 shown produces a laminate article 10L from a film article 15L. The manufacturing apparatus 70 includes a feeding device 71, a coating device 72, a drying device 73, a curing device 74, and a recycling device 75. The manufacturing apparatus 70 produces the laminate article 10L from the film article 15L in a roll-to-roll manner. For reference examples A to E, 10 film rolls 15R are used to produce 10 laminate rolls 10R.

[0519] The supply device 71 rotatably holds the membrane roll 15R. The supply device 71 rotates the winding core 16, leading to the unwinding of the membrane article 15L from the membrane roll 15R. The coating device 72 applies a coating liquid for the following hard coating layer to the membrane article 15L. The drying device 73 dries the coating film of the hard coating liquid on the membrane article 15L. The curing device 74 irradiates the coating film of the hard coating liquid with ultraviolet light to cure it. The recycling device 75 winds the laminate article 10L onto the winding core 16 for recycling.

[0520] <Coating solution for hard coating>

[0521] · 30 parts by weight of multifunctional acrylate monomer

[0522] (Nippon Kayaku Co., Ltd., Trade Name: PET-30)

[0523] · 2 parts by weight of photopolymerization initiator

[0524] (IGM Resins BV, Product Name: Omnirad 184)

[0525] 30 parts by weight of toluene

[0526] · 33 parts by weight of methyl ethyl ketone

[0527] The manufacturing apparatus 70 may also include a suction roller. The suction roller attracts and holds the film article 15L. Therefore, the film article 15L can be conveyed without clamping rollers. Figure 9 As shown, the suction roller 76 is located between the curing device 74 and the recycling device 75.

[0528] The suction roller 76 adopts the following specifications.

[0529] • Corner protection: 180°

[0530] • Suction width: 500mm

[0531] • Mesh size: 500μm

[0532] • Attraction angle: 90°

[0533] ·Outer diameter: 600mm

[0534] The tension of the film article 15L supplied from the supply device 71 is 200N. The tension of the laminate article 10L recovered by the recovery device 75 is 250N. The circumferential speed of the conveying roller is measured using a rotary encoder mounted on the suction roller. The conveying speed is set to 20m / min. Other manufacturing conditions, such as the drying conditions in the drying device 73 and the curing conditions in the curing device 74, are set to the same conditions used in the manufacturing method of the optical laminate in Example 1.

[0535] For each example, when manufacturing 10 laminated rolls of 10R, the change in circumferential speed measured using a rotary encoder was confirmed. The transportability of each example was evaluated according to the following evaluation criteria. The evaluation results of the transportability are shown in the "Transportability" column of Table 2.

[0536] <Evaluation Criteria>

[0537] AA: During the manufacture of 10 laminated rolls 10R, the circumferential speed can be maintained at 20±0.3m / min for 100% of the total length (500m×10 rolls).

[0538] A: During the manufacture of 10 laminated rolls 10R, the circumferential speed can be maintained at 20±0.3m / min for more than 80% and less than 100% of the total length (500m×10 rolls).

[0539] B: During the manufacture of 10 laminated rolls 10R, the circumferential speed can be maintained at 20±0.3m / min for more than 70% and less than 80% of the total length (500m×10 rolls).

[0540] BB: During the manufacture of 10 laminated rolls 10R, the circumferential speed can be maintained at 20±0.3m / min for less than 70% of the total length (500m×10 rolls).

[0541] In all the examples from Reference A to Reference E, the variation in circumferential speed was not to the extent that it would be a problem in mass production.

[0542] For Reference Example A, with an in-plane phase difference Re of 1512 nm, and Reference Example E, with an in-plane phase difference Re of 2934 nm, the circumferential speed measured by the rotary encoder repeatedly decelerated and accelerated between 19.6 m / min and 20.5 m / min every 5 seconds. Regarding Reference Examples A and E, abnormal noise occurred during the conveying of the polyester film with the easily adhesive layer. Furthermore, regarding Reference Examples A and E, when the conveying was unstable, defects such as damage occurred to the film article 15L or the laminated article 10L.

[0543] Regarding reference examples B to D, no abnormal noises were produced, and the circumferential speed remained stable. No damage or other appearance defects were observed in the 15L membrane item and the 10L laminated item.

[0544] <<<2. Optical laminates as examples and comparative examples for evaluation>>>

[0545] As described below, optical laminates of Examples 1-8, Comparative Examples 1-7, Reference Example 1, and Reference Examples A-E were fabricated. Each optical laminate comprises a polyester film with an easy-to-adhere layer and a functional layer formed on the polyester film with the easy-to-adhere layer. The polyester film with the easy-to-adhere layer comprises a polyester film and an easy-to-adhere layer formed on the polyester film using an easy-to-adhere layer coating liquid. In each example, the polyester film is selected from a plurality of PET films. In each example, it is set to be selected from a plurality of easy-to-adhere layer coating liquids.

[0546] <<2-1. Preparation of coating liquid for easy-to-adhere layer>>

[0547] As described below, coating solutions A to D are used to prepare the easy-to-adhere layer.

[0548] <2-1-1. Coating liquid A for easy-to-adhere layers>

[0549] The following materials were mixed and subjected to transesterification at 200°C for 2 hours to obtain compound 1.

[0550] 110 parts by weight of dimethyl terephthalate

[0551] · 30 parts by weight of ethylene glycol

[0552] · 30 parts by weight of 1,4-butanediol

[0553] 0.1 parts by weight of zinc acetate

[0554] 0.1 parts by weight of antimony trioxide

[0555] Next, 4.0 parts by mass of fumaric acid were added to compound 1, and an esterification reaction was carried out at 230°C for 2 hours. Then, a polycondensation reaction was carried out under reduced pressure (3–6 mmHg) at 250°C for 1 hour to obtain compound 2. 230 parts by mass of methyl ethyl ketone and 120 parts by mass of isopropanol were added to compound 2 as solvents. Compound 2 and the solvent were heated to 70°C while stirring to dissolve compound 2 in the solvent, yielding resin solution 3.

[0556] Add 30 parts by weight of m-phenylenedimethyl diisocyanate to resin solution 3 and stir for 3 hours. Then, raise the temperature of the reaction vessel to 100°C to remove methyl ethyl ketone and isopropanol, obtaining resin 4 for easy bonding.

[0557] The easy-to-bond resin 4 is dissolved in a mixed solvent prepared by mixing methyl ethyl ketone and toluene in a mass ratio of 8:2. Through the above operations, an easy-to-bond coating liquid A with a solid content of 5% by mass is obtained. The mass ratio of polyester to polyurethane components in the resin contained in the easy-to-bond coating liquid A is 8:2.

[0558] <2-1-2. Coating liquid B for easy-to-adhere layers>

[0559] The amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in compound 1 and the amount of isophthalic diisocyanate added to resin solution 3 were changed to the following amounts. Otherwise, the process was repeated in the same manner as with coating solution A for easy-to-adhere layers to obtain coating solution B for easy-to-adhere layers. The mass ratio of polyester to polyurethane components in the resin of coating solution B for easy-to-adhere layers is 7:3.

[0560] 100 parts by weight of dimethyl terephthalate

[0561] · 28 parts by weight of ethylene glycol

[0562] · 28 parts by weight of 1,4-butanediol

[0563] 46 parts by weight of m-phenylenedimethyl diisocyanate

[0564] <2-1-3. Coating liquid C for easy-to-adhere layers>

[0565] The amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in compound 1 and the amount of isophthalic diisocyanate added to resin solution 3 were changed to the following amounts, except that the process was the same as that for easy-to-adhesive coating solution A, to obtain easy-to-adhesive coating solution C. The mass ratio of polyester to polyurethane components in the resin contained in easy-to-adhesive coating solution C is 6:4.

[0566] 70 parts by weight of dimethyl terephthalate

[0567] · 25 parts by weight of ethylene glycol

[0568] · 25 parts by weight of 1,4-butanediol

[0569] 60 parts by weight of m-phenylenedimethyl diisocyanate

[0570] <2-1-4. Coating liquid D for easy-to-adhere layers>

[0571] The amounts of dimethyl terephthalate, ethylene glycol, and 1,4-butanediol in compound 1 and the amount of isophthalic diisocyanate added to resin solution 3 were changed to the following amounts, except that the process was the same as that for easy-to-adhesive coating solution A, to obtain easy-to-adhesive coating solution C. The mass ratio of polyester to polyurethane components in the resin contained in easy-to-adhesive coating solution C is 4:6.

[0572] 30 parts by weight of dimethyl terephthalate

[0573] · 23 parts by weight of ethylene glycol

[0574] · 23 parts by weight of 1,4-butanediol

[0575] 89 parts by weight of m-phenylenedimethyl diisocyanate

[0576] <2-1-5. Coating liquid E for easy-to-adhere layers>

[0577] While stirring, 15g of polyvinyl alcohol was gradually added to 85g of ion-exchanged water. The mixture was heated to 70-90°C and stirred to prepare a PVA-A aqueous solution with a solid content of 15% by mass. The polyvinyl alcohol used was "PVA28-98" (formerly "PVA117") manufactured by KURARAY Co., Ltd.

[0578] A mixture of PVA-A aqueous solution and aqueous polyurethane resin at a solids ratio of 60:40 was diluted with a solvent to obtain coating liquid E for easy-to-adhesive layers. The solids concentration of coating liquid E for easy-to-adhesive layers was 14.6% by mass. The aqueous polyurethane resin used was "VYLONAL MD2000" manufactured by Toyobo MC Co., Ltd. The solvent was a mixture of water and isopropanol at a mass ratio of 7:3.

[0579] <2-1-6. Coating liquid F for easy-to-adhere layers>

[0580] 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 a coating liquid F for easy-to-adhesive layer. The solid content concentration of coating liquid F for easy-to-adhesive 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 Co., Ltd. The solvent was a mixture of methyl ethyl ketone and toluene in a mass ratio of 8:2.

[0581] <2-1-7. Coating liquid G for easy-to-adhere layers>

[0582] A polyester-based water-dispersible urethane adhesive was diluted with a solvent to obtain a coating liquid G for easy-to-adhere layers. The solids concentration of coating liquid G for easy-to-adhere layers was 14.6% by mass. "SUPERFLEX SF210" (35% solids concentration) manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. was used as the polyester-based water-dispersible urethane adhesive. The solvent was a mixture of water and isopropanol at a mass ratio of 7:3.

[0583] <<2-2. Fabrication and Preparation of PET Film>>

[0584] As examples, comparative examples, and reference examples, the following PET films 1 to 6 were prepared.

[0585] <2-2-1. PET film 1>

[0586] 1 kg of PET (absorption center wavelength: 320 nm) and 0.1 kg of UV absorber were melt-mixed at 280°C using a mixer to produce granules containing the UV absorber. The UV absorber was 2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one). This granule and PET with a melting point of 258°C were fed into a single-screw extruder and melt-mixed at 290°C, then extruded through a T-die. The extruded PET was cast onto a casting drum with controlled surface temperature to obtain a cast film. The amount of UV absorber in the cast film was 3 parts by mass relative to 100 parts by mass of PET.

[0587] The surface temperature of the casting drum is controlled as follows: The portion of the resin adhering to the die is set at 50°C. The portion where the resin peels off is set at 25°C. The temperature gradually decreases from the resin-adhering portion to the resin peeling point.

[0588] The resulting cast film was heated with a roller assembly set to 120°C, and then stretched 5.1 times its original length along the flow direction in a stretching zone, followed by temporary cooling. The length of the stretching zone in the flow direction was 480 mm. Stretch roller A was located at the beginning of the stretching zone, and stretch roller B was located at the end. Stretch rollers A and B each had two clamping rollers. The cast film was stretched while being heated from both sides using a radiant heater, with the film temperature at 135°C at a point 180 mm from the beginning of the 480 mm stretching zone. The time for the cast film to pass through the stretching zone in the flow direction was 0.50 seconds.

[0589] Next, the uniaxially stretched film is fed into a tenter frame. After preheating with rollers set to 120°C, the uniaxially stretched film is stretched 4.9 times along its width direction while undergoing heat treatment with hot air at 105°C in the first stage and 136°C in the second stage. Here, the stretching interval in the width direction is divided into two parts, with the stretch amount at the midpoint of the stretching interval in the width direction being 80% of the stretch amount at the end of the stretching interval. The stretch amount is calculated by subtracting the film width before stretching from the film width at the measurement point. The film stretched along the width direction is then heat-treated in stages within the tenter frame with hot air ranging from 180°C to a heat treatment temperature of 245°C. Next, the film stretched along the width direction undergoes a 1% relaxation treatment along the width direction under the same temperature conditions, followed by a further rapid cooling to 100°C and then another 1% relaxation treatment along the width direction. The relaxed PET film is then wound up to obtain a biaxially stretched PET film 1 with a thickness of 40 μm.

[0590] <2-2-2. PET film 2>

[0591] The time for the cast film to pass through the stretching zone in the flow direction was changed to 0.45 seconds, and the same procedure as for PET film 1 was performed to obtain biaxially oriented PET film 2.

[0592] <2-2-3. PET film 3>

[0593] The time for the cast film to pass through the stretching zone in the flow direction was changed to 0.40 seconds, and the same procedure as for PET film 1 was followed to obtain biaxially oriented PET film 3.

[0594] <2-2-4. PET film 4>

[0595] The time for the cast film to pass through the stretching zone in the flow direction was changed to 0.35 seconds, and the same procedure as for PET film 1 was performed to obtain biaxially oriented PET film 4.

[0596] <2-2-5. PET film 5>

[0597] The time for the cast film to pass through the stretching zone in the flow direction was changed to 0.30 seconds, and the same procedure as for PET film 1 was followed to obtain biaxially oriented PET film 5.

[0598] <2-2-6. PET film 6>

[0599] The time for the cast film to pass through the stretching zone in the flow direction was changed to 0.25 seconds, and the same procedure as for PET film 1 was followed to obtain biaxially oriented PET film 6.

[0600] <2-2-7. PET film 7>

[0601] As PET film 7, a PET film with an easy-to-adhesive layer, "COSMOSHINE A4160", which can be obtained from Toyobo Co., Ltd., was prepared. This polyester film with an easy-to-adhesive layer comprises a biaxially oriented PET film and an easy-to-adhesive layer disposed on one side of the biaxially oriented PET film. The thickness of the polyester film with the easy-to-adhesive layer as PET film 7 is 38 μm.

[0602] <2-2-8. PET film 8>

[0603] The stretch ratio in the flow direction was changed to 3.8 times, and the stretch ratio in the width direction was changed to 4.4 times. Otherwise, the same operation as PET film 1 was performed to obtain PET film 8.

[0604] <2-2-9. PET film 9>

[0605] The stretch ratio in the flow direction was changed to 3.5 times, and the stretch ratio in the width direction was changed to 4.4 times. Otherwise, the same operation as PET film 1 was performed to obtain biaxially oriented PET film 9.

[0606] <2-2-10. PET film 10>

[0607] The stretch ratio in the flow direction was changed to 3.5 times, and the stretch ratio in the width direction was changed to 4.7 times. Otherwise, the same operation as PET film 1 was performed to obtain biaxially oriented PET film 10.

[0608] <2-2-11.PET film 11>

[0609] The stretch ratio in the flow direction was changed to 3.3 times, and the stretch ratio in the width direction was changed to 4.7 times. Otherwise, the same operation as PET film 1 was performed to obtain biaxially oriented PET film 11.

[0610] <2-2-12.PET film 12>

[0611] The stretch ratio in the flow direction was changed to 3.3 times, and the stretch ratio in the width direction was changed to 5.0 times. Otherwise, the same operation as PET film 1 was performed to obtain biaxially oriented PET film 12.

[0612] <2-2-13. PET film 13>

[0613] The stretch ratio in the flow direction was changed to 3.3 times, and the stretch ratio in the width direction was changed to 5.1 times. Otherwise, the same operation as PET film 1 was performed to obtain biaxially oriented PET film 13.

[0614] <<2-3. Fabrication of Polyester Films and Optical Laminates with Easy-to-Adhesive Layers>>

[0615] Using the above-described easy-adhesive coating liquid and PET film, polyester films and optical laminates with easy-adhesive layers of Examples 1-8, Comparative Examples 1-4, Reference Example 1 and Reference Examples A-E were prepared.

[0616] [Example 1]

[0617] The above-mentioned easy-to-adhesive layer coating solution A is applied to PET film 2 to form a coated film. The coated film is dried at 90°C for 60 seconds. Through the above operations, an easy-to-adhesive layer with a thickness of 100 nm is formed, and the polyester film with an easy-to-adhesive layer of Example 1 is obtained.

[0618] A coating liquid for a hard coating with the following formulation is applied to the easy-to-adhesive layer of a polyester film with an easy-to-adhesive layer to form a coated film. The coated film is dried at 80°C for 60 seconds and irradiated with 200 mJ / cm². 2 The ultraviolet light is used to cure it. Through the above operations, a hard coating with a dry thickness of 10 μm is formed on the easy-to-adhere layer, resulting in the optical laminate of Example 1.

[0619] <Coating solution for hard coating>

[0620] · 30 parts by weight of multifunctional acrylate monomer

[0621] (Nippon Kayaku Co., Ltd., Trade Name: PET-30)

[0622] · 2 parts by weight of photopolymerization initiator

[0623] (IGM Resins BV, Product Name: Omnirad 184)

[0624] 30 parts by weight of toluene

[0625] · 33 parts by weight of methyl ethyl ketone

[0626] [Example 2]

[0627] By replacing PET film 2 with PET film 3, and otherwise operating in the same manner as in Example 1, the polyester film and optical laminate with an easy-to-adhere layer of Example 2 were obtained.

[0628] [Example 3]

[0629] By replacing PET film 2 with PET film 4, and otherwise operating in the same manner as in Example 1, the polyester film and optical laminate with an easy-to-adhere layer of Example 3 were obtained.

[0630] [Example 4]

[0631] By replacing PET film 2 with PET film 5, and otherwise operating in the same manner as in Example 1, the polyester film and optical laminate with an easy-to-adhere layer of Example 4 were obtained.

[0632] [Example 5]

[0633] The PET film 2 was replaced with PET film 3, and the coating liquid A for the easy-to-adhere layer was replaced with coating liquid B for the easy-to-adhere layer. Otherwise, the operation was the same as in Example 1 to obtain the polyester film and optical laminate with the easy-to-adhere layer of Example 5.

[0634] [Example 6]

[0635] The PET film 2 was replaced with PET film 3, and the coating liquid A for the easy-to-adhere layer was replaced with coating liquid C for the easy-to-adhere layer. Otherwise, the operation was the same as in Example 1 to obtain the polyester film and optical laminate with the easy-to-adhere layer of Example 6.

[0636] [Example 7]

[0637] The PET film 2 was changed to PET film 5, the coating liquid A for the easy-to-adhesive layer was changed to coating liquid B for the easy-to-adhesive layer, and the drying conditions when drying the coating film with the easy-to-adhesive layer coating liquid were changed from 90°C and 60 seconds to 100°C and 60 seconds. Otherwise, the operation was the same as in Example 1, and the polyester film and optical laminate with the easy-to-adhesive layer of Example 7 were obtained.

[0638] [Example 8]

[0639] The PET film 2 was changed to PET film 3, the coating liquid A for the easy-to-adhesive layer was changed to coating liquid B for the easy-to-adhesive layer, and the drying conditions when drying the coating film with the easy-to-adhesive layer coating liquid were changed from 90°C and 60 seconds to 110°C and 60 seconds. Otherwise, the operation was the same as in Example 1, and the polyester film and optical laminate with the easy-to-adhesive layer of Comparative Example 8 were obtained.

[0640] [Comparative Example 1]

[0641] By replacing PET film 2 with PET film 1, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer and an optical laminate of Comparative Example 1 were obtained.

[0642] [Comparative Example 2]

[0643] By replacing PET film 2 with PET film 6, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer and an optical laminate of Comparative Example 2 were obtained.

[0644] [Comparative Example 3]

[0645] The PET film 2 was replaced with PET film 3, and the coating liquid A for the easy-to-adhesive layer was replaced with coating liquid D for the easy-to-adhesive layer. Otherwise, the operation was the same as in Example 1, and the polyester film and optical laminate with the easy-to-adhesive layer of Comparative Example 3 were obtained.

[0646] [Comparative Example 4]

[0647] The PET film 2 and the easy-to-adhesion layer were replaced with commercially available PET film 7 (polyester film with an easy-to-adhesion layer), and the operation was the same as in Example 1 to obtain the polyester film with an easy-to-adhesion layer and the optical laminate of Comparative Example 4.

[0648] [Comparative Example 5]

[0649] The PET film 2 was replaced with PET film 3, the easy-to-adhesive layer coating liquid A was replaced with easy-to-adhesive layer coating liquid E, the coating timing of easy-to-adhesive layer coating liquid E was changed, the coating amount of easy-to-adhesive layer coating liquid E was changed, and the drying conditions of the coated film of easy-to-adhesive layer coating liquid E were changed. Otherwise, the operation was the same as in Example 1, resulting in the polyester film and optical laminate with an easy-to-adhesive layer of Comparative Example 5. In Comparative Example 5, easy-to-adhesive layer coating liquid E was coated on a uniaxially stretched film before stretching in the width direction. The coated film of easy-to-adhesive layer coating liquid E was stretched together with the uniaxially stretched film in the width direction. The coating amount of easy-to-adhesive layer coating liquid E was 0.2 g / m² based on the mass of the dried easy-to-adhesive layer. 2 The drying conditions for the coated film were set at 80°C for 20 seconds.

[0650] [Comparative Example 6]

[0651] The PET film 2 was replaced with PET film 3, the easy-to-adhesive layer coating liquid A was replaced with easy-to-adhesive layer coating liquid F, the drying conditions of the coating film with easy-to-adhesive layer coating liquid F were changed, and the coating amount of easy-to-adhesive layer coating liquid F was changed. Otherwise, the operation was the same as in Example 1 to obtain the polyester film and optical laminate with an easy-to-adhesive layer of Comparative Example 6. The drying conditions of the coating film were set to 70°C for 30 seconds. The coating amount of the adhesive layer coating liquid F was 5 g / m³ (wet weight). 2 The mass of the dried, easily bonded layer is 0.5 g / m. 2.

[0652] [Comparative Example 7]

[0653] The PET film 2 was replaced with PET film 3, the easy-to-adhesive layer coating liquid A was replaced with easy-to-adhesive layer coating liquid G, the coating method of the coating film of easy-to-adhesive layer coating liquid G was changed, the drying conditions of the coating film of easy-to-adhesive layer coating liquid G were changed, and the coating amount of easy-to-adhesive layer coating liquid G was changed. Otherwise, the operation was the same as in Example 1, resulting in the polyester film and optical laminate with an easy-to-adhesive layer of Comparative Example 7. The coating of the easy-to-adhesive layer coating liquid G was performed using a coating tester with a gravure roller having a grid #200. The drying conditions of the coating film were set to 150°C for 1 minute. The coating amount of the adhesive layer coating liquid F was set to obtain an easy-to-adhesive layer with a thickness of 0.3 μm.

[0654] [Reference Example 1]

[0655] By replacing PET film 2 with PET film 8, and otherwise operating in the same manner as in Example 1, the polyester film and optical laminate with an easy-to-adhere layer of Reference Example 1 were obtained.

[0656] [Reference Example A]

[0657] By replacing PET film 2 with PET film 9, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer of Reference Example A is obtained.

[0658] [Reference Example B]

[0659] By replacing PET film 2 with PET film 10, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer of Reference Example B was obtained.

[0660] [Reference Example C]

[0661] By replacing PET film 2 with PET film 11, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer as in Reference Example C is obtained.

[0662] [Reference Example D]

[0663] By replacing PET film 2 with PET film 12, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer of Reference Example D was obtained.

[0664] [Reference Example E]

[0665] By replacing PET film 2 with PET film 13, and otherwise operating in the same manner as in Example 1, a polyester film with an easy-to-adhere layer of Reference Example E is obtained.

[0666] [Table 1]

[0667] [Table 2]

[0668] By setting the average value of δq / δa to 1.125 or higher and 1.80 or lower according to feature (B), high adhesion can be imparted to polyester films and optical laminates with easy-to-adhere layers. By setting the face orientation degree ΔP to 0.150 or higher and 0.195 or lower according to feature (A), mechanical strength can be improved.

[0669] The degree of orientation ΔP is correlated with puncture resistance. However, the correlation between ΔP and puncture resistance is not very strong, weaker than the correlation between ΔP and flexural resistance. This can be understood from the fact that Comparative Example 3, with an orientation ΔP of 0.176, exhibits lower puncture resistance than other examples with the same degree of orientation ΔP. On the other hand, among samples with an average δq / δa value between 1.125 and 1.80, the correlation between ΔP and puncture resistance is very strong. From this perspective, it can be said that combining the aforementioned characteristic (A) related to orientation ΔP and the aforementioned characteristic (B) related to the average δq / δa value can yield unexpected results.

[0670] More specifically, Comparative Example 3 has the same face orientation degree ΔP as Examples 2, 5, and 6, but has a larger average value of δq / δa than Examples 2, 5, and 6. The evaluations of puncture resistance and flexural resistance of Comparative Example 3 differ from those of Examples 2, 5, and 6, and are unsatisfactory. That is, by setting an upper limit on the average value of δq / δa according to feature (B) in addition to feature (A), puncture resistance and flexural resistance can be improved more consistently.

[0671] One possible reason for this phenomenon is that by setting an upper limit on the average value of δq / δa, the mechanical properties of the polyester film with the easy-to-adhere layer become homogeneous, and the flexural strength, which is a more localized indicator of mechanical strength, and the puncture resistance, which is arguably a more localized indicator of mechanical strength than flexural strength, can be steadily improved. However, the present invention is not limited to this conjecture.

[0672] Similarly, Comparative Examples 5-7 have the same face orientation degree ΔP as Example 2, but have a smaller average value of δq / δa than Example 2. The evaluation of the bending resistance and puncture resistance of Comparative Examples 5-7 is adequate, but lower than that of Example 2. That is, by setting a lower limit on the average value of δq / δa according to feature (B) in addition to feature (A), the bending resistance and puncture resistance can be improved more stably.

[0673] One reason for the speculation that the bend resistance can be stably improved is that by setting a lower limit on the average value of δq / δa, the mechanical properties of the polyester film with an easy-bonding layer can be inhibited from becoming too homogeneous, and a load can be repeatedly applied to a certain area. One reason for the speculation that the puncture resistance can be stably improved is that by setting a lower limit on the average value of δq / δa, the mechanical properties of the polyester film with an easy-bonding layer can be inhibited from becoming too homogeneous, and an impact load can be concentratedly applied to a very small position. However, the present invention is not limited to this speculation.

[0674] It should be noted that in Example 2, Example 5, Example 6, and Comparative Example 3, the ratio of the polyester component in the easy-bonding layer decreases in turn. In Example 2, Example 5, Example 6, and Comparative Example 3, the average value of δq / δa decreases in turn, and the adhesion in Comparative Example 3 is insufficient. The ratio of the polyester component in the easy-bonding layer of Comparative Example 6 is greater than the ratio of the polyester component in the easy-bonding layer of Example 2. The average value of δq / δa of Comparative Example 6 is less than the average value of δq / δa of Example 2. However, the adhesion evaluation of Comparative Example 6 is "B". It is considered that this phenomenon is due to the fact that in Comparative Example 6, the viscoelasticity of the surface of the easy-bonding layer becomes too homogeneous, and the adhesion between the easy-bonding layer and the functional layer decreases. That is, it is considered that in Comparative Example 6, the adhesion between the easy-bonding layer and the polyester film is improved, but the adhesion between the easy-bonding layer and the functional layer decreases. Comparative Example 5 and Comparative Example 7 are the same as Comparative Example 6, the average value of δq / δa is less than 1.125, and the adhesion evaluation is insufficient.

[0675] In addition to features (A) and (B), through the above-mentioned feature (B1) related to the coefficient of variation of δq / δa, the adhesion between the polyester film with an easy-bonding layer and the optical laminate can be more stably improved. Regarding this point, it can be understood from the adhesion evaluation results of Example 5 and Example 8.

[0676] In Reference Example 1 where the Nz coefficient is 2.0 or less, the results of adhesion, puncture resistance, bend resistance, and pencil hardness were all judged to be qualified. However, when manufacturing the polyester film with an easy-bonding layer in Reference Example 1, the wettability of the coating liquid for the easy-bonding layer on the PET film decreased compared with other examples. Compared with other examples, the coefficient of variation of δq / δa becomes larger. Compared with Example 3 with the same degree of surface orientation ΔP, the adhesion, puncture resistance, and bend resistance are all worse.

[0677] Symbol Explanation

[0678] 10: Optical laminate; 10a: First surface; 10b: Second surface; 10L: Laminated article; 10R: Laminated roll; 11: Winding core; 15: Polyester film with easy-to-adhere layer; 15a: First surface; 15b: Second surface; 15L: Film article; 15R: Film roll; 16: Winding core; 20: Polyester film; 25: Easy-to-adhere layer; 30: Functional layer; 40: Polarizer; 41: Polarizing element; 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-to-adhere layer, comprising a polyester film and an easy-to-adhere layer, wherein the surface orientation degree is 0.150 to 0.195, and the average value of δq / δa of the surface of the easy-to-adhere layer is 1.125 to 1.

80. The average value of δq / δa is calculated as follows: The phase mode of atomic force microscopy was used to measure a 10 μm × 10 μm area on the surface of the easily bondable layer. This measurement yielded the distribution of the phase signal on the surface of the easily bondable layer, with the unit of phase signal being [deg]. Let the arithmetic mean of the phase signal shown in Equation 1 below be δa, and let the root mean square of the phase signal shown in Equation 2 below be δq. In Equations 1 and 2 below, rectangular coordinate axes X and Y are arranged on the reference surface representing the average value of the phase signal, and the axis orthogonal to the reference surface is set as the Z axis. The surface of the phase signal is set as f(x,y). In Equations 1 and 2 below, the size of the region for calculating δa and δq is set as Lx and Ly. In Equations 1 and 2 below, Ar = Lx × Ly. Seven 2μm×2μm measurement evaluation areas were selected from the 10μm×10μm measurement area. δa, δq, and δq / δa were calculated for each of the seven measurement evaluation areas. Based on the five δq / δa values ​​remaining after excluding the maximum and minimum values ​​from the seven δq / δa values, the average value of δq / δa was calculated. [Mathematical Expression 1] [Mathematical Expression 2] 。 2. The polyester film with an easy-to-adhere layer according to claim 1, wherein, The coefficient of variation of δq / δa calculated based on the above 5 δq / δa values ​​is below 0.

150.

3. The polyester film with an easy-to-adhere layer according to claim 1, wherein, When the refractive index along the slow axis in the same plane is defined as nx, and the refractive index along the direction orthogonal to the slow axis in the same plane is defined as ny, nx and ny satisfy the following relationship. nx-ny≤0.0300.

4. The polyester film with an easy-to-adhere layer according to claim 1, wherein the thickness is more than 10 μm and less than 75 μm.

5. The polyester film with an easy-to-adhere layer according to claim 1, wherein the in-plane phase difference is less than 2000 nm.

6. A membrane article comprising a polyester film having an easy-to-adhere layer as described in any one of claims 1 to 5.

7. The membrane article according to claim 6, which is wound around the winding axis.

8. An optical laminate having one or more functional layers on the easy-to-adhere 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 easy-to-adhere layer comprises 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 of 80 degrees or more with pure water.

11. A laminated article comprising a plurality of optical laminates as described in claim 8.

12. The laminated article according to claim 11, which is wound around the winding axis.

13. A polarizer comprising, in sequence, a first transparent protective plate, a polarizing element, and a second transparent protective plate, wherein at least one of the first transparent protective plate and the second transparent protective plate is an optical laminate as described in claim 8, and the polyester film with an easy-to-adhere layer is located between the functional layer and the polarizing element.

14. A panel comprising a support plate and a polyester film with an easy-to-adhere layer as described in any one of claims 1 to 5.

15. A surface panel comprising a support plate and an optical laminate of claim 8, wherein the polyester film with an easy-to-adhere layer is located between the functional layer and the support plate.

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

17. An image display device comprising the image display panel of claim 16.

Images