Laminated film, polarizing plate, display device, and method for producing polarizing plate roll

Abstract

An object of the present invention is to provide a laminated film that, although being a thin film, has excellent transportability, can be processed in the same manner as conventional polarizer protective films, and further has excellent curl controllability during polarizer processing, thereby improving the productivity (adhesiveness to a polarizer) of polarizer processing, a high-quality polarizer having no optical unevenness and including the laminated film, a display device, and a method for manufacturing a polarizer roll. The laminated film of the present invention is characterized in that it is a laminated film in which a peelable functional layer is laminated on a base film, the thickness of the functional layer is in the range of 1 to 19 μm, the total thickness of the laminated film is 50 μm or less, and when the humidity expansion coefficient of the base film at 23°C is CHE1 (ppm / %RH), the thickness is d1 (μm), the humidity expansion coefficient of the functional layer at 23°C is CHE2 (ppm / %RH), and the thickness is d2 (μm), the relationship of the following formula 1 is satisfied. Formula 1: 0.20 < |(CHE1 - CHE2)| × (d2 / d1) < 2.00.

Description

Technical Field

[0001] The present invention relates to a laminated film, a polarizer having the laminated film, a display device and a method for manufacturing a polarizer roll. More specifically, it relates to a laminated film that, although being a thin film, can be handled in the same manner as a conventional polarizer protective film and has excellent curl control during polarizer processing, thereby improving the productivity of polarizer processing. Background Art

[0002] Liquid crystal display devices have low power consumption and can be made thinner, and therefore are widely used as image display devices such as televisions (TVs) and personal computers (PCs).

[0003] In recent years, as televisions (TVs) have been required to be larger and thinner and to improve display quality, thinner components are required to suppress optical unevenness caused by stress due to bending of display panels and dimensional changes of components.

[0004] In addition, in applications such as notebook and small- to medium-sized personal computers, smartphones, and tablet computers, there is a particularly high demand for thinner components, and further thinning of functional films (such as viewing angle compensation films and polarizing plate protective films) is required.

[0005] However, if the film is too thin, the film loses its elasticity and rigidity, and the film transportability and yield of the laminating process are reduced. Therefore, Patent Document 1 proposes a method in which a thin functional film is formed on a substrate film (also called a "carrier film") so as to be releasable, and a thick laminated film is used for transport until lamination, and the unnecessary substrate film is removed after lamination with a polarizer.

[0006] However, in the case of stacking two films made of different materials such as a base film and a thin functional film disposed thereon, if the inherent humidity expansion coefficients of these materials are different, curling will occur due to humidity fluctuations. If the curling is very small, it may be easier to perform the lamination and peeling process, but if the curling is strong, it is difficult to laminat, resulting in a problem of reducing the yield of the polarizer manufacturing process.

[0007] As described above, Patent Document 1 discloses a method for preparing a thin functional film by laminating the functional film on a substrate film so that the functional film can be peeled off. However, since there is a difference in humidity dependence between the material for preparing the functional film and the substrate film, there is a problem that the polarizer curls due to moisture absorption during processing or storage, which is difficult to handle during the above-mentioned transportation and lamination. These problems are particularly significant when the laminated film is a thin film.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2018-45220 Summary of the invention

[0011] The present invention is made in view of the above-mentioned problems and conditions, and the problem to be solved is to provide a laminated film which, although being a thin film, has excellent transportability and can be handled in the same way as conventional polarizer protective films, and further has excellent curl controllability during polarizer processing, thereby improving the productivity of polarizer processing (adhesion to the polarizer), a high-quality polarizer without optical unevenness having the laminated film, a display device, and a method for manufacturing a polarizer roll.

[0012] In order to solve the above-mentioned problems, the inventors of the present invention have discovered a laminated film having a peelable functional layer laminated on a substrate film during a study on the causes of the above-mentioned problems. When the substrate film and the functional layer have thicknesses within a specific range respectively, and the humidity expansion coefficient and thickness of the substrate film, as well as the humidity expansion coefficient and thickness of the functional layer satisfy a specific relationship, a laminated film can be obtained which is a thin film but has excellent transportability and can be handled in the same manner as conventional polarizer protective films. Furthermore, it has excellent curl controllability during polarizer processing, and the productivity of polarizer processing (adhesion to polarizer) is improved.

[0013] That is, the above-mentioned problems of the present invention can be solved by the following means.

[0014] 1. A laminated film, characterized in that a peelable functional layer is laminated on a base film,

[0015] The thickness of the functional layer is in the range of 1 to 19 μm.

[0016] The total thickness of the laminated film is 50 μm or less.

[0017] When the humidity expansion coefficient of the above-mentioned base film at 23°C is set to CHE1 (ppm / %RH) and the thickness is set to d1 (μm), and when the humidity expansion coefficient of the above-mentioned functional layer at 23°C is set to CHE2 (ppm / %RH) and the thickness is set to d2 (μm), the relationship of the following formula (1) is satisfied.

[0018] Formula (1) 0.20<|(CHE1-CHE2)|×(d2 / d1)<2.00

[0019] 2. The laminated film according to item 1, wherein the thickness of the functional layer is in the range of 2 to 10 μm.

[0020] 3. The laminated film according to item 1 or 2, wherein the total thickness of the laminated film is in the range of 30 to 45 μm.

[0021] 4. The laminated film according to any one of items 1 to 3, characterized in that the retardation value Ro of the functional layer defined by the following formula (i) is in the range of 0 to 20 nm, and the retardation value Rt defined by the following formula (ii) is in the range of -25 to 25 nm.

[0022] Formula (i)Ro=(n x -n y )×d

[0023] Formula (ii) Rt = {(n x +n y ) / 2-n z}×d

[0024] (In the above formulas (i) and (ii), Ro is the retardation value in the in-plane direction of the functional layer, Rt is the retardation value in the thickness direction of the functional layer, and n x is the refractive index of the functional layer in the direction of the slow axis in the plane, n y is the refractive index of the functional layer in the direction of the phase-advancing axis, n z is the refractive index of the functional layer in the thickness direction (refractive index is measured at 23°C and 55% RH at a wavelength of 590 nm), and d is the thickness of the film (nm)

[0025] 5. The laminated film according to any one of items 1 to 4, wherein when the residual solvent content of the substrate film is S1 and the residual solvent content of the functional layer is S2, the following formula (2) is satisfied.

[0026] Formula (2) 10<S1<S2<1000(ppm)

[0027] 6. The laminated film according to item 5, wherein the boiling point of a main residual solvent among the residual solvents is 100° C. or less under atmospheric pressure.

[0028] 7. The laminated film according to item 5 or 6, wherein the residual solvent is a chlorine-based solvent.

[0029] 8. The laminated film according to any one of items 5 to 7, wherein the residual solvent is dichloromethane.

[0030] 9. The laminated film according to any one of items 5 to 8, wherein the residual solvent contains dichloromethane and alcohols.

[0031] 10. The laminated film according to any one of items 1 to 9, wherein the substrate film is a biaxially stretched polyester film having a humidity expansion coefficient CHE1 at 23° C. in the range of 10 to 20 ppm / % RH.

[0032] 11. The laminated film according to any one of items 1 to 10, wherein the functional layer contains a polymer material having a carbonyl group in a side chain.

[0033] 12. The laminated film according to any one of items 1 to 10, wherein the functional layer contains a polymer material having a cyclic structure in its main chain.

[0034] 13. A polarizing plate comprising the laminated film according to any one of items 1 to 12.

[0035] 14. A display device comprising the laminated film according to any one of items 1 to 12 or the polarizing plate according to item 13.

[0036] 15. A method for producing a polarizing plate roll, characterized in that the laminated film according to any one of items 1 to 12 is wound while being bonded to at least one surface of a polarizer, comprising the following steps:

[0037] The laminated film is wound up while being bonded to the polarizer so that the layers of the polarizer, the pressure-sensitive adhesive layer, the functional layer, and the base film are in this order from the inner side of the roll.

[0038] According to the above-mentioned means of the present invention, it is possible to provide a laminated film which, although being a thin film, has excellent transportability, can be handled in the same manner as conventional polarizer protective films, and further has excellent curl controllability during polarizer processing, thereby improving the productivity of polarizer processing (adhesion to the polarizer), a high-quality polarizer having no optical unevenness and having the laminated film, a display device, and a method for manufacturing a polarizer roll.

[0039] The mechanism of expression and action of the effects of the present invention have not yet been clarified, but are presumed as follows.

[0040] When a laminated film (hereinafter also referred to as a "laminated body") having a functional layer disposed on a substrate film is formed, the warping and curling of the laminated film is a very important factor in order to improve its yield. The mechanism of warping is complex and its generation mechanism has not been clearly understood so far, so a method for controlling warping without sacrificing productivity has not been developed so far.

[0041] In particular, in the case of handling laminated films in which very thin functional layers are arranged, there is little knowledge of how to predict and improve the magnitude of curling in the laminate of a base film (functioning as a protective film) and the functional layer, especially curling affected by humidity.

[0042] The present inventors have studied how to predict and improve the mechanism of such humidity-induced warping, using a heat-induced curl prediction formula for a laminate as a reference.

[0043] The following formula was proposed for curling of a laminate due to heat, and as a result of the study, an index for curling of a laminate under certain conditions such as humidity fluctuations and curling in warm water was found to be accurately predicted with a relatively simple formula using the assumptions shown below.

[0044] Specifically, it was found that the curling of the laminate in warm water (or under high humidity) is greatly affected by (1) the difference in the coefficient of hydroscopic expansion (CHE) between the base film and the functional layer and (2) the thickness ratio between the base film and the functional layer.

[0045] It is known that a curling prediction formula of a bimetallic laminate based on heat is represented by the following formula (a).

[0046] Formula (a) Curl curvature 1 / R∝6(α2-α1)(ΔT)(1+m 2 ) / h[3(1+m) 2 +(1+mn){m 2 +(mn) -1}]

[0047] (In the formula, α: represents the thermal expansion coefficient, α1 represents the functional layer, and α2 represents the base film. ΔT: represents the temperature rise width. h: represents the total thickness of the base film (d1) and the thickness of the functional layer (d2). m: represents the thickness ratio (d1 / d2) of the base film thickness (d1) and the thickness of the functional layer (d2). n: represents the elastic modulus ratio (f1 / f2) of the base film elastic modulus (f1) and the elastic modulus of the functional layer (f2))

[0048] Here, 1) the difference in humidity expansion coefficient between the base film and the functional layer is directly replaced by the difference in thermal expansion coefficient (α2-α1)=ΔCHE).

[0049] 2) When comparing various membranes under a certain condition such as immersion in water, the humidity difference (ΔT) is treated as a constant.

[0050] 3) The elastic modulus ratio n is assumed to not vary significantly in the organic polymer material and is assumed to be n≈1.

[0051] 4) The thickness ratio m of the thickness of the substrate film (d1) / the thickness of the functional layer (d2) is actually the thickness of the functional layer (d2) < the thickness of the substrate film (d1), and is therefore 1<<m, becoming (1 / m)<<1.

[0052] 5) The total thickness h is a practically manageable thickness and is also within a certain numerical range and is treated as a constant.

[0053] Therefore, if the above approximation conditions 1) to 5) are added, equation (a) can be finally expressed by equation (f).

[0054] If "h" in formula (a) is regarded as a constant, then formula (a) is:

[0055] Formula (b) Curvature 1 / R∝ΔCHE×(1+m) / [3+3m+m 2 +m -1 ]

[0056] If we regard “m” in formula (a) as -1 ≈0”, then formula (b) is:

[0057] Formula (c) Curl curvature 1 / R≈ΔCHE×(1+m) / [3+3m+m 2 ]

[0058] Formula (d) Curl curvature 1 / R≈ΔCHE×(1+m) / 3(1+m) 2

[0059] Since "m is 1<<m" in formula (a), formula (d) is,

[0060] Formula (e) Curl curvature 1 / R∝ΔCHE×1 / (1+m)

[0061] Furthermore, since "m is 1<<m" in formula (e), if "1+m" ​​is set to "m", then the curling curvature 1 / R∝ΔCHE / m in formula (f) is

[0062] That is, the present invention was discovered by conducting the above-mentioned empirical experiment in which it was inferred that the curl curvature 1 / R can be represented by "|(CHE1-CHE2)|×(d2 / d1)" in the formula (1) of the present invention.

[0063] Conceptually, it can also be understood based on a qualitative phenomenon, that is, although it often expands due to humidity, the thicker the layer, the more severe the curling becomes.

[0064] On the other hand, the inventors also found that if the laminated body does not curl at all, there is no opportunity for peeling when the base film is peeled, which reduces workability and also reduces yield.

[0065] When the polarizer and the functional layer are laminated together, if the humidity expansion coefficient of the substrate film is too large compared to that of the functional layer, the substrate film is easily curled to the outside, and the center of the functional layer floats from the surface of the polarizer, making it impossible to fully laminate the functional layer and the polarizer (see Figure 1 ). Furthermore, it is considered that when the curl is large, optical unevenness is likely to occur due to internal stress on the functional layer.

[0066] In addition, when the laminated film is stored in a roll under high humidity, if the difference in the amount of moisture expansion of each layer is large, interlayer delamination is likely to occur, or deformation such as wrinkles is likely to occur in the functional layer. If interlayer delamination occurs, the transport stability is likely to be reduced during the transport of the laminated film and the production of the polarizer. If the functional layer is deformed such as wrinkles, the flatness of the functional layer is impaired, so there is a problem that the adhesion between the functional layer and the polarizer cannot be fully improved.

[0067] Therefore, the present invention is made in view of the above situation. It is speculated that by suppressing the interlayer delamination and deformation of the functional layer during the storage of the laminated film under high humidity, the humidity expansion coefficient and thickness of the substrate film and the functional layer, which will become the main factors of curling, are adjusted to satisfy the relationship of the above formula (1), thereby obtaining a laminated film that not only has excellent curl control during polarizing plate processing, but also suppresses the productivity of polarizing plate processing (adhesion to the polarizer) and the generation of optical unevenness of the functional layer.

[0068] Specifically, it is speculated that by appropriately increasing the humidity expansion coefficient of the substrate film compared to the functional layer at 23°C and appropriately designing their respective thickness ratios so as to satisfy the range of the above formula (1), the direction and size of the moderate curling of the laminated film can be controlled to improve the productivity of polarizing plate processing (adhesion to the polarizer), and the effect of suppressing the formation of wrinkles and optical unevenness in the functional layer can be exhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a schematic diagram for explaining the mechanism of curling in a high-humidity environment when a polarizing plate is produced using a peelable film laminate.

[0070] Figure 2 It is a schematic diagram showing a cross section of the laminated film of the present invention.

[0071] Figure 3 It is a schematic diagram showing a method for producing a laminated film according to one embodiment of the present invention.

[0072] Figure 4A It is a cross-sectional view of a polarizing plate with a substrate film.

[0073] Figure 4BIt is a cross-sectional view of the polarizing plate from which the base film has been peeled off. DETAILED DESCRIPTION

[0074] The laminated film of the present invention is characterized in that a functional layer capable of being peeled off is laminated on a substrate film, the thickness of the functional layer is in the range of 1 to 19 μm, the total thickness of the laminated film is 50 μm or less, and the relationship of the above formula (1) is satisfied when the humidity expansion coefficient of the substrate film at 23°C is CHE1 (ppm / %RH) and the thickness is d1 (μm), and the humidity expansion coefficient of the functional layer at 23°C is CHE2 (ppm / %RH) and the thickness is d2 (μm). This feature is a technical feature shared or corresponding to the following embodiments.

[0075] As an embodiment of the present invention, from the viewpoint of showing the effect of the present invention, the thickness of the functional layer is within the range of 2 to 10 μm, and wrinkles and curling deformation of the functional layer as a thin film are suppressed, and when the substrate film is peeled off and the functional layer is attached to the polarizer, a thinner polarizer is provided, which is preferred from this viewpoint. Furthermore, it is also preferred from the viewpoint of suppressing optical unevenness of a liquid crystal display device using the polarizer.

[0076] The total thickness of the laminated film is preferably within a range of 30 to 45 μm, since the laminated film has excellent rigidity and transportability despite being a thin film and can be handled in the same manner as a conventional polarizing plate protective film.

[0077] The retardation value Ro defined by the above formula (i) of the functional layer is in the range of 0 to 20 nm, and the retardation value Rt defined by the above formula (ii) is in the range of -25 to 25 nm, which is a preferred range of retardation values ​​from the perspective of providing a thin polarizing plate used in an IPS mode display device. In addition, from the perspective of using a functional layer that imparts an extremely thin film without affecting the optical properties of various films, a functional layer with such optical properties is also preferred.

[0078] When the residual solvent content of the substrate film is set to S1 and the residual solvent content of the functional layer is set to S2, it is preferred to satisfy the above formula (2) from the viewpoint of controlling the humidity expansion coefficients (CHE1 and CHE2) of the substrate film and the functional layer. The solvent also penetrates into the substrate film, thereby forming a plurality of mixed layers between the laminated films, which can ensure good process adaptability by not being easily peeled off during various processes. It should be noted that when a mixed solvent is used, the value of the sum of all solvent types is used as an indicator.

[0079] In addition, when preparing the above-mentioned substrate film and the slurry for the functional layer for film formation, from the viewpoint of easy operation, it is preferred that the boiling point of the main solvent in the above-mentioned residual solvent is below 100°C at atmospheric pressure, and the above-mentioned residual solvent is a chlorine-based solvent, and further the above-mentioned residual solvent is dichloromethane, wherein the above-mentioned residual solvent includes dichloromethane and alcohols. By using a low boiling point solvent and a chlorine-based solvent with high solubility, the drying time after film formation can be shortened. It is estimated that the coating film with a short drying time has a lower density than the coating film with a long drying time, and as a result, the permeability of water changes, and CHE2 can be slightly controlled. It should be noted that the main solvent refers to a solvent mixed at a ratio greater than 50% by mass among the solvent types of the coating liquid.

[0080] The substrate film is a biaxially stretched polyester film, and from the viewpoint of suppressing curling of the entire laminated film by an appropriate humidity expansion coefficient CHE1, the humidity expansion coefficient CHE1 of the polyester film at 23°C is preferably in the range of 10 to 20 ppm / %RH. In addition, by making the polyester film biaxially stretched, the anisotropy of CHE1 is eliminated, and the generation of unevenness can be suppressed.

[0081] In order to control physical properties such as the humidity expansion coefficient and improve optical properties, the functional layer preferably contains a linear polymer material having a carbonyl group in a side chain or a polymer material having a cyclic structure in a main chain as the resin used.

[0082] The polarizing plate of the present invention includes the laminated film of the present invention, and thus can be processed by the same polarizing plate processing steps as those in the related art without reducing productivity, even without requiring complicated processing steps.

[0083] The display device of the present invention is a preferred embodiment from the viewpoint that a high-quality display device free from light leakage and optical unevenness can be obtained by including the laminated film of the present invention or the polarizing plate of the present invention.

[0084] The manufacturing method of the polarizing plate roll of the present invention is characterized in that it is a manufacturing method of the polarizing plate roll in which the laminated film of the present invention is adhered to at least one surface of the polarizer and rolled up, and includes the step of adhering the laminated film to the polarizer and rolling up in the order of the layers of the polarizer, the functional layer and the substrate film from the inner side of the roll. By the manufacturing method of the polarizing plate roll, the substrate film can also serve as a protective film, resulting in a reduction in the number of parts and a simplification of the processing steps.

[0085] Hereinafter, the present invention and its constituent elements, as well as forms and modes for implementing the present invention will be described in detail. It should be noted that in the present application, "to" is used to mean that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0086] 《Overview of the laminated film of the present invention》

[0087] The laminated film of the present invention is characterized in that it is a laminated film having a peelable functional layer laminated on a base film, the thickness of the functional layer is in the range of 1 to 19 μm, the total thickness of the laminated film is less than 50 μm, and when the humidity expansion coefficient of the base film at 23°C is set to CHE1 (ppm / %RH) and the thickness is set to d1 (μm), and when the humidity expansion coefficient of the functional layer at 23°C is set to CHE2 (ppm / %RH) and the thickness is set to d2 (μm), the relationship of the following formula (1) is satisfied.

[0088] Formula (1) 0.20<|(CHE1-CHE2)|×(d2 / d1)<2.00

[0089] (Determination of the coefficient of humidity expansion (CHE) at 23°C)

[0090] The film sample is fixed in a constant temperature and humidity chamber with a width of 1 cm and a sample length of 15 cm. It is dehumidified to a certain humidity (about 30% RH). After the film length becomes constant, if it is humidified (about 80% RH), it will begin to elongate by absorbing moisture. After about 24 hours, the moisture absorption reaches equilibrium, and the elongation of the film also reaches equilibrium. According to the elongation at this time, the following formula is used to calculate. At this time, the atmospheric temperature is kept constant at 23°C.

[0091] Humidity expansion coefficient at 23°C (ppm / %RH) = elongation (cm) / (specimen length (cm) × humidity difference) × 10 6

[0092] As a means of controlling the humidity expansion coefficient (hereinafter also referred to as "CHE"), it is preferred to adjust the drying speed (film density) of the substrate film and the functional layer after film formation. If high-speed drying is performed, a sparse film is easily formed, and CHE becomes larger.

[0093] As a means of controlling CHE of the substrate film, stretching (ratio) and thermal relaxation can be used during or after film formation. If the stretching (ratio) is high, a dense film is formed and the CHE becomes small, and if thermal relaxation is performed, a coarse film is easily formed and the CHE becomes large. Therefore, the relationship with the CHE of the functional layer can be considered and used as a means of adjusting so as to fall within the range of the above formula (1).

[0094] In addition, the film-forming materials used in the substrate film and the functional layer are also related to the control of CHE. When the film-forming material of the functional layer is a straight-chain polymer material having a carbonyl group in the side chain, in addition to the control of CHE, it also has moderate moisture permeability, thereby being able to impart the effect of suppressing the optical unevenness of the polarizer. In particular, acrylic resins with low photoelasticity tend to show good properties. Furthermore, the above-mentioned film-forming materials have polymer materials with a cyclic structure in the main chain (such as cycloolefin resins) that have little change in optical properties relative to humidity and are not prone to unevenness from humidity, so using these polymer materials is also a preferred method.

[0095] The value of the above formula (1) of the laminated film is large, and when it exceeds 2.00, as described above, the curl is large, and it is difficult to bond the laminated film during the manufacture of the polarizer in practice. On the other hand, if the value of the formula (1) is less than 0.20, it is difficult to peel the substrate film and the functional layer, resulting in peeling errors. Therefore, it is necessary to adjust the CHE and thickness within the range of the formula (1).

[0096] In addition, depending on the size of the rolled-up film, bubbles may be generated when the film is attached to a polarizer (polyvinyl alcohol film), or breakage or wrinkles may occur.

[0097] The mechanism of the generation of bubbles during lamination has not yet been determined, but is considered to be as follows.

[0098] If the curl is too large, the unevenness in the TD direction (the width direction of the long film) becomes too large, and air is drawn in during lamination to generate bubbles. On the contrary, if the curl is too small, it is easy to be too affected by the curl in the MD direction (the width direction of the long film), and air is drawn in to generate bubbles.

[0099] In the present invention, the adhesion can be improved by controlling the curl within a specific range. From the viewpoint of improving the adhesion, the range of the index (|(CHE1-CHE2)|×(d2 / d1)) of the present application corresponding to the curl is greater than 0.20 and less than 2.00, more preferably in the range of 0.30 to 1.00, and particularly preferably in the range of 0.40 to 0.70.

[0100] Furthermore, when the functional film is bonded to a polarizer (polyvinyl alcohol film), interference fringes may occur.

[0101] The reason for the interference fringes is not yet clearly understood, but it is believed that after the laminated film of the present invention is attached, when the substrate film is peeled off, the functional layer shrinks. At this time, a slight uneven refractive index is generated at the interface between the polarizer and the functional layer, and it is believed that the interference unevenness is observed due to this unevenness.

[0102] It is considered that by controlling the curl within the specific range of the present invention, the shrinkage unevenness of the polarizer can be made uniform and the interference unevenness can be improved.

[0103] It is estimated that if the curl is too small, the influence of the contraction of the polarizer becomes large, so the interference unevenness becomes large, and if the curl is too large, the influence of the contraction of the functional layer becomes large.

[0104] In the present invention, from the viewpoint of interference unevenness, the range of the index (|(CHE1-CHE2)|×(d2 / d1)) of the present application corresponding to curl is preferably in the range of 0.30 to 1.00, and particularly preferably in the range of 0.40 to 0.70.

[0105] In addition, when the display device is provided, when the value of formula (1) is 2.00 or more, internal stress remains in the functional layer and optical unevenness is likely to occur. On the other hand, if the value of formula (1) is 0.20 or less, there is a problem with the moisture permeability of the functional layer, and drying unevenness is likely to occur, and wrinkles caused by drying unevenness may be visible, resulting in optical unevenness.

[0106] In addition, if the humidity expansion coefficient CHE of the laminated film as a whole is large, for example, when the laminated film is stored at high temperature in a roll state, the humidity expansion amount of the base film and the functional layer is large, so the difference in their humidity expansion amount is also likely to become large. As a result, interlayer delamination is likely to occur between the base layer and the base film, or the functional layer is deformed. If interlayer delamination occurs, the transport stability of the laminated film is likely to be reduced, and if the functional layer is deformed, the flatness of the functional layer is likely to be impaired, so the adhesion with the polarizer is also likely to be reduced.

[0107] In the present invention, it is preferred to reduce the humidity expansion coefficient CHE of the entire laminate film, because the humidity expansion amount of the entire laminate film under high humidity can be reduced, and thus the difference in humidity expansion amount between the substrate film and the functional layer can be reduced. Thus, during the period when the laminate film is stored at high temperature, the peeling and deformation of the functional layer can be suppressed, so that the adhesion with the polarizer can be improved without impairing the transport stability of the laminate film.

[0108] (Layer Structure of Laminated Film)

[0109] Figure 2 An example of the layer structure of the laminated film of the present invention is shown.

[0110] The laminated film 1 of the present invention comprises a substrate film 2 and a functional layer 3 on the substrate film 2. The substrate film 2 and the functional layer 3 may be formed by laminating a plurality of layers. In addition, the functional layer 3 may have other functional layers such as a primer layer (not shown) and a protective layer (not shown) on the surface or the back.

[0111] The base film 2 may have an adhesive layer or a pressure-sensitive adhesive layer (not shown) on the surface opposite to the functional layer. The adhesive layer or the pressure-sensitive adhesive layer can provide an adhesive function when the base film 2 and the display element are attached to each other.

[0112] Incidentally, the "peelable functional layer" in the present invention means that during normal production or general use, the substrate film and the functional layer are tightly attached and not easily peeled off. During polarizing plate processing, when it is desired to use only the functional layer, the functional layer can be peeled off from the substrate layer by external stress.

[0113] For example, regarding the stress when the substrate film is peeled off from the functional layer, the following state can be cited as an example: in a laminate film cut into a width of 25 mm and a length of 80 mm, the surface of the functional layer on the opposite side of the interface with the substrate film side is adhered to a glass substrate via an acrylic adhesive sheet for fixation, and then the substrate film at one end (the side with a width of 25 mm) of the test piece in the longitudinal direction is clamped using a tensile testing machine (RTF-1210 manufactured by A&D Co., Ltd.), and a 90° peel test (JIS K 6854-1:1999 "Adhesives-Peel Adhesion Strength Test Method-Part 1: 90 Degree Peel") is carried out at a crosshead speed (clamp movement speed) of 200 mm / min in an atmosphere of a temperature of 23°C and a humidity of 60% RH to evaluate the peel stress. When the substrate film and the functional layer can be peeled off at a stress of 0.05 to 2.00 N / 25 mm. If the stress is 0.05 N / 25 mm or more, peeling is unlikely to occur during the polarizing plate processing process, which is preferred, and if it is 2.00 N / 25 mm or less, the polarizing plate will not break when the base film is peeled off, which is preferred.

[0114] Hereinafter, the structure of the laminated film of the present invention will be described in detail.

[0115] 〔1〕Base film

[0116] The substrate film supports the functional layer and is not particularly limited as long as the difference in humidity expansion coefficient (|(CHE1-CHE2)|) at 23°C between the substrate film and the functional layer can be adjusted to satisfy the above formula (1). The substrate film usually includes a resin film.

[0117] Examples of the resin used include cellulose ester resins, cycloolefin resins, polypropylene resins, acrylic resins, polyester resins, polyarylate resins, and styrene resins or composite resins thereof. Among them, polyester resins are preferably used as resins having a moderately large coefficient of humidity expansion and which are easily controlled within the range of formula (1).

[0118] Examples of resin films include polyester resins (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.). Among them, polyester resin films including polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferred because it is easy to adjust the humidity expansion coefficient CHE of the laminated film at 23°C within the range of the above formula (1).

[0119] The resin film may be a heat-treated (heat-relaxed) resin film or a stretched resin film, and as described above, is suitable for controlling CHE.

[0120] Since the heat treatment reduces the residual stress of the resin film (e.g., residual stress associated with stretching, etc.), it can increase the humidity expansion coefficient CHE1 of the resin film and the substrate film. The heat treatment temperature is not particularly limited, and when the glass transition temperature of the resin constituting the resin film is set to Tg, it can be carried out at (Tg+60) to (Tg+180)°C.

[0121] The stretching treatment increases the residual stress of the resin film, thereby reducing the humidity expansion coefficient CHE1 of the resin film and then the substrate film. The stretching treatment is preferably performed in the biaxial direction of the resin film, for example. The stretching treatment can be performed under any conditions, for example, it can be performed at a stretching ratio of about 120 to 900%. Whether the resin film is stretched can be confirmed, for example, by whether it has an in-plane hysteresis axis (an axis extending in the direction in which the refractive index becomes the maximum). The stretching treatment can be performed before laminating the functional layer or after laminating, and it is preferably stretched before laminating.

[0122] As the polyester resin film (also simply referred to as a polyester film), a commercially available item can be used, and for example, polyethylene terephthalate film TN100 (manufactured by Toyobo Co., Ltd.) and MELINEX ST504 (manufactured by DuPont Teijin Films Co., Ltd.) can be preferably used.

[0123] The substrate film may further include a release layer provided on the surface of the resin film. The release layer can facilitate the peeling of the functional layer from the substrate film when producing the polarizing plate.

[0124] The release layer may contain a known release agent without particular limitation. Examples of the release agent contained in the release layer include silicone-based release agents and non-silicone-based release agents.

[0125] Examples of silicone-based release agents include well-known silicone-based resins. Examples of non-silicone-based release agents include long-chain alkyl side-chain polymers obtained by reacting long-chain alkyl isocyanates with polyvinyl alcohol or ethylene-vinyl alcohol copolymers, olefin-based resins (e.g., copolymerized polyethylene, cyclic polyolefins, polymethylpentene), polyarylate resins (e.g., polycondensates of aromatic dicarboxylic acid components and dihydric phenol components), fluororesins (e.g., polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), PFA (copolymer of tetrafluoroethylene and perfluoroalkoxyethylene), FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (copolymer of tetrafluoroethylene and ethylene)), etc.

[0126] The thickness of the release layer is not particularly limited as long as it can exhibit desired releasability, but is preferably 0.1 to 1.0 μm, for example.

[0127] Furthermore, if the humidity expansion coefficient of the base film itself at 23° C. is within the range of 10 to 20 ppm / %RH, warping is less likely to occur, which is preferred.

[0128] It is speculated that this is because if it is above 10ppm / %RH, the substrate film can follow the change of the polarizer caused by environmental changes, and as a result, it is speculated that the generation of poor appearance can be avoided. In addition, it is speculated that if it is below 20ppm / %RH, the substrate film itself can be prevented from humid expansion, and as a result, it is speculated that the generation of bending can be suppressed.

[0129] (thickness)

[0130] The total thickness of the laminated film of the present invention is 50 μm or less, preferably in the range of 30 to 45 μm. Although it is a thin film, it also requires a certain degree of strength (elasticity, rigidity) as a support, so the thickness d1 of the substrate film is preferably in the range of 15 to 45 μm, more preferably in the range of 20 to 40 μm.

[0131] 〔1.2〕Additives

[0132] 〈Plasticizers〉

[0133] The substrate film of the present invention may contain a plasticizer. The plasticizer is not particularly limited, but is preferably selected from polyol ester plasticizers, phthalate plasticizers, citric acid plasticizers, fatty acid ester plasticizers, phosphate plasticizers, polycarboxylic acid ester plasticizers, polyester plasticizers, and the like.

[0134] 〈Ultraviolet absorber〉

[0135] The substrate film of the present invention may also contain an ultraviolet absorber. As the ultraviolet absorber used, there can be cited ultraviolet absorbers of benzotriazole, 2-hydroxybenzophenone or phenyl salicylate. For example, triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone can be illustrated.

[0136] 〈Antioxidants〉

[0137] The base film of the present invention may contain an antioxidant. An antioxidant is also called an anti-degradation agent.

[0138] The antioxidant is preferably contained in the base film because it has a function of delaying or preventing the decomposition of the base film due to, for example, halogens contained in the residual solvent in the base film, phosphoric acid in the phosphoric acid-based plasticizer, and the like.

[0139] As such an antioxidant, it is preferable to use a hindered phenol compound, for example, 2,6-di-tert-butyl-p-cresol, pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate].

[0140] <particle>

[0141] The base film of the present invention also preferably contains fine particles.

[0142] As the microparticles used in the present invention, as examples of inorganic compounds, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, water and calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate can be cited. In addition, microparticles of organic compounds can also be preferably used. As examples of organic compounds, polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resins, silicone resins, polycarbonate resins, benzoguanamine resins, melamine resins, polyolefin powders, polyester resins, polyamide resins, polyimide resins, or crushed and classified organic polymer compounds such as polyfluoroethylene resins and starch, and polymer compounds synthesized by suspension polymerization can be used.

[0143] From the perspective of reducing turbidity, the fine particles preferably contain silicon, and particularly preferably silicon dioxide, for example, which are commercially available under the trade names of Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (all manufactured by Nippon Aerosil Co., Ltd.) and can be used.

[0144] 〔1.3〕Method for producing substrate film

[0145] As the manufacturing method of the substrate film of the present invention, the conventional manufacturing methods such as inflation method, T-die method, calendaring method, cutting method, casting method, emulsification method, hot pressing method can be used. From the viewpoint of suppressing coloration, suppressing foreign matter defects, suppressing optical defects such as die lines, etc., the film-making method is preferably a solution casting method and a melt casting method. If it is a solution casting method, the temperature in the processing step is low, so it can be given high functionality by using various additives. In addition, in the solution casting method, in order to adjust CHE1, the content of the residual solvent of the substrate film can also be controlled.

[0146] Hereinafter, the "solution casting method" will be described.

[0147] 〈Solution Casting Method〉

[0148] In the case of film formation by solution casting, the method for manufacturing the substrate film of the present invention preferably includes the following steps: a step of preparing a slurry by dissolving and dispersing the thermoplastic resin and the additives such as the above-mentioned microparticles in a solvent (dissolution step; slurry preparation step); a step of casting the slurry onto a continuously moving annular metal support (casting step); a step of drying the cast slurry into a web (solvent evaporation step); a step of peeling off the metal support (peeling step); a step of drying, stretching, and maintaining the width (stretching, maintaining the width, and drying step); and a step of winding the finished film into a roll (winding step). The solvent used in the slurry preparation step of the solution casting method can be appropriately selected from the solvent used in the formation of the functional layer described later.

[0149] It should be noted that the content of the residual solvent of the net at the moment of peeling the above-mentioned net (hereinafter, also referred to as "residual solvent amount") can be appropriately adjusted according to the strength of the drying conditions, the length of the metal support, etc. In order to make the film show good planarity, the residual solvent amount when peeling the net from the metal support is preferably 10 to 150% by mass. When peeling at the moment when the residual solvent amount is more, if the net is too soft, the planarity is damaged when peeling, and it is easy to produce surface unevenness and longitudinal stripes caused by the peeling tension. Therefore, the residual solvent amount when peeling is determined by taking into account economic speed and quality. It is further preferably 10 to 40% by mass or 60 to 130% by mass, and particularly preferably 10 to 30% by mass or 70 to 120% by mass.

[0150] In the present invention, the residual solvent amount of the base film is defined by the following formula.

[0151] Residual solvent amount (mass %) = [(MN) / N] × 100

[0152] It should be noted that M is the mass of a sample taken at any time during or after the production of the web or film, and N is the mass of M after heating it at 115° C. for 1 hour. It should be noted that the residual solvent type is the type of solvent basically used and can be appropriately measured and identified by gas chromatography or the like.

[0153] In the drying, stretching, and width holding steps, the film is generally dried by a roller drying method (a method in which a plurality of rollers arranged above and below are alternately passed through a web for drying) or a method in which the web is dried while being transported by a tentering method. For example, after peeling, the web is dried by using a drying device in which a plurality of rollers arranged in a drying device are alternately passed through the web for transportation and / or a tentering stretching device in which both ends of the web are clamped and transported by a clamp.

[0154] The means for drying the web is not particularly limited, and generally, it can be carried out by hot air, infrared rays, heating rolls, microwaves, etc. From the viewpoint of simplicity, hot air is preferably used.

[0155] The web is preferably stretched in at least one direction. By stretching, the orientation of molecules in the film can be controlled. In particular, by biaxial stretching as described below, the anisotropy of CHE1 is eliminated and the generation of unevenness can be suppressed.

[0156] As a specific stretching method, the long side direction of the net (film making direction; casting direction; MD direction) and the direction orthogonal to the net surface, that is, the width direction (TD direction) can be biaxially stretched or uniaxially stretched successively or simultaneously. Preferably, the biaxially stretched film obtained by biaxially stretching the casting direction (MD direction) and the width direction (TD direction) can be implemented. It should be noted that the stretching operation can be implemented in multiple stages. In addition, when biaxially stretching is performed, biaxial stretching can be performed simultaneously or in stages. In addition, the simultaneous biaxial stretching also includes stretching in one direction to relax the tension of the other party for contraction.

[0157] The stretching ratios in the mutually orthogonal biaxial directions are preferably 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, and more preferably 0.8 to 1.2 times in the casting direction and 1.2 to 2.0 times in the width direction.

[0158] The stretching temperature is usually preferably in the temperature range of Tg of the resin constituting the film to Tg+60° C. Usually, the stretching temperature is preferably 120° C. to 200° C., more preferably 120° C. to 180° C.

[0159] The amount of residual solvent in the web during stretching is preferably 0 to 20% by mass, and more preferably 0 to 15% by mass.

[0160] The method of stretching the web is not particularly limited. For example, there can be cited a method of adding a peripheral speed difference to multiple rollers, and stretching in the longitudinal direction by using the peripheral speed difference of the rollers; a method of fixing the two ends of the web with clamps and pins, expanding the interval between the clamps and pins in the forward direction, and stretching in the longitudinal direction; a method of similarly expanding in the transverse direction and stretching in the transverse direction; or a method of expanding in both the longitudinal and transverse directions and stretching in both the longitudinal and transverse directions, etc. Of course, these methods can also be used in combination. Among them, it is particularly preferred to use a tentering machine method that holds the two ends of the web with clamps or the like to stretch in the width direction (transverse direction). These width maintenance or transverse stretching in the film-making process are preferably performed using a tentering machine, and can also be a pin plate tentering machine or a cloth clip tentering machine.

[0161] The substrate film of the present invention can obtain the same effect even if it is heat-relaxed in addition to stretching. The heat-relaxation temperature is usually preferably carried out in the temperature range of Tg to Tg+60°C of the resin constituting the film. Usually, the heat-relaxation temperature is preferably 120°C to 200°C, and more preferably 120°C to 180°C.

[0162] Next, the film is wound into a roll through a winding process. The film winding method can be performed by using a generally used method, such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, etc. These methods can be used separately.

[0163] The substrate film of the present invention is preferably a long film, specifically, a film of about 100 m to 10000 m, usually provided in a roll form. The longer the film length, the more can be produced in one production, so it is preferred. It should be noted that from the perspective of transportability and operability, it is required to be in a compact roll form, so the thinner the total film thickness of the laminated film, the more preferred.

[0164] 〔2〕Functional layer

[0165] The functional layer of the present invention is bonded to a polarizer after being peeled off from the substrate film, or bonded to a polarizer and then peeled off to form a polarizing plate, and can function as an optical film such as a polarizing plate protective film or a retardation film.

[0166] From the viewpoint of providing a film polarizing plate while suppressing wrinkles and curling deformation of the functional layer as a film, the thickness of the functional layer of the present invention is preferably in the range of 1 to 19 μm, more preferably in the range of 2 to 10 μm.

[0167] 〔2.1〕Resin

[0168] The resin used in the functional layer of the present invention is not particularly limited, but from the aspect of controlling the humidity expansion coefficient, it is preferably a linear polymer material having a carbonyl group in the side chain, or a polymer material having a cyclic structure in the main chain. Therefore, as a preferred resin, it can be a cycloolefin resin, a fumaric acid diester resin, a (meth) acrylic resin, or a styrene (meth) acrylic ester copolymer.

[0169] 〈Cycloolefin resin〉

[0170] The cycloolefin-based resin used in the functional layer is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and a copolymerizable monomer other than the cycloolefin monomer.

[0171] The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[0172]

[0173] In the general formula (A-1), R 1 ~R 4 Each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group. p represents an integer of 0 to 2. 1 ~R 4 All the different R 1 and R 2 Not at the same time representing hydrogen atoms, R 3 and R 4 It does not represent hydrogen atoms at the same time.

[0174] In the general formula (A-1), R 1 ~R 4 The hydrocarbon group having 1 to 30 carbon atoms represented by is preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom. Examples of such a linking group include bivalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0175] In the general formula (A-1), R1 ~R 4 Examples of polar groups represented by include carboxyl, hydroxyl, alkoxy, alkoxycarbonyl, aryloxycarbonyl, amino, amide and cyano. Among them, carboxyl, hydroxyl, alkoxycarbonyl and aryloxycarbonyl are preferred, and alkoxycarbonyl and aryloxycarbonyl are preferred from the viewpoint of ensuring solubility during film formation of the solution.

[0176] From the viewpoint of improving the heat resistance of the optical film, p in the general formula (A-1) is preferably 1 or 2. This is because if p is 1 or 2, the volume of the obtained polymer becomes larger and the glass transition temperature is easily increased. In addition, it also has the advantage of being able to slightly respond to humidity and easily controlling the curling balance as a laminate.

[0177]

[0178] In the general formula (A-2), R 5 represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. 6 represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0-2.

[0179] R in the general formula (A-2) 5 It preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

[0180] R in the general formula (A-2) 6 Preferably, it represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, and an aryloxycarbonyl group. From the viewpoint of ensuring solubility during film formation from a solution, an alkoxycarbonyl group and an aryloxycarbonyl group are more preferred.

[0181] From the viewpoint of improving the heat resistance of the optical film, p in the general formula (A-2) preferably represents 1 or 2. This is because when p represents 1 or 2, the volume of the obtained polymer becomes large and the glass transition temperature tends to increase.

[0182] From the viewpoint of improving solubility in organic solvents, cycloolefin monomers having a structure represented by general formula (A-2) are preferred. Generally speaking, organic compounds have reduced crystallinity by destroying symmetry, and thus their solubility in organic solvents is improved. 5 and R 6 Since the ring-constituting carbon atom is substituted only on one side with respect to the molecular symmetry axis, the molecular symmetry is low, that is, the cycloolefin monomer having the structure represented by the general formula (A-2) has high solubility and is therefore suitable for producing an optical film by a solution casting method.

[0183] The content ratio of the cycloolefin monomer having a structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer can be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin resin. If a certain amount or more of the cycloolefin monomer having a structure represented by the general formula (A-2) is contained, the orientation of the resin is improved, so the phase difference (retardation) value is likely to increase.

[0184] Specific examples of the cycloolefin monomer having a structure represented by the general formula (A-1) are shown in Exemplary Compounds 1 to 14, and specific examples of the cycloolefin monomer having a structure represented by the general formula (A-2) are shown in Exemplary Compounds 15 to 34.

[0185]

[0186] Examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer and a copolymerizable monomer capable of addition copolymerization with the cycloolefin monomer.

[0187] Examples of the copolymerizable monomer capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0188] Examples of copolymerizable monomers capable of addition copolymerization include compounds containing unsaturated double bonds, vinyl cyclic hydrocarbon monomers, and (meth)acrylates. Examples of compounds containing unsaturated double bonds include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), examples of which include ethylene, propylene, and butene. Examples of vinyl cyclic hydrocarbon monomers include vinyl cyclopentene monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0189] The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer may be, for example, 20 to 80 mol %, preferably 30 to 70 mol % based on the total of all monomers constituting the copolymer.

[0190] As described above, the cycloolefin resin is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2), and examples thereof include the following.

[0191] 1) Ring-opening polymers of cycloolefin monomers

[0192] 2) Ring-opening copolymers of cycloolefin monomers and copolymerizable monomers capable of ring-opening copolymerization therewith

[0193] 3) Hydrogenated product of the ring-opening (co)polymer of 1) or 2) above

[0194] 4) A (co)polymer obtained by cyclizing the ring-opening (co)polymer of 1) or 2) by Friedel-Crafts reaction and then hydrogenating the ring-opening (co)polymer

[0195] 5) Saturated copolymers of cycloolefin monomers and compounds containing unsaturated double bonds

[0196] 6) Addition copolymers of cycloolefin monomers and vinyl cyclic hydrocarbon monomers and hydrogenated products thereof

[0197] 7) Alternating copolymers of cycloolefin monomers and (meth)acrylates

[0198] The polymers of 1) to 7) above can be obtained by a known method, for example, the method described in Japanese Patent Application Laid-Open No. 2008-107534 and Japanese Patent Application Laid-Open No. 2005-227606. For example, the catalyst and solvent used in the ring-opening copolymerization of 2) above can be the catalysts and solvents described in paragraphs 0019 to 0024 of Japanese Patent Application Laid-Open No. 2008-107534. The catalyst used in the hydrogenation of 3) and 6) above can be the catalysts described in paragraphs 0025 to 0028 of Japanese Patent Application Laid-Open No. 2008-107534. The acidic compound used in the Friedel-Crafts reaction of 4) above can be the acidic compound described in paragraph 0029 of Japanese Patent Application Laid-Open No. 2008-107534. The catalyst used in the addition polymerization of 5) to 7) above can be the catalysts described in paragraphs 0058 to 0063 of Japanese Patent Application Laid-Open No. 2005-227606. The alternating copolymerization reaction of 7) can be carried out by the method described in, for example, JP-A-2005-227606 Nos. 0071 and 0072.

[0199] Among them, the polymers of 1) to 3) and 5) are preferred, and the polymers of 3) and 5) are more preferred. That is, from the perspective of being able to increase the glass transition temperature of the obtained cycloolefin resin and to increase the light transmittance, the cycloolefin resin preferably contains at least one of the structural unit represented by the following general formula (B-1) and the structural unit represented by the following general formula (B-2), and more preferably contains only the structural unit represented by the general formula (B-2), or contains both the structural unit represented by the general formula (B-1) and the structural unit represented by the general formula (B-2). The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-1), and the structural unit represented by the general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the general formula (A-2).

[0200]

[0201] In the general formula (B-1), X represents -CH=CH- or -CH2CH2-. 1 ~R 4 and p are respectively the same as R 1 ~R 4 Has the same meaning as p.

[0202]

[0203] In the general formula (B-2), X represents -CH=CH- or -CH2CH2-. 5 ~R 6 and p are respectively the same as R 5 ~R 6 Has the same meaning as p.

[0204] The cycloolefin resin of the present invention may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (eg, G7810), Arton F, Arton R (eg, R4500, R4900, and R5000), and Arton RX (eg, RX4500) manufactured by JSR Corporation.

[0205] The intrinsic viscosity of the cycloolefin resin (η) inh is preferably 0.2 to 5 cm 3 / g, more preferably 0.3 to 3 cm 3 / g, more preferably 0.4 to 1.5 cm 3 / g.

[0206] The number average molecular weight (Mn) of the cycloolefin resin is preferably 8,000 to 100,000, more preferably 10,000 to 80,000, and further preferably 12,000 to 50,000. The weight average molecular weight (Mw) of the cycloolefin resin is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and further preferably 40,000 to 200,000. The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0207] <Gel Permeation Chromatography>

[0208] Solvent: dichloromethane

[0209] Column: Shodex K806, K805, K803G (three columns made by Showa Denko K.K. connected and used)

[0210] Column temperature: 25°C

[0211] Sample concentration: 0.1 mass%

[0212] Detector: RI Model 504 (manufactured by GLScience)

[0213] Pump: L6000 (manufactured by Hitachi, Ltd.)

[0214] Flow rate: 1.0mL / min

[0215] Calibration curve: A calibration curve based on 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) in the range of Mw=500 to 2800000 is used. The 13 samples are preferably used at substantially equal intervals.

[0216] When the intrinsic viscosity [η]inh, the number average molecular weight and the weight average molecular weight are within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties and molding processability as a functional layer.

[0217] The glass transition temperature (Tg) of the cycloolefin resin is usually 110°C or higher, preferably 110 to 350°C, more preferably 120 to 250°C, and even more preferably 120 to 220°C. If Tg is 110°C or higher, deformation under high temperature conditions is easily suppressed. On the other hand, if Tg is 350°C or lower, molding is easy, and degradation of the resin due to heat during molding is also easily suppressed.

[0218] The content of the cycloolefin-based resin is preferably 70% by mass or more, more preferably 80% by mass or more, based on the functional layer.

[0219] 〈Fumaric acid diester resin〉

[0220] The fumaric acid diester-based resin used in the functional layer is a fumaric acid diester-based resin containing a diisopropyl fumarate residue unit and a fumaric acid diester residue unit having an alkyl group having 1 or 2 carbon atoms.

[0221] Here, the alkyl groups with 1 or 2 carbon atoms in the fumaric acid diester residue unit having an alkyl group with 1 or 2 carbon atoms are each independent, and examples thereof include methyl and ethyl. In addition, they may also be substituted with halogen groups such as fluorine and chlorine; ether groups; ester groups or amino groups. As examples of the fumaric acid diester residue unit having an alkyl group with 1 or 2 carbon atoms, dimethyl fumarate residue units and diethyl fumarate residue units may be mentioned. In addition, they may include one or more types.

[0222] Specific examples of the fumaric acid diester-based resin include diisopropyl fumarate / dimethyl fumarate copolymer resins and diisopropyl fumarate / diethyl fumarate copolymer resins.

[0223] The above-mentioned fumaric acid diester resin may also contain other monomer residue units as long as it does not exceed the scope of the present invention. Examples of other monomer residue units include styrene residue units such as styrene residue units and α-methylstyrene residue units; (meth)acrylic acid residue units; (meth)acrylic acid ester residue units such as methyl (meth)acrylate residue units, ethyl (meth)acrylate residue units, and butyl (meth)acrylate residue units; vinyl ester residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylonitrile residue units; methacryloyl residue units; Vinyl ether residue units such as methyl vinyl ether residue units, ethyl vinyl ether residue units, and butyl vinyl ether residue units; N-substituted maleimide residue units such as N-methylmaleimide residue units, N-cyclohexylmaleimide residue units, and N-phenylmaleimide residue units; olefin residue units such as ethylene residue units and propylene residue units; or fumaric acid diester residues other than the above-mentioned fumaric acid diester residue units such as di-n-butyl fumarate residue units and bis(2-ethylhexyl) fumarate residue units, and one or more of cinnamic acid and cinnamic acid ester units.

[0224] The mixing ratio of the fumaric acid diester resin used in the present invention is preferably 50 to 99 mol % of diisopropyl fumarate residue units and 1 to 50 mol % of fumaric acid diester residue units having an alkyl group with 1 or 2 carbon atoms. From the perspective of excellent phase difference characteristics and strength when a phase difference film is prepared, a fumaric acid diester resin composed of 60 to 95 mol % of diisopropyl fumarate residue units and 5 to 40 mol % of fumaric acid diester residue units having an alkyl group with 1 or 2 carbon atoms is particularly preferred.

[0225] The fumaric acid diester resin used in the present invention preferably has a number average molecular weight in the range of 50,000 to 250,000 in terms of standard polystyrene obtained from an elution curve measured by the gel permeation chromatography.

[0226] (Synthesis Example of Fumaric Acid Diester Resin)

[0227] In a 1L autoclave equipped with a stirrer, a cooling tube, a nitrogen introduction tube and a thermometer, 2g of hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metolose 60SH-50), 600g of distilled water, 330g of diisopropyl fumarate, 70g of diethyl fumarate and 3g of tert-butyl peroxypivalate as a polymerization initiator were placed, and nitrogen bubbling was performed for 1 hour, and then the mixture was kept at 50°C for 24 hours while stirring at 400 rpm to perform free radical suspension polymerization. After cooling to room temperature, the suspension containing the generated polymer particles was filtered and washed with distilled water and methanol to obtain a fumaric acid diester resin (yield: 75%).

[0228] The number average molecular weight of the obtained fumaric acid diester-based resin was 120000. In addition, the resin composition was confirmed to be diisopropyl fumarate residue unit / diethyl fumarate residue unit=84 / 16 (mol %) by 1H-NMR measurement.

[0229] 〈(Meth)acrylic resin〉

[0230] The (meth) acrylic resin used in the functional layer preferably contains at least a structural unit (U1) derived from methyl methacrylate and a structural unit (U2) derived from phenylmaleimide. The (meth) acrylic resin containing the structural unit (U2) derived from phenylmaleimide can reduce the humidity expansion coefficient CHE2 of the functional layer. In addition, the photoelastic coefficient is also small, and even if it expands due to moisture absorption, it is not easy to produce unevenness.

[0231] The (meth)acrylic resin may further contain other structural units other than those mentioned above. Examples of such other structural units include (meth)acrylic acid alkyl esters such as adamantyl acrylate; (meth)acrylic acid cycloalkyl esters such as 2-ethylhexyl acrylate, etc. Among them, from the viewpoint of reducing the deterioration of brittleness caused by the structural unit (U2) derived from phenylmaleimide, it is preferred to further contain a structural unit (U3) derived from an alkyl acrylate.

[0232] That is, the (meth)acrylic resin more preferably includes a structural unit (U1) derived from methyl methacrylate, a structural unit (U2) derived from phenylmaleimide, and a structural unit (U3) derived from an alkyl acrylate.

[0233] The content of the structural unit (U1) derived from methyl methacrylate is preferably 50 to 95% by mass, more preferably 70 to 90% by mass, based on all the structural units constituting the (meth)acrylic resin.

[0234] The structural unit (U2) derived from phenylmaleimide has a relatively rigid structure, and thus can reduce the humidity expansion coefficient CHE2 of the functional layer. In addition, since the structural unit (U2) derived from phenylmaleimide has a relatively high volume structure, it can have micro-voids in the resin matrix that allow the rubber particles to move, and thus can make the rubber particles easily unevenly present in the surface layer of the functional layer.

[0235] The content of the structural unit (U2) from phenylmaleimide is preferably 1 to 25% by mass relative to all the structural units constituting the (meth) acrylic resin. If the content of the structural unit (U2) from phenylmaleimide is 1% by mass or more, it is easy to reduce the humidity expansion coefficient CHE2 of the functional layer at 23°C, and if it is 25% by mass or less, the brittleness of the functional layer is not easily excessively damaged. From the above viewpoint, the content of the structural unit (U2) from phenylmaleimide is more preferably 7 to 15% by mass.

[0236] The structural unit (U3) derived from an alkyl acrylate can impart appropriate flexibility to the resin, and thus can improve the brittleness caused by, for example, the structural unit (U2) derived from phenylmaleimide.

[0237] The alkyl acrylate preferably has an alkyl moiety with carbon atoms of 1 to 7, preferably 1 to 5. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate and the like.

[0238] The content of the structural unit (U3) derived from an alkyl acrylate is preferably 1 to 25% by mass relative to all the structural units constituting the (meth) acrylic resin. If the content of the structural unit (U3) derived from an alkyl acrylate is 1% by mass or more, it is possible to impart appropriate flexibility to the (meth) acrylic resin, so that the functional layer will not become too brittle and will not break easily. If the content of the structural unit (U3) derived from an alkyl acrylate is 25% by mass or less, the Tg of the functional layer will not become too low, and the coefficient of humidity expansion (CHE2) at 23° C. will not become too large. From the above viewpoints, the content of the structural unit (U3) derived from an alkyl acrylate is more preferably 5 to 15% by mass.

[0239] The ratio of the structural unit (U2) derived from phenylmaleimide to the total amount of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from alkyl acrylate is preferably 20 to 70% by mass. If the ratio is 20% by mass or more, the tensile modulus G2 of the functional layer is easily increased, and if it is 70% by mass or less, the functional layer will not become too brittle.

[0240] The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 100° C. or higher, more preferably 120 to 150° C. If the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the functional layer can be easily improved. In order to adjust the Tg of the (meth)acrylic resin, it is preferred to adjust the content of the structural unit (U2) derived from phenylmaleimide and the structural unit (U3) derived from alkyl acrylate.

[0241] The weight average molecular weight (Mw) of the (meth)acrylic resin is not particularly limited and can be adjusted according to the purpose. For example, from the viewpoint of promoting the entanglement of resin molecules to improve the toughness of the functional layer and making it less likely to break, and from the viewpoint of appropriately increasing the CHE ratio and easily adjusting the curling amount to a preferred degree for adhesion, the weight average molecular weight of the (meth)acrylic resin is preferably 100,000 or more, and more preferably 1,000,000 or more. If the weight average molecular weight of the (meth)acrylic resin is 1,000,000 or more, the toughness of the obtained functional layer can be improved. Therefore, when conveying to the laminated film, the breakage of the functional layer due to conveying tension can be suppressed, and the conveying stability can be improved. From the same viewpoint, the weight average molecular weight of the (meth)acrylic resin is further preferably 1.5 million to 3,000,000. The method for determining the weight average molecular weight is as described above.

[0242] 〈Styrene-(meth)acrylate copolymer〉

[0243] Styrene (meth) acrylate copolymer (hereinafter also referred to as styrene acrylic resin) has excellent transparency when used in the functional layer. In addition, the hygroscopic expansion coefficient can be adjusted by the copolymerization ratio of the styrene part, so the curling of the laminate can be controlled by changing these ratios.

[0244] The styrene-acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylate monomer. The styrene monomer includes styrene represented by the structural formula CH2=CH-C6H5 and styrene derivatives having a known side chain or functional group in the styrene structure.

[0245] In addition, the (meth)acrylate monomer includes, in addition to acrylates and methacrylates represented by CH(R1)=CHCOOR2 (R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 24 carbon atoms), acrylate derivatives and methacrylate derivatives having known side chains and functional groups in the structures of these esters.

[0246] Examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, and p-n-dodecylstyrene.

[0247] Examples of the (meth)acrylate monomers include acrylate monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate (2EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylate.

[0248] It should be noted that in this specification, "(meth)acrylate monomer" is a general term for "acrylate monomer" and "methacrylate monomer", and refers to one or both of them. For example, "methyl (meth)acrylate" refers to one or both of "methyl acrylate" and "methyl methacrylate".

[0249] The (meth)acrylate monomer may be one or more, for example, a copolymer formed by using a styrene monomer and two or more acrylate monomers, a copolymer formed by using a styrene monomer and two or more methacrylate monomers, or a copolymer formed by using a styrene monomer, an acrylate monomer, and a methacrylate monomer.

[0250] The weight average molecular weight (Mw) of the styrene acrylic resin is preferably in the range of 5,000 to 150,000, more preferably in the range of 10,000 to 70,000, from the viewpoint of facilitating control of plasticity.

[0251] The styrene-acrylic resin of the present invention may be a commercially available product, and an example thereof is MS resin "TX320XL" manufactured by Denka Corporation.

[0252] 〈Polyarylate resin〉

[0253] The polyarylate resin has excellent toughness when used in a functional layer. The polyarylate resin contains at least a constituent unit derived from an aromatic diol and a constituent unit derived from an aromatic dicarboxylic acid.

[0254] The polyarylate-based resin of the present invention may be a commercially available product, and as an example, PAR resin "U-100" manufactured by Unitika Co., Ltd. having a weight average molecular weight (Mw) of 100,000 may be mentioned.

[0255] 〔2.2〕Additives

[0256] The functional layer may further contain other components other than the above as needed. Examples of other components include rubber particles, the above-mentioned matting agent (microparticles), plasticizers, ultraviolet absorbers, etc. Among them, rubber particles and plasticizers can also be used as a means of controlling the humidity expansion coefficient CHE of the functional layer by imparting hydrophobicity to the film, so the curling characteristics of the laminate can be controlled by appropriately adjusting the material and the amount of addition. In addition, from the viewpoint of imparting toughness (softness) to the functional layer, it is preferred to further contain rubber particles.

[0257] 〈Rubber particles〉

[0258] The rubber particles are particles containing a rubber-like polymer. The rubber-like polymer is a soft cross-linked polymer having a glass transition temperature of 20° C. or less. Examples of such cross-linked polymers include butadiene-based cross-linked polymers, (meth)acrylic cross-linked polymers, and organosiloxane cross-linked polymers. Among them, from the viewpoint that the refractive index difference with the (meth)acrylic resin is small and the transparency of the functional layer is not easily damaged, preferably a (meth)acrylic cross-linked polymer, more preferably an acrylic cross-linked polymer (acrylic rubber-like polymer).

[0259] That is, the rubber particles are preferably particles containing an acrylic rubber-like polymer (a).

[0260] For the acrylic rubber-like polymer (a):

[0261] The acrylic rubber polymer (a) is a cross-linked polymer containing a structural unit derived from acrylic ester as a main component. The term "containing as a main component" means that the content of the structural unit derived from acrylic ester falls within the range described below. The acrylic rubber polymer (a) is preferably a cross-linked polymer containing a structural unit derived from acrylic ester, a structural unit derived from other monomers copolymerizable therewith, and a structural unit derived from a multifunctional monomer having two or more free radical polymerizable groups (non-conjugated reactive double bonds) in one molecule.

[0262] The acrylic acid ester is preferably an acrylic acid alkyl ester having an alkyl group with 1 to 12 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. The acrylic acid ester may be one kind or two or more kinds.

[0263] The content of the structural unit derived from acrylate is preferably 40 to 80% by mass, more preferably 50 to 80% by mass, based on the total structural units constituting the acrylic rubber polymer (a1). When the content of acrylate is within the above range, sufficient toughness can be easily imparted to the protective film.

[0264] The other monomers that can be copolymerized are monomers other than the multifunctional monomers among the monomers that can be copolymerized with the acrylic acid ester. That is, the monomers that can be copolymerized do not have more than two free radical polymerizable groups. Examples of monomers that can be copolymerized include methacrylates such as methyl methacrylate; styrenes such as styrene and methyl styrene; (meth) acrylonitriles; (meth) acrylamides; (meth) acrylic acid. Among them, the other monomers that can be copolymerized preferably include styrenes. The other monomers that can be copolymerized may be one or more.

[0265] The content of the structural unit derived from other copolymerizable monomers is preferably 5 to 55% by mass, more preferably 10 to 45% by mass, based on the total structural units constituting the acrylic rubber-like polymer (a).

[0266] Examples of the multifunctional monomer include allyl (meth)acrylate, triallyl cyanurate, triallyl isocyanate, diallyl phthalate, diallyl maleate, hexadivinyl acid, divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol (meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate.

[0267] The content of the structural unit derived from the multifunctional monomer is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass, relative to the total structural units constituting the acrylic rubber polymer (a). If the content of the multifunctional monomer is 0.05% by mass or more, it is easy to increase the degree of crosslinking of the obtained acrylic rubber polymer (a), so the hardness and rigidity of the obtained functional layer will not be too impaired. If it is 10% by mass or less, the toughness of the functional layer is not easily impaired.

[0268] The monomer components constituting the acrylic rubber-like polymer (a) can be measured, for example, by the peak area ratio detected by thermal decomposition GC-MS.

[0269] The glass transition temperature (Tg) of the rubbery polymer is preferably 0° C. or lower, more preferably -10° C. or lower. If the glass transition temperature (Tg) of the rubbery polymer is 0° C. or lower, appropriate toughness can be imparted to the film. The glass transition temperature (Tg) of the rubbery polymer can be measured by the same method as described above.

[0270] The glass transition temperature (Tg) of the rubber polymer can be adjusted by the composition of the rubber polymer. For example, in order to lower the glass transition temperature (Tg) of the acrylic rubber polymer (a), it is preferred to increase the mass ratio of the acrylic acid ester having an alkyl group with 4 or more carbon atoms / other copolymerizable monomers in the acrylic rubber polymer (a) (for example, to 3 or more, preferably 4 to 10).

[0271] The particles containing the acrylic rubber polymer (a) may be particles composed of the acrylic rubber polymer (a), or particles having a hard layer composed of a hard cross-linked polymer (c) having a glass transition temperature of 20°C or higher and a soft layer composed of the acrylic rubber polymer (a) disposed around the hard layer (these are also referred to as "elastomers"); or particles composed of an acrylic graft copolymer obtained by polymerizing a mixture of monomers such as methacrylate in the presence of the acrylic rubber polymer (a) by at least one stage. The particles composed of the acrylic graft copolymer may be core-shell type particles having a core portion containing the acrylic rubber polymer (a) and a shell portion covering the core portion.

[0272] For core-shell rubber particles containing an acrylic rubber-like polymer:

[0273] (Nuclear Department)

[0274] The core part includes an acrylic rubber polymer (a) and may further include a hard cross-linked polymer (c) as required. That is, the core part may have a soft layer composed of an acrylic rubber polymer and a hard layer composed of a hard cross-linked polymer (c) disposed inside the soft layer.

[0275] The crosslinked polymer (c) may be a crosslinked polymer containing methacrylic acid ester as a main component. That is, the crosslinked polymer (c) preferably comprises a structural unit derived from alkyl methacrylate, a structural unit derived from other monomers copolymerizable therewith, and a structural unit derived from a polyfunctional monomer.

[0276] The alkyl methacrylate may be the above-mentioned alkyl methacrylate; the other copolymerizable monomers may be the above-mentioned styrenes, acrylates, etc.; and the polyfunctional monomers may be the same monomers as those listed above as the polyfunctional monomers.

[0277] The content of the structural unit derived from the alkyl methacrylate can be 40 to 100% by mass relative to the total structural units constituting the crosslinked polymer (c). The content of the structural unit derived from other copolymerizable monomers can be 60 to 0% by mass relative to the total structural units constituting other crosslinked polymers (c). The content of the structural unit derived from the multifunctional monomer can be 0.01 to 10% by mass relative to the total structural units constituting other crosslinked polymers.

[0278] (Shell)

[0279] The shell portion includes a methacrylic polymer (b) (other polymer) graft-bonded to the acrylic rubber polymer (a) and including a structural unit derived from methacrylic acid ester as a main component. The main component means that the content of the structural unit derived from methacrylic acid ester is within the range described below.

[0280] The methacrylic acid ester constituting the methacrylic polymer (b) is preferably an alkyl methacrylate such as methyl methacrylate, wherein the alkyl group has 1 to 12 carbon atoms. The methacrylic acid ester may be one kind or two or more kinds.

[0281] The content of methacrylate is preferably 50% by mass or more relative to the total structural units constituting the methacrylic polymer (b). If the content of methacrylate is 50% by mass or more, compatibility with a methacrylic resin containing a structural unit derived from methyl methacrylate as a main component is easily obtained. From the above viewpoints, the content of methacrylate is more preferably 70% by mass or more relative to the total structural units constituting the methacrylic polymer (b).

[0282] The methacrylic polymer (b) may further contain structural units derived from other monomers copolymerizable with methacrylic acid ester. Examples of other copolymerizable monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, and n-butyl acrylate; (meth)acrylic acid monomers having alicyclic, heterocyclic, or aromatic rings (ring-containing (meth)acrylic acid monomers) such as benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0283] The content of the structural unit derived from the copolymerizable monomer is preferably 50% by mass or less, more preferably 30% by mass or less, based on the total structural units constituting the methacrylic polymer (b).

[0284] In this embodiment, since the functional layer is not stretched, the shape of the rubber particles can be approximately a true sphere. That is, the aspect ratio of the rubber particles when observing the cross section or surface of the functional layer can be about 1 to 2.

[0285] The average particle size of the rubber particles is preferably 100 to 400 nm. If the average particle size of the rubber particles is 100 nm or more, it is easy to give sufficient toughness and stress relaxation to the functional layer, and if it is 400 nm or less, the transparency of the functional layer is not easily impaired. From the same point of view, the average particle size of the rubber particles is more preferably 150 to 300 nm.

[0286] The average particle size of the rubber particles can be calculated by the following method.

[0287] The average particle size of the rubber particles can be measured as the average value of the equivalent circle diameters of 100 particles obtained by SEM or TEM photography of the surface or slice of the laminated film. The equivalent circle diameter can be obtained by converting the projected area of ​​the particles obtained by photography into the diameter of a circle having the same area. In this case, the rubber particles observed by SEM observation and / or TEM observation at a magnification of 5000 times are used for calculation of the average particle size.

[0288] The content of the rubber particles is not particularly limited, but is preferably 5 to 40% by mass, more preferably 7 to 30% by mass, based on the functional layer.

[0289] 〔2.3〕Physical properties

[0290] 〈Humidity Expansion Coefficient at 23°C (CHE2)〉

[0291] Based on the relationship with the preferred humidity expansion coefficient (CHE1) of the substrate film, and from the viewpoint of controlling the direction and degree of curling, the humidity expansion coefficient (CHE2) of the functional layer at 23°C is preferably in the range of 1 to 30 ppm / %RH. If the humidity expansion coefficient CHE2 of the functional layer is 1 ppm or more, the peeling process after lamination is easy to perform, and if it is 30 ppm or less, the effect of suppressing the occurrence of errors and unevenness during lamination is shown. It is more preferably in the range of 3 to 20 ppm / %RH, and even more preferably in the range of 5 to 15 ppm / %RH.

[0292] 〈Phase difference Ro and Rt〉

[0293] The functional layer of the present invention can function as an optical film such as a retardation film by being bonded to a polarizer after being peeled off from the base film.

[0294] For example, from the perspective of using as a phase difference film for IPS mode, the functional layer preferably has an in-plane phase difference Ro of 0 to 10 nm, more preferably 0 to 5 nm, measured at a wavelength of 590 nm and an environment of 23°C and 55% RH. The functional layer preferably has a thickness direction phase difference Rt of -40 to 40 nm, more preferably -25 to 25 nm.

[0295] Ro and Rt are respectively defined by the following formulae.

[0296] Formula (a): Ro=(n x -n y )×d

[0297] Formula (b): Rt=((n x +n y ) / 2-n z )×d

[0298] (Where,

[0299] n x represents the refractive index in the slow axis direction (the direction where the refractive index is maximum) of the functional layer in the plane,

[0300] n y represents the refractive index of the functional layer in a direction perpendicular to the in-plane slow axis,

[0301] n z represents the refractive index of the functional layer in the thickness direction,

[0302] d represents the thickness of the functional layer (nm)

[0303] The in-plane slow axis of the functional layer can be confirmed by an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRICS).

[0304] Ro and Rt can be measured by the following method.

[0305] 1) The functional layer was humidified for 24 hours in an environment of 23° C. and 55% RH. The average refractive index of the film was measured by Abbe's refractive index, and the thickness d was measured using a commercially available micrometer.

[0306] 2) The retardation Ro and Rt at a measurement wavelength of 590 nm of the humidity-controlled film were measured in an environment of 23° C. and 55% RH, respectively, using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRICS).

[0307] The phase differences Ro and Rt of the functional layer can be adjusted, for example, by the type of resin, stretching conditions, and drying conditions. For example, Rt can be reduced by increasing the drying temperature.

[0308] [3] Method for producing laminated film

[0309] The form of the laminated film of the present invention is not particularly limited, and may be, for example, in a tape shape. That is, the laminated film of the present invention is preferably wound in a roll in a direction perpendicular to its width direction to form a roll.

[0310] [3.1] Method for producing laminated film

[0311] [Manufacturing method]

[0312] The method for producing a laminated film of the present invention comprises: 1) obtaining a functional layer solution; 2) applying the obtained functional layer solution to the surface of a substrate film; and 3) removing the solvent from the applied functional layer solution to form a functional layer.

[0313] 1) Step of obtaining a functional layer solution

[0314] A functional layer solution containing the above-mentioned resin and a solvent is prepared.

[0315] The solvent used for the functional layer solution is not particularly limited as long as it can disperse or dissolve the resin well. For example, as the organic solvent used in the present invention, alcohols (methanol, ethanol, diol, triol, tetrafluoropropanol, etc.), glycols, cellosolves, ketones (acetone, methyl ethyl ketone, etc.), carboxylic acids (formic acid, acetic acid, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), esters (ethyl acetate, propyl acetate, etc.), ethers (isopropyl ether, THF, etc.), amides (dimethyl sulfoxide, etc.), hydrocarbons (heptane, etc.), nitriles (acetonitrile, etc.), aromatics (cyclohexylbenzene, toluene, xylene, chlorobenzene, etc.), halogenated alkanes (also called dichloromethane ("methylene chloride"), etc.), amines (1,4-diazabicyclo[2.2.2]octane, diazabicycloundecene, etc.), lactones, etc.

[0316] Among them, as the solvent of the functional layer, when preparing the slurry for the functional layer for film making, from the viewpoint of difficulty in handling and the viewpoint of controlling the coefficient of humidity expansion, it is preferred that the boiling point is below 100°C at atmospheric pressure, and the type is a chlorine-based solvent, more specifically methylene chloride (also known as "methylene dichloride"). When preparing the slurry for the functional layer for film making, it has high solubility and fast drying speed, thereby adjusting the film quality of the coating film, and then controlling the coefficient of humidity expansion, which is also preferred from such a viewpoint. In addition, adding a hydrophilic solvent can also control the coefficient of humidity expansion. As a hydrophilic solvent, ketones and alcohols can be cited, preferably alcohols. More preferably isopropanol, ethanol, methanol, etc., and most preferably methanol.

[0317] The amount added is preferably in the range of 1 to 20% by mass, more preferably in the range of 3 to 10% by mass.

[0318] From the viewpoint of easily adjusting the viscosity to the range described later, the resin concentration of the functional layer solution is preferably, for example, 1.0 to 20% by mass. Furthermore, from the viewpoint of reducing the shrinkage amount during drying of the coating film, the resin concentration of the functional layer solution is preferably moderately high, more preferably exceeding 5% by mass and being 20% ​​by mass or less, and further preferably exceeding 5% by mass and being 15% by mass or less. In addition, by adjusting the solution concentration, the time until the film is formed becomes shorter, and these drying times can also serve as a means of controlling the CHE of the functional layer. For high concentration, a mixed solvent can be appropriately used.

[0319] The viscosity of the solution for the functional layer is not particularly limited as long as it is a degree that can form a functional layer of the desired thickness, and is preferably 5 to 5000 mPa·s. If the viscosity of the solution for the functional layer is 5 cP or more, it is easy to form a functional layer of moderate thickness. If it is 5000 mPa·s or less, the viscosity of the solution increases, and the uneven thickness can be suppressed. From the same point of view, the viscosity of the solution for the functional layer is more preferably 100 to 1000 mPa·s. The viscosity of the solution for the functional layer can be measured at 25°C using an E-type viscometer.

[0320] 2) Step of providing a functional layer solution

[0321] Next, the obtained functional layer solution is applied to the surface of the base film. Specifically, the obtained functional layer solution is applied to the surface of the base film.

[0322] The coating method of the functional layer solution is not particularly limited, and may be a known method such as backroll coating, gravure coating, spin coating, wire bar coating, roll coating, etc. Among them, backroll coating is preferred from the viewpoint of being able to form a thin and uniform coating film.

[0323] 3) Process of forming a functional layer

[0324] Next, the solvent is removed from the functional layer solution applied to the base film to form a functional layer.

[0325] Specifically, the functional layer solution applied to the substrate film is dried. Drying can be performed, for example, by blowing air or heating. In particular, from the viewpoint of easily suppressing curling of the laminated film, drying can also be performed by blowing air.

[0326] The density of the functional layer can be controlled by adjusting the drying conditions (e.g., drying temperature, drying air volume, drying time, etc.), thereby adjusting CHE. In order to adjust the direction of increasing CHE, it is preferred to adjust the direction in which the film becomes sparse. Specifically, it is preferred to increase the drying speed, preferably 0.001 to 0.05 kg / hr·m 2, more preferably 0.002 to 0.01 kg / hr·m 2 .

[0327] The drying rate is expressed as the mass of the solvent evaporated per unit time and per unit area. The drying rate can usually be adjusted by the drying temperature. The drying temperature also depends on the type of solvent used, for example, it can be 50 to 200°C ((Tb-50) to (Tb+50)°C relative to the boiling point Tb of the solvent used). Temperature control can be performed in multiple stages. After a certain degree of drying, the drying rate and film quality can be controlled by drying at a higher temperature.

[0328] The laminated film of the present embodiment may be in a strip shape as described above. Therefore, the method for producing a laminated film of the present embodiment preferably further includes 4) the step of winding the strip-shaped laminated film into a roll shape to form a roll.

[0329] 4) Step of winding the laminated film to obtain a roll

[0330] The obtained strip-shaped laminated film is wound into a roll in a direction perpendicular to its width direction to obtain a roll.

[0331] The length of the strip-shaped laminated film is not particularly limited, and may be, for example, about 100 to 10,000 m. The width of the strip-shaped laminated film is preferably 1 m or more, more preferably 1.3 to 4 m. From the viewpoint of improving the uniformity of the film, it is more preferably 1.6 to 2.5 m.

[0332] [Manufacturing equipment]

[0333] The method for producing the laminated film of the present invention can be, for example, Figure 3 The manufacturing apparatus shown is carried out.

[0334] Figure 3 Schematic diagram of a manufacturing apparatus B200 for carrying out the manufacturing method of the laminated film of the present embodiment. The manufacturing apparatus B200 includes a supply unit B210, a coating unit B220, a drying unit B230, a cooling unit B240, and a winding unit B250. Ba to Bd represent conveying rollers for conveying the base film B110.

[0335] The supply unit B210 includes a take-out device (not shown) for taking out the roll body B201 of the strip-shaped base film B110 wound around the core.

[0336] The coating section B220 is a coating device having a support roller B221 for holding the base film B110 , a coating head B222 for coating the functional layer solution onto the base film B110 held by the support roller B221 , and a decompression chamber B223 provided on the upstream side of the coating head B222 .

[0337] The flow rate of the functional layer solution discharged from the coating head B222 can be adjusted by a pump (not shown). The flow rate of the functional layer solution discharged from the coating head B222 is set to an amount that can stably form a coating layer of a predetermined thickness when continuous coating is performed under the pre-adjusted conditions of the coating head B222.

[0338] The decompression chamber B223 is a mechanism for stabilizing the liquid beads (accumulation of coating liquid) formed between the functional layer solution from the coating head B222 and the substrate film B110 during coating, and the degree of decompression can be adjusted. The decompression chamber B223 is connected to a decompression blower (not shown) and the interior is decompressed. The decompression chamber B223 is in a state without air leakage, and the gap with the support roller is also adjusted to be narrow, so that stable liquid beads of the coating liquid can be formed.

[0339] The drying section B230 is a drying device for drying the coating film applied on the surface of the substrate film B110, and has a drying chamber B231, an inlet B232 for drying gas, and an outlet B233. The temperature and air volume of the drying air can be appropriately determined according to the type of the coating film and the type of the substrate film B110. By setting the temperature and air volume of the drying air, the drying time and other conditions in the drying section B230, the residual solvent amount of the dried coating film can be adjusted. The residual solvent amount of the dried coating film can be measured by comparing the unit mass of the dried coating film with the mass of the coating film after it is fully dried.

[0340] (Residual solvent amount)

[0341] Since the functional layer is obtained by coating the functional layer solution, the solvent from the solution may remain. The amount of residual solvent also becomes a means of controlling the moisture expansion coefficient, and can be controlled by the solvent and coating solution concentration, the wind speed blown for drying the functional layer, the drying temperature and time, the conditions of the drying room (external air or internal air circulation), the heating temperature of the support roll coating method during coating, etc.

[0342] As described above, when high-speed drying is performed, the film becomes loose and water permeation becomes faster, so the humidity expansion coefficient CHE2 becomes larger.

[0343] When the residual solvent content of the substrate film is S1 and the residual solvent content of the functional layer is S2, the residual solvent content of the functional layer preferably satisfies the following formula (2) from the viewpoint of curling balance of the laminated film.

[0344] Formula (2) 10<S1<S2<1000(ppm)

[0345] Specifically, the residual solvent content of the functional layer is preferably less than 1000 ppm, more preferably less than 800 ppm, and more preferably 500 to less than 700 ppm if the curling balance of the laminated film is considered. In addition, by selecting a solvent coating process in which the substrate film also has residual solvent, the adhesion between the laminates is improved. The residual solvent content of the substrate film is preferably in the range of 10 to 100 ppm.

[0346] The amount of residual solvent in the functional layer and the substrate film can be measured by headspace gas chromatography. In headspace gas chromatography, the sample is sealed in a container, heated, and the gas in the container is quickly injected into the gas chromatograph in a state where the container is full of volatile components, and mass analysis is performed. While identifying the compounds, the volatile components must be quantified. In the headspace method, all peaks of volatile components can be observed using a gas chromatograph, and by using an analysis method that uses electromagnetic interaction, volatile substances, monomers, etc. can also be quantified with high precision.

[0347] The cooling unit B240 cools the temperature of the base film B110 having the coating film (functional layer B120) obtained by drying in the drying unit B230, and adjusts it to an appropriate temperature. The cooling unit B240 has a cooling chamber B241, a cooling air inlet B242, and a cooling air outlet B243. The temperature and air volume of the cooling air can be appropriately determined according to the type of the coating film and the type of the base film B110. In addition, even if the cooling unit B240 is not provided, the cooling unit B240 may not be provided when the appropriate cooling temperature is reached.

[0348] The winding section B250 is a winding device (not shown) for winding up the base film B110 on which the functional layer B120 is formed to obtain a roll B251.

[0349] (thickness)

[0350] The thickness d2 of the functional layer is usually thinner than the thickness d1 of the base film. Specifically, from the viewpoint of reducing the thickness of the polarizer, the thickness d2 of the functional layer is preferably in the range of 1 to 19 μm, and more preferably in the range of 2 to 10 μm.

[0351] 〔4〕Polarizing film

[0352] The polarizing plate includes a polarizer and a laminated film or a functional layer disposed on at least one surface of the polarizer. The polarizer and the laminated film or the functional layer are preferably bonded to each other via an adhesive layer.

[0353] Figure 4A and Figure 4B Although an example of the layer structure of the polarizing plate of the present invention is shown, the present invention is not limited to this.

[0354] Figure 4AIt is a cross-sectional view of a polarizing plate with a substrate film.

[0355] The functional layer 3 side of the laminated film 1 (substrate film 2 and functional layer 3) of the present invention is bonded to the polarizer 5 via the adhesive layer 4 to form a polarizing plate 10a. The opposite surface of the polarizer 5 to the surface bonded with the laminated film 1 of the present invention may be bonded with an opposing film 6 via the adhesive layer 4 as needed.

[0356] For example, when a display device (not shown) has a polarizing plate 10a, the laminated film 1 of the present invention may be bonded to the display element side via an adhesive layer (not shown), and the counter film 6 may be bonded to the display element side via an adhesive layer (not shown). When the laminated film 1 of the present invention is bonded, the embodiment shown in FIG. 4(b) below in which the base film 2 is peeled off from the laminated film 1 is preferred.

[0357] Figure 4B It is a cross-sectional view of a polarizing plate from which the base film has been peeled off.

[0358] The functional layer 3 side of the laminated film 1 (base film 2 and functional layer 3) of the present invention is bonded to the polarizer 5 via the adhesive layer 4 to process the polarizer 10b. During or after the polarizer processing, the base film 2 is peeled off from the functional layer 3 to process the thin film polarizer 10b. On the surface of the polarizer 5 opposite to the surface bonded with the functional layer 3 of the present invention, an opposing film 6 can be bonded via the adhesive layer 4 as needed.

[0359] For example, when a display device (not shown) includes a polarizing plate 10b, the functional layer 3 of the present invention may be bonded to the display element side via an adhesive layer (not shown), and the opposing film 6 may be bonded to the display element side via an adhesive layer (not shown).

[0360] 〔4.1〕Polarizer

[0361] The polarizer is an element that transmits only light with a polarization plane in a certain direction. The polarizer may generally be a polyvinyl alcohol-based polarizing film. Examples of the polyvinyl alcohol-based polarizing film include a film obtained by dyeing a polyvinyl alcohol-based film with iodine and a film obtained by dyeing a dichroic dye.

[0362] The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching the polyvinyl alcohol-based film and then dyeing it with iodine or a dichroic dye (preferably a film further treated for durability with a boron compound); or a film obtained by dyeing the polyvinyl alcohol-based film with iodine or a dichroic dye and then uniaxially stretching it (preferably a film further treated for durability with a boron compound). The absorption axis of the polarizer is usually parallel to the maximum stretching direction.

[0363] The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 5 to 20 μm from the viewpoint of reducing the thickness of the polarizing plate.

[0364] [4.2] Laminated film or functional layer, and counter film

[0365] At least one surface of the polarizer is provided with a substrate film or a functional layer constituting the laminated film of the present invention. The substrate film or the functional layer constituting the laminated film can function as a polarizer protective film. In this embodiment, it is preferred to configure the functional layer on one surface of the polarizer and configure other protective films on the other surface.

[0366] Examples of the opposing film include cycloolefin resins, polypropylene resins, acrylic resins, polyester resins, polyarylate resins, cellulose ester resins, styrene resins, or composite resins thereof, etc. Among them, a resin film containing cycloolefin resins, acrylic resins, and polyester resins is preferred.

[0367] 〔4.3〕Adhesive layer

[0368] The adhesive layer is disposed between the functional layer and the polarizer and between the opposing film and the polarizer. The adhesive layer disposed between the functional layer and the polarizer and the adhesive layer disposed between the opposing film and the polarizer may be the same as or different from each other.

[0369] The adhesive layer may be a cured product layer of an active energy ray-curable adhesive, or may be a layer obtained from a water-soluble polymer.

[0370] The active energy ray-curable adhesive may be a photo-radical polymerizable composition or a photo-cationic polymerizable composition. Among them, a photo-cationic polymerizable composition is preferred.

[0371] The photocationically polymerizable composition contains an epoxy compound and a photocationic polymerization initiator.

[0372] In the case of water-soluble polymers, it is possible to carry out via the adhesive made of, for example, vinyl alcohol polymers or the adhesive made of water-soluble crosslinking agents of vinyl alcohol polymers such as boric acid or borax, glutaraldehyde or melamine, oxalic acid, etc. This adhesive layer can be formed as a coating dry layer of an aqueous solution, and when preparing its aqueous solution, it is also possible to coordinate catalysts such as other additives, acids as required. When using the process of water-soluble polymers, sometimes the curling of laminate is produced by the penetration of the included water, so that the yield of polaroid is reduced. It is also one of purposes of the present invention to prevent the error of such a process.

[0373] The thickness of the adhesive layer is not particularly limited, but is preferably 0.01 to 10 μm, and more preferably 0.01 to 5 μm.

[0374] 〔4.4〕Adhesive layer

[0375] The pressure-sensitive adhesive layer is a layer for bonding the polarizing plate to a display element such as a liquid crystal cell, and may be formed on either side of the polarizing plate, but may also be disposed on the side of the functional layer opposite to the polarizer.

[0376] The adhesive layer is preferably a layer formed by drying and partially crosslinking an adhesive composition containing a matrix polymer, a prepolymer and / or a crosslinkable monomer, a crosslinking agent, and a solvent. That is, the adhesive layer may be a layer formed by crosslinking at least a portion of the adhesive composition.

[0377] Examples of adhesive compositions include acrylic adhesive compositions using (meth)acrylic polymers as base polymers, silicone adhesive compositions using silicone polymers as base polymers, and rubber adhesive compositions using rubber as base polymers. Among them, acrylic adhesive compositions are preferred from the viewpoints of transparency, durability, heat resistance, and processability.

[0378] The adhesive composition may further contain various additives such as a thickener, a plasticizer, glass fibers, glass beads, metal powder, other fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and silane coupling agents as needed.

[0379] The thickness of the adhesive layer is usually about 3 to 100 μm, preferably 5 to 50 μm.

[0380] The surface of the adhesive layer is protected by a release film subjected to a release treatment. Examples of the release film include plastic films such as acrylic films, polycarbonate films, polyester films, and fluororesin films.

[0381] 〔4.4〕Method for manufacturing polarizing plate

[0382] The polarizer of the present embodiment can be manufactured by laminating the above-mentioned laminated film on at least one surface of the polarizer and peeling off the substrate film. The lamination of the laminated film can be performed on only one surface of the polarizer or on both surfaces. From the perspective of transmittance, it is preferred to laminate the laminated film on one surface of the polarizer and laminate the opposing film as other protective films on the other surface.

[0383] The polarizer may be laminated to the substrate film side or the functional layer side of the laminated film of the present invention. It is preferred to laminate to the functional layer side and use the substrate film as a protective film or to peel off and use only the functional layer as a thin film.

[0384] Therefore, when a polarizing plate roll is manufactured by laminating a laminated film to at least one surface of a polarizer and winding it, a preferred method for manufacturing a polarizing plate roll is to laminarize the laminated film to the polarizer and wind it in the order of the layers of the polarizer, the functional layer and the base film from the inner side of the roll. In addition, a method in which the laminated film is laminated to the polarizer and dried, and before winding it, the base film in the laminated film is peeled off and rolled up is also a preferred method.

[0385] Basically, the polarizing plate of the present invention can be produced through the following steps: 1) a step of bonding the functional layer of the above-mentioned laminated film to one surface of a polarizer (the substrate film arranged on the surface of the functional layer on the opposite side of the polarizer can be in an attached state or can be peeled off as needed); 2) bonding an opposing film serving as other protective films to the other surface of the polarizer.

[0386] 1) Functional layer bonding process

[0387] The functional layer of the laminated film is bonded to one surface of the polarizer via an adhesive. The surface of the bonded functional layer or one surface of the polarizer may be subjected to a pre-treatment such as a corona treatment as necessary.

[0388] For example, when a water-soluble polymer adhesive is used as an adhesive, 1) a surface treatment such as a corona treatment is applied to the surface of the functional layer of the laminated film as needed. Next, the functional layer of the laminated film is laminated on one side of the polarizer via the adhesive of the water-soluble polymer. 2) Next, an opposing film as another protective film is bonded to the other side of the polarizer. Specifically, a surface treatment such as a corona treatment is applied to the surface of the opposing film as needed. Next, after the opposing film is laminated on the other side of the polarizer via the adhesive of the water-soluble polymer, a drying treatment is performed in stages, for example, at a temperature range of 50 to 80°C.

[0389] The steps 1) and 2) may be performed simultaneously or sequentially. From the viewpoint of improving production efficiency, the steps 1) and 2) are preferably performed simultaneously.

[0390] Therefore, in the steps 1) and 2), it is preferred that the functional layer of the laminated film in strip form, the polarizer in strip form, and the other protective film in strip form (counter film) are unwound from a roll and laminated roll to roll to perform polarizing plate processing.

[0391] In addition, it is preferred to further carry out a step of winding the strip-shaped polarizer into a roll to form a roll. In this step, the length and width of the strip-shaped polarizer may be the same as the length and width of the strip-shaped laminated film in step 4) of the method for producing the laminated film.

[0392] In addition, in the manufacturing method of the polarizing plate roll of the present invention, in the process of winding the laminated film while laminating it to at least one surface of the polarizer 5, it is also preferred to form the polarizing plate roll by laminating the laminated film 1 to the polarizer 5 while winding it in the order of the layers from the inside of the roll, namely, the polarizer 5, the adhesive layer 4, the functional layer 3 and the base film 2. In this case, since the base film 2 of the present invention is arranged on the outside of the polarizing plate roll, it can function as a protective film, prevent damage to the functional layer 2 during the processing of the polarizing plate, or suppress curling for easy handling.

[0393] In this case, the opposing film 6 may be bonded to the polarizer 5 via the adhesive layer 4 on the surface opposite to the surface bonded with the laminated film 1 as required, and then wound to form a polarizing plate roll.

[0394] [5] Display device

[0395] The display device of this embodiment has a display element such as a liquid crystal unit, an organic electroluminescent element (also referred to as "EL") element, and a polarizer manufactured by the above manufacturing method. Among them, the display device of this embodiment is preferably a liquid crystal display device having a liquid crystal unit and a polarizer manufactured by the above manufacturing method.

[0396] That is, the liquid crystal display device includes a liquid crystal cell, a first polarizer disposed on one surface of the liquid crystal cell, and a second polarizer disposed on the other surface of the liquid crystal cell. Moreover, at least one of the first polarizer and the second polarizer is the polarizer of this embodiment. The absorption axis of the first polarizer in the first polarizer and the absorption axis of the second polarizer in the second polarizer are preferably orthogonal (to form orthogonal Nicols).

[0397] The display mode of the liquid crystal unit may be, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybrid aligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment), PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), etc. For example, in a liquid crystal display device for portable settings, the IPS mode is preferred.

[0398] Example

[0399] The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereto. It should be noted that "parts" or "%" are used in the Examples, but unless otherwise specified, they represent "parts by mass" or "mass %".

[0400] Example 1

[0401] [1] Laminated film materials

[0402] [1-1] Base film

[0403] <Base film A>

[0404] Polyethylene terephthalate film (PET film): (TN100 manufactured by Toyobo Co., Ltd., having a release layer containing a non-silicone release agent, thickness 38 μm)

[0405] <Base film B>

[0406] A polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) stretched 13% in the TD direction (thickness 30 μm)

[0407] <Base film C>

[0408] A film (thickness 25 μm) obtained by stretching a polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) by 30% in the TD direction

[0409] <Base film D>

[0410] A film (thickness 38 μm) prepared by thermally holding a polyethylene terephthalate film (PET film) (TN100 manufactured by Toyobo Co., Ltd.) at 150° C. for 30 seconds.

[0411] <Base film E>

[0412] Triacetyl cellulose film (TAC) (KC4UA manufactured by Konica Minolta, Inc., without release layer, thickness 38 μm)

[0413] <Base film F>

[0414] Cyclic olefin film (COP) (ARTON G7810 manufactured by JSR Corporation, without release layer, thickness 38 μm)

[0415] <Base film G>

[0416] High-density polyethylene (HDPE) (HI-ZEX 2200J (manufactured by Prime Polymer Co., Ltd.), thickness 38 μm)

[0417] The humidity expansion coefficient CHE1 of the base films A to G at 23° C. was measured by the following method.

[0418] (Humidity expansion coefficient at 23°C CHE1)

[0419] The humidity expansion coefficient CHE1 of the base film at 23° C. is measured in accordance with JIS K7197.

[0420] The film sample is fixed in a constant temperature and humidity chamber with a width of 1 cm and a sample length of 15 cm. It is dehumidified to a certain humidity (about 30% RH). After the film length becomes constant, if it is humidified (about 80% RH), it will begin to elongate by absorbing moisture. After about 24 hours, the moisture absorption reaches equilibrium, and the elongation of the film also reaches equilibrium. According to the elongation at this time, the following formula is used for calculation. At this time, the atmospheric temperature is kept constant at 23°C.

[0421] Humidity expansion coefficient at 23°C (ppm / %RH) = elongation (cm) / (specimen length (cm) × humidity difference) × 10 6

[0422] [1-2] Solution for functional layer

[0423] (1) Material preparation

[0424] <Resin>

[0425] 1. COP (G7810): ARTON G7810 manufactured by JSR Corporation, Mw: 140,000, a cycloolefin resin having a carboxylic acid group

[0426] 2. Fumaric acid resin: Fumaric acid diester resin made by Tosoh Corporation, number average molecular weight 120,000

[0427] 3. Acrylic acid: MMA / PMI / MADA copolymer (60 / 20 / 20 mass ratio), Mw: 1.5 million, Tg: 137°C (It should be noted that the abbreviations are shown below. MMA: methyl methacrylate, PMI: phenylmaleimide and MADA: adamantyl acrylate)

[0428] 4. Polyarylate: U-100 manufactured by Unitika

[0429] 5.COP (ZNX330R): ZNX330R made by Zeon Corporation of Japan

[0430] 6. A-DCP: tricyclodecane dimethanol diacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.)

[0431] 7. PSt / polyarylate (mass ratio 5:5) mixture: Pst (polystyrene: manufactured by PS JAPAN, Mw: 500,000: manufactured by PS JAPAN), polyarylate (the following compound P)

[0432] 8.PSt: Polystyrene (Mw: 500,000: manufactured by PS JAPAN)

[0433] 9.TAC: acetyl cellulose with acetyl substitution degree 2.9

[0434]

[0435] The glass transition temperature (Tg) and weight average molecular weight (Mw) of resins 1 to 9 were measured by the following method.

[0436] (Glass transition temperature)

[0437] The glass transition temperature (Tg) of the resin is measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0438] (Weight average molecular weight)

[0439] The weight average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation in series). 20 mg ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered using a 0.45 mm filter. 100 ml of the solution was injected into the column (temperature 40° C.), and the detector RI temperature was 40° C. for measurement, using the value converted to styrene.

[0440] <Rubber particles R1>

[0441] Rubber particles R1 prepared by the following method were used.

[0442] The following materials were placed in an 8 L polymerization apparatus equipped with a stirrer.

[0443]

[0444] After the inside of the polymerization machine was fully purged with nitrogen, the internal temperature was set to 80°C, and 0.021 parts by mass of potassium persulfate was added in the form of a 2% aqueous solution. Next, a mixed solution obtained by adding 0.07 parts by mass of polyoxyethylene lauryl ether phosphoric acid to 21 parts by mass of a monomer mixture (c') consisting of 84.6% by mass of methyl methacrylate, 5.9% by mass of butyl acrylate, 7.9% by mass of styrene, 0.5% by mass of allyl methacrylate, and 1.1% by mass of n-octyl ester mercaptan was continuously added to the above solution over 63 minutes. Furthermore, the polymerization reaction was continued for 60 minutes to obtain the innermost hard polymer (c).

[0445] Thereafter, 0.021 parts by mass of sodium hydroxide in the form of a 2% aqueous solution and 0.062 parts by mass of potassium persulfate in the form of a 2% aqueous solution were added. Next, a mixed solution obtained by adding 0.25 parts by mass of polyoxyethylene lauryl ether phosphoric acid to 39 parts by mass of a monomer mixture (a') consisting of 80.0% by mass of butyl acrylate, 18.5% by mass of styrene, and 1.5% by mass of allyl methacrylate was continuously added for 117 minutes. After the addition was completed, 0.012 parts by mass of potassium persulfate in the form of a 2% aqueous solution was added, and the polymerization reaction was continued for 120 minutes to obtain a soft layer (a layer consisting of an acrylic rubber-like polymer (a)). The glass transition temperature (Tg) of the soft layer is -30°C. The glass transition temperature of the soft layer is calculated by averaging the glass transition temperatures of the homopolymers of each monomer constituting the acrylic rubber-like polymer (a) according to the composition ratio.

[0446] Thereafter, 0.04 parts by mass of potassium persulfate was added as a 2% by mass aqueous solution, and 26.1 parts by mass of a monomer mixture (b') consisting of 97.5% by mass of methyl methacrylate and 2.5% by mass of butyl acrylate was continuously added over 78 minutes. The polymerization reaction was further continued for 30 minutes to obtain a polymer (b).

[0447] The obtained polymer was put into a 3 mass % sodium sulfate warm water solution to cause salting out and coagulation. Then, dehydration and washing were repeated, and then drying was performed to obtain acrylic acid graft copolymer particles (rubber particles R1) having a three-layer structure. The average particle size of the obtained rubber particles R1 was 200 nm.

[0448] The average particle size of the rubber particles is measured by the following method.

[0449] (Average particle size)

[0450] The dispersed particle size of the rubber particles in the obtained dispersion was measured using a zeta potential particle size measuring system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0451] (2) Preparation of solution for functional layer

[0452] <Preparation of functional layer solution for laminated film 201>

[0453] The following components are mixed to obtain a functional layer solution 201 .

[0454] Toluene (boiling point 110°C): 900 parts by mass

[0455] COP(G7810): 100 parts by mass

[0456] <Preparation of functional layer solution for laminated films 202 to 205>

[0457] Functional layer solutions for laminated films 202 to 205 were obtained in the same manner as the functional layer solution for laminated film 201 except that the solvent was changed to cyclopentanone (boiling point 131° C.) and dichloromethane (methylene chloride, boiling point 41° C.) shown in Table I.

[0458] <Preparation of Functional Layer Solution for Laminated Films 206 to 215>

[0459] The following components were mixed to obtain functional layer solutions 206 to 215.

[0460] Dichloromethane (boiling point 41°C): 760 parts by mass

[0461] Methanol (boiling point 65°C): 40 parts by mass

[0462] COP(G7810): 200 parts by mass

[0463] <Preparation of Functional Layer Solution for Laminated Films 216 to 222>

[0464] The following components are mixed to obtain a functional layer solution 216 .

[0465] Methyl ethyl ketone (MEK: boiling point 80°C) 900 parts by mass

[0466] Fumaric acid diester resin (expressed as fumaric acid resin): 100 parts by mass

[0467] In the functional layer solution for laminated films 217 to 222, as shown in Table II, the solvent is appropriately changed to a mixed solution of MEK (boiling point 80°C): toluene (boiling point 110°C) = 7:3 (mass ratio), dichloromethane (boiling point 41°C) and a resin concentration (10 mass % or 20 mass %). Otherwise, the functional layer solution for laminated films 217 to 222 is prepared in the same manner as the functional layer solution for laminated film 216.

[0468] <Preparation of functional layer solution for laminated film 223>

[0469] The following components are mixed to obtain a functional layer solution 223 .

[0470] Methyl ethyl ketone (MEK: boiling point 80°C) 900 parts by mass

[0471] Acrylic acid: 100 parts by mass

[0472] <Preparation of functional layer solution for laminated film 224>

[0473] The following components are mixed to obtain a functional layer solution 224 .

[0474] Methyl ethyl ketone (MEK: boiling point 80°C) 900 parts by mass

[0475] Acrylic acid: 80 parts by mass

[0476] Rubber particles R1: 20 parts by mass

[0477] <Preparation of functional layer solution for laminated film 225>

[0478] The following components are mixed to obtain a functional layer solution 225 .

[0479] Dichloromethane (boiling point 41°C) 900 parts by mass

[0480] Acrylic acid: 100 parts by mass

[0481] <Preparation of functional layer solution for laminated films 226 and 227>

[0482] The following components are mixed to obtain a functional layer solution 226 .

[0483] Dichloromethane (boiling point 41°C) 800 parts by mass

[0484] Acrylic acid: 80 parts by mass

[0485] Rubber particles R1: 20 parts by mass

[0486] The following components are mixed to obtain a functional layer solution 227 .

[0487] Dichloromethane (boiling point 41°C) 800 parts by mass

[0488] Acrylic acid: 160 parts by mass

[0489] Rubber particles R1: 20 parts by mass

[0490] <Preparation of functional layer solution for laminated films 228 and 229>

[0491] The following components are mixed to obtain a functional layer solution 228 .

[0492] Toluene (boiling point 110°C): 900 parts by mass

[0493] Polyarylate (U-100 manufactured by Unitika Co., Ltd.): 100 parts by mass

[0494] The functional layer solution for the laminated film 229 was prepared in the same manner as the functional layer solution for the laminated film 228 except that dichloromethane (boiling point 41° C.) was used as a solvent as shown in Table III.

[0495] <Preparation of functional layer solution for laminated film 230>

[0496] With reference to Example 1 of Japanese Patent Application Laid-Open No. 2020-3823, the following components were mixed to obtain a functional layer solution 230.

[0497] Cyclohexane (boiling point 81°C): 900 parts by mass

[0498] COP(ZNX330R) 100 parts by mass

[0499] <Preparation of functional layer solution for laminated film 231>

[0500] Using Example 3 of Japanese Patent Publication No. 2018-45220 as a reference, the following components were mixed to obtain a functional layer solution for the laminated film 231.

[0501]

[0502] <Preparation of functional layer solution for laminated film 232>

[0503] Using Example 3 of Japanese Patent Publication No. 2018-45220 as a reference, the following components were mixed to obtain a functional layer solution for the laminated film 232.

[0504]

[0505] <Preparation of functional layer solution for laminated film 233>

[0506] Using Example 3 of Japanese Patent Publication No. 2018-41028 as a reference, the following components were mixed to obtain a functional layer solution for the laminated film 233.

[0507]

[0508] <Preparation of functional layer solution for laminated film 234>

[0509] The following components are mixed to obtain a functional layer solution 234 .

[0510]

[0511] [2] Fabrication of laminated films

[0512] <Production of Laminated Film 201>

[0513] As a substrate film, a PET film (TN100 manufactured by Toyobo Co., Ltd., substrate film A) was prepared. On the release layer of the PET film, a functional layer solution for the laminated film 201 was applied using a die head by a support roll coating method, and then the laminated film was dried in the following drying step to form a functional layer with a thickness of 5 μm, thereby obtaining a laminated film 201.

[0514] Step 1: 1 minute at 40°C

[0515] Step 2: 1 minute at 70°C

[0516] Step 3: 1 minute at 100°C

[0517] Step 4: 2 minutes at 130°C

[0518] <Production of laminated films 202 to 234>

[0519] In the preparation of the laminated film 201, the type and thickness of the base film and the type and thickness of the functional layer solution were changed as shown in Tables I to III, and the laminated films 202 to 234 were obtained in the same manner. It should be noted that the drying temperature was changed only in the dryer temperature of the fourth step, and the temperatures of the first, second, and third steps were fixed.

[0520] "evaluate"

[0521] (1) Qualitative and quantitative determination of residual solvents

[0522] The qualitative and quantitative determination of the residual solvent in the obtained laminated film is performed by peeling the laminated film into the base film and the functional layer, respectively, and performing headspace gas chromatography. In headspace gas chromatography, the sample is sealed in a container and heated, and the gas in the container is quickly injected into the gas chromatograph in a state where the container is full of volatile components, and mass analysis is performed to identify the compounds while quantifying the volatile components. The quantification of the volatile components is performed by pre-preparing a standard curve using a sample with a known concentration, and comparing the peak area of ​​the volatile components obtained by measurement with the standard curve.

[0523] (Measurement conditions)

[0524] Head space device: HP7694 Head Space Sampler (manufactured by Hewlett-Packard Company)

[0525] Temperature conditions: transmission line 200℃, loop temperature 200℃

[0526] Sample volume: 0.8g / 20ml vial

[0527] GC: HP5890 (manufactured by Hewlett-Packard Company)

[0528] MS: HP5971 (manufactured by Hewlett-Packard Company)

[0529] Column: HP-624 (30m×inner diameter 0.25mm)

[0530] Oven temperature: initial temperature 40°C (holding time 3 minutes), heating rate 10°C / min, reaching temperature 200°C (holding time 5 minutes)

[0531] Measurement mode: SIM (selected ion monitoring) mode

[0532] (2) Determination of the humidity expansion coefficient (CHE2) of the functional layer at 23°C

[0533] In the obtained laminated film, in a sample in which the base film was peeled off, the humidity expansion coefficient (CHE2) of the functional layer at 23° C. was measured by the same method as the humidity expansion coefficient (CHE1) of the above-mentioned base film.

[0534] (3) Transportability (transport stability)

[0535] The transport stability of the laminated film was evaluated by checking whether or not breakage or cracking occurred during roll transport on a production line while applying a transport tension of 350 N / m. The transport stability was evaluated based on the following criteria.

[0536] 0: The functional layer is not broken and can be transported

[0537] △: The functional layer has slight scratches and cracks, but the material can be transported.

[0538] ×: Functional layer cracked or broken

[0539] If it is △ or more, it is judged to be good.

[0540] (4) Curling in water

[0541] The laminated film was cut into a strip of 35 mm (lateral direction during production) x 2 mm (longitudinal direction during production), and the curl in the width direction of the film was measured when the film was immersed in warm water at 38°C for 30 minutes.

[0542] When the side coated with the functional layer was concave, the measurement was positive (plus).

[0543] [Curl]

[0544] The obtained laminated film was cut into a circle with a diameter of 5 cm to prepare a sample. The obtained sample was placed in a constant temperature and humidity chamber at 23°C and 55% RH for 24 hours. Thereafter, the sample was taken out of the constant temperature and humidity chamber, placed on a flat plate, and 1 / r was calculated from the radius of curvature r (m) of a curve consistent with the sample using a curvature scale. Then, the curling amount was evaluated based on the following criteria.

[0545] ◎: 1 / r is less than 4

[0546] ○: 1 / r is 4 or more and less than 8

[0547] △: 1 / r is greater than 8 and less than 12

[0548] ×: 1 / r is 12 or more

[0549] If it is △ or more, it is judged to be good.

[0550] (5) Compatibility with polarizer

[0551] (Evaluation of fit)

[0552] A 60 μm thick long polyvinyl alcohol film containing polyvinyl alcohol (hereinafter referred to as "PVA") was continuously conveyed via a guide roller while being immersed in a dyeing bath (30°C) containing boric acid and potassium iodide, and subjected to dyeing treatment and 2.5 times stretching treatment. Then, a total of 5 times stretching treatment and crosslinking treatment were carried out in an acid bath (60°C) to which boric acid and potassium iodide were added, and the obtained iodine-PVA polarizer with a thickness of 12 μm was dried in a dryer at 50°C for 30 minutes to obtain a polarizer with a moisture content of 4.9%. The polarizer was cut into 10 cm×10 cm.

[0553] Next, the following components were mixed to prepare a water-based adhesive 1.

[0554] Pure water: 100 parts by mass

[0555] Polyvinyl alcohol-based resin (trade name "GOSEFIMER Z200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 3 parts by mass

[0556] A water-based adhesive 1 is applied to the PVA polarizer using a wire rod (#0), and the film of the present application processed into 10 cm×10 cm is bonded to the PVA surface in the form of a functional layer using a high-precision desktop laminating machine HAL-215 (manufactured by Sankyo Co., Ltd.) for single sheet lamination. The base film is then peeled off to produce a laminate of the PVA and functional layers.

[0557] The lamination process suitability of the laminate was evaluated as follows.

[0558] (Evaluation column)

[0559] ◎: Even after laminating 50 sheets, no bubbles were found, no breakage of the edges, no film displacement, etc.

[0560] ○: Even after laminating 20 sheets, no bubbles were found, no breakage of the end, no film displacement, etc.

[0561] △: Even after laminating 10 sheets, no bubbles were found, no breakage of the edges, no film displacement, etc.

[0562] ×: When 10 sheets were bonded, one or more sheets had bubbles mixed in, edge breakage, or film displacement.

[0563] (6) Interference fringes

[0564] 〈Production of Polarizing Film〉

[0565] Using the laminated films 201 to 234 produced as described above, a polarizing plate was produced by the following procedure.

[0566] (Production of Polarizer)

[0567] A long strip of polyvinyl alcohol film with a thickness of 60 μm is immersed in a dyeing bath (30°C) of iodine and potassium iodide while being continuously conveyed via a guide roller, and is subjected to dyeing treatment and 2.5-fold stretching treatment. It is then subjected to a total of 5-fold stretching treatment and cross-linking treatment in an acidic bath (60°C) to which boric acid and potassium iodide are added. The resulting iodine-PVA polarizer with a thickness of 12 μm is dried in a dryer at 50°C for 30 minutes to obtain a polarizer with a moisture content of 4.9%.

[0568] (Production of polarizing film)

[0569] The polarizer produced above was sandwiched from both sides by using the laminated films 201 to 234 and the optical films described below as opposing films, and bonded via the water-soluble adhesive liquid 1 described below, thereby producing polarizing plates 201 to 234 .

[0570] At this time, the longitudinal direction of the polarizer and the longitudinal direction of the laminated film were aligned with each other and bonded together.

[0571] 〈Opposing film〉

[0572] As the opposing film, a film containing the following resin was used.

[0573] COP (cycloolefin): ARTON G7810 manufactured by JSR Corporation

[0574] (Preparation of water-soluble adhesive solution 1)

[0575] The following components were mixed and then degassed to prepare a water-soluble adhesive solution 1.

[0576] 100 parts by mass of pure water

[0577] "Epocross WS-300" manufactured by Nippon Shokubai Co., Ltd. 7.5 parts by mass

[0578] "CROSSLINKER CL-427" manufactured by Menadiona 0.1 parts by mass

[0579] It should be noted that for the production of polarizers, the adhesive side surface of the laminated film was subjected to corona discharge treatment at a corona output intensity of 2.0 kW and a linear speed of 18 m / min, and the water-soluble adhesive liquid 1 prepared above was applied to the corona discharge treated surface by a rod coater in a manner such that the thickness after drying became about 3 μm, and then dried at 50° C., 60° C., and 70° C. for 60 seconds each, to obtain a polarizer.

[0580] The prepared polarizing plate was placed on a light-proof black cloth such as a blackout curtain with the surface having the functional layer facing upward, and irradiated with a three-wavelength fluorescent lamp (National Fluorescent Lamp: FL20SS·ENW / 18 manufactured by Panasonic Corporation). The surface of the polarizing plate was visually observed and evaluated according to the following criteria.

[0581] ◎: Ten samples were observed, but no interference unevenness was observed.

[0582] ○: No interference fringes are visible

[0583] △: Interference fringes can be vaguely seen

[0584] ×: Interference fringes are obvious

[0585] The production conditions of the obtained laminated films 201 to 234 are shown in Tables I, II and III, and the evaluation results are shown in Table IV. The content of the rubber particles indicates mass % in the coating film (functional layer) after drying.

[0586] [Table 1]

[0587]

[0588] [Table 2]

[0589]

[0590] [Table 3]

[0591]

[0592] [Table 4]

[0593]

[0594] As shown in Table IV, the transportability, underwater curling, adhesion and interference fringe evaluation of the laminated films 201 to 208, 211 to 213, 216 to 218, 222, 224 and 226 to 229 of the present invention are superior to those of the laminated films of the comparative examples. In particular, when the value represented by formula (1) is in the range of 0.30 to 1.00, the adhesion is good, and when it is in the range of 0.40 to 0.80, the interference fringe characteristics tend to become better.

[0595] Example 2

[0596] The retardation of the functional layers of the laminated films 204, 213, 214, 216, 218, 226 and 229 prepared in Example 1 was measured by the following method. The results are shown in Table V.

[0597] The retardation Ro and Rt are measured by the following method.

[0598] 1) The base film was peeled off from the laminated film, and the functional layer was humidified in an environment of 23° C. and 55% RH for 24 hours. The average refractive index of the layer was measured by Abbe's refractive index, and the thickness d was measured using a commercially available micrometer.

[0599] 2) The retardation Ro and Rt of the film after humidity control at a measurement wavelength of 590 nm were measured in an environment of 23° C. and 55% RH, respectively, using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRICS).

[0600] Ro and Rt are respectively defined by the following formulae.

[0601] Formula (a): Ro = (nx - ny) × d

[0602] Formula (b): Rt=((nx+ny) / 2-nz)×d

[0603] (where nx represents the refractive index of the functional layer in the direction of the in-plane slow axis, ny represents the refractive index of the functional layer in the direction orthogonal to the in-plane slow axis, nz represents the refractive index of the functional layer in the thickness direction, and d represents the thickness of the functional layer (nm))

[0604] [Table 5]

[0605]

[0606] According to the results in Table V, the retardation values ​​of the functional layer of the present invention are Ro in the range of 0 to 20 nm and Rt in the range of -25 to 25 nm, and are both suitable as a phase difference film for an IPS mode liquid crystal display device.

[0607] Industrial Applicability

[0608] According to the present invention, a laminated film can be obtained which, although being a thin film, has excellent transportability and can be handled in the same manner as conventional polarizer protective films. Furthermore, a laminated film has excellent curl controllability during polarizer processing. Therefore, it is possible to provide a high-quality polarizer and display device which has excellent productivity (adhesion to the polarizer) during polarizer processing and is free of optical unevenness.

[0609] 1 Laminated film

[0610] 2. Substrate film

[0611] 3 Functional layer

[0612] 4 Adhesive layer

[0613] 5 Polarizer

[0614] 6 Opposing film

[0615] 10,10' Polarizer

[0616] B110 Base Film

[0617] B120 functional layer

[0618] B200 Manufacturing Device

[0619] B210 Supply Department

[0620] B220 coating department

[0621] B230 Drying Section

[0622] B240 Cooling Unit

[0623] B250 Winding Unit

Claims

1. A laminated film, characterized in that: It is a laminated film in which a peelable functional layer is laminated on a base film. The substrate film contains polyethylene terephthalate, The functional layer contains a fumaric acid diester resin or a (meth)acrylic resin containing rubber particles. The thickness of the functional layer is in the range of 1 to 19 μm. The total thickness of the laminated film is 50 μm or less, When the humidity expansion coefficient of the substrate film at 23° C. is CHE1 and the thickness is d1, and when the humidity expansion coefficient of the functional layer at 23° C. is CHE2 and the thickness is d2, the following relationship is satisfied: Formula 1 0.20<|(CHE1-CHE2)|×(d2 / d1)<2.00 In Formula 1, the units of humidity expansion coefficients CHE1 and CHE2 are ppm / %RH, and the units of thicknesses d1 and d2 are μm.

2. The laminated film according to claim 1, characterized in that The thickness of the functional layer is in the range of 2 to 10 μm.

3. The laminated film according to claim 1 or 2, characterized in that: The total thickness of the laminated film is in the range of 30 to 45 μm.

4. The laminated film according to any one of claims 1 to 3, characterized in that The functional layer has a retardation value Ro defined by the following formula i in the range of 0 to 20 nm, and a retardation value Rt defined by the following formula ii in the range of -25 to 25 nm. Formula i Ro = (n x -n y )×d Formula Rt={(n x +n y ) / 2-n z }×d In the above formulas i and ii, Ro is the retardation value in the in-plane direction of the functional layer, Rt is the retardation value in the thickness direction of the functional layer, and n x is the refractive index of the functional layer in the direction of the slow axis in the plane, n y is the refractive index of the functional layer in the direction of the phase-advancing axis, n z represents the refractive index of the functional layer in the thickness direction, and d represents the thickness of the film. The refractive index is a value measured at a wavelength of 590 nm under an environment of 23° C. and 55% RH, and the unit of the thickness d is nm.

5. The laminated film according to any one of claims 1 to 4, characterized in that When the residual solvent content of the substrate film is set to S1 and the residual solvent content of the functional layer is set to S2, the following formula 2 is satisfied: Formula 2 10ppm<S1<S2<1000ppm, Wherein, in Formula 2, the unit of the residual solvent contents S1 and S2 is ppm.

6. The laminated film according to claim 5, characterized in that The boiling point of the main residual solvent among the residual solvents is 100° C. or lower under atmospheric pressure.

7. The laminated film according to claim 5 or 6, characterized in that: The residual solvent is a chlorine-based solvent.

8. The laminated film according to any one of claims 5 to 7, characterized in that The residual solvent is dichloromethane.

9. The laminated film according to any one of claims 5 to 8, characterized in that The residual solvent includes dichloromethane and alcohols.

10. The laminated film according to any one of claims 1 to 9, wherein The substrate film is a biaxially stretched polyester film, and the humidity expansion coefficient CHE1 of the polyester film at 23° C. is in the range of 10 to 20 ppm / %RH.

11. The laminated film according to any one of claims 1 to 10, characterized in that The functional layer contains a polymer material having a carbonyl group in a side chain.

12. The laminated film according to any one of claims 1 to 10, wherein The functional layer contains a polymer material having a ring structure in the main chain.

13. A polarizing plate, characterized in that: A laminated film according to any one of claims 1 to 12.

14. A display device, characterized in that: A laminated film according to any one of claims 1 to 12 or a polarizing plate according to claim 13 is provided.

15. A method for manufacturing a polarizing plate roll, characterized in that: A method for producing a polarizing plate roll comprising winding the laminated film according to any one of claims 1 to 12 while bonding it to at least one surface of a polarizer, comprising the following steps: The laminated film is wound up while being bonded to the polarizer so that the layers of the polarizer, the pressure-sensitive adhesive layer, the functional layer, and the base film are in this order from the inner side of the roll.

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