JP6321999B2 - Manufacturing method of polarizing plate - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate.

  The polarizing plate has been widely used in display devices such as liquid crystal display devices, particularly in thin televisions and various mobile devices in recent years. As a polarizing plate, the thing of the structure which bonded the protective film on the single side | surface or both surfaces of the polarizer using the adhesive agent is common.

  The polarizing plate can be manufactured by a method in which a protective film is bonded to a polarizer (polarizing film) made of a single (single) film via an adhesive layer (hereinafter also referred to as “single film method”). , A step of forming a resin layer on a base film by coating (application); a step of drawing and dyeing this resin layer as a polarizer layer to obtain a polarizing laminate film; on the polarizer layer of the polarizing laminate film It can also manufacture by the method (henceforth a "coating method") including the process of bonding a protective film through an adhesive bond layer; The process of peeling and removing a base film after bonding of a protective film. The latter method is advantageous in that the film is easily handled during the process and that a thin polarizer layer is easily obtained.

  Patent Documents 1 and 2 describe that a polarizing plate is produced by a method similar to the coating method.

JP 2009-0986653 A JP 2009-093074 A

  With the widespread use of flat-screen TVs and mobile devices, the demand for thinner polarizing plates has been increasing in recent years. However, there is a problem that curling tends to occur when the polarizing plate is thinned. When the curl is improperly curled, bubbles are easily caught when the polarizing plate is bonded to a display cell such as a liquid crystal cell by the adhesive layer to form a display device. If such bubbles exist in a display device such as a liquid crystal display device, light scattering occurs when the light is turned on, and light leaks in a black display state (bubbles become bright spots), resulting in a display defect. obtain.

  Patent Documents 1 and 2 describe that curling of a polarizing plate can be suppressed by a method similar to the above-described coating method. However, the polarizing plate in which curling is referred to in these documents is a polarizing plate that is used as a protective film for the polarizer layer without peeling off and removing the base film in the above-described coating method. No mention is made of curling of a polarizing plate comprising a polarizer layer and a protective film, which is obtained by peeling off and removing.

  An object of the present invention is a method for producing a polarizing plate by peeling and removing a base film after pasting a protective film on a polarizer layer of a polarizing laminate film, for example, as in the above-described coating method. Another object of the present invention is to provide a production method capable of suppressing curling of the obtained polarizing plate.

The present invention provides the following method for producing a polarizing plate.
[1] A step of bonding a protective film via an adhesive layer on a polarizer layer of a polarizing laminate film including a polarizer layer on at least one surface of a base film;
Performing a heat treatment under an environment of relative humidity of 25% or more to dry the adhesive layer;
Peeling and removing the base film;
In this order.

[2] The production method according to [1], wherein the adhesive forming the adhesive layer is a water-based adhesive.
[3] The polarizing laminated film is
After applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film, a step of forming a polyvinyl alcohol-based resin layer by drying to obtain a laminated film;
Stretching the laminated film to obtain a stretched film;
A step of obtaining a polarizing laminated film by dyeing a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form the polarizer layer;
The production method according to [1] or [2], which is produced by a method comprising:

  [4] The manufacturing method according to any one of [1] to [3], wherein the protective film is made of a cellulose ester resin or a (meth) acrylic resin.

  [5] The manufacturing method according to any one of [1] to [4], wherein the polarizer layer has a thickness of 10 μm or less.

  According to this invention, after bonding a protective film on the polarizer layer of a light-polarizing laminated film, the base film is peeled and removed, and the protective film is bonded to the polarizer layer and at least one surface thereof. In the method for producing a polarizing plate comprising, curling of the obtained polarizing plate can be suppressed.

It is a flowchart which shows a preferable example of the manufacturing method of the polarizing plate which concerns on this invention. It is a flowchart which shows a preferable example of the manufacturing method of a light-polarizing laminated film. It is a flowchart which shows another preferable example of the manufacturing method of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the laminated | multilayer film obtained at a resin layer formation process. It is a schematic sectional drawing which shows an example of the laminated constitution of the stretched film obtained at a extending process. It is a schematic sectional drawing which shows an example of the laminated constitution of the light-polarizing laminated film obtained at a dyeing process. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing laminated film with a protective film obtained at a 1st protective film bonding process. It is a schematic sectional drawing which shows the layer structure of the polarizing plate with a single-sided protective film obtained by a peeling process. It is a schematic sectional drawing which shows the layer structure of the polarizing plate with a double-sided protective film obtained at a 2nd protective film bonding process.

FIG. 1 is a flowchart showing a preferred example of a method for producing a polarizing plate according to the present invention. As shown in FIG. 1, the production method of the present invention comprises the following steps:
(1) A first protective film laminating step of laminating a first protective film via an adhesive layer on a polarizer layer of a polarizing laminate film having a polarizer layer on at least one surface of a base film. S10,
(2) Drying step S20 for drying the adhesive layer by performing a heat treatment in an environment with a relative humidity of 25% or more,
(3) Peeling step S30 for peeling and removing the base film,
including.

Moreover, as shown in FIG. 2, the polarizing laminated film preferably has the following steps as in the above-described coating method:
[A] A resin layer forming step of forming a polyvinyl alcohol resin layer by applying a coating liquid containing a polyvinyl alcohol resin on at least one surface of a substrate film and then drying to form a laminated film S1-1,
[B] Stretching step S1-2 for stretching a laminated film to obtain a stretched film,
[C] Dyeing step S1-3 for obtaining a polarizing laminated film by dyeing a polyvinyl alcohol resin layer of a stretched film with a dichroic dye to form a polarizer layer,
Manufactured by a method comprising:

  By the above manufacturing method, the polarizing plate with a single-sided protective film by which the 1st protective film was bonded to one side of a polarizer layer is obtained. As shown in FIG. 3, after peeling process S30, 2nd protective film bonding process S40 which bonds a 2nd protective film through the adhesive bond layer to the surface at the side of the polarizer layer of a polarizing plate with a single-sided protective film is carried out. It may be provided to obtain a polarizing plate with a double-sided protective film.

  In addition, the polarizing plate in the present invention (the polarizing plate obtained by the production method of the present invention) is composed of a polarizer layer and a protective film laminated on at least one surface of the polarizing plate via an adhesive layer (that is, , A polarizing plate with a single-sided protective film or a polarizing plate with a double-sided protective film), which does not have a base film contained in a polarizing laminated film that is a precursor thereof. However, the polarizing plate obtained by the production method of the present invention is a composite polarizing plate in which another optical member (peripheral member) such as another film or layer is laminated thereon, or used as such a composite polarizing plate. Can be. The polarizer layer can be obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin layer (or film).

  Moreover, the light-polarizing laminated film in this invention is provided with a base material film and the polarizer layer laminated | stacked on the at least one surface, and says the thing by which the protective film is not bonded. . In order to distinguish the polarizing laminated film formed by bonding the first protective film to the polarizer layer in the first protective film laminating step S10 from the polarizing laminated film below, “polarizing laminated film with protective film” Also called “film”.

  Hereinafter, each step will be described in detail. In addition, in resin layer formation process S1-1, although a polyvinyl alcohol-type resin layer may be formed in both surfaces of a base film, the case where it forms mainly on one side below is demonstrated.

<1st protective film bonding process S10>
As described above, the polarizing laminated film is preferably produced by a method including [a] resin layer forming step S1-1, [b] stretching step S1-2, and [c] dyeing step S1-3.

[A] Resin layer forming step S1-1
Referring to FIG. 4, this step is a step of obtaining laminated film 100 by forming polyvinyl alcohol-based resin layer 6 on at least one surface of base film 30. The polyvinyl alcohol-based resin layer 6 is a layer that becomes the polarizer layer 5 through the stretching step S1-2 and the dyeing step S1-3. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one or both surfaces of the base film 30 and drying the coating layer.

  The base film 30 can be composed of a thermoplastic resin, and among them, it is preferably composed of a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); polyester resins; (meth) acrylic resins; cellulose triacetate, Cellulose ester resins such as cellulose diacetate; Polycarbonate resins; Polyvinyl alcohol resins; Polyvinyl acetate resins; Polyarylate resins; Polystyrene resins; Polyethersulfone resins; Polysulfone resins; Polyamide resins; System resins; and mixtures and copolymers thereof.

  The base film 30 may have a single-layer structure made of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins. A laminated multilayer structure may be used. The base film 30 may be made of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 when the laminated film 100 is stretched in the stretching step S1-2 described below. preferable.

  The base film 30 can contain an additive. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the base film 30 is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. .

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

  The coating liquid applied to the base film 30 is preferably a polyvinyl alcohol resin solution obtained by dissolving a polyvinyl alcohol resin powder in a good solvent (for example, water). Examples of the polyvinyl alcohol resin include polyvinyl alcohol resins and derivatives thereof. Derivatives of polyvinyl alcohol resins include polyvinyl formal, polyvinyl acetal, etc., as well as polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid. Denatured; modified with alkyl ester of unsaturated carboxylic acid; modified with acrylamide. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10 mol%. When the modification exceeding 30 mol% is performed, it is difficult to adsorb the dichroic dye, which may cause a problem that the polarization performance is lowered. Among the above-mentioned polyvinyl alcohol resins, it is preferable to use a polyvinyl alcohol resin.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10000, more preferably in the range of 1000 to 10000, still more preferably in the range of 1500 to 8000, and in the range of 2000 to 5000. Most preferably. The average degree of polymerization can be determined by a method defined in JIS K 6726-1994 “Testing method for polyvinyl alcohol”. If the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarization performance, and if it exceeds 10,000, the solubility in a solvent is deteriorated, and it becomes difficult to form a polyvinyl alcohol-based resin layer.

  The polyvinyl alcohol resin is preferably a saponified product of a polyvinyl acetate resin. The range of the saponification degree is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 94 mol% or more. If the degree of saponification is too low, the water resistance and heat-and-moisture resistance may not be sufficient when a polarizing laminate film or a polarizing plate is formed. Further, it may be a completely saponified product (having a saponification degree of 100 mol%), but if the saponification degree is too high, the dyeing speed becomes slow, and the production time is required to give sufficient polarization performance. In some cases, a polarizer layer having sufficient polarization performance may not be obtained. Therefore, the saponification degree is preferably 99.5 mol% or less, more preferably 99.0 mol% or less.

The degree of saponification is the unit ratio (mol%) of the ratio of acetate groups (acetoxy groups: -OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, to hydroxyl groups by saponification treatment. The following formula:
Saponification degree (mol%) = [(number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)] × 100
Defined by The saponification degree can be determined according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetate groups that inhibit crystallization.

  Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The coating liquid may contain additives such as a plasticizer and a surfactant as necessary. As the plasticizer, polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol resin.

  The coating liquid is applied to the base film 30 by a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a comma coating method; a lip coating method; a spin coating method; The method can be appropriately selected from a method such as a fountain coating method, a dipping method, and a spray method.

  The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of solvent contained in the coating solution. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher.

  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, two polarizing plates can be obtained from one polarizing laminated film 300, which is advantageous in terms of production efficiency of the polarizing plate.

  The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, and more preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer 6 has a thickness within this range, the dichroic dye has good dyeability and excellent polarization performance through the stretching step S1-2 and the dyeing step S1-3, which will be described later, and is sufficient. A very thin (for example, a thickness of 10 μm or less) polarizer layer 5 can be obtained. If the thickness of the polyvinyl alcohol-based resin layer 6 is less than 3 μm, the film becomes too thin after stretching and the dyeability tends to deteriorate.

  Prior to the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6, at least the surface of the base film 30 on the side where the polyvinyl alcohol resin layer 6 is formed is provided. Corona treatment, plasma treatment, flame (flame) treatment or the like may be performed.

  Prior to coating the coating liquid, the polyvinyl alcohol resin layer 6 is provided on the base film 30 via a primer layer or the like in order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6. May be formed.

  The primer layer can be formed by applying a primer layer forming coating solution to the surface of the substrate film 30 and then drying it. The primer layer forming coating solution contains a component that exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6. The primer layer-forming coating solution usually contains a resin component that imparts such adhesion and a solvent. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability and the like is preferably used, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. Among these, polyvinyl alcohol resins that give good adhesion are preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution containing water as a solvent.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the primer layer forming coating solution. A suitable crosslinking agent is appropriately selected from known ones such as organic and inorganic based on the type of thermoplastic resin to be used. Examples of cross-linking agents include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based cross-linking agents. . When a polyvinyl alcohol resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelate compound crosslinking agent, or the like is preferably used.

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

  The method for applying the primer layer forming coating solution to the base film 30 can be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The primer layer is applied to the surface on which the coating liquid for forming the polyvinyl alcohol-based resin layer is applied. The drying temperature of the coating layer made of the primer layer forming coating solution 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 higher.

[B] Stretching step S1-2
With reference to FIG. 5, this process extends | stretches the laminated | multilayer film 100 which consists of the base film 30 and the polyvinyl alcohol-type resin layer 6, and is extended | stretched consisting of the extended base film 30 'and the polyvinyl alcohol-type resin layer 6'. In this step, the film 200 is obtained. The stretching process is usually uniaxial stretching.

  The stretching ratio of the laminated film 100 can be appropriately selected depending on the desired polarization characteristics, but is preferably more than 5 times and not more than 17 times, more preferably more than 5 times the original length of the laminated film 100. 8 times or less. When the draw ratio is 5 times or less, the polyvinyl alcohol-based resin layer 6 ′ is not sufficiently oriented, and the degree of polarization of the polarizer layer 5 may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the film is likely to be broken during stretching, and the thickness of the stretched film 200 becomes unnecessarily thin, and the workability and handleability in subsequent processes may be reduced.

  The stretching process is not limited to stretching in one stage, and can be performed in multiple stages. In this case, all the multistage stretching processes may be performed continuously before the dyeing process S1-3, and the second and subsequent stretching processes may be performed as a dyeing process and / or a crosslinking process in the dyeing process S1-3. You may do it at the same time. Thus, when performing a extending | stretching process in multistage, it is preferable to perform an extending | stretching process so that it may become a draw ratio more than 5 times combining all the stages of an extending | stretching process.

  The stretching treatment may be longitudinal stretching that extends in the film longitudinal direction (film transport direction), and may be lateral stretching or oblique stretching that extends in the film width direction. Examples of the longitudinal stretching method include inter-roll stretching using a roll, compression stretching, stretching using a chuck (clip), and the like, and examples of the lateral stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted. However, it is preferable to use the dry stretching method because the stretching temperature can be selected from a wide range.

  The stretching temperature is set to be equal to or higher than the temperature at which the polyvinyl alcohol-based resin layer 6 and the entire base film 30 can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base film 30. It is in the range of −30 ° C. to + 30 ° C., more preferably in the range of −30 ° C. to + 5 ° C., and still more preferably in the range of −25 ° C. to + 0 ° C. When the base film 30 consists of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

  If the stretching temperature is lower than the phase transition temperature of −30 ° C., high-strength stretching exceeding 5 times is difficult to achieve, or the fluidity of the base film 30 is too low and the stretching 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 too large and stretching tends to be difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the drawing temperature is within the above range, and more preferably 120 ° C. or higher.

  As a heating method of the laminated film 100 in the stretching process, a zone heating method (for example, a method in which hot air is blown and heated in a stretching zone such as a heating furnace adjusted to a predetermined temperature); There is a method of heating the roll itself; a heater heating method (a method in which infrared heaters, halogen heaters, panel heaters, etc. are installed above and below the laminated film 100 and heated by radiant heat). In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

  Prior to the stretching step S1-2, a preheat treatment step for preheating the laminated film 100 may be provided. As the preheating method, the same method as the heating method in the stretching process can be used. The preheating temperature is preferably in the range of −50 ° C. to ± 0 ° C. of the stretching temperature, and more preferably in the range of −40 ° C. to −10 ° C. of the stretching temperature.

  Moreover, you may provide a heat setting process process after the extending | stretching process in extending process S1-2. The heat setting process is a process in which heat treatment is performed at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the stretched film 200 held by a clip. The crystallization of the polyvinyl alcohol-based resin layer 6 'is promoted by this heat setting treatment. The temperature of the heat setting treatment is preferably in the range of −0 ° C. to −80 ° C. of the stretching temperature, and more preferably in the range of −0 ° C. to −50 ° C. of the stretching temperature.

[C] Dyeing step S1-3
With reference to FIG. 6, this step is a step of forming the polarizer layer 5 by dyeing the polyvinyl alcohol-based resin layer 6 ′ of the stretched film 200 with a dichroic dye and adsorbing and orienting it. Through this step, a polarizing laminated film 300 in which the polarizer layer 5 is laminated on one side or both sides of the base film 30 ′ is obtained. Specifically, iodine or a dichroic organic dye can be used as the dichroic dye.

  The dyeing step can be performed by immersing the entire stretched film 200 in a solution (dyeing solution) containing a dichroic dye. As the staining solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. As a solvent for the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and further preferably 0.025 to 5% by weight. preferable.

  When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine because the dyeing efficiency can be further improved. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The iodide concentration in the dyeing solution is preferably 0.01 to 20% by weight. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80, by weight. Preferably, it is in the range of 1: 7 to 1:70. The temperature of the dyeing solution is preferably in the range of 10-60 ° C, more preferably in the range of 20-40 ° C.

  In addition, although it is possible to perform dyeing process S1-3 before extending process S1-2, or to perform these processes simultaneously, the dichroic dye to be adsorbed to the polyvinyl alcohol-based resin layer is oriented well. It is preferable to carry out the dyeing step S1-3 after subjecting the laminated film 100 to at least some degree of stretching treatment so that the laminated film 100 can be processed. That is, the stretched film 200 obtained by performing the stretching process until the target magnification is reached in the stretching step S1-2 can be used for the dyeing step S1-3, and at a lower magnification than the target in the stretching step S1-2. After performing the stretching process, the stretching process may be performed until the total stretching ratio reaches the target ratio in the dyeing step S1-3. As the latter embodiment, 1) after the stretching process is performed at a lower magnification than the target in the stretching process S1-2, the stretching process is performed so that the total stretching ratio becomes the target ratio during the dyeing process in the dyeing process S1-3. In the case of performing the crosslinking treatment after the dyeing treatment, as described later, 2) after performing the stretching treatment at a lower magnification than the target in the stretching step S1-2, the dyeing treatment in the dyeing step S1-3 In the embodiment, the stretching process is performed until the total stretching ratio does not reach the target ratio, and then the stretching process is performed during the crosslinking process so that the final total stretching ratio becomes the target ratio. it can.

  The dyeing step S1-3 can include a crosslinking treatment step performed subsequent to the dyeing treatment. The crosslinking treatment can be performed by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

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

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

  The crosslinking treatment can be performed simultaneously with the dyeing treatment by blending a crosslinking agent in the dyeing solution. Further, a stretching process may be performed during the crosslinking process. The specific mode for carrying out the stretching treatment during the crosslinking treatment is as described above. Moreover, you may perform the process immersed in a crosslinking solution 2 or more times using 2 or more types of crosslinking solutions from which a composition differs.

  It is preferable to perform a washing | cleaning process and a drying process after dyeing process S1-3 and before bonding a 1st protective film. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The washing step may be a combination of a water washing step and a washing step with an iodide solution.

  As a drying process performed after the washing process, any appropriate method such as natural drying, blow drying, and heat drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

  The thickness of the polarizer layer 5 included in the polarizing laminated film 300 can be, for example, 30 μm or less, and further 20 μm or less, but is preferably 10 μm or less from the viewpoint of thinning the polarizing plate, and is 8 μm or less. Is more preferable. The thickness of the polarizer layer 5 is usually 2 μm or more.

  In this process, with reference to FIG. 7, the 1st protective film 10 is bonded through the adhesive bond layer 15 on the polarizer layer 5 of the said polarizing laminated film 300, and a polarizing laminated film with a protective film Get 400. When the polarizing laminated film 300 has the polarizer layers 5 on both surfaces of the base film 30 ′, usually, protective films are bonded onto the polarizer layers 5 on both surfaces. In this case, these protective films may be the same type of protective film or different types of protective films.

  The material constituting the first protective film 10 is preferably a light-transmitting (preferably optically transparent) thermoplastic resin. Examples of such a resin include a chain polyolefin resin (polypropylene resin). Resins), polyolefin resins such as cyclic polyolefin resins (norbornene resins, etc.); cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyester resins; polycarbonate resins; (meth) acrylic resins; Examples thereof include polystyrene resins; or mixtures and copolymers thereof.

  Since the method of the present invention employs a means for setting the relative humidity of the drying environment within a predetermined range in the drying step S20 described later, curling is suppressed, so that the obtained polarized light can be obtained regardless of the type of the protective film. There is an advantage that curling of the plate can be suppressed. Among them, when a protective film with high moisture permeability such as cellulose ester resin (for example, cellulose triacetate) or (meth) acrylic resin (for example, polymethyl methacrylate resin) is used, the dimensional difference due to the change in moisture content is large. The force for correcting in the positive curl direction is large, and the merit of the present invention is great.

  The first protective film 10 can also be a protective film having an optical function such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching a film made of the thermoplastic resin (uniaxial stretching or biaxial stretching) or by forming a liquid crystal layer or the like on the film. It can be.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

  The polyester-based resin is a resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic 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 naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, and polycyclohexanedimethyl naphthalate.

  The polycarbonate resin is composed of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymer polycarbonate, or the like.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50-100). % Methyl methacrylate resin is used.

  In addition, the description about each thermoplastic resin shown above is applicable also to the thermoplastic resin which comprises the base film 30. FIG.

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

  Although it is preferable that the thickness of the 1st protective film 10 is thin from a viewpoint of thickness reduction of a polarizing plate, when too thin, intensity | strength will fall and it will be inferior to 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.

  As the adhesive used for pasting, an adhesive that requires a drying step (removal of the solvent) is used. For example, a water-based adhesive or a photocurable adhesive containing a solvent (such as an organic solvent) can be used. A water-based adhesive is preferable. Examples of the water-based adhesive include an adhesive made of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. In particular, when a cellulose ester resin film that has been surface-treated (hydrophilized) by saponification treatment or the like is used as the first protective film 10, it is preferable to use a water-based adhesive comprising a polyvinyl alcohol-based resin aqueous solution.

  Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying the polymer or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can contain additives such as polyvalent aldehydes, water-soluble epoxy compounds, melamine compounds, zirconia compounds, and zinc compounds.

  A water-based adhesive is applied to the bonding surface of the polarizer 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 a bonding roll. A pasting process is carried out by applying pressure and making close contact with each other. The coating method of the water-based adhesive (same for the photo-curable adhesive) is not particularly limited, and casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, dip coating method A conventionally known method such as a spraying method can be used.

  In bonding the first protective film 10 on the polarizer layer 5, the bonding surface of the first protective film 10 is subjected to plasma treatment, corona treatment, ultraviolet ray in order to improve the adhesion with the polarizer layer 5. Surface treatment (easy adhesion treatment) such as irradiation treatment, flame (flame) treatment, and saponification treatment can be performed, and among them, plasma treatment, corona treatment or saponification treatment is preferable. For example, when the first protective film 10 is made of a cyclic polyolefin resin, plasma treatment or corona treatment is usually performed. Moreover, when it consists of a cellulose ester-type resin, a saponification process is normally performed. Examples of the saponification treatment include a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

  A photocurable adhesive refers to an adhesive that cures by irradiating an active energy ray such as ultraviolet rays. For example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, a binder. Examples include those containing a resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomer. As a photoinitiator, what contains the substance which generate | occur | produces active species, such as a neutral radical, an anion radical, and a cation radical by irradiation of active energy rays like an ultraviolet-ray can be mentioned. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

<Drying step S20>
In this step, the adhesive layer 15 of the polarizing laminated film 400 with a protective film is dried, and the solvent in the adhesive layer 15 (water for a water-based adhesive, for example, an organic solvent for a photo-curable adhesive). Remove. At this time, in the present invention, the heat treatment for drying is performed in an environment having a relative humidity of 25% or more. A polarizing plate manufactured through a peeling step S30 for peeling and removing the base film 30 ′ by carrying out a drying treatment in such an environment (as described above, the polarizing plate here is a polarizer layer and , And a protective film laminated on at least one surface via an adhesive layer.) Can be effectively suppressed. When the drying treatment is carried out in an environment where the relative humidity is less than 25%, the curl suppressing effect is not recognized.

  Here, the curling of the polarizing plate and the curl suppressing effect of the present invention will be described. Curling is a phenomenon in which a film such as a polarizing plate (including a laminated film) bends in an arcuate shape (or in a cylindrical shape if remarkable). Regarding the polarizing plate with a single-side protective film, which is formed by laminating the first protective film 10 on one surface of the polarizer layer 5 via the adhesive layer 15, curl with the first protective film 10 side inward. The state of being curled is called a normal curl, and the state of curling with the polarizer layer 5 side inside is called a reverse curl.

  Curling becomes a problem in a polarizing plate when the polarizing plate is curled when it is bonded to a display cell such as a liquid crystal cell via an adhesive layer. That is, at the time of bonding to a display cell such as a liquid crystal cell, the polarizing plate is usually a composite polarizing plate because other peripheral members such as various films and layers are bonded. In this case, it is important to suppress curling. As a peripheral member, a protective film for preventing scratches bonded on a protective film; on a protective film (for example, a polarizing plate with a double-sided protective film) or on a polarizer layer (for example, a polarizing plate with a single-sided protective film) Adhesive layer for laminating a polarizing plate to a display cell or other optical member; a separate film laminated on the outer surface of the adhesive layer; on a protective film (for example, with a double-sided protective film) In the case of a polarizing plate) or on a polarizer layer (for example, in the case of a polarizing plate with a single-sided protective film), an optical compensation film such as a retardation film, or other optical functional film; laminated on a protective film Surface treatment layer and the like.

  The composite polarizing plate should be flat with no curling, or slightly curled with the pressure-sensitive adhesive layer side of the composite polarizing plate being outside (convex). Thereby, when bonding a composite polarizing plate to a display cell, it can suppress that a bubble mixes between an adhesive layer and a display cell, and produces a malfunction on display in a display device, or a bonding surface. It can suppress that the malfunction which a defect generate | occur | produces in an edge part arises. On the other hand, when the composite polarizing plate is curled with the pressure-sensitive adhesive layer side inward (concave), it is easy to bite air bubbles at the time of bonding, and there is a high possibility of causing the above-mentioned problems.

  It is possible to intentionally suppress the curl amount of the composite polarizing plate or correct the curl direction to some extent when pasting the peripheral members, but again, it should be applied to at least one surface of the polarizer layer. It is difficult to control the curling of the composite polarizing plate unless the curling is small in the state of the polarizing plate formed by bonding the protective film. Therefore, it is important to suppress curling of the polarizing plate itself obtained by bonding a protective film to at least one surface of the polarizer layer.

  That is, the curl of the polarizing plate formed by laminating a protective film on at least one surface of the polarizer layer is corrected to the extent that it can be corrected by laminating peripheral members regardless of whether the curl is a normal curl or a reverse curl. It is preferable to make it small, and it is more preferable that it be as flat as possible. This can be realized according to the present invention. In particular, in the conventional coating method, when the base film is peeled and removed after the protective film is bonded to the polarizer layer, the obtained polarizing plate tended to curl greatly in the reverse curl direction. In particular, this reverse curl can be effectively suppressed.

  The reason why reverse curl is likely to occur in the conventional coating method is considered to be due to the restraining force exerted by the base film. In the polarizing laminated film formed by the coating method, the polarizer layer is not shrunk by the rigidity of the base film, and when the base film is peeled and removed after the protective film is bonded, the polarizer layer is shrunk. This is considered to be caused. In contrast, in the case of a single film method in which a protective film is bonded to a polarizer (polarizing film) made of a single film (single film) via an adhesive layer, moisture is evaporated and dried before the protective film is bonded. Further, since the polarizer is sufficiently contracted by tension control or the like, the dimensional change does not occur so much even after the protective film is bonded, and the problem of curling is hardly caused in the first place.

  The reason why the reverse curl can be effectively suppressed by the method of the present invention in which the base film 30 ′ is peeled and removed after the heat treatment for drying is performed in an environment having a relative humidity of 25% or more is as follows. It is estimated to be. That is, a certain amount of time is required for the adhesive layer 15 to be sufficiently solidified or cured by the heat treatment in the drying process, and the moisture content of the first protective film 10 is greatly reduced until the adhesive layer 15 is sufficiently solidified or cured. As a result, the film contracts, and the first protective film 10 is bonded and fixed to the polarizer layer 5 in a sufficiently contracted state. In this case, the force which the 1st protective film 10 tends to shrink does not arise in the polarizing plate obtained. On the other hand, in the present invention, since the drying treatment can be performed while suppressing moisture evaporation from the first protective film 10, the force that the first protective film 10 tends to contract in the obtained polarizing plate, that is, the positive curl Power to correct in the direction works. This force suppresses reverse curl.

  The heat treatment for drying is preferably performed in an environment with a relative humidity of 50% or less, and more preferably in an environment with a relative humidity of 40% or less. When the relative humidity exceeds 50%, particularly when an aqueous adhesive is used, the drying of the adhesive layer 15 may be poor (not achieved). Although it is possible to carry out the drying treatment at a relative humidity of 40% or more, further 50% or more, in that case, in order to prevent drying failure, the drying temperature is increased within a preferable range described later. It is preferable to set.

  The drying temperature is preferably 30 to 80 ° C. When the drying temperature is less than 30 ° C., the adhesive layer 15 is not sufficiently dried, and the first protective film 10 is easily peeled off from the polarizer layer 5. Further, when the drying temperature exceeds 80 ° C. under a relative humidity of 25% or more, the amount of water present in the air becomes excessive, so that the polarizing laminated film 400 with a protective film used for the drying process is used in this drying environment. The film may condense at the moment it is placed, or condensation may occur in a local low-temperature portion near the entrance / exit of the drying apparatus (drying furnace), which may adversely affect the drying of the adhesive layer 15.

  Drying of the adhesive layer 15 can be performed by introducing the polarizing laminated film 400 with a protective film into a drying furnace capable of adjusting temperature and humidity. You may make it adjust the inside of a drying furnace with the humidity controller which attached the relative humidity separately.

  After the drying step, a curing step of curing at room temperature or slightly higher temperature, for example, a temperature of about 20 to 45 ° C. may be provided. The curing temperature is generally set lower than the drying temperature.

  When a photocurable adhesive is used as the adhesive, after performing the drying process, a curing process is performed in which the photocurable adhesive is cured by irradiating active energy rays. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp A microwave excited mercury lamp, a metal halide lamp, or the like is preferably used.

<Peeling step S30>
Referring to FIG. 8, this step is a step of peeling and removing the base film 30 ′ after the drying step S20. In this step, the polarizing plate 1 with a single-side protective film is obtained. When the polarizing laminated film 300 has the polarizer layers 5 on both surfaces of the base film 30 ′, and a protective film is bonded to both the polarizer layers 5, a single polarized light is obtained by the peeling step S 30. The polarizing plate 1 with a single-sided protective film is obtained from the conductive laminated film 300.

  The method for peeling and removing the base film 30 ′ is not particularly limited, and can be peeled by the same method as the separator (peeling film) peeling step performed with a normal pressure-sensitive adhesive polarizing plate. The substrate film 30 ′ may be peeled off immediately after the drying step S <b> 20, or may be peeled off while being wound up in a subsequent step after the drying step S <b> 20.

<2nd protective film bonding process S40>
With reference to FIG.3 and FIG.9, if this process of bonding the 2nd protective film 20 to the surface by the side of the polarizer layer 5 in the polarizing plate 1 with a single-sided protective film through the adhesive layer 25 is implemented, it will be double-sided. The polarizing plate 2 with a protective film can be obtained. About the 2nd protective film 20 and the adhesive bond layer 25 which bonds this, the description which described the 1st protective film 10 and the adhesive bond layer is quoted. The first protective film 10 and the second protective film 20 may be the same type of protective film or different types of protective films. The adhesive layer 15 and the adhesive layer 25 may be formed of the same type of adhesive, or may be formed of different types of adhesive.

  Similar to the drying of the adhesive layer 15, the curling in the polarizing plate 2 with the double-sided protective film can be further improved by performing a drying heat treatment in an environment where the relative humidity is 25% or more in the drying process of the adhesive layer 25. There is.

  As described above, the obtained polarizing plate 1 with a single-sided protective film and the polarizing plate 2 with a double-sided protective film are obtained by pasting peripheral members as exemplified above into a composite polarizing plate, or such a composite polarizing plate. Or can be used as

  The pressure-sensitive adhesive layer as an example of the peripheral member can be laminated on the outer surface of any protective film in the polarizing plate 2 with a double-sided protective film. It can laminate | stack on the surface on the opposite side to the protective film of a child layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is usually based on a (meth) acrylic resin, styrene resin, silicone resin or the like, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It consists of an adhesive composition. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property. The thickness of an adhesive layer is 1-40 micrometers normally, Preferably it is 3-25 micrometers.

  In addition, as an optical functional film as another example of the peripheral member, a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light that shows the opposite property; anti-glare having an uneven shape on the surface A film with a function; a film with a surface antireflection function; a reflection film having a reflection function on the surface; a transflective film having both a reflection function and a transmission function; and a viewing angle compensation film.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

<Example 1>
(1) Primer layer forming step Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) is dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with a crosslinking agent (“Smiles Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 5 parts by weight to 6 parts by weight of the polyvinyl alcohol powder to form a primer layer forming coating solution. Got.

  Next, an unstretched polypropylene (PP) film (melting point: 163 ° C.) having a thickness of 110 μm is prepared as a base film, and after corona treatment is performed on one surface thereof, the above-described microgravure coater is used on the corona treatment surface. The primer layer-forming coating solution was applied and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(2) Production of laminated film (resin layer forming step)
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C., and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. This was used as a coating liquid for forming a polyvinyl alcohol resin layer.

  By applying the polyvinyl alcohol-based resin layer forming coating solution to the primer layer surface of the base film having the primer layer prepared in (1) above using a lip coater, and then drying at 80 ° C. for 20 minutes. A polyvinyl alcohol-based resin layer was formed on the primer layer to obtain a laminated film composed of base film / primer layer / polyvinyl alcohol-based resin layer.

(3) Production of stretched film (stretching process)
The laminated film produced in the above (2) was subjected to 5.8-fold free end uniaxial stretching at 160 ° C. using a tenter device to obtain a stretched film. The thickness of the stretched polyvinyl alcohol resin layer was 3.0 μm.

(4) Production of polarizing laminated film (dyeing process)
The stretched film produced in the above (3) is immersed in a 26 ° C. dyeing aqueous solution containing iodine and potassium iodide (0.35 parts by weight iodine and 10 parts by weight potassium iodide per 100 parts by weight of water). After performing the dyeing treatment, it is added to a 78 ° C. aqueous crosslinking solution containing boric acid and potassium iodide (9.5 parts by weight of boric acid and 5 parts by weight of potassium iodide per 100 parts by weight of water) for 300 seconds. Immersion was performed for crosslinking. Thereafter, the film was washed with pure water at 8 ° C. for 10 seconds and finally dried at 40 to 50 ° C. for 200 seconds to obtain a polarizing laminated film composed of a base film / primer layer / polarizer layer.

(5) Preparation of polarizing plate (protective film bonding step, drying step and peeling step)
Polyvinyl alcohol powder (“KL-318” manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with a crosslinking agent (“Smile Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to obtain an aqueous adhesive solution.

  Next, after coating the adhesive aqueous solution on the outer surface (bonding surface) of the polarizer layer of the polarizing laminate film prepared in (4) above, a protective film [transparent protective film made of triacetyl cellulose (TAC)] ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.) and a thickness of 40 µm] were bonded, and crimped by passing between a pair of bonding rolls. Next, it is introduced into a drying furnace adjusted to 60 ° C. and 35% RH, and the adhesive layer is dried by performing a heat treatment for 10 minutes. From the base film / primer layer / polarizer layer / adhesive layer / protective film A polarizing laminated film with a protective film was obtained.

  Finally, the base film was peeled off from the polarizing laminated film with a protective film. The base film was easily peeled off to obtain a polarizing plate with a single-side protective film.

<Example 2, Comparative Examples 1-2>
A polarizing plate with a single-sided protective film was produced in the same manner as in Example 1 except that the drying conditions of the adhesive layer were as shown in Table 1.

[Measurement and Evaluation of Curling Amount of Polarizing Plate]
A test piece having an absorption axis direction (MD) of 80 mm × transmission axis direction (TD) of 80 mm was cut out from the obtained polarizing plate with a single-side protective film and allowed to stand for 24 hours in an environment of 25 ° C. and 55% RH. This test piece has a reverse curl that is curled with the polarizer layer side inward, and if the concave surface is placed on the reference surface (horizontal base), the two opposite edges rise. The test piece is cylindrical (the two raised edges are not in contact with each other). In this state, the diameters at both ends of the cylindrical shape formed by the test piece were measured, the curl amount was obtained as an average of them, and the degree of curl suppression was evaluated according to the following evaluation criteria. The results are shown in Table 1. The smaller the curl amount, the stronger the reverse curl, and the larger the curl amount, the weaker the reverse curl.

A: The curl amount is 17 mm or more, and the curling of the polarizing plate is sufficiently suppressed.
B: The curl amount is less than 17 mm, and the curling of the polarizing plate is remarkable.

  The above evaluation criteria are as follows. When the curl amount is 17 mm or more, a protective film for preventing scratches (polyethylene terephthalate film with an adhesive layer) is bonded to the outer surface of the protective film of the polarizing plate with a single-sided protective film to obtain a substantially flat composite polarizing plate. I was able to. Furthermore, even if the adhesive layer for bonding to a liquid crystal cell was bonded to the outer surface of the polarizer layer of the composite polarizing plate, the composite polarizing plate was kept almost flat.

  On the other hand, when the curl amount was less than 17 mm, the obtained composite polarizing plate was curled in the reverse curl direction even when the protective film was bonded to the outer surface of the protective film. Furthermore, even if the adhesive layer for bonding to a liquid crystal cell was bonded to the outer surface of the polarizer layer of the composite polarizing plate, the reverse curled state was maintained. Moreover, when it was left to stand in an environment of 23 ° C. and 55% RH for several days and observed again, there was a problem that reverse curl was further increased.

  DESCRIPTION OF SYMBOLS 1 Polarizing plate with single-sided protective film, 2 Polarizing plate with double-sided protective film, 5 Polarizer layer, 6 Polyvinyl alcohol-based resin layer, 6 ′ Stretched polyvinyl alcohol-based resin layer, 10 First protective film, 15, 25 Adhesive Layer, 20 second protective film, 30 base film, 30 ′ stretched base film, 100 laminated film, 200 stretched film, 300 polarizing laminated film, 400 polarizing laminated film with protective film.

Claims (3)

A step of bonding a protective film via an adhesive layer on a polarizer layer of a polarizing laminate film including a polarizer layer on at least one surface of a base film;
A step of performing a heat treatment in an environment of a relative humidity of 25% or more and a temperature of 30 to 80 ° C. to dry the adhesive layer;
Peeling and removing the base film;
Look at including in this order,
The adhesive forming the adhesive layer is a water-based adhesive,
The polarizing laminated film is
After applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film, a step of forming a polyvinyl alcohol-based resin layer by drying to obtain a laminated film;
Stretching the laminated film to obtain a stretched film;
A step of obtaining a polarizing laminated film by dyeing a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form the polarizer layer;
The manufacturing method of a polarizing plate manufactured by the method containing this . The manufacturing method according to claim 1, wherein the protective film is made of a cellulose ester resin or a (meth) acrylic resin. The manufacturing method of Claim 1 or 2 whose thickness of the said polarizer layer is 10 micrometers or less.

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