TW201539061A - Method for producing polarizable laminated film and polarizing plate - Google Patents

Abstract

The present invention provides a method for producing a polarizable laminated film, comprising: a step of forming a polyvinyl alcohol resin layer on a surface of a base film to obtain a laminated film, a step of elongating the laminated film to obtain an elongated film; a step of dying the polyvinyl alcohol resin layer of the elongated film by dichroic dye to produce a polarizer layer, thereby obtaining a polarizable laminated film; wherein the arithmetic mean roughness Ra0 of the base film surface on which the polyvinyl alcohol resin layer will be formed is 30 nm or less. In addition, the present invention provides a method for producing polarizing plate, comprising: a step of laminating a first protection film on a surface of the polarizer layer of the obtained polarizable laminated film opposite to the base film, and a step of peering the base film.

Description

Polarizing laminated film and method for producing polarizing plate

The present invention relates to a method for producing a polarizing laminate film and a method for producing a polarizing plate. Further, the present invention relates to a polarizing plate obtained by the manufacturing method and a display device including the polarizing plate.

The polarizing plate is widely used for display devices such as liquid crystal display devices, and has been widely used in recent years for flat televisions or various mobile devices. In the case of a polarizing plate, a member made of a protective film made of a thermoplastic resin is usually bonded to one side or both sides of a polarizer.

With the popularity of flat-panel televisions or mobile devices, the requirements for thinning of polarizing plates are also increasing. A method of producing a polarizing plate having a polarizing film of a film is known as a method of using a substrate film as described in the specification of the present invention (for example, Japanese Laid-Open Patent Publication No. 2011-128486 (Patent Document 1) Japanese Patent Publication No. 2013-186389 (Patent Document 2)].

The coating method generally comprises the steps of: forming a resin layer on a substrate film by coating; forming a polarizer layer by stretching and dyeing the resin layer to obtain a polarizer layer; a step of attaching a protective film to the polarizer layer of the polarizing laminated film; The step of peeling off the base film after bonding the protective film. According to this method, since the polarizing plate layer or even the polarizing plate can be easily thinned, the polarizing plate layer of the film and the resin layer as the precursor thereof are always supported by the substrate film or the protective film without being supported by the substrate film or the protective film. It will be used in the form of a monomer, so the film in the step is rational.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-128486

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2013-186389

For the polarizing plate, in order to ensure its stability against a sharp temperature difference which may be exposed when mounted on a display device or the like, its durability against a heat shock test is required. The hot and cold blasting test is exposed to a high temperature environment (for example, about 70 to 85 ° C) for a certain period of time after exposure to a low temperature environment (for example, about 40 to -30 ° C) for a certain period of time, and the test of the interactive operation is repeated. The above-mentioned certain period of time is usually 30 to 60 minutes, and when "low temperature → high temperature →" is set to one cycle, it is usually repeated for 50 to 400 cycles.

However, according to the investigation by the inventors of the present invention, when the polarizing plate having the protective film on the polarizing plate layer is subjected to the hot and cold pressing test, especially when the polarizing plate is manufactured by using the base film as in the above-described coating method, Resistant to temperature changes, resulting in easy occurrence of polarizing layers Bad situation that will break (hereinafter, this bad condition is also called "cracking"). The problem of the cracking is to thin the polarizing layer in order to achieve the requirement for thinning of the polarizing plate, or to adhere to one or both sides of the polarizing plate in order to achieve the requirement of thinning the polarizing plate. The protective film (especially a film having a low rigidity such as a thermoplastic resin film) is thinned, and as a result, the effect of the polarizing layer layer-reinforcing effect by the protective film is particularly weak.

An object of the present invention is to provide a method for producing a polarizing laminate film which is formed by forming a polarizing layer on a substrate film as in the above-described coating method to form a polarizing laminate film, and is produced by using the polarizing laminate film. In the method of polarizing plate, a polarizing plate which is not easily cracked in a cold and hot stamping test can be provided.

Another object of the present invention is to provide a method of manufacturing a polarizing plate which is less prone to cracking in a hot and cold wash test. A still further object is to provide a polarizing plate and a display device using the same, which are less likely to be cracked during the hot and cold wash test, and have high durability against a sharp temperature difference.

The present invention is based on the findings of the present inventors as follows. In other words, the inventors of the present invention have found that a polarizing laminate film is formed on a base film to form a polarizing laminate film, and a protective film is bonded to the polarizer layer, and then the base film is peeled off and removed. In the polarizing plate, the crack generated on the polarizer layer is mainly caused by minute irregularities on the surface of the polarizer layer exposed by peeling off of the base film, and the unevenness is received by the base film. Generated by the influence of the surface state on the side of the polarizer layer.

In other words, in the method for producing a substrate film, the surface shape of the polarizer layer side exposed by the peeling of the base film is unavoidably affected by the shape of the surface of the polarizer layer side of the base film. When the surface shape of the base film is reflected, the surface shape of the base film is reflected, and the surface smoothness of the polarizer layer side exposed by peeling off the base film is impaired, and the arithmetic mean roughness is made. When Ra ₁ exceeds a specific value, or the difference between the arithmetic mean roughness Ra ₁ and the arithmetic mean roughness Ra ₂ of the polarizer layer on the side of the protective film exceeds a specific value, it is likely to be caused by the surface in the cold heat test. Cracking of the bumps.

The present invention has been made based on the above knowledge, and provides a method for producing a polarizing laminated film, a method for producing a polarizing plate, a polarizing plate, and a display device.

[1] A method for producing a polarizing laminated film, comprising the steps of: forming a polyvinyl alcohol-based resin layer on a substrate film surface to obtain a laminated film; and extending the laminated film to obtain a stretched film; a step of obtaining a polarizing layer film by dyeing a polyvinyl alcohol-based resin layer of the above-mentioned stretched film with a dichroic dye to obtain a polarizing laminated film; wherein a base film surface of the polyvinyl alcohol-based resin layer is to be formed The arithmetic mean roughness Ra ₀ is 130 nm or less.

[2] The method for producing a polarizing laminated film according to the above aspect, wherein the polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin.

[3] A method of producing a polarizing plate, comprising the steps of: manufacturing a polarizing laminated film according to [1] or [2], wherein the polarizing plate layer is opposite to the substrate film a step of bonding the first protective film to the side surface; and a step of peeling off the base material film.

[4] The method for producing a polarizing plate according to the above [3], wherein the arithmetic mean roughness Ra of the surface which is formed by peeling off the base film in the polarizing plate obtained by peeling off the base film ₁ is 55 nm or less.

[5] The method for producing a polarizing plate according to the above [4], wherein, in the polarizing plate obtained by peeling off the base film, arithmetic of a surface which is revealed by peeling off of the base film The difference between the average thickness Ra ₁ and the arithmetic mean roughness Ra ₂ of the surface of the polarizer layer constituting the polarizing laminate film on the opposite side to the base film is 15 nm or less.

The method of producing a polarizing plate according to any one of the above aspects, wherein the polarizing layer constituting the polarizing laminated film has a thickness of 10 μm or less.

[7] The method for producing a polarizing plate according to any one of [3], wherein the first protective film is a thermoplastic resin film.

[8] The method for producing a polarizing plate according to any one of [3] to [7] further comprising the step of: peeling off the base film by using the base material film; The step of peeling off the film and revealing the surface of the second protective film made of a thermoplastic resin.

[9] A polarizing plate which is provided by any one of [3] to [8] The method for producing a polarizing plate according to the item is obtained.

[10] The polarizing plate according to [9], which has an adhesive layer laminated on at least one side.

[11] A display device comprising: the polarizing plate according to [9] or [10].

According to the present invention, since the polarizing laminate film is produced according to a predetermined method and the polarizing plate is used to manufacture the polarizing plate, it is possible to provide cracking which is less likely to occur in the hot and cold wash test and has high durability against a sharp temperature difference. Polarizer and display device.

1‧‧‧ polarizing plate with protective film on one side

2‧‧‧ polarizing plates with protective film on both sides

5‧‧‧Polarized film

6‧‧‧Polyvinyl alcohol resin layer

6'‧‧‧Extended polyvinyl alcohol resin layer

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

30‧‧‧Base film

30'‧‧‧Extended substrate film

100‧‧‧ laminated film

200‧‧‧Extension film

300‧‧‧Polarized laminated film

400‧‧‧Polarized laminated film with protective film

Fig. 1 is a flow chart showing a method for producing a polarizing laminated film of the present invention and a method for producing a polarizing plate.

Fig. 2 is a schematic cross-sectional view showing an example of a layer structure of a laminated film obtained by a resin layer forming step.

Fig. 3 is a schematic cross-sectional view showing an example of a layer structure of a stretched film obtained by an extending step.

Fig. 4 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing laminate film obtained by a dyeing step.

Fig. 5 is a schematic cross-sectional view showing an example of a layer structure of a polarizing laminated film with a protective film obtained by the first protective film bonding step.

Fig. 6 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate having a protective film on one side obtained by a peeling step.

Fig. 7 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate having a protective film on both sides obtained by the second protective film bonding step.

<Method for Producing Polarized Laminated Film>

Referring to Fig. 1, a polarizing laminated film which is a manufacturing intermediate of a polarizing plate is produced by a method comprising the steps of forming a resin layer of a laminated film by forming a polyvinyl alcohol-based resin layer on at least one surface of a base film. Step S10 is formed; a step of stretching the laminated film to obtain a stretched film, and a step of dyeing the polyvinyl alcohol-based resin layer of the stretched film to form a polarizing plate layer to obtain a polarizing laminated film.

In addition, the polarizing laminated film in the present invention refers to a substrate having a base film and a polarizing layer laminated on at least one surface thereof, and the protective film is not bonded. The polarizing laminated film in which the first protective film is bonded to the polarizing plate layer by the first protective film bonding work S40 is also referred to as "in order to distinguish it from the polarizing laminated film." A polarizing laminate film with a protective film.

(1) Resin layer forming step S10

Referring to Fig. 2, this step is a step of forming a laminated film 100 by forming a polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30. This polyvinyl alcohol-based resin layer 6 is a layer in which the polarizing plate layer 5 is formed by the extending step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one surface or both surfaces of the base film 30 and drying the coating layer.

The base film 30 may be composed of a thermoplastic resin, and is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation. Specific examples of such a thermoplastic resin may include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (norbornene resin); a polyester resin; (meth)acrylic resin; cellulose ester resin such as cellulose triacetate or cellulose diacetate; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; Polyarylate resin; polystyrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures and copolymers thereof.

The base film 30 may have a single layer structure formed of one or more resin layers composed of one or two or more thermoplastic resins, or may be a resin layer composed of one or two or more thermoplastic resins. Multi-layered structure with multiple layers. When the laminated film 100 is extended in the extending step S20 described later, the base film 30 is preferably made of a resin which is extensible at an extending temperature suitable for extending the polyvinyl alcohol-based resin layer 6.

The substrate film 30 may contain an additive. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color preventives, flame retardants, nucleating agents, antistatic agents, pigments, and color formers. The content of the thermoplastic resin in the substrate film 30 is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, still more preferably from 70 to 97% by weight. good.

The thickness of the base film 30 is usually from 1 to 500 μm, and preferably from 1 to 300 μm, in terms of workability such as strength and handleability. More preferably from 5 to 200 μm, still more preferably from 5 to 150 μm.

In the present invention, the arithmetic mean roughness Ra ₀ of the surface of the base film 30 on which the polyvinyl alcohol-based resin layer 6 is formed (which may be one surface or both surfaces of the base film 30) is 130 nm or less. By adjusting the arithmetic mean roughness Ra ₀ to this range, the surface on the side of the polarizer layer of the polarizing plate obtained by the later-described manufacturing method using the polarizing laminated film can be smoothly smoothed, so that the above-mentioned unevenness can be effectively suppressed. Cracking of the polarizer layer 5. From the viewpoint of suppressing cracking more effectively, the arithmetic mean roughness Ra ₀ is preferably 120 nm or less, more preferably 100 nm or less, and still more preferably 80 nm or less.

The arithmetic mean roughness Ra ₀ (the same applies to Ra ₁ and Ra ₂ described later) is defined by the surface roughness defined by JIS B 0601-2001. According to this, it is possible to regard the arithmetic mean roughness as the surface unevenness and/or the larger one. The arithmetic mean roughness is usually calculated by finding the difference between the average heights of the points, so it is a statistical value in terms of length (mainly nm). The arithmetic mean roughness can be easily obtained by, for example, obtaining a surface image using a conjugated focus microscope such as PL μ 2300 sold by Sensofar Japan Co., Ltd., and performing statistical processing using the attached software.

Specific examples of the method of adjusting the arithmetic mean roughness Ra _{0 of the} base film 30 to 130 nm or less are as follows, but are not limited to these examples.

[A] When the base film 30 is formed by extrusion molding, the difference between the resin melting temperature at the time of extrusion and the temperature of the cooling roll used for cooling the molten film is expanded. By increasing the temperature difference, the amount of temperature change during film cooling is increased, and the rapid cooling system is advantageous for reducing the arithmetic mean thickness. degree. The resin melt temperature is set to be high to the extent that the resin is not deteriorated or the excessive viscosity is lowered, and the cooling roller is cooled as much as possible to expand the temperature difference.

In particular, when a crystalline thermoplastic resin is used, since crystallization is caused during cooling, it is advantageous to reduce the arithmetic mean roughness by suppressing crystal growth by rapid cooling. Although it may vary depending on the type of the thermoplastic resin to be used, the above temperature difference is preferably 100 ° C or more, more preferably 240 ° C or more, and still more preferably more than 240 ° C. Even when a non-crystalline thermoplastic resin is used, the cooling process of the resin greatly affects the surface unevenness of the base film 30, so the temperature difference should be as large as possible.

[B] Reduce the amount of nucleating agent or other additives added. When a crystalline thermoplastic resin is used, it is widely known that in many cases, a substance called a nucleating agent is added, which is a crystal nucleus for controlling crystal growth. This nucleating agent is suitable for improving the handleability or heat resistance because it imparts rigidity to the base film 30. However, when it is excessively added, the amount of crystals formed during extrusion becomes extremely large, and as a result, it is easy to be on the substrate film. 30 causes surface irregularities. Therefore, the amount of the nucleating agent added is preferably 2% by weight or less (when the thermoplastic resin is 100%). Since other additives such as an antioxidant, an ultraviolet absorber, a lubricating material, and a matting agent may also affect the surface unevenness, the amount thereof is preferably 20% by weight or less.

[C] Adjust the surface roughness of the cooling roll, and the like. When the surface roughness of the cooling roll is increased by the matte treatment or the like, irregularities are likely to occur on the surface of the base film that is in contact therewith. Therefore, in the use of a cooling roll having a low surface roughness, When a cooling roll having a high surface roughness is used, it is preferable that the base film surface opposite to the side in contact with the cooling roll is a surface on which the polyvinyl alcohol-based resin layer 6 is formed. When the polyvinyl alcohol-based resin layer 6 is formed on both surfaces of the base film 30, it is preferable to use a cooling roll having a low surface roughness. The arithmetic mean thickness of the substrate film surface on the side opposite to the side on which the cooling roll is contacted can be adjusted, for example, by the amount of air or wind speed between the molten resin extruded from the extrusion die and the contact with the cooling roll. And reduce it.

[D] When the base film 30 is formed by a casting method, the surface roughness of the support for casting and the like are adjusted. A stainless steel belt or a mirror roll can be used as the support, and the higher the smoothness of the surface, the more advantageous the reduction of the arithmetic mean roughness. The arithmetic mean roughness of the substrate film surface on the opposite side to the support side is largely dependent on the drying conditions after casting, and the evaporation rate of the solvent can be adjusted, for example, by selection of a solvent or optimization of a drying apparatus. Make it less.

Next, the coating liquid applied on the base film 30 will be described. The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. Examples of the derivative of the polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, and the like, and, for example, the polyvinyl alcohol resin is modified with an olefin such as ethylene or propylene. Those who have been modified by unsaturated carboxylic acids such as acrylic acid, methacrylic acid, or crotonic acid; those modified by alkyl esters of unsaturated carboxylic acids; those modified by (meth) acrylamide. The proportion of the modification is preferably less than 30% by mole, and more preferably less than 10% by mole. When proceeding When the modification is more than 30 mol%, it becomes difficult to adsorb the dichroic dye, and the problem of lowering the polarizing performance may occur. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

Moreover, "(meth)acrylic acid" in this specification means the thing chosen from at least one of acrylic acid and methacrylic acid. "(Meth)acrylonitrile" is also the same.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10,000, more preferably in the range of 1,000 to 10,000, still more preferably in the range of 1,500 to 8,000, and most preferably 2,000 to 5,000. The average degree of polymerization can be determined in accordance with the method specified in JIS K6726-1994 "Testing methods for polyvinyl alcohol". When the average degree of polymerization is less than 100, it will be difficult to obtain good polarizing properties, and if it exceeds 10,000, the solubility in a solvent will be deteriorated, so that it is difficult to form the polyvinyl alcohol-based resin layer 6.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The degree of saponification is in the range of 80 mol% or more, preferably 90 mol% or more, and more preferably 94 mol% or more. When the degree of saponification is too low, it is possible to make the polarizing laminated film or even the water resistance or the moist heat resistance when forming the polarizing plate insufficient. In addition, although it may be a completely saponified product (the degree of saponification is 100% by mole), if the degree of saponification is too high, the dyeing speed will be slow, and if sufficient polarizing performance is to be imparted, the manufacturing time will be lengthened, or A polarizer layer having sufficient polarizing properties cannot be obtained depending on the situation. Therefore, the degree of saponification is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

The degree of saponification is expressed by the unit ratio (% by mole), and the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin is changed to a hydroxyl group by saponification treatment. The ratio can be defined by the following formula: degree of saponification (% by mole) = [(hydroxyl number) ÷ (hydroxyl number + number of acetate groups)] × 100

The degree of saponification can be determined in accordance with JIS K6726 (1994). The higher the degree of saponification, the higher the proportion of the hydroxyl group, indicating that the proportion of the acetate group which hinders crystallization is lower.

In the case of the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer such as vinyl acetate and another monomer copolymerizable therewith may be exemplified. . Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The coating liquid may also contain an additive such as a plasticizer or a surfactant as needed. As the plasticizer, a polyhydric alcohol or a condensate thereof or the like can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol, and the like. The amount of the additive to be added is preferably 20% by weight or less based on the polyvinyl alcohol-based resin.

The method of applying the above coating liquid to the base film 30 may be suitably selected from the following methods: a wire bar coating method; a roll coating method such as a trans coating method or a gravure coating method; a die coating method; a comma coating method; (comma coat); lip coating method; spin coating method; screen coating method; fountain coating method; dip coating method;

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set in accordance with the type of solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, and preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or more.

The polyvinyl alcohol-based resin layer 6 may be formed only on one surface of the base film 30 or may be formed on both surfaces. When formed on both sides, since two polarizing plates can be obtained from one polarizing laminated film 300, the production efficiency of the polarizing plate is also favored.

The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, more preferably 5 to 20 μm. When the polyvinyl alcohol-based resin layer 6 having the thickness in this range is obtained, the dyeing property of the dichroic dye can be obtained by the extending step S20 and the dyeing step S30 which will be described later, and the polarizing property is excellent and thin (for example, thickness). The polarizer layer 5 of 10 μm or less). When the thickness of the polyvinyl alcohol-based resin layer 6 is less than 3 μm, it tends to be too thin after stretching, and the dyeability tends to be deteriorated.

Before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, it is also possible to apply at least on the surface of the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed. Corona treatment, plasma treatment, flame treatment, etc.

Further, before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, a polyethylene layer may be formed on the base film 30 via a primer layer. The alcohol resin layer 6.

The substrate layer can be formed by applying a coating liquid for forming a substrate layer onto the surface of the base film 30 and then drying it. Substratum formation The coating liquid contains a component that exerts a certain degree of strong force on both the base film 30 and the polyvinyl alcohol-based resin layer 6 . The coating liquid for forming a substrate layer usually contains a resin component and a solvent which impart such adhesion. The resin component is preferably a thermoplastic resin which is excellent in transparency, heat stability, and elongation, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol resin. Among them, a polyvinyl alcohol-based resin which imparts a good adhesion is suitable. More preferred is a polyvinyl alcohol resin. The solvent is usually a general organic solvent or an aqueous solvent which can dissolve the above-mentioned resin component, and it is preferred to form a substrate layer with a coating liquid containing water as a solvent.

In order to increase the strength of the underlayer, a crosslinking agent may be added to the coating liquid for forming a substrate. The crosslinking agent is suitably selected from known ones such as an organic system and an inorganic system, depending on the type of the thermoplastic resin to be used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, and organometallic compounds) and polymer-based crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component forming the underlayer, a polyamide solvent, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, or the like can be used.

The thickness of the substrate layer is preferably from about 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the adhesion improving effect between the base film 30 and the polyvinyl alcohol-based resin layer 6 is reduced, and when it is thicker than 1 μm, it is disadvantageous for thinning of the polarizing plate.

The method of applying the coating liquid for forming an underlayer layer on the base film 30 can be similar to the coating liquid for forming a polyvinyl alcohol-based resin layer. The substrate layer is coated on the surface on which the coating liquid for forming a polyvinyl alcohol-based resin layer is applied. The drying temperature of the coating layer composed of the coating liquid for forming a substrate layer is, for example, 50 to 200 ° C, and preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or more.

(2) Extension step S20

Referring to Fig. 3, in this step, the laminated film 100 composed of the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched to obtain the stretched base film 30' and the polyvinyl alcohol-based resin layer 6'. The step of stretching the film 200 is constructed. The extension process is usually a one-axis extension.

The stretching ratio of the laminated film 100 can be appropriately selected in accordance with the required polarizing characteristics, and is preferably more than 5 times and 17 times or less with respect to the original length of the laminated film 100, and more than 5 times and 8 times or less. Better. When the stretching ratio is 5 or less, the polyvinyl alcohol-based resin layer 6' cannot be sufficiently aligned, so that the degree of polarization of the polarizing plate layer 5 cannot be sufficiently increased. On the other hand, when the stretching ratio exceeds 17 times, the film is easily broken at the time of stretching, and the thickness of the stretched film 200 is made thinner than necessary, and the workability and handleability in the subsequent step are lowered. Hey.

The extension process is not limited to one-stage extension, and can also be extended in multiple stages. At this time, the multi-stage stretching treatment may be continuously performed before the dyeing step S30, or the stretching treatment after the second stage may be simultaneously performed with the dyeing treatment and/or the crosslinking treatment in the dyeing step S30. When the stretching treatment is carried out in a plurality of stages, it is preferable to carry out the stretching treatment so that the total elongation of the entire length of the stretching treatment exceeds 5 times.

The stretching treatment may be a longitudinal stretching extending in the longitudinal direction of the film (film conveying direction), or a lateral stretching or oblique stretching extending in the width direction of the film. The longitudinal stretching method includes, for example, stretching between rolls by a roll, compression and extension, extension by a chuck, that is, a clip, and the like, and a tenter method may be used. Although the stretching treatment may employ either a wet stretching method or a dry stretching method, it is preferable to use a dry stretching method from the viewpoint of wide selection of the stretching temperature.

The elongation temperature is set to a temperature at which the entire polyvinyl alcohol-based resin layer 6 and the base film 30 are more extensible, and the phase transition temperature (melting point or glass transition temperature) of the base film 30 is set. The range of -30 ° C to +30 ° C is preferred, and the range of -30 ° C to +5 ° C is more preferable, and the range of -25 ° C to +0 ° C is more preferable. When the base film 30 is composed of a plurality of resin layers, the phase transition temperature is the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

When the stretching temperature is lower than -30 ° C of the phase transition temperature, it is difficult to achieve a high-magnification extension of more than 5 times, or the fluidity of the base film 30 is too low, and the elongation treatment tends to be difficult. When the stretching temperature exceeds +30 ° C of the phase transition temperature, the fluidity of the base film 30 is excessively increased, and the elongation treatment tends to be difficult. In order to more easily achieve a high stretching ratio of more than 5 times, the stretching temperature is within the above range, and preferably 120 ° C or more.

The heating method of the laminated film 100 in the stretching process is, for example, a zone heating method (for example, adding, for example, blowing into a hot air to adjust to a predetermined temperature) Heating method in the extension zone like a hot furnace. A method of heating the roller itself when extending by a roller, a heater heating method (a method of providing an infrared heater, a halogen heater, a plate heater, or the like on the upper and lower sides of the laminated film 100 by radiant heat). In the inter-roller stretching method, the area heating method is preferred from the viewpoint of the uniformity of the stretching temperature.

The preheating step of the preheating laminated film 100 may also be provided before the extending step S20. The preheating method can utilize the same method as the heating method in the elongation treatment. The preheating temperature is preferably in the range of -50 ° C to ± 0 ° C of the elongation temperature, and more preferably in the range of -40 ° C to -10 ° C in the elongation temperature.

Further, after the extension processing in the extending step S20, a heat fixing processing step may also be provided. In the heat-fixing treatment, the heat treatment is performed at a temperature higher than the crystallization temperature while maintaining the tension state while holding the end portion of the stretched film 200 with a clip. The crystallization of the polyvinyl alcohol-based resin layer 6' is promoted by the heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0 ° C to -80 ° C of the elongation temperature, and more preferably in the range of -0 ° C to -50 ° C of the elongation temperature.

(3) Dyeing step S30

Referring to Fig. 4, this step is a step of dyeing and aligning the polyvinyl alcohol-based resin layer 6' of the stretched film 200 with a dichroic dye to form a polarizer layer 5. Through this step, a polarizing laminated film 300 in which the polarizing plate layer 5 is laminated on one surface or both surfaces of the base film 30' is obtained. As the dichroic dye, iodine or a dichroic organic dye can be specifically used.

a dyeing step by immersing the stretch film 200 as a whole It is carried out in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. The solvent of the dyeing solution can usually be water, but an organic solvent compatible with water can also be added. The concentration of the dichroic dye in the dyeing solution is preferably from 0.01 to 10% by weight, more preferably from 0.02 to 7% by weight, still more preferably from 0.025 to 5% by weight.

When iodine is used as the dichroic dye, in order to further improve the dyeing efficiency, it is preferred to further add the iodide to the dye solution containing iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to iodide is preferably in the range of 1:5 to 1:100 by weight, and more preferably in the range of 1:6 to 1:80, and 1:7 to 1:70. The scope is even better. The temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

Further, although the dyeing step S30 may be performed before the stretching step S20, or the steps may be simultaneously performed, the dichroic dye adsorbed on the polyvinyl alcohol-based resin layer may be well aligned, so that the laminated film 10 is applied. It is preferred to carry out the dyeing step S30 after at least some extent of the stretching treatment. That is, in addition to the stretching film 200 which is subjected to the stretching process to the target magnification in the extending step S20, the stretching film 200 may be supplied to the dyeing step S30, and the stretching step S20 may be performed after the stretching process below the target magnification. The extension process is applied in step S30 until the total stretch ratio becomes the target magnification until. In the latter embodiment, after the stretching process of the target magnification is performed in the extending step S20, the stretching process is performed in the dyeing process of the dyeing step S30 so that the total stretching ratio becomes the target magnification. Or, as described later, when the cross-linking treatment is performed after the dyeing treatment, 2) after the stretching treatment lower than the target magnification is performed in the extending step S20, the total stretching ratio is not reached in the dyeing treatment of the dyeing project S30. The extension process of the degree of the target magnification is performed, and then, in the cross-linking process, the state in which the total stretch ratio becomes the target magnification is finally performed.

In the dyeing step S30, a crosslinking treatment step performed after the dyeing treatment may be included. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, a conventionally known one can be used, and examples thereof include a boron compound such as boric acid and borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

The crosslinking solution may specifically be a solution in which the crosslinking agent is dissolved in a solvent. The solvent may be, for example, water, but may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, more preferably in the range of 6 to 15% by weight.

The crosslinking solution may contain an iodide. By the addition of iodide, the in-plane polarizing performance of the polarizer layer 5 can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight. The temperature of the cross-linking solution is 10 to 90 ° C The range is good.

The crosslinking treatment can also be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the dyeing solution. Further, the stretching treatment can also be performed in the crosslinking treatment. The specific aspect in which the elongation treatment is carried out in the crosslinking treatment is as described above. Further, it is also possible to carry out the treatment of immersing in the crosslinking solution twice or more using a crosslinking solution of two or more different compositions.

After the dyeing step S30, it is preferable to perform the washing step and the drying step before the first protective film bonding step S40 to be described later. The washing step usually involves a water washing step. The water washing treatment can be carried out by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 to 50 ° C and preferably in the range of from 4 to 20 ° C. The washing step may also be a combination of a water washing step and a step of washing with an iodide solution.

The drying step performed after the washing step may be any suitable method such as natural drying, air drying, and heat drying. For example, in the case of heat drying, the drying temperature is usually from 20 to 95 °C.

The thickness of the polarizer layer 5 having the polarizing laminate film 300 is, for example, 30 μm or less, and may be 20 μm or less. However, from the viewpoint of reducing the thickness of the polarizing plate, it is preferably 10 μm or less, and more preferably 8 μm or less. The thickness of the polarizer layer 5 is usually 2 μm or more.

The arithmetic mean roughness Ra ₂ of the surface of the polarizer layer 5 of the polarizing layer film 30 opposite to the base film 30 ′ is applied to the base film 30 by applying a coating liquid containing a polyvinyl alcohol resin. When the polarizer layer 5 is formed by the stretching and dyeing steps, it is usually 55 nm or less, and more typically about 40 nm or less.

<Method of Manufacturing Polarizing Plate>

With reference to Fig. 1, the method for producing a polarizing plate of the present invention includes the steps of: bonding the surface of the polarizing layer of the polarizing laminated film produced by the above method to the side opposite to the substrate film. The first protective film bonding step S40 of the first protective film; and the peeling step S50 of peeling off the base film.

After the first protective film bonding step S40 and the peeling step S50, a polarizing plate having a protective film attached to one surface of the first protective film on one surface of the polarizer layer is obtained. Further, as shown in Fig. 1, after the peeling step S50, a surface of the polarizing plate having the protective film on one side may be removed by peeling off the base film (hereinafter, this surface is also referred to as "stripping". In the second protective film bonding step S60 to which the second protective film is bonded, a polarizing plate having a protective film on both sides thereof is obtained.

A polarizing plate is produced by using a polarizing laminate film in which a polarizing plate layer is formed on a surface having an arithmetic mean roughness Ra ₀ of 130 nm or less on the base film 30 by the above-described production method (one side or both sides are attached) The polarizing plate of the protective film can obtain a polarizing plate which is less likely to be cracked in the cold heat test and has high durability against a sharp temperature difference.

Here, the cracking of the polarizer layer and the effect of suppressing cracking of the present invention will be described in more detail. When the cold heat is repeated in the hot and cold wash test, the layers of the polarizing plate composed of the plastic polymer are repeatedly stretched and contracted due to thermal expansion. Further, since the protective film or the like has a skew at the time of molding, or When the polymer is aligned, the relaxation behavior is also added, so the size of the film itself gradually changes (usually shrinks) after each cycle. Further, in the polarizing plate layer, in addition to expansion and contraction due to thermal expansion, the contraction due to the relaxation of the alignment or the cross-linking shrinkage due to boric acid may also operate, so that it strongly contracts itself.

The polarizing plate in the hot and cold blasting test is caused by the contraction force of the polarizing film layer which is about to contract, and the skew caused by the inconsistent action of the layers disposed around it, so that a very high internal stress is generated in each repetition cycle. . The cracking of the polarizer layer is a problem in which the polarizing plate layer is broken by the alignment direction of the highly aligned polyvinyl alcohol resin due to the internal stress.

Among the factors of the cracking, in addition to the shrinkage stress of the polarizer layer itself, a glass substrate to which a polarizing plate is bonded, such as a protective film and a test, is also exemplified (a liquid crystal cell (assuming a practical liquid) Crystal cell), etc., such as display cells, etc.) (such as the nature of such surrounding members), but the inventors have found that most of the cases in which cracking actually occurs must be due to such factors. The generated internal stress is specifically concentrated so that the defect portion which becomes the crack initiation point exists in the polarizing plate, and the surface unevenness of the peeling surface of the polarizing plate can form the above-mentioned defect portion. When such a defective portion exists, cracking may occur even if the internal stress is low.

Although it is not intended to limit the scope of the present invention, the surface unevenness of the peeling surface of the polarizing plate is a mechanism for causing cracking as a starting point, and it is estimated that it is as follows. When there is more than the thickness of the polarizer layer on the peeling surface In the case of a small unevenness, when a protective film is bonded to the surface thereof by an adhesive or a glass substrate is bonded to the surface thereof via an adhesive layer, it may be small that cannot be detected by a naked eye or a defect detector. The void area. Since the size of the void portion is as small as several μm, it is considered that the portion of the polarizing plate layer forming the void portion maintains the shrinkage stress of the polarizing plate layer. On the other hand, in the case where there is a void portion, since the reinforcing effect of the protective film or the glass substrate via the adhesive layer or the adhesive layer is not obtained, it is considered that the polarized plate exists as a particularly weak portion. Therefore, it becomes a starting point for easy cracking. In actuality, when the cross section of the polarizing plate which has been cracked is analyzed by a scanning electron microscope or the like, a void portion of about several μm can be detected in the cracked portion. As described above, since the void portion is not detectable by the naked eye or the defect detector or the like, it is difficult to take measures to remove the polarizing plate having the void portion as a defective product.

If according to the present invention, by forming the arithmetic mean roughness of the base film surface of the polarizing sheet becomes Ra ₀ 130nm or less, the peeled surface of the polarizing plate of the arithmetic average roughness Ra ₁ of the resulting polarization becomes close configuration The arithmetic mean roughness Ra ₂ of the surface of the polarizer layer of the laminated film opposite to the substrate film, that is, the arithmetic mean roughness Ra _{1 can be} made small, so that the thickness of the polarizer layer is, for example, 10 μm or less. The film can also suppress the occurrence of voids which are easily detected as described above and which are likely to be the starting point of cracking.

In addition, when a polarizing layer is formed on a base film to form a polarizing laminate film, and a protective film is bonded to the polarizer layer, and the base film is peeled off and removed, a surface of the peeling surface is produced. The state is inevitably affected by the surface state of the substrate film, which is in the above patent It is also mentioned in the literature 2. However, the invention described in Patent Document 2 mainly focuses on foreign matter (dust, etc.) or scratches which are present on the surface or inside of the base film and which is large enough to be discernible, and which are generated by reflection. The polarizer or the scratched polarizer layer faces the side opposite to the display unit to construct the display device. Further, in the invention described in Patent Document 2, the problem is not that the polarizing sheet layer is cracked, but the unevenness or scratch of the polarizing sheet layer is a bright spot, and the visibility of the display device is lowered, and the suppression is not provided. Invention of a method of embossing or scratching.

Further, as a result of investigation by the present inventors, it has been found that a defect (for example, a foreign matter) of several tens of μm or more which is as large as the identifiable degree does not become a defective portion which provides a crack initiation point. This is because the defect of tens of μm or more in the polarizer layer of the film (for example, 10 μm or less) is substituted for most or all of the polarizer layer in the thickness direction of the polarizer layer, and is in the defect portion. There is almost no polarizing layer, so it is presumed that the shrinkage stress of the polarizing layer itself in the defect portion may not work at all or become very small. On the other hand, in the present invention, microscopic surface irregularities (for example, minute surface irregularities of 50 μm or less and irregularities of nano-scale fine surface irregularities) which are not tens of μm indistinguishable from the surface are concerned, regardless of the surface. The arrangement on the side of the glass substrate or on the opposite side of the glass substrate is a cracking factor in the thermal shock test.

(1) First protective film bonding step S40

With reference to Fig. 5, in this step, the first protective film 10 is bonded to the surface of the polarizing layer 5 of the polarizing laminated film 300 on the side opposite to the base film 30' via the first adhesive layer 15 to obtain Polarized laminated film with protective film Steps of 400. When the polarizing laminate film 300 has the polarizer layer 5 on both surfaces of the base film 30', the protective film is usually bonded to the polarizing layer 5 on both surfaces. In this case, the protective film may be the same kind of protective film or a different protective film.

The material constituting the first protective film 10 is preferably a thermoplastic resin having light transmissivity (preferably, optical transparency), and examples of such a resin include a chain polyolefin resin (polypropylene system). a polyolefin resin such as a resin or the like, a cyclic polyolefin resin (such as a decene-based resin); a cellulose ester resin such as cellulose triacetate or cellulose diacetate; or a polyester resin; A polycarbonate resin; a (meth)acrylic resin; a polystyrene resin; or a mixture or a copolymer thereof.

The first protective film 10 may be a protective film having an optical function such as a retardation film or a brightness enhancement film. For example, a retardation film to which an arbitrary retardation value is imparted can be obtained by stretching a film composed of the above thermoplastic resin (one-axis stretching or biaxial stretching or the like) or forming a liquid crystal layer or the like on the film.

The chain-like polyolefin resin may, for example, be a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, and may be a copolymer composed of two or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include, for example, a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene. (representatively a random copolymer) and such unsaturated carboxylic acids A graft polymer modified by a derivative thereof or a derivative thereof, and the like. Among them, a norbornene-based resin obtained by using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is preferred.

A cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, it is also possible to use such co-polymers or to modify partial hydroxyl groups via other substituents. Among these, cellulose triacetate (i.e., triacetate cellulose: TAC) is particularly preferred.

The polyester resin is a resin having an ester bond, and is usually composed of a polycondensate of a polybasic acid or a derivative thereof and a polyhydric alcohol. As the polybasic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. Wait. As the polyol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl alcohol, and cyclohexane dimethanol.

Specific examples of the polyester resin include: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyterephthalic acid Propylene glycol, propylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

The polycarbonate resin is composed of a polymer in which a monomer unit is bonded via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate such as a modified polymer skeleton, or a copolymerized polycarbonate or the like.

The (meth)acrylic resin is a resin mainly composed of a compound having a (meth)acryl fluorenyl group. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methacrylic acid Ester-(meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymer (MS resin, etc.); a copolymer of methyl acrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl (meth) acrylate) Copolymer, etc.). It is preferred to use a polymer having a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate as a main component, and methyl methacrylate as a main component (50 to 100% by weight). More preferably, the methyl methacrylate resin is preferably 70 to 100% by weight.

Moreover, the description of each of the thermoplastic resins shown above can also be applied to the thermoplastic resin constituting the base film 30.

On the surface of the first protective film 10 opposite to the polarizer layer 5, a surface treatment layer such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer may be formed. (coating layer). The method of forming the surface treatment layer on the surface of the protective film is not particularly limited, and a known method can be used.

In view of the reduction in thickness of the polarizing plate, the thickness of the first protective film 10 is preferably thin, but if it is too thin, the strength is lowered to deteriorate the workability. Therefore, the thickness of the first protective film 10 is preferably 5 to 90 μm or less, more preferably 5 to 60 μm, and still more preferably 5 to 50 μm. Even if the thickness of the first protective film 10 is 30 μm or less, the crack of the polarizer layer in the thermal shock test can be effectively suppressed by the present invention.

As the adhesive for forming the first adhesive layer 15, for example, an aqueous adhesive or a photocurable adhesive can be used. The aqueous adhesive agent may, for example, be an adhesive composed of a polyvinyl alcohol-based resin aqueous solution or an aqueous two-component urethane-based emulsion adhesive. In particular, when a cellulose ester-based resin film which has been subjected to surface treatment (hydrophilization treatment) such as saponification treatment is used as the first protective film 10, an aqueous binder composed of a polyvinyl alcohol-based resin aqueous solution is preferably used.

In the case of a polyvinyl alcohol-based resin, in addition to a vinyl alcohol homopolymer obtained by subjecting a polyvinyl acetate which is a homopolymer of vinyl acetate to saponification, vinyl acetate may be used together with it. A polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of another monomer of the polymerization, or a modified polyvinyl alcohol-based polymer having a partially modified hydroxyl group. The aqueous binder may contain an additive such as a polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, or a zinc compound.

The aqueous adhesive is applied to the bonding surface of the polarizing plate layer 5 and/or the first protective film 10 of the polarizing laminated film 300, and these films are bonded via the adhesive layer, preferably by using a bonding film. The roller or the like is pressed and adhered to perform a bonding step. The coating method of the aqueous adhesive (the same applies to the photocurable adhesive) is not particularly limited, and a casting method, a mayer bar coating method, a gravure coating method, a comma coating method, or the like can be used. Conventionally known methods such as a doctor blade method, a die coating method, a dip coating method, and a spray method.

When an aqueous adhesive is used, after performing the above-mentioned bonding, a drying step of drying the film is preferably performed to remove moisture contained in the aqueous adhesive. Drying can be carried out, for example, by introducing the film into a drying oven. The drying temperature (temperature of the drying oven) is preferably from 30 to 90 °C. If it is less than 30 ° C, the first protective film 10 tends to be peeled off from the polarizer layer 5 . When the drying temperature exceeds 90 ° C, there is a possibility that the polarizing performance of the polarizing plate layer 5 is deteriorated by heat. The drying time can be set to about 10 to 1,000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

After the drying step, it may be set at a temperature of room temperature or slightly higher than room temperature, for example, a ripening step of about 12 to 600 hours at a temperature of about 20 to 45 °C. The ripening temperature is usually set to be lower than the drying temperature.

The photocurable adhesive agent is an adhesive which can be cured by irradiation with light such as ultraviolet rays, and includes, for example, a polymerizable compound and a photopolymerization initiator, a photoreactive resin, and a binder resin. Binder resin) and photoreactive crosslinkers. The polymerizable compound is, for example, a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, or a photocurable urethane monomer, or a photopolymerizable single Bulk oligomer. The photopolymerization initiator may be one which contains an active species such as a neutral radical, an anionic radical, or a cationic radical by irradiation with light such as ultraviolet rays. The photocurable adhesive containing a polymerizable compound and a photopolymerization initiator is preferably a photocurable epoxy-based monomer and a photocationic polymerization initiator.

When a photocurable adhesive is used, after the bonding is carried out, a drying step (when the photocurable adhesive contains a solvent, etc.) is carried out in accordance with the demand, and then a curing step of curing the photocurable adhesive by irradiation with light is performed. . The light to be irradiated is not particularly limited, but preferably has a light-emitting distribution at a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light, and a microwave-excited mercury lamp are used. A metal halide lamp or the like is preferable as the light source.

When the first protective film 10 is bonded to the polarizer layer 5, the bonding surface of the first protective film 10 can be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment. Adhesive treatment) to improve adhesion to the polarizer layer 5, wherein plasma treatment, corona treatment or saponification treatment is preferred. For example, when the first protective film 10 is composed of a cyclic polyolefin resin, it is usually subjected to plasma treatment or corona treatment. Further, when it is composed of a cellulose ester-based resin, it is usually subjected to a saponification treatment. The saponification treatment may be exemplified by immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

(2) Stripping step S50

Referring to Fig. 6, this step is a step of peeling off the base film 30' after the first protective film bonding step S40. In this step, a polarizing plate 1 having a protective film on one side is obtained. When the polarizing laminate film 300 has the polarizer layer 5 on both surfaces of the base film 30', and when the polarizer layer 5 is bonded to the protective film, the film is removed from the film by the peeling step S50. The polarizing laminated film 300 obtained two sheets of polarizing plates 1 with a protective film on one side.

The method of peeling off the base film 30' is not particularly The limitation can be carried out in the same manner as the peeling step of a separator (release film) which is performed on a usual polarizing plate with an adhesive. The base film 30' may be directly peeled off immediately after the first protective film bonding step S40, or may be wound into a wheel shape once after the first protective film bonding step S40, and then rolled up by the subsequent steps. Stripped out on one side.

According to the present invention, since the polarizing laminated film 300 is produced by using the base film 30 having the arithmetic mean roughness Ra ₀ of the surface on which the polarizing plate layer 5 is formed, and the polarizing plate is used, the polarizing plate can be used. The arithmetic mean roughness Ra _{1 of the} peeling surface is close to the arithmetic mean roughness Ra ₂ of the surface of the polarizing layer 5 constituting the polarizing laminated film 300 opposite to the base film 30', that is, the arithmetic mean roughness Ra ₁ A smaller polarizing plate 1 with a protective film on one side. The polarizing plate 1 having a protective film on one side thereof is less likely to be cracked in the thermal shock test, and has high durability against a sharp temperature difference.

From the viewpoint of effectively suppressing cracking, the difference between the arithmetic mean roughness Ra ₁ and the arithmetic mean roughness Ra ₂ is preferably 15 nm or less, and more preferably 12 nm or less. For the same reason, the arithmetic mean roughness Ra ₁ is preferably 55 nm or less, and more preferably 50 nm or less.

<Second protective film bonding step S50>

With reference to the first and seventh figures, the double-sided attachment can be obtained by performing the step of bonding the second protective film 20 via the second adhesive layer 25 on the peeling surface of the polarizing plate 1 having the protective film on one side. A polarizing plate 2 having a protective film. The polarizing plate 2 having the protective film on both sides thereof is also less likely to be cracked in the thermal shock test, and has high durability against a sharp temperature difference.

The second protective film 20 and the second adhesive bonded thereto The layer 25 is described with reference to the first protective film 10 and the first adhesive layer 15. The first protective film 10 and the second protective film 20 may be the same type of protective film or a different type of protective film. The first adhesive layer 15 and the second adhesive layer 25 may be formed of an adhesive of the same kind, or may be formed of a different type of adhesive.

The polarizing plate 1 having a protective film on one side and the polarizing plate 2 having a protective film on both sides thereof can be bonded to a peripheral member to form a composite polarizing plate, or can be used as such a composite polarizing plate. The peripheral member may be a protective film for damage prevention attached to the protective film; and the laminate may be laminated on the protective film (for example, when the polarizing plate 2 having the protective film is attached) or the polarizing plate layer 5 (for example) An adhesive layer for attaching a polarizing plate to a display unit or other optical member when the polarizing plate 1 having a protective film is attached to one side; a spacer film laminated on the outer surface of the adhesive layer; An optical compensation film such as a retardation film or other optical function on the film (for example, when the polarizing plate 2 having the protective film is provided on both sides) or on the polarizing plate layer 5 (for example, when the polarizing plate 1 having the protective film is provided on one side) Sex film.

The adhesive layer of an example of the peripheral member can be laminated on the outer surface of any of the protective films when the polarizing plate 2 having the protective film is attached to both sides, and can be laminated on, for example, the peeling surface when the polarizing plate 1 having the protective film on one side thereof is laminated. . The adhesive for forming the adhesive layer is usually a (meth)acrylic resin, a styrene resin, a silicone resin or the like as a matrix polymer, and an isocyanate compound or an epoxy compound is added thereto. And an adhesive composition of a crosslinking agent such as an aziridine compound. Further, fine particles may be further contained to form an adhesive layer which exhibits light scattering properties. The thickness of the adhesive layer is usually from 1 to 40 μm, preferably from 3 to 25 μm.

Further, as another example of the optical functional film of the peripheral member, a reflective polarizing film which can polarize light and reflect polarized light having opposite properties to that of the display can be cited; the surface has a concave-convex shape and an anti-glare function a film; a film for preventing surface reflection function; a reflective film having a reflecting function on the surface; a semi-transmissive reflecting film having both a reflecting function and a penetrating function; a viewing angle compensation film.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples and comparative examples, but the invention is not limited to the scope of the examples.

In the following examples and comparative examples, the arithmetic mean roughness Ra was obtained by obtaining a surface image using PL μ 2300 sold by Sensofar Japan Co., Ltd., and then performing statistical processing using the attached software. The lens is 20 times and the observation area is 636.61 μm × 477.25 μm.

<Example 1>

(1) Fabrication of substrate film

A three-layered substrate film is produced by co-extrusion molding using a multilayer extrusion molding machine by using no propylene/ethylene containing about 5% by weight of ethylene units A homopolymer of propylene homopolymer (manufactured by Sumitomo Chemical Co., Ltd.) is disposed on both sides of a resin layer composed of a polymer (Sumitomo Nobrene W151, manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138 °C). A resin layer composed of "Sumitomo Nobrene FLX80E4" and melting point Tm = 163 ° C). Total thickness of substrate film The degree is 90 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) is 3/4/3. No nucleating agent was used.

Since the resin melting temperature at the time of co-extrusion was set to 275 ° C, the temperature of the cold roll used for cooling the molten film was set to 25 ° C, so the temperature difference at the time of cooling was 250 ° C. Further, a film surface side of the base layer of polyvinyl alcohol resin, the arithmetic average roughness Ra ₀ was 55.0nm.

(2) Substrate formation step

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1,100, saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polycondensate having a concentration of 3% by weight. Aqueous vinyl alcohol solution. In the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was added in an amount of 5 parts by weight based on 6 parts by weight of the polyvinyl alcohol powder to obtain a coating liquid for forming an underlayer layer. .

Then, in the above-described (1) making one side of the base film (arithmetic average surface roughness Ra ₀ to 55.0nm) is administered after the corona treatment, using a micro gravure coater on the corona-treated surface The coating liquid for forming an underlayer was dried at 80 ° C for 10 minutes to form a substrate having a thickness of 0.2 μm.

(3) Production of laminated film (resin layer forming step)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2,400, saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%. This aqueous solution is used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The bottom of the base film having the bottom layer produced in the above (2) The coating liquid for forming a polyvinyl alcohol-based resin layer was applied onto the surface of the layer by a lip coater, and then dried at 80 ° C for 20 minutes to form a polyvinyl alcohol-based resin layer on the substrate layer. A laminate film composed of a base film/substrate layer/polyvinyl alcohol-based resin layer.

(4) Production of stretched film (extension step)

With respect to the laminated film produced in the above (3), a 5.8-fold free end uniaxial stretching was carried out at 160 ° C using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the stretched polyvinyl alcohol-based resin layer was 6.2 μm.

(5) Production of polarizing laminated film (dyeing step)

The stretched film prepared in the above (4) was immersed in a dyeing aqueous solution containing 30% by weight of iodine and potassium iodide (containing 0.6 parts by weight of iodine and 10 parts by weight of potassium iodide) for about 180 seconds to carry out a polyvinyl alcohol system. After the dyeing treatment of the resin layer, the excess dyeing aqueous solution was washed with pure water at 10 °C.

Next, it was immersed in a first cross-linked aqueous solution (containing 9.5 parts by weight of boric acid per 100 parts by weight of water) containing boric acid for 120 seconds, and then immersed in a second cross-linked aqueous solution containing 70% of boric acid and potassium iodide. (By 9.5 parts by weight of boric acid and 4 parts by weight of potassium iodide per 100 parts by weight of water), the crosslinking treatment was carried out for 60 seconds. Thereafter, the film was washed with pure water at 10 ° C for 10 seconds, and finally dried at 40 ° C for 300 seconds to obtain a polarizing laminated film composed of a base film/substrate layer/polarizing sheet layer.

When the arithmetic mean roughness Ra ₂ of the surface of the polarizing layer opposite to the base film was measured, the obtained polarizing laminated film was 38.5 nm.

(6) Production of polarizing plate (protective film bonding step and peeling) step)

Polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree: 1,800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. In the obtained aqueous solution, a crosslinking agent ("Sumirez resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed at a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to prepare an aqueous solution of an adhesive.

Then, after applying the aqueous solution of the above-mentioned adhesive agent to the surface of the polarizing layer of the polarizing laminated film produced in the above (5) on the side opposite to the substrate film, the protective film [transparently composed of cellulose triacetate (TAC)) A protective film ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd., thickness: 40 μm) was bonded, and dried in an oven at 80 ° C for 2 minutes to obtain a substrate film/substrate layer/polarizing sheet/adhesive layer. / A polarizing laminated film with a protective film formed of a protective film.

Then, the base film is peeled off from the polarizing laminated film with a protective film. The base film was easily peeled off, and a polarizing plate with a protective film on one side was obtained. The thickness of the polarizer layer was 6.7 μm.

The obtained polarizing plate with a protective film on one side was measured to have an arithmetic mean roughness Ra ₁ of the peeling surface which was observed by peeling off of the base film, and was 38.7 nm. Finally, a (meth)acrylic adhesive layer was provided on the release surface to prepare a polarizing plate with an adhesive layer.

<Example 2>

In addition to the addition of 1% by weight of the nucleating agent composed of high-density polyethylene to the homopolypropylene in the two-layer homopolypropylene layer as the surface layer, A base film was produced in the same manner as in Example 1, and a polarizing plate with an adhesive layer was produced in the same manner as in Example 1 except that the base film was used.

<Example 3>

A base film was produced in the same manner as in Example 1 except that in the two-layer homopolypropylene layer as the surface layer, 2% by weight of a nucleating agent composed of high-density polyethylene was added to the homopolypropylene. In the same manner as in Example 1, except that the base film was used, a polarizing plate with an adhesive layer was produced.

<Comparative Example 1>

The base film was produced in the same manner as in Example 3 except that the resin melting temperature at the time of co-extrusion was set to 265 ° C, and the same operation as in Example 1 was carried out except that the base film was used. A polarizing plate with an adhesive layer is prepared.

<Comparative Example 2>

A base film was produced in the same manner as in Comparative Example 1, except that the nucleating agent composed of high-density polyethylene was added to the two-layer homopolypropylene layer as the surface layer in an amount of 3% by weight based on the homopolypropylene. In the same manner as in Example 1, except that the base film was used, a polarizing plate with an adhesive layer was produced.

<Comparative Example 3>

The base film was produced in the same manner as in Comparative Example 2 except that the resin melting temperature at the time of co-extrusion was set to 260 ° C, and the same operation as in Example 1 was carried out except that the base film was used. Production A polarizing plate with an adhesive layer.

The amount of the nucleating agent added during the production of the base film, the temperature difference at the time of cooling, and the arithmetic mean roughness Ra ₀ , Ra ₁ and Ra _{2 are} summarized in Table 1.

[cold thermal shock test]

The obtained polarizing plate obtained in the examples and the comparative examples was cut into 4.4" size (50 mm × 100 mm), and adhered to the Corning glass using the adhesive layer. 50 pieces of the sample of the laminated glass were prepared and placed in hot and cold heat. In the rinsing tester, the operation was carried out for "30 minutes after holding in a tank at -40 ° C for 30 minutes, and then moving to a tank of 85 ° C for a period of 30 minutes", and a 400-cycle thermal shock test was repeated. The number of cracks in the polarizer layer in 50 samples was visually calculated, and the number of cracks was converted into the number corresponding to 1 m ² . During the test, the sample was taken out after 100 cycles and 250 cycles, and the number of cracks corresponding to 1 m ² was obtained in the same manner. The results are shown in Table 1.

Even if a (meth)acrylic adhesive layer was provided on the protective film side of the obtained polarizing plate with a protective film on one side, a polarizing plate with an adhesive layer was prepared, and the same thermal shock test as described above was carried out. The number of cracks was also substantially the same as Examples 1 to 3 and Comparative Examples 1 to 3, respectively.

Claims (11)

A method for producing a polarizing laminated film, comprising the steps of: forming a polyvinyl alcohol-based resin layer on a surface of a substrate film to obtain a laminated film; and extending the laminated film to obtain a stretched film; and using the laminated film; The dichroic dye is a step of dyeing the polyvinyl alcohol-based resin layer of the stretched film to form a polarizer layer to obtain a polarizing laminate film; wherein the arithmetic mean of the substrate film surface of the polyvinyl alcohol-based resin layer is to be formed. The roughness Ra ₀ is 130 nm or less. The method for producing a polarizing laminated film according to the first aspect of the invention, wherein the polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin. A method for producing a polarizing plate, which comprises the steps of: manufacturing a polarizing laminated film according to claim 1 or 2; and a side of the polarizing layer opposite to the substrate film a step of bonding the first protective film to the surface; and a step of peeling off the base film. The method for producing a polarizing plate according to the third aspect of the invention, wherein, in the polarizing plate obtained by peeling off the base film, an arithmetic mean roughness Ra of a surface which is formed by peeling off the base film ₁ is 55 nm or less. The method for producing a polarizing plate according to the third aspect of the invention, wherein, in the polarizing plate obtained by peeling off the base film, an arithmetic mean thickness of a surface which is formed by peeling off the base film The difference between the degree Ra ₁ and the arithmetic mean roughness Ra ₂ of the surface of the polarizer layer constituting the polarizing laminate film on the opposite side to the base film is an absolute value of 15 nm or less. The method for producing a polarizing plate according to any one of the third to fifth aspect, wherein the polarizing layer constituting the polarizing laminated film has a thickness of 10 μm or less. The method for producing a polarizing plate according to any one of claims 3 to 6, wherein the first protective film is a thermoplastic resin film. The method for producing a polarizing plate according to any one of claims 3 to 7, further comprising the step of: removing the base film by removing the base film; The step of peeling off and exposing the surface to be bonded to the second protective film made of a thermoplastic resin. A polarizing plate obtained by the method for producing a polarizing plate according to any one of claims 3 to 8. The polarizing plate of claim 9, which has an adhesive layer laminated on at least one side. A display device comprising: the polarizing plate of claim 9 or 10.