JPWO2016002504A1 - Manufacturing method of polarizing plate with double-sided protective film - Google Patents

Abstract

Including a step of peeling and removing the base film from the multilayer film including the base film, the iodine-based polarizer and the first protective film in this order, and a step of bonding the second protective film to the outer surface of the iodine-based polarizer, Double-sided protection in which the first and second protective films are thermoplastic resin films having a moisture permeability of 150 g / m 2/24 hr or less, and the moisture content of the iodine-based polarizer when the second protective film is bonded is less than 8% by weight. Provided is a method for producing a polarizing plate with a film, and a polarizing plate with a double-sided protective film in which a thermoplastic resin film having a moisture permeability of 150 g / m 2/24 hr or less is laminated on both sides of an iodine polarizer having a moisture content of less than 8% by weight. The

Description

  The present invention relates to a method for producing a polarizing plate with a double-sided protective film in which protective films are bonded to both surfaces of an iodine-based polarizer, and more specifically, a protective film having a low moisture permeability is sequentially bonded to both surfaces of an iodine-based polarizer. The present invention relates to a method for producing a polarizing plate with a double-sided protective film.

  The polarizing plate is widely used in display devices such as a liquid crystal display device, especially in various mobile devices such as smartphones 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 polarizer itself has a low resistance to moisture and heat, and its polarization characteristics are likely to deteriorate in a humid and heat environment. Conventionally, a triacetyl cellulose film has been used as a protective film for protecting a polarizer, but since a triacetyl cellulose film has high moisture permeability, a polarizing plate using this film as a protective film is particularly iodine-based as a polarizer. In the case of using a polarizer, there has been a problem that the heat and humidity resistance is still insufficient.

  Therefore, in order to improve the moisture and heat resistance of the polarizing plate, it has been proposed to bond a protective film having a low moisture permeability such as a norbornene resin film to the iodine polarizer instead of the triacetyl cellulose film. [For example, paragraph [0005] of JP-A-2004-245925 (Patent Document 1)].

JP 2004-245925 A

  If a protective film with low moisture permeability is bonded to both surfaces of the iodine-based polarizer, moisture penetration from the outside is reduced, so that the wet heat resistance of the polarizing plate can be improved. However, on the other hand, a conventional polarizing plate with a double-sided protective film using a protective film with low moisture permeability on both sides is cross-linked when subjected to a heat resistance test that is exposed to a higher temperature environment than a general wet heat resistance test. It is the inventor of the present invention that light leakage occurs under Nicol (a phenomenon in which red color light leaks from the polarizing plate and the polarizing plate appears red, also referred to as red discoloration), or polarization characteristics deteriorate. It became clear by examination. This problem of poor heat resistance becomes more conspicuous as the thickness of the iodine polarizer is smaller.

  Therefore, the present invention is a polarizing plate in which a protective film having low moisture permeability is bonded to both surfaces of an iodine-based polarizer, and a method for producing a polarizing plate with a double-sided protective film that combines heat and moisture resistance, And it aims at provision of the polarizing plate with a double-sided protective film which combines heat-and-moisture resistance and heat resistance.

  This invention provides the manufacturing method of the polarizing plate with a double-sided protective film shown below, and the polarizing plate with a double-sided protective film.

[1] A step of peeling and removing the base film from the multilayer film including the base film, the iodine-based polarizer and the first protective film in this order to obtain a polarizing plate with a single-side protective film;
Bonding a second protective film to the outer surface of the iodine-based polarizer in the polarizing plate with a single-sided protective film to obtain a polarizing plate with a double-sided protective film;
Including
The first protective film and the second protective film is a thermoplastic film of less moisture permeability 150 g / m ^2/24 hr or,
The manufacturing method of the polarizing plate with a double-sided protective film whose moisture content of the said iodine type polarizer when bonding a said 2nd protective film is less than 8 weight%.

  [2] The production method according to [1], wherein the second protective film is bonded to an outer surface of the iodine polarizer using an active energy ray-curable adhesive.

  [3] The manufacturing method according to [1] or [2], wherein the iodine-based polarizer has a thickness of 10 μm or less.

[4] A polarizing plate with a double-sided protective film is obtained by laminating a second protective film on the outer surface of the iodine-type polarizer in the polarizing plate with a single-sided protective film including the iodine-type polarizer and the first protective film laminated on one side thereof. Including a step of obtaining
The first protective film and the second protective film is a thermoplastic film of less moisture permeability 150 g / m ^2/24 hr or,
The manufacturing method of the polarizing plate with a double-sided protective film whose moisture content of the said iodine type polarizer when bonding a said 2nd protective film is less than 8 weight%.

  [5] The production method according to [4], wherein the second protective film is bonded to an outer surface of the iodine polarizer using an active energy ray-curable adhesive.

  [6] The manufacturing method according to [4] or [5], wherein the iodine polarizer has a thickness of 10 μm or less.

[7] An iodine-based polarizer and a protective film laminated on both sides thereof,
Any protective film to be laminated on both sides, a thermoplastic resin film of less moisture permeability 150g / m ² / 24hr,
A polarizing plate with a double-sided protective film, wherein the iodine polarizer has a moisture content of less than 8% by weight.

  [8] The polarizing plate with a double-sided protective film according to [7], wherein the iodine polarizer has a thickness of 10 μm or less.

  According to the present invention, a method for producing a polarizing plate with a double-sided protective film, which is a polarizing plate in which a protective film having low moisture permeability is bonded to both sides of an iodine-based polarizer, which has both moisture heat resistance and heat resistance. And the polarizing plate which bonded the protective film with low moisture permeability on both surfaces of an iodine type polarizer, Comprising: The polarizing plate with a double-sided protective film which has both heat-and-moisture resistance and heat resistance can be provided.

It is a flowchart which shows a preferable example of the manufacturing method of the polarizing plate with a double-sided protective film which concerns on this invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the polarizing plate with a single-sided protective film. It is a flowchart which shows a preferable example of a polarizing plate preparation process with a single-sided protective film. 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 multilayer film obtained at a bonding process. It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate with a double-sided protective film which concerns on this invention.

<Method for producing polarizing plate with double-sided protective film>
The manufacturing method of the polarizing plate with a double-sided protective film according to the present invention may include the following steps as shown in FIG.

(1) Step S10 of preparing a polarizing plate with a single-sided protective film including an iodine-based polarizer and a first protective film laminated on one side thereof (hereinafter also referred to as “polarizing plate with a single-sided protective film S10”), and (2) Step S20 for obtaining a polarizing plate with a double-sided protective film by bonding the second protective film to the outer surface of the iodine-based polarizer in the polarizing plate with a single-sided protective film (hereinafter referred to as “Polarizer production step S20 with double-sided protective film”) Also called).

As described above, in the present invention, the first protective film and the second protective film are sequentially bonded to the iodine polarizer. In that case, in order to improve the heat-and-moisture resistance of the polarizing plate with a double-sided protective film obtained, the 1st protective film bonded to one side of an iodine type polarizer, and the 2nd protective film bonded to the other side as a moisture permeability using a thermoplastic resin film of low moisture permeability is not more than 150g / m ² / 24hr.

Moreover, in order to improve the heat resistance of the polarizing plate with a double-sided protective film obtained, the water content of the iodine-based polarizer when the second protective film is bonded to the iodine-based polarizer is less than 8% by weight. In the present invention, in order to improve the heat and moisture resistance, a protective film with low moisture permeability is bonded to both surfaces of the iodine-based polarizer to form a polarizing plate.
a) When a protective film with low moisture permeability is applied to both sides, moisture in the iodine-based polarizer is difficult to dissipate to the outside, and moisture accumulates in the iodine-based polarizer,
b) Iodine-based polarized light when the second protective film is bonded as described above from the situation such as redness in the heat resistance test and deterioration of polarization characteristics caused by moisture remaining in the iodine-based polarizer. It is effective to control the moisture content of the child. The moisture content of the iodine-based polarizer is measured according to the method described in the Examples section.

  The moisture content of the iodine-based polarizer is during the process of manufacturing the polarizing plate with a double-sided protective film, and is in any stage before the second protective film is bonded to the iodine-based polarizer. This can be achieved by providing a step S30 (hereinafter also referred to as “moisture percentage reduction step S30”) for performing a moisture percentage reduction process on the film including the polarizer (see FIG. 1).

Hereinafter, each process will be described with reference to FIGS.
(1) Polarizing plate preparation process S10 with a single-sided protective film
This step is a step of preparing (preparing) a polarizing plate 100 with a single-sided protective film as shown in FIG. 2, for example, including the iodine-based polarizer 5 and the first protective film 10 laminated on one side thereof. As shown in FIG. 2, the first protective film 10 is usually bonded (adhered and fixed) to one surface of the iodine-based polarizer 5 via the first adhesive layer 15.

[Iodine polarizer]
The iodine-based polarizer 5 is a polarizer in which iodine is adsorbed and oriented as a dichroic dye. Specifically, the iodine-based polarizer 5 is obtained by adsorbing and orienting iodine to a uniaxially stretched polyvinyl alcohol resin layer (or film). Can be. The thickness of the iodine-based polarizer 5 can be, for example, 30 μm or less, and further 20 μm or less, but in particular for mobile devices, it is preferably 10 μm or less from the viewpoint of thinning the polarizing plate with a double-sided protective film, More preferably, it is 8 μm or less. The thickness of the iodine-based polarizer 5 is usually 2 μm or more.

  When the thickness of the iodine-based polarizer 5 is reduced, the concentration of iodine is increased, and the concentration of iodine complex existing in the vicinity of the interface with the protective film laminated on both sides is also increased. It is easy to receive. Therefore, the heat-and-moisture resistance tends to be lower as the thickness of the iodine-based polarizer 5 is smaller. Moreover, when the thickness of the iodine-type polarizer 5 is reduced and the concentration of iodine is further increased, the iodine-type polarizer 5 is easily affected by moisture remaining in the iodine-type polarizer and heat resistance is likely to be lowered. As described above, the heat-and-moisture resistance and heat resistance are likely to be lower as the thickness of the iodine-based polarizer 5 is smaller. However, the present invention is particularly advantageous when the thickness of the iodine-based polarizer 5 is small.

  As the polyvinyl alcohol resin constituting the polyvinyl alcohol resin layer, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

  In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl. The same applies to cases such as “(meth) acryloyl”.

  What formed the said polyvinyl alcohol-type resin into a film comprises the iodine-type polarizer 5. FIG. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method, but it is easy to obtain the iodine-based polarizer 5 having a small thickness, and the iodine-based polarization of the thin film in the process. Since the handleability of the child 5 is also excellent, a method of forming a film by coating a solution of a polyvinyl alcohol resin as described later on the base film is preferable.

  The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, more preferably 94.0. It is in the range of ˜99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and heat-and-moisture resistance of the resulting polarizing plate with a double-sided protective film are lowered. When a polyvinyl alcohol-based resin having a saponification degree exceeding 99.5 mol% is used, the iodine dyeing speed becomes slow, the productivity decreases, and the iodine-based polarizer 5 having sufficient polarization performance cannot be obtained. There is.

The degree of saponification is the unit ratio (mol%) of the proportion of acetate groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, changed to hydroxyl groups by the saponification step. The following formula:
Saponification degree (mol%) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)
Defined by The degree of saponification 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.

  The polyvinyl alcohol-based resin may be a modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; alkyl esters of unsaturated carboxylic acids, (meth) acrylamide, and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When modification exceeding 30 mol% is performed, it is difficult to adsorb iodine, and it is difficult to obtain an iodine-based polarizer 5 having sufficient polarization performance.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined according to JIS K 6726-1994.

[First protective film]
The first protective film 10 has a light-transmitting property (preferably optically clear) a thermoplastic resin, and the moisture permeability is less film 150g / m ² / 24hr. The moisture permeability includes a moisture permeability of the second protective film described later, a temperature measured according to JIS Z 0208-1976 “moisture-proof packaging material moisture permeability test method (cup method)”, and a relative humidity of 90 ° C. Percent moisture permeability. Moisture permeability is preferably 100g / m ² / 24hr or less.

As a means for the moisture permeability of the first protective film 10 below 150g / m ² / 24hr, or used as moisture permeability is lower in the thermoplastic resin constituting the film, or by increasing the thickness of the film, onto the film For example, a barrier layer having low moisture permeability may be provided.

  The thermoplastic resin constituting the first protective film 10 is not particularly limited as long as the above moisture permeability can be achieved. However, since the moisture permeability is low and the thickness of the first protective film 10 can be reduced, a chain polyolefin resin (polypropylene type) is used. Resins), polyolefin resins such as cyclic polyolefin resins (norbornene resins, etc.); polyester resins such as polyethylene terephthalate resins; polycarbonate resins; (meth) acrylic resins; polystyrene resins; A mixture, copolymer or the like is preferably used.

  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 cyclic olefins as polymerization units. 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 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 dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. A diol can be used as the polyhydric alcohol, 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.

  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 provided on the surface of the first protective film 10 opposite to the iodine-based polarizer 5. It can also be formed. The method for forming the surface treatment layer is not particularly limited, and a known method can be used.

  The first protective film 10 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. it can.

  The thickness of the first protective film 10 is preferably 90 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less, from the viewpoint of thinning the polarizing plate with a double-sided protective film. The thickness of the 1st protective film 10 is 5 micrometers or more normally from a viewpoint of intensity | strength and a handleability.

[First adhesive layer]
The first adhesive layer 15 is a layer for bonding and fixing the first protective film 10 to one surface of the iodine-based polarizer 5. The adhesive that forms the first adhesive layer 15 is an active energy ray-curable adhesive (preferably containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays). Can be a water-based adhesive in which an adhesive component such as an ultraviolet curable adhesive) or a polyvinyl alcohol-based resin is dissolved or dispersed in water.

  The curable compound may be a cationic polymerizable curable compound or a radical polymerizable curable compound. Examples of the cationic polymerizable curable compound include an epoxy compound (a compound having one or more epoxy groups in the molecule) and an oxetane compound (one or two or more oxetane rings in the molecule). Or a combination thereof. Examples of the radical polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule) and radical polymerizable double bonds. Other vinyl compounds or combinations thereof can be mentioned. A cationic polymerizable curable compound and a radical polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further includes a cationic polymerization initiator and / or a radical polymerization initiator for initiating a curing reaction of the curable compound.

  The single-sided protective film-attached polarizing plate 100 may be prepared in advance or may be manufactured by an arbitrary method. The following can be mentioned as a manufacturing method.

i) A method of bonding the first protective film 10 to one surface of an iodine-based polarizer 5 made of a single (single) film manufactured by a known method, and
ii) A manufacturing method including the following steps as shown in FIG.

A resin layer forming step S10-1 for forming a polyvinyl alcohol resin layer by applying a coating liquid containing a polyvinyl alcohol resin on at least one surface of the base film, and then drying to form a laminated film;
Stretching step S10-2 for stretching a laminated film to obtain a stretched film,
Dyeing process S10-3 which dyes the polyvinyl alcohol-type resin layer of a stretched film with iodine, forms an iodine-type polarizer, and obtains a polarizing laminated film,
Bonding step S10-4 to obtain a multilayer film by laminating the first protective film 10 on the iodine-type polarizer of the polarizing laminated film, and a polarizing plate with a single-side protective film by peeling and removing the base film from the multilayer film Peeling step S10-5 to obtain 100.

[Resin layer forming step S10-1]
Referring to FIG. 4, this step is a step of obtaining laminated film 200 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 iodine-based polarizer 5 through the stretching step S10-2 and the dyeing step S10-3. 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 it. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that a thin film iodine-based polarizer 5 can be easily obtained.

  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 is preferably composed of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin layer 6 in the stretching step S10-2 described below.

  The base film 30 can contain an additive. Specific 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 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 viewpoints of 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). The details of the polyvinyl alcohol resin are as described above. The coating liquid may contain additives such as a plasticizer and a surfactant as necessary.

  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, curling of the film that may occur during the production of the polarizing laminated film 400 (see FIG. 6) can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 400. It is also advantageous in terms of efficiency.

  The thickness of the polyvinyl alcohol-based resin layer 6 in the laminated film 200 is preferably 3 to 30 μm, more preferably 5 to 20 μm. If it is the polyvinyl alcohol-type resin layer 6 which has the thickness in this range, the dyeing | staining property of iodine will be favorable through the extending | stretching process S10-2 and dyeing | staining process S10-3 mentioned later, and it will be excellent in polarization performance, and thin enough ( For example, an iodine-based polarizer 5 having a thickness of 10 μm or less can be obtained.

  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. For the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 30 via a primer layer or the like.

  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. This coating solution includes a component that exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually includes a resin component that provides 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. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking 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 with a double-sided protective film.

  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 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.

[Extension process S10-2]
With reference to FIG. 5, this process is a process of extending the laminated film 200 to obtain a stretched film 300 composed of the stretched base film 30 ′ and the polyvinyl alcohol-based resin layer 6 ′. The stretching process is usually uniaxial stretching.

  The draw ratio of the laminated film 200 can be appropriately selected according to 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 200. 8 times or less. When the draw ratio is 5 times or less, the polyvinyl alcohol resin layer 6 ′ is not sufficiently oriented, and the degree of polarization of the iodine polarizer 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 300 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 of the multistage stretching processes may be performed continuously before the dyeing process S10-3, and the second and subsequent stretching processes may be performed as a dyeing process and / or a crosslinking process in the dyeing process S10-3. 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 exceeding 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.

  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 200 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); And a method of heating the roll itself; a heater heating method (a method in which infrared heaters, halogen heaters, panel heaters and the like are installed above and below the laminated film 200 and heated by radiant heat) and the like. 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 S10-2, a preheat treatment step for preheating the laminated film 200 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 S10-2. 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 300 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.

[Dyeing step S10-3]
With reference to FIG. 6, this step is a step in which the polyvinyl alcohol resin layer 6 ′ of the stretched film 300 is dyed with iodine and adsorbed and oriented to form the iodine polarizer 5. Through this step, a polarizing laminated film 400 in which the iodine-based polarizer 5 is laminated on one surface or both surfaces of the base film 30 ′ is obtained.

  The dyeing step can be performed by immersing the stretched film 300 in a solution containing iodine (dyeing solution). As the staining solution, a solution in which iodine is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent compatible with water may be further added. The iodine concentration in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight.

  Since the dyeing efficiency can be improved, it is preferable to further add an iodide to the dyeing solution. 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 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, by weight, preferably 1: 5 to 1: 100, more preferably 1: 6 to 1:80. The temperature of the dyeing solution is preferably 10 to 60 ° C, more preferably 20 to 40 ° C.

  In addition, although dyeing process S10-3 can be performed before extending process S10-2, or these processes can be performed simultaneously, the iodine adsorb | sucked to a polyvinyl alcohol-type resin layer can be orientated favorably. It is preferable to carry out the dyeing step S10-3 after performing at least some stretching treatment on the laminated film 200 so that it is possible.

  The dyeing step S10-3 can include a crosslinking treatment step performed subsequent to the dyeing treatment. The crosslinking treatment can be performed by immersing a dyed film in a solution (crosslinking solution) in which a crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. Only 1 type may be used for a crosslinking agent and it may use 2 or more types together. As a solvent for the crosslinking solution, water can be used, but it may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably 1 to 20% by weight, more preferably 6 to 15% by weight.

  The crosslinking solution can further comprise iodide. By adding the iodide, the polarization performance in the plane of the iodine-based polarizer 5 can be made more uniform. Specific examples of iodide are the same as described above. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably 10 to 90 ° C.

  In addition, a crosslinking process can also be performed simultaneously with a dyeing | staining process by mix | blending a crosslinking agent in a dyeing solution. 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 S10-3 and before bonding process S10-4 mentioned later. 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 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.

[Bonding step S10-4]
Referring to FIG. 7, in this step, the first adhesive layer 15 is formed on the iodine-based polarizer 5 of the polarizing laminated film 400, that is, on the surface opposite to the base film 30 ′ of the iodine-based polarizer 5. It is the process of obtaining the multilayer film 500 by bonding the 1st protective film 10 through. The adhesive that forms the first adhesive layer 15 is as described above.

  In addition, when the polarizing laminated film 400 has the iodine type polarizer 5 on both surfaces of the base film 30 ′, the first protective film 10 is usually bonded to the both surfaces of the iodine type polarizer 5. In this case, these first protective films 10 may be the same type of protective film or different types of protective films.

  When bonding the 1st protective film 10 using an active energy ray hardening adhesive, the iodine type polarizer 5 is attached to the 1st protective film 10 through the active energy ray hardening adhesive used as the 1st adhesive layer 15. FIG. After the lamination, the adhesive layer is cured by irradiating with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Among them, ultraviolet rays are preferable, and as a light source in this case, 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 excitation mercury lamp, a metal halide lamp, or the like can be used. In the case of using an aqueous adhesive, the first protective film 10 may be laminated on the iodine polarizer 5 through the aqueous adhesive and then dried by heating.

  In bonding the first protective film 10 to the iodine-based polarizer 5, in order to improve the adhesion with the iodine-based polarizer 5 on the bonding surface of the first protective film 10 and / or the iodine-based polarizer 5. In addition, surface treatment (easily adhesion treatment) such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment can be performed. Among them, plasma treatment, corona treatment or saponification treatment is performed. It is preferable.

[Peeling step S10-5]
This step is a step of peeling and removing the base film 30 ′ from the multilayer film 500. Through this step, the same polarizing plate 100 with a single-sided protective film as in FIG. 2 is obtained. When the polarizing laminated film 400 has the iodine-based polarizer 5 on both surfaces of the base film 30 ′, and the first protective film 10 is bonded to both the iodine-based polarizers 5, the peeling step S 50 Two polarizing plates with a single-sided protective film 100 can be obtained from one polarizing laminated film 400.

  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. Substrate film 30 'may peel immediately as it is after bonding process S10-4, and after bonding process S10-4, it winds up in roll shape once, and peels off, unwinding in the subsequent process. May be.

(2) Polarizing plate making process S20 with double-sided protective film
At this process, the polarizing plate with a double-sided protective film is obtained by bonding the 2nd protective film 20 to the outer surface of the iodine type polarizer 5 in the polarizing plate 100 with a single-sided protective film. An example of the layer structure of the polarizing plate with a double-sided protective film is shown in FIG. Like the polarizing plate 600 with a double-sided protective film shown in FIG. 8, the second protective film 20 is usually bonded (adhered and fixed) to the iodine-based polarizer 5 via the second adhesive layer 25. The outer surface of the iodine-based polarizer 5 means a surface of the iodine-based polarizer 5 opposite to the first protective film 10, and a polarizing plate 100 with a single-sided protective film through a step of peeling and removing the base film 30 ′. Means the surface of the iodine-based polarizer 5 exposed by peeling off the base film 30 ′.

Also the second protective film 20, similarly to the first protective film 10, having a light transmitting property (a preferably optically clear) a thermoplastic resin, and moisture permeability by the following film 150 g / m ^2/24 hr or is there. A protective film having both optical functions such as a retardation film and a brightness enhancement film may be used. Regarding the surface treatment layer that the second protective film 20 may have and the thickness, material, and the like of the film, the above description of the first protective film 10 is cited. The first protective film 10 and the second protective film 20 may be protective films made of the same kind of resin or may be protective films made of different kinds of resins.

  The adhesive forming the second adhesive layer 25 can be an active energy ray curable adhesive or an aqueous adhesive, like the first adhesive layer 15, but preferably an ultraviolet curable adhesive or the like. It is an active energy ray-curable adhesive. When the water-based adhesive is used, moisture is supplied to the iodine-based polarizer 5, so that the moisture content of the iodine-based polarizer 5 when the second protective film 20 is bonded may not be less than 8% by weight. is there. The adhesive forming the second adhesive layer 25 may have the same composition as the adhesive forming the first adhesive layer 15, or may have a different composition.

(3) Moisture content reduction step S30
The manufacturing method of the polarizing plate with a double-sided protective film according to the present invention is as described above so that the moisture content of the iodine-based polarizer 5 when the second protective film 20 is bonded is less than 8% by weight. In the process of manufacturing a polarizing plate with a double-sided protective film, a moisture content reducing step S30 is performed at any one or more stages before the polarizing plate-preparing step with a double-sided protective film S20. The moisture content reduction step S <b> 30 is a step of performing a process of reducing the moisture content of the iodine polarizer 5 on the film including the iodine polarizer 5.

An example of the timing at which the moisture content reduction step S30 is performed is as follows.
1) After sticking the 1st protective film 10 on the single side | surface of the iodine type polarizer 5 which consists of a single-piece | unit (single) film, and obtaining the polarizing plate 100 with a single-sided protective film, the method of bonding the 2nd protective film 20 is carried out. If it exists, before pasting of the 1st protective film 10, after pasting (including immediately before polarizing plate production process S20 with double-sided protective film), or both. However, if the moisture content is lowered in the state of a single (single) film, the iodine-based polarizer 5 is easily torn or broken, and therefore preferably after the first protective film 10 is bonded.

  2) After obtaining the polarizing plate 100 with a single-side protective film according to the method shown in FIG. 3, in the method of laminating the second protective film 20, after the dyeing step S10-3, after the laminating step S10-4. After the peeling step S10-5 (including immediately before the polarizing plate production step S20 with a double-sided protective film), or two or more of these steps. Since it is easy to reduce the moisture content, the moisture content reducing step S30 is preferably performed at a stage where the surface of the iodine-based polarizer 5 is exposed, for example, before the bonding step S10-4 or after the peeling step S10-5. .

  For example, as in the case of performing the moisture content reduction step S30 before the bonding step S10-4 in the above 2), regardless of the above 1) or 2), the moisture content reduction step S30 and a polarizing plate with a double-sided protective film are produced. When there is a relatively long interval between step S20, take moisture absorption suppression means so that the moisture content does not become 8% by weight or more when the second protective film 20 is bonded due to moisture absorption during this interval, Alternatively, the moisture content reduction step S30 may be performed again during this interval.

  As a moisture absorption suppressing means, after finishing a method involving temporarily pasting a peelable moisture-proof film on the exposed surface of the iodine-based polarizer 5 or a process involving forming a film including the iodine-based polarizer 5 having an exposed surface. Examples include a method of winding a film in a roll shape as soon as possible to suppress the entry of moisture from the outside, and a method of further packing the roll film with a moisture-proof film such as an aluminum laminate. The method of winding in a roll shape is particularly advantageous when the film to be wound has a base film, and the base film has a low moisture permeability. Alternatively, without taking the above-described moisture absorption suppressing means, taking into consideration the moisture absorption rate of the iodine-based polarizer 5, the polarizing plate with a double-sided protective film is produced before moisture content becomes 8% by weight or more due to moisture absorption. The process may be designed so that

  For example, when there is a relatively long interval between the moisture content reduction step S30 and the polarizing plate production step S20 with a double-sided protective film, the moisture content reduction step S30 takes into account 8 in consideration of the moisture absorption rate of the iodine-based polarizer 5. The moisture content may be lowered sufficiently lower than the weight%. Also by this method, the moisture content when bonding the 2nd protective film 20 is less than 8 weight%, without taking a special means between moisture content reduction process S30 and polarizing plate preparation process S20 with a double-sided protective film. It is possible to

  As described above, a water-based adhesive can be used for laminating the iodine-based polarizer 5 and the first protective film 10, but when the water-based adhesive is used, moisture is supplied to the iodine-based polarizer 5. Therefore, it is preferable to perform the moisture content reduction step S30 after the first protective film 10 is bonded and before the second protective film 20 is bonded. In addition, this moisture content reduction process S30 does not need to be the first moisture content reduction process S30.

  From the viewpoint of heat resistance, the moisture content of the iodine-based polarizer 5 when the second protective film 20 is bonded is preferably less than 6% by weight, and more preferably 5% by weight or less. The specific method for reducing the moisture content is not particularly limited. For example, a method of blowing dry air, a method of passing through a humidity control zone adjusted to low humidity, a method of passing through a hot air drying furnace, an infrared heater, etc. And a method of heating using a simple heating device, and combinations thereof.

<Polarizing plate with double-sided protective film>
As shown in FIG. 8, the polarizing plate with a double-sided protective film according to the present invention includes an iodine-based polarizer 5, a first protective film 10 laminated on one surface thereof, and a first laminated film on the other surface. 2 protective film 20. Usually, the 1st protective film 10 and the 2nd protective film 20 are bonded (adhesion fixation) to the iodine type polarizer 5 through the 1st adhesive bond layer 15 and the 2nd adhesive bond layer 25, respectively.

In the polarizing plate with a double-sided protective film according to the present invention, the moisture content of the iodine polarizer 5 is less than 8% by weight, preferably less than 6% by weight, and more preferably 5% by weight or less. Further, the first protective film 10 and the second protective film 20 both moisture permeability 150 g / m ^2/24 hr or less, preferably 100 g / m ^2/24 hr or less of the thermoplastic resin film is used. The above description is cited for specific configurations of the iodine-based polarizer 5, the first protective film 10, and the second protective film 20.

  The polarizing plate with a double-sided protective film according to the present invention can be suitably manufactured by the method described above. Since the polarizing plate with a double-sided protective film according to the present invention has a moisture content of less than 8% by weight of the iodine-based polarizer 5 and is laminated on both surfaces with a protective film having low moisture permeability, the iodine-based polarizer 5 Even when the thickness of the film is small (for example, 10 μm or less in thickness), it has both heat and moisture resistance. The polarizing plate with a double-sided protective film can be suitably applied to an image display device such as a liquid crystal display device or an organic EL device. When applied to a liquid crystal display device, the polarizing plate with a double-sided protective film according to the present invention may be a polarizing plate disposed on the front (viewing) side of the liquid crystal cell, or disposed on the back (backlight) side. It may be a polarizing plate.

  The polarizing plate with a double-sided protective film is a pressure-sensitive adhesive layer that is laminated on the first protective film 10 or the second protective film 20 and is bonded to another member (for example, a liquid crystal cell when applied to a liquid crystal display device). May be provided. 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.

  The polarizing plate with a double-sided protective film can further include another optical layer laminated on the first protective film 10 or the second protective film 20. As another optical layer, a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light that exhibits the opposite properties; a film with an antiglare function having a concavo-convex shape on the surface; a film with a surface antireflection function A reflective film having a reflective function on the surface; a transflective film having both a reflective function and a transmissive 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, the substrate film having a thickness of 90μm made of polypropylene (melting point: 163 ° C., moisture permeability: 15g / m ² / 24hr) was subjected to corona treatment on one surface of, using a small-diameter gravure coater on the corona-treated surface above 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 surface of the primer layer of the base film having the primer layer prepared in (1) above using a die coater, and then drying at 80 ° C. for 20 minutes. Then, 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 5.3 times free end uniaxial stretching at 160 ° C. using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film. The thickness of the stretched polyvinyl alcohol resin layer was 5.1 μm.

(4) Production of polarizing laminated film (dyeing process)
The stretched film prepared in the above (3) is added to a dyeing aqueous solution at 30 ° C. containing iodine and potassium iodide (containing 0.6 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water). After immersing for 2 seconds, the polyvinyl alcohol-based resin layer was dyed, and the excess dyeing aqueous solution was washed away with pure water at 10 ° C.

  Next, it is immersed for 120 seconds in a first aqueous crosslinked solution at 78 ° C. containing boric acid (containing 10.4 parts by weight boric acid per 100 parts by weight of water), and then a 70 ° C. aqueous solution containing boric acid and potassium iodide. 2 A crosslinking treatment was performed by immersing in a crosslinking aqueous solution (containing 5.7 parts by weight of boric acid and 12 parts by weight of potassium iodide per 100 parts by weight of water) for 60 seconds. Thereafter, it was washed with pure water at 10 ° C. for 10 seconds. Finally, it was dried at 50 ° C. for 60 seconds and then at 80 ° C. for 60 seconds (moisture content reduction step) to obtain a polarizing laminated film composed of a base film / iodine polarizer. The moisture content of the iodine-type polarizer of the polarizing laminated film at the end of drying was 0.4% by weight. The iodine polarizer had a thickness of 5.6 μm.

The surface of the iodine polarizer opposite to the base film has removability so that moisture content in the air can be absorbed and moisture content of the iodine polarizer can be suppressed. the low moisture resistance film (polyolefin resin film of moisture permeability 30g / m ² / 24hr), was stuck after drying quickly. Thereby, since an iodine type polarizer is pinched | interposed by the base film and moisture proof film of a low moisture permeability, it can maintain a low moisture content.

(5) Production of multilayer film (bonding process)
Immediately (within 1 minute) while peeling the moisture-proof film from the polarizing laminated film with the moisture-proof film prepared in (4) above, the first protective film was bonded to the peeled surface. The first protective film, the moisture permeability is 16g / m ² / 24hr, using thermoplastic resin film 23μm thick made of cyclic polyolefin resin (Nippon Zeon's "ZF-14"). The first protective film is bonded using a small-diameter gravure coater so that the thickness after curing the ultraviolet curable adhesive (“KR-75T” manufactured by ADEKA Co., Ltd.) is about 1.0 μm on one side. After coating, this is bonded to the release surface using a bonding roll, and then irradiated with ultraviolet light with a cumulative amount of 200 mJ / cm ² from the base film side using a high-pressure mercury lamp and bonded. This was done by curing the agent layer.

(6) Preparation of polarizing plate with double-sided protective film (peeling step and polarizing plate with double-sided protective film)
Immediately after peeling the base film from the multilayer film produced in (5) above, a second protective film is bonded to the peeled surface, and the first protective film / adhesive layer / iodine polarizer / adhesive. A polarizing plate with a double-sided protective film comprising a layer / second protective film was obtained. The second protective film, the moisture permeability is 16g / m ² / 24hr, using thermoplastic resin film 23μm thick made of cyclic polyolefin resin (Nippon Zeon's "ZF-14"). The second protective film is bonded using a small-diameter gravure coater so that the thickness after curing an ultraviolet curable adhesive (“KR-75T” manufactured by ADEKA Co., Ltd.) on the one side is about 1.0 μm. After coating, this is bonded to the release surface using a bonding roll, and then irradiated with ultraviolet light with an integrated light amount of 200 mJ / cm ² from the second protective film side using a high-pressure mercury lamp. This was done by curing the adhesive layer. The moisture content of the iodine-type polarizer when bonding the second protective film was 0.5% by weight.

<Example 2>
A polarizing plate with a double-sided protective film was produced in the same manner as in Example 1, except that the final drying treatment (moisture content reduction step) was performed at 50 ° C. for 60 seconds and then at 65 ° C. for 60 seconds. . The moisture content of the iodine-based polarizer when the second protective film was bonded was 4.6% by weight.

<Example 3>
In the same manner as in Example 2, a polarizing plate with a double-sided protective film was produced. The moisture content of the iodine-based polarizer when the second protective film is bonded is 4.4% by weight, and the visibility correction polarization degree Py of the polarizing plate with a double-sided protection film is 99.995%, and the visibility correction single transmission is performed. The rate Ty was 40.9%.

<Example 4>
As the first protective film and second protective film, the moisture permeability is 63 g / m ^2/24 hr or, using a thermoplastic resin film having a thickness of 80μm made of an acrylic resin, an ultraviolet curable adhesive ((Ltd.) ADEKA manufactured A polarizing plate with a double-sided protective film was produced in the same manner as in Example 2 except that “KR-15P”) was used. When the second protective film is bonded, the moisture content of the iodine-based polarizer is 4.2% by weight, the visibility correction polarization degree Py of the polarizing plate with a double-sided protection film is 99.994%, and the visibility correction single transmission. The rate Ty was 41.4%.

<Example 5>
As the first protective film, a moisture permeability of 63 g / m ^2/24 hr or, a thermoplastic resin film having a thickness of 80μm made of an acrylic resin, a second protective film, the moisture permeability is 16g / m ² / 24hr, A thermoplastic resin film having a thickness of 23 μm made of a cyclic polyolefin resin (“ZF-14” manufactured by Nippon Zeon Co., Ltd.) was used. The first protective film uses an ultraviolet curable adhesive (“KR-15P” manufactured by ADEKA Corporation), and the second protective film uses “KR-75T” manufactured by an ultraviolet curable adhesive ADEKA Corporation. Except having used, it carried out similarly to Example 2, and produced the polarizing plate with a double-sided protective film. When the second protective film is bonded, the moisture content of the iodine-based polarizer is 4.8% by weight, and the visibility correction polarization degree Py of the polarizing plate with the double-sided protection film is 99.994%, and the visibility correction single transmission. The rate Ty was 41.4%.

<Comparative Example 1>
A polarizing plate with a double-sided protective film was produced in the same manner as in Example 1 except that the final drying treatment (moisture content reduction step) was performed at 40 ° C. for 60 seconds and then at 50 ° C. for 60 seconds. . The moisture content of the iodine-type polarizer when bonding the second protective film was 10.7% by weight.

<Comparative example 2>
A polarizing plate with a double-sided protective film was produced in the same manner as in Example 1 except that the final drying treatment (moisture content reduction step) was performed at 40 ° C. for 120 seconds. The moisture content of the iodine-type polarizer when bonding the second protective film was 12.5% by weight.

<Comparative Example 3>
After the final drying process (moisture content reduction process) in the dyeing process, the moisture content of the iodine-based polarizer is kept near the equilibrium moisture content by storing it for about 2 days in an environment of 25 ° C and 55% RH without laminating a moisture-proof film. Then, a polarizing plate with a double-sided protective film was produced in the same manner as in Example 2 except that the first and second protective films were bonded. The moisture content of the iodine-based polarizer when the second protective film was bonded was 15.3% by weight.

  The moisture permeability of the film and the moisture content of the iodine-based polarizer in each example and comparative example were measured by the following methods.

(1) Moisture permeability The moisture permeability at a temperature of 40 ° C. and a relative humidity of 90% was measured according to JIS Z 0208-1976 “Moisture permeability test method for moisture-proof packaging material (cup method)”.

(2) Moisture content of iodine-based polarizer The relationship between the moisture content measured by a near-infrared moisture meter ("IRMA1100S" manufactured by Chino Co., Ltd.) and the moisture content obtained by the dry weight method is a linear expression. A calibration curve to be expressed is obtained in advance from both moisture percentages obtained for a plurality of iodine-based polarizer samples having different moisture percentages, and the moisture percentage measured by a near-infrared moisture percentage meter is measured by the dry weight method using the calibration curve. In terms of the moisture content by the above, this was used as the moisture content of the iodine polarizer. The moisture content by the dry weight method is expressed by the following formula when the weight of the sample before drying is W0 and the weight when the sample is dried at 105 ° C. for 1 hour is W1:
Moisture content (% by weight) = 100 × (W0−W1) / W0
Defined by

[Evaluation of wet heat resistance and heat resistance of polarizing plate with double-sided protective film]
(1) Evaluation of wet heat resistance About the polarizing plate with double-sided protective film produced in Examples 1 and 2 and Comparative Examples 1 to 3, the visibility after a wet heat resistance test that is left in an environment of 65 ° C. and 90% RH for 500 hours The corrected polarization degree Py and the Py before the test are measured using an absorptiometer (“V7100” manufactured by JASCO Corporation), and moisture resistance is determined from the difference ΔPy between the two ΔPy (Py before the test−Py after the test). Thermal properties were evaluated. The smaller the absolute value of ΔPy, the higher the heat and moisture resistance. The results are shown in Table 1. In measuring Py, a polarizing plate sample with a double-sided protective film was set so that incident light was irradiated to the second protective film side. In addition, the visibility correction | amendment polarization degree Py after a heat-and-moisture resistance test measured after leaving still in a 23 degreeC55% RH environment for about 12 hours after a heat-and-moisture resistance test.

  Py before the wet heat resistance test (and the heat resistance test described below) was 99.995% for each of the examples and comparative examples. Moreover, the visibility-corrected single transmittance Ty measured using the same absorptiometer was 41.6% for each of the examples and the comparative examples.

(2) Evaluation of heat resistance The polarizing plate with a double-sided protective film produced in Examples 1 and 2 and Comparative Examples 1 to 3 was subjected to a heat resistance test that was allowed to stand in an environment of 85 ° C. dry for 500 hours. The heat resistance was evaluated from ΔPy (Py before the test−Py after the test) in the same manner as the evaluation of the wet heat resistance. The smaller the absolute value of ΔPy, the higher the heat resistance. The results are shown in Table 1.

(3) Evaluation of moisture and heat resistance under accelerated conditions For the polarizing plate with a double-sided protective film produced in Examples 3 to 5, the moisture and heat resistance test in which the plate was allowed to stand for 48 hours in an environment of 80 ° C. and 90% RH ) It was performed by the same method as the evaluation of heat and humidity resistance. The results are shown in Table 2.

(4) Evaluation of heat resistance under accelerated conditions About the polarizing plate with double-sided protective film produced in Examples 3-5, the heat resistance test which left still for 48 hours in 105 degreeC and dry environment is said (2) heat resistance. The same method as the evaluation of sex was performed. The results are shown in Table 2.

  Moreover, about the polarizing plate with a double-sided protective film after a heat resistance test, the degree of light leakage (red change) was confirmed visually. Specifically, two sample pieces of 10 cm × 20 cm were cut out from the polarizing plate with a double-sided protective film after the heat resistance test, and these samples were bonded to both surfaces of the glass plate using an adhesive. At this time, the second protective film side was set to the glass plate side, and the sample pieces arranged on both surfaces were set to have a crossed Nicols positional relationship. And the backlight was applied from the one polarizing plate side in the dark room, and the visual evaluation of red discoloration was performed according to the following evaluation criteria. The results are shown in Tables 1 and 2.

A: The black state is maintained and redness cannot be recognized visually.
B: Clear red discoloration is observed.

  5 iodine polarizer, 6 polyvinyl alcohol resin layer, 6 ′ stretched polyvinyl alcohol resin layer, 10 first protective film, 15 first adhesive layer, 20 second protective film, 25 second adhesive layer, 30 base film, 30 'stretched base film, 100 polarizing plate with single-sided protective film, 200 laminated film, 300 stretched film, 400 polarizing laminated film, 500 multilayer film, 600 polarizing plate with double-sided protective film.

Claims (8)

Removing the base film from the multilayer film including the base film, the iodine-based polarizer and the first protective film in this order to obtain a polarizing plate with a single-side protective film;
Bonding a second protective film to the outer surface of the iodine-based polarizer in the polarizing plate with a single-sided protective film to obtain a polarizing plate with a double-sided protective film;
Including
The first protective film and the second protective film is a thermoplastic film of less moisture permeability 150 g / m ^2/24 hr or,
The manufacturing method of the polarizing plate with a double-sided protective film whose moisture content of the said iodine type polarizer when bonding a said 2nd protective film is less than 8 weight%.   The manufacturing method of Claim 1 which bonds the said 2nd protective film to the outer surface of the said iodine type polarizer using an active energy ray hardening adhesive.   The said iodine type polarizer is a manufacturing method of Claim 1 or 2 whose thickness is 10 micrometers or less. A step of obtaining a polarizing plate with a double-sided protective film by laminating a second protective film on the outer surface of the iodine-based polarizer in the polarizing plate with a single-sided protective film including the iodine-type polarizer and the first protective film laminated on one side thereof. Including
The first protective film and the second protective film is a thermoplastic film of less moisture permeability 150 g / m ^2/24 hr or,
The manufacturing method of the polarizing plate with a double-sided protective film whose moisture content of the said iodine type polarizer when bonding a said 2nd protective film is less than 8 weight%.   The manufacturing method of Claim 4 which bonds the said 2nd protective film to the outer surface of the said iodine type polarizer using an active energy ray hardening adhesive.   The said iodine type polarizer is a manufacturing method of Claim 4 or 5 whose thickness is 10 micrometers or less. Including an iodine-based polarizer and a protective film laminated on both sides thereof,
Any protective film to be laminated on both sides, a thermoplastic resin film of less moisture permeability 150g / m ² / 24hr,
A polarizing plate with a double-sided protective film, wherein the iodine polarizer has a moisture content of less than 8% by weight.   The polarizing plate with a double-sided protective film according to claim 7, wherein the iodine-based polarizer has a thickness of 10 μm or less.

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