TWI569967B - A polarizing plate and a liquid crystal display device using the same - Google Patents

Description

Polarizing plate and liquid crystal display device using the same

The present invention relates to a polarizing plate and a liquid crystal display device using the same.

The liquid crystal display device needs to be increasingly expanded in applications such as liquid crystal televisions or liquid crystal displays for personal computers. In general, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter or the like is held by a glass plate, and two polarizing plates provided on both sides thereof. The respective polarizing plates are usually composed of two transparent resin films holding polarizers. As an example of such a transparent resin film, a cellulose-deposited film such as cellulose acetate having a function of protecting a polarizer is often used. The deuterated cellulose film has a high transmittance, and is immersed in an aqueous alkali solution to saponify its surface, and is hydrophilized to achieve excellent adhesion to a polarizer.

However, it has been proposed in the past to use a resin film other than a deuterated cellulose film as a protective film for a polarizing plate. For example, Japanese Laid-Open Patent Publication No. 2012-181277 discloses a polarizing plate in which a cellulose-deposited cellulose film having a specified retardation value is disposed on a unit cell side of a polarizer. In the polarizing plate to be formed, the outer resin film is formed by blending a composition of rubber elastomer particles having a predetermined number average particle diameter in a transparent acrylic resin, and is not easily broken even if it is thinned.

Further, Japanese Laid-Open Patent Publication No. 2012-256057 discloses Provided is a polarizing plate which is obtained by using a polyester film formed of polyethylene terephthalate (PET) or the like as a protective film of a polarizing plate, by retarding a film controlled to a specified value It is used in combination with a specific light source, and is excellent in durability and visibility.

The present inventors have placed a deuterated cellulose film as a protective film on the side of one side of a polarizer, and used acrylic acid as disclosed in Japanese Laid-Open Patent Publication No. 2012-181277 or JP-A-2012-256057. A film having a resin or a polyester as a main component was placed on the other side, and a polarizing plate having such a configuration was produced, and the durability was examined. Specifically, the polarizing plate having such a configuration was subjected to a thermal shock endurance test and a high-temperature and high-humidity durability test. As a result, when the configuration disclosed in Japanese Laid-Open Patent Publication No. 2012-181277 or JP-A-2012-256057 is used, light leakage in the in-plane end portion of the polarizing plate or due to a polarizing plate occurs. The problem of warpage of the panel caused by curling.

The present invention has been made in view of the above problems, and the object of the invention is to provide a protective film as an acrylic resin or a polyester. The film of the main component is disposed on the polarizing plate formed on one side of the polarizer. Even after the thermal shock durability test or the high-temperature and high-humidity durability test, the inner end of the polarizing plate may be leaked, or The occurrence of problems such as warpage of the panel due to the curl of the polarizing plate is suppressed to a minimum technical means.

The present inventors have made in-depth research in view of the above problems. It is found that the protective film A, the polarizer and the protective film B are sequentially provided, and the protective film A and the protective film B are in a polarizing plate which is bonded to the polarizer using an ultraviolet curing adhesive. As the protective film A, a film containing an acrylic resin or a polyester as a main component is used, and as the protective film B, a cellulose acetate film containing cellulose acetate as a main component is used, and the cellulose acetate is used. The average acetyl group substitution degree is 2.1 to 2.7, and the difference between the longitudinal and lateral directions of the photoelastic coefficient of the cellulose acetate film (the absolute value of the value obtained by subtracting the value of the TD direction from the value of the MD direction) is controlled. In the case of 5.0 or less, a polarizing plate excellent in durability which can solve the above problems can be realized, and the present invention has been completed.

That is, the above object of the present invention is solved by the following means.

[1] A polarizing plate comprising a protective film A, a polarizer and a protective film B in this order, wherein the protective film A and the protective film B are bonded to the polarizer using an ultraviolet curing adhesive. a polarizing plate characterized in that the protective film A is made of acrylic resin or polyester as a main component The protective film B is a cellulose acetate film containing cellulose acetate as a main component, and the cellulose acetate has an average ethyl thiol substitution degree of 2.1 to 2.7; The difference between the longitudinal and lateral directions of the photoelastic coefficient (23° C. 55% RH) of the ester film (the absolute value of the value obtained by subtracting the value in the TD direction from the value in the MD direction) is 5.0 or less.

[2] The polarizing plate according to the above [1], wherein, in the protective film B, the photoelastic coefficient in the MD direction is larger than the photoelastic coefficient in the TD direction.

[3] The polarizing plate according to the above [1] or [2] wherein the protective film A has a film thickness of 55 to 80 μm.

[4] The polarizing plate according to any one of the above [1], wherein the protective film A has a tensile modulus in the MD direction (23 ° C 55% RH) and a tensile modulus in the TD direction. The absolute value of the difference between (23 ° C and 55% RH) is 500 MPa or less.

[5] The polarizing plate according to any one of the above [1], wherein the protective film A is allowed to stand at 80 ° C and 90% RH for 24 hours, and the haze value is changed at this time. It is 0.5 or less.

[6] The polarizing plate according to any one of the above [1], wherein the protective film A is made of an acrylic resin as a main component.

[7] The polarizing plate according to any one of the above [1], wherein the protective film A is made of polyethylene terephthalate as a main component.

[8] The polarizing plate according to any one of the above [1] to [7] wherein The protective film B contains a hysteresis rising agent containing at least one hysteresis rising agent selected from the group consisting of a pyrazole ring, an imidazole ring, and a triazole ring.

[9] The polarizing plate according to any one of [1] to [8] wherein the cellulose acetate of the protective film B has a degree of substitution of the ethyl thiol group of 2.5 to 2.7.

[10] The polarizing plate according to any one of the above [1], wherein the ultraviolet curable adhesive is a mixture of an alicyclic epoxy compound and an aliphatic chain epoxy compound.

[11] A VA liquid crystal display device comprising the polarizing plate according to any one of [1] to [10] above.

1‧‧‧Solution kettle

3, 6, 12, 15 ‧ ‧ filters

4, 13 ‧ ‧ storage tank

5, 14‧‧‧ liquid pump

8, 16‧‧‧ catheter

10‧‧‧ UV absorbers into the kettle

20‧‧‧Conduit tube

21‧‧‧Mixer

30‧‧‧Pressure mould

31‧‧‧Metal strip

32‧‧‧thin strip

33‧‧‧ peeling position

34‧‧‧Zoom extension

35‧‧‧Drying device

41‧‧‧Into the kettle

42‧‧‧ Stock silo

43‧‧‧ pump

44‧‧‧Filter

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

Fig. 2 is a view showing an example of a dope preparation step, a casting step, and a drying step (solvent evaporation step) of a preferred solution casting film forming method of the present invention.

[Best Mode for Carrying Out the Invention]

The polarizing plate according to the present invention has a protective film A, a polarizer and a protective film B in this order, and the protective film A and the protective film B are bonded to the polarizer using an ultraviolet curing adhesive. A polarizing plate. Here, the protective film A is a film containing an acrylic resin or a polyester as a main component; the protective film B is a cellulose acetate film containing cellulose acetate as a main component, and the cellulose acetate is used. The average ethyl thiol substitution of the ester is from 2.1 to 2.7. Then, the difference between the longitudinal and lateral directions of the photoelastic coefficient of the cellulose acetate film (the absolute value of the value obtained by subtracting the value in the TD direction from the value in the MD direction) is 5.0 or less. According to the present invention, even if the protective film is a polarizing plate in which a film containing acrylic resin or polyester as a main component is disposed on one side of a polarizer, thermal shock durability test or high temperature and high humidity durability is obtained. After the test, the occurrence of problems such as light leakage at the inner end portion of the polarizing plate or warpage of the panel due to curling of the polarizing plate can be minimized.

With regard to the above configuration defined by the present invention, As a technical reason for the efficacy of the object of the present invention, the detailed mechanism has not been fully elucidated, but the following mechanism is presumed. That is, first, regarding the problem caused by the thermal shock durability test, when a polyester film such as an acrylic resin film or a polyethylene terephthalate film is used as the protective film A, in view of the acrylic resin The value of Tg (about 100 ° C), polyester Tg (PET is about 70 ° C), when exposed to high temperature - low temperature cycle, the film will become repeatedly softened - hardened, and stress is generated in the plane. Then, it is considered to be caused by the difference in stress between the cellulose ester film used as the protective film B, and light leakage from the warpage or optical deformation of the panel occurs. On the other hand, according to the configuration of the present invention, the stress generated in the plane can be relaxed, and as a result, it is estimated that the occurrence of warpage or light leakage of the panel after the thermal shock durability test can be reduced.

Also, regarding the high temperature and high humidity durability test In the case where a cellulose film such as an acrylic resin film or a polyethylene terephthalate film which is less permeable to water (less moisture permeability) is used as the protective film A, it penetrates into the liquid crystal. The moisture of the protective film B (cellulose ester film) on the cell side is not easily released to the outside of the film by the protective film A having a small moisture permeability, and the cellulose ester constituting the cellulose ester film is decomposed, which is considered to be due to this. Light leakage from the warpage or optical deformation of the panel occurs. (In this regard, as a constituent of the protective film B, cellulose acetate having an average substitution ratio of 2.1 to 2.7 is used as a main component. This problem is more pronounced when the cellulose acetate film is used. On the other hand, in the configuration of the present invention, the optical deformation is reduced as compared with the conventional configuration, and even if the decomposition of the cellulose ester occurs, it is considered that the deterioration of the visibility of the display device is not deteriorated. . Further, the photoelastic anisotropy of optical deformation is small, and it is considered that physical deformation is not easily caused. As a result, it is presumed that the occurrence of warpage or light leakage of the panel after the thermal shock durability test can be reduced.

Hereinafter, the present invention and the constituent elements, and The form of the invention will be described in detail. In addition, the "~" shown in the present invention is used in the sense that the numerical values described before and after are included as the lower limit and the upper limit.

Polarizer

Hereinafter, each constituent element of the polarizing plate of the present invention will be described in detail.

[Composition of polarizing plate]

The polarizing plate of the present invention has a protective film A, a polarizer and a protective film B in this order, and the protective film A is a film mainly composed of an acrylic resin or a polyester (for example, polyethylene terephthalate), and is protected. Film B is a cellulose acetate film having a specified average acetylation degree of substitution.

1 is a view showing an example of the configuration of a polarizing plate of the present invention. A schematic cross-sectional view. In Fig. 1, the polarizing plate 101 of the present invention has a protective film A (an acrylic film, a PET film or the like polyester film) 102 and a polarizer 104 from the surface side, and the protective film A102 and the polarizer 104 are borrowed. This is followed by the ultraviolet curable adhesive layer 103A. The ultraviolet curable adhesive layer 103A is made of a material that is cured by irradiation with ultraviolet rays or the like. Further, the details of the ultraviolet curable adhesive are as described later.

The polarizing plate 101 shown in FIG. 1 is further protected with configuration The surface of the film A102 is the surface of the polarizer 104 on the opposite side, and the protective film B (cellulose acetate film) 105 is laminated by interposing the ultraviolet curable adhesive layer 103B.

Also, although not shown in Figure 1, it can be used as needed. The outer side (the outermost surface portion) of the protective film A102 is provided with, for example, an antiglare layer, an antireflection layer, an antifouling layer, a hard coat layer, or the like.

[Protective film A]

The protective film A is thin with acrylic resin or polyester as a main component membrane.

In the present invention, the so-called film is "as a specified component" The main component means that the ratio of the predetermined component is more than 50% by mass, preferably 55% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass of the total mass of the resin component constituting the film. More than %, particularly preferably 90% by mass or more.

[Acrylic]

The acrylic resin according to the present invention also contains a methacrylic resin, preferably a derivative of an acrylate/methacrylate, and particularly preferably a (co)polymer of an acrylate ester/methacrylate ester. The acrylic resin is not particularly limited, but an acrylic resin composed of 51 to 99% by mass of methyl methacrylate unit and 1 to 50% by mass of a monomer unit of another acrylic resin copolymerizable therewith can be obtained. A preferred optical film is preferred.

In the acrylic resin related to the present invention, as a methyl group Other monomers of the acrylic resin copolymerized with methyl acrylate unit, for example, an alkyl methacrylate having an alkyl group having 2 to 18 carbon atoms, an alkyl group having an alkyl group having 1 to 18 carbon atoms, or acrylic acid An aromatic group such as an unsaturated group-containing divalent carboxylic acid such as α,β-unsaturated acid such as methacrylic acid, maleic acid, fumaric acid or itaconic acid, styrene or α-methylstyrene Alpha, β-unsaturated nitrile such as vinyl compound, acrylonitrile or methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, etc., which can be used alone Or use two or more kinds of monomers together as a copolymerization component. use.

Among these, the thermal decomposition resistance or fluidity of the copolymer From the viewpoints, preferred are methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, etc., particularly preferably methyl acrylate or N-butyl acrylate.

As can be formed even in high temperature, high humidity environment The acrylic resin which can change the optical film which is small and has high transparency, and the copolymerization component is preferably an alicyclic alkyl group or an acrylic acid which forms a cyclic structure in the molecular main chain by intramolecular cyclization. Resin. Examples of the acrylic resin which forms a cyclic structure in the molecular main chain include an acrylic thermoplastic resin described in paragraphs [0026] to [0027] of JP-A-2012-133078, which contains a lactone-containing resin. A polymer of a ring; a preferred resin composition or a synthesis method, for example, described in JP-A-2012-066538 and JP-A-2006-171464. Moreover, as another preferable aspect, for example, a resin containing glutaric anhydride as a copolymerization component is described in the copolymerization component or a specific synthesis method, for example, JP-A-2004-070296.

In the present invention, the surface of the so-called formed film is excellent. From the viewpoint of the weight, the weight average molecular weight (Mw) of the acrylic resin to which the present invention is applied is preferably 80,000 or more. Further, from the viewpoint of further improving the film surface shape at the time of lamination, the weight average molecular weight of the acrylic resin is preferably in the range of 100,000 to 4,000,000.

The upper limit of the weight average molecular weight of the acrylic resin The viscosity does not become too high and can maintain the solution casting adaptability. In the case of ensuring compatibility with an organic solvent or an additive at the time of preparation of a dope, the upper limit is preferably set to 4,000,000.

The weight average molecular weight of the acrylic resin according to the present invention can be measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

Solvent: tetrahydrofuran

Pipe column: Shodex K806, K805, K803G (Showa Denko (share) system, used in 3 connections)

Column temperature: 25 ° C

Sample concentration: 0.1% by mass

Detector: RI Model 504 (manufactured by GL SCIENCE)

Pump: L6000 (Hitachi Manufacturing Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: A calibration curve made using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 500 to 2800000. 13 samples are preferably used at almost equal intervals.

The method for producing the acrylic resin is not particularly limited, and a conventional method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization can be used.

Further, in the present invention, a commercially available one may be used as the acrylic resin according to the present invention. For example, DERPET 60N, 80N (above is made by Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (above is Mitsubishi Rayon) (share) system, KT75 (Denki Kagaku Kogyo (share) system), etc. The acrylic resin of such a commercial product may be used in combination of two or more kinds.

(Other thermoplastic resins that can be used together with acrylic resin)

In the present invention, when the protective film A is made of an acrylic resin as a main component, it is possible to maintain the "acrylic layer containing an acrylic resin as a main component" within a range not exceeding the content of the acrylic resin according to the present invention. Further, other thermoplastic resins may be further included within the range not impairing the effects of the object of the present invention.

The thermoplastic resin has a glass transition temperature of 100 ° C or higher and a total light transmittance of 85% or more. When the acrylic resin according to the present invention is mixed and brought into a film form, heat resistance or mechanical strength is improved. The point is preferred.

Examples of the other thermoplastic resin include olefin-based polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly(4-methyl-1-pentene); polystyrene and styrene-methacrylic acid; a styrene polymer such as a methyl ester copolymer, a styrene-acrylonitrile copolymer, or an acrylonitrile-butadiene-styrene block copolymer; and an ABS resin prepared with a polybutadiene rubber or an acrylic rubber ( A rubbery polymer such as acrylonitrile-butadiene-styrene resin or ASA resin (acrylonitrile-styrene-acrylate resin). The rubbery polymer preferably has a graft portion having a composition compatible with the cyclic polymer on the surface, and the average particle diameter of the rubbery polymer is improved from the viewpoint of improving the transparency at the time of film formation. It is preferably 100 nm or less, more preferably 70 nm or less.

Used as other thermoplastic resins to use with acrylic trees The resin is preferably a thermodynamically compatible resin. As such other thermoplastic resin, for example, an acrylonitrile-styrene copolymer or a polyvinyl chloride resin having a vinyl cyanide monomer unit and an aromatic vinyl monomer unit is preferable. Among these, the acrylonitrile-styrene copolymer is easy to obtain an optical fiber having a glass transition temperature of 120 ° C or higher, a phase difference of 100 μm in the plane direction of less than 10 nm, and a total light transmittance of 85% or more. A film is preferred.

As an acrylonitrile-styrene copolymer, specifically, suitable The copolymerization ratio is in the range of 1:10 to 10:1 in terms of molar units.

The composition of the acrylic resin that can be used for this purpose is It is preferable to contain an aliphatic (meth) acrylate monomer, a (meth) acrylate monomer having an aromatic ring, or a (meth) acrylate monomer having a cyclohexyl group.

The constituent mass ratio of the components is preferably an acrylic tree 40 to 100% by mass in the fat, more preferably 60 to 100% by mass, most preferably 70 to 100% by mass.

As an aliphatic (meth) acrylate monomer, it can be listed For example, methyl acrylate, ethyl acrylate, (i-, n-) propyl acrylate, butyl (n-, i-, s-, t-) acrylate, acrylic acid (n-, i-, s-) pentane Ester, (n-, i-) hexyl acrylate, (n-, i-) heptyl acrylate, (n-, i-) octyl acrylate, (n-, i-) decyl acrylate, acrylic acid (n- , i-) tetradecyl ester, (2-ethylhexyl) acrylate, acrylic acid (ε-caprolactone), (2-hydroxyethyl) acrylate, acrylic acid (2- Hydroxypropyl) ester, (3-hydroxypropyl) acrylate, (4-hydroxybutyl) acrylate, (2-hydroxybutyl) acrylate, (2-methoxyethyl) acrylate, acrylic acid ( 2-ethoxyethyl) ester or the like, or the above acrylate is changed to methacrylate. Preferred among them are methyl methacrylate, ethyl methacrylate, (i-, n-) propyl methacrylate, butyl methacrylate (n-, i-, s-, t-), acrylic acid Methyl ester, ethyl acrylate.

As a (meth) acrylate single with an aromatic ring As the body, for example, benzyl acrylate, benzyl methacrylate, phenylethyl acrylate, phenylethyl methacrylate or the like can be used.

As a (meth) acrylate monomer having a cyclohexyl group, For example, cyclohexyl acrylate and cyclohexyl methacrylate can be used.

In addition to the above monomers, as a further copolymerizable For example, an unsaturated group-containing divalent carboxylic acid such as α,β-unsaturated acid such as acrylic acid or methacrylic acid, maleic acid, fumaric acid or itaconic acid, styrene or α-methylbenzene An aromatic vinyl compound such as ethylene, an α,β-unsaturated nitrile such as acrylonitrile or methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, or the like. These may be used singly or in combination of two or more kinds of monomers as a copolymerization component.

In order to synthesize an acrylic resin, in the usual polymerization, The control of the sub-quantity is difficult. As a polymerization method of such a low molecular weight polymer, for example, a method of using a peroxide polymerization initiator such as cumene hydroperoxide or t-butyl hydrogen peroxide; a larger amount than usual polymerization a method of polymerizing a starter; using a thiol group in addition to a polymerization initiator a method of a chain transfer agent such as a compound or carbon tetrachloride; a method of using a polymerization terminator such as benzoquinone or dinitrobenzene in addition to a polymerization initiator; and, for example, Japanese Patent Laid-Open No. 2000-128911 or Japan JP-A-2000-344823 discloses a compound having a thiol group and a hydroxy group, or a method in which a block polymerization is carried out using a polymerization catalyst having the compound and an organometallic compound, and the like. Good user, but especially the method described in this bulletin.

[Rubber particles]

When the protective film A according to the present invention has an acrylic resin as a main component, the protective film A preferably contains rubber particles. The rubber particles which can be suitably used in the present invention are not particularly limited, but are preferably acrylic rubber particles. As the acrylic rubber particles, an acrylic monomer containing butyl acrylate or an alkyl acrylate such as 2-ethylhexyl acrylate as a main component is polymerized in the presence of a polyfunctional monomer to have rubber elasticity. particle.

Acrylic rubber particles can be made of rubber bombs like this The particles of the nature may be formed of a single layer, or may be a multilayer structure having at least one rubber elastic layer. The acrylic rubber particles having a multilayer structure include, for example, a rubber-elastic particle as a core and a hard methacrylic acid alkyl ester polymer coating thereon; and a hard methacrylic acid alkane; The base ester-based polymer is used as a core, and the periphery thereof is coated with the above-mentioned rubber-elastic acrylic polymer; or the periphery of the hard core is coated with a rubber-elastic acrylic polymer, and further The periphery is covered with a hard alkyl methacrylate polymer. In such rubber particles, the average diameter of the particles formed of the elastic layer is usually in the range of about 50 to 400 nm.

Rubber particles in the protective film A related to the present invention The content is usually in the range of 5 to 50 parts by mass per 100 parts by mass of the acrylic resin. Since the acrylic resin and the acrylic rubber particles are commercially available in a state of being mixed, the commercially available product can be used. An example of a commercially available product of a (meth)acrylic resin in which acrylic rubber particles are blended is, for example, OROGRLAS DR which is conventionally sold by Sumitomo Chemical-Haas (now), and is now sold by Sumitomo Chemical Co., Ltd. HT 55X or Technolloy S001, etc.

[Polyester]

The specific constitution of the other candidate polyester which protects the constituent components of the film A is not particularly limited.

As the polyester constituting the polyester film, polyparaphenylene can be used. Ethylene formate or polyethylene naphthalate, but other copolymerization components may also be included. These resins are excellent in transparency and excellent in thermal properties and mechanical properties, and can easily control hysteresis by stretching processing. In particular, polyethylene terephthalate has a large intrinsic birefringence, and even if the film thickness is thin, it is relatively easy to obtain a large hysteresis, so it is the most suitable material.

Further, in the present invention, the hysteresis value of the protective film A can be measured Determine the refractive index and thickness of the biaxial direction, or use it A commercially available automatic birefringence measuring device of KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.) was obtained.

Protective film A with polyester as its main component, can follow one A general method for producing a polyester film is produced. For example, the molten polyester resin is extruded into a sheet shape, and is stretched in the longitudinal direction by the speed difference of the roll at a temperature higher than the glass transition temperature of the formed unaligned polyester. The direction is extended and the heat treatment is applied.

The polyester film of the present invention may be a uniaxially stretched film or a biaxially stretched film. When a biaxially stretched film is used as the polarizer protective film, no rainbow is observed even when viewed from directly above the film face. The color spots, but it is necessary to pay attention to the fact that rainbow-like spots are observed when viewed from an oblique direction. The reason for this phenomenon is that since the biaxially stretched film is formed of a refractive index ellipsoid having a different refractive index in the traveling direction, the width direction, and the thickness direction, there is a hysteresis of zero according to the light transmission direction inside the film ( The direction in which the refractive index ellipsoid appears to be a perfect circle. Therefore, when the liquid crystal display screen is viewed from a specific direction in the oblique direction, there is a case where the hysteresis is zero, and a rainbow-like color spot is formed concentrically around the point. Then, when the angle from the position directly above the film surface (the normal direction) to the position where the rainbow-like color spot can be seen is θ , the larger the angle of the birefringence in the film surface, the larger the angle θ , the rainbow The more visible spots will become harder to see. In the biaxially stretched film, since the angle θ tends to be small, it is preferable that the uniaxially stretched film becomes difficult to see a rainbow-like color spot.

[Preferred physical properties of protective film A]

In the protective film A, the light transmittance of light having a wavelength of 380 nm is preferably 20% or less for the purpose of suppressing deterioration of an optical functional dye such as an iodine dye. The light transmittance is preferably 15% or less, more preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of the optical functional pigment due to ultraviolet rays can be suppressed. Further, the transmittance in the present invention is measured by a vertical method for the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

Here, in order to make the above light transmittance of the protective film A It is preferably 20% or less, and it is preferable to appropriately adjust the type, concentration, and thickness of the ultraviolet absorber. The ultraviolet absorber used in the present invention is a conventional one. The ultraviolet absorber is, for example, an organic ultraviolet absorber and an inorganic ultraviolet absorber, and is preferably an organic ultraviolet absorber from the viewpoint of transparency. When two or more types of ultraviolet absorbers are used in combination, ultraviolet rays of respective wavelengths can be simultaneously absorbed, so that the ultraviolet absorption effect can be further improved.

Still, among the ultraviolet absorbers, the molecular weight is 400 or more. The ultraviolet absorber is not easily volatilized because it is difficult to sublimate or has a high boiling point, and is not easily scattered even when the film is dried at a high temperature, and is preferable from the viewpoint of effectively improving the weather resistance with a relatively small amount of addition.

As a UV absorber having a molecular weight of 400 or more, For example, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2-benzotriazole, 2,2-methylenebis[4-(1, 1,3,3-tetrabutyl)-6-(2H-benzo a benzotriazole system such as triazol-2-yl)phenol, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2, A hindered amine system such as 6,6-pentamethyl-4-piperidinyl sebacate may be used in combination of two or more kinds.

As such ultraviolet absorbers, commercially available products can be used. For example, Tinuvin series of Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 928, etc., manufactured by BASF Japan Co., Ltd. can be used.

The above ultraviolet absorber may be used alone or in combination 2 More than one kind.

Moreover, in order to make the adhesion to the polarizer good, The protective film A can be subjected to corona treatment, coating treatment, flame treatment, or the like.

Further, the film thickness of the protective film A is not particularly limited, and is preferably 40 to 100 μm, preferably 55 to 80 μm. When the film thickness of the protective film A is within such a range, it is particularly preferable from the viewpoint of suppressing the warpage (curl) of the panel after the thermal shock durability test or the high-temperature high-humidity durability test. Further, in particular, when the protective film A is made of an acrylic resin as a main component, it is preferable to suppress the occurrence of light leakage due to the transmission of the protective film A with only a small amount of water. Thick rules.

Tensile modulus of the protective film A in the MD direction (23 ° C The absolute value of the difference between the tensile elastic modulus (23 ° C and 55% RH) of 55% RH) and the TD direction is preferably 500 MPa or less, more preferably 300 MPa or less, still more preferably 200 MPa or less. By being configured in such a way, it is possible to protect The MD direction of the film A and the TD direction take a value close to the tensile modulus, and have the advantage that it is not easy to cause curling. Further, in the present invention, cellulose acetate having a specified average acetylation degree of substitution is used as a main component of the protective film B, and as a protective film A opposed to the protective film B having such a configuration, as described above. In the case where the tensile modulus of elasticity has a value close to the TD direction in the MD direction, it is preferable to say that the occurrence of curl is surely suppressed. In addition, the absolute value of the tensile modulus of the protective film A is not particularly limited. However, when the protective film A has an acrylic resin as a main component, the tensile modulus in the MD direction is preferably 1,500 to 4,000 MPa, and more preferably 2,000. ~3000MPa. Further, the tensile modulus in the TD direction is preferably from 1,500 to 5,000 MPa, and more preferably from 2,000 to 4,000 MPa. On the other hand, when the protective film A is made of polyester as a main component, the tensile modulus in the MD direction is preferably from 3,000 to 8,000 MPa, and more preferably from 5,000 to 7,500 MPa. Further, the tensile modulus in the TD direction is preferably 1,500 to 8,000 MPa, and more preferably 2,000 to 7,000 MPa. In addition, the value of the tensile modulus of the protective film A is defined by the measurement method described in the column of the examples to be described later, using the measured values.

Furthermore, the protective film A is subjected to high temperature and high humidity conditions (80 ° C). The condition of 90% RH was allowed to stand for 24 hours, and the change in haze value (rise portion) at this time was preferably 0.5 or less. The change (rise) of the haze value under such conditions is dependent on the tiny foreign matter present in the film. When the film contains most of the micro foreign matter, when placed under high temperature conditions and/or high humidity conditions, the foreign matter is Cracks (cracks) are generated between the polymers, and the cracks are marked as a change in haze. Again, the change in haze is In the case of a large film, the balance of the strength of the film is deteriorated due to the occurrence of cracks, and the balance of the polarizing plate is deteriorated, causing warpage (curl) of the panel. In other words, the above-mentioned regulation can be said to be an evaluation of the "durability of high-temperature and high-humidity conditions" which cannot be observed with respect to the absolute value measured by the simple haze. The value of the haze (and the change (rising portion)) of the protective film A is defined by the measurement method described in the column of the examples to be described later, using the measured values.

In order to get a better composition (so-called as above) The protective film A of the MD-TD of the tensile modulus or the change of the haze value under high temperature and high humidity conditions, preferably the film forming material (ie, acrylic resin or polyester) of the film is melted. The state is filtered. By applying such a treatment, the polymer component (block) contained in the raw material resin can be removed, and the molecular weight distribution of the raw material resin can be made sharper. In addition, the specific means of the filtration treatment is not particularly limited, and the filtration treatment may be carried out by using a filter medium such as a conventional stainless steel sintered body. Here, the filter particle size (initial filtration efficiency: 95%) of the filter medium is preferably 25 μm or less, and more preferably 10 μm or less.

After that, the raw material resin that has been subjected to the filtration treatment is reacted It is required to be mixed with an additive such as an ultraviolet absorber and put into an extruder, and then melted, extruded in a T-die, and adhered to a cooling roll to obtain an unstretched sheet. The unstretched sheet extends in the MD direction in response to the desired extension between the rolls having the speed difference (roll extension), and further, by the need to hold the clip and extend the extension (pull) Width extension Stretching, or extension (inflated extension) extended by air pressure, etc., also extends in the TD direction, and finally is treated in a biaxial alignment.

Here, first, when performing the longitudinal extension step of the first segment, It extends between two or more rolls of different circumferential speeds. The stretching ratio (longitudinal stretching ratio) at this time is preferably 1.00 to 1.20 times, more preferably 1.01 to 1.10 times, and particularly preferably 1.01 to 1.05 times when rubber particles are used as a main component and rubber particles are added. . When rubber particles are not added, it is preferably 1.10 to 1.60 times, more preferably 1.15 to 1.40 times, and particularly preferably 1.2 to 1.35 times. Further, in the case where polyester is used as the main component, it is preferably 2 to 5 times, more preferably 3 to 5 times, and particularly preferably 3 to 4 times. As the heating means at this time, a method of heating a roll or a method of a non-contact heating method may be used, or these may be used in combination. Among them, as an optimum stretching method, for example, a method in which roll heating and non-contact heating are used in combination. In this case, the film is first prepared to be heated to a so-called relatively high temperature of 120 to 150 ° C, which is important from the viewpoint of increasing the modulus of elasticity of the protective film A. Thereafter, the film is heated by an infrared heater to be introduced into a lateral stretching step to be described later. Further, the importance of this preliminary heating is equally applicable even in the case where the lateral stretching step is first performed and then the vertical stretching step is carried out. Further, the extension temperature of the longitudinal stretching step is preferably from 90 to 180 ° C, more preferably from 100 to 180 ° C.

Next, the uniaxially stretched film obtained in such a manner It is introduced into the tenter and can be extended in the width direction as needed. In the case of the acrylic resin as a main component, the stretching ratio (transverse stretching ratio) at this time is preferably 1.00 to 1.20 times, more preferably 1.01 to 1.10 times, and particularly preferably 1.01~1.05 times. When rubber particles are not added, it is preferably 1.00 to 1.50 times, more preferably 1.05 to 1.40 times, and particularly preferably 1.1 to 1.2 times. Further, in the case where polyester is used as the main component, it is preferably 1 to 5 times, more preferably 2 to 5 times, more preferably 2 to 4 times, and particularly preferably 3 to 4 times. Further, the stretching temperature of the lateral stretching step is preferably from 90 to 180 ° C, more preferably from 100 to 150 ° C. For the biaxially stretched film obtained in such a manner, heat treatment is applied as needed. The heat treatment is preferably carried out in the tentering, and it is preferably carried out in the range of the melting point of the raw material resin of from Tm to 50 ° C to Tm.

As a method of blending the ultraviolet absorber to the protective film A The method can be carried out by a combination of conventional methods, and the dried ultraviolet absorber can be blended with the polymer raw material by, for example, a kneading extruder in advance to prepare a masterbatch for film formation. The method of mixing the specified master batch and the polymer raw material is carried out.

At this time, the concentration of the ultraviolet absorber of the masterbatch is ultraviolet The absorbent is uniformly dispersed and economically formulated, and preferably has a concentration of 5 to 30% by mass. As a condition for preparing the master batch, a kneading extruder is preferably used, and the extrusion temperature is extruded at a temperature equal to or higher than the melting point of the polyester raw material and at a temperature of 290 ° C or lower for 1 to 15 minutes. When the temperature is above 290 ° C, the amount of reduction of the ultraviolet absorber is large, and the viscosity of the master batch is lowered. When the extrusion temperature is a melting point of -50 ° C or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color tone adjuster, and an antistatic agent may be added as needed.

The protective film A can also be made into a multilayer of at least three layers or more. The structure is such that an ultraviolet absorber is added to the intermediate layer of the film. The intermediate layer is a three-layer structure film containing a UV absorber, specifically, the following Make it all. The pellets of the raw material resin for the outer layer are separately mixed with the masterbatch containing the ultraviolet absorber and the raw material resin as the intermediate layer, and dried in a predetermined ratio, and then supplied to a conventional melt laminating extruder. The slit-shaped mold was extruded into a sheet shape, and cooled and solidified on a casting roll to produce an unstretched film. That is, a film layer constituting the two outer layers and a film constituting the intermediate layer may be laminated using two or more extruders, three-layer manifolds, or a bus bar (for example, a bus bar having a square bus portion). In the layer, a three-layered sheet was extruded from a metal nozzle and cooled by a casting roll to produce an unstretched film.

[Protective film B]

The protective film B is a cellulose acetate film containing cellulose acetate as a main component. As a specific form of the cellulose acetate film, in addition to the average acetyl group substitution degree and the photoelastic coefficient, which have a predetermined configuration, conventionally known knowledge can be appropriately referred to.

Specifically, it is used in the protection of the polarizing plate related to the present invention. The protective film B, which is a cellulose acetate having a main component, is characterized by a degree of substitution of the average ethyl thiol group of 2.1 to 2.7, more preferably an average degree of substitution of an ethyl ketone group of 2.5 to 2.7. When the average degree of substitution of the cellulose acetate is less than 2.1, the cellulose acetate is easily decomposed by the influence of moisture, and as a result, there is a problem that the problem of the present invention cannot be sufficiently solved. Further, when the average degree of substitution of the cellulose acetate exceeds 2.7, the haze and durability are deteriorated, and the problem of the present invention cannot be sufficiently solved.

Further, a protective film for a polarizing plate related to the present invention B, the cellulose acetate film constituting the film is a difference between the longitudinal and lateral directions of the photoelastic coefficient (23 ° C 55% RH) (the absolute value of the value obtained by subtracting the value of the TD direction from the value of the MD direction) It is characterized by 5.0 or less, and is preferably 3.0 or less, more preferably 2.5 or less. The present inventors have found that as a cellulose ester film, by using cellulose acetate having the above-described specified average acetylation degree, the difference in the longitudinal and lateral directions of the photoelastic coefficient of the cellulose acetate film is controlled to be In the polarizing plate in which the protective film A as described above is disposed on one side of the polarizer, the polarizing plate can be used even after the thermal shock durability test or the high-temperature and high-humidity durability test. The occurrence of problems such as light leakage at the inner end portion of the surface or warpage of the panel due to curling of the polarizing plate is suppressed to a minimum. Further, the value of the photoelastic coefficient of the cellulose acetate film is defined by the measurement method described in the column of the examples to be described later, using the measured values.

(cellulose acetate)

The protective film B used in the polarizing plate according to the present invention, the cellulose acetate of which is the main component, is characterized by the degree of substitution of the average ethyl thiol group of 2.1 to 2.7, and the degree of substitution of the cellulose acetate. It can be determined by the method specified in ASTM-D817-96.

As long as the average degree of substitution of ethyl thiol is sufficient to meet the above requirements, In order to obtain desired optical characteristics, cellulose acetate having a different degree of substitution may be mixed and used. The mixing ratio of the different cellulose acetate is not particularly limited.

In order to increase the mechanical strength of the obtained film, the number average molecular weight of the cellulose acetate is preferably in the range of 4 × 10 ⁴ to 3 × 10 ⁵ , and more preferably in the range of 4.5 × 10 ⁴ to 2 × 10 ⁵ . , particularly preferably in the range of 5 × 10 ⁴ ~ 7 × 10 ⁴ . In the present specification, "weight average molecular weight (Mw)" and "number average molecular weight (Mn)" are values measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

[Chemical 1]

(GPC measurement conditions)

Solvent: dichloromethane

Pipe column: Shodex K806, K805, K803G (Showa Denko)

System, used in 3 connections)

Column temperature: 25 ° C

Sample concentration: 0.1% by mass

Detector: RI Model 504 (manufactured by GL SCIENCE)

Pump: L6000 (Hitachi Manufacturing Co., Ltd.)

Flow rate: 1.0ml/min

Calibration curve: using standard polystyrene STK standard polystyrene (east

Cao (share) system) Mw=1000000~500 up to 13 samples made

Calibration curve. 13 samples were used at almost equal intervals.

The content of residual sulfuric acid in the cellulose acetate is preferably in the range of 0.1 to 45 ppm by weight, and preferably in the range of 1 to 30 ppm by weight in terms of sulfur element. The sulfuric acid system is considered to remain in the film in the form of a salt. When the content of the residual sulfuric acid exceeds 45 ppm by weight, when slicing is performed at the time of the heat-stretching film or after the heat stretching, Easy to break. The content of residual sulfuric acid can be determined by the method specified in ASTM D817-96.

In cellulose acetate, the free acid content is preferably from 1 to 500. In the range of ppm by weight, it is preferably in the range of 1 to 100 ppm by weight, more preferably 1 to 70 ppm by weight. When the content of the free acid is in the above range, in the same manner as described above, when the film is cut at the time of the heat-stretching film or after the heat stretching, it is not easily broken. The content of the free acid can be determined by the method specified in ASTM D817-96.

The content of iron (Fe) component in cellulose acetate, It is preferably 3 ppm by weight or less, more preferably 1 ppm by weight or less. Further, the content of the calcium (Ca) component in the cellulose derivative is preferably 60 ppm by weight or less, and more preferably 0 to 30 ppm by weight. The content of the magnesium (Mg) component in the cellulose acetate is preferably in the range of 0 to 70 ppm by weight, particularly preferably in the range of 0 to 20 ppm by weight.

The above cellulose B with the specified average thiol substitution degree The acid ester can be produced by a conventional method, and specifically, it can be synthesized by referring to the method described in JP-A-10-45804. Further, as the cellulose acetate, a commercially available product can also be used.

(hysteresis riser)

The cellulose acetate film as the protective film B preferably contains a hysteresis rising agent. The term "hysteresis riser" means an additive having a function of increasing the hysteresis of the cellulose acetate film by the addition. The specific form of the hysteresis rising agent is not particularly limited and may be appropriately referred to. Previously known insights.

Here, as a preferred form of the retardation increasing agent, examples are given. A compound of the following formula (1) (hereinafter also referred to as "compound (I)"). However, it is of course also possible to use other hysteresis risers. The compound of the following formula (1) is characterized in that the hysteresis value in the thickness direction of the cellulose acetate film can be increased, and the moisture permeability of the film can be lowered. Further, the compound of the following formula (1) has a low volatility even under high temperature and high humidity. Therefore, the cellulose acetate film can also be improved in the bleeding resistance, and as a result, the sharpness of the image can be improved.

In the above formula (1), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a halogen atom. Here, R ¹ to R ⁴ may be the same or different, respectively. The alkyl group having 1 to 3 carbon atoms has a methyl group, an ethyl group, a propyl group and an isopropyl group. Among them, a hydrogen atom, a methyl group, an ethyl group, and a fluorine atom are preferred from the viewpoints of an effect of increasing the hysteresis value (specifically, a hysteresis value in the thickness direction of the film), compatibility with cellulose acetate, and the like. Chlorine atom, particularly preferably methyl.

In the above formula (1), X is independently shown as -O- or -O-C(=O)-. Here, when X is represented by -O-C(=O)-, the ether oxygen (-O-) of -O-C(=O)- becomes a phenyl skeleton bonded to the formula (1). Among them, X is more Good for -O-.

In the above formula (1), R ⁵ and R ⁶ each independently have the following definitions.

When X is -O-, R ⁵ and R ⁶ are each independently shown to be an alkyl group which may be substituted with a hydroxyl group, an ester group or a substituted aromatic group; or a glycidyl group.

Further, when X is -OC(=O)-, R ⁵ and R ⁶ are each independently shown as an alkyl group which may be substituted with a hydroxyl group, an ester group or a substituted aromatic group; or a substituted aromatic group; .

The above ester group of the substitutable alkyl group is of the formula: -O-C(=O)-R or -C(=O)-O-R represents, in this case, R is a linear or branched alkyl or aromatic group having 1 to 8 carbon atoms. The above alkyl group and aromatic group are the same as defined below.

The alkyl group of R ⁵ and R ⁶ is not particularly limited, and is preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, A linear or branched alkyl group having 1 to 8 carbon atoms such as isopentyl, neopentyl, hexyl, heptyl or octyl. Among these, an alkyl group having 1 to 5 carbon atoms is preferred, and an alkyl group having 2 to 4 carbon atoms is preferred.

The aromatic group may be an aryl group having 6 to 24 carbon atoms. More The term is exemplified by phenyl, p-tolyl, naphthyl, biphenyl, anthracenyl, fluorenyl, fluorenyl, fluorenyl, fluorenyl, terphenyl, phenanthryl and the like. Among these, a phenyl group, a naphthyl group, and a phenyl group are preferable. Further, the above aromatic group may have a substituent. Here, the substituent of the substitutable aromatic group is not particularly limited, and examples thereof include an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a phenyl group, a methylphenyl group, and a phenylphenyl group. Methylphenylphenyl, cyano, halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), nitro group, and the like. Further, the substituent may be one or two or more, and in the latter case, each substituent may be the same or different. Among these, the aromatic group is preferably a phenyl group or a methylbenzene from the viewpoints of an improvement effect of a hysteresis value (specifically, a hysteresis value in the thickness direction of the film), compatibility with cellulose acetate, and the like. Base, methylphenylphenyl.

Among these, R ⁵ and R ^{6 are} preferably an alkyl group having a hydroxyl group and an ester group as a substituent or a glycidyl group. At this time, it is preferable that X is -O-. In addition, as a compound of the formula (1), the compound described in JP-A-2011-140637 and JP-A-2011-116912 is included in the compound of the formula (1). Further, a part of the compound described in JP-A-2006-45468 is further contained in the compound of the formula (1). More specifically, as a further preferred example of the compound of the formula (1), for example, the following. Further, the compound is specified by the following number. That is, the compound of the following (1-1) is also referred to as "compound (1-1)".

The content of the compound of the formula (1) in the protective film B Not particularly limited. The content of the compound of the formula (1) is, for example, preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, particularly preferably 5 to 10 parts by mass based on 100 parts by mass of the cellulose acetate. Share. As long as such an amount, the phase difference function and tear strength of the protective film B can be improved. Further, since the volatility under high temperature and high humidity is lowered, the bleeding resistance of the protective film B can be improved, and the sharpness of the image can be improved.

Further, as a compound of the above formula (1) The addition method may be added to the resin forming the protective film B, or may be added to the resin forming the protective film B after being dissolved in the solvent. (a compound having an aromatic hydrocarbon ring or an aromatic heterocyclic ring of 5 or 6 members; Compound (II))

The protective film B according to the present invention preferably contains a compound (compound (II)) having an aromatic hydrocarbon ring or an aromatic hetero ring of 5 or 6 members.

The specific configuration of the compound (II) is not particularly limited, and any compound may be used as long as it is a compound having an aromatic hydrocarbon ring or an aromatic hetero ring of 5 or 6 members. In the above, the aromatic hydrocarbon ring or the aromatic heterocyclic ring of the above-mentioned five or six members is a compound which is linked to each other with a single bond or two or less atoms (hereinafter also referred to as "additive N"). good.

Such an additive is coordinated to cellulose acetate by a plurality of CH/π interaction forces, thereby inhibiting the infiltration of water molecules into the cellulose acetate and the additive, thereby reducing optical properties. The change is better.

The aromatic ring of 5 or 6 members is preferably a 6 π electron system. When a broad aromatic ring of a π-conjugated system such as a naphthalene ring (10 π), a benzoxazole ring (10 π), or an anthracene ring (14 π), the π/π interaction becomes stronger, so compared with the fiber The CH/π interaction between the acetate and the additive causes the π/π interaction between the additives to become dominant, which tends to cause deterioration of the compatibility of cellulose acetate, and bleed out with time. Further, even in the case of compatibility, since the distance between the cellulose acetate and the additive becomes long, the optical characteristics are easily changed.

Examples of such an aromatic ring include a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring (1,2,3-triazole ring, 1,2,4-triazole ring), a tetrazole ring, and a furan ring. , oxazole ring, isoxazole ring, oxadiazole ring, eclipse An azole ring, a thiophene ring, a thiazole ring, an isothiazole ring, a thiadiazole ring, an isothiadiazole ring, and the like. Among these, the hetero atom other than the carbon atom forming the aromatic ring contains only an aromatic ring of a nitrogen atom, and the effect of suppressing fluctuation in optical characteristics is excellent, which is preferable.

Further, as a hetero atom other than a carbon atom forming an aromatic ring An aromatic ring containing only a nitrogen atom is less likely to cause reaction or decomposition under the coexistence with cellulose acetate, and a phase difference film excellent in durability can be obtained, which is preferable. Specifically, the aromatic ring is preferably a pyrrole ring, a pyrazole ring, an imidazole ring, or a triazole ring (1,2,3-triazole ring, 1,2,4-triazole ring), and is preferably selected. At least one of the group consisting of a free pyrazole ring, an imidazole ring, and a triazole ring.

The aromatic ring of 5 or 6 members is separated by a single bond It is preferable that the CH/π interaction of the cellulose acetate and the additive becomes strong, and the change in optical characteristics is suppressed, and the two or more atoms are bonded together. The term "interconnected with two or less atoms" means that the minimum number of atoms existing between the connected substituents is two or less among the atoms constituting the linking group. Specifically, the number of linking atoms of the ether group (-O-) is 1, the number of linking atoms of the oxiranyl group (-CO-O-) is 2, and the linking atom of the carbonate group (-O-CO-O-) The number is 3. In order to further suppress variations in optical characteristics, a single bond is preferred.

Set the three 5 or 6 member aromatic rings to A, B, and C. When A and B and B and C are connected, the dihedral angles of A and B and B and C are small, and since the respective aromatic rings can simultaneously form a CH/π interaction, it is preferable. When the dihedral angle becomes too small, the π/π interaction Easy to become dominant. Therefore, the dihedral angles of A and B and B and C are preferably 0° or more and 45° or less, and more preferably 5° or more and 40° or less, and more preferably 10° or more and 35° or less.

<Compound having a structure represented by the general formula (2)>

In the present invention, the additive N is particularly preferably a compound having a structure represented by the following formula (2).

In the above formula (2), A ₁ , A ₂ and B are each independently represented by an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, 2-ethyl). A hexyl group or the like, a cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), an aromatic hydrocarbon ring or an aromatic hetero ring. Among them, an aromatic hydrocarbon ring or an aromatic hetero ring is preferred. The structure of the aromatic hydrocarbon ring or the aromatic heterocyclic ring of 5 or 6 members is not limited, and examples thereof include a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, and a triazole ring (1, 2, 3-3). Oxazole ring, 1,2,4-triazole ring), tetrazole ring, furan ring, oxazole ring, isoxazole ring, oxadiazole ring, isoxazole ring, thiophene ring, thiazole ring, isothiazole ring , thiadiazole ring, isothiadiazole ring and the like.

The aromatic hydrocarbon ring or the aromatic heterocyclic ring of 5 or 6 members represented by A ₁ , A ₂ and B may have a substituent, and examples of the substituent include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and the like). Iodine atom, etc.), alkyl (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, 2-ethylhexyl, etc.), cycloalkyl (cyclohexyl, cyclopentyl) Base, 4-n-dodecylcyclohexyl, etc.), alkenyl (vinyl, allyl, etc.), cycloalkenyl (2-cyclopenten-1-yl, 2-cyclohexen-1-yl) Equivalent, alkynyl (ethynyl, propargyl, etc.), aromatic hydrocarbon ring (phenyl, p-tolyl, naphthyl, etc.), aromatic heterocyclic (2-pyrrolyl, 2-furyl, 2-thienyl, pyrrolyl, imidazolyl, oxazolyl, thiazolyl, benzimidazolyl, benzoxazolyl, 2-benzothiazolyl, pyrazolone, pyridyl, pyridone, 2 -pyrimidinyl, triazinyl, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, oxazolyl, isoxazolyl, 1,2,4-oxadiazole Base, 1,3,4-oxadiazolyl, thiazolyl, isothiazolyl, 1,2,4-thiadiazolyl, 1,3,4-thiadiazolyl, etc.), cyano, hydroxyl, nitrate Base, carboxyl, alkoxy (methoxy, ethoxy, isopropoxy, tert-butoxy, n-octyloxy, 2-methoxyethoxy, etc.), aryloxy (phenoxy, 2-methyl) Phenoxy, 4-tert-butylphenoxy, 3-nitrophenoxy, 2-tetraammonium phenoxy, etc., decyloxy (methyloxy, ethoxylated, trimethyl) Ethyl ethoxy, stearyloxy, benzhydryloxy, p-methoxyphenylcarbonyloxy, etc.), amine group (amine group, methylamino group, dimethylamino group, anilino group) , N-methyl-anilino, diphenylamino, etc.), mercaptoamino group (formylamino group, ethionylamino group, trimethylethylamino group, lauryl amine group, benzene Mercaptoamine, etc.), alkyl and arylsulfonylamino (methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino, 2,3,5-tri Chlorophenylsulfonylamino, p-methylphenylsulfonylamino, etc., mercapto, alkylthio (methylthio, ethylthio, n-hexadecylthio, etc.), aromatic sulfur Base (phenylthio, p-chlorophenylthio, m-methoxyphenylthio, etc.), amine sulfonyl (N-ethylamine sulfonyl, N-(3-dodecylpropoxy) Aminesulfonyl, N,N-dimethylaminesulfonyl, N-B Sulfonamide, N-benzylidenesulfonylsulfonyl, N-(N'phenylaminecarbamyl)aminesulfonyl, etc.), sulfonic acid group, mercapto group (ethylidene group, trimethyl group) Ethylmercaptopurine, etc., aminomethyl sulfhydryl (amine methyl sulfhydryl, N-methylamine carbhydryl, N,N-dimethylamine carbhydryl, N,N-di-n-octyl Each group such as a carbamine group or a N-(methylsulfonyl)carbamyl group.

In the above formula (2), A ₁ , A ₂ and B are represented by a benzene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring (1,2,3-triazole ring, 1,2,4- The triazole ring is preferably a resin composition which is excellent in the effect of changing optical characteristics and excellent in durability, and is preferably selected from the group consisting of a pyrazole ring, an imidazole ring and a triazole ring. At least one of them.

In the above formula (2), T ₁ and T _{2 are} preferably independently represented as a pyrrole ring, a pyrazole ring, an imidazole ring or a triazole ring (1,2,3-triazole ring, 1,2,4-three, respectively). Oxazole ring). Among these, a resin composition which is excellent in variation in optical characteristics and excellent in durability and excellent in durability is preferable, and a pyrazole ring or a 1,2,4-triazole ring is preferable. Pyrazole ring. The pyrazole ring, the imidazole ring or the triazole ring (1,2,3-triazole ring, 1,2,4-triazole ring) represented by T ₁ and T ₂ may be a tautomer. The specific configuration of the pyrrole ring, the pyrazole ring, the imidazole ring, the 1,2,3-triazole ring, and the 1,2,4-triazole ring is as follows.

In the formula, * indicates a bonding position with L ₁ , L ₂ , L ₃ or L ₄ . R ^{8 is} shown as a hydrogen atom or a non-aromatic substituent. The non-aromatic substituent represented by R ⁸ may be the same as the non-aromatic substituent among the substituents which A ₁ in the above formula (2) may have. When the substituent represented by R ⁸ is a substituent having an aromatic group, A ₁ and T ₁ or B and T _{1 are} easily twisted, and A ₁ , B and T ₁ cannot simultaneously form a cellulose acetate. The CH/π interaction makes it difficult to suppress variations in optical characteristics. R ^{8 is} preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a fluorenyl group having 1 to 5 carbon atoms, particularly preferably a hydrogen atom, in order to enhance the effect of suppressing the change in optical characteristics.

In the above formula (2), T ₁ and T ₂ may have a substituent, and examples of the substituent include the same substituents as those of A ₁ and A ₂ in the above formula (2).

In the above formula (2), L ₁ , L ₂ , L ₃ and L ₄ are each independently shown as a single bond or a divalent linking group, and an aromatic hydrocarbon ring or an aromatic heterocyclic ring of 5 or 6 members is intervened. Two or less atoms are connected and connected. The two or less atoms interposed between the atoms constituting the linking group are the smallest number of atoms existing between the connected substituents. The divalent linking group having two or less linked atoms is not particularly limited, and is selected from an alkyl group, an alkenyl group, an alkynyl group, O, (C=O), NR, S, (O=S=O). The divalent linking group of the group formed, or the combination of the two linking groups. R is shown as a hydrogen atom or a substituent. Examples of the substituent represented by R include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), naphthene. (cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl, etc.), aromatic hydrocarbon ring (phenyl, p-tolyl, naphthyl, etc.), aromatic heterocyclic (2-furan) A group, a 2-thienyl group, a 2-pyrimidinyl group, a 2-benzothiazolyl group, a 2-pyridyl group, etc.), a cyano group, etc. The divalent linking group represented by L ₁ , L ₂ , L ₃ and L ₄ may have a substituent, and the substituent is not particularly limited, and may be, for example, a substituent which may be possessed by A ₁ and A ₂ in the above formula (2). For the same base.

In the above formula (2), the planarity of the compound represented by the above formula (2) is increased, and the CH/π interaction with the water-adsorbing resin is enhanced, and the change in optical properties is suppressed. Therefore, L ₁ , L ₂ , L ₃ and L _{4 are} preferably a single bond, or O, (C=O)-O, O-(C=O), (C=O)-NR or NR-(C =O), which is preferably a single bond.

In the above formula (2), n is an integer of 0 to 5. When n is an integer of 2 or more, the plurality of A ₂ , T ₂ , L ₃ and L ₄ in the above formula (2) may be the same or different. When n is larger, the CH/π interaction between the compound represented by the above formula (2) and the cellulose acetate becomes stronger, and the effect of suppressing the variation of optical properties is excellent; when n is smaller, the fiber is The compatibility of the cellulose acetate is excellent. Therefore, n is preferably an integer of 1 to 3, and is preferably an integer of 1 to 2.

<Compound having a structure represented by the general formula (3)>

The compound represented by the formula (2) is preferably a compound represented by the following formula (3).

A ₁ , A ₂ , T ₁ , T ₂ , L ₁ , L ₂ , L ₃ and L ₄ in the formula (3) are respectively A ₁ , A ₂ , T ₁ in the above formula (2) T ₂ , L ₁ , L ₂ , L ₃ and L ₄ are synonymous. A ₃ and T ₃ are each represented by the same group as A ₁ and T ₁ in the formula (2). L ₅ and L ₆ are the same as those of L ₁ in the above formula (2). m is shown as an integer from 0 to 4.

When m is smaller, due to compatibility with cellulose acetate It is excellent, so m is preferably an integer of 0 to 2, and preferably 0 to 1 number.

<Compound having a structure represented by the general formula (2.1)>

The compound having a structure represented by the formula (2) is preferably a triazole compound having a structure represented by the following formula (2.1).

A ₁ , B, L ₁ and L ₂ in the formula (2.1) are represented by the same groups as A ₁ , B, L ₁ and L ₂ in the above formula (2). k is shown as an integer from 1 to 4. T _{1 is} shown as a 1,2,4-triazole ring.

Further, the triazole having the structure represented by the above formula (2.1) The compound is preferably a triazole compound having a structure represented by the following formula (2.2).

In the general formula (2.2), Z is represented by the following formula (2.2a) structure. q is shown as an integer from 2 to 3. For at least one Z substituted by a benzene ring, at least two of Z are bonded to an ortho or meta position.

In the formula (2.2a), R ¹⁰ is represented by a hydrogen atom, an alkyl group or an alkoxy group. p is shown as an integer from 1 to 5. * indicates the bonding position with the benzene ring. T _{1 is} shown as a 1,2,4-triazole ring.

The above formula (2), (3), (2.1) or (2.2) The compound represented may also form a hydrate, solvate or salt. Further, in the present invention, the hydrate may also contain an organic solvent, and the solvate may also contain water. That is, the "hydrate" and "solvate" are mixed solvates containing both water and an organic solvent. As the salt, an acid addition salt formed by an inorganic or organic acid is contained. Examples of the inorganic acid include, for example, hydrogen halide acid (hydrochloric acid, hydrogen bromide acid, etc.), sulfuric acid, phosphoric acid, and the like, and are not limited thereto. Further, examples of the organic acid include acetic acid, trifluoroacetic acid, propionic acid, butyric acid, oxalic acid, citric acid, benzoic acid, alkylsulfonic acid (methanesulfonic acid, etc.), and allylsulfonic acid (benzenesulfonic acid). Further, 4-methylbenzenesulfonic acid, 1,5-naphthalene disulfonic acid, etc., and the like are not limited thereto. Among these, a hydrochloride, an acetate, a propionate, and a butyrate are preferable.

As an example of a salt, for example, the acidity of the parent compound Partially replaced by a metal ion (such as an alkali metal salt such as a sodium or potassium salt, an alkaline earth metal salt such as a calcium or magnesium salt, an ammonium alkali metal ion, an alkaline earth metal ion, or an aluminum ion), or The salt formed when it is adjusted with an organic base (ethanolamine, diethanolamine, triethanolamine, oroproline, piperidine, etc.) is not limited to these. Among these, a sodium salt or a potassium salt is preferred.

As an example of the solvent contained in the solvate, there are generally Machine solvents can be included. Specifically, for example, an alcohol (for example, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol), an ester (for example, ethyl acetate), Hydrocarbyl (e.g., toluene, hexane, heptane), ether (e.g., tetrahydrofuran), nitrile (e.g., acetonitrile), ketone (acetone), and the like. A solvate of an alcohol (for example, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol) is preferred. These solvents may be the reaction solvent used in the synthesis of the above compound, the solvent used in the crystallization purification after the synthesis, or a mixture thereof.

Moreover, it can contain two or more solvents at the same time, and can also be a package The form of water and solvent (for example, water and alcohol (for example, methanol, ethanol, t-butanol, etc.), etc.).

Still, even the above formula (2), (3), (2.1) or The compound represented by (2.2) may be added in the form of not containing water, a solvent or a salt, or a hydrate, a solvate or a salt may be formed in the retardation film of the present invention.

The above formula (2), (3), (2.1) or (2.2) The molecular weight of the compound to be represented is not particularly limited, and the smaller the compatibility with the resin, the larger the viscosity of the compound is, the higher the effect of suppressing the change in the optical value of the change in the environmental humidity is. Therefore, it is preferably 150 to 2,000. It is 200 to 1500, more preferably 300 to 1000.

The following is an example of the present invention having 5 or 6 members. Specific examples of the compound of an aromatic hydrocarbon ring or an aromatic hetero ring. Among them, preferably It is a compound represented by the above formula (2), (3), (2.1) or (2.2). The aforementioned compound having an aromatic hydrocarbon ring or an aromatic heterocyclic ring of 5 or 6 members which can be used in the present invention is not limited to the following specific examples. Further, as described above, the following specific examples may be tautomers, and may also form a hydrate, a solvate or a salt. Further, the compound is defined by the following number. That is, the compound of the following "1" is also called "compound (2-1)".

In the protective film B according to the present invention, the content of the compound (compound (II)) having an aromatic hydrocarbon ring or an aromatic heterocyclic ring of 5 or 6 members is not particularly limited, and may be adjusted in an appropriate amount to be contained in the protective film. B. The content of the compound of the compound (II) is, for example, preferably from 1 to 30 parts by mass, more preferably from 3 to 20 parts by mass, particularly preferably from 5 to 10 parts by mass, per 100 parts by mass of the cellulose acetate. . As long as such an amount, the phase difference function and tear strength of the protective film B can be improved. Further, since the volatility under high temperature and high humidity is lowered, the bleeding resistance of the protective film B can be improved, and the sharpness of the image can be improved.

Further, as a method of adding the compound (II), a powder may be added to the resin forming the protective film B, or may be dissolved in a solvent. After that, it is added to the resin forming the protective film B.

(plasticizer)

The cellulose acetate film as the protective film B may contain a plasticizer in order to improve the fluidity of the composition at the time of film production or the flexibility or workability of the film. Examples of the plasticizer include, for example, a sugar ester-based plasticizer, a polyester-based plasticizer, a polyol ester-based plasticizer, an acrylic compound, and a polycarboxylic acid ester-based plasticizer (including a phthalate-based plasticizer). ), glycolate plasticizer, ester plasticizer (including citric acid ester plasticizer, fatty acid ester plasticizer, phosphate ester plasticizer, trimellitate plasticizer, etc.), styrene Compounds, etc. Among the plasticizers, it is highly compatible with the effectiveness of moisture permeability and compatibility with cellulose acetate, and preferably contains a sugar ester-based plasticizer (sugar ester compound) selected from the following It is at least one type of plasticizer which is a group of a plasticizer and an acrylic compound. These may be used alone or in combination of two or more.

The plasticizer has both an improvement in moisture and heat resistance, and a fiber From the viewpoint of the compatibility of the vitamin acetate, the molecular weight is preferably 5,000 or less, more preferably 3,000 or less. When the compound having a molecular weight of 3,000 or less is used as the polymer, the weight average molecular weight (Mw) is preferably 3,000 or less. The preferred molecular weight (Mw) ranges from 100 to 2,500, more preferably from 300 to 2,000.

Sugar ester plasticizer (sugar ester compound) means a compound having 1 to 12 furanose structures or a pentose structure, and the compound All or a portion of the hydroxyl groups in the group are esterified compounds. A sugar ester type plasticizer can be added for the purpose of water repellency.

As a raw material for synthesizing a sugar ester compound related to the present invention Examples of the sugar include, for example, glucose, galactose, mannose, fructose, xylose, or arabinose, lactose, sucrose, and the like.

As an OH group in a rutose structure or a furanose structure The monocarboxylic acid to be used in the esterification of all or a part is not particularly limited, and a conventional aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid or the like can be used. The carboxylic acid to be used may be one type or two or more types.

As an example of a preferred aliphatic monocarboxylic acid, for example, Acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and the like.

As an example of a preferred alicyclic monocarboxylic acid, for example, a ring Pentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, or derivatives thereof.

As an example of a preferable aromatic monocarboxylic acid, for example, a benzoic acid benzoic acid such as benzoic acid, phenylacetic acid or toluic acid is introduced into an aromatic monocarboxylic acid, cinnamic acid, diphenylglycolic acid or biphenylcarboxylic acid, which is formed by introducing 1 to 5 alkyl groups or alkoxy groups. An aromatic monocarboxylic acid having two or more benzene rings such as naphthalenecarboxylic acid or tetrahydronaphthalenecarboxylic acid, or a derivative thereof, is particularly preferably benzoic acid.

As a preferred example of such a sugar ester, the following A sucrose ester represented by the formula (FA).

R ₁ to R _{8 of the} formula (FA) are each independently represented by a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group. R ₁ to R ₈ may be the same or different from each other.

The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. As an example of the substituted or unsubstituted alkylcarbonyl group, a methylcarbonyl group (ethenyl) is contained. Examples of the substituent of the alkyl group include an aromatic hydrocarbon ring group such as a phenyl group.

The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. As an example of the arylcarbonyl group, a phenylcarbonyl group is contained. Examples of the substituent of the aromatic hydrocarbon ring group include an alkyl group such as a methyl group or an alkoxy group such as a methoxy group.

The compound represented by the above formula (FA) preferably has an average degree of substitution of from 3.0 to 8.0, more preferably from 4.0 to 7.5, and is more preferably controlled to have a moisture permeability by a value of from 4.5 to 7.0. And compatibility with cellulose acetate.

In the present invention, the degree of substitution of the compound represented by the formula (FA) is a number substituted by a substituent other than hydrogen among the eight hydroxyl groups contained in the formula (FA), that is, The number of the base other than the hydrogen contained in R ₁ to R ₈ of the general formula (FA) is shown. Therefore, when R ₁ to R ₈ are all substituted by a substituent other than hydrogen, the degree of substitution is 8.0 which is the maximum value, and when all of R ₁ to R ₈ are a hydrogen atom, the degree of substitution is 0.0.

a compound having a structure represented by the formula (FA) It is difficult to form the number of the hydroxyl groups and the number of the OR groups, and it is known that the number of the hydroxyl groups in the formula and the components having different OR groups are mixed in several types. Therefore, in terms of the degree of substitution of the formula (FA) in the present invention, it is preferred to use an average degree of substitution, and the average ratio can be used to determine the average ratio of the area ratio of the graph showing the degree of substitution distribution by high-speed liquid chromatography. Degree of substitution.

In the formula (FA), R ₁ to R ₈ represent a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted arylcarbonyl group, and R ₁ to R ₈ may be the same or different (hereinafter, also referred to as R _{1 )} ~R ₈ is a sulfhydryl group). Specific examples of R ₁ to R ₈ include a mercapto group derived from a monocarboxylic acid used in the synthesis of the above-exemplified sugar ester compound.

Specific examples of the sugar ester compound according to the present invention are listed below. However, when any of R ₁ to R ₈ is the same substituent R, the present invention is not limited thereto. Further, in the following examples, the polyester compound is defined by the following symbols. Further, in the present invention, R ₁ to R ₈ may be each a sugar ester compound having a different basis.

The saccharide ester compound of the present invention can be thiolated The agent (also known as an esterifying agent, for example, an acid halide such as acetamidine chloride or an anhydride such as acetic anhydride) is produced by reacting with the sugar, and the degree of substitution can be increased by the amount of the thiolating agent. Timing, adjustment of the esterification reaction time to control, but by mixing the sugar ester compounds with different degrees of substitution, or by simply mixing the compounds with different degrees of substitution, the average of the objects can be adjusted. A component with a degree of substitution or less than 4 degrees.

As an example of other sugar esters, it includes the Japanese special opening A compound described in Japanese Laid-Open Patent Publication No. Hei 10-237084.

Further, the polyester-based plasticizer is not particularly limited, and for example, for example, a hydroxyl group (OH group) polymer (polyester polyol) obtained by condensation reaction of a dicarboxylic acid or the ester-forming derivative with a diol, or a hydroxyl group at the terminal of the polyester polyol A polymer blocked by a monocarboxylic acid (end blocking polyester). The ester-forming derivative herein means an esterified product of a dicarboxylic acid, cerium chloride dicarboxylate or an anhydrous product of a dicarboxylic acid.

It is preferred to use a polyester represented by the following formula (FB-1) The plasticizer is preferred because it has a high degree of moisture permeability control and compatibility with cellulose acetate.

In the above formula, B is a linear chain having a carbon number of 2 or more and 6 or less. Or a branched alkyl group or a cycloalkyl group, and A is an aromatic ring group having a carbon number of 6 or more and 14 or less, or an aliphatic group having 4 to 12 carbon atoms, and n is a natural number of 1 or more.

The compound represented by the above formula has an aromatic ring a dicarboxylic acid (also known as an aromatic dicarboxylic acid) and a linear or branched alkanediol or a cycloalkanediol having a carbon number of 2 or more and 6 or less, and having both ends unblocked by a monocarboxylic acid .

As an aromatic dicarboxylic acid having 6 or more and 16 or less carbon atoms, For example, phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid Acid, 2,6-naphthalene dicarboxylic acid, 2,8-naphthalene dicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and the like. Among them, phthalic acid and terephthalic acid are preferred.

As an aromatic dicarboxylic acid having 4 or more and 12 or less carbon atoms, For example, 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 1,4-butanedicarboxylic acid (adipate), 1,5-pentane Dicarboxylic acid (pimelic acid), 1,8-octane dicarboxylic acid (sebacic acid), etc., particularly preferably adipic acid or succinic acid.

Further, from the viewpoint of enhancing the strength of the film, the dicarboxylic acid is preferably a mixed aromatic dicarboxylic acid or an aliphatic dicarboxylic acid.

Examples of the linear or branched alkanediol or cycloalkanediol having a carbon number of 2 or more and 6 or less include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1 , 3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6 - hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol or the like. Among them, ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, and 1,3-butylene glycol are preferred.

Among them, A is a naphthalene ring or a biphenyl ring which may have a substituent, and it is preferred to obtain the effects of the present invention. Here, the term "substituent" means an alkyl group, an alkenyl group or an alkoxy group having 1 or more and 6 or less carbon atoms.

The hydroxyl value (OH number) of the polyester compound is preferably 100 mgKOH/g or more and 500 mgKOH/g or less, more preferably 170 mgKOH/g to 400 mgKOH/g. When the hydroxyl value is for this range, The compatibility of the vitamin acetate will become suitable.

Polyester compound when the hydroxyl value is 400 mgKOH/g or less The hydrophobicity of the substance does not become excessively large; when the hydroxyl group is 170 mgKOH/g or more, the intermolecular interaction (hydrogen bond, etc.) of the polyester compounds does not become too strong, and thus it is considered that the film can be prevented from being excessively strong. Precipitate.

Also, the measurement of the hydroxyl value can be applied to Japanese industrial specifications. JIS K1557-1: The acetic anhydride method described in 2007.

The number average molecular weight (Mn) of the above polyester compound is It is calculated by the following formula.

[Number 1] Mn = (number of hydroxyl groups in the molecule) × 56110 / (hydroxyl number) = 2 × 56110 / (hydroxyl price)

Mn = (number of hydroxyl groups in the molecule) × 56110 / (hydroxyl number) = 2 × 56110 / (hydroxyl price)

Further, the preferred number average molecular weight of the polyester compound is from 300 to 2,000.

The polyester compound may be subjected to a hot melt condensation method by a polyesterification reaction or a transesterification reaction of the above dicarboxylic acid and a diol according to a usual method, or a ruthenium chloride and a diol derived from the acid. Any of the methods of the interface condensation method can also be easily synthesized.

The following polyester compounds are exemplified below.

It is preferred to use a polyester represented by the following formula (FB-2) The plasticizer is preferred because it has a high degree of moisture permeability control and compatibility with cellulose acetate.

[92] General formula (FB-2) B-(GA) _n -GB

In the above formula (FB-2), B is a hydroxyl group or a carboxylic acid residue, and G is an alkanediol residue having a carbon number of 2 to 18 or an aromatic diol residue having a carbon number of 6 to 12 or a carbon number of 4~12 oxyalkylene glycol residue, A is shown as a C4 to 12 alkyl dicarboxylic acid residue or a C6 to 12 aryl dicarboxylic acid residue, and n is an integer of 1 or more. .

In the formula (FB-2), it is a hydroxyl group or a carboxylic acid residue represented by B, an alkylene glycol residue represented by G, or an oxyalkylene glycol residue or an aromatic diol residue, and is represented by A. It is composed of an alkyl dicarboxylic acid residue or an aryl dicarboxylic acid residue and is obtained by the same reaction as a general ester compound.

The carboxylic acid component of the polyester compound represented by the formula (FB-2) includes, for example, acetic acid, propionic acid, butyric acid, benzoic acid, p-tert-butyl benzoic acid, o-toluic acid, m-toluic acid, p-toluene. Formic acid, dimethyl benzoic acid, ethyl benzoic acid, n-propyl benzoic acid, aminobenzoic acid, ethoxylated benzoic acid, an aliphatic acid, etc., may be used alone or in combination of two or more.

The alkanediol component having 2 to 18 carbon atoms of the polyester compound represented by the formula (FB-2) is ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,2-butylene. Glycol, 1,3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl -1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dihydroxymethylpentane), 2-n-butyl-2-ethyl 1,3-1,3-propanediol (3,3-dihydroxymethylglycol) Alkane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3- Hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-nonanediol, 1,12-octadecanediol, etc., such diols, One type or a mixture of two or more types is used.

Especially alkanediol with a carbon number of 2~12, due to the cellulose B The acid ester is excellent in compatibility, so it is particularly preferable. Further, it is preferably an alkanediol having 2 to 6 carbon atoms, more preferably an alkanediol having 2 to 4 carbon atoms.

As a polyester plasticizer represented by the general formula (FB-2) An aromatic diol having 6 to 12 carbon atoms, for example, a cyclic diol such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, cyclohexane diethanol or 1,4-benzenedimethanol. As the diol, one or a mixture of two or more kinds may be used.

Further, as the polyester system represented by the above formula (FB-2) Examples of the compound having a carbon number of 4 to 12 oxyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These diols may be used alone or in combination of two or two. The above mixture.

As the polyester compound represented by the formula (FB-2) The alkyl dicarboxylic acid component having 4 to 12 carbon atoms, such as succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, sebacic acid, sebacic acid, dodecane dicarboxylic acid, etc. These may be used alone or in combination of two or more.

As the polyester compound represented by the formula (FB-2) The aryldicarboxylic acid component having 6 to 12 carbon atoms is phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalene dicarboxylic acid, 1,4-naphthalenedicarboxylic acid or the like.

Polyester compound represented by the formula (FB-2), weight The average molecular weight is preferably from 300 to 3,000, and preferably from 350 to 1500. As appropriate. Further, the acid value is 0.5 mgKOH/g or less, the hydroxyl group (hydroxyl group) is 25 mgKOH/g or less, the acid value is preferably 0.3 mgKOH/g or less, and the hydroxyl group (hydroxyl group) is 15 mgKOH/g or less.

The weight average molecular weight of the polyester plasticizer is It was calculated by the measurement of gel permeation chromatography (GPC) by the following measurement conditions.

[化93]

Solvent: tetrahydrofuran (THF)

Pipe column: TSKgel G2000HXL (Tosoh Co., Ltd., used in 2 connections)

Column temperature: 40 ° C

Sample concentration: 0.1% by mass

Device: HLC-8220 (Dongcao (share) system)

Flow rate: 1.0ml/min

Calibration curve: Use the calibration curve of PStQuick F (Tosoh Corporation).

Although specific examples of the polyester compound represented by the formula (FB-2) of the present invention are exemplified below, the present invention is not limited thereto. Further, in the following examples, the polyester compound is defined by the following symbols.

The viscosity of polyester-based plasticizers may depend on molecular structure or The amount is different, but in the case of an adipic acid plasticizer, since it has high compatibility with cellulose acetate and has a high effect of imparting plasticity, it is preferably 200 to 5000 mPa·s (25 ° C). The scope of). The polyester-based plasticizers may be one type or two or more types may be used in combination.

Polyol ester-based plasticizer, which is an aliphatic type of 2 or more The ester compound (alcohol ester) of the "polyol" and "monocarboxylic acid" is preferably a 2 to 20-valent aliphatic polyol ester. The polyol ester compound preferably has an aromatic ring or a cycloalkane ring in the molecule.

In the specific example of the polyol ester-based plasticizer, it includes three The ester compound represented by the formula (I) described in JP-A-2008-88292, hydroxymethylpropane triacetate, trimethylolpropane benzoate, pentaerythritol tetraacetate )Wait.

a polycarboxylic acid ester-based plasticizer, which is 2 or more (preferably An ester compound of "polycarboxylic acid" and "alcohol compound" of 2 to 20 valence. The polyvalent carboxylic acid is preferably a 2 to 20-valent aliphatic polycarboxylic acid, a 3 to 20-valent aromatic polycarboxylic acid, or a 3 to 20-valent alicyclic polycarboxylic acid.

As an example of the polycarboxylic acid, it contains, for example, trimellitic acid, Aromatic polycarboxylic acid or a derivative thereof having a valence of 3 or more symmetrical benzenetricarboxylic acid or pyromic acid; succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, Aliphatic polycarboxylic acid like tetrahydrophthalic acid; tartaric acid, propanol diacid, malic acid, citric acid-like oxypolycarboxylic acid, etc., in order to suppress volatilization from the film, preferably oxypolycarboxylic acid .

As an example of an alcohol compound, it has a linear or side chain An aliphatic saturated alcohol compound, an aliphatic unsaturated alcohol compound having a linear or side chain, an alicyclic alcohol compound or an aromatic alcohol compound, or the like. The carbon number of the aliphatic saturated alcohol compound or the aliphatic unsaturated alcohol compound is preferably from 1 to 32, more preferably from 1 to 20, still more preferably from 1 to 10. Examples of the alicyclic alcohol compound include cyclopentanol, cyclohexanol and the like. Examples of the aromatic alcohol compound include phenol, p-cresol, dimethylphenol, benzyl alcohol, cinnamyl alcohol and the like. The alcohol compounds may be one type or a mixture of two or more types.

The molecular weight of the polycarboxylate-based plasticizer is not particularly limited. However, it is preferably in the range of 300 to 1000, and preferably in the range of 350 to 750. The molecular weight of the polycarboxylic acid ester-based plasticizer is preferably as large as possible in terms of suppressing bleeding. From the viewpoint of moisture permeability or compatibility with cellulose acetate, the smaller the better.

As an example of a polycarboxylic acid ester type plasticizer, it includes Japan. The ester compound (B) represented by the formula (II) described in JP-A-2008-88292.

Polycarboxylate-based plasticizer, which may also be phthalic acid Ester-based plasticizer. Examples of the phthalate-based plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, Dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, and the like.

As an example of a glycolate plasticizer, it contains an alkyl ortho Alkyl phthalic acid glycolate. Examples of alkyl alkyl phthalic acid glycolic acid esters include methyl phthalic acid methyl ester, Ethyl ethyl phthalate, ethyl propyl phthalate, butyl butyl phthalate, octyl octyl phthalate Wait.

As an ester-based plasticizer, it contains a fatty acid ester-based plasticizer. Agent, citrate-based plasticizer, phosphate-based plasticizer, trimellitic acid-based plasticizer, and the like.

As an example of a fatty acid ester plasticizer, it contains oleic acid Ester, ethyl decyl methyl citrate, dibutyl sebacate, and the like. Examples of the citrate-based plasticizer include ethoxylated trimethyl citrate, ethionyl triethyl citrate, acetyl citrate tributyl acrylate, and the like. Examples of the phosphate-based plasticizer include triphenyl phosphate, tricresyl phosphate, tolyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate (BDP), and phosphoric acid. Trioctyl ester, tributyl phosphate, and the like. Examples of the trimellitic acid-based plasticizer include octyl trimellitate, n-octyl trimellitate, isodecyl trimellitate, isodecyl trimellitate and the like.

The content of the above plasticizer is not particularly limited, as opposed to The cellulose acetate contained in the protective film B (cellulose acetate film) is preferably 100% by mass, preferably 0.1 to 30% by mass, more preferably 5 to 20% by mass. As long as such an amount, the cellulose acetate film will not easily bleed out.

(other additives)

Further, in the protective film B according to the present invention, in place of the above plasticizer, or in addition to the plasticizer, other materials may be included as needed. additive. The other additives are not particularly limited, and examples thereof include a hydrogen bond compound, an active agent, an antioxidant, a colorant, an ultraviolet absorber, a matting agent, acrylic particles, a hydrogen bonding solvent, and an ionic surfactant.

The above hydrogen bonding compound can reduce the hysteresis value Rt for wet Changes in degree of change. Here, as the hydrogen-bonding compound, it is preferred to have a functional group selected from at least a plurality of hydroxyl groups, amine groups, thiol groups, and carboxylic acid groups in one molecule, and it is preferred to have a plurality of functional groups in one molecule. The dissimilar functional group particularly preferably has a hydroxyl group and a carboxylic acid group in one molecule.

The hydrogen bond compound, as a mother core, contains 1 or 2 The aromatic ring is preferred, and the number of the aforementioned functional groups contained in one molecule is divided by the molecular weight of the compound, and the value obtained is preferably 0.01 or more.

The above effects are presumed to be due to the above hydrogen bonding compound. A bond (hydrogen bond) acts on a portion where the cellulose acetate interacts with a water molecule (hydrogen bond) to suppress a change in charge distribution due to detachment of water molecules.

As a specific compound example, for example, Japanese special open Exemplary compound E-104 described in Japanese Patent Publication No. 2012-82235.

Hydrogen bonding compound, relative to cellulose acetate 100 The amount can be added in the range of 1 to 30 parts by mass.

The protective film B related to the present invention serves as an ultraviolet ray For the purpose of line absorption function, it is also preferred to contain an ultraviolet absorber. The ultraviolet absorber is not particularly limited, and the same as those described above which can be contained in the protective film A can be used.

In the cellulose acetate film as the protective film B, purple The amount of the external absorbent to be used varies depending on the type of the ultraviolet absorber, the use conditions, etc., and is generally 0.05 to 10% by mass, preferably 0.1%, based on 100% by mass of the cellulose acetate. A range of ~5 mass% is added.

The matting agent is a fine particle that imparts slidability to the film, as long as it is The transparency of the obtained film may be impaired and heat resistance at the time of melting, and may be any inorganic compound or organic compound. These matting agents may be used singly or in combination of two or more. By using particles having a particle size or shape (for example, a needle shape or a spherical shape) in combination, transparency and slidability can be highly combined. Among these, cerium oxide having excellent transparency (haze) is particularly preferred because it has a refractive index close to that of the acrylic copolymer or the cellulose acetate used as the resin.

As a specific example of cerium oxide, it is preferred to use Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (above is made by Japan Aerosil Co., Ltd.), seahostar KEP-10, seahostar KEP-30, seahostar KEP-50 ( The above are commercially available products of the trade names such as Nippon Shokubai Co., Ltd., sylophobic 100 (manufactured by Fuji Silysia Co., Ltd.), nipsil E220A (manufactured by Japan Silka Co., Ltd.), and admafine SO (manufactured by Admatechs Co., Ltd.).

In terms of the shape of the particles, amorphous, needle-like, flat The flatness, the spherical shape, and the like are not particularly limited, and in particular, when spherical particles are used, the obtained film has good transparency, which is preferable.

The size of the particle, if it is close to the wavelength of visible light, the light If it is scattered and the transparency is poor, it is preferably one which is smaller than the wavelength of visible light, and more preferably 1/2 or less of the wavelength of visible light. If the particle size is too small, there is a case where the slidability cannot be improved, and it is particularly preferable in the range of 80 nm to 180 nm. Further, the size of the particles means the size of the aggregate when the particles are aggregates of primary particles. Further, when the particles are not spherical, they mean the diameter of a circle corresponding to the projected area.

A matting agent, relative to a resin (cellulose acetate), It is added in the range of 0.05 to 10% by mass, preferably 0.1 to 5% by mass.

Protective film B related to the present invention to maintain transparency The amount in the range may contain, for example, the acrylic particles described in the specification of International Publication No. 2010/001668. The acrylic particles have an effect of improving film brittleness.

(physical properties of the film)

Hereinafter, the characteristics of the cellulose acetate film as the protective film B in the present invention will be described.

(film thickness)

The film thickness of the protective film B is not particularly limited, but is preferably 12 to 60 μm, more preferably 15 to 40 μm, and most preferably 15 to 30 μm. When the film thickness of the protective film B is 12 μm or more, it is preferable from the viewpoint that there is no variation in hysteresis value and it is difficult to generate unevenness or light leakage of the display device; on the other hand, when the film of the protective film B is protected When the thickness is 60 μm or less, it is called It is preferable from the viewpoint that it is difficult to generate warpage of the panel.

(transparency)

As an index for judging the transparency of the cellulose acetate film, a haze value (turbidity) is used. In particular, in a liquid crystal display device used outdoors, it is required to obtain sufficient brightness or high contrast even in a bright place, so that the haze value is preferably 0.6% or less, preferably 0.4% or less, more preferably It is 0.3 or less, and the best is 0.2 or less. When used as a scattering film, the haze value may exceed the above range. Further, the internal haze of the film is preferably from 0.01 to 0.1, more preferably from 0.02 to 0.06.

Further, as the cellulose of the protective film B related to the present invention In the acetate film, the total light transmittance is preferably 90% or more, and more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%.

Haze value and transmittance can be measured using a haze meter set.

A film that satisfies the above physical properties, and is preferably as large A liquid crystal display device or a liquid crystal display device for outdoor use is used for a polarizing plate protective film.

(hysteresis / retardation)

The cellulose acetate film as the protective film B is not particularly limited, and the hysteresis value Ro in the in-plane direction defined by the following formulas (i) and (ii) is in the range of 30 to 70 nm, and the thickness direction is When the hysteresis value Rt is in the range of 95 to 140 nm, it is mounted on the VA type display device. The contrast of the time ‧ the viewing angle is preferred. In particular, when the hysteresis value Ro in the in-plane direction is in the range of 45 to 60 nm and the hysteresis value Rt in the thickness direction is in the range of 110 to 135 nm, the contrast ‧ viewing angle when the VA type display device is mounted is improved. good.

Formula (i): Ro = (n _{x -} n _y ) × d (nm)

Formula (ii): Rt={(n _x +n _y )/2-n _z }×d (nm)

In the formulae (i) and (ii), n _x represents a refractive index in the direction x in which the refractive index is the largest in the in-plane direction of the film. n _y represents the refractive index in the direction y perpendicular to the aforementioned direction x in the in-plane direction of the film. n _z represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement was carried out at a measurement wavelength of 590 nm in an environment of ‧55% RH at 23 °C.

(Method for producing cellulose acetate film)

Next, a method of producing a cellulose acetate film will be described. However, the present invention is not limited to this.

As a method for producing a cellulose acetate film, it can be used A manufacturing method such as a normal inflation method, a T-die method, a calendering method, a cutting method, a casting method, an emulsification method, or a hot pressing method, but suppresses coloring, suppresses defects of foreign matter, and suppresses optical defects such as mold lines. In the film forming method, a solution casting film forming method and a melt casting film forming method are preferred, and a solution casting film forming method is preferred because a uniform surface can be obtained.

<solution casting film forming method>

When the film is formed by a solution flow method, the method for producing a cellulose acetate film preferably comprises the steps of dissolving cellulose acetate and a desired additive in a solvent to prepare a dope. a step (dissolution step, dope preparation step); a step of casting the dope on the continuously traveling endless metal support (casting step); and drying the casted dope to form a web (step) Solvent evaporation step); a step of stripping from the metal support (peeling step); a step of drying, stretching, and maintaining the width (extension ‧ width retention ‧ drying step); step of winding the film after completion (winding step) .

Figure 2 is a simulation showing the preferred solution casting film of the present invention A diagram of an example of a concentrated liquid preparation step, a casting step, and a drying step (solvent evaporation step).

From the input kettle 41, the filter 44 removes large condensation The product is supplied to the storage tank 42. Thereafter, various additive liquids are added from the storage tank 42 to the main dope dissolution tank 1.

Thereafter, the main concentrate is filtered by the main filter 3, In addition, the additive addition liquid is added inline from the conduit 16. In most cases, the main dope may contain about 10 to 50% by mass of recycled waste. The so-called re-burning waste is a material obtained by finely pulverizing a film, which is formed by cutting a film at both ends of the film, or a film material which is out of specification due to abrasion or the like. And use it.

Moreover, as a raw material of the resin used in preparation of a dope, It is preferred to use a cellulose acetate, a desired additive or the like in advance to be granulated.

Hereinafter, each step will be described.

1) Dissolution step (dope preparation step)

This step is a step in which a cellulose acetate and a desired additive are dissolved in a solvent mainly containing cellulose acetate as a good solvent to form a dope.

The concentration of cellulose acetate in the concentrate is more concentrated It is preferable to reduce the drying load after casting to the metal support, but if the concentration of the cellulose acetate is too rich, the load during filtration increases, and the filtration accuracy deteriorates. The concentration is preferably from 10 to 35% by mass, more preferably from 15 to 22% by mass.

The solvent used in the dope may be used alone or in combination. However, the good solvent and the weak solvent of the cellulose acetate are preferred because of the production efficiency, and the good solvent is preferred because of the solubility of the cellulose acetate.

The mixing ratio of good solvent to weak solvent, the preferred range is The good solvent is 70 to 98% by mass, and the weak solvent is 2 to 30% by mass. The so-called good solvent or weak solvent is defined as a weak solvent if it can be used alone to dissolve the cellulose acetate to be used as a good solvent; and if it is solely swollen or insoluble. Therefore, depending on the average degree of substitution of the cellulose acetate, the good solvent and the weak solvent may vary.

The good solvent used in the present invention is not particularly limited, and An organic halogen compound such as dichloromethane or dioxolane, acetone, methyl acetate, ethyl acetate methyl acetate or the like is obtained. Particularly preferred is dichloromethane or methyl acetate.

Further, the weak solvent used in the present invention is not particularly limited. For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone or the like can be preferably used. Further, it is preferred that the dope contains 0.01 to 2% by mass of water.

Moreover, the solvent used in the dissolution of cellulose acetate is The solvent removed from the film can be recovered by drying in the film forming step and reused.

Although the trace solvent is contained in cellulose acetate in a trace amount The additive to be added, for example, a plasticizer, a UV absorber, a polymer, a monomer component, etc., can be reused well even if it is contained, and can be purified and used as needed.

When preparing the above-mentioned dope, as cellulose B As a method of dissolving the acid ester, a general method can be used. Specifically, a method of performing at normal pressure, a method of performing at a boiling point or lower of a main solvent, or a method of pressurizing at a boiling point or higher of a main solvent, and a method of performing a method of pressurizing at a boiling point or higher of a main solvent, for example, Japanese Laid-Open Patent Publication No. Hei 9-95544, Japanese Patent Application No. Hei 9 Various methods of dissolving, such as a method of performing a cooling and dissolving method, and a method of performing at a high pressure as described in JP-A-11-21379, are described in the Japanese Patent Publication No. Hei 9-95538. Among them, a method of pressurizing at a boiling point or higher of the main solvent is preferred, and if combined with heating and pressurization, it can be heated to a boiling point or higher in a normal pressure.

Also, the cellulose acetate is mixed with a weak solvent to make it wet. After moistening or swelling, a method of further adding a good solvent to dissolve is also preferably used.

Pressurization can also be carried out by adding an inert gas such as nitrogen. The method is carried out by a method of increasing the vapor pressure of the solvent by heating. The heating system is preferably carried out by an external person, for example, a jacket type, which is preferable because of temperature control.

Adding the heating temperature of the solvent to dissolve the cellulose acetate From the viewpoint of solvability, it is preferred that the heating temperature is high, but when the heating temperature is too high, the required pressure is increased to cause poor productivity.

The preferred heating temperature is 45 to 120 ° C, and preferably 60 to 110 ° C, more preferably 70 ° C to 105 ° C. Also, the pressure can be adjusted so that the solvent does not boil at the set temperature.

Or preferably, a cooling dissolution method can be used, whereby acetic acid can be used. The cellulose acetate is dissolved in a solvent such as a methyl ester.

Next, the fiber is made of a suitable filter material such as filter paper. It is preferred to filter the cellulose acetate solution (dope in solution or dissolved).

As a filter material, it is absolutely filtered to remove insoluble matter or the like. The accuracy is small, but if the absolute filtering accuracy is too small, there will be a problem that the filter mesh is likely to be blocked. Therefore, a filter material having an absolute filtration accuracy of 0.008 mm or less is preferable, and a filter material of 0.001 to 0.008 mm is preferable, and a filter material of 0.003 to 0.007 mm is more preferable.

The material of the filter material is not particularly limited, although general filtration can be used. However, it is preferable to use a filter material made of plastic such as polypropylene or Teflon (registered trademark) or a filter material made of metal such as stainless steel because there is no fiber peeling or the like.

Preferably, the cellulose of the raw material is removed and reduced by filtration. Impurities contained in acetate, especially bright spots foreign matter.

The term "bright spot foreign matter" means that two polarizing plates are arranged in a crossed-in-the-ear state, and a film or the like is placed therebetween, and light is emitted from one side of the polarizing plate side, and when viewed from the other side of the polarizing plate side, it is seen from the opposite side. The point at which the light leaks (foreign matter) is preferably 200 pieces/cm ² or less with a diameter of 0.01 mm or more. Further, it is preferably 100 pieces/cm ² or less, more preferably 50 pieces/m ² or less, still more preferably 0 to 10 pieces/cm ² or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is also small.

Although the filtration of the concentrated liquid can be carried out in a general manner, In the method of filtering at a temperature higher than the boiling point of the solvent at a pressure higher than the boiling point of the solvent and heating at a temperature in which the solvent does not boil, it is preferable because the filtration pressure difference (referred to as differential pressure) before and after filtration is small.

The preferred temperature is 45 to 120 ° C, and preferably 45 to 70. °C, more preferably 45~55 °C.

The filter pressure is better. The filtration pressure is preferably 1.6 MPa or less, and It is preferably 1.2 MPa or less, more preferably 1.0 MPa or less.

2) Casting step

Next, the dope is cast on the metal support. That is, in this step, the dope is fed to the pressurizing mold 30 by a liquid-feeding pump (for example, a pressurized quantitative gear pump), and the metal strip 31 of the endless continuous traveling, for example, a stainless steel belt, or A casting position on a metal support such as a rotating metal roll, and a step of casting a dope from a press die slit.

The slit shape of the metal nozzle portion of the mold can be adjusted, and A pressure mold which makes the film thickness easy to be uniform is preferable. In the press mold, a coat hanger type mold or a T-shaped mold is used, and any of them is suitable. The surface of the metal support is preferably mirrored. In order to increase the film forming speed, a pressurizing mold of two or more bases may be placed on the metal support, and the amount of the concentrated liquid may be divided and laminated. It is also preferable to obtain a film of a laminated structure by a co-casting method in which a plurality of concentrated liquids are simultaneously cast.

The width of the casting, in terms of productivity, More than 1.4m is preferred. More preferably 1.4~4m. When it exceeds 4 m, streaks may be incorporated in the manufacturing process, and the stability in the subsequent conveyance step may be lowered. From the point of view of portability and productivity, it is preferably 1.6 to 2.5 m.

a metal support system in the casting step to It is preferable that the surface is a mirror surface, and the metal support body is preferably a roller which is formed by using a stainless steel belt or a surface which is cast by a casting.

The surface temperature of the metal support in the casting step is -50 ° C ~ The boiling point temperature of the solvent is not high, and the drying speed of the thin strip is preferably high because the temperature is high, but if it is too high, the thin strip may be foamed and the planarity may be deteriorated.

The preferred support temperature is 0~55°C, more preferably 25~ 50 ° C. Alternatively, after the thin strip is gelated by cooling, it is preferably peeled off from the roll in a state in which a residual solvent is contained.

The method of controlling the temperature of the metal support is not particularly limited. There is a method of blowing warm air or cold air, or a method of bringing warm water into contact with the inside of the metal support. Use warm water, because of the effective heat conduction, in the metal The time until the temperature of the support reaches a certain level is short and preferable. When using warm air, there is a case where a wind with a higher temperature than the target temperature is used.

3) Solvent evaporation step

In this step, the thin strip (the dope is cast on the support for casting, and the formed concentrated liquid film is a thin strip) is heated on the support for casting, and the solvent is evaporated.

In order to evaporate the solvent, there is a method of blowing from the side of the thin strip And/or the method of heat transfer from the inside of the support body by means of liquid heat transfer, heat transfer from the surface by radiant heat, etc., the inner liquid heat transfer method is preferred because of good drying efficiency. Also, a method of combining these methods is also applicable. It is preferred that the thin strip on the support after casting is dried on the support under an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C, it is preferable to make the warm wind at this temperature face the top of the thin strip or to heat it by means of infrared rays or the like.

From the point of view of surface quality, moisture permeability, and peelability, When the rust steel strip is formed, the film is formed within 30 to 120 seconds, and the roll film is formed for 5 to 40 seconds, and the strip is preferably peeled off from the support.

4) Stripping step

Next, the strip is peeled off from the metal support. That is, this step is a step of peeling off the thin strip from which the solvent has evaporated on the metal support and peeling off at the peeling position. The stripped strip is sent to the next step.

The temperature in the stripping position on the metal support is -50~40 It is preferably in the range of °C, preferably in the range of 10 to 40 ° C, and is preferably in the range of 15 to 30 ° C for the film formation of the stainless steel, and preferably -30 to 10 ° C for the film formation of the roller.

Still, residual dissolution of the thin strip on the metal support during peeling The dose can be appropriately adjusted depending on the strength of the drying conditions, the length of the metal support, and the like. Specifically, it is preferable to control the amount of residual solvent when the strip is peeled off from the metal support to 15 to 40% by mass, and more preferably 20 to 35% by mass.

In the present invention, the amount of residual solvent is defined by the following formula.

[Number 2] Residual solvent amount (% by mass) = {(M - N) / N} × 100

Further, M is the weight of the sample taken at any time during or after the manufacture of the thin strip or film, and N is the weight obtained by heating M at 115 ° C for 1 hour.

The peeling tension at the time of peeling off the metal support and the film is preferably 300 N/m or less. More preferably, it is in the range of 196 to 245 N/m. However, when wrinkles are likely to occur at the time of peeling, it is preferably 190 N/m or less, and preferably 100 to 190 N/m.

5) Drying ‧ Extension ‧ Width Maintenance Step (dry)

In the drying step of the cellulose acetate film, the strip is peeled off from the metal support and further dried to have a residual solvent amount of 1% by mass or less. Preferably, it is 0.1% by mass or less, and particularly preferably 0% to 0.01% by mass or less.

In the film drying step, in general, it can be taken as a roll to dry The dry method (the way in which the thin strips are alternately passed to the plurality of rolls arranged one above the other to dry them) or the manner in which the strips are conveyed while the strips are being conveyed. For example, after stripping, a drying device 35 that transports the strips through a plurality of rollers arranged in a drying apparatus, and/or a tenter stretching device 34 that clamps both ends of the strips by the jaws is used. , dry the strip.

The means for drying the thin strip is not particularly limited, in general, It can be carried out by hot air, infrared rays, heating rolls, microwaves, etc. From the point of view of convenience, it is preferable to carry out hot air. Too intense drying tends to damage the flatness of the film that has just been completed. The drying by high temperature is preferably carried out by using a residual solvent of about 8% by mass or less. Overall, the drying can be carried out substantially in the range of 40 to 250 °C. In particular, it is preferred to dry it in the range of 40 to 200 ° C. The drying temperature is gradually increased in stages, preferably to about 100 to 150 ° C, preferably from 5 minutes to 30 minutes, more preferably from 6 minutes to 12 minutes.

When using a tenter extension device, it is preferred to use a tenter The left and right holding means can control the length of the film (the distance from the start of holding to the end of the holding) independently and independently. Further, in the tentering step, it is preferable to make a zoning having different temperatures in order to improve the planarity.

Also, between different temperature zones, each zone does not occur. It is also good to set up the neutral zone in the way of interference.

(Extension ‧ Width retention)

Next, it is preferred to use a metal support to extend the strip in at least one direction. The alignment of the molecules in the film can be controlled by the stretching process. In the present invention, in order to obtain the target hysteresis values Ro and Rth, even if the cellulose acetate film is composed of the protective film B of the present invention and contains a hysteresis-increasing agent, it is controlled and extended by the handling tension. It is preferred to operate to control the refractive index. For example, the hysteresis value can be varied by lowering or increasing the tension in the longitudinal direction.

As a specific extension method, the long side of the film can be The direction of the film formation (the direction of the film; the direction of the casting; the direction of the MD) and the direction perpendicular to the film (i.e., the width direction (TD direction)) are sequentially or simultaneously performed biaxially or uniaxially. Preferably, the biaxially stretched film obtained by biaxially stretching in the casting direction (MD direction) and the width direction (TD direction) is used, but the cellulose acetate film according to the present invention may be a uniaxially stretched film or may be Extend the film. In addition, the extension operation can also be divided into multi-stage implementations. Further, in the case of biaxial stretching, simultaneous biaxial stretching can be performed, or it can be carried out in stages. In this case, the so-called gradation may be, for example, an extension in which the extending directions are different, and the extension in the same direction may be divided into a plurality of stages, or the extension of the different directions may be added to any stage. That is, for example, it may be an extension stage as described later:

‧Extension in the casting direction →Extension in the width direction →Extension in the casting direction →Extension in the casting direction

‧Extension in the width direction →Extension in the width direction →Extension in the casting direction Stretching → extending in the casting direction

Moreover, in the case of simultaneous biaxial stretching, it also includes stretching in one direction and relaxing the tension to cause the other to contract.

The stretching ratio in the biaxial direction perpendicular to each other is preferably 0.01 to 2.0% in the casting direction (MD direction) and 10 to 50% in the width direction (TD direction), preferably 0.1 in the casting direction. ~1.0%, in the width direction of 20~40%. The amount of the residual solvent at this time is in the range of 15 to 40%, and it is preferable since the cellulose acetate film exhibits a specified toughness value.

The stretching temperature is usually preferably carried out at a temperature ranging from Tg to Tg + 60 ° C of the resin constituting the film. Usually, the stretching temperature is preferably from 120 ° C to 200 ° C, more preferably from 130 ° C to 200 ° C, and even more preferably from about 140 ° C to less than 190 ° C.

The amount of the residual solvent in the film at the time of stretching is not particularly limited, but the amount of the residual solvent in the stretching treatment in the width direction is preferably 2 to 5% by mass.

The method of extending the thin strip is not particularly limited. For example, a method of setting a circumferential speed difference for a plurality of rollers and extending the longitudinal direction of the roller by a roller in the longitudinal direction; fixing both ends of the thin strip by a clamp or a needle, and spacing the clamp or the needle at A method in which the traveling direction is expanded to extend in the longitudinal direction, a method of expanding in the lateral direction and extending in the lateral direction, or a method of expanding both vertically and horizontally and extending in both the longitudinal and lateral directions. Of course, these methods can also be used in combination. Among them, it is particularly preferable to extend the tenter pattern in which both ends of the thin strip are gripped by a clamp or the like in the width direction (lateral direction).

Also, in the case of the so-called tenter method, it is driven by linear The method drives the jaw portion to perform a smooth extension, and it is preferable to reduce the risk of breakage or the like.

The width of the film forming step is maintained or extended in the transverse direction It is best to carry out by tentering, which can be a needle tenter or a clamper.

Slow axis of cellulose acetate film associated with the present invention (slow axis) or fast axis (fast axis) is present in the plane of the film, When the angle formed by the film width direction and the total length of the film is θ1, θ1 is preferably -1 or more and +1 or less, and more preferably -0.5 or more and +0.5 or less. It is -0.2° or more and +0.2° or less.

This θ1 can be defined as the alignment angle, and the measurement of θ1 can be used. The dynamic birefringence meter KOBRA-21ADH (Prince Measurement Machine) is used. Θ1 satisfies various relationships as described above, can obtain high luminance in display images, and contributes to suppressing or preventing light leakage, and contributes to faithful color reproduction in a color liquid crystal display device.

6) Winding step

Finally, a cellulose acetate film was obtained by winding up the resulting thin strip (finished film). More specifically, after the amount of the residual solvent in the thin strip is 2% by mass or less, the coiler 37 is wound up as a film, and the amount of the residual solvent is 0.4% by mass or less. A film with good stability. In particular, it is preferable to wind up in the range of 0.00 to 0.10% by mass.

In general, the winding method can be used by common people. Moment method, constant stretching method, taper tension method, program tension control method with constant internal stress, etc., can be used.

Before taking up, cut the end at the width of the product and In order to prevent sticking or scratching during rolling, knurling (embossing) can be performed at both ends. The knurling process can be processed by heating or pressurizing a metal ring having a convex and concave pattern on the side. Further, in the grip portion of the jaws at both ends of the film, the film is usually deformed and can be removed because it cannot be used as a product. If the deterioration of the material due to heat is not caused, it can be recycled and reused.

Cellulose acetate film is good for long film, In the case of a body, it is usually about 100m to 10000m, and it is usually a form provided in a roll shape. Further, the width of the film should be 1.4 to 4 m, preferably 1.4 to 4 m, more preferably 1.6 to 3 m, depending on the requirements for the enlargement or production efficiency of the liquid crystal display device.

Cellulose acetate film layer produced by the above method After being packaged and processed at the peripheral portion, it is preferably subjected to a ripening treatment for 3 days or more under conditions of 50 ° C or higher. By imparting such a treatment, the properties such as the planarity of the cellulose acetate film can be improved, and the value within the range is preferably controlled from the viewpoint of improvement in dimensional stability.

[Polarizer]

The polarizer of the main constituent elements of the polarizing plate of the present invention is a representative polarizer-based polyvinyl alcohol-based polarizing film which is known to pass only light of a polarizing surface in a certain direction. In the polyvinyl alcohol-based polarizing film, there is a pair A polyvinyl alcohol-based film is obtained by dyeing iodine and dyeing a dichroic dye. As the polarizer, a polyvinyl alcohol aqueous solution may be used as a film, and after uniaxially stretching and dyeing, or after uniaxially stretching after dyeing, it is preferably a polarizer which is subjected to durability treatment with a boron compound. . The film thickness of the polarizer is preferably 2 to 30 μm, and is preferably 2 to 15 μm from the viewpoint of film suitability, and more preferably 3 to 10 μm from the viewpoint of further film suitability and workability. .

Also, it is also preferable to use the Japanese Patent Laid-Open No. 2003-248123 An ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%, as described in JP-A-2003-342322. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C is preferably used. The polarizer formed by using the ethylene-modified polyvinyl alcohol film is excellent in polarizing performance and durability, and is particularly suitable for a large liquid crystal display device because it has few color spots.

Also, it is better to use the Japanese Special Open 2011-100161 A coating type polarizer is produced by the method described in Japanese Patent No. 4,719, 205, Japanese Patent No. 4,751, 481, and Japanese Patent No. 4,804, 589, and the protective film according to the present invention is bonded to each other to produce a polarizing plate.

[Ultraviolet hardening type adhesive]

In the polarizing plate of the present invention, as shown in FIG. 1, the protective film A and the protective film B described above are respectively separated from the polarizer, preferably by ultraviolet light. A wire-curing adhesive is applied to the laminate.

In the present invention, by applying an ultraviolet curing adhesive The adhesion of the protective film A to the polarizer or the adhesion of the protective film B to the polarizer can provide excellent durability of the polarizer with high productivity.

[Composition of ultraviolet curing type adhesive]

As an ultraviolet curable adhesive composition for a polarizing plate, a photoradical polymerization type composition by photoradical polymerization, a photocationic polymerization type composition by photocationic polymerization, and photo-radical polymerization using a photo-radical polymerization are known. A mixed composition of photocationic polymerization.

The radically polymerizable compound containing a polar group such as a hydroxyl group or a carboxyl group described in JP-A-2008-009329, and a radical polymerizable compound not containing a polar group are known as a photo-radical polymerization type composition. A composition or the like contained in a specific ratio. In particular, the radically polymerizable compound is preferably a "compound having a radically polymerizable ethylenically unsaturated bond". As a preferable example of the compound having a radically polymerizable ethylenically unsaturated bond, a compound having a (meth) acrylonitrile group is contained. Examples of the compound having a (meth)acryl fluorenyl group include an N-substituted (meth) acrylamide-based compound, a (meth) acrylate-based compound, and the like. (Meth) acrylamide refers to acrylamide or methacrylamide.

Further, as a photo-cationic polymerization type composition, an ultraviolet curing type adhesive group as disclosed in, for example, Japanese Laid-Open Patent Publication No. 2011-028234 a product comprising: (α) a cationically polymerizable compound, (β) a photocationic polymerization initiator, (γ) a photosensitizer exhibiting a maximum absorption of light having a long wavelength of 380 nm, and (δ) naphthalene-based photosensitizer. However, an ultraviolet curable adhesive other than this may be used.

(pre-processing steps)

The pretreatment step is a step of subjecting the cellulose ester film to the subsequent surface of the polarizer for easy subsequent processing. When the two sides of the polarizer are respectively bonded to the protective film A and the protective film B, the bonding surfaces of the respective protective films and the polarizers are easily subjected to subsequent processing. As easy processing, for example, corona treatment, plasma treatment, and the like.

(coating step of ultraviolet curing type adhesive)

As a coating step of the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of a polarizer and a bonding surface of the protective film. When the ultraviolet curable adhesive is directly applied to the surface of the polarizer or the protective film, the coating method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a notch coater, and a gravure coater can be used. Further, it is also possible to use a method in which an ultraviolet curable adhesive is cast between a polarizer and a protective film, and then uniformly pressed by a roller or the like.

(Fitting step)

After the ultraviolet curable adhesive is applied by the above method, it is treated by a bonding step. In the bonding step, when the ultraviolet curable adhesive is applied to the surface of the polarizer, for example, in the previous coating step, the protective film is overlaid thereon. In the prior coating step, when a UV-curable adhesive is applied to the surface of the protective film, the polarizer is superimposed thereon. Further, when the ultraviolet curable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film A are superposed in this state. When the protective film A and the protective film B are respectively applied to both sides of the polarizer, and the ultraviolet curable adhesive is used on both surfaces, the ultraviolet protective adhesive is superposed on both sides of the polarizer, and the protective film A is protected. Film B. Then, in this state, when the protective film A is superposed on one side of the polarizer, it is from the side of the polarizer and the side of the protective film A; and when the protective film A and the protective film B are overlapped on both sides of the polarizer, The protective film A and the protective film B side on both sides are sandwiched by a pressurizing roller or the like. The material of the pressure roller can be metal or rubber. The pressure roller disposed on both sides can be the same material or different materials.

(hardening step)

In the hardening step, the uncured ultraviolet curable adhesive is irradiated with ultraviolet rays to harden a compound containing a cationically polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate system). The ultraviolet curable adhesive layer of the compound, the acrylamide compound, or the like, is followed by a polarizer that is superimposed with the ultraviolet curable adhesive and the protective film A or the polarizer and the protective film B. to When the protective film A is bonded to one side of the polarizer, the active energy ray may be irradiated from either the polarizer side or the protective film A side. Further, when the protective film A and the protective film B are bonded to both surfaces of the polarizer, ultraviolet rays are irradiated while the protective film A and the protective film B are superposed on each other on both sides of the polarizer. It is advantageous to harden the ultraviolet curing adhesive on both sides.

The ultraviolet irradiation condition may be any condition as long as it can cure the ultraviolet curable adhesive which is suitable for use in the present invention. The cumulative amount of the ultraviolet irradiation light amount is preferably 50 ~ 1500mJ / cm ^2, more preferably 100 ~ 500mJ / cm ^2.

When the manufacturing process of the polarizing plate is performed in a continuous line, the linear velocity varies depending on the hardening time of the adhesive, but is preferably from 1 to 500 m/min, more preferably from 5 to 300 m/min, still more preferably from 10 to 100 m. /min. When the linear velocity is 1 m/min or more, productivity can be ensured, or damage to the protective film A can be suppressed, and a polarizing plate excellent in durability can be produced. In addition, as long as the linear velocity is 500 m/min or less, the curing of the ultraviolet curable adhesive is sufficient, and an ultraviolet curable adhesive layer having an intended hardness and excellent adhesion can be formed.

Display device

The polarizing plate according to the present invention can be used for various display devices, and is particularly preferably applied to a liquid crystal display device.

Liquid crystal display device having the polarizing plate of the present invention Preferably, it can be used in TN (Twisted Nematic) mode, STN ( Super Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Birefringence), VA (Vertical Alignment) (also includes MVA (Multi-domain Vertical Alignment) or PVA (Patterned Vertical Alignment)), HAN ( HybridAligned Nematic) and so on. In order to improve the contrast, a VA (MVA, PVA) method is preferred.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In the embodiment, the expression "%" is used, and unless otherwise specified, "% by mass" is indicated.

<<Preparation of Acrylic Resin Film as Protective Film A>> [Production of Protective Film A-1; Prescription = Acrylic 1] (film forming film)

First, Technolloy S001 (Tg = 105 ° C, manufactured by Sumitomo Chemical Co., Ltd.) was prepared as an acrylic resin, and melted by heating to 200 ° C. Then, the filtration treatment was carried out in a molten state. Further, the filtration treatment was carried out by using five filters of a stainless steel fiber having a size of 12 inches and a filtration accuracy of 25 μm.

Next, the following components were dried using a vacuum NAUTA mixer at 80 ° C and 133 Pa for 3 hours to obtain a resin composition.

<Resin composition>

The above resin composition was melt-kneaded at 200 ° C using a biaxial extruder and extruded into a strip shape. The resin composition which had been extruded into a strip was water-cooled, and then cut to obtain pellets.

The obtained pellets were dried by a dehumidified air having a temperature of 70 ° C for 5 hours or more, and then the temperature was maintained at a temperature of 100 ° C, and the mixture was placed in a single-screw extruder. The moisture content of the particles fed to the single-axis extruder was 120 ppm.

Using the obtained pellets, a film was produced by a melt casting type film production apparatus. Specifically, the pellet obtained above was melt-kneaded at 200 ° C using a uniaxial extruder, and then extruded from a casting die onto a cooling roller having a surface temperature of 90 ° C. Then, the resin which has been extruded to the cooling roller is pressed by the elastic contact roller having a thickness of 2 mm on the surface of the metal layer, and then cooled by the cooling roller and the cooling roller to obtain a thin strip having a thickness of 60 μm. (web).

Then, both end portions in the width direction of the film were cut to obtain an acrylic resin film having a film thickness of 60 μm, and this was used as the protective film A-1.

[Production of Protective Film A-2]

In the production of the protective film A-1, the cooled and solidified strip was peeled off using a peeling roller so that the thickness of the thin strip was 81 μm. With a roller type stretching device, it was extended at 175 ° C as a stretching ratio of 1.35 times in the conveying direction (MD direction) of the thin strip. The obtained film was introduced into a tenter stretching machine having a preheating zone, an extension zone, a holding zone, and a cooling zone, and further having a neutral zone in each section. Then, it was extended by the tenter stretching machine at 175 ° C as a stretching ratio of 1.35 times in the width direction (TD direction) of the film. Thereafter, the film was cooled until the film temperature became 30 ° C, and the jaws of the stretcher were pulled down. Then, both end portions in the width direction of the film were cut to obtain an acrylic resin film having a film thickness of 60 μm, and this was used as the protective film A-2.

[Production of Protective Film A-3; Prescription = Acrylic 2]

In the production of the protective film A-2, in addition to the filtration treatment of the acrylic resin (Technolloy S001), the protective film was produced by using five filters of a stainless steel fiber having a size of 7 μm and a filtration precision of 25 μm. The production of A-2 was carried out in the same manner to obtain an acrylic resin film, and was used as the protective film A-3.

[Production of Protective Film A-4~A-12]

In the production of the protective film A-2, the stretching ratio in the conveyance direction (MD direction) of the thin strip, the stretching ratio in the width direction (TD direction), and the film thickness are changed as described in Table 1, and the protection is performed. The film A-2 was produced in the same manner to produce acrylic resin films A-4 to A-12.

[Preparation of Protective Film A-13; Prescription = Acrylic 3]

In the production of the protective film A-1, an acrylic resin film A-13 was produced in the same manner as in the production of the protective film A-1 except that Dianal BR-80 (manufactured by Mitsubishi Rayon Co., Ltd.) was used instead of Technolloy S001.

[Preparation of Protective Film A-14; Prescription = Acrylic 4]

In the production of the protective film A-1, acrylic resin was produced in the same manner as in the production of the protective film A-1 except that the "lactone containing a lactone ring" obtained by the following method was used instead of Technolloy S001. Film A-14.

(Manufacture of acrylic resin containing lactone ring)

2,500 g of 2-hydroxyethyl acrylate, 7500 g of methyl methacrylate, and 3,800 g of methyl isobutyl ketone (MIBK) were placed in a 30 L reactor equipped with a stirring device, a temperature sensor, a cooling tube, and a nitrogen introduction tube. Methyl ethyl ketone (MEK) was 950 g, and the initial monomer concentration was set to 68% by weight. The temperature of the nitrogen was simultaneously raised to 100 ° C, and 4.4 g of t-butyl peroxyisopropyl carbonate as a starter was added while refluxing, and it took 4 hours to drip off the tert-butyl peroxyisopropyl carbonate. A solution of 6.4 g of an ester, 280 g of MIBK, and 70 g of MEK was simultaneously subjected to solution polymerization under reflux (about 95 ° C to 110 ° C), and it took 4 hours to carry out the aging. In this case, the polymer concentration in the solution is 45% by weight or less, and between 2 hours and 4 hours after the start of the polymerization reaction, at a rate of 2500 g/hr, and between 4 hours and 7 hours later. At 1600g/hr The mixed solvent (MIBK: MEK = 4:1) was dropped.

Polymerization in a polymer solution obtained as described above 1 g of the compound (1a), a 0.005 g amount of a mixture of stearyl phosphate/distearyl phosphate (Phoslex A-18 manufactured by Seiko Chemical Co., Ltd.) was added to the polymer solution, and nitrogen was passed under reflux. The cyclization condensation reaction was carried out at 80 to 100 ° C for 5 hours. Next, the polymer solution obtained by the above condensation reaction was introduced into a cylinder temperature of 260 ° C, a rotation number of 100 rpm, and a decompression degree of 13.3 to 400 hPa (10~) at a treatment rate of 2.0 kg/hr in terms of resin amount. Circulation in the extruder in a vented twin-screw extruder (φ=29.75 mm, L/D=30) with a number of rear exhaust ports of 1 and a number of front exhaust ports of 4 (300 mmHg) The condensation reaction and devolatilization are carried out to obtain a lactone ring-containing acrylic resin in a transparent particle shape.

[Preparation of protective film A-15; prescription = PET1] (Manufacture of PET (A))

The temperature of the esterification reactor was raised, and 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged at a time point of reaching 200 ° C, and 0.017 parts by mass of ruthenium trioxide as a catalyst was introduced while stirring, magnesium acetate. 0.064 parts by mass of tetrahydrate and 0.16 parts by mass of triethylamine. Subsequently, the temperature was raised by pressurization, and the pressure esterification reaction was carried out under the conditions of a gauge pressure of 0.34 MPa and 240 ° C. Thereafter, the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, it took 15 minutes to raise the temperature to 260 ° C and added 0.012 parts by mass of trimethyl phosphate. Then, after 15 minutes, a dispersion treatment was carried out using a high-pressure disperser, and the obtained esterification reaction product was obtained after 15 minutes. The mixture was transferred to a polycondensation reaction tank, and subjected to a polycondensation reaction under reduced pressure at 280 °C.

After the end of the polycondensation reaction, the size will be 12 inches. Five pieces of a stainless steel fiber sintered filter having a filtration accuracy of 25 μm were filtered, and the mixture was extruded into a strip shape by a nozzle, and cooled by using cooling water which has been previously subjected to filtration treatment (pore diameter: 1 μm or less). , solidified, and cut into granules (also known as "PET (A)").

(Manufacture of PET (B))

10 parts by mass of dry ultraviolet absorber (2,2'-(1,4-phenylene) bis(4H-3,1-benzoxazinone-4-one), particle-free PET ( A) 90 parts by mass of the mixture, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber (also referred to as "PET (B)") was obtained by using a kneading extruder.

(modulation of the subsequent modified coating liquid)

The transesterification reaction and the polycondensation reaction are carried out by a usual method to prepare 46 mol% of terephthalic acid as a dicarboxylic acid component (to the entire dicarboxylic acid component), 46 mol % of isophthalic acid, and 5 - Aqueous dispersible sulfonate having a composition of 8 mole % of sodium sulfonate isophthalate, 50 mol% of ethylene glycol as a diol component (to the total of the diol component), and 50 mol% of neopentyl glycol Copolymerized polyester resin of acid metal base". Next, 51.4 parts by mass of mixed water, 38 parts by mass of isopropyl alcohol, and 5 parts by mass of n-butyl celecoxime, After 0.06 parts by mass of the ion-based surfactant, the mixture was heated and stirred until it reached 77° C., and 5 parts by mass of the above-mentioned copolymerized polyester resin having a water-dispersible sulfonic acid metal base was added, and stirring was continued until the solid block of the resin disappeared. Thereafter, the aqueous resin dispersion liquid was cooled to room temperature to obtain a uniform water-dispersible copolymerized polyester resin liquid having a solid content concentration of 5.0% by mass. Furthermore, 3 parts by mass of the aggregated cerium oxide particles (Sylysia 310, manufactured by Fuji Silysia Co., Ltd.) was dispersed in 50 parts by mass of water, and then 0.54 parts by mass of the aqueous dispersion of Sylysia 310 was added to the above water-dispersibility. In 99.46 parts by mass of the polymerized polyester resin liquid, 20 parts by mass of water was added while stirring to obtain an adhesive modified coating liquid.

(film forming film)

A polyethylene terephthalate film having a three-layer structure was produced by the following method.

Particle-free PET (A) resin pellets 90 mass 10 parts by weight of the PET (B) resin particles containing the ultraviolet absorber, and dried under reduced pressure (1 Torr) at 135 ° C for 6 hours, and then supplied to an extruder (for the intermediate layer), and further, by a conventional method The PET (A) was dried and supplied to an extruder (for both outer layers), and melted at 285 °C. Each of the two kinds of polymers was filtered twice with a filter material of a stainless steel sintered body (95% intercepted by a nominal filtration precision of 10 μm particles), and laminated by using two types of three-layer bus bar blocks, and extruded by a metal nozzle. After laminating, the film was applied by a static electricity casting method and wound on a casting roll having a surface temperature of 30 ° C to obtain an unstretched film after cooling and solidification. At this time, the thickness of each layer The ratio is 10 (outer layer): 80 (intermediate layer): 10 (outer layer) to adjust the discharge amount of each extruder.

Then, the above-mentioned adhesive modified coating liquid was applied to both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying became 0.08 g/m ² , and then dried at 80 ° C for 20 seconds. .

Using a heated roller group and an infrared heater, it will be shaped The unstretched film having the coating layer was preheated to 145 ° C, and then stretched three times in the traveling direction (MD direction) with a roll group having a peripheral speed difference. Thereafter, the film was introduced into a tenter stretching machine, and the end portion of the film was gripped while being clamped, and introduced into a hot air region at a temperature of 135 ° C to extend 2.5 times in the width direction (TD direction). In this manner, a biaxially oriented PET film having a film thickness of 70 μm was obtained and used as a protective film A-15.

[Preparation of protective film A-16; prescription = PET2]

In the production of the protective film A-15, in addition to the filtration treatment of the polycondensate, five sheets of a filter sintered with a stainless steel fiber having a size of 7 inches and a filtration accuracy of 25 μm were used, and the protective film A-15 was used. The production was carried out in the same manner to obtain a biaxially oriented PET film and to serve as a protective film A-16.

[Production of Protective Film A-17~A-21]

In the production of the protective film A-15, the stretching ratio in the conveyance direction (MD direction) of the thin strip, the stretching ratio in the width direction (TD direction) of the film, and the film thickness are changed as described in Table 1. And protection Film A-15 was produced in the same manner to obtain a biaxially oriented PET film to produce a protective film A-17 to A-21.

[Preparation of protective film A-22; prescription = PET3]

In the production of the protective film A-15, an acrylic resin film A- was produced in the same manner as in the production of the protective film A-15 except that PET (C) obtained by the following method was used instead of PET (A). twenty two.

(Manufacture of PET (C))

In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux cooler, 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, and dimethyl-5-sodium sulfonate were charged. 14.8 parts by mass of acid isophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate, which takes 4 hours from 160 ° C to 220 ° C The transesterification reaction is carried out. Subsequently, the temperature was raised to 255 ° C, and the reaction system was gradually depressurized, and then subjected to a polycondensation reaction under reduced pressure of 30 Pa for 1 hour and 30 minutes. The monomer composition in the obtained polycondensation reactant (polyester resin) is as follows.

[dicarboxylic acid component]

‧ terephthalic acid 49 mol%

‧ isophthalic acid 48 mol%

‧5-sodium sulfonate isophthalic acid 3 mol%

[diol component]

‧Ethylene glycol 40% by mole

‧ diethylene glycol 60 mol%

After completion of the above polycondensation reaction, the polycondensate was subjected to filtration treatment using 5 filters of a stainless steel fiber having a size of 12 inches and a filtration precision of 25 μm, and was extruded into a strip shape by a nozzle, and the use was performed in advance. The cooling water of the filtration treatment (pore diameter: 1 μm or less) was cooled, solidified, and cut into pellets (the obtained one is also referred to as "PET (C)").

[Preparation of protective film A-23; prescription = PET4]

The monomer composition in the "Production of PET (C)" described in the column of the protective film A-22 was changed as follows to obtain PET (D).

[dicarboxylic acid component]

‧ terephthalic acid 48 mol%

‧ isophthalic acid 46 mol%

‧ trimesic acid 3 mol%

‧5-sodium sulfonate isophthalic acid 3 mol%

[diol component]

‧Ethylene glycol 50% by mole

‧ neopentyl glycol 50 mole%

Then, in the production of the protective film A-22, an acrylic resin film A-23 was produced in the same manner as in the production of the protective film A-22 except that the PET (D) obtained above was used instead of the PET (C).

[Evaluation of Tensile Elasticity of Protective Film A]

The acrylic resin film and the PET film as the protective film A produced as described above were each conditioned at 23 ° C and 55% RH for 24 hours, and the modulus of elasticity was measured according to the method described in JIS K7127. As a tensile tester, TENSILON RTC-1225 manufactured by Orientec Co., Ltd. was used, and the shape of the test piece was 100 mm (vertical) × 10 mm (width), and the gap between the chucks was 50 mm (25 mm above and below the chuck) to hold up and down. The test speed was carried out at 100 mm/min. Further, it was measured that the MD direction and the TD direction were measured five times for each sample, and the average value of each direction was calculated. The results are shown in Table 1 below.

[Evaluation of haze change of protective film A]

The acrylic resin film and the PET film as the protective film A produced above were allowed to stand in an environment of 80 ° C and 90% RH for 24 hours, and the change in the haze value at this time (the increase in the haze value) was measured. . In addition, the haze value was measured using a haze meter NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd. The results are shown in Table 1 below.

<<Preparation of Cellulose Acetate Film as Protective Film B>> [Production of Protective Film B-1] (modulation of fine particle dispersion dilution)

10 parts by mass of Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd., primary average particle diameter: 16 nm, apparent specific gravity: 90 g/L), and 90 parts by mass of ethanol were stirred and mixed with a dissolving rod for 30 minutes, and then Manton Gaulin using a high-pressure disperser was used. It is dispersed to prepare a fine particle dispersion.

While 88 parts by mass of dichloromethane was added to the obtained fine particle dispersion, the mixture was stirred, and stirred and mixed with a dissolution bar for 30 minutes, and then diluted. The obtained solution was filtered using a Polypropylene Winder Cartridge Filter (TCW-PPS-1N) manufactured by Advantech Toyo Co., Ltd. to obtain fine particle dispersion. Diluent.

(modulation of in-line addition liquid)

15 parts by mass of Tinuvin 928 (manufactured by BASF Japan Co., Ltd.) and 100 parts by mass of methylene chloride as an ultraviolet absorber were placed in a sealed container, heated and stirred, completely dissolved, and then filtered. While adding 36 parts by mass of the fine particle dispersion diluent to the obtained solution, the mixture was stirred and further stirred for 30 minutes, and then 6 parts by mass of cellulose ester 1 was added (the degree of substitution of ethyl ketone was 2.80, Mn = 75,000, Mw=150000 and Mw/Mn=2.0) were stirred and further stirred for 60 minutes. The obtained solution was filtered using Finemet NF manufactured by Nippon Seisaku Co., Ltd. to obtain an in-line addition liquid. The filter material is a nominal filtration accuracy of 20 μm.

(modulation of dope)

The following components were placed in a closed container, and completely dissolved by heating and stirring. The obtained solution was filtered using a filter paper No. 24 made of a filter paper (strand) to obtain a main dope.

<Composition of main concentrated liquid>

100 parts by mass of the main dope and 2.5 parts by mass of the incoming line The addition liquid was sufficiently mixed using an in-line mixer (Toray static in-line mixer Hi-Mixer, SWJ) to obtain a dope.

(film forming step)

The obtained dope was uniformly cast on a stainless steel belt support using a belt casting apparatus under the conditions of a liquid temperature of the concentrated liquid of 35 ° C and a width of 1.95 m. On the stainless steel belt support, the organic solvent in the obtained concentrated liquid film was evaporated to form a thin strip so that the amount of the residual solvent was 30% by mass, and then the thin strip was peeled off from the stainless steel belt support. The obtained thin strip was further dried at 35 ° C, and then cut into strips having a width of 1.90 m. Thereafter, the strip was stretched by 1.3 times in the TD direction (the width direction of the film) at 160 ° C using a tenter. Further, the amount of residual solvent of the thin strip at the start of the extension in the TD direction was 3% by mass.

Thereafter, the obtained film is in the drying apparatus as a majority While the roller was being conveyed, it was dried at 120 ° C for 15 minutes, and then cut into strips having a width of 1.6 m to obtain a cellulose acetate film. Applying at the end Grain processing. Then, a long-length cellulose acetate film having a width of 1.6 m, a length of 6000 m, and a thickness of 40 μm obtained by the above operation was taken up in the longitudinal direction to obtain a laminated roll body 1 of a cellulose acetate film. .

(packaging of laminated roller bodies)

Thereafter, the periphery of the laminated roll body 1 is double-packed with a moisture-proof film packaging material on which a thickness of 50 μm is deposited on a polyethylene resin film, and the end of the core is fixed by a rubber wheel to form a layer. Roller body 1A.

[Production of Protective Film B-2~B-25]

In the production of the protective film B-1, the degree of substitution of the cellulose acetate, the type of the retardation increasing agent, the type of the plasticizer, and the stretching ratio in the TD direction were changed as described in Table 2, and the protection was carried out. Film B-1 was formed into protective films B-2 to B-25 in the same manner. Further, the rising agent 2 to the rising agent 12 described in Table 2 are the following compounds.

[Evaluation of hysteresis of protective film B]

With respect to the protective film B produced as described above, AXOSCAN (Axometrics) was used to measure the hysteresis value Ro in the in-plane direction and the hysteresis value Rt in the thickness direction, respectively. The results are shown in Table 2 below.

[Evaluation of Photoelastic Coefficient of Protective Film B]

The protective film B prepared above was stored in an environment of 23 ° C and 55% RH for 24 hours, and then stretched in a specified direction (MD direction or TD direction) of the film in an environment of 23 ° C and 55% RH. In the state of the load, the hysteresis value Ro of the in-plane direction of the film at a wavelength of 589 nm was measured using a KOBRA-31PRW (Prince Measurement Machine (Unit)).

Then, stepwise increase the tensile load applied to the film The hysteresis value Ro of the in-plane direction of the film under each tensile load was measured at the same time. Then, the hysteresis value Ro in the in-plane direction under each tensile load is divided by the thickness d of the film to calculate Δn (= nx - ny). Further, the horizontal axis is the tensile load and the vertical axis is Δn (=nx-ny), and the tensile load-Δn curve is obtained, and the obtained curve is taken as the straight line when the line is approximated. The slope value is used to calculate the photoelastic coefficient. The results are shown in Table 2 below.

"The production of polarizing plates" [Production of polarizer]

A polyvinyl alcohol film having a thickness of 2400 and a saponification degree of 99.9 mol% and having a thickness of 50 μm was immersed in warm water of 30 ° C for 60 seconds to swell. Next, the obtained film is immersed in iodine/potassium iodide (mass ratio) =0.5/8) In an aqueous solution having a concentration of 0.3%, the dyeing was carried out while extending to 3.0 times. Thereafter, the obtained film was stretched in a boric acid aqueous solution at 65 ° C so that the total stretching ratio became 5.5. Thereafter, the obtained film was dried in an oven at 40 ° C for 3 minutes to obtain a polarizer having a thickness of 10 μm.

[Adjust the preparation of the liquid] (Modulation of ultraviolet curable adhesive liquid 1 : aliphatic epoxy compound)

10.0 g of triglycidyl ether of trimethylolpropane of an aliphatic epoxy compound, and 4.0 g of a photocationic polymerization initiator of a Japanese Caoda Co., Ltd., and a system of "Cota" 1.0 g of the brand name "CS7001" of the photosensitizer was mixed and defoamed to prepare an ultraviolet curable adhesive liquid 1 made of a curable resin composition containing an epoxy resin.

(Modulation of ultraviolet curable adhesive liquid 2: alicyclic epoxy compound)

In the preparation of the ultraviolet curable adhesive liquid 1, except that 4-methyl-7-oxabicyclo[4.1.0]heptane-3-carboxylic acid (=(4-methyl-7-oxadiene) is used. In the same manner as in the preparation of the ultraviolet curable adhesive liquid 1 except that 10.0 g of a tris-glycidyl ether of trimethylolpropane was substituted for 10.0 g of the ring [4.1.0]heptan-3-yl)methyl) Hardening type adhesive solution 2.

(Preparation of ultraviolet curable adhesive liquid 3: combination of aliphatic ‧ alicyclic epoxy compounds)

In the preparation of the ultraviolet curable adhesive liquid 1, except for the use of trimethylolpropane triglycidyl ether 5.0 g and 4-methyl-7-oxabicyclo[4.1.0]heptane-3-carboxylic acid (=(4-methyl-7-oxabicyclo[4.1.0]heptan-3-yl)methyl) 5.0 g to replace trimethylolpropane triglycidyl ether 10.0 g, and ultraviolet curing The preparation of the type adhesive liquid 1 is the same to prepare the ultraviolet curable adhesive liquid 3.

(Preparation of ultraviolet curable adhesive liquid 4: radical polymerizable compound)

38.3 g of hydroxyethyl acrylamide (manufactured by Xingren Co., Ltd.), Aronix M-220 (tripropylene glycol diacrylate, manufactured by Toagosei Co., Ltd.), 19.1 g of a radically polymerizable compound, and propylene fluorene. 38.3g, a photopolymerization initiator, KAYACUREDETX-S (diethyl thioxanthone, manufactured by Nippon Kayaku Co., Ltd.) 1.4g and IRGACURE 907 (2-methyl-1-(4-methylthiobenzene) Ultraviolet-curing adhesive liquid prepared from a curable resin composition containing a radical polymerizable compound, prepared by dissolving and defoaming 1.4 g of 2-morpholinopropan-1-one (manufactured by BASF Corporation) 4.

(Adjustment of the liquid 5: aqueous polyvinyl alcohol solution)

An aqueous solution of 2.5% by mass of polyvinyl alcohol was prepared to form an adhesive liquid 5.

[Production of polarizing plate] (production of polarizing plate 1)

The polarizing plate 1 (101) formed by the configuration shown in Fig. 1 was produced by the following method. The numerical values in parentheses are numbers indicating the respective constituent elements shown in Fig. 1.

First, as the protective film B (105), the above is used. The protective film B-16 was produced, and the surface was subjected to a corona discharge treatment. Further, the conditions of the corona discharge treatment were set to a corona output intensity of 2.0 kW and a linear velocity of 18 m/min. Then, on the corona discharge treatment surface of the protective film B (105), the ultraviolet curable adhesive liquid 1 prepared as described above is applied by bar coating so that the film thickness after curing is about 3 μm. A photo-curable resin layer (103B) is formed. The polyvinyl alcohol-iodine-based polarizer (104, thickness: 10 μm) produced above was bonded to the obtained photocurable resin layer (103B).

Next, as the protective film A (102), the above is used. The protective film A-1 (acrylic resin film) was produced, and the surface was subjected to corona discharge treatment. Further, the conditions of the corona discharge treatment were set to a corona output intensity of 2.0 kW and a speed of 18 m/min.

Next, the corona discharge treatment of the protective film A (102) On the surface, the ultraviolet curable adhesive liquid 1 prepared as described above was applied by bar coating so that the film thickness after curing was about 3 μm, and an ultraviolet curable adhesive layer (103A) was formed.

Single-sided polarized light that has been bonded to the protective film B (105) The sub-layer (104) is bonded to the ultraviolet curable adhesive layer (103A) to obtain a protective film A (acrylic resin film, 102) laminated/ A laminate of an ultraviolet curable adhesive layer (103A) / a polarizer (104) / an ultraviolet curable adhesive layer (103B) / a protective film B (cellulose acetate film, 105). At this time, the slow axis of the protective film B (105) and the absorption axis of the polarizer (104) are bonded to each other so as to be perpendicular to each other.

Using an ultraviolet irradiation device with a belt conveyor (D-bulb manufactured by Fusion UV Systems Co., Ltd.), ultraviolet rays were irradiated from both sides of the laminate so that the cumulative amount of light became 750 mJ/cm ² . The ultraviolet curable adhesive layer (103A, 103B) is cured to prepare a polarizing plate 1 (101).

[Production of Polarizing Plate 2~54]

In the production of the polarizing plate 1 described above, the polarizing plates 2 to 54 were produced in the same manner except that the type of the protective film A, the type of the protective film B, and the type of the adhesive liquid were changed by changing the combinations described in the following Table 3. .

[Production of Liquid Crystal Display Device]

The polarizing plate on the viewing side of the VA liquid crystal display device is peeled off, and the polarizing plate prepared as described above is placed on the viewing side (T1) and the protective film B at the position of the protective film B on the liquid crystal cell. In the side of the cell (T2), the VA liquid crystal display devices 1 to 54 corresponding to the respective polarizing plates 1 to 54 are formed by laminating the adhesive with butyl acrylate as a main component.

[Evaluation of polarizing plate]

With respect to the VA liquid crystal display devices 1 to 54 produced as described above, the degree of light leakage and warpage (curl) after the thermal shock durability test or the high temperature and high humidity test was evaluated according to the method described below. The results are shown in Table 3 below.

(thermal shock durability test)

The display device was placed in a thermostatic chamber and set to 1 cycle at -40 ° C (30 minutes) → 90 ° C (30 minutes), and 50 cycles were performed.

(High temperature and high humidity durability test)

The display device was placed at 75 ° C, 95% for 100 hours.

(evaluation of light leakage)

The display device after performing the above-described thermal shock durability test and the high-temperature and high-humidity durability test was used to make a full black display, and the light leakage at this time was visually observed, and the light leakage was evaluated in accordance with the following criteria.

◎: It is completely impossible to confirm the light leakage by visual inspection.

○: It is almost impossible to confirm the light leakage by visual inspection.

△: Although light leakage can be confirmed by visual observation, it is used as a product without problems.

×: Light leakage can be clearly confirmed by visual inspection, and it is problematic to use as a product.

(Evaluation of warpage (curl) of the panel)

The shape of the warp (curl) of the panel of the display device after the above-described thermal shock endurance test and the high-temperature and high-humidity durability test was visually observed, and the curl was evaluated in accordance with the following criteria.

◎: almost flat and no curl was confirmed

○: Although the occurrence of weak curl was confirmed, the practical quality was no problem.

△: The occurrence of significant curl was confirmed, and the curling property which was difficult to handle was confirmed.

×: Severely curled state, and the operation is extremely difficult quality

As shown in the results in Table 3, it is clear that compared to the comparison In the case where the polarizing plate of the present invention is a protective film A (protective film on the side of the viewing side), which is a film containing acrylic resin or polyester as a main component, even a thermal shock is used. After the durability test or the high-temperature and high-humidity durability test, problems such as light leakage at the inner end portion of the polarizing plate or warpage of the panel due to curling of the polarizing plate can be suppressed.

[Production of Protective Film B-26~B-31]

In the production of the protective film B-16, the same amount as the protective film B-16 was used except that the amount of addition of the hysteresis rising agent (increased agent 5) and the stretching ratio in the TD direction were changed as described in Table 4. To make protective film B-26~B-31. Then, the hysteresis value Ro in the in-plane direction, the hysteresis value Rt in the thickness direction, and the photoelastic coefficient were measured for the protective film B thus produced by the same method as described above. The results are shown in Table 4 below.

[Production of polarizing plate 55~60]

In the production of the polarizing plate 5 described above, the protective film B is changed to the protective film B-26 to B-31 produced as described above, and is produced in the same manner. Polarizer 55~60.

[Production of Liquid Crystal Display Devices 55 to 60]

The VA liquid crystal display devices 55 to 60 respectively corresponding to the polarizing plates 55 to 60 are produced by the same method as described above. Then, the degree of light leakage and warpage (curl) after the thermal shock durability test or the high-temperature high-humidity test was evaluated for each of the liquid crystal display devices 55 to 60 produced by the same method as described above. The results are shown in Table 5 below.

As is clear from the results shown in Table 5, the film thickness of the protective film B is preferably from 12 to 60 μm, more preferably from 15 to 40 μm, most preferably from 15 to 30 μm.

The present application is based on Japanese Patent Application No. 2013-239352, filed on Nov. 19, 2013, which is hereby incorporated by reference.

Claims (12)

A polarizing plate which has a protective film A, a polarizer and a protective film B in this order, and the protective film A and the protective film B are polarizing plates which are bonded to the polarizer using an ultraviolet curing adhesive. The protective film A is a film containing an acrylic resin or a polyester as a main component, and the protective film B is composed of a cellulose acetate having an average ethyl ketone group substitution degree of 2.1 to 2.7 as a main component. a cellulose acetate film of a hysteresis-increasing agent, which is a compound having a 5-membered aromatic heterocyclic ring containing only a nitrogen atom as a hetero atom other than a carbon atom forming an aromatic ring; The difference between the longitudinal and lateral directions of the photoelastic coefficient (23 ° C 55% RH) of the acetate film (absolute value of the value obtained by subtracting the value in the TD direction from the value in the MD direction) is 5.0 or less. The polarizing plate of claim 1, wherein in the protective film B, the photoelastic coefficient in the MD direction is larger than the photoelastic coefficient in the TD direction. The polarizing plate of claim 1 or 2, wherein the protective film A has a film thickness of 55 to 80 μm. The polarizing plate of claim 1 or 2, wherein the protective film A has an absolute difference in tensile modulus (23 ° C 55% RH) in the MD direction and tensile modulus (23 ° C 55% RH) in the TD direction. The value is 500 MPa or less. The polarizing plate of claim 1 or 2, wherein the protective film A is allowed to stand under conditions of 80 ° C and 90% RH for 24 hours, and the change in haze value at this time is 0.5 or less. The polarizing plate of claim 1 or 2, wherein the protective film A is made of an acrylic resin as a main component. The polarizing plate of claim 1 or 2, wherein the protective film A is made of polyethylene terephthalate as a main component. The polarizing plate of claim 1 or 2, wherein the hysteresis rising agent comprises a hysteresis rise of at least one selected from the group consisting of a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, and a tetrazole ring. Agent. The polarizing plate of claim 1 or 2, wherein the hysteresis rising agent comprises at least one hysteresis rising agent selected from the group consisting of a pyrazole ring, an imidazole ring and a triazole ring. The polarizing plate of claim 1 or 2, wherein the cellulose acetate ester constituting the protective film B has a degree of substitution of the ethyl thiol group of 2.5 to 2.7. The polarizing plate of claim 1 or 2, wherein the ultraviolet curable adhesive is a mixture of an alicyclic epoxy compound and an aliphatic chain epoxy compound. A VA type liquid crystal display device comprising the polarizing plate of any one of claims 1 to 11.