Polarizing plate and method for manufacturing the same, and method for manufacturing a display device

Abstract

A polarizing plate according to the present invention is formed by laminating a polarizer, a first protective film disposed on one surface of the polarizer, a second protective film disposed on the other surface of the polarizer, and a release film disposed on a surface of the first protective film on the opposite side to the polarizer. An extinction coefficient A2 of the second protective film for light with a wavelength of 9.4 μm is 1.0×102 to 4.5×102 / μm. In a cross-section of the polarizing plate conforming to the lamination direction, a straight line connecting an end point P1 of the release film at a cut end surface on the opposite side to the first protective film and an end point P2 of the polarizer at the cut end surface on the second protective film side has an angle φ of inclination 0.5-10° with respect to the lamination direction.

Description

[Technical Field]

[0001] This invention relates to polarizing plates, methods for manufacturing the same, and methods for manufacturing display devices. [Background technology]

[0002] Display panels such as liquid crystal displays (LCDs) and organic EL displays (OLEDs) typically include polarizers. A polarizer consists of a polarizer and two protective films (optical films) that sandwich it. Such polarizers are manufactured by laminating the polarizer and the two protective films using a roll-to-roll process, and then cutting the resulting laminate to a size suitable for a display panel.

[0003] Traditionally, laminates have been cut using cutting tools. However, this method often generates foreign matter such as film scraps during the cutting process. Protective films contaminated with such foreign matter can cause display defects on the display panel.

[0004] Therefore, in recent years, polarizing plates have been cut using laser light (see, for example, Patent Documents 1 and 2). For example, as a method for cutting a laminated film of multiple resin layers of different materials, a method is known in which laser light of different wavelengths is used depending on the type of resin layer (see, for example, Patent Document 1). In addition, a method is known in which the film is cut to an intermediate depth with laser light, and then physically torn apart to cut it (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-98400 [Patent Document 2] Japanese Patent Publication No. 2012-30243 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, there are various types and combinations of the two protective films used in polarizing plates, and their laser light absorption properties can vary greatly. For example, in Patent Documents 1 and 2, a laminate in which a cellulose triacetate film (TAC) is laminated on one side of a polarizer and a cycloolefin resin film is laminated on the other side is obtained by cutting it with laser light. However, display devices manufactured using such polarizing plates have the problem of easily producing display unevenness at the edges of the display screen.

[0007] Furthermore, the method described in Patent Document 1 requires the use of different types of laser light, and the method described in Patent Document 2 involves a combination of laser cutting and physical cutting, resulting in low productivity.

[0008] This invention has been made in view of the above circumstances, and aims to provide a polarizing plate and a method for manufacturing the same, which can be cut by laser light without reducing productivity and can suppress display unevenness at the edges of a display device, as well as a method for manufacturing a display device. [Means for solving the problem]

[0009] The present invention relates to the following polarizing plate, a method for manufacturing the same, and a method for manufacturing a display device.

[0010] The polarizing plate of the present invention is a polarizing plate comprising a polarizer, a first protective film disposed on one side of the polarizer, a second protective film disposed on the other side of the polarizer, and a release film disposed on the side opposite to the polarizer, sandwiching the first protective film, wherein the absorption coefficient A2 of the second protective film for light with a wavelength of 9.4 μm, as measured by the ATR method, is 1.0 × 10⁻⁶. 2 ~4.5×10 2is in μm, the polarizing plate has a cut end face, and in a cross section of the polarizing plate along the lamination direction, the inclination angle with respect to the lamination direction of a straight line connecting an end point P1 on the side opposite to the first protective film of the release film at the cut end face and an end point P2 on the side of the second protective film of the polarizer is 0.5 to 10°.

[0011] The method for manufacturing a polarizing plate of the present invention is a laminate including a polarizer, a first protective film disposed on one surface of the polarizer, a second protective film disposed on the other surface of the polarizer, and a release film disposed on a surface of the first protective film opposite to the polarizer, wherein a ratio A1 / A2 of an absorption coefficient A1 of light with a wavelength of 9.4 μm measured by the ATR method of the first protective film and an absorption coefficient A2 of light with a wavelength of 9.4 μm measured by the ATR method of the second protective film is 1 to 5, and a step of irradiating the laminate with laser light from the release film side to cut the laminate along the lamination direction of the laminate.

[0012] The method for manufacturing a display device of the present invention includes a step of attaching the polarizing plate of the present invention to at least one surface of a display element such that the second protective film faces the display element side.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an optical film, a polarizing plate, and a liquid crystal display device that can enhance the cutting property with laser light without causing light leakage in the display device.

Brief Description of the Drawings

[0014] [Figure 1] FIGS. 1A and B are cross-sectional views showing a part of a manufacturing process of a display device using a conventional polarizing plate. [Figure 2] FIGS. 2A and B are cross-sectional views showing a part of a manufacturing process of a display device using another conventional polarizing plate. [Figure 3]Figs. 3A and 3B are cross-sectional views showing part of the manufacturing process of a display device using a polarizing plate according to the present embodiment. [Figure 4] Fig. 4A is a cross-sectional view showing the configuration of a polarizing plate according to the present embodiment, and Fig. 4B is an enlarged view of the cut surface of Fig. 4A. [Figure 5] Figs. 5A to 5C are cross-sectional views showing the manufacturing process of a polarizing plate according to the present embodiment. [Figure 6] Fig. 6 is a cross-sectional view showing the configuration of a display device according to the present embodiment.

Mode for Carrying Out the Invention

[0015] The inventors of the present invention examined the cause of display unevenness occurring at the end of a display screen in a display device using a conventional polarizing plate (for example, the polarizing plate of Patent Document 1 or 2) cut with laser light, and found that it is related to the inclination angle of the cut end face of the polarizing plate after cutting with laser light. That is, although the mechanism causing the display unevenness at the end is not clear, it is presumed as follows.

[0016] Figs. 1A to 2B are cross-sectional views showing part of the manufacturing process of a display device using a conventional polarizing plate. Figs. 3A and 3B are cross-sectional views showing part of the manufacturing process of a display device using a polarizing plate according to the present embodiment.

[0017] (Influence of the inclination angle φ of the cut end face) When manufacturing a display device, a polarizing plate P with a release film cut with laser light is pressed and attached onto a display element C through an adhesive (not shown) or the like. In this case, as described in Patent Document 1 or 2, if the difference in laser light absorption between the two protective films 2 and 3 sandwiching the polarizer 1 is too large (specifically, if the laser light absorption of protective film 3 is extremely low compared to that of protective film 2), a slope (a slope that widens as it approaches the surface of the display element C (a slope in the positive direction)) is likely to be formed on the cut edge of the polarizing plate P (see Figure 1A). When a polarizing plate P with such a sloped cut edge is pressed and attached to the display element C, the slope remains even after attachment (see Figure 1B), which can easily cause display unevenness at the edges of the display screen due to refraction of light from the backlight, etc.

[0018] On the other hand, if a polarizing plate P with a straight cut edge is pressed onto the display element C (see Figure 2A), the cut edge of the polarizing plate P tends to tilt in the opposite direction (negative direction) after attachment (see Figure 2B). Therefore, similar to the above, uneven display is likely to occur at the edges of the display screen.

[0019] In contrast, the present invention makes the inclination of the cut end surface of the polarizing plate 10 before it is attached to the display element C gentler (see Figure 3A). Specifically, the inclination angle of the cut end surface of the polarizing plate 10 is adjusted to 0.5 to 10° in the cross section along the lamination direction of each film (see Figure 4B, described later). As a result, the inclination angle of the cut end surface of the polarizing plate after it is attached to the display element C can be made close to 0° (it can be made almost perpendicular to the surface of the display element C) (see Figure 3B), thus suppressing display unevenness at the edges of the display screen caused by the inclination angle (shape) of the cut end surface.

[0020] (Effects of internal stress caused by laser cutting) Furthermore, in a conventional polarizer like the one in Figure 2A (tilt angle φ=0°), there is almost no internal stress remaining in the protective film due to cutting. Therefore, when the polarizer tries to expand due to moisture absorption, there is almost no force to contract the protective film, and the tilt angle φ of the cut end of the polarizer tends to increase in the negative direction as described above, starting from the point of contact with the display element C (the cut end) (the amount of change in tilt angle φ due to humidity changes is large). On the other hand, in a polarizer like the one in Figure 1A (φ is excessive), a large amount of internal stress remains in the protective film due to laser cutting. Therefore, the force to contract the protective film becomes too large in response to the force to expand the polarizer due to moisture absorption, and the tilt angle φ tends to change in the positive direction as described above. In contrast, in the polarizing plate of the present invention as shown in Figure 3A, a moderate amount of internal stress remains in the protective film due to laser cutting. Therefore, a moderate force is easily generated that counteracts the force that causes the polarizer to expand due to moisture absorption, and the force does not become excessively large in either the negative or positive direction around the contact point with the display element C (the amount of change in the tilt angle φ due to humidity changes is small). As a result, optical unevenness after humid heat endurance can be further reduced.

[0021] The inclination angle of the cut end face of the polarizing plate 10 can be adjusted by any method. In particular, it is preferable to adjust the inclination angle of the cut end face of the polarizing plate 10 by the laser light absorbance of the first protective film 12 and the second protective film 13 and their ratio. Specifically, the ratio of the laser light absorbance of the first protective film 12 and the second protective film 13 is made appropriately small; that is, the absorption coefficient of the second protective film 13 for light with a wavelength of 9.4 μm is made appropriately large (1.0 × 10⁻⁶). 2 ~4.5×10 2 (Assuming / μm), and it is preferable to moderately reduce the ratio A1 / A2 between the absorption coefficient A1 of the first protective film 12 and the absorption coefficient A2 of the second protective film 13. The configuration of the present invention will be described below.

[0022] 1. Polarizing plate Figure 4A is a cross-sectional view showing the configuration of the polarizing plate 10 according to this embodiment, and Figure 4B is an enlarged view of the cross-section of Figure 4A. Note that the adhesive layer is not shown in Figures 4A and 4B.

[0023] As shown in Figures 4A and 4B, the polarizing plate 10 according to this embodiment includes a polarizer 11, a first protective film 12 disposed on one side thereof, a second protective film 13 disposed on the other side thereof, and a release film 14 disposed on the side opposite to the polarizer 11 via the first protective film 12. An adhesive layer (not shown) is disposed between the polarizer 11 and either the first protective film 12 or the second protective film 13.

[0024] 1-1. Polarizer 11 The polarizer 11 is an element that transmits only light with a specific polarization plane, and is a polyvinyl alcohol-based polarizing film. Polyvinyl alcohol-based polarizing films include those dyed with iodine and those dyed with dichroic dyes.

[0025] The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a 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 uniaxially stretching a polyvinyl alcohol-based film after dyeing it with iodine or a dichroic dye (preferably a film further treated for durability with a boron compound). The absorption axis of the polarizer is parallel to the direction of maximum stretching.

[0026] The thickness of the polarizer 11 is preferably 5 to 40 μm, and more preferably 5 to 30 μm, for example, in order to make the polarizer thinner.

[0027] 1-2. First protective film 12 The first protective film 12 is positioned on one surface of the polarizer 11, specifically between the polarizer 11 and the release film 14. When the device is assembled into a display device, the first protective film 12 is positioned on the side opposite to the display element (the side away from the display element) via the polarizer 11.

[0028] The resin constituting the first protective film 12 is not particularly limited and should be transparent and such that the ratio A1 / A2 of the absorption coefficients of the first protective film 12 and the second protective film 13 is below a certain level. Examples of such resins include polyester resin, (meth)acrylic resin, cellulose ester resin (such as TAC film), and cycloolefin resin. In particular, the first protective film preferably contains (meth)acrylic resin or cycloolefin resin.

[0029] ((meth)acrylic resin) The (meth)acrylic resin is preferably a polymer containing structural units derived from methyl methacrylate. The polymer may further contain structural units derived from monomers copolymerizable with methyl methacrylate. Examples of other monomers copolymerizable with methyl methacrylate include alkyl (meth)acrylates with 1 to 18 carbon atoms other than methyl methacrylate, such as 2-ethylhexyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrenes such as styrene and α-methylstyrene; maleic anhydride; maleimides such as maleimide and N-phenylmaleimide; and glutaric anhydride.

[0030] The content of structural units derived from methyl methacrylate relative to the total structural units constituting the above copolymer is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0031] (Cycloolefin resin) The cycloolefin resin can be the same as the cycloolefin resin contained in the second protective film 13 described later. That is, the composition of the cycloolefin resin contained in the first protective film may be the same as or different from the composition of the cycloolefin resin contained in the second protective film.

[0032] The weight-average molecular weight of (meth)acrylic resins and cycloolefin resins can be within the same range as that of the weight-average molecular weight of cycloolefin resins, as described later.

[0033] (Thickness) The thickness of the first protective film 12 is not particularly limited, but is preferably 20 to 70 μm, and more preferably 30 to 60 μm.

[0034] 1-3. Second protective film 13 The second protective film 13 is positioned on the other side of the polarizer 11. Specifically, when the device is assembled, the second protective film 13 is positioned between the display element and the polarizer 11 (on the side closer to the display element than the polarizer 11).

[0035] The material of the second protective film 13 is preferably such that the ratio A1 / A2 of the absorption coefficients of the first protective film 12 and the second protective film 13 is between 1 and 5. If A1 / A2 is 1 or greater, the polarizing plate can be cut more easily in a shorter time. On the other hand, if A1 / A2 is 5 or less, the second protective film 13 has an appropriate absorption of laser light (the laser light absorption of the second protective film 13 is not too low compared to the first protective film 12), which can reduce the amount of shrinkage due to cutting. As a result, the inclination angle of the cut end surface 10a of the resulting polarizing plate 10 can also be made smaller. From a similar viewpoint, the ratio A1 / A2 of the absorption coefficients is preferably 1.5 to 5.0, and more preferably 2.0 to 4.5.

[0036] The absorption coefficient A2 of the second protective film 13 at a wavelength of 9.4 μm is, as stated above, 1.0 × 10⁻⁶. 2 ~4.5×10 2It is preferably / μm. When the absorption coefficient A2 is 1.0×10 2 / μm or more, since the laser light can be appropriately absorbed, the cutting property by the laser light can be enhanced. From the viewpoint of hardly impairing the transparency and hardly causing light leakage in the display device, the absorption coefficient A2 of the second protective film 13 is 1.5×10 2 ~4.0×10 2 / μm, more preferably 2.0×10 2 ~3.5×10 2 / μm.

[0037] The absorption coefficient A1 of the first protective film 12 and the absorption coefficient A2 of the second protective film 13 can be measured by the following methods, respectively. Using a microscopic FTIR (Agilent's "UMA600" and "FTS3000"), by the ATR method (Attenuated Total Reflection method), incident light diameter: 100 μm, prism: Ge (incident angle 45°), detector: MCT-A, resolution: 4.0 cm -1 , integration: 64 times, the infrared absorption spectrum was measured. From the obtained infrared absorption spectrum, the absorbance of the portion corresponding to a wavelength of 9.4 μm (frequency 1041 cm -1 ) was read. Then, based on the following formula, the absorption coefficient of the film can be obtained. Absorption coefficient ( / μm) = Absorbance × loge10 / Film thickness (μm) The absorption coefficient of the film can be adjusted mainly by the composition of the film. [[ID=…]] The composition of the second protective film 13 is not particularly limited as long as it satisfies the above absorption characteristics, but it preferably contains a cycloolefin resin, and more preferably further contains a light absorption material. That is, the second protective film 13 preferably contains a cycloolefin resin and a light absorption material.

[0039] 1-3-1. Cycloolefin resin Cycloolefin resins are polymers that contain structural units derived from norbornene monomers. Norbornene monomers are represented by the following formula (1). [ka]

[0040] R in equation (1) 1 ~R 4 These represent a hydrogen atom, a halogen atom, a hydrocarbon group, or a polar group, respectively.

[0041] Examples of halogen atoms include fluorine atoms and chlorine atoms.

[0042] The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4, more preferably 1 or 2 carbon atoms. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, and butyl groups. The hydrocarbon group may further have a divalent linking group containing an oxygen atom, nitrogen atom, sulfur atom, or silicon atom (e.g., carbonyl group, imino group, ether bond, silyl ether bond, thioether bond, etc.).

[0043] Examples of polar groups include linking groups such as carboxyl groups, hydroxyl groups, alkoxy groups, alkoxycarbonyl groups, allyloxycarbonyl groups, amino groups, amide groups, and methylene groups (-(CH2) n This includes groups to which these groups are bonded via (where n is an integer of 1 or more). Among these, alkoxycarbonyl groups and aryloxycarbonyl groups are preferred, and alkoxycarbonyl groups are more preferred.

[0044] Among them, R 1 ~R 4Preferably, at least one of these is a polar group. This is because cycloolefin resins containing structural units derived from norbornene monomers having polar groups are easily dissolved in solvents when forming films, for example by solution casting, and the glass transition temperature of the resulting film is also easily increased. On the other hand, in melt deposition, the cycloolefin resin may not contain structural units derived from norbornene monomers having polar groups.

[0045] Also, R 1 ~R 4 Of these, R 1 and R 2 Both (or R 3 and R 4 Both of them may be hydrogen atoms.

[0046] In equation (1), p represents an integer between 0 and 2. From the viewpoint of improving the heat resistance of the second protective film, it is preferable that p is between 1 and 2.

[0047] Specific examples of norbornene monomers represented by formula (1) are shown below. Among these, the following are examples of norbornene monomers that have a polar group.

[0048] [ka]

[0049] Examples of norbornene monomers that do not have polar groups include the following: [ka]

[0050] The content of structural units derived from norbornene monomers can be 50 to 100 mol% relative to the total structural units constituting the cycloolefin resin.

[0051] The cycloolefin resin may further contain structural units derived from norbornene monomers and structural units derived from other copolymerizable monomers. Examples of other copolymerizable monomers include norbornene monomers without polar groups (if the norbornene monomer has polar groups) and cycloolefin monomers without a norbornene skeleton, such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0052] Commercially available cycloolefin resins may be used. Examples of commercially available products include ARTON® G, ARTON F, ARTON R, and ARTON RX manufactured by JSR Corporation.

[0053] The weight-average molecular weight Mw of the cycloolefin resin is not particularly limited, but is preferably between 20,000 and 300,000, more preferably between 30,000 and 250,000, and even more preferably between 40,000 and 200,000. When the weight-average molecular weight Mw of the cycloolefin resin is within the above range, the mechanical properties of the second protective film 13 can be improved without impairing moldability.

[0054] The weight-average molecular weight (Mw) of cycloolefin resins can be measured by gel permeation chromatography (GPC). Specifically, the measurement device used is a gel permeation chromatograph (HLC8220GPC manufactured by Tosoh Corporation), and the columns used are TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL manufactured by Tosoh Corporation, in series. Then, 20 ± 0.5 mg of the sample is dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution is injected into the above column (at 40°C), measured with a radioisotope detector at 40°C, and the weight-average molecular weight is determined by converting it to styrene equivalent.

[0055] The glass transition temperature (Tg) of cycloolefin resins is usually preferably 110°C or higher, more preferably 110 to 350°C, and even more preferably 120 to 250°C. When the Tg of a cycloolefin resin is 110°C or higher, deformation is less likely to occur even under high-temperature conditions. When the Tg is 350°C or lower, the moldability is less likely to be impaired, and thermal degradation of the cycloolefin resin during molding can be further suppressed.

[0056] The glass transition temperature can be measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0057] The content of the cycloolefin resin is not particularly limited, but it is preferably 50% by mass or more, and more preferably 70-99% by mass, relative to the second protective film 13.

[0058] 1-3-2. Light-absorbing materials The light-absorbing material is usually preferably a compound having a carbonyl group, and more preferably an ester compound or (meth)acrylic polymer particles.

[0059] <Ester compounds> The ester compound may be a sugar ester compound, a polycondensed ester compound, or a polyhydric alcohol ester compound.

[0060] (Sugar ester compounds) Sugar ester compounds are compounds in which all or part of the OH groups of a monosaccharide, disaccharide, or trisaccharide are esterified. Such sugar ester compounds are preferably compounds represented by the following formula (FA). [ka]

[0061] In formula (FA), R1 to R8 represent substituted or unsubstituted alkylcarbonyl groups, or substituted or unsubstituted arylcarbonyl groups. R1 to R8 may be the same or different from each other.

[0062] The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having two or more carbon atoms. Examples of substituted or unsubstituted alkylcarbonyl groups include methylcarbonyl group (acetyl group) and ethylcarbonyl group. Examples of substituents on the alkyl group include aryl groups such as phenyl group.

[0063] The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. An example of an arylcarbonyl group is the phenylcarbonyl group. An example of substituents on the aryl group is an alkyl group such as a methyl group.

[0064] Examples of R1 to R8 in formula (FA) include the following: [ka]

[0065] The average degree of substitution of the sugar ester compound is preferably 3 to 6. The average degree of substitution of the sugar ester compound indicates the average proportion of the total number of OH groups of the starting sugar that are esterified.

[0066] (Polyhydric alcohol ester compounds) Polyhydric alcohol esters are esterified products of a divalent or higher aliphatic polyhydric alcohol (preferably a divalent to 20valent aliphatic polyhydric alcohol) and a monocarboxylic acid.

[0067] Examples of polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol, with triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol being preferred.

[0068] The monocarboxylic acid is not particularly limited and may be any of the following: aliphatic monocarboxylic acids such as acetic acid and propionic acid, alicyclic monocarboxylic acids such as cyclopentanecarboxylic acid and cyclohexanecarboxylic acid, or aromatic monocarboxylic acids such as benzoic acid and toluic acid.

[0069] The carboxylic acid used in the polyhydric alcohol ester compound may be one type or a mixture of two or more types. Furthermore, all of the OH groups in the polyhydric alcohol may be esterified, or some may remain as OH groups.

[0070] The molecular weight of the sugar ester compound and the polyhydric alcohol ester compound depends on the method of producing the second protective film, but from the viewpoint of easily obtaining good compatibility with the cycloolefin resin, it is preferable that it be moderately low. Specifically, the molecular weight of the sugar ester compound and the ester compound can be, for example, 300 to 1500, preferably 600 to 1200.

[0071] (Polycondensed ester compounds) Polycondensed ester compounds are polycondensed polymers containing structural units obtained by reacting dicarboxylic acids and diols.

[0072] The dicarboxylic acid may be an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or an alicyclic dicarboxylic acid, and is preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be one type or a mixture of two or more types. It is preferable to mix aromatic dicarboxylic acids and aliphatic dicarboxylic acids.

[0073] The diol may be an aromatic diol, an aliphatic diol, or an alicyclic diol, preferably an aliphatic diol, and more preferably a diol having 1 to 4 carbon atoms. The diol may be one type or a mixture of two or more types.

[0074] In other words, the polycondensed ester compound preferably contains a structural unit obtained by reacting a dicarboxylic acid, including an aromatic dicarboxylic acid, with a diol having 1 to 8 carbon atoms, and more preferably contains a structural unit obtained by reacting a dicarboxylic acid, including an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid, with a diol having 1 to 8 carbon atoms. Both ends of the polycondensed ester molecule may or may not be sealed.

[0075] Among these ester compounds, sugar ester compounds are particularly preferred because they have a moderately low molecular weight and excellent compatibility with cycloolefin resins.

[0076] <(meth)acrylic polymer particles> (Meth)acrylic polymer particles are polymer particles containing structural units derived from (meth)acrylates, and preferably polymer particles containing structural units derived from methyl methacrylate.

[0077] Polymers containing structural units derived from methyl methacrylate may further contain structural units derived from other copolymer monomers. Examples of other copolymer monomers include alkyl(meth)acrylates having 1 to 18 carbon atoms other than methyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrenes such as styrene and α-methylstyrene; polyfunctional (meth)acrylic acid esters having two or more (meth)acrylic groups, such as (poly)ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; and polyfunctional monomers such as allyl(meth)acrylate and allylalkyl(meth)acrylates.

[0078] In particular, the polymer is preferably a crosslinked polymer, that is, a copolymer containing structural units derived from methyl methacrylate and structural units derived from polyfunctional monomers; more preferably, it is a copolymer containing structural units derived from methyl methacrylate, structural units derived from styrenes, and structural units derived from polyfunctional monomers.

[0079] From the viewpoint of increasing the laser light absorption rate of the second protective film 13, it is preferable that the content of structural units derived from (meth)acrylates containing carbonyl groups is above a certain level. From this viewpoint, the total amount of structural units derived from methyl methacrylate is preferably 30 mol% or more, and more preferably 50 to 80 mol%, relative to the total structural units constituting the polymer.

[0080] The content of structural units derived from polyfunctional monomers is preferably 3 to 50 mol%, and more preferably 10 to 35 mol%, relative to the total amount of structural units constituting the polymer.

[0081] The (meth)acrylic polymer particles are preferably polymers with a refractive index difference of 0.01 or less from that of the cycloolefin resin. Such (meth)acrylic polymer particles are less likely to reduce the transparency of the resulting second protective film.

[0082] The refractive indices of cycloolefin resin and (meth)acrylic polymer particles can each be the refractive index of light at a wavelength of 550 nm. The refractive index of light at a wavelength of 550 nm can be determined, for example, by preparing a sample film containing each component individually and measuring the refractive index of the sample film at a wavelength of 550 nm using a Horiba UVSEL spectroscopic ellipsometer.

[0083] The Tg of (meth)acrylic polymer particles is preferably 80°C or higher. The Tg of (meth)acrylic polymer particles can be measured in accordance with JIS K 7121-2012 or ASTMD 3418-82, as described above.

[0084] The average particle size of the (meth)acrylic polymer particles is not particularly limited, but is preferably, for example, 50 to 500 nm. When the average particle size is within the above range, it is possible to increase the absorption rate of laser light while forming irregularities of an appropriate size on the surface of the film, thereby imparting slipperiness. From the above viewpoint, the average particle size of the (meth)acrylic polymer particles is more preferably 0.07 to 0.28 μm.

[0085] The average particle size of (meth)acrylic polymer particles in the second protective film 13 can be measured by the following method. First, the second protective film 13 is cut, and the resulting cut surface is observed using TEM. Then, the particle size of 100 arbitrary particles is measured. The particle size is measured as the equivalent circle diameter of 100 particles obtained by TEM imaging, as described above. The average value of the obtained particle sizes is then defined as the "average particle size." In the TEM image, areas with a brightness of 150% or more of the average brightness of the field of view are identified as particles.

[0086] The amount of light-absorbing material can be set such that the ratio A1 / A2 of the absorption coefficients of the second protective film 13 and the first protective film 12 satisfies the above range, and the absorption coefficient A2 of the second protective film 13 satisfies the above range.

[0087] For example, it is preferable that the mass-based content of the light-absorbing material in the second protective film 13 is greater than the mass-based content of the light-absorbing material in the first protective film 12.

[0088] Specifically, the content of the light-absorbing material is preferably 0.5 to 10% by mass relative to the resin. When the content of the light-absorbing material is within the above range, it is easy to adjust the ratio of the absorption coefficients A1 / A2 within the above range while keeping the absorption coefficient A2 of the second protective film 13 within the above range. This makes it easy to adjust the inclination angle of the cut end surface 10a of the resulting polarizing plate 10 within the above range while moderately increasing the cutability of the second protective film 13 by laser light. From a similar viewpoint, it is more preferable that the content of the light-absorbing material is 1 to 6% by mass relative to the resin.

[0089] 1-3-3. Other ingredients The second protective film 13 may further contain other components, such as inorganic fine particles, as needed.

[0090] Inorganic fine particles have the function of improving the slipperiness of the second protective film 13. Examples of inorganic materials that constitute the inorganic fine particles include oxides such as silicon dioxide (SiO2), titanium dioxide, aluminum oxide, and zirconium oxide. Among these, silicon dioxide is preferred because it can reduce the increase in film haze. Examples of commercially available silicon dioxide particles include Aerosil R812, R972 (manufactured by Nippon Aerosil Co., Ltd.), and NanoTek SiO2 (manufactured by CI Chemicals Co., Ltd.).

[0091] The average primary particle diameter of the inorganic fine particles is preferably 5 to 50 nm. If the average primary particle diameter of the inorganic fine particles is 5 nm or more, the surface of the film can be roughened, making it easier to impart slipperiness, and if it is 50 nm or less, it is easier to suppress the increase of haze. The average primary particle diameter of the inorganic fine particles is more preferably 5 to 30 nm. The average primary particle diameter of the inorganic fine particles in the second protective film 13 can be measured by the same method as described above.

[0092] The content of inorganic fine particles is not particularly limited, but may be 0 to 5% by mass, preferably 0 to 2% by mass, relative to the second protective film 13.

[0093] 1-3-4. Physical Properties (Total light transmittance) The total light transmittance of the second protective film 13 is not particularly limited as long as it has sufficient light transmittance, but it is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The total light transmittance of the second protective film 13 can be measured in accordance with JIS K7361-1:1997.

[0094] The total light transmittance of the second protective film 13 can be adjusted by, for example, the amount of light-absorbing material it contains. To increase the total light transmittance of the second protective film 13, it is preferable to keep the amount of light-absorbing material below a certain level.

[0095] (Phase difference Ro and Rt) The second protective film 13 may have phase difference values ​​Ro and Rt depending on its application. For example, the in-plane phase difference Ro of the second protective film 13, measured at a measurement wavelength of 590 nm and under conditions of 23°C and 55% RH, preferably satisfies 40 nm ≤ Ro ≤ 60 nm, and the phase difference Rt in the thickness direction preferably satisfies 115 nm ≤ Rt ≤ 145 nm. Such a second protective film 13 is suitable, for example, as a phase difference film to be combined with a VA-type liquid crystal cell.

[0096] Ro and Rt are defined by the following formulas, respectively. Equation (2a): Ro = (nx - ny) × d Equation (2b): Rt = ((nx + ny) / 2 - nz) × d (In the formula, nx represents the refractive index of the second protective film 13 in the in-plane slow axis direction (the direction in which the refractive index is maximum). ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the second protective film 13. nz represents the refractive index in the thickness direction of the second protective film 13. 'd' represents the thickness (nm) of the second protective film 13.

[0097] The in-plane slow axis of the second protective film 13 refers to the axis on the film surface where the refractive index is maximum. The in-plane slow axis of an optical film can be confirmed using an automatic birefringence meter, AxoScanMueller Matrix Polarimeter (manufactured by Axonometrics).

[0098] Ro and Rt can be measured using the following method. 1) The second protective film 13 is conditioned for 24 hours in an environment of 23°C and 55% RH. The average refractive index of this optical film is measured using an Abbe refractometer, and its thickness d is measured using a commercially available micrometer. 2) The phase difference Ro and Rt of the second protective film 13 after humidity control are measured at a measurement wavelength of 590 nm using an automated birefringence meter AxoScan (AxoScanMueller Matrix Polarimeter: Axometrics Corporation) in an environment of 23°C and 55% RH.

[0099] The phase difference Ro and Rt of the second protective film 13 can be adjusted mainly by the stretching ratio. To increase the phase difference Ro and Rt of the second protective film 13, it is preferable to increase the stretching ratio.

[0100] (Thickness) The thickness of the second protective film 13 is not particularly limited, but is preferably 20 to 70 μm, and more preferably 30 to 45 μm. The ratio t1 / t2 of the thickness t2 of the second protective film 13 to the thickness t1 of the first protective film 12 is not particularly limited, but can be, for example, 1 to 5.

[0101] 1-3-5. Manufacturing method The first protective film 12 and the second protective film 13 may be manufactured by any method, for example, by a molten casting method or a solution casting method.

[0102] In the molten casting method, a cast film is obtained by casting a hot molten thermoplastic resin composition and then cooling and solidifying it. Specifically, it can be obtained through the following steps: A1) preparing the thermoplastic resin composition, A2) casting the hot molten thermoplastic resin composition and then cooling and solidifying it, and A3) stretching the obtained film if necessary.

[0103] In step A1), the components of the protective film are dry-blended and then melt-kneaded using a twin-screw extruder or the like to obtain pellets.

[0104] In step A2), the prepared thermoplastic resin composition pellets are melt-kneaded using a twin-screw extruder or the like, and then cast from a casting die. The thermal melting temperature in molten casting can be (Tg+30) to (Tg+70)°C, where Tg is the glass transition temperature of the resin.

[0105] In step A3), stretching may be performed according to the required optical properties, and it is preferable to stretch in one or more directions from the width direction (TD direction), transport direction (MD direction), and oblique direction.

[0106] The stretching ratio is set according to the required optical performance; for example, from the viewpoint of making it function as a low phase difference film, it can be set to 1.01 to 1.3 times. The stretching ratio is defined as (stretched size of the film after stretching) / (stretched size of the film before stretching). The stretching temperature (drying temperature during stretching) is preferably (Tg-20) to (Tg+30)°C.

[0107] (Solution casting method) In the solution casting method, a solution (dope) containing the components of the protective film dissolved in a solvent is cast, and then dried to obtain a cast film. Specifically, it can be manufactured by the following steps: B1) preparing a dope containing a cycloolefin resin, a light-absorbing material, and a solvent; B2) casting the obtained dope onto a support, followed by drying and peeling to obtain a cast film; and, if necessary, B3) stretching the obtained cast film.

[0108] In step B1), the cycloolefin resin and the light-absorbing material are dissolved or dispersed in a solvent to prepare the dope. The solvent used includes at least an organic solvent (good solvent) capable of dissolving the cycloolefin resin. Examples of good solvents include chlorinated organic solvents such as methylene chloride and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran, with methylene chloride being preferred. The solvent used may further include poor solvents such as aliphatic alcohols with 1 to 4 carbon atoms, such as methanol and ethanol, from the viewpoint of improving the peelability of the cast film from the support.

[0109] In step B2), the obtained dope is extruded, for example, from a casting die and cast onto a support. Then, the solvent is evaporated from the dope cast onto the support, and the dope is peeled off to obtain a cast film.

[0110] In step B3), the obtained cast film is stretched. The stretching ratio and stretching temperature can be the same as in step A3 above.

[0111] 1-4. Release film 14 The release film 14 is a film that protects the first protective film 12 and is peeled off when in use.

[0112] The type of release film 14 is not particularly limited and can be any film that can be peeled off at the time of use. The absorption coefficient of the release film 14 at a wavelength of 9.4 μm is not particularly limited, but is usually higher than that of the second protective film 13 and is often about the same as or higher than that of the first protective film 12. The release film 14 is, for example, a release film that has been treated with a mold release agent, and examples of such films include plastic films such as acrylic film, polycarbonate film, polyester film, and fluororesin film.

[0113] (Thickness) The thickness of the release film 14 is not particularly limited, as long as it can protect the first protective film 12, but it is preferably 20 to 60 μm, and more preferably 30 to 50 μm.

[0114] 1-5.Adhesive layer An adhesive layer (not shown) is placed between the polarizer 11 and the first protective film 12, or between the polarizer 11 and the second protective film 13, to bond them together.

[0115] The adhesive constituting the adhesive layer is not particularly limited and may be a dried aqueous solution of fully saponified polyvinyl alcohol (water glue) or a cured product of an active energy ray-curable adhesive. The active energy ray-curable adhesive may be a photoradical polymerization type composition utilizing photoradical polymerization, a photocationic polymerization type composition utilizing photocationic polymerization, or a combination thereof.

[0116] The thickness of the adhesive layer can be, for example, 0.01 to 10 μm, preferably about 0.03 to 5 μm.

[0117] 1-6. Physical Properties (Angle of inclination) The polarizing plate 10 having the above configuration has a cut end surface 10a cut by laser light (see Figure 4B). In the cross-section of the polarizing plate 11 along the stacking direction L0 (thickness direction of the polarizing plate 11) (specifically, the cross-section along the stacking direction L0 and perpendicular to the cut end surface 10a), the inclination angle φ of the straight line L1 connecting the endpoint P1 of the release film 14 on the side opposite to the first protective film 12 and the endpoint P2 of the polarizer 11 on the second protective film 15 side with respect to the stacking direction L0 is 0.5 to 10°. When the inclination angle φ is 0.5° or more, when the polarizing plate 11 is attached to the display element with the second protective film 13 side facing the display element and pressed, it is easy to make the inclination of the cut end surface 10a almost zero. As a result, when used as a display device, even if the ambient humidity and heat change, light leakage caused by the shape of the cut end surface 10a of the polarizing plate 10 can be suppressed. From a similar viewpoint, the above-mentioned inclination angle φ is more preferably 1 to 10°, and even more preferably 6 to 8°.

[0118] The cut end surface 10a of the polarizing plate 10 can be observed using an optical microscope. Specifically, the tilt angle is measured from the image obtained by observing the cut surface of a sample cut perpendicular to the cut end surface 10a of the polarizing plate 10 using an optical microscope.

[0119] 2. Method for manufacturing polarizing plates Figures 5A to 5C are cross-sectional views showing the manufacturing method of the polarizing plate 10 according to this embodiment.

[0120] As shown in Figures 5A to 5C, the method for manufacturing the polarizing plate 10 according to this embodiment includes the steps of: 1) preparing a laminate 20 including a polarizer 11, a first protective film 12, a second protective film 13, and a release film 14 (see Figure 5A); and 2) irradiating the laminate 20 with laser light from the release film 14 side to cut the laminate 20 along the lamination direction (thickness direction) (see Figures 5B and 5C).

[0121] Regarding step 1) First, a laminate 20 is prepared, which includes a polarizer 11, a first protective film 12, a second protective film 13, and a release film 14 (see Figure 5A).

[0122] The polarizer 11 and the first protective film 12 or the second protective film 13 can be bonded together using the above-mentioned adhesive in a roll-to-roll manner.

[0123] Regarding step 2) Next, the surface of the resulting laminate 20 (specifically the surface of the release film 14) is irradiated with laser light to cut the laminate 20 along the lamination direction (see Figures 5B and 5C).

[0124] Laser cutting is performed by irradiating the laminate 20 with laser light L from the release film 14 side. In this embodiment, the ratio A1 / A2 of the absorption coefficients of the first protective film 12 and the second protective film 13 is appropriately adjusted (the absorption coefficient A2 of the second protective film 13 is moderately larger than in the conventional method). As a result, excessive energy is not required during cutting, and the amount of shrinkage of the film on the side irradiated by the laser light L (especially the first protective film 12) can be reduced. Therefore, the inclination angle φ of the cut end surface 10a of the polarizing plate 10 after cutting can be made smaller than in the conventional method (see Figure 5C).

[0125] 3. Display device and method for manufacturing the same The display device according to this embodiment has a display element and a polarizing plate disposed on at least one of its surfaces.

[0126] The type of display element is not particularly limited and may be an organic EL display element or a liquid crystal display element. In this embodiment, it is preferable that the display element is a liquid crystal display element.

[0127] Figure 6 is a cross-sectional view showing the configuration of the display device according to this embodiment.

[0128] As shown in Figure 6, the display device 100 according to this embodiment includes a liquid crystal display element 30 (display element), a first polarizing plate 40 disposed on one side of the liquid crystal display element 30 (e.g., the viewing side), and a second polarizing plate 50 disposed on the other side of the liquid crystal display element 30 (e.g., the backlight side).

[0129] The liquid crystal display element 30 may have two transparent substrates 31 and 31 and a liquid crystal layer 32 disposed between them. The display mode of the liquid crystal display element 30 is not particularly limited and may be, for example, STN (Super-Twisted Nematic), TN (Twisted Nematic), OCB (Optically Compensated Bend), HAN (Hybridaligned Nematic), VA (Vertical Alignment, MVA (Multi-domain Vertical Alignment), PVA (Patterned Vertical Alignment)), IPS (In-Plane-Switching), etc. Among these, the VA mode is preferred.

[0130] In this embodiment, one or both of the first polarizing plate 40 and the second polarizing plate 50 are polarizing plates 10 according to this embodiment. In this embodiment, both the first polarizing plate 40 and the second polarizing plate 50 are polarizing plates 10 according to this embodiment. In this embodiment, it is preferable that the polarizing plate 10 is arranged so that the second protective film 13 faces the liquid crystal display element 30.

[0131] The display device configured in this way is manufactured by a process of attaching the polarizing plate 10 according to this embodiment to at least one surface of the display element. The attachment can be performed by pressing the polarizing plate 10 so that the second protective film 13 faces the display element side.

[0132] In the display device 100 according to this embodiment, the cut end surface 10a of the polarizing plate 10 attached to the liquid crystal display element 30 is almost parallel to the stacking direction (almost perpendicular to the surface of the liquid crystal display element 30) and is hardly tilted. Therefore, display unevenness at the edges caused by the tilt angle of the cut end surface 10a of the polarizing plate 10 can be suppressed. Furthermore, such a polarizing plate 10 shows less change in the tilt angle φ due to changes in the humid heat conditions of the usage environment compared to conventional polarizing plates (Figure 2A) where the tilt angle of the cut end surface of the polarizing plate before attachment is approximately 0°, or polarizing plates with too large a φ (Figure 1A). Therefore, display unevenness at the edges after storage in humid heat can be further suppressed. [Examples]

[0133] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0134] 1. Materials of the first protective film and the second protective film (1) Resin Cycloolefin resin A (COP-A, Tg: 162℃, Mw: 100,000, Ethylene: unit 1: unit 2 = 50:28:22 molar ratio) [ka] Cycloolefin resin B (COP-B, Tg: 170℃, Mw: 100,000) [ka] (Meth)acrylic resin (Acr): Polymethyl methacrylate (PMMA, Tg: 110℃, Mw: 300,000)

[0135] The Tg and Mw of the resin were measured by the following method.

[0136] [Glass transition temperature (Tg)] The glass transition temperature of the resin was measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0137] [Weight average molecular weight (Mw)] The weight-average molecular weight (Mw) of the resin was measured using gel permeation chromatography (HLC8220GPC, Tosoh Corporation) and columns (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL, Tosoh Corporation, in series). 20 ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into the column (at 40°C), and the measurement was performed at a detector RI temperature of 40°C. The weight-average molecular weight was then calculated by converting it to styrene equivalent.

[0138] (2) Light-absorbing materials Light-absorbing material A: [ka] Light-absorbing material B: Methyl methacrylate (MMA) / styrene (St) / ethylene glycol dimethacrylate (EGDMA) (70 / 10 / 20 molar ratio) copolymer particles (refractive index 1.51, average particle diameter 0.14 μm)

[0139] 2. Preparation or manufacturing of the first protective film <Preparation of Film 101> (Preparation of light-absorbing material-added solution) 95 parts by mass of methylene chloride were placed in a sealed container, and 4.5 parts by mass of light-absorbing material A were added while stirring. The mixture was then stirred and mixed in a dissolver for 50 minutes. 2000 g of the resulting mixture was passed through a high-pressure dispersion device (product name: Ultra-high pressure homogenizer M110-E / H, manufactured by Microfluidics Corporation) and treated once at 175 MPa to prepare a light-absorbing material dispersion. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a light-absorbing material-added solution.

[0140] (Preparation of dope) A dope with the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. To this, the dried acrylic resin and the above-mentioned light-absorbing material additive solution (light-absorbing material) were added while stirring, heated, and stirred until completely dissolved. This was filtered using Asaka Filter Paper No. 244 manufactured by Asaka Filter Paper Co., Ltd. to prepare the dope. Dichloromethane: 300 parts by mass Ethanol: 43 parts by mass PMMA (Polymethyl Methacrylate): 60 parts by mass Light-absorbing material additive solution (light-absorbing material A): 60 parts by mass

[0141] (Film forming) Next, using an endless belt casting apparatus, the dope was uniformly cast onto a stainless steel belt support at a temperature of 22°C and a width of 1500 mm. The solvent was evaporated on the stainless steel band support until the residual solvent content was 45%, and the dope was peeled off the stainless steel band support while adjusting the peeling speed to achieve a tension of 162 N / m. The cast film obtained by peeling was stretched in a longitudinal stretching apparatus at 35°C while the solvent was evaporated. It was slit to a width of 1.2 m, and then dried at a temperature of 135°C while being stretched 1.1 times in the width direction with a tenter. After that, it was wound up to obtain a film 101 with a thickness of 40 μm.

[0142] <Preparation of films 102-104> Films 102 to 104 were obtained in the same manner as film 101, except that the type and content of the light-absorbing material were changed as shown in Table 1.

[0143] <Film 105> Toyobo Co., Ltd. CosmoShine (registered trademark)

[0144] <Film 106> 100 parts by mass of cellulose triacetate (TAC) with an acetyl group substitution degree of 2.92 and a viscosity-average degree of polymerization of 300, 2 parts by mass of ethyl phthalyl ethyl glycolate, 10 parts by mass of triphenyl phosphate, 350 parts by mass of methylene chloride, and 50 parts by mass of ethanol were placed in a sealed container. The mixture was slowly stirred and gradually heated to 45°C over 60 minutes until dissolved. The atmosphere inside the container became 1.2 atmospheres. This dope was filtered using Asaka Filter Paper No. 244 manufactured by Asaka Filter Paper Co., Ltd., and then allowed to stand for 24 hours to remove bubbles from the dope.

[0145] Separately, 5 parts by mass of the above-mentioned cellulose triacetate, 3 parts by mass of Chinuvin 326 (manufactured by BASF Japan Ltd.), 7 parts by mass of Chinuvin 109 (manufactured by BASF Japan Ltd.), 5 parts by mass of Chinuvin 171 (manufactured by BASF Japan Ltd.), and 1 part by mass of AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) were mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol, stirred, and dissolved to prepare an ultraviolet absorber solution. The ultraviolet absorber solution was added to 100 parts by mass of the above dope at a ratio of 2 parts by mass, thoroughly mixed with a static mixer, and then cast from the die onto a stainless steel belt at a dope temperature of 35°C. After drying on the temperature-controlled stainless steel belt for 1 minute by contacting the back surface of the stainless steel belt with warm water at 35°C, cold water at 15°C was then contacted on the back surface of the stainless steel belt and held for 15 seconds before being peeled off the stainless steel belt.

[0146] The amount of residual solvent in the web at the time of peeling was 70% by mass. The peeled web was then dried at 120°C for 10 minutes while fixing both ends to obtain a film 106 with a thickness of 80 μm.

[0147] The absorption coefficient A1 of the obtained films 101 to 106 was measured by the following method.

[0148] [absorption coefficient] The obtained film was analyzed using the ATR method with a microscopic FTIR (Agilent "UMA600" and "FTS3000"), with an incident light diameter of 100 μm, a Ge prism (incident angle 45°), an MCT-A detector, and a resolution of 4.0 cm².-1 The infrared absorption spectrum was measured under the condition of 64 cumulative measurements. From the obtained infrared absorption spectrum, the portion corresponding to a wavelength of 9.4 μm (frequency 1041 cm⁻¹) was identified. -1 The absorbance of the film was read. Then, the absorption coefficient of the film was determined based on the following formula. Absorption coefficient ( / μm) = Absorbance × log10 / Film thickness (μm)

[0149] The composition and physical properties of the obtained films 101 to 106 are shown in Table 1.

[0150] [Table 1]

[0151] 3. Preparation of the second protective film <Production of Film 201> (Pellet preparation) COP-A and light-absorbing material A were mixed in a vacuum Nauter mixer so that the content of light-absorbing material A was 2.8% by mass relative to COP-A. After drying, the mixture was melted using a twin-screw extruder to obtain resin mixture pellets.

[0152] (Ryuen) The obtained pellets were fed into an extruder under a nitrogen atmosphere and melt-cast. The melt-extruded film was then cooled with a cooling roll, stretched at 160°C and 140%, and peeled off with a release roll to obtain a film 201 with a thickness of 40 μm.

[0153] <Preparation of Film 202> Film 202 was obtained in the same manner as film 201, except that the content of the light-absorbing material was changed as shown in Table 2.

[0154] <Preparation of films 203 and 207> Films 203 and 207 were obtained in the same manner as film 201, except that COP-A:100 parts by mass was changed to a mixture of COP-A:50 parts by mass and COP-B:50 parts by mass, and the content of the light-absorbing material was changed as shown in Table 2.

[0155] <Preparation of film 204> Film 204 was obtained in the same manner as film 201, except that the stretching temperature was changed to 180°C and the stretching ratio to 200%.

[0156] <Film 205> Film 205 was obtained in the same manner as film 201, except that the type and content of the light-absorbing material were changed as shown in Table 2.

[0157] <Preparation of films 206 and 208> Films 206 and 208 were obtained in the same manner as film 201, except that no light-absorbing material was added and the film thickness was changed by adjusting the stretching conditions as shown in Table 2.

[0158] <Preparation of film 209> (Preparation of light-absorbing material-added solution) 95 parts by mass of methylene chloride were placed in a sealed container, and 2.8 parts by mass of light-absorbing material A were added while stirring. The mixture was then stirred and mixed in a dissolver for 50 minutes. 2000 g of the resulting mixture was passed through a high-pressure dispersion device (product name: Ultra-high pressure homogenizer M110-E / H, manufactured by Microfluidics Corporation) and treated once at 175 MPa to prepare a light-absorbing material dispersion. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a light-absorbing material-added solution.

[0159] (Preparation of dope) A dope with the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. COP-A (cycloolefin resin) and the above-mentioned light-absorbing material additive solution (light-absorbing material) were added while stirring, heated, and stirred until completely dissolved. This was then filtered using Asaka Filter Paper No. 244 manufactured by Asaka Filter Paper Co., Ltd. to prepare the dope. Dichloromethane: 300 parts by mass Ethanol: 19 parts by mass COP-B (cycloolefin resin): 100 parts by mass Light-absorbing material additive solution (light-absorbing material A): 98 parts by mass

[0160] (Film forming) Next, using an endless belt casting apparatus, the dope was uniformly cast onto a stainless steel belt support at a temperature of 33°C and a width of 1500 mm. The temperature of the stainless steel belt was controlled to 30°C. After evaporating the solvent in the dope cast onto the stainless steel belt support until the residual solvent content was 30% by mass, the dope was peeled off the stainless steel belt support with a peeling tension of 130 N / m. The peeled and cast film was stretched in the width direction (TD direction) at a stretch ratio of 50% under conditions of 160°C (resin Tg - 10°C). The residual solvent at the start of stretching was 10% by mass. Next, it was dried at 130°C while being transported through a drying zone with multiple rollers. After that, it was wound up to obtain a film 209 with a thickness of 40 μm.

[0161] The extinction coefficient A2 of the obtained films 201-209 was measured using the same method as described above. The average absorptivity of the obtained films 201-209 was also measured using the following method.

[0162] [Average absorption rate] The absorbance of the film was measured using the method described above. Absorbance = Absorption coefficient ( / μm) × Film thickness (μm) / log10 The average absorption rate was measured by substituting the obtained values ​​into the following formula. Average absorptivity (%) = 100 - 10^(2 - absorbance)

[0163] The composition and physical properties of the obtained films 201-209 are shown in Table 2.

[0164] [Table 2]

[0165] 3. Fabrication of polarizing plates <Examples 1-9 and Comparative Examples 1-6> (Fabrication of polarizers) A polyvinyl alcohol resin film (PVA) with a degree of polymerization of 2400 and a degree of saponification of 99.7 mol% was prepared. The film was stretched three times in the film transport direction while being stained in an iodine aqueous solution at 30°C, and then stretched again in an aqueous solution of 4% boric acid and 5% potassium iodide at 60°C until the total stretching ratio was six times the original length. Furthermore, the stretched film was washed by immersing it in an aqueous solution of 2% potassium iodide at 30°C for several seconds. The resulting stretched film was dried at 90°C to obtain a polarizer with a thickness of 25 μm.

[0166] (Fabrication of laminates) A polyethylene terephthalate film (PET film) with a thickness of 40 μm was attached to one side of the first protective film shown in Table 3 using an adhesive as a release liner. On the other side of this first protective film, a polarizer and the second protective film shown in Table 3 were laminated and bonded together using an acrylic UV-curing adhesive to create a laminate. The thickness of the adhesive layer was 1 μm.

[0167] (Cutting of the laminate) The surface of the release film of the obtained laminate was irradiated with a carbon dioxide laser with a wavelength of 9.4 μm to cut the laminate and obtain a polarizing plate. The cutting conditions were a frequency of 20 kHz, an output of 59 W, and a speed of 60 m / min.

[0168] (evaluation) The cross-sectional shape, productivity, and display characteristics of the obtained polarizing plates were evaluated using the following method.

[0169] 1) Shape of the cut end surface of the polarizing plate The obtained polarizing plate was cut using a cutting machine perpendicular to the cut end surface and along the film lamination direction (thickness direction of the polarizing plate). The inclination angle φ of the laser-cut end surface of the polarizing plate on the cut surface was observed with an optical microscope (see Figure 4B). Then, in the above cross-section, the angle φ of the straight line L1 connecting the end point P1 of the release film on the opposite side of the first protective film and the end point P2 on the second protective film side of the polarizer with respect to the lamination direction L0 was measured.

[0170] 2) Productivity The resulting laminate was cut with a laser beam to prepare 100 polarizing plates measuring 300 × 210 × 0.1 mm. For each polarizing plate, the peelability of the PET film was measured using a 90° peel test with adhesive tape and evaluated according to the following criteria. ◎: No peeling defects. ○: It can be peeled off, but there is a small amount of residue remaining, though it is not a problem. △: Can be peeled off, but some residue occasionally remains, which is a minor issue. ×: While peeling is possible, residual peeling occurs on many polarizing plates, which is problematic. ○ or higher was considered satisfactory.

[0171] 3)Display characteristics The polarizing film that was pre-attached to a Sony KLV-40J3000 40-inch display, a VA-type liquid crystal display device, was carefully peeled off. Then, a laser-cut polarizing film was attached so as to match the transmission axis of the original polarizing film, and a liquid crystal display device was fabricated. Specifically, the laser-cut polarizing film was placed on the glass substrate of the liquid crystal cell (liquid crystal display element) using adhesive, with its second protective film facing the glass substrate side, and then pressed into place. This resulted in the creation of a liquid crystal display device.

[0172] The obtained liquid crystal display devices were then stored for 500 hours in an environment of 60°C and 90RH. Before storage (initial state) and after storage (after humid heat endurance), the entire screen of the display device was visually observed in a darkroom with a black display, and the display unevenness (light leakage) at the edges of the display screen was evaluated. The display unevenness at the edges before storage (initial state) and after storage (after humid heat endurance) was evaluated according to the following criteria.

[0173] (initial) ◎: No light leakage was observed during visual inspection from a 45° angle from the front. ○: A slight light leak is observed during visual inspection from a 45° angle from the front, but it is at an acceptable level. △: Light leakage was observed during visual inspection from a 45° angle from the front, indicating a problematic level of leakage. ×: Significant light leakage was observed during visual inspection from a 45° angle from the front, indicating a problematic level of light leakage. ○ or higher was considered satisfactory.

[0174] (after saving) ◎: No light leakage was observed during visual inspection from a 45° angle from the front, similar to the pre-storage state. ○: Compared to before storage, slight light leakage is observed when visually inspected from a 45° angle from the front, but it is at an acceptable level. △: Compared to before preservation, light leakage was observed when visually inspected from a 45° angle from the front, indicating a problematic level of leakage. ×: Compared to before storage, significant light leakage was observed when visually inspected from a 45° angle from the front, reaching a problematic level. ○ or higher was considered satisfactory.

[0175] The evaluation results for Examples 1-9 and Comparative Examples 1-6 are shown in Table 3. [Table 3]

[0176] As shown in Table 3, in all of the polarizing plates of Examples 1 to 9, where the absorption coefficient A2 of the second protective film is below a certain level and the ratio of the absorption coefficients A1 / A2 of the first and second protective films is below a certain level, the inclination angle φ of the cut edge surface of the laser-cut portion is small, ranging from 0.5 to 10°. Furthermore, it can be seen that liquid crystal display devices using these polarizing plates suppress display unevenness at the edges of the screen and have good peelability of the PET film of the polarizing plate.

[0177] In contrast, the polarizers of Comparative Examples 1 and 3, which have a large ratio of the absorption coefficients A1 / A2 between the first and second protective films, all show a large inclination angle φ of the cut edge surface of the laser-cut portion, exceeding 12°. Furthermore, liquid crystal display devices using these polarizers exhibit uneven display at the initial edges. Also, the absorption coefficient A2 of the second protective film is 1.0 × 10⁻⁶. 2 ~4.5×10 2In Comparative Example 2, the polarizing plate exceeding the range of / μm has a small inclination angle φ of the cut edge surface of the laser-cut portion (less than 0.5°). Therefore, when bonded to a liquid crystal display device, the inclination angle of the cut edge surface after bonding is no longer perpendicular to the bonding surface due to the effect of pressing pressure. As a result, it can be seen that liquid crystal display devices using this polarizing plate will exhibit uneven display at the initial edges.

[0178] Furthermore, in the liquid crystal display device of Comparative Example 2, where the initial inclination angle φ of the cut edge of the polarizing plate is close to 0°, display unevenness at the edges is more likely to occur, mainly after storage with moist heat (see Figure 2A); in the liquid crystal display device of Comparative Example 1, where the initial inclination angle φ of the cut edge of the polarizing plate exceeds 10°, display unevenness at the initial edges is mainly observed (see Figure 1A).

[0179] Furthermore, in the liquid crystal display devices of Comparative Examples 3 and 4, where the initial inclination angle φ of the cut edge of the polarizing plate is extremely large, it is clear that display unevenness cannot be completely suppressed, both initially and after storage with moist heat. This is thought to be because the initial inclination angle φ of the cut edge is significantly large, exceeding 10°, which causes the display unevenness to persist, and because the force of contraction of the protective film becomes too large compared to the force of expansion of the polarizer when moisture is absorbed.

[0180] This application claims priority under Japanese Patent Application No. 2020-178173, filed on 23 October 2020. All provisions of the said application are incorporated herein by reference. [Industrial applicability]

[0181] According to the present invention, it is possible to provide a polarizing plate that can be cut with laser light without reducing productivity and can suppress display unevenness at the edges of a display device, as well as a method for manufacturing the same, and a method for manufacturing a display device. [Explanation of Symbols]

[0182] 10 Polarizing plates 10a Cut end surface 11 Polarizer 12. First protective film 13. Second protective film 14 Release film 20 Laminate 30 LCD display buttons 40. First polarizing plate 50. First polarizing plate 100 display device L laser light φ Tilt angle

Claims

1. A polarizing plate comprising a polarizer, a first protective film disposed on one side of the polarizer, a second protective film disposed on the other side of the polarizer, and a release film disposed on the side opposite to the polarizer, with the first protective film in between, is laminated. The absorption coefficient A2 of the second protective film for light with a wavelength of 9.4 μm, as measured by the ATR method, is 1.0 × 10⁻⁶. ２ ~4.5 x 10 ２ / μm and The ratio A1 / A2 of the absorption coefficient A1 of the first protective film for light at a wavelength of 9.4 μm, as measured by the ATR method, to the absorption coefficient A2 of the second protective film for light at a wavelength of 9.4 μm, as measured by the ATR method, is 2 to 4.

5. The polarizing plate has a cut end face, In the cross-section of the polarizing plate along the stacking direction, The angle of inclination of the straight line connecting the endpoint P1 of the release film on the side opposite to the first protective film at the cut end surface, and the endpoint P2 of the polarizer on the side of the second protective film, with respect to the lamination direction, is 0.5 to 10°. The second protective film is attached so that the display element side faces the second protective film. Polarizing plate.

2. The first protective film comprises a (meth)acrylic resin or a cycloolefin resin. The polarizing plate according to claim 1.

3. The second protective film contains a cycloolefin resin, A polarizing plate according to claim 1 or 2.

4. The second protective film further comprises one or more light-absorbing materials selected from the group consisting of ester compounds and (meth)acrylic polymer particles. The polarizing plate according to claim 3.

5. The mass-based content of the light-absorbing material in the second protective film is greater than the mass-based content of the light-absorbing material in the first protective film. The polarizing plate according to claim 4.

6. A laminate comprising a polarizer, a first protective film disposed on one side of the polarizer, a second protective film disposed on the other side of the polarizer, and a release film disposed on the side of the first protective film opposite to the polarizer, wherein the laminate is attached so that the side with the second protective film faces the display element side, and the ratio A1 / A2 of the absorption coefficient A1 of the first protective film for light at a wavelength of 9.4 μm measured by the ATR method to the absorption coefficient A2 of the second protective film for light at a wavelength of 9.4 μm measured by the ATR method is 2 to 4.5, A step of irradiating the laminate with laser light of wavelength 9.4 μm from the release film side to cut the laminate along the lamination direction of the laminate. Having, A method for manufacturing polarizing plates.

7. The process includes attaching a polarizing plate according to any one of claims 1 to 5 to at least one surface of a display element such that the second protective film faces the display element. A method for manufacturing a display device.

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