CN118732116A

CN118732116A - Polarizing plate

Info

Publication number: CN118732116A
Application number: CN202410349744.8A
Authority: CN
Inventors: 山口智之; 山形祐佳子; 大山裕也
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2023-03-30
Filing date: 2024-03-26
Publication date: 2024-10-01
Also published as: JP2024142939A

Abstract

The invention provides a polarizing plate for suppressing rainbow patterns observed from an oblique direction of the polarizing plate and suppressing leakage light under a high-temperature environment. A polarizing plate is provided, which comprises a polyester resin film, a 1 st adhesive layer, a polarizing plate, a 2 nd adhesive layer and a (meth) acrylic resin film in this order, wherein the phase difference Re defined by Re= (n _x-n_y) x d of the polyester resin film is 6000nm or more, the phase difference Re1 measured in the 1 st arrangement is 5000nm or more, the phase difference Re2 measured in the 2 nd arrangement is 6000nm or more, the phase difference Re3 measured in the 3 rd arrangement is 6000nm or more, and the phase difference Re4 measured in the 4 th arrangement is 7000nm or more.

Description

Polarizing plate

Technical Field

The present invention relates to a polarizing plate, and also relates to a polarizing plate with an adhesive layer and a liquid crystal display device including the same.

Background

In recent years, improvement in visibility of a liquid crystal display device has been demanded. In order to improve the visibility of a liquid crystal display device, it is also required to suppress unevenness and light leakage in a polarizing plate which is one of the members constituting the liquid crystal display.

In order to suppress unevenness of the polarizing plate and suppress light leakage, studies on the type and combination of the polarizer protective film in the polarizing plate have been made. For example, patent document 1 describes that when a biaxially stretched polyethylene terephthalate film of 38 μm is used as one polarizer protective film, the use of a film containing an acrylic compound whose composition is adjusted by a cellulose ester resin as the other polarizer protective film can suppress unevenness in the polarization degree of the polarizing plate.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-123402

Disclosure of Invention

Problems to be solved by the invention

In the polarizing plate described in patent document 1, suppression of rainbow marks (japanese: rainbow strands) observed from an oblique direction of the polarizing plate and suppression of light leakage of the polarizing plate in a high-temperature environment are also insufficient.

The invention aims to provide a polarizing plate which suppresses rainbow patterns observed from the inclined direction of the polarizing plate and suppresses leakage light under a high-temperature environment, a polarizing plate with an adhesive layer comprising the polarizing plate and a liquid crystal display device comprising the polarizing plate with the adhesive layer.

Means for solving the problems

The present invention includes the following inventions.

[1] A polarizing plate comprising, in order, a polyester resin film, a1 st adhesive layer, a polarizing plate, a2 nd adhesive layer and a (meth) acrylic resin film,

The polyester resin film satisfies the following [ i ] to [ iv ] with respect to the phase difference Re defined by the formula (1).

Re＝(n_x-n_y)×d (1)

In the formula, n _x represents the refractive index in the slow axis direction in the film plane, n _y represents the refractive index in the fast axis direction in the film plane, and d represents the film thickness. ]

[I] The phase difference Re1 measured in the 1 st arrangement is 6000nm or more, and in the 1 st arrangement, the polyester resin film is arranged such that the angle formed by the surface of the polyester resin film and the measuring direction is 90 degrees.

[ Ii ] in the 2 nd configuration of the measurement of the phase difference Re2 is more than 5000nm, in the 2 nd configuration, the above 1 st configuration of the polyester resin film around the fast axis as the center axis rotation 30 DEG, so that the polyester resin film surface and the measurement direction of the angle of 60 degrees.

In the 3 rd arrangement, the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction is 60 degrees by rotating the polyester resin film by 30 degrees about an axis forming an angle of 45 degrees with respect to the fast axis of the polyester resin film in the plane of the polyester resin film, and the measured phase difference Re3 is 6000nm or more.

[ Iv ] in the 4 th arrangement, the phase difference Re4 measured in the above 1 st arrangement is 7000nm or more, in the 4 th arrangement, by making the polyester resin film as a center axis rotation 30 DEG, so that the polyester resin film surface and the measurement direction form an angle of 60 degrees.

[2] The polarizing plate according to [1], wherein the surface reflectance of the polyester resin film is 5.7% or less.

[3] The polarizing plate according to [1] or [2], wherein the film thickness of the polyester resin film is 60 μm or more.

[4] The polarizing plate according to any one of [1] to [3], wherein a ratio of a phase difference value Re1 of the polyester resin film to a phase difference value Rth in a thickness direction defined by the formula (2) is 0.5 or more.

Rth＝〔(n_x+n_y)/2-n_z〕 ×d (2)

[ Wherein n _x represents the refractive index in the slow axis direction in the film plane, n _y represents the refractive index in the fast axis direction in the film plane, n _z represents the refractive index in the film thickness direction, and d represents the film thickness. ]

[5] The polarizing plate according to any one of [1] to [4], wherein the absolute value of the variation in the phase difference Rth in the thickness direction before and after the (meth) acrylic resin film is stored for 360 hours in an environment at a temperature of 85℃and a relative humidity of 85% RH is 10nm or less.

[6] The polarizing plate according to any one of [1] to [5], wherein the glass transition temperature of the (meth) acrylic resin film is 110℃or higher.

[7] The polarizing plate according to any one of [1] to [6], wherein the (meth) acrylic resin film comprises a (meth) acrylic resin component having a ring structure.

[8] A polarizing plate with an adhesive layer comprising the polarizing plate according to any one of [1] to [7] and an adhesive layer,

The pressure-sensitive adhesive layer is laminated on the surface of the (meth) acrylic resin film opposite to the polarizing plate.

[9] A liquid crystal display device comprising the polarizing plate with an adhesive layer according to [8 ].

Effects of the invention

According to the present invention, it is possible to provide a polarizing plate that suppresses rainbow unevenness from an oblique direction of the polarizing plate and suppresses leakage light in a high-temperature environment, a polarizing plate with an adhesive layer including the polarizing plate, and a liquid crystal display device including the polarizing plate with the adhesive layer.

Drawings

Fig. 1 is a schematic cross-sectional view schematically showing an example of a polarizing plate of the present invention.

Fig. 2 is a schematic perspective view illustrating the phase difference value Re1 and the measurement method thereof.

Fig. 3 is a schematic perspective view illustrating the phase difference value Re2 and the measurement method thereof.

Fig. 4 is a schematic perspective view illustrating the phase difference value Re3 and a measurement method thereof.

Fig. 5 is a schematic perspective view illustrating the phase difference value Re4 and the measurement method thereof.

Fig. 6 is a schematic cross-sectional view schematically showing an example of the adhesive layer-attached polarizing plate of the present invention.

Description of the reference numerals

1: Polarizing plate, 2: polarizing plate with adhesive layer, 10: polyester resin film, 15: adhesive layer 1, 20: (meth) acrylic resin film, 25: adhesive layer 2, 30: polarizing plate, 40: adhesive layer, 100: polyester resin film (1 st arrangement), 110: polyester resin film (arrangement 2), 120: polyester resin film (3 rd arrangement), 130: polyester resin film (4 th arrangement), 201: light source, 202: observer, 210: measurement directions, 300, 310, 320: center axis, 400: the fast axis of the polyester resin film in configuration 1, 500: the slow axis of the polyester resin film in the 1 st arrangement.

Detailed Description

The polarizing plate of the present invention comprises, in order, a polyester resin film, a1 st adhesive layer, a polarizing plate, a2 nd adhesive layer, and a (meth) acrylic resin film.

Fig. 1 shows an example of the layer structure of the polarizing plate of the present invention. The polarizing plate 1 shown in fig. 1 includes, in order, a polyester resin film 10, a1 st adhesive layer 15, a polarizing plate 30, a2 nd adhesive layer 25, and a (meth) acrylic resin film 20.

As shown in fig. 1, in the polarizing plate of the present invention, the polyester resin film 10 is preferably in direct contact with the 1 st adhesive layer 15. Further, the (meth) acrylic resin film 20 is preferably in direct contact with the 2 nd adhesive layer 25. Preferably, the polarizer 30 is in direct contact with the 1 st adhesive layer 15. Preferably, the polarizer 30 is in direct contact with the 2 nd adhesive layer 25.

< Polyester resin film >)

The polyester resin film used in the present invention satisfies the following [ i ] to [ iv ] with respect to the phase difference Re defined by the formula (1).

Re＝(n_x-n_y)×d (1)

In the formula, n _x denotes a refractive index in a slow axis direction in the film plane, n _y denotes a refractive index in a fast axis direction (a direction orthogonal to the slow axis direction in the film plane), and d denotes a thickness of the film. ]

[ Ii ] the phase difference Re2 measured in the 2 nd arrangement is 5000nm or more, and in the 2 nd arrangement, the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction becomes 60 DEG by rotating the polyester resin film by 30 DEG about the fast axis thereof as the central axis.

And (iii) the phase difference Re3 measured in the 3 rd arrangement is 6000nm or more, wherein the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction is 60 DEG by rotating the polyester resin film by 30 DEG about an axis forming an angle of 45 DEG with respect to the fast axis of the polyester resin film in the plane of the polyester resin film.

[ Iv ] the phase difference Re4 measured in the 4 th arrangement is 7000nm or more, and in the 4 th arrangement, the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction becomes 60 DEG by rotating the polyester resin film by 30 DEG about the slow axis thereof as the center axis.

The slow axis direction in the film plane means a direction in which the refractive index becomes maximum in the plane. In this specification, the phase difference value Re is a phase difference value at a wavelength of 587 nm.

Fig. 2 is a schematic perspective view illustrating the phase difference value Re1 and the measurement method thereof. The phase difference value Re1 is a phase difference value measured in the 1st arrangement, and in the 1st arrangement, the polyester resin film is arranged such that an angle formed between the surface of the polyester resin film 100 and the measurement direction 210 becomes 90 °. The measurement direction is a direction from the light source 201 of the phase difference measuring device toward the observer 202 for detecting and observing the light transmitted through the polyester resin film, and is a so-called optical path of the phase difference measuring device.

Fig. 3 is a schematic perspective view illustrating the phase difference value Re2 and the measurement method thereof. The phase difference value Re2 is a phase difference value measured for the polyester resin film 100 in the 1 st arrangement, that is, the polyester resin film 110 in the 2 nd arrangement, which is a polyester resin film inclined by rotating the polyester resin film 100 by 30 ° about the fast axis 400 thereof as the central axis 300. The angle between the surface of the polyester resin film 110 in the 2 nd arrangement and the measurement direction 210 is 60 °.

Fig. 4 is a schematic perspective view illustrating the phase difference value Re3 and a measurement method thereof. The phase difference value Re3 is a phase difference value measured for the polyester resin film in the 3 rd arrangement, that is, the polyester resin film 120 in the 1 st arrangement, by rotating the polyester resin film 100 by 30 ° about the axis 310 forming an angle of 45 ° with respect to the fast axis 400 thereof in the plane of the polyester resin film. The angle between the surface of the polyester resin film 120 in the 3 rd arrangement and the measurement direction 210 is 60 °.

Fig. 5 is a schematic perspective view illustrating the phase difference value Re4 and the measurement method thereof. The phase difference value Re4 is a phase difference value measured for the polyester resin film 100 in the 1 st arrangement, that is, the polyester resin film 130 in the 4 th arrangement, which is inclined by rotating the polyester resin film 100 by 30 ° about the slow axis 500 thereof as the central axis 320. The angle between the surface of the polyester resin film 130 in the 4 th arrangement and the measurement direction 210 is 60 °.

The phase difference Re1 of the polyester resin film is preferably 7000nm or more, more preferably 7500nm or more, and still more preferably 8000nm or more. The phase difference Re1 of the polyester resin film is usually 30000nm or less, preferably 20000nm or less, more preferably 15000nm or less, still more preferably 10000nm or less, and particularly preferably 9000nm or less. When the upper limit of the phase difference value Re1 exceeds 30000nm, the thickness of the polyester resin film tends to be considerably large in order to satisfy the phase difference value, and the handleability as an optical film tends to be greatly reduced. By setting the phase difference Re1 of the polyester resin film to 6000nm or more, rainbow lines (rainbow-like color spots) when viewed from an oblique direction are easily reduced.

The polyester resin film has a phase difference Re2 of 5000nm or more. The phase difference Re2 is preferably 5500nm or more, more preferably 6000nm or more, still more preferably 6500nm or more, particularly preferably 7000nm or more. The phase difference Re2 is usually 30000nm or less, preferably 20000nm or less, more preferably 15000nm or less, further preferably 10000nm or less, particularly preferably 9000nm or less. By setting the phase difference Re2 of the polyester resin film to 5000nm or more, rainbow lines when viewed from an oblique direction are easily reduced.

The phase difference Re3 of the polyester resin film is 6000nm or more. The phase difference Re3 is preferably 7000nm or more, more preferably 7500nm or more, and still more preferably 8000nm or more. The phase difference Re3 is usually 30000nm or less, preferably 20000nm or less, more preferably 15000nm or less, further preferably 10000nm or less, particularly preferably 9000nm or less. By setting the phase difference Re3 of the polyester resin film to 6000nm or more, rainbow lines when viewed from an oblique direction are easily reduced.

The phase difference Re4 of the polyester resin film is 7000nm or more. The phase difference Re4 is preferably 8000nm or more, more preferably 8500nm or more, and still more preferably 9000nm or more. The phase difference Re4 is usually 30000nm or less, preferably 20000nm or less, more preferably 15000nm or less, and still more preferably 10000nm or less. By setting the phase difference Re4 of the polyester resin film to 7000nm or more, rainbow lines when viewed from an oblique direction are easily reduced.

Re1 to Re4 can be measured by using a phase difference measuring apparatus (KOBRA-HB-RESPC, manufactured by Walker measuring instruments Co., ltd.).

By using a polyester resin film having Re1 to Re4 in the above range, rainbow patterns observed in the oblique direction of the polarizing plate can be suppressed.

The ratio (Re 1/Rth) of the phase difference Re1 to the phase difference Rth in the thickness direction of the polyester resin film is usually 0.4 or more, preferably 0.5 or more, more preferably 0.6 or more, still more preferably 0.7 or more, still more preferably 0.9 or more. If the ratio Re1/Rth is larger, there is a tendency that rainbow lines due to the observation angle are not easily generated. In the completely uniaxial (uniaxially symmetric) film, the ratio Re1/Rth is 2.0, and therefore, the ratio Re1/Rth is preferably 2.0 or less, and more preferably 1.5 or less.

The phase difference value Rth in the thickness direction is represented by the following formula (2). The thickness-direction phase difference value Rth is the thickness-direction phase difference value at the wavelength of 587 nm.

Rth＝〔(n_x+n_y)/2-n_z〕×d (2)

[ Wherein n _x represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, n _z represents the refractive index in the film thickness direction (direction perpendicular to the film plane), and d represents the film thickness. ]

The angle between the fast axis or slow axis of the polyester resin film and the transmission axis of the polarizing plate is, for example, from-20 ° to +20°, preferably from-15 ° to +15°, more preferably from-10 ° to +10°, still more preferably from-5 ° to +5°, still more preferably from-3 ° to +3°, still more preferably from-2 ° to +2°, and particularly preferably from-1 ° to +1°. In a preferred embodiment, the fast axis or slow axis of the polyester resin film is substantially parallel to the transmission axis of the polarizing plate. Here, substantially parallel means that the transmission axis of the polarizer is parallel to the fast axis or slow axis of the polyester resin film to such an extent that the shift that is inevitably generated when the polarizer is bonded to the polyester resin film is allowed.

The smaller the angle between the fast axis or slow axis of the polyester resin film and the transmission axis of the polarizing plate, the smaller the change in polarization state due to the transmission of the linearly polarized light through the polyester resin film, and thus the tendency is that occurrence of rainbow lines can be suppressed.

In order to suppress degradation of an optically functional dye such as iodine contained in the polarizing plate, the transmittance of the polyester resin film at 380nm is preferably 40% or less. The light transmittance at 380nm is more preferably 35% or less, still more preferably 30% or less, particularly preferably 20% or less. If the light transmittance is 40% or less, deterioration of the optically functional dye due to ultraviolet rays can be suppressed.

At least one selected from the group consisting of an antireflection layer and a low-reflection prevention layer may be provided on at least one surface of the polyester resin film.

The surface reflectance of the antireflection layer is preferably 5.7% or less. If the surface reflectance of the anti-reflection layer exceeds 5.7%, there is a tendency that rainbow marks are easily observed. The surface reflectance of the antireflection layer is more preferably 5.3% or less, still more preferably 5.0% or less, and particularly preferably 4.5% or less. The lower limit of the surface reflectance of the antireflection layer is not particularly limited, and is, for example, 2.0%. The reflectance may be measured by any method. For example, a polyester resin film having a surface opposite to the antireflection layer side of the polyester resin film bonded to a black acrylic plate with an adhesive therebetween may be measured for light reflectance at 550nm from the antireflection layer side surface using a spectrocolorimeter (CM-2600 d, manufactured by KONICA MINOLTA JAPAN).

The anti-reflection layer may be a single layer or a plurality of layers. Examples of the antireflection layer include a hard coat layer having a fine uneven shape on the surface and antiglare properties for preventing reflection glare of external light. Examples of the antiglare hard coat layer include an antiglare hard coat layer in which a filler is dispersed in the hard coat layer to form a surface roughness, an antiglare hard coat layer in which a surface roughness is formed in the hard coat layer by an embossing method or the like, and the like. For example, in the case of forming an antiglare hard coat layer using an ultraviolet curable resin, the ultraviolet curable resin may be applied to a polyester resin film and irradiated with ultraviolet rays, or the ultraviolet curable resin may be applied to a polyester resin film and irradiated with ultraviolet rays in a state where the coating film is adhered to the uneven surface of a mold.

As a material for forming the antiglare hard coat layer, an ultraviolet curable resin, a thermosetting resin, an electron beam curable resin, or the like can be used, and from the viewpoints of productivity, hardness, and the like, the ultraviolet curable resin is preferably used.

The surface reflectance of the low-reflection preventing layer is preferably 4.0% or less. The surface reflectance of the low-reflection preventing layer is more preferably 3.0% or less, still more preferably 2.0% or less, still more preferably 1.5% or less, and particularly preferably 1.0% or less. The lower limit of the surface reflectance of the low-reflection preventing layer is not particularly limited, and may be, for example, 0.01%.

The low reflection preventing layer may be a single layer or a plurality of layers. In the case where the low-reflection preventing layer is a single layer, an antireflection effect can be obtained if the thickness of the low-refractive-index layer made of a material having a refractive index lower than that of the polyester resin film is formed to be 1/4 wavelength or an odd multiple of the wavelength of light. In addition, when the antireflection layer is a multilayer, an antireflection effect can be obtained if the low refractive index layer and the high refractive index layer are alternately formed to be 2 or more layers, and the thickness of each layer is appropriately controlled to be laminated. In addition, a hard coat layer may be laminated between the low reflection preventing layer and the polyester resin film, if necessary.

The low reflection preventing layer may be a known low reflection preventing layer. The low-reflection preventing layer is preferably a layer formed by coating an organic thin film having a lower refractive index than a polyester resin film, a hard coat layer laminated on the polyester resin film, or the like.

The thickness of at least one selected from the antireflection layer and the low reflection preventing layer is usually 0.01 to 20 μm, preferably 0.03 to 1 μm, more preferably 0.05 to 0.15 μm.

The surface reflectance of the polyester resin film is preferably 5.7% or less, more preferably 5.3% or less, further preferably 4.0% or less, further preferably 3.0% or less, particularly preferably 2.0% or less, and most preferably 1.5% or less. The surface reflectance of the polyester resin film is usually 0.01% or more.

If the surface reflectance of the polyester resin film is 5.7% or less, the rainbow pattern of the polarizing plate to which the polyester resin film is applied tends to be more effectively suppressed.

In the case where at least one selected from the antireflection layer and the low reflection layer is laminated as described above, the total surface reflectance of the at least one selected from the antireflection layer and the low reflection layer is 5.7% or less. It is presumed that by reducing the surface reflectance, the interface reflectance between the base film and air can be reduced, and rainbow marks can be suppressed.

When at least one selected from the antireflection layer and the low-reflection preventing layer is provided on only one side of the polyester resin film, at least one selected from the antireflection layer and the low-reflection preventing layer is preferably provided on the opposite side of the polyester resin film from the polarizing plate.

In the case of providing at least one selected from the antireflection layer and the low-reflection preventing layer, the polyester resin film preferably has an easy-to-adhere layer on the surface thereof. In this case, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-to-adhere layer to the vicinity of the geometric average of the refractive index of the antireflection layer or the low-reflection preventing layer and the refractive index of the polyester resin film. The refractive index of the easy-to-bond layer can be adjusted by a known method.

In order to improve the adhesion to the polarizing plate, the polyester resin film preferably has an easy-to-adhere layer containing at least 1 of a polyester resin, a polyurethane resin, or a polyacrylic resin as a main component on at least one surface thereof. The "main component" herein means 50% by mass or more of the solid components constituting the easy-to-adhere layer. The coating liquid used for forming the easy-to-adhere layer is preferably an aqueous coating liquid containing at least 1 of a water-soluble or water-dispersible copolyester resin, an acrylic resin, and a polyurethane resin. Examples of the coating liquid include a water-soluble or water-dispersible copolyester resin solution, an acrylic resin solution, a urethane resin solution, and the like disclosed in japanese patent No. 3567927, japanese patent No. 3589232, japanese patent No. 3589233, japanese patent No. 3900191, japanese patent No. 4150982, and the like.

When a polyester resin is used as the adhesive layer, a water-soluble or water-dispersible resin is preferably used from the viewpoint of compatibility with a polyvinyl alcohol resin. For the water-solubility or water-dispersibility of the polyester resin, it is preferable to copolymerize a compound containing a hydrophilic group such as a sulfonate group or a carboxylate group. Among them, a dicarboxylic acid component having a sulfonate group is preferable from the viewpoints of keeping the acid value of the polyester resin low, controlling the reactivity with the crosslinking agent, and imparting hydrophilicity. Examples of the dicarboxylic acid component having a sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthalene isophthalic acid-2, 7-dicarboxylic acid and 5- (4-sulfophenoxy) isophthalic acid or alkali metal salts thereof, and among these, 5-sulfoisophthalic acid is preferable. The dicarboxylic acid component having a sulfonate group is preferably 1 to 15 mol%, more preferably 1.5 to 12 mol%, and even more preferably 2 to 10 mol% of the dicarboxylic acid component of the polyester resin. When the dicarboxylic acid component having a sulfonate group is not less than the lower limit, the polyester resin is suitably water-soluble or water-dispersible. In addition, when the dicarboxylic acid component having a sulfonate group is not more than the upper limit, the adhesive property with the polyester film base material is suitable.

The adhesive layer can be obtained by applying the coating liquid to one or both surfaces of a polyester resin film, drying at 100 to 150 ℃ and stretching in the transverse direction. The coating amount of the final easy-to-adhere layer is preferably 0.05 to 0.20g/m ². If the coating amount is less than 0.05g/m ², the adhesiveness to the polarizing plate may become insufficient. On the other hand, if the coating amount exceeds 0.20g/m ², the blocking resistance may be lowered. When the polyester resin film is provided with the adhesive layer on both sides, the coating amounts of the adhesive layers on both sides may be the same or different, and may be set independently from each other within the above-mentioned range.

In order to impart slipperiness, it is preferable to add particles to the easy-to-adhere layer. The average particle diameter of the particles is preferably 2 μm or less. If the average particle diameter of the particles exceeds 2. Mu.m, the particles are liable to fall off from the adhesive layer. Examples of the particles contained in the easy-to-adhere layer include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. These may be added to the easy-to-adhere layer alone or in combination of 2 or more.

As a method of applying the coating liquid, a known method can be used. Examples thereof include a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brush method, a spray coating method, an air knife coating method, a wire bar coating method, a tube blade coating method, and the like, which may be performed alone or in combination.

The thickness of the polyester resin film is arbitrary, and is usually 15 μm to 200. Mu.m, preferably 20 μm to 100. Mu.m, more preferably 25 μm to 95. Mu.m, still more preferably 60 μm to 90. Mu.m.

If the thickness of the polyester resin film is less than 15 μm, the anisotropy of mechanical properties of the film becomes remarkable, and cracks, etc. are liable to occur, which tends to lower the practical applicability. On the other hand, if the thickness of the polyester resin film exceeds 200. Mu.m, the thickness as a polarizing plate becomes too thick.

In the case where at least one selected from the antireflection layer and the low-reflection preventing layer is provided as described above, the total thickness including the above may be within the above range.

The polyester resin film used in the present invention can be produced by a usual method for producing a polyester film, and can be obtained by a method described in, for example, japanese patent application laid-open publication No. 2021-103319 or japanese patent application laid-open publication No. 2021-99521.

The phase difference values of Re1 to Re4 can be controlled to specific ranges by appropriately setting the draw ratio, draw temperature, and film thickness. For example, a high phase difference value is easily obtained by increasing the stretching ratio, decreasing the stretching temperature, increasing the thickness of the film, and the like. The phase difference values of Re1 to Re4 can be set by selecting the film formation conditions and thickness from the above conditions in consideration of the physical properties and the like required for processing.

The material for forming the polyester resin film is not particularly limited, and polyethylene terephthalate, polyethylene naphthalate, and other copolymer components may be used. From the viewpoint of controlling the phase difference value of the polyester resin film, the material forming the polyester resin film is preferably polyethylene terephthalate resin.

(Meth) acrylic resin film

The (meth) acrylic resin film is excellent in mechanical properties, solvent resistance, scratch resistance, light resistance, transparency, cost, and the like. By using a (meth) acrylic resin film as a polarizer protective film, improvement in mechanical strength and thinning of a polarizing plate, a liquid crystal panel including the same, and a liquid crystal display device can be achieved. In addition, by using the above polyester resin film as one polarizer protective film and using the (meth) acrylic resin film as the other polarizer protective film, rainbow lines when viewed from an oblique direction can be effectively suppressed. In addition, by using the above polyester resin film as one polarizer protective film and using the (meth) acrylic resin film as the other polarizer protective film, light leakage in a high-temperature environment can be effectively suppressed.

The (meth) acrylic resin constituting the (meth) acrylic resin film is a material obtained by mixing the (meth) acrylic resin with additives and the like added as needed, and melt-kneading the mixture.

In the present specification, "(meth) acrylic resin" means "(meth)" which may be any of acrylic resin and methacrylic resin, and is also defined as (meth) acrylate, (meth) acryl, etc.

The (meth) acrylic resin is preferably a polymer mainly composed of (meth) acrylic acid ester. The (meth) acrylic resin may be a homopolymer of 1 (meth) acrylate or a copolymer of (meth) acrylate and other (meth) acrylate. Examples of the (meth) acrylic acid ester include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate, and the number of carbon atoms of the alkyl group is usually about 1 to 8. Examples of the polymerizable monomer copolymerizable with the (meth) acrylic acid ester include styrene monomers such as styrene and alkylstyrene; monofunctional monomers such as unsaturated nitriles, e.g., acrylonitrile and methacrylonitrile, and alkenyl esters of unsaturated carboxylic acids, e.g., allyl (meth) acrylate and methallyl (meth) acrylate; diallyl maleate and other dibasic acid dienyl esters; polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

The (meth) acrylic resin film may contain 2 or more (meth) acrylic resins.

When the (meth) acrylic resin film contains 2 or more types of (meth) acrylic resins, it is preferable that the syndiotacticity (rr) represented by the triad of at least 1 type of (meth) acrylic resins is 50% or more. The syndiotacticity (rr) represented by the triad is preferably 55% or more, more preferably 60% or more, still more preferably 65% or more, still more preferably 70% or more, from the viewpoint of improving the toughness of the film, improving the heat resistance of the film and the adhesion to the polarizing plate. The syndiotacticity (rr) represented by the triad is usually 90% or less, or may be 85% or less.

The syndiotacticity (rr) represented by the triad is the ratio of 2 chains (diads, diad) that the continuous chains of 3 structural units (triads, triad) have to be racemic (expressed as rr). The syndiotacticity (rr) (%) expressed by the triad was calculated as follows: ¹ H-NMR spectrum was measured at 30℃in CDCL ₃, and based on the spectrum, the area (X) of the region of 0.6 to 0.95ppm and the area (Y) of the region of 0.6 to 1.35ppm were measured, and calculated as (X/Y). Times.100.

The (meth) acrylic resin having a syndiotacticity (rr) of 50% or more, which is represented by the triad, can be produced, for example, by the method described in International publication No. 2016/080124.

When the (meth) acrylic resin having a syndiotacticity (rr) of 50% or more is contained in the three-unit group, the content of the (meth) acrylic resin having a syndiotacticity (rr) of 50% or more is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, still more preferably 10% by mass or more and 35% by mass or less, still more preferably 15% by mass or more and 30% by mass or less, relative to the entire (meth) acrylic resin, from the viewpoints of the toughness of the film and the adhesion to the polarizing plate.

As the (meth) acrylic resin, a (meth) acrylic resin having a ring structure can be used. Examples of the (meth) acrylic resin having a ring structure include (meth) acrylic resins having a lactone ring structure, and (meth) acrylic resins having a glutaric anhydride structure, a glutarimide structure, and the like. The (meth) acrylic resin having a ring structure has high heat resistance, high wet heat resistance, high transparency, and high mechanical strength by biaxial stretching.

Examples of the (meth) acrylic resin having a ring structure such as a lactone ring structure include resins described in JP-A2000-230016, JP-A2001-151814, JP-A2002-120326, JP-A2002-254544, and JP-A2005-146084.

Examples of the (meth) acrylic resin having a glutaric anhydride structure, a glutarimide structure, or the like include resins described in JP-A-6-256537, JP-A-6-11615, and JP-A-2009-203348.

The (meth) acrylic resin having a lactone ring structure preferably has a ring structure represented by the following general formula < 1 >.

[ Chemical formula 1]

( Wherein R ¹、R² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. )

The content of the lactone ring structure represented by the general formula < 1 > in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, still more preferably 10 to 60% by mass, and particularly preferably 10 to 50% by mass. If the content of the lactone ring structure represented by the general formula < 1 > in the structure of the (meth) acrylic resin having the lactone ring structure is less than 5% by mass, heat resistance, solvent resistance, and surface hardness may be insufficient. If the content of the lactone ring structure represented by the general formula < 1 > in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90 mass%, there is a possibility that the molding processability is poor. The ratio of the lactone ring structure in the (meth) acrylic resin having the lactone ring structure can be determined by gas chromatography or dynamic TG measurement, for example, as described in japanese patent application laid-open No. 2006-171464.

The (meth) acrylic resin having a lactone ring structure may have a structure other than the lactone ring structure represented by the general formula < 1 >. The structure other than the lactone ring structure represented by the general formula < 1 > is not particularly limited, and a polymer structural unit (repeating structural unit) formed by polymerizing at least 1 selected from the group consisting of (meth) acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following general formula < 2 > is preferable as a method for producing a (meth) acrylic resin having a lactone ring structure.

[ Chemical formula 2]

Wherein R ⁴ represents a hydrogen atom or a methyl group, X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, -OAc group, -CN group or-CO-R ⁵ group, ac group represents an acetyl group, and R ⁵ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

The content of the structure other than the lactone ring structure represented by the general formula < 1 > in the (meth) acrylic resin structure having a lactone ring structure is preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, particularly preferably 50 to 90% by mass, in the case of a polymer structural unit (repeating structural unit) formed by polymerizing a hydroxyl group-containing monomer, preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass, in the case of a polymer structural unit (repeating structural unit) formed by polymerizing a (meth) acrylic acid ester. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing an unsaturated carboxylic acid, the content is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing a monomer represented by the general formula < 2 >, the content is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass.

The weight average molecular weight of the (meth) acrylic resin having a lactone ring structure is preferably 1000 to 2000000, more preferably 5000 to 1000000, further preferably 10000 to 500000, particularly preferably 50000 to 500000. If the weight average molecular weight is out of the above range, it is not preferable from the viewpoint of molding processability.

Examples of the thermoplastic resin to be mixed with the (meth) acrylic resin having a lactone ring structure include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and vinyl chloride resins; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, nylon 610, etc.; polyacetal; a polycarbonate; polyphenylene ether; polyphenylene sulfide; polyether ether ketone; polysulfone; polyether sulfone; polyoxy benzyl ester (polyethylene, japanese) on the top; polyamide imide; rubber polymers such as ABS resins and ASA resins blended with polybutadiene rubber and acrylic rubber.

The (meth) acrylic resin having a glutaric anhydride structure, a glutarimide structure or the like preferably has a ring structure represented by the above general formula < 2 > and the following general formula < 3 >.

[ Chemical formula 3]

(Wherein R ¹ and R ² are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ is hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a substituent having 5 to 15 carbon atoms and containing an aromatic ring).

The content of the glutarimide structure is preferably 20% by mass or more, more preferably 20% by mass to 95% by mass, still more preferably 40% by mass to 90% by mass, and particularly preferably 50% by mass to 80% by mass of the (meth) acrylic resin having the glutarimide structure.

If the content of the glutarimide unit is within the above range, the resulting (meth) acrylic resin having glutarimide will not be extremely reduced in heat resistance and transparency or in molding processability and mechanical strength at the time of film formation.

On the other hand, if the content of the glutarimide unit is less than the above range, the obtained glutarimide resin tends to be insufficient in heat resistance or impaired in transparency. If the amount is larger than the above range, heat resistance and melt viscosity are unnecessarily high, molding processability is deteriorated, mechanical strength during film processing is extremely low, and transparency is likely to be impaired.

The weight average molecular weight of the (meth) acrylic resin having a glutarimide structure is not particularly limited, and is preferably 10000 to 500000. If the amount is within the above range, the molding processability is not lowered, or the mechanical strength at the time of film processing is not sufficient. On the other hand, if the weight average molecular weight is less than the above range, there is a tendency that the mechanical strength is insufficient at the time of film formation. If the amount is larger than the above range, the viscosity at the time of melt extrusion tends to be high, the molding processability tends to be low, and the productivity of molded articles tends to be low.

Further, as the (meth) acrylic resin, a mixture or copolymer of a (meth) acrylic acid ester and an imide compound as a thermoplastic resin can be mentioned. Examples of the imide compound include N-substituted maleimides such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-N-propylmaleimide, N-isopropylmaleimide, N-N-butylmaleimide, N-isobutylmaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-N-pentylmaleimide, N-N-hexylmaleimide, N-N-heptylmaleimide, N-N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide, N-cyclopropyl maleimide, N-cyclobutylmaleimide, N-cyclopentyl maleimide, N-cyclohexylmaleimide, N-cycloheptylmaleimide, N-cyclooctylmaleimide and the like. These maleimide compounds may be used alone or in combination of 2 or more.

The (meth) acrylic resin preferably contains acrylic rubber particles in view of impact resistance and film formability of the film. The amount of the acrylic rubber particles that can be contained in the (meth) acrylic resin is preferably 5 mass% or more, more preferably 10 mass% or more, relative to 100 mass% of the total amount of the (meth) acrylic resin and the acrylic rubber particles. The upper limit of the amount of the acrylic rubber particles is not critical, but if the amount of the acrylic rubber particles is too large, the surface hardness of the film decreases, and in the case of subjecting the film to surface treatment, the solvent resistance of the organic solvent in the surface treatment agent decreases. Therefore, the amount of the acrylic rubber particles that can be contained in the (meth) acrylic resin is preferably 80 mass% or less, more preferably 60 mass% or less.

The acrylic rubber particles are particles containing an elastic polymer mainly composed of an acrylic ester as an essential component, and may have a single-layer structure substantially composed of only the elastic polymer, or may have a multilayer structure in which the elastic polymer is 1 layer. Specifically, a crosslinked elastic copolymer obtained by polymerizing a monomer composed of 50 to 99.9 mass% of an alkyl acrylate, 0 to 49.9 mass% of at least 1 other vinyl monomer copolymerizable therewith, and 0.1 to 10 mass% of a copolymerizable crosslinking monomer is preferably used as the elastic polymer.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and the number of carbon atoms of the alkyl group is usually about 1 to 8. Further, examples of the other vinyl monomer copolymerizable with the alkyl acrylate include compounds having 1 polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylates such as methyl methacrylate, aromatic vinyl compounds such as styrene, vinyl cyanide compounds such as acrylonitrile, and the like. Further, examples of the copolymerizable crosslinking monomer include crosslinkable compounds having at least 2 polymerizable carbon-carbon double bonds in the molecule, and more specifically, examples thereof include (meth) acrylic esters of polyhydric alcohols such as ethylene glycol di (meth) acrylate and butanediol di (meth) acrylate, allyl (meth) acrylate, alkenyl esters of (meth) acrylic acid such as methallyl (meth) acrylate, divinylbenzene, and the like.

The (meth) acrylic resin may contain, in addition to the acrylic rubber particles, a usual additive such as an ultraviolet absorber, an organic dye, a pigment, an inorganic pigment, an antioxidant, an antistatic agent, a surfactant, and the like. Among them, ultraviolet absorbers are preferably used in terms of improving weather resistance. Examples of the ultraviolet light absorber include benzotriazole-based ultraviolet light absorbers such as 2,2' -methylenebis [ 4- (1, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol ], 2- (5-methyl-2-hydroxyphenyl) -2H-benzotriazole, 2- [ 2-hydroxy-3, 5-bis (. Alpha.,. Alpha. -dimethylbenzyl) phenyl ] -2H-benzotriazole, 2- (3, 5-di-tert-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3, 5-di-tert-butyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3, 5-di-tert-amyl-2-hydroxyphenyl) -2H-benzotriazole, and 2- (2 ' -hydroxy-5 ' -tert-octylphenyl) -2H-benzotriazole; 2-hydroxybenzophenone-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2, 4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4 '-chlorobenzophenone, 2' -dihydroxy-4-methoxybenzophenone, and 2,2 '-dihydroxy-4, 4' -dimethoxybenzophenone; phenyl salicylate-based ultraviolet absorbers such as p-tert-butylphenyl salicylate and p-octylphenyl salicylate may be used in an amount of 2 or more of them as required. When the ultraviolet absorber is contained in the (meth) acrylic resin, the amount thereof is usually 0.1 mass% or more, preferably 0.3 mass% or more, and preferably 2 mass% or less, relative to 100 mass% of the total amount of the (meth) acrylic resin and the ultraviolet absorber.

As a method for obtaining the (meth) acrylic resin film, various conventionally known methods such as a method using a flow divider, a method using a multi-manifold die, and the like can be used. Among them, a method of laminating the films via a shunt, performing multilayer melt extrusion molding from a T-die, and forming a film by bringing at least one surface of the obtained laminated film into contact with a roll or a belt is preferable in view of obtaining a film having good surface properties. In particular, from the viewpoint of improving the surface smoothness and surface gloss of the (meth) acrylic resin film, a method of bringing both surfaces of the multilayer melt extrusion molded laminate film into contact with a roll surface or a belt surface to form a film is preferable. In the roll or belt used in this case, the surface of the roll or belt in contact with the (meth) acrylic resin is preferably a mirror surface in order to impart smoothness to the surface of the (meth) acrylic resin film. In order to improve the film strength, the resulting film may be stretched.

A film formed of a (meth) acrylic resin is unlikely to cause a retardation in an unstretched state, but if stretched, a retardation occurs, and therefore a substance functioning as a retardation reducing agent can be blended into a (meth) acrylic resin, so that no retardation occurs even if stretched. Examples of the retardation reducing agent include styrene-acrylonitrile copolymer. The retardation value can be controlled by the stretching ratio and the blending amount of the retardation reducing agent.

The thickness of the (meth) acrylic resin film is usually 1 μm or more and 80 μm or less, preferably 3 μm or more and 65 μm or less, more preferably 5 μm or more and 55 μm or less, still more preferably 7 μm or more and 45 μm or less, and particularly preferably 20 μm or more and 45 μm or less.

The glass transition temperature of the (meth) acrylic resin film is 100℃or higher, preferably 110℃or higher, more preferably 115℃or higher, and still more preferably 120℃or higher. The glass transition temperature is usually 170℃or lower. When the glass transition temperature of the (meth) acrylic resin film is 110 ℃ or higher, there is a tendency that the change in the molecular orientation of the (meth) acrylic resin in the (meth) acrylic resin film in a high-temperature environment, etc. are suppressed, the change in the phase difference value Re and the phase difference value Rth in the thickness direction are suppressed, and light leakage in a high-temperature environment is more effectively suppressed. The phase difference Re and the thickness-direction phase difference Rth of the (meth) acrylic resin film were phase differences at a wavelength of 587 nm.

If the absolute value of the phase difference value Rth in the thickness direction of the (meth) acrylic resin film is 15nm or less, the (meth) acrylic resin film can serve as both an optical compensation film and a polarizer protective film in an IPS liquid crystal display device.

The absolute value of the phase difference value Rth in the thickness direction of the (meth) acrylic resin film is preferably 11nm or less, more preferably 8nm or less, and still more preferably 5nm or less.

The absolute value of the phase difference value Rth in the thickness direction of the (meth) acrylic resin film after the test in which the film is stored for 360 hours at a temperature of 85 ℃ and a relative humidity of 85% rh is preferably 15nm or less. The phase difference Rth in the thickness direction is defined by the above formula (2).

The absolute value of the phase difference Rth in the thickness direction of the (meth) acrylic resin film is more preferably 11nm or less, still more preferably 8nm or less, particularly preferably 5nm or less.

The absolute value of the variation in the phase difference value Rth in the thickness direction before and after the test of the (meth) acrylic resin film stored in an environment at a temperature of 85 ℃ and a relative humidity of 85% rh for 360 hours is preferably 10nm or less. The phase difference Rth in the thickness direction is defined by the above formula (2).

The absolute value of the variation in the phase difference Rth in the thickness direction of the (meth) acrylic resin film is more preferably 7nm or less, still more preferably 5nm or less, and particularly preferably 3nm or less.

If the absolute value of the variation in the phase difference Rth in the thickness direction of the (meth) acrylic resin film is 10nm or less, the variation in the phase difference in the high-temperature environment is small, and thus there is a tendency that light leakage in the high-temperature environment is more easily suppressed. It is presumed that such a (meth) acrylic resin film is suppressed in changes in molecular orientation, molecular structure, and the like in the (meth) acrylic resin film due to moisture in the polarizing plate laminate under a high-temperature environment.

< Polarizer >

The polarizing plate is a film having a function of selectively transmitting linearly polarized light in a certain direction from natural light. Examples of the polarizing plate include an iodine-based polarizing plate in which iodine as a dichroic dye is adsorbed and aligned to a polyvinyl alcohol-based resin film, a dye-based polarizing plate in which a dichroic dye as a dichroic dye is adsorbed and aligned to a polyvinyl alcohol-based resin film, and a coated polarizing plate in which a dichroic dye in a lyotropic liquid crystal state is coated, aligned, and immobilized. These polarizing plates selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in the other direction, and are therefore called absorption type polarizing plates.

The polarizing plate is not limited to an absorption type polarizing plate, and may be a reflection type polarizing plate that selectively transmits linear polarized light in one direction from natural light and reflects linear polarized light in the other direction, or a scattering type polarizing plate that scatters linear polarized light in the other direction, and the absorption type polarizing plate is preferable in view of excellent visibility when the polarizing plate is applied to a liquid crystal display device or the like.

Among these, the polarizing plate is more preferably a polyvinyl alcohol polarizing plate composed of a polyvinyl alcohol resin, further preferably a polyvinyl alcohol polarizing plate in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented to a polyvinyl alcohol resin film, and particularly preferably a polyvinyl alcohol polarizing plate in which iodine is adsorbed and oriented to a polyvinyl alcohol resin film.

The polyvinyl alcohol-based polarizing plate can be produced by a conventionally known method using a polyvinyl alcohol-based resin film (or layer).

The thickness of the polarizing plate may be 30 μm or less, preferably 25 μm or less (for example, 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, still more preferably 8 μm or less). The thickness of the polarizing plate 30 is usually 2 μm or more. The reduction in thickness of the polarizing plate is advantageous for thinning the polarizing plate, and further, a liquid crystal panel, a liquid crystal display device, and the like to which the polarizing plate is applied.

The visibility-corrected polarization degree of the polarizing plate may be, for example, 99.00% or more, preferably 99.90% or more, more preferably 99.98% or more, still more preferably 99.99% or more, and usually 100% or less, for example, may be less than 100%.

The visibility correction transmittance of the polarizing plate may be, for example, 40% or more, preferably 41% or more, more preferably 42% or more, still more preferably 43% or more, and usually 50.0% or less, for example, may be less than 50.0% or 49.0% or less.

The visibility-corrected polarization degree and the visibility-corrected transmittance of the polarizing plate can be calculated by correcting the visibility of the polarization degree and the transmittance obtained by using a spectrophotometer with an integrating sphere (for example, "V7100" manufactured by japan spectroscopy corporation) using a 2-degree field of view (C light source) of "JIS Z8701".

< Adhesive layer >)

The 1 st adhesive layer for bonding the polarizer to the polyester resin film and the 2 nd adhesive layer for bonding the polarizer to the (meth) acrylic resin film may be formed of a known adhesive composition. The 1 st adhesive layer and the 2 nd adhesive layer may be adhesive layers formed of the same adhesive composition or may be adhesive layers formed of different adhesive compositions. The 1 st adhesive layer and the 2 nd adhesive layer may be each an adhesive layer formed of an aqueous adhesive composition, or may be each an adhesive layer formed of a curable adhesive composition cured by heating or irradiation of active energy rays such as ultraviolet rays, visible light, electron beams, X-rays, or the like.

Examples of the aqueous adhesive composition include a composition obtained by dissolving a polyvinyl alcohol resin or a urethane resin as a main component in water and a composition obtained by dispersing a polyvinyl alcohol resin or a urethane resin as a main component in water. The aqueous adhesive composition may further contain a curable component such as a polyaldehyde, a melamine compound, a zirconia compound, a zinc compound, a glyoxal compound, a water-soluble epoxy resin, and a crosslinking agent. Examples of the aqueous adhesive composition include an adhesive composition described in japanese patent application laid-open publication No. 2010-191389, an adhesive composition described in japanese patent application laid-open publication No. 2011-107686, a composition described in japanese patent application laid-open publication No. 2020-172088, and a composition described in japanese patent application laid-open publication No. 2005-208456.

The curable adhesive composition is preferably an active energy ray curable adhesive composition which contains a curable (polymerizable) compound as a main component and is cured by irradiation with active energy rays. Examples of the active energy ray-curable adhesive composition include a cationic polymerizable adhesive composition containing a cationic polymerizable compound as a curable compound, a radical polymerizable adhesive composition containing a radical polymerizable compound as a curable compound, and a mixed adhesive composition containing both a cationic polymerizable compound and a radical polymerizable compound as a curable compound.

The cationically polymerizable compound is a compound or oligomer which is cured by a cationic polymerization reaction by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, X-rays, and the like, and specifically, an epoxy compound, an oxetane compound, a vinyl compound, and the like are exemplified.

Examples of the epoxy compound include alicyclic epoxy compounds (compounds having 1 or more epoxy groups bonded to an alicyclic ring in the molecule) such as 3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexane carboxylate; aromatic epoxy compounds (compounds having an aromatic ring and an epoxy group in the molecule) such as diglycidyl ether of bisphenol a; aliphatic epoxy compounds such as 2-ethylhexyl glycidyl ether and 1, 4-butanediol diglycidyl ether (compounds having at least 1 oxirane ring bonded to an aliphatic carbon atom in the molecule), and the like.

Examples of oxetane compounds include compounds having 1 or more oxetane rings in the molecule, such as 3-ethyl-3- { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane.

The cationically polymerizable adhesive composition preferably contains a cationic polymerization initiator. The cationic polymerization initiator may be a thermal cationic polymerization initiator or a photo cationic polymerization initiator. Examples of the cationic polymerization initiator include aromatic diazonium salts such as benzodiazonium hexafluoroantimonate; aromatic iodonium salts such as diphenyliodonium tetrakis (pentafluorophenyl) borate; aromatic sulfonium salts such as triphenylsulfonium hexafluorophosphate; iron-arene complexes such as xylene-cyclopentadienyl iron (II) hexafluoroantimonate. The content of the cationic polymerization initiator is usually 0.1 to 10 parts by mass relative to 100 parts by mass of the cationically polymerizable compound. The cationic polymerization initiator may contain 2 or more.

Examples of the cationically polymerizable adhesive composition include the cationically polymerizable compositions described in JP-A2016-126345 and JP-A2021-113969.

The radical polymerizable compound is a compound or oligomer which is cured by radical polymerization reaction by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, X-rays, and the like, and specifically, a compound having an ethylenically unsaturated bond is exemplified. Examples of the compound having an ethylenically unsaturated bond include a (meth) acrylic compound having 1 or more (meth) acryloyl groups in the molecule, and a vinyl compound having 1 or more vinyl groups in the molecule.

Examples of the (meth) acrylic compound include (meth) acryl-containing compounds such as (meth) acrylic oligomers having at least 2 (meth) acryl groups in the molecule, which are obtained by reacting 2 or more kinds of (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule, a (meth) acrylamide monomer, and a functional group-containing compound.

The radical polymerization type adhesive composition preferably contains a radical polymerization initiator. The radical polymerization initiator may be a thermal radical polymerization initiator or a photo radical polymerization initiator. Examples of the radical polymerization initiator include acetophenone-based initiators such as acetophenone and 3-methylacetophenone; benzophenone-based initiators such as benzophenone, 4-chlorobenzophenone and 4,4' -diaminobenzophenone; benzoin ether initiators such as benzoin propyl ether and benzoin diethyl ether; thioxanthone-based initiators such as 4-isopropylthioxanthone; xanthone, fluorenone, and the like. The content of the radical polymerization initiator is usually 0.1 to 10 parts by mass based on 100 parts by mass of the radical polymerizable compound. The radical polymerization initiator may contain 2 or more kinds.

Examples of the radical polymerizable adhesive composition include radical polymerizable compositions described in Japanese patent application laid-open No. 2016-126345, japanese patent application laid-open No. 2016-153474, and International publication No. 2017/183335.

The active energy ray-curable adhesive composition may contain, if necessary, an additive such as an ion scavenger, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, a defoaming agent, an antistatic agent, a leveling agent, a solvent, and the like.

The lamination of the polarizing plate and the polyester resin film can be performed as follows: an adhesive composition is applied to at least one of the bonding surfaces selected from the bonding surface of the polarizing plate and the bonding surface of the polyester resin film, the two are laminated via an application layer of the adhesive composition, and the laminated layers are pressed from the top and bottom by a bonding roller or the like, and then the adhesive layer is dried, cured by irradiation with active energy rays, or cured by heating.

The adhesive composition may be formed by various coating methods such as die coater, comma coater, gravure coater, bar coater, and blade coater.

The adhesive composition may be cast between the polarizing plate and the polyester resin film while being continuously supplied so that the joint surface of the polarizing plate and the polyester resin film is inside.

Before forming the coating layer of the adhesive layer, at least one bonding surface selected from the bonding surface of the polarizer and the bonding surface of the polyester resin film may be subjected to an easy-to-adhere treatment such as saponification treatment, corona treatment, plasma treatment, primer treatment, anchor coating treatment, and the like.

The lamination of the polarizer and the acrylic resin film may be performed in the same manner as the lamination of the polarizer and the polyester resin film.

The light irradiation intensity upon irradiation with the active energy ray is determined according to the composition of the active energy ray-curable adhesive composition, and is not particularly limited, but is preferably 10mW/cm ² or more and 1,000mW/cm ² or less. The irradiation intensity is preferably an intensity in a wavelength region effective for activation of the photo-cationic polymerization initiator or the photo-radical polymerization initiator. The irradiation is performed 1 or more times at such a light irradiation intensity, and the cumulative light amount is preferably 10mJ/cm ² or more, more preferably 100mJ/cm ² or more and 1,000mJ/cm ² or less.

The light source used for polymerization curing of the active energy ray-curable adhesive composition is not particularly limited, and examples thereof include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a halogen lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

When the 1 st adhesive layer and the 2 nd adhesive layer are formed of the aqueous adhesive composition, the thickness of the 1 st adhesive layer and the 2 nd adhesive layer may be, for example, 5 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less, and may be 0.01 μm or more, preferably 0.05 μm or more.

When the 1 st adhesive layer and the 2 nd adhesive layer are formed of a curable adhesive composition (preferably an active energy ray curable adhesive composition), the thickness of the 1 st adhesive layer and the 2 nd adhesive layer may be, for example, 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less, may be 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more.

The 1 st adhesive layer and the 2 nd adhesive layer are preferably formed of the same kind of adhesive composition, respectively.

The 1 st adhesive layer and the 2 nd adhesive layer are preferably formed of a cationic polymerization type adhesive composition, respectively.

The 1 st adhesive layer and the 2 nd adhesive layer may have the same thickness or may have different thicknesses, but are preferably the same thickness. The term "same thickness" also includes an error of about 0.3 μm.

< Light diffusion layer >)

In order to improve visibility (brightness) in an oblique direction, the polarizing plate of the present invention may further include a light diffusion layer.

The light diffusion layer is a layer comprising a light-transmitting resin as a base material, and may be a layer comprising light-transmitting fine particles dispersed in a light-transmitting resin, and is disclosed in, for example, japanese patent application laid-open publication No. 2012-048223, japanese patent application laid-open publication No. 2012-212120, and the like.

The light-transmitting resin is not particularly limited as long as it has light-transmitting properties, and for example, an ionizing radiation-curable resin such as an ultraviolet-curable resin or an electron beam-curable resin, a cured product of a thermosetting resin, a cured product of a thermoplastic resin or a metal alkoxide, or the like can be used. In the case of using an ionizing radiation curable resin, a thermosetting resin, or a metal alkoxide, the resin is cured by irradiation with an ionizing radiation or heating to form a light-transmitting resin. Among them, the ionizing radiation curable resin is preferable in terms of having high hardness and being capable of imparting high scratch resistance when used as a polarizer protective film provided on the surface of a liquid crystal display device.

Examples of the ionizing radiation curable resin include polyfunctional acrylates such as acrylic acid and methacrylic acid esters of polyhydric alcohols; and multifunctional urethane acrylates synthesized from diisocyanates and polyols, and hydroxy esters of acrylic acid or methacrylic acid, and the like. In addition to these, polyether resins, polyester resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and the like having acrylate functional groups can be used.

Examples of the thermosetting resin include phenolic resins, urea melamine resins, epoxy resins, unsaturated polyester resins, and silicone resins, in addition to thermosetting urethane resins containing an acrylic polyol and an isocyanate prepolymer.

Examples of the thermoplastic resin include cellulose derivatives such as acetyl cellulose, nitrocellulose, acetyl butyl cellulose, ethyl cellulose, and methyl cellulose; vinyl resins such as vinyl acetate and copolymers thereof, vinyl chloride and copolymers thereof, vinylidene chloride and copolymers thereof; acetal resins such as polyvinyl formal and polyvinyl butyral; acrylic resins and copolymers thereof, methacrylic resins and copolymers thereof; a polystyrene resin; a polyamide resin; a polyester resin; polycarbonate resin, and the like.

As the metal alkoxide, a silicon oxide-based substrate or the like using a silicon alkoxide-based material as a raw material can be used. Specifically, tetramethoxysilane, tetraethoxysilane, and the like can be hydrolyzed, dehydrated, and condensed to prepare an inorganic matrix or an organic-inorganic composite matrix (light-transmitting resin).

As the light-transmitting fine particles, organic fine particles or inorganic fine particles having light transmission properties can be used. Examples thereof include organic fine particles including acrylic resin, melamine resin, polyethylene, polystyrene, silicone resin, and acrylic-styrene copolymer, and inorganic fine particles including calcium carbonate, silica, alumina, barium carbonate, barium sulfate, titanium oxide, and glass. Alternatively, spheres of organic polymer or hollow glass beads may be used. The light-transmitting fine particles may be composed of 1 kind of fine particles, or may contain 2 or more kinds of fine particles. The light-transmitting fine particles may be in any of spherical, flat, plate-like, needle-like, amorphous, and the like, and are preferably spherical or substantially spherical.

The filling ratio of the light-transmitting fine particles is preferably 40% or more, more preferably 50% or more.

The weight average particle diameter of the light-transmitting fine particles is preferably 0.5 μm or more and 15 μm or less, more preferably 3 μm or more and 9 μm or less. If the weight average particle diameter of the light-transmitting fine particles is less than 0.5. Mu.m, the visible light having a wavelength in the range of 380nm to 800nm may not be sufficiently scattered. In addition, when the weight average particle diameter exceeds 15 μm, the thickness of the entire light diffusion layer becomes thick, which may prevent the thickness of the polarizing plate or the display from being reduced. The weight average particle diameter of the light-transmitting fine particles was measured using Coulter Multisizer (manufactured by BECKMAN Coulter corporation) using the Coulter principle (pore resistance method).

The refractive index of the light-transmitting fine particles is preferably set to be larger than that of the light-transmitting resin, and the difference is preferably in the range of 0.04 to 0.15. By setting the refractive index difference between the light-transmissive particles and the light-transmissive resin to be within the above range, appropriate internal scattering due to the refractive index difference between the light-transmissive particles and the light-transmissive resin can be generated, and a light diffusing function can be imparted.

The light diffusion layer may be a layer formed of an adhesive composition having light diffusion properties (hereinafter, also referred to as a light diffusion adhesive composition) in which spherical fine particles are blended in an acrylic resin. At this time, the refractive index difference between the acrylic resin and the spherical fine particles is in the range of more than 0.01 and less than 0.09. The refractive index difference is preferably more than 0.01 and 0.07 or less, more preferably more than 0.01 and 0.04 or less. If the refractive index difference between the two is 0.01 or less, the resulting adhesive layer does not exhibit desired optical properties, and as a result, becomes an adhesive that is a near transparent adhesive. On the other hand, if the refractive index difference between the acrylic resin and the spherical fine particles becomes too large, light diffusion is strong, and therefore the brightness when the liquid crystal display device is viewed from the front is lowered.

The spherical particles satisfying the above conditions may be used alone or in combination of 2 or more. When 2 or more kinds of spherical particles are mixed, spherical particles having different refractive indexes may be mixed, or only spherical particles having different particle diameters may be mixed.

The acrylic resin contained in the adhesive composition may be composed of an acrylic resin having a molecular weight in the range of thousands to 200 tens of thousands in weight average molecular weight. The spherical fine particles having an average particle diameter in the range of 0.5 to 15 μm are selected and blended in a proportion of 20 to 80 parts by mass relative to 100 parts by mass of the acrylic resin. By setting to such a specific combination, good adhesive properties and optical properties are exhibited.

In order to form a good crosslinked structure when the adhesive layer is formed, the light diffusing adhesive composition may contain a crosslinking agent. In addition, an ionic compound may be contained in order to impart antistatic properties.

The material of the spherical fine particles is not particularly limited, and known organic fine particles and inorganic fine particles can be used. Examples of the organic fine particles include resin particles containing a polyolefin resin such as polystyrene, polyethylene, and polypropylene, a polymethacrylate resin, a (meth) acrylic resin such as a polyacrylate resin, and the like, and may be crosslinked polymers that are crosslinked. Further, a copolymer resin obtained by copolymerizing 2 or more monomers selected from ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene, and the like may be used. Examples of the inorganic fine particles include particles containing silica, silicone resin, titanium oxide, aluminum oxide, and the like. In view of dispersibility in acrylic resins, coatability of the adhesive composition, optical properties of the resulting adhesive layer, and the like, the fine particles preferably contain a silicone resin or a polymethyl methacrylate resin.

The amount of the spherical fine particles is 20 to 80 parts by mass based on 100 parts by mass of the nonvolatile component of the acrylic resin. If the amount is less than 20 parts by mass relative to 100 parts by mass of the acrylic resin, the desired optical properties, particularly haze, will not be exhibited, while if the amount exceeds 80 parts by mass, the adhesive properties such as peeling due to the decrease in the adhesive force of the resulting adhesive layer will be reduced.

The light diffusion layer may further include an antireflection layer on the viewing side when the polarizing plate is laminated on the liquid crystal display device. The antireflection layer is provided to reduce reflectance as much as possible, and by forming the antireflection layer, reflection glare on a display screen can be prevented. Examples of the antireflection layer include a low refractive index layer made of a material having a lower refractive index than the light diffusion layer.

The light diffusion layer preferably has a total haze of 20% or more and an internal haze of 20% or more. The "total haze" is a value obtained by the following expression [ 1] based on a ratio of total light transmittance (Tt) indicating the total amount of light transmitted by irradiating the light diffusion layer with light to diffuse light transmittance (Td) transmitted by diffusing the light diffusion layer.

Total haze (%) = (Td/Tt) ×100 [1]

The total light transmittance (Tt) is the sum of the parallel light transmittance (Tp) and the diffuse light transmittance (Td) that are transmitted while being coaxial with the incident light. The total light transmittance (Tt) and the diffuse light transmittance (Td) are values measured in accordance with JIS K7361.

The "internal haze" of the light diffusion layer refers to a haze other than the haze (surface haze) caused by the surface shape of the light diffusion layer in the total haze.

When the total haze and/or internal haze is less than 20%, light scattering is insufficient, and it is difficult to obtain sufficient wide viewing angle performance. In addition, when the total haze and/or the internal haze exceeds 90%, light scattering becomes strong, and when a polarizing plate having a light diffusion layer is applied to a liquid crystal display device, front contrast may be lowered. In addition, when the total haze and/or the internal haze exceeds 90%, the transparency of the light diffusion layer tends to be impaired. The total haze and/or internal haze is preferably 25% or more, more preferably 30% or more, and still more preferably 35% or more, respectively. Further, it is preferably 85% or less, more preferably 80% or less, and still more preferably 75% or less.

When a layer using a light-transmitting resin as a base material is used as the light diffusion layer, the layer may be bonded to the polyester resin film via an adhesive layer. The adhesive layer that can be used for bonding may be an adhesive layer having light diffusion property formed from the light diffusion adhesive composition, or may be an adhesive layer not having light diffusion property. When an adhesive layer having light diffusion properties is used, both the adhesive layer having light diffusion properties and a layer (film) based on a light-transmitting resin are regarded as light diffusion layers.

In addition, as the light diffusion layer, only an adhesive layer having light diffusion property may be used.

< Other constituent Condition >

The polarizing plate of the present invention may further comprise an optically functional film in order to impart a desired optical function. Examples of the optically functional film include a retardation film, a condensing plate, and a brightness enhancement film.

The optically functional film is bonded to the polarizing plate via an adhesive layer or an adhesive layer. The adhesive layer and the pressure-sensitive adhesive layer are the same as the adhesive layer and the pressure-sensitive adhesive layer described above, respectively.

< Polarizing plate with adhesive layer >

The present invention also relates to a polarizing plate with an adhesive layer comprising the above polarizing plate and an adhesive layer. The polarizing plate with the adhesive layer can be applied to a liquid crystal display device, for example. In a liquid crystal display device, a polarizing plate with an adhesive layer is arranged on the viewing side and/or the back side of a liquid crystal cell as an image display element.

Fig. 6 shows an example of the layer structure of the polarizing plate with an adhesive layer of the present invention. The polarizing plate with adhesive layer 2 shown in fig. 6 includes a polarizing plate including, in order, a polyester resin film 10, a1 st adhesive layer 15, a polarizing plate 30, a2 nd adhesive layer 25, and a (meth) acrylic resin film 20, and an adhesive layer 40.

Like the polarizing plate 2 with an adhesive layer shown in fig. 6, the adhesive layer 40 is preferably laminated on the surface of the (meth) acrylic resin film 20 opposite to the polarizing plate 30.

The polarizing plate with an adhesive layer may be attached to the liquid crystal cell via its adhesive layer 40. That is, from the viewpoint of visibility, in the liquid crystal panel and the liquid crystal display device, the polarizing plate of the present invention is preferably arranged such that the (meth) acrylic resin film 20 side thereof is the liquid crystal cell side.

The adhesive layer 40 may be laminated on either the polyester resin film 10 or the (meth) acrylic resin film 20, but as described above, it is preferably laminated on the (meth) acrylic resin film 20. If the pressure-sensitive adhesive layer 40 is laminated on the (meth) acrylic resin film, the polyester resin film 10 is disposed on the side (for example, the viewing side) opposite to the image display element. In the case where the optically functional film is laminated on the side of the (meth) acrylic resin film opposite to the side of the polarizing plate 30, the adhesive layer 40 may be further laminated on the side of the optically functional film opposite to the (meth) acrylic resin film 20.

As the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive composition containing a (meth) acrylic resin, a silicone resin, a polyester resin, a polyurethane resin, a polyether resin, or the like as a base polymer, and the like can be given. Among them, from the viewpoints of transparency, adhesion, reliability, heat resistance, reworkability, and the like, (meth) acrylic adhesive compositions containing a (meth) acrylic resin are preferable.

The thickness of the pressure-sensitive adhesive layer is determined by the adhesive force or the like, and is, for example, 1 μm or more and 50 μm or less, preferably 2 μm or more and 40 μm or less, and preferably 3 μm or more and 30 μm or less.

Examples

The present invention will be described in further detail with reference to examples. In the examples, "%" and "parts" are mass% and parts unless otherwise specified.

Production example 1 production of polarizing plate

The long polyvinyl alcohol film (average polymerization degree: about 2400, saponification degree: 99.9 mol% or more, thickness: 60 μm) was continuously fed and immersed in a swelling bath containing pure water at 20℃for a residence time of 31 seconds (swelling step). Then, the film pulled out of the swelling bath was immersed in a dyeing bath containing iodine at 30℃with a residence time of 122 seconds, in which the ratio of potassium iodide/water was 2/100 (mass ratio) (dyeing step). Next, the film pulled out of the dyeing bath was immersed in a crosslinking bath at 56 ℃ with a residence time of 70 seconds, in which potassium iodide/boric acid/water is 12/4.1/100 (mass ratio), and then immersed in a crosslinking bath at 40 ℃ with a residence time of 13 seconds, in which potassium iodide/boric acid/water is 9/2.9/100 (mass ratio) (crosslinking step). In the dyeing step and the crosslinking step, longitudinal uniaxial stretching is performed by stretching between rolls in a bath. The total stretch ratio was set to 5.5 times based on the raw film. Next, the film pulled out of the crosslinking bath was immersed in a cleaning bath containing pure water at 5 ℃ for a residence time of 3 seconds (cleaning step), and then introduced into a drying oven at 80 ℃ for a residence time of 190 seconds to be dried (drying step), whereby a polarizing plate was obtained. The thickness of the polarizing plate obtained in the above was 24. Mu.m.

( Production example 2: production of polyethylene terephthalate resin (1) )

86.4 Parts of terephthalic acid and 64.6 parts of ethylene glycol were charged into an esterification reaction vessel while the esterification reaction vessel was heated to 200℃to obtain a mixture. To the resulting mixture, 0.017 parts of antimony trioxide, 0.064 parts of magnesium acetate tetrahydrate and 0.16 parts of triethylamine as a catalyst were added while stirring the resulting mixture. After the gauge pressure in the esterification reaction tank was set to 0.34MPa and the esterification reaction was further carried out under pressure at 240 ℃, the esterification reaction tank was returned to normal pressure, and 0.014 parts of phosphoric acid was added. Further, the temperature was raised to 260℃over 15 minutes, and 0.012 parts of trimethyl phosphate was added to obtain a mixture. The resultant mixture was subjected to dispersion treatment with a high-pressure dispersing machine after 15 minutes, and further, after 15 minutes, the resultant esterification reaction product was fed to a polycondensation reaction tank, and the polycondensation reaction was carried out under reduced pressure at 280 ℃.

After completion of the polycondensation reaction, the mixture was filtered with a NASLON-unit filter having a 95% blocking diameter of 5 μm, extruded from a nozzle into a bundle, cooled and solidified with cooling water previously subjected to filtration treatment (pore diameter: 1 μm or less), and cut into pellets to obtain a polyethylene terephthalate resin (hereinafter referred to as PET (1)).

( Production example 3: production of polyethylene terephthalate resin (2) )

10 Parts of the dried ultraviolet absorber (2, 2' - (1, 4-phenylene) bis (4H-3, 1-benzoxazin-4-one) and 90 parts of PET (1) obtained in production example 2 were mixed, and a kneading extruder was used to obtain a polyethylene terephthalate resin (2) (hereinafter referred to as PET (2)) containing the ultraviolet absorber.

PREPARATION EXAMPLE 4 preparation of coating liquid for Forming an easy-to-bond layer

A water-dispersible sulfonate-containing metal salt-based copolyester resin was produced by transesterification and polycondensation of 8 mol% of a dicarboxylic acid component comprising 46 mol% of terephthalic acid, 46 mol% of isophthalic acid and 5-sodium isophthalic acid sulfonate (Japanese, 5-sevelo) with 50 mol% of glycol component comprising ethylene glycol and 50 mol% of neopentyl glycol by a conventional method.

Next, 51.4 parts of water, 38 parts of isopropyl alcohol, 5 parts of n-butyl cellosolve, and 0.06 parts of a nonionic surfactant were mixed to obtain a mixture. While heating and stirring the obtained mixture to 77 ℃,5 parts of the water-dispersible sulfonate-group-containing copolymerized polyester resin was added, and stirring was continued until solidification of the resin disappeared, to obtain an aqueous resin dispersion. The resulting aqueous resin dispersion was cooled to 25℃to obtain a uniform water-dispersible copolyester resin solution having a solid content of 5.0% by mass.

3 Parts of aggregated silica particles were dispersed in 50 parts of water to obtain an aqueous dispersion of aggregated silica particles. To 99.46 parts of the water-dispersible copolyester resin solution was added 0.54 part of an aqueous dispersion of aggregated silica particles, and 20 parts of water was further added while stirring, to obtain a coating solution for forming an easy-to-bond layer.

Production example 5 production of protective film 1

PET (3) obtained by mixing 90 parts of PET (1) produced in production example 2 and 10 parts of PET (2) produced in production example 3 was dried under reduced pressure at 135℃for 6 hours, and then fed to an extruder 2 (for an intermediate layer B). Further, the PET (1) was dried and then fed to the extruder 1 (for the outer layer A and the outer layer C). The PET (1) supplied to the extruder 1 and the PET (3) supplied to the extruder 2 were melted at 285 ℃. The 2 polymers were each filtered through a stainless steel sintered filter medium (nominal filtration accuracy of 10 μm particles 95% cut), laminated with 2 kinds of 3 layers of joint blocks, extruded from a tube head into a sheet, and then wound around a casting drum having a surface temperature of 30 ℃ by an electrostatic casting method to be cooled and solidified, thereby producing an unstretched PET film. At this time, the ratio of the thicknesses of the layer a, the layer B, and the layer C was 10:80:10, the discharge amount of each extruder was adjusted.

Next, the coating liquid for forming an easy-to-adhere layer was applied to both sides of the obtained unstretched PET film by a reverse roll method so that the coating amount after drying became 0.08g/m ², and then dried at 80℃for 20 seconds.

The unstretched PET film having the coating layer formed thereon was stretched to 4.0 times in the width direction in a hot air region at a temperature of 125 ℃ while holding the end of the film with a jig by a tenter stretcher. Next, the film was subjected to a relaxation treatment of 3.0% in the width direction after being treated at 225 ℃ for 10 seconds while maintaining the stretched width in the width direction, to obtain a uniaxially stretched PET film having an easy-to-adhere layer formed thereon with a film thickness of about 80 μm. This was used as the protective film 1.

Production example 6 production of protective film 2

60 Parts of pentaerythritol triacrylate and 40 parts of a polyfunctional urethane acrylate (a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate) were mixed in a propylene glycol monomethyl ether solution, and the concentration of the solid content was adjusted to 60%, thereby obtaining an ultraviolet-curable resin composition.

Next, 5 parts of "Lucirin TPO" (manufactured by BASF corporation, chemical name: 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide) was added as a photopolymerization initiator to 100 parts of the solid content of the ultraviolet-curable resin composition, and the mixture was diluted with propylene glycol monomethyl ether so that the solid content concentration became 60%, to prepare a coating liquid.

The coating liquid was coated on a uniaxially stretched PET film (protective film 1) having a film thickness of about 80. Mu.m, and dried in a dryer set at 80℃for 1 minute. The dried transparent resin film was irradiated with light from a high-pressure mercury lamp having an intensity of 20mW/cm ² so that the light quantity in terms of h-line became 300mJ/cm ², and the ultraviolet-curable resin composition layer was cured to prepare a film having a hard coat layer on the transparent resin film. This was used as the protective film 2. The thickness of the resulting hard coat layer was 4. Mu.m.

Production example 7 production of protective film 3

A coating liquid for forming a hard coat layer was prepared by mixing 10 parts of dipentaerythritol triacrylate, 10 parts of pentaerythritol tetraacrylate, 30 parts of urethane acrylate (UA-306T manufactured by Co., ltd.), 2.5 parts of Irgacure 184 (manufactured by Ciba Japan Co., ltd.) as a photopolymerization initiator, 50 parts of methyl ethyl ketone as a solvent, and 50 parts of butyl acetate. The coating liquid was coated on a uniaxially stretched PET film (protective film 1) having a film thickness of about 80 μm by a bar coater, and dried in a dryer set at 80℃for 1 minute. For the transparent resin film after drying, a metal halide lamp was used, and irradiation with an external light was performed at an output of 120W for 10 seconds Zhong Zi from a distance of 20cm, thereby forming a hard coat layer. The resulting hard coat layer had a thickness of 5 μm and a refractive index of 1.52.

Next, to tetraethoxysilane and 1h,2 h-perfluorooctyl trimethoxysilane 95: to the 5 (molar ratio) mixture, isopropyl alcohol and 0.1N hydrochloric acid were added to hydrolyze the mixture, thereby obtaining a solution of a polymer containing an organosilicon compound composed of an oligomer. To this solution, low refractive index silica fine particles having voids therein were mixed, and isopropyl alcohol was added, thereby obtaining a low refractive index layer forming coating liquid containing 2% of an organosilicon compound and 2% of low refractive index silica fine particles. The obtained coating liquid for forming a low refractive index layer was coated on the hard coat layer by a bar coater, and dried in a dryer set at 120 ℃ for 1 minute, thereby forming a low refractive index layer. The thickness of the resulting low refractive index layer was about 0.1 μm and the refractive index was 1.37. Thus, an antireflection film having a hard coat layer and a low refractive index layer on a transparent resin film was produced. This was used as the protective film 3.

Production example 8 production of protective film 4

A polyester film having an easy-to-adhere layer formed on one side was produced in the same manner as the protective film 1 except that an easy-to-adhere layer was formed on only one side of the unstretched PET film. This was used as the protective film 4.

Production example 9 production of protective film 5

A mixture (lactone ring content: 28.5%) of 90 parts of a (meth) acrylic resin having a lactone ring structure and 10 parts of an acrylonitrile-styrene (AS) resin was extruded to obtain an acrylic resin film having a thickness of 40 μm which was stretched to 2.0 times in the machine direction and 2.4 times in the transverse direction. This was used as the protective film 5.

Production example 10 production of protective film 6

An acrylic resin film having a thickness of 60 μm was produced from a mixture of 70 parts of a copolymer of methyl methacrylate/methyl acrylate=96/4 (mass ratio) and 30 parts of acrylic rubber particles (layer 1: copolymer of methyl methacrylate and allyl methacrylate (mass ratio 99.8/0.2)/layer 2: copolymer of butyl acrylate and styrene and allyl methacrylate (mass ratio 79/19/2)/layer 3: copolymer of methyl acrylate and ethyl acrylate (mass ratio 96/4)) which were an acrylic multilayer polymer constituted of a 3-layer structure by melt extrusion. This was used as the protective film 6.

Example 1 >

One surface of each of the protective film 1 obtained in production example 5 and the protective film 5 obtained in production example 9 was subjected to corona treatment, and an epoxy-based ultraviolet curable adhesive was applied to the corona-treated surface using an adhesive applicator. Next, the polarizing plate obtained in production example 1 was laminated on the coating layer, and then pressed and bonded using a bonding roller, thereby obtaining a polarizing plate precursor. At this time, the protective film 1 (polyester resin film) is bonded so that the stretching direction (width direction) thereof is perpendicular to the absorption axis direction of the polarizer (stretching direction of the polarizer). The polarizing plate precursor was irradiated with ultraviolet light from the protective film 5 side using an ultraviolet irradiation device (lamp: a metal halide lamp manufactured by EYE GRAPHICS company) with a belt conveyor so that the cumulative light amount became 200mJ/cm ² (UVB), and the adhesive was cured to obtain a polarizing plate. As described above, a polarizing plate having a protective film 1 (polyester-based resin film)/adhesive layer/polarizing plate/adhesive layer/protective film 5 ((meth) acrylic-based resin film) was obtained.

Next, an adhesive layer with a release film having a (meth) acrylic adhesive layer (thickness 20 μm) on the release treated surface of the release film was prepared. After corona treatment of the surface of the protective film 5 ((meth) acrylic resin film), the pressure-sensitive adhesive layer with a release film was laminated on the protective film 5 ((meth) acrylic resin film) side of the above-mentioned polarizing plate, whereby a polarizing plate with a pressure-sensitive adhesive layer was obtained. The polarizing plate with an adhesive layer has a structure of a protective film 1 (polyester resin film)/adhesive layer/polarizer/adhesive layer/protective film 5 ((meth) acrylic resin film)/adhesive layer/release film).

Example 2 >

A polarizing plate having a structure of protective film 2 (polyester resin film)/adhesive layer/polarizing plate/adhesive layer/protective film 5 ((meth) acrylic resin film) was obtained in the same manner as in example 1 except that protective film 1 was replaced with protective film 2 and a surface different from the surface having the hard coat layer was subjected to corona treatment. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in example 1.

Example 3 >

A polarizing plate having a structure of protective film 3 (polyester resin film)/adhesive layer/polarizing plate/adhesive layer/protective film 5 ((meth) acrylic resin film) was obtained in the same manner as in example 1 except that protective film 1 was replaced with protective film 3 and a surface different from the surface having the low reflection layer was subjected to corona treatment. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in example 1.

Example 4 >

A polarizing plate having a configuration of protective film 4 (polyester resin film)/adhesive layer/polarizing plate/adhesive layer/protective film 5 ((meth) acrylic resin film) was obtained in the same manner as in example 1 except that the protective film 1 was replaced with protective film 4 and the surface on which the adhesive layer was laminated was subjected to corona treatment. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in example 1.

Example 5 >

A polarizing plate having a configuration of a protective film 1 (polyester resin film)/adhesive layer/polarizing plate/adhesive layer/protective film 6 ((meth) acrylic resin film)) was obtained in the same manner as in example 1, except that the protective film 6 was used instead of the protective film 5. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in example 1.

Comparative example 1 >

A biaxially stretched polyethylene terephthalate (PET) protective film (Mitsubishi chemical corporation) containing a polyester resin was prepared to a thickness of 38. Mu.m. The surface reflectance and the phase difference value Re (Re 1 to Re 4) of the polyester resin film are shown in Table 1.

A polarizing plate having a constitution of a protective film (biaxially stretched polyester resin film having a thickness of 38 μm)/an adhesive layer/a polarizing plate/an adhesive layer/a protective film 5 ((meth) acrylic resin film) was obtained in the same manner as in example 1, except that a polyester resin having a thickness of 38 μm was used. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in example 1. The polarizing plate was bonded so that the stretching direction (width direction) of the biaxially stretched polyethylene terephthalate protective film was perpendicular to the absorption axis direction of the polarizing plate (stretching direction of the polarizing plate) as in example 1. The stretching direction (width direction) of the biaxially stretched polyethylene terephthalate protective film means the width direction when the film is rolled out from the film roll.

Comparative example 2 >

A polarizing plate having a structure of a protective film 1 (polyester resin film)/an adhesive layer/a polarizing plate/an adhesive layer/a protective film (cellulose resin film) was obtained in the same manner as in example 1, except that a protective film (manufactured by KONICA MINOLTA corporation) of triacetyl cellulose (TAC) having a thickness of 40 μm was used instead of the (meth) acrylic resin film.

Next, an adhesive layer with a release film having a (meth) acrylic adhesive layer (thickness 20 μm) on the release treated surface of the release film was prepared. After corona treatment of the surface of the cellulose resin film, the pressure-sensitive adhesive layer with a release film was laminated on the cellulose resin film side of the polarizing plate, thereby obtaining a polarizing plate with a pressure-sensitive adhesive layer. The polarizing plate with an adhesive layer has a structure of a protective film 1 (polyester resin film)/an adhesive layer/a polarizing plate/an adhesive layer/a protective film (cellulose resin film)/an adhesive layer/a release film.

Comparative example 3 >

A polarizing plate having a protective film (biaxially stretched polyester resin film having a thickness of 38 μm)/an adhesive layer/a polarizing plate/an adhesive layer/a protective film (cellulose resin film) was obtained in the same manner as in example 1 except that a biaxially stretched polyester resin film having a thickness of 38 μm (manufactured by mitsubishi chemical company) used in comparative example 1 was used as the polyester resin film, and a protective film (manufactured by KONICA MINOLTA company) having a thickness of 40 μm used in comparative example 2 was used instead of the (meth) acrylic resin film. In addition, a polarizing plate with an adhesive layer was obtained in the same manner as in comparative example 2. The polarizing plate was bonded so that the stretching direction (width direction) of the biaxially stretched polyester resin film was perpendicular to the absorption axis direction of the polarizing plate (stretching direction of the polarizing plate) as in example 1. The stretching direction (width direction) of the biaxially stretched polyester resin film means the width direction when the film is wound out from the film roll.

(Measurement of in-plane phase Difference value of polyester resin film)

The phase difference values Re1 to Re4 of the polyester resin films used in the examples and comparative examples were measured at a wavelength of 587nm using a phase difference measuring apparatus (KOBRA-HB-RESPC, manufactured by prince measuring instruments Co., ltd.). The results are shown in Table 1.

Re1: the phase difference value measured in the 1 st arrangement, wherein the polyester resin film is arranged in such a manner that the angle formed by the surface of the polyester resin film and the measuring direction becomes 90 DEG

Re2: the phase difference value measured in the 2 nd arrangement, wherein the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction becomes 60 ° by rotating the polyester resin film by 30 ° about the fast axis thereof as the central axis

Re3: in the 3 rd arrangement, the polyester resin film Re4 is arranged such that the polyester resin film in the 1 st arrangement is rotated by 30 ° about an axis forming an angle of 45 ° with respect to the fast axis thereof in the plane of the polyester resin film, and the angle formed by the plane of the polyester resin film and the measurement direction becomes 60 °, in the 3 rd arrangement: the phase difference value measured in the 4 th arrangement, in which the polyester resin film in the 1 st arrangement is arranged such that the angle between the surface of the polyester resin film and the measurement direction becomes 60 ° by rotating the polyester resin film by 30 ° about the slow axis thereof as the center axis

(Measurement of the phase Difference in the thickness direction of the polyester resin film)

The retardation values Rth in the thickness direction of the polyester resin films used in examples and comparative examples were measured at a wavelength of 587nm using a retardation measuring apparatus (KOBA-HB-RESPC, manufactured by KORA measuring Co., ltd.) in a state where the angle between the surface of the polyester resin film and the measurement direction was 60 ℃. Further, re1/Rth is obtained from the phase difference Rth and the phase difference Re1 in the thickness direction. The results are shown in Table 1.

(Measurement of surface reflectance of polyester resin film)

The polyester resin films used in examples and comparative examples were laminated with a (meth) acrylic pressure-sensitive adhesive layer (thickness 20 μm) having a release film on the surface subjected to corona treatment in examples and comparative examples, to obtain a polyester resin film with a pressure-sensitive adhesive layer.

The release film was peeled off from the obtained polyester resin film with an adhesive layer and then attached to the surface of a black acrylic plate (trade name "KANASE LITE 1410", product of the company KANASE), to obtain a laminate having a structure of a polyester resin film/an adhesive layer/a black acrylic plate.

The laminate having the above-described structure of the polyester film/adhesive layer/black acrylic plate was measured for the surface reflectance of the polyester film surface at a wavelength of 550nm by a spectrocolorimeter CM2600d (KONICA MINOLTA JAPAN, inc.). The results are shown in Table 1.

((Measurement of the phase difference in the thickness direction of the (meth) acrylic resin film or the cellulose resin film)

The (meth) acrylic resin film or the cellulose resin film used in examples and comparative examples was subjected to measurement of a phase difference value Rth in the thickness direction before and after the test at a temperature of 85 ℃ and a relative humidity of 85% rh at a wavelength of 587nm in a state where the angle between the surface of the resin film and the measurement direction was 50 ° by using a phase difference measuring device (KOBRA-WPR, manufactured by prince measuring instruments, inc.), and the absolute value |Δrth| of the amount of change in the phase difference value Rth in the thickness direction (Δrth) was obtained. The results are shown in Table 1.

(Glass transition temperature)

The glass transition temperature (Tg) of the (meth) acrylic resin film used in the examples was determined by using a differential scanning calorimeter (Seiko Instruments, EXSTAR 6000). The results are shown in Table 1.

(Determination of Rainbow patterns)

After the release film was peeled off from the polarizing plate with an adhesive layer obtained in example 1, the adhesive layer side was bonded to an alkali-free glass substrate (thickness 0.7mm, "Eagle XG" manufactured by corning corporation), to obtain a glass-bonded polarizing plate laminate.

The above-mentioned polarizing plate laminate laminated with glass was placed on a backlight light source so that the glass substrate side was a light source, and visual observation of the polarizing plate was performed in an oblique direction from the polyester resin film side of the polarizing plate in a dark place, and the visibility of rainbow marks was confirmed, and was evaluated according to the following criteria.

The polarizing plates with an adhesive layer obtained in examples 2 to 5 and the polarizing plates with an adhesive layer obtained in comparative examples 1 to 3 were evaluated for rainbow patterns in the same manner. The results are shown in Table 1.

And (3) the following materials: rainbow patterns are very weak

And (2) the following steps: rainbow pattern weakness

Delta: the rainbow lines are medium

X: rainbow pattern

(Measurement of light leakage)

The polarizing plate with an adhesive layer obtained in example 1 was cut into 150mm×90mm sizes. Either the long side or the short side of the cut polarizing plate with the adhesive layer is parallel to the absorption axis. The release film was peeled off from the cut polarizing plate with an adhesive layer (the longitudinal direction was parallel to the absorption axis), and then the adhesive layer was bonded to one surface of an alkali glass substrate (thickness 1.1mm, manufactured by Nitro Corp.). The adhesive-equipped polarizing plate obtained by cutting the adhesive-equipped polarizing plate obtained in example 1 in the same manner as described above (the short side direction was parallel to the absorption axis) was bonded to a surface of the glass substrate different from the polarizing plate bonding surface so that the transmission axes of the 2 polarizing plates were orthogonal to each other with the glass substrate interposed therebetween, thereby obtaining an optical laminate 1.

After the obtained optical laminate 1 was left to stand in an environment of 85 ℃ for 500 hours, the optical laminate was placed on a backlight source, and the light leakage in the center of the sample was visually observed, and the evaluation was performed in a dark place according to the following criteria. An optical laminate was produced in the same manner as the adhesive layer-attached polarizing plate obtained in example 2 to example 5 and the adhesive layer-attached polarizing plate obtained in comparative example 1 to comparative example 3, and light leakage was evaluated in the same manner. The results are shown in Table 1.

And (3) the following materials: the light leakage is very weak

O: weak light leakage

X: leakage light intensity

TABLE 1

The polarizing plate of the present invention sufficiently suppresses rainbow lines coming from an oblique direction and suppresses light leakage in a high-temperature environment. On the other hand, the polarizing plate of comparative example 2 using the cellulose resin film was insufficient in suppressing light leakage. This is presumably because the polyester film, which is another polarizer protective film, is low in moisture permeability, so that moisture contained in the polarizer is difficult to diffuse from the polarizer to the outside and remains in the polarizer, and the change in the molecular orientation and molecular structure of the cellulose resin film increases due to the remaining moisture, and the change in the phase difference value of the cellulose resin film increases. In addition, in the case of applying a biaxially stretched polyester film of 38 μm, any of the phase difference values Re1 to Re4 is low, and rainbow lines observed from the oblique direction are not sufficiently suppressed.

Claims

1. A polarizing plate comprising, in order, a polyester resin film, a1 st adhesive layer, a polarizing plate, a 2 nd adhesive layer and a (meth) acrylic resin film,

The polyester resin film has a phase difference Re defined by the formula (1) satisfying the following [ i ] to [ iv ],

Re＝(n_x-n_y)×d (1)

Where n _x denotes the refractive index in the slow axis direction in the film plane, n _y denotes the refractive index in the fast axis direction in the film plane, d denotes the film thickness,

[I] The phase difference Re1 measured in the 1 st arrangement is 6000nm or more, in the 1 st arrangement, the polyester resin film is arranged in a manner that the angle formed by the surface of the polyester resin film and the measuring direction is 90 degrees,

[ Ii ] in the 2 nd configuration of the measurement of the phase difference Re2 is more than 5000nm, in the 2 st configuration, by the 1 st configuration of the polyester resin film around its fast axis as the center axis rotation 30 DEG, so that the polyester resin film surface and the measurement direction of the angle of 60 DEG is arranged,

[ Iii ] in the 3 rd configuration of the measurement of the phase difference Re3 is 6000nm above, in the 3 rd configuration, in the 1 st configuration of the polyester resin film in the form of a polyester resin film in the fast axis relative to the 45 degrees of the axis of the rotation of 30 degrees as a center axis, so that the polyester resin film surface and the measurement direction of the angle of 60 degrees form the polyester resin film arrangement,

[ Iv ] in the 4 th arrangement of the measurement of the phase difference Re4 is 7000nm or more, in the 4 th arrangement, the 1 st arrangement of the polyester resin film around its slow axis as the center axis rotation 30 DEG, so that the polyester resin film surface and the measurement direction of the angle of 60 degrees.

2. The polarizing plate according to claim 1, wherein the surface reflectance of the polyester resin film is 5.7% or less.

3. The polarizing plate according to claim 1, wherein the polyester resin film has a film thickness of 60 μm or more.

4. The polarizing plate according to claim 1, wherein the polyester resin film has a ratio of a phase difference value Re1 to a phase difference value Rth in a thickness direction defined by the formula (2) of 0.5 or more,

Rth＝〔(n_x+n_y)/2-n_z〕 ×d (2)

Where n _x denotes a refractive index in a slow axis direction in a film plane, n _y denotes a refractive index in a fast axis direction in a film plane, n _z denotes a refractive index in a film thickness direction, and d denotes a film thickness.

5. The polarizing plate according to claim 1, wherein the absolute value of the variation in the phase difference Rth in the thickness direction before and after the test in which the (meth) acrylic resin film is stored for 360 hours in an environment of 85 ℃ and 85% rh is 10nm or less.

6. The polarizing plate according to claim 1, wherein the (meth) acrylic resin film has a glass transition temperature of 110 ℃ or higher.

7. The polarizing plate according to claim 1, wherein the (meth) acrylic resin film comprises a (meth) acrylic resin component having a ring structure.

8. A polarizing plate with an adhesive layer comprising the polarizing plate according to any one of claims 1 to 7 and an adhesive layer,

9. A liquid crystal display device comprising the polarizing plate with an adhesive layer according to claim 8.