KR102441217B1 - Method for producing polarizing plate having protective films on both surfaces thereof - Google Patents

Abstract

A step of peeling and removing the base film from the multilayer film comprising a base film, an iodine-based polarizer, and a first protective film in this order, and a step of bonding a second protective film to the outer surface of the iodine-based polarizer; The second protective film is a thermoplastic resin film having a water vapor transmission rate of 150 g/m 2 /24 hr or less, and the moisture content of the iodine-based polarizer at the time of bonding the second protective film is less than 8% by weight. A polarizing plate with a double-sided protective film in which a thermoplastic resin film having a water vapor transmission rate of 150 g/m 2 /24 hr or less is laminated on both surfaces of this iodine-based polarizer of less than 8% by weight is provided.

Description

The manufacturing method of a polarizing plate with a double-sided protective film {METHOD FOR PRODUCING POLARIZING PLATE HAVING PROTECTIVE FILMS ON BOTH SURFACES THEREOF}

The present invention relates to a method for manufacturing a polarizing plate with double-sided protective film in which protective films are bonded to both sides of an iodine-based polarizer, and more particularly, to a double-sided protective film by sequentially bonding protective films with low moisture permeability to both surfaces of an iodine-based polarizer. It relates to a method of manufacturing an attached polarizing plate.

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

Polarizer itself has low heat-and-moisture resistance, and it is easy to deteriorate a polarization|polarized-light characteristic in a moist-heat environment. Conventionally, a triacetyl cellulose film has been used as a protective film for protecting a polarizer. However, since a triacetyl cellulose film has a high water vapor transmission rate, the polarizing plate using this for a protective film is particularly resistant to moisture and heat when an iodine-based polarizer is used as the polarizer. There was a problem that this is still not enough.

Then, in order to improve the heat-and-moisture resistance of a polarizing plate, instead of a triacetyl cellulose film, bonding a protective film with low moisture permeability, such as a norbornene-type resin film, to an iodine-type polarizer is proposed [for example, Unexamined-Japanese-Patent No. 2004 Paragraph [0005] of Publication No. 245925 (Patent Document 1)].

Patent Document 1: Japanese Patent Laid-Open No. 2004-245925

Since penetration of moisture from the outside is reduced when a protective film with a low moisture permeability is bonded to both surfaces of an iodine-type polarizer, the heat-and-moisture resistance of a polarizing plate can be improved. However, on the other hand, conventional polarizing plates with double-sided protective films using protective films with such a low moisture permeability on both sides are subjected to a heat resistance test exposed to a higher temperature environment than a general heat-and-moisture resistance test, light leakage (discoloration) under cross nicol. Therefore, it became clear by examination of the present inventors that light in a red region leaks from a polarizing plate, and a polarizing plate looks red (also called redness.) arises, or a polarization characteristic falls. The problem of this heat resistance defect is so remarkable that the thickness of an iodine type polarizer is small.

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

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

The process of bonding a 2nd protective film to the outer surface of the iodine type polarizer in the said polarizing plate with a single-sided protective film, and obtaining a polarizing plate with a double-sided protective film

including,

The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m 2 /24 hr or less,

The manufacturing method of the polarizing plate with double-sided protective film whose moisture content of the said iodine type polarizer at the time of 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 the outer surface of the iodine-based 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] In a polarizing plate with a single-sided protective film comprising an iodine-based polarizer and a first protective film laminated on one side thereof, bonding a second protective film to the outer surface of the iodine-based polarizer to obtain a polarizing plate with double-sided protective film; do,

The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m 2 /24 hr or less,

The manufacturing method of the polarizing plate with double-sided protective film whose moisture content of the said iodine type polarizer at the time of 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 the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive.

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

[7] comprising an iodine-based polarizer and a protective film laminated on both surfaces thereof,

All of the protective films laminated on both sides are thermoplastic resin films with a moisture permeability of 150 g/m 2 /24 hr or less,

The polarizing plate with a double-sided protective film whose moisture content of the said iodine-type polarizer is less than 8 weight%.

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

According to the present invention, a method for manufacturing a polarizing plate with a protective film on both sides of an iodine-based polarizer bonded to a protective film having low moisture permeability on both surfaces thereof, which has both heat and moisture resistance and heat resistance, and a method for producing a polarizing plate with a protective film on both sides of an iodine-based polarizer having low moisture permeability on both surfaces of the iodine-based polarizer As a polarizing plate to which the protective film was bonded, the polarizing plate with a double-sided protective film which has both heat-and-moisture resistance and heat resistance can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS 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 layer structure of a 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 by the resin layer formation process.
It is a schematic sectional drawing which shows an example of the layer structure of the stretched film obtained by an extending process.
It is a schematic sectional drawing which shows an example of the layer structure of the light-polarizing laminated film obtained by a dyeing process.
It is a schematic sectional drawing which shows an example of the laminated constitution of the multilayer film obtained by a bonding process.
It is a schematic sectional drawing which shows an example of the layer structure of the polarizing plate with double-sided protective film which concerns on this invention.

<Method for producing a polarizing plate with double-sided protective film>

As shown in FIG. 1, the manufacturing method of the polarizing plate with double-sided protective film which concerns on this invention may include the following process.

(1) Step S10 of preparing a polarizing plate with a single-sided protective film comprising an iodine-based polarizer and a first protective film laminated on one side thereof (hereinafter also referred to as “polarizing plate preparation step S10 with a single-sided protective film”), and

(2) Step S20 of 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 (hereinafter also referred to as “polarizing plate with double-sided protective film production step S20”).

As described above, in the present invention, the first protective film and the second protective film are successively bonded to the iodine-based polarizer. In that case, in order to improve the heat-and-moisture resistance of the polarizing plate with double-sided protective film obtained, as a 1st protective film bonded to one surface of an iodine type polarizer, and a 2nd protective film bonded to the other surface, a water vapor transmission rate is 150 g/m<2> A thermoplastic resin film with a low moisture permeability of /24 hr or less is used.

Moreover, in order to improve the heat resistance of the polarizing plate with double-sided protective film obtained, the moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film to an iodine-type polarizer shall be less than 8 weight%. In the present invention, in order to improve heat-and-moisture resistance, a protective film having a low moisture permeability is bonded to both surfaces of an 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 be dissipated to the outside, and the moisture collects in the iodine-based polarizer;

b) Redness in the heat resistance test and deterioration of polarization characteristics are caused by moisture remaining in the iodine-based polarizer.

It is effective to manage the moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film as mentioned above from such situations. The moisture content of the iodine-based polarizer is measured according to the method described in the section of Examples.

The moisture content of the iodine-based polarizer is determined in any one of the steps before bonding the second protective film to the iodine-based polarizer during the process of manufacturing a polarizing plate with a double-sided protective film, (3) with respect to the film containing the iodine-based polarizer. This can be achieved by providing step S30 (hereinafter, also referred to as "water content reduction step S30") of performing a moisture content reduction process (refer FIG. 1).

Hereinafter, each process is demonstrated, referring FIGS. 2-8.

(1) Polarizing plate with single-sided protective film preparation step S10

This step is a step of preparing (for) a polarizing plate 100 with a protective film on one side as shown in Fig. 2, for example, including the iodine polarizer 5 and the first protective film 10 laminated on one side . As shown in FIG. 2 , the first protective film 10 is usually bonded (adhesive and fixed) to one side of the iodine-based polarizer 5 via the first adhesive layer 15 .

[Iodine-based polarizer]

The iodine-based polarizer 5 is a polarizer in which iodine is adsorbed and oriented as a dichroic dye, and specifically, it may be a uniaxially stretched polyvinyl alcohol-based resin layer (or film) in which iodine is adsorbed and oriented. The thickness of the iodine-based polarizer 5 may be, for example, 30 µm or less, further 20 µm or less, but in particular for mobile devices, from the viewpoint of thinning the polarizing plate with double-sided protective film, it is preferably 10 µm or less, and 8 µm or less more preferably. The thickness of the iodine-type polarizer 5 is 2 micrometers or more normally.

When the thickness of the iodine-based polarizer 5 is reduced, the concentration of iodine becomes higher and the concentration of the iodine complex existing in the vicinity of the interface with the protective film laminated on both surfaces also increases, so that it is easily affected by moisture entering from the outside. . Therefore, heat-and-moisture resistance tends to become low, so that the thickness of the iodine-type polarizer 5 is small. Moreover, when the thickness of the iodine-type polarizer 5 becomes small and the density|concentration of iodine becomes higher, it becomes easy to be influenced by the water|moisture content remaining in the iodine-type polarizer, and heat resistance also becomes low easily. As described above, the smaller the thickness of the iodine-based polarizer 5, the lower the heat resistance and heat resistance. The present invention is particularly advantageous when the thickness of the iodine-based polarizer 5 is small.

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

In this specification, "(meth)acryl" means at least one chosen from acryl and methacryl. It is the same also when saying "(meth)acryloyl" etc.

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

Although the saponification degree of polyvinyl alcohol-type resin may be the range of 80.0-100.0 mol%, Preferably it is the range of 90.0-99.5 mol%, More preferably, it is the range of 94.0-99.0 mol%. The water resistance and heat-and-moisture resistance of the polarizing plate with double-sided protective film obtained as saponification degree is less than 80.0 mol% fall. When saponification degree uses polyvinyl alcohol-type resin more than 99.5 mol%, the dyeing rate of iodine becomes slow, productivity falls, and the iodine-type polarizer 5 which has sufficient polarization performance may not be obtained.

The degree of saponification refers to the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, changed to a hydroxyl group by the saponification process in unit ratio (mol%). , the formula:

Saponification degree (mol%) = 100 x (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetic acid groups)

is defined as Saponification degree can be calculated|required based on JISK6726-1994. The higher the degree of saponification, the higher the proportion of hydroxyl groups, and therefore, the lower the proportion of acetic acid groups that inhibit crystallization.

The polyvinyl alcohol-type resin may be modified|denatured polyvinyl alcohol by which a part was modified|denatured. For example, polyvinyl alcohol-type resin is olefins, such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; What modified|denatured with the alkylester of unsaturated carboxylic acid, (meth)acrylamide, etc. is mentioned. It is preferable that it is less than 30 mol%, and, as for the ratio of modification|denaturation, it is more preferable that it is less than 10 %. When it modifies|denatures more than 30 mol%, it becomes difficult to adsorb|suck iodine, and there exists a tendency for it difficult to obtain the iodine type polarizer 5 which has sufficient polarization|polarized-light performance.

The average polymerization degree of polyvinyl alcohol-type resin becomes like this. Preferably it is 100-10000, More preferably, it is 1500-8000, More preferably, it is 2000-5000. The average degree of polymerization of polyvinyl alcohol-type resin can also be calculated|required based on JISK6726-1994.

[First Protective Film]

The first protective film 10 is a film made of a light-transmitting (preferably optically transparent) thermoplastic resin and having a water vapor transmission rate of 150 g/m 2 /24 hr or less. Moisture permeability is a water vapor transmission rate at a temperature of 40° C. and a relative humidity of 90% measured in accordance with JIS Z 0208-1976 “Test method for moisture permeability of moisture-proof packaging material (cup method)” including the moisture permeability of the second protective film to be described later. The moisture permeability is preferably 100 g/m 2 /24 hr or less.

As a means for setting the moisture permeability of the first protective film 10 to 150 g/m 2 /24 hr or less, a thermoplastic resin constituting the film having low moisture permeability is used, the thickness of the film is increased, or the moisture permeability is low on the film. providing a barrier layer is mentioned.

The thermoplastic resin constituting the first protective film 10 is not particularly limited as long as it can achieve the above-described moisture permeability, but has low moisture permeability and can reduce the thickness of the first protective film 10, so that the chain polyolefin-based resin polyolefin-based resins such as resins (such as polypropylene-based resins) and cyclic polyolefin-based resins (such as norbornene-based resins); polyester-based resins such as polyethylene terephthalate-based resins; polycarbonate-based resin; (meth)acrylic resin; polystyrene-based resin; Or a mixture thereof, a copolymer, etc. are used preferably.

The first protective film 10 may be a protective film having an optical function such as a retardation film or a brightness improving film. For example, the retardation film to which arbitrary retardation values were provided can be made by extending|stretching (uniaxial stretching, biaxial stretching, etc.) the film which consists of the said thermoplastic resin, or forming a liquid crystal layer etc. on the film.

Examples of the chain-type polyolefin-based resin include homopolymers of chain-type olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain-type olefins.

The cyclic polyolefin-based resin is a generic term for a resin that is polymerized by using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and a chain olefin such as ethylene and propylene (typically a random copolymer), and these graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among them, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers are preferably used as cyclic olefins.

The polyester-based resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyhydric carboxylic acid or a derivative thereof and a polyhydric alcohol. As polyhydric carboxylic acid or its derivative(s), dicarboxylic acid or its derivative(s) can be used, For example, terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalenedicarboxylic acid, etc. are mentioned. Diol can be used as polyhydric alcohol, For example, ethylene glycol, propanediol, butanediol, neopentyl glycol, cyclohexane dimethanol, etc. are mentioned.

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

The polycarbonate-based resin is composed of a polymer to which a monomer unit is bonded through a carbonato group. The polycarbonate-based resin may be a resin called a modified polycarbonate in which a polymer skeleton is modified, a copolymer polycarbonate, or the like.

(meth)acrylic-type resin is resin which uses the compound which has a (meth)acryloyl group as a main structural monomer. Specific examples of the (meth)acrylic resin 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 acid ester-(meth)acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); and copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylate norbornyl copolymer, etc.). Preferably, a polymer containing poly(meth)acrylic acid C _1-6 alkylester as a main component, such as poly(meth)methyl acrylate, is used, and more preferably, methyl methacrylate as the main component (50 to 100% by weight, Preferably 70-100 weight%) methyl methacrylate-type resin is used.

On the surface on the opposite side to the iodine-based polarizer 5 in the first protective film 10, a hard coat layer, an anti-glare layer, an anti-reflection layer, an anti-static layer, and a surface treatment layer (coating layer) such as an anti-fouling layer may be formed. . The method of forming a surface treatment layer is not specifically limited, A well-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.

The thickness of the first protective film 10 is preferably 90 µm or less, more preferably 50 µm or less, still more preferably 30 µm or less from the viewpoint of reducing the thickness of the polarizing plate with 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 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 . Examples of the adhesive for forming the first adhesive layer 15 include an active energy ray-curable adhesive (preferably an ultraviolet curable adhesive) containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays; It may be a water-based adhesive in which an adhesive component such as a polyvinyl alcohol-based resin is dissolved and dispersed in water.

The curable compound may be a cationically polymerizable curable compound or a radical polymerizable curable compound. Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or two or more epoxy groups in a molecule), an oxetane compound (a compound having one or two or more oxetane rings in a molecule), or these can be a combination of Examples of the radical polymerizable curable compound include (meth)acrylic compounds (compounds having one or two or more (meth)acryloyloxy groups in the molecule) and other vinyl compounds having radical polymerizable double bonds; or a combination thereof. You may use together a cationically polymerizable sclerosing|hardenable compound, and a radically polymerizable sclerosing|hardenable compound. An active energy ray-curable adhesive agent further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating the hardening reaction of the said curable compound normally.

The polarizing plate 100 with a single-sided protective film may be prepared beforehand, and may be manufactured according to arbitrary methods. As a manufacturing method, the following is mentioned.

i) a method of bonding the first protective film 10 to one side of the iodine-based polarizer 5 made of a single (single) film manufactured according to a known method, and

ii) A manufacturing method including the following steps as shown in FIG. 3 .

After coating the coating liquid containing the polyvinyl alcohol-type resin on at least one surface of the base film, the polyvinyl alcohol-type resin layer is formed by drying, and the resin layer forming process S10-1 which obtains a laminated|multilayer film;

Stretching step S10-2 of stretching a laminated film to obtain a stretched film;

Dyeing step S10-3 of dyeing the polyvinyl alcohol-based resin layer of the stretched film with iodine to form an iodine-based polarizer to obtain a light-polarizing laminated film;

Bonding process S10-4 which bonds the 1st protective film 10 on the iodine-type polarizer of a light-polarizing laminated film to obtain a multilayer film, and

Peeling process S10-5 which peels and removes a base film from a multilayer film, and obtains the polarizing plate 100 with a single-sided protective film.

[Resin Layer Forming Step S10-1]

With reference to FIG. 4, this process is a process of forming the polyvinyl alcohol-type resin layer 6 in at least one surface of the base film 30, and obtaining the laminated|multilayer film 200. This polyvinyl alcohol-type resin layer 6 is a layer used as the iodine-type polarizer 5 through extending|stretching process S10-2 and dyeing|staining process S10-3. The polyvinyl alcohol-based resin layer 6 can be formed by coating a coating liquid containing a polyvinyl alcohol-based resin on one or both surfaces of the base film 30 and drying. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that it is easy to obtain the thin-film iodine-based polarizer 5 .

The base film 30 may be composed of a thermoplastic resin, and among them, it is preferable to be composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include, for example, polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (norbornene-based resins, etc.); polyester-based resin; (meth)acrylic resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; polycarbonate-based resin; polyvinyl alcohol-based resin; polyvinyl acetate-based resin; polyarylate-based resins; polystyrene-based resin; polyether sulfone-based resin; polysulfone-based resin; polyamide-based resin; polyimide-based resin; and mixtures and copolymers thereof.

The single layer structure which consists of one resin layer which consists of 1 type, or 2 or more types of thermoplastic resins may be sufficient as the base film 30, The multilayer structure which laminated|stacked the resin layer which consists of 1 type or 2 or more types of thermoplastic resins may be sufficient as it. It is preferable that the base film 30 is comprised from resin which can extend|stretch at the extending|stretching temperature suitable for extending|stretching the polyvinyl alcohol-type resin layer 6 in extending process S10-2 mentioned later.

The base film 30 may contain an additive. Specific examples of the additive include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments and colorants.

The thickness of the base film 30 is usually 1-500 µm in terms of strength and handleability, preferably 1-300 µm, more preferably 5-200 µm, still more preferably 5-150 µm. .

The coating solution to be coated on the base film 30 is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a polyvinyl alcohol-based resin powder in a good solvent (eg, water). The detail of polyvinyl alcohol-type resin is as above-mentioned. The coating liquid may contain additives, such as a plasticizer and surfactant, as needed.

A method of coating the coating solution on the base film 30 includes a wire bar coating method; roll coating methods such as reverse coating and gravure coating; die coat method; comma coat method; lip coat method; spin coating method; screen coating method; Fountain coating method; dipping method; It can select suitably from methods, such as 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. 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-type resin layer 6 may be provided only in one side of the base film 30, and may be formed in both surfaces. When it is formed on both sides, curling of the film that may occur during the manufacture of the light-polarizing laminated film 400 (see FIG. 6 ) can be suppressed, and two polarizing plates can be obtained from one light-polarizing laminated film 400 . , which is advantageous in terms of production efficiency.

The thickness of the polyvinyl alcohol-type resin layer 6 in the laminated|multilayer film 200 becomes like this. Preferably it is 3-30 micrometers, More preferably, it is 5-20 micrometers. In the case of the polyvinyl alcohol-based resin layer 6 having a thickness within this range, through the stretching step S10-2 and the dyeing step S10-3 described later, the dyeability of iodine is good, the polarization performance is excellent, and it is sufficiently thin (for example, The iodine-based polarizer 5 (with a thickness of 10 µm or less) can be obtained.

Prior to coating of the coating solution, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, at least the surface of the base film 30 on the side where the polyvinyl alcohol-based resin layer 6 is formed. Then, corona treatment, plasma treatment, flame (flame) treatment, etc. may be performed. For the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 30 through a primer layer or the like.

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of the base film 30 and then drying. This coating liquid contains a component which exhibits a strong adhesive force to a certain extent to both of the base film 30 and the polyvinyl alcohol-type resin layer 6, and usually contains the resin component and solvent which provide this adhesive force. As a resin component, Preferably, the thermoplastic resin excellent in transparency, thermal stability, ductility, etc. is used, For example, (meth)acrylic-type resin, polyvinyl alcohol-type resin, etc. are mentioned. Especially, polyvinyl alcohol-type resin which provides favorable adhesive force is used preferably. More preferably, it is polyvinyl alcohol resin. As the solvent, a general organic solvent or aqueous solvent capable of dissolving the resin component is usually used, but it is preferable to form the primer layer from a coating solution using water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming the primer layer. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (eg, metal salts, metal oxides, metal hydroxides, organometallic compounds), and polymer-based crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based cross-linking agent, a metal chelate compound-based cross-linking agent, or the like is preferably used.

It is preferable that it is about 0.05-1 micrometer, and, as for the thickness of a primer layer, it is more preferable that it is 0.1-0.4 micrometer. When it becomes thinner than 0.05 micrometer, the effect of the adhesive force improvement of the base film 30 and the polyvinyl alcohol-type resin layer 6 is small, and when it becomes thicker than 1 micrometer, it is disadvantageous to thickness reduction of the polarizing plate with a double-sided protective film.

A method of coating the coating solution for forming the primer layer on the base film 30 may 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 coating liquid for forming a primer layer is, for example, 50 to 200°C, preferably 60 to 150°C. When the solvent contains water, the drying temperature is preferably 80°C or higher.

[Stretching step S10-2]

This process with reference to FIG. 5 is a process of extending|stretching the laminated|multilayer film 200, and obtaining the stretched film 300 which consists of the stretched base film 30' and the polyvinyl alcohol-type resin layer 6'. An extending|stretching process is uniaxial stretching normally.

Although the draw ratio of the laminated|multilayer film 200 can be suitably selected according to the desired polarization characteristic, Preferably, it is more than 5 times and 17 times or less with respect to the original length of the laminated|multilayer film 200, More preferably, it exceeds 5 times. less than 8 times. Since the polyvinyl alcohol-type resin layer 6' does not fully orientate that a draw ratio is 5 times or less, the polarization degree of the iodine type polarizer 5 may not become high enough. On the other hand, when the draw ratio exceeds 17 times, breakage of the film tends to occur during stretching, the thickness of the stretched film 300 becomes thinner than necessary, and there is a fear that workability and handleability in a subsequent step may be reduced.

The stretching treatment may be performed in multiple stages without being limited to stretching in one stage. In this case, all of the multi-step stretching treatment may be continuously performed before the dyeing step S10-3, and the stretching treatment after the second step may be performed simultaneously with the dyeing treatment and/or the crosslinking treatment in the dyeing step S10-3. . Thus, when performing an extending|stretching process in multiple steps, it is preferable to perform an extending|stretching process so that it may become a draw ratio of more than 5 times in total of all the stages of an extending|stretching process.

The stretching treatment may be longitudinal stretching stretching in the film longitudinal direction (film conveyance direction), and transverse stretching or diagonal stretching stretching in the film width direction may be used. Examples of the longitudinal stretching method include inter-roll stretching performed using rolls, compression stretching, and stretching using a chuck (clip), and examples of the transverse stretching method include a tenter method. As the stretching treatment, any of a wet stretching method and a dry stretching method can be employed.

The stretching temperature is set above the temperature at which the polyvinyl alcohol-based resin layer 6 and the entire base film 30 exhibit fluidity to the extent that they can be stretched, and preferably the phase transition temperature (melting point or glass transition temperature) of the base film 30 . ) 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 is formed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

When the stretching temperature is lower than -30°C of the phase transition temperature, high magnification stretching of more than 5 times is difficult to be achieved, or the fluidity of the base film 30 is too low, and stretching treatment tends to be difficult. When extending|stretching temperature exceeds +30 degreeC of a phase transition temperature, there exists a tendency for the fluidity|liquidity of the base film 30 to become too large and extending|stretching becomes 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|multilayer film 200 in an extending|stretching process, it is a zone heating method (For example, the method of heating in the same extending|stretching zone as the heating furnace adjusted to predetermined temperature by blowing hot air); In the case of stretching using a roll, a method of heating the roll itself; There is a heater heating method (a method in which an infrared heater, a halogen heater, a panel heater, etc. are installed above and below the laminated film 200 and heated by radiant heat) and the like. In the stretching method between rolls, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature.

Prior to extending|stretching process S10-2, you may provide the preheating process process of preheating the laminated|multilayer film 200. As a preheating method, the method similar to the heating method in an extending|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 in the stretching temperature.

In addition, you may provide a heat setting treatment process after the extending process in extending process S10-2. A heat setting process is a process which heat-processes above the crystallization temperature, maintaining the edge part of the stretched film 300 in a tension state in the state hold|gripped with the clip. Crystallization of the polyvinyl alcohol-type resin layer 6' is accelerated|stimulated by this heat setting process. It is preferable that it is the range of -0 degreeC - -80 degreeC of extending|stretching temperature, and, as for the temperature of a heat setting process, it is more preferable that it is the range of -0 degreeC - -50 degreeC of extending|stretching temperature.

[Dyeing step S10-3]

With reference to FIG. 6 , this step is a step of dyeing the polyvinyl alcohol-based resin layer 6 ′ of the stretched film 300 with iodine and adsorbing and aligning it to obtain an iodine-based polarizer 5 . Through this process, the light-polarizing laminated film 400 in which the iodine-type polarizer 5 was laminated|stacked on one side or both surfaces of the base film 30' is obtained.

A dyeing process can be performed by immersing the stretched film 300 in the solution (dyeing solution) containing an iodine. As a dyeing solution, the solution which melt|dissolved iodine in the solvent can be used. As the solvent, generally water is used, but an organic solvent compatible with water may be further added. The density|concentration of the iodine in a dyeing solution becomes like this. Preferably it is 0.01 to 10 weight%, More preferably, it is 0.02 to 7 weight%.

Since the dyeing efficiency can be improved, it is preferable to further add iodide to the dyeing solution. Examples of the 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. The density|concentration of the iodide in a dyeing solution becomes like this. Preferably it is 0.01 to 20 weight%. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is in a weight ratio, preferably 1:5 to 1:100, and more preferably 1:6 to 1:80. The temperature of a dyeing solution becomes like this. Preferably it is 10-60 degreeC, More preferably, it is 20-40 degreeC.

In addition, although it is also possible to perform dyeing process S10-3 before extending process S10-2, or to perform these processes simultaneously, in order to orientate favorably the iodine adsorbed to the polyvinyl alcohol-type resin layer, laminated|multilayer film 200 ), it is preferable to perform the dyeing process S10-3 after performing the extending|stretching process to a certain extent at least.

Dyeing step S10-3 may include a crosslinking treatment step performed following the dyeing treatment. A crosslinking process can be performed by immersing the dyed film in the solution (crosslinking solution) which melt|dissolved the crosslinking agent in the solvent. Examples of the crosslinking agent include boric acid and boron compounds such as borax, glyoxal and glutaraldehyde. Only 1 type may be used for a crosslinking agent, and 2 or more types may be used together. Although water can be used as a solvent of a crosslinking solution, you may further contain the organic solvent compatible with water. The density|concentration of the crosslinking agent in a crosslinking solution becomes like this. Preferably it is 1 to 20 weight%, More preferably, it is 6 to 15 weight%.

The crosslinking solution may further contain iodide. By addition of iodide, the polarization|polarized-light performance in the surface of the iodine type polarizer 5 can be made uniform more. Specific examples of iodide are the same as described above. The density|concentration of the iodide in a crosslinking solution becomes like this. Preferably it is 0.05 to 15 weight%, More preferably, it is 0.5 to 8 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 of immersing in a crosslinking solution twice or more 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. A washing process usually includes a water washing process. The water washing process can be performed by immersing the film after a dyeing process or a crosslinking process in pure water, such as ion-exchange water and distilled water. Water washing temperature is 3-50 degreeC normally, Preferably it is 4-20 degreeC. The washing process may be a combination of a water washing process and a washing process with an iodide solution. As a drying process performed after a washing|cleaning process, arbitrary suitable methods, such as natural drying, air drying, and heat drying, are employable. For example, in the case of heat drying, the drying temperature is usually 20 to 95°C.

[Joining step S10-4]

With reference to FIG. 7 , this step is performed on the iodine-based polarizer 5 of the light-polarizing laminated film 400 , that is, the first adhesive layer on the surface opposite to the base film 30 ′ of the iodine-based polarizer 5 . It is a process of obtaining the multilayer film 500 by bonding the 1st protective film 10 through (15). The adhesive forming the first adhesive layer 15 is the same as described above.

In addition, when the light-polarizing laminated film 400 has the iodine-based polarizer 5 on both surfaces of the base film 30', the first protective film 10 is usually formed on the iodine-based polarizer 5 on both surfaces. are joined In this case, the protective film of the same type may be sufficient as these 1st protective films 10, and a different type of protective film may be sufficient as them.

When the first protective film 10 is bonded using an active energy ray-curable adhesive, the first protective film 10 is applied to the iodine-based polarizer 5 through an active energy ray-curable adhesive serving as the first adhesive layer 15 . After lamination, the adhesive layer is cured by irradiating active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Among them, ultraviolet light is suitable, and as a light source in this case, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, etc. can be used. When using a water-based adhesive, after laminating|stacking the 1st protective film 10 on the iodine-type polarizer 5 via a water-based adhesive, what is necessary is just to heat-dry.

In bonding the first protective film 10 to the iodine-based polarizer 5 , the bonding surface of the first protective film 10 and/or the iodine-based polarizer 5 has adhesiveness with the iodine-based polarizer 5 . In order to improve the surface treatment (easy-adhesion treatment) such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, among others, plasma treatment, corona treatment or saponification treatment It is preferable to perform the treatment.

[Peeling Step S10-5]

This step is a step of peeling and removing the base film 30 ′ from the multilayer film 500 . Through this process, the polarizing plate 100 with a single side|surface protective film similar to FIG. 2 is obtained. When the light-polarizing laminated film 400 has iodine-based polarizers 5 on both surfaces of the base film 30', and the first protective film 10 is bonded to both iodine-based polarizers 5, this By peeling process S50, the polarizing plate 100 with a single-sided protective film of 2 sheets is obtained from the light-polarizing laminated film 400 of 1 sheet.

The method of peeling and removing the base film 30' is not specifically limited, It can peel by the method similar to the peeling process of the separator (peelable film) performed with a normal polarizing plate with an adhesive. The base film 30' may peel immediately after bonding process S10-4, as it is, and may peel once after bonding process S10-4, winding up in roll shape, and unwinding in a subsequent process.

(2) Polarizing plate with double-sided protective film manufacturing process S20

In this process, a 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 a 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 2nd protective film 20 is bonded (adhesive and fixed) to the iodine-type polarizer 5 via the 2nd adhesive bond layer 25 normally. The outer surface of the iodine-based polarizer 5 means a surface on the opposite side to the first protective film 10 in the iodine-based polarizer 5, and one side is protected through a step of peeling and removing the base film 30'. When producing the polarizing plate 100 with a film, the surface of the iodine-type polarizer 5 exposed by peeling and removal of the base film 30' is meant.

The second protective film 20, like the first protective film 10, is also made of a light-transmitting (preferably optically transparent) thermoplastic resin and has a water vapor transmission rate of 150 g/m 2 /24 hr or less. . The protective film which has optical functions like retardation film and a brightness improving film together may be sufficient. As for the thickness, material, etc. of the surface treatment layer and the film that the second protective film 20 may have, the above description of the first protective film 10 is cited. The 1st protective film 10 and the 2nd protective film 20 may be mutually the protective film which consists of the same kind of resin, and the protective film which consists of different kinds of resin may be sufficient as them.

The adhesive forming the second adhesive layer 25 may be an active energy ray-curable adhesive or a water-based adhesive, similarly to the first adhesive layer 15, but is preferably an active energy ray-curable adhesive such as an ultraviolet curable adhesive. When a water-based adhesive is used, moisture is supplied to the iodine-based polarizer 5, so there is a case where the moisture content of the iodine-based polarizer 5 when bonding the second protective film 20 is not less than 8% by weight. have. The adhesive agent which forms the 2nd adhesive bond layer 25 may have the same composition as the adhesive agent which forms the 1st adhesive bond layer 15, and may have a different composition.

(3) Water content reduction step S30

In the manufacturing method of the polarizing plate with double-sided protective film which concerns on this invention, in order to make the moisture content of the iodine-type polarizer 5 at the time of bonding the 2nd protective film 20 less than 8 weight%, the double-sided protective film as described above. In the process of manufacturing a polarizing plate with a double-sided protective film, the moisture content reduction process S30 performed in any one or more steps before the manufacturing process S20 of a polarizing plate with a double-sided protective film is included. Moisture content reduction process S30 is a process of performing the process which reduces the moisture content of the iodine-type polarizer 5 with respect to the film containing the iodine-type polarizer 5.

An example of the timing which implements moisture content reduction process S30 is as follows.

1) bonding the first protective film 10 to one side of the iodine-based polarizer 5 made of a single (single) film to obtain a polarizing plate 100 with a single side protective film, and then bonding the second protective film 20 In a method, before bonding of the 1st protective film 10, after bonding (including immediately before the polarizing plate production process S20 with a double-sided protective film), or these both. However, since the iodine-based polarizer 5 is torn or easily fractured when the moisture content is lowered in the state of a single (single) film, preferably after bonding of the first protective film 10 .

2) After obtaining the polarizing plate 100 with a single-sided protective film according to the method shown in FIG. 3, in the method of bonding the 2nd protective film 20, it peels after dyeing process S10-3, after bonding process S10-4, and After step S10-5 (including immediately before step S20 of producing a polarizing plate with double-sided protective film), or two or more steps of these. Since it is easy to reduce a moisture content, it is preferable to perform moisture content reduction process S30 at the stage in which the surface of the iodine-type polarizer 5 is exposed, for example, before bonding process S10-4, or after peeling process 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), a relatively long When there is an interval, a moisture absorption suppression means is devised so that the moisture content during bonding of the second protective film 20 does not become 8% by weight or more due to moisture absorption during this interval, or a moisture content reduction step S30 again during this interval may be performed.

As a means for suppressing moisture absorption, a method of temporarily bonding a peelable moisture-proof film to the exposed surface of the iodine-based polarizer 5, or a process involving the formation of a film containing the iodine-based polarizer 5 having an exposed surface is completed. As soon as possible, a method of winding the film in a roll shape to suppress the intrusion of moisture from the outside, a method of further packing the roll-shaped film with a moisture-proof film such as an aluminum laminate, etc. are mentioned. The method of winding in roll shape is particularly advantageous when the film to be wound has a base film and this base film has low moisture permeability. Alternatively, without taking into account the moisture absorption rate of the iodine-based polarizer 5, the polarizing plate with double-sided protective film production step S20 is performed before the moisture content becomes 8 wt% or more due to moisture absorption, without particularly taking the above moisture absorption suppression means. The process may be designed to do this.

Further, for example, when there is a relatively long interval between the moisture content reduction step S30 and the polarizing plate with double-sided protection film production process S20, in consideration of the moisture absorption rate of the iodine-based polarizer 5, in the moisture content reduction step S30, sufficiently lower than 8 wt% You can also lower the moisture content. Also by this method, it is possible to make the moisture content at the time of bonding the 2nd protective film 20 into less than 8 weight% without taking special means between the moisture content reduction process S30 and the polarizing plate manufacturing process S20 with a double-sided protective film. do.

As described above, a water-based adhesive can be used for bonding 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, so It is preferable to perform moisture content reduction process S30 between bonding the 2nd protective film 20 after bonding the 1 protective film 10. In addition, this moisture content reduction process S30 does not need to be the first moisture content reduction process S30.

It is preferable that it is less than 6 weight%, and, as for the moisture content of the iodine-type polarizer 5 at the time of bonding the 2nd protective film 20 from a heat resistant viewpoint, it is more preferable that it is 5 weight% or less. A specific method for reducing the moisture content is not particularly limited, and for example, a method of spraying dry air, a method of passing a humidity control zone adjusted to low humidity, a method of passing a hot air drying furnace, using a heating device such as an infrared heater heating method, and combinations thereof.

<Polarizing plate with double-sided protective film>

The polarizing plate with double-sided protective film which concerns on this invention, as shown in FIG. 8, the iodine type polarizer 5, the 1st protective film 10 laminated|stacked on the one side, and the agent laminated|stacked on the other side. 2 to include a protective film (20). Usually, the first protective film 10 and the second protective film 20 are bonded (adhesive and fixed) to the iodine-based polarizer 5 through the first adhesive layer 15 and the second adhesive layer 25, respectively. .

The polarizing plate with double-sided protective film which concerns on this invention WHEREIN: The moisture content of the iodine type polarizer 5 is less than 8 weight%, Preferably it is less than 6 weight%, More preferably, it is 5 weight% or less. In addition, a thermoplastic resin film with a water vapor transmission rate of 150 g/m 2 /24 hr or less, preferably 100 g/m 2 /24 hr or less is used for the 1st protective film 10 and the 2nd protective film 20 together. About the specific structure of the iodine-type polarizer 5, the 1st protective film 10, and the 2nd protective film 20, the above description is quoted.

The polarizing plate with double-sided protective film which concerns on this invention can be manufactured suitably according to the method demonstrated above. In the polarizing plate with double-sided protective film according to the present invention, the moisture content of the iodine-based polarizer 5 is less than 8% by weight, and since protective films with low moisture permeability are laminated on both surfaces, the thickness of the iodine-based polarizer 5 is small. Even if it is a case (for example, 10 micrometers or less in thickness), it becomes a thing which combines heat-and-moisture resistance and heat resistance. A polarizing plate with a double-sided protective film is applicable suitably to image display apparatuses like a liquid crystal display device and an organic electroluminescent device. In the case of application to a liquid crystal display device, the polarizing plate with double-sided protective film according to the present invention may be a polarizing plate disposed on the front (viewer) side of the liquid crystal cell, or a polarizing plate disposed on the back (backlight) side of the liquid crystal cell. .

A polarizing plate with a double-sided protective film is laminated|stacked on the 1st protective film 10 or the 2nd protective film 20, The adhesive layer for bonding to another member (for example, liquid crystal cell in the case of applying to a liquid crystal display device) may be provided. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is usually made of a (meth)acrylic resin, a styrene-based resin, a silicone-based resin, etc. as a base polymer, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. . 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.

Further, the polarizing plate with double-sided protective film may further include another optical layer laminated on the first protective film 10 or the second protective film 20 . Examples of the other optical layer include a reflective polarizing film that transmits a certain kind of polarized light and reflects the polarized light exhibiting the opposite property; A film with an anti-glare function having an uneven shape on the surface; Film with surface anti-reflection function; a reflective film having a reflective function on the surface; a transflective film having both a reflective function and a transmissive function; A viewing angle compensation film etc. are mentioned.

Example

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

<Example 1>

(1) Primer layer forming process

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Kosei Chemicals Co., Ltd., average degree of polymerization 1100, saponification degree 99.5 mol%) is dissolved in hot water at 95°C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3 wt% did. A crosslinking agent (“Sumirez Resin 650” manufactured by Taoka Chemical Co., Ltd.) was mixed with the obtained aqueous solution in a ratio of 5 parts by weight with respect to 6 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, corona treatment is performed on one side of a base film of 90 μm in thickness made of polypropylene (melting point: 163° C., moisture permeability: 15 g/m 2 /24 hr), and then using a small-diameter gravure coater on the corona-treated surface The coating solution for forming the primer layer was coated and dried at 80° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(2) Preparation of laminated film (resin layer formation process)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%, This was used as the coating liquid for polyvinyl alcohol-type resin layer formation.

After coating the coating solution for forming a polyvinyl alcohol-based resin layer on the surface of the primer layer of the base film having the primer layer prepared in (1) using a die coater, by drying at 80° C. for 20 minutes, on the primer layer The polyvinyl alcohol-type resin layer was formed, and the laminated|multilayer film which consists of a base film/primer layer/polyvinyl alcohol-type resin layer was obtained.

(3) Preparation of stretched film (stretching process)

With respect to the laminated|multilayer film produced in said (2), 5.3 times free-end uniaxial stretching was performed at 160 degreeC using the longitudinal uniaxial stretching apparatus of a floating, and the stretched film was obtained. The thickness of the polyvinyl alcohol-type resin layer after extending|stretching was 5.1 micrometers.

(4) Preparation of light-polarizing laminated film (dyeing process)

The stretched film prepared in (3) was immersed for about 180 seconds in an aqueous dyeing solution at 30° C. containing iodine and potassium iodide (0.6 parts by weight of iodine per 100 parts by weight of water, and 10 parts by weight of potassium iodide) for about 180 seconds. After performing the dyeing|staining process of the vinyl alcohol-type resin layer, 10 degreeC pure water wash|cleaned the excess dyeing solution.

Next, it is immersed in a first aqueous crosslinking solution at 78°C containing boric acid (10.4 parts by weight of boric acid per 100 parts by weight of water is included) for 120 seconds, followed by a second aqueous crosslinking solution at 70°C containing boric acid and potassium iodide. A crosslinking treatment was performed by immersing in (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. Then, it wash|cleaned for 10 second with 10 degreeC pure water. Finally, the light-polarizing laminated film which consists of a base film / iodine type polarizer was obtained by drying at 50 degreeC for 60 second and then at 80 degreeC for 60 second (moisture content reduction process). The moisture content of the iodine-type polarizer which the light-polarizing laminated film has at the time of completion|finish of drying was 0.4 weight%. In addition, the thickness of the iodine-based polarizer was 5.6 µm.

Moisture-proof film with re-peelability and low moisture permeability on the surface on the opposite side to the base film in the iodine-based polarizer so that moisture in the air can be absorbed and the moisture content of the iodine-based polarizer can be suppressed from rising (30 g of moisture permeability) /m 2 /24 hr polyolefin-based resin film) was immediately bonded after drying. Thereby, since the iodine-type polarizer is pinched|interposed by the base film of a low moisture permeability, and a moisture-proof film, a low moisture content can be maintained.

(5) Preparation of multilayer film (bonding process)

Immediately (within 1 minute), the 1st protective film was bonded together on the peeling surface, peeling a moisture-proof film from the light-polarizing laminated film with a moisture-proof film produced in said (4). For the first protective film, a thermoplastic resin film ("ZF-14" manufactured by Nippon Zeon Co., Ltd.) having a water vapor transmission rate of 16 g/m 2 /24 hr and having a thickness of 23 µm made of a cyclic polyolefin-based resin was used. The bonding of the first protective film is performed using a small-diameter gravure coater so that the thickness after curing is about 1.0 μm with an ultraviolet curable adhesive (“KR-75T” manufactured by ADEKA Co., Ltd.) on one side, and then this, It was performed by bonding to the said peeling surface using a bonding roll, and hardening the adhesive bond layer by irradiating ultraviolet-ray with the accumulated light amount of 200 mJ/cm<2> from the base film side using a high pressure mercury lamp after that.

(6) Production of polarizing plate with double-sided protective film (peeling process and polarizing plate with double-sided protective film production process)

Immediately after peeling the base film from the multilayer film produced in (5) above, a second protective film is bonded to the peeling surface thereof, and a first protective film/adhesive layer/iodine polarizer/adhesive layer/second protective film is formed. A polarizing plate with a double-sided protective film was obtained. For the second protective film, a thermoplastic resin film having a water vapor transmission rate of 16 g/m 2 /24 hr and a thickness of 23 µm made of a cyclic polyolefin resin (“ZF-14” manufactured by Nippon Zeon Co., Ltd.) was used. The bonding of the second protective film is performed on one side of the UV curable adhesive (“KR-75T” manufactured by ADEKA Co., Ltd.) using a small-diameter gravure coater so that the thickness after curing is about 1.0 μm, and then, It was performed by bonding to the said peeling surface using a bonding roll, and irradiating ultraviolet-ray with the accumulated light amount of 200 mJ/cm<2> from the 2nd protective film side using a high pressure mercury lamp after that, and hardening the adhesive bond layer. The moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film was 0.5 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 conditions of the final drying treatment (moisture content reduction step) of the dyeing step were set at 50° C. for 60 seconds and then at 65° C. for 60 seconds. The moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film was 4.6 weight%.

<Example 3>

It carried out similarly to Example 2, and produced the polarizing plate with a double-sided protective film. The moisture content of the iodine-based polarizer at the time of bonding the second protective film was 4.4% by weight, the visibility corrected polarization degree (Py) of the polarizing plate with double-sided protective film was 99.995%, and the visibility corrected single transmittance (Ty) was 40.9%.

<Example 4>

As the first protective film and the second protective film, a UV curable adhesive (“KR-” manufactured by ADEKA Co., Ltd. 15P"), it carried out similarly to Example 2, and produced the polarizing plate with a double-sided protective film. The moisture content of the iodine-based polarizer at the time of bonding the second protective film was 4.2% by weight, the visibility corrected polarization degree (Py) of the polarizing plate with double-sided protective film was 99.994%, and the visibility corrected single transmittance (Ty) was 41.4%.

<Example 5>

As the first protective film, a thermoplastic resin film having a moisture permeability of 63 g/m 2 /24 hr and made of an acrylic resin and having a thickness of 80 μm, as a second protective film, a water vapor transmission rate of 16 g/m 2 /24 hr, is a cyclic polyolefin-based A 23-micrometer-thick thermoplastic resin film made of 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 an ultraviolet curable adhesive (“KR-75T” manufactured by ADEKA Corporation). Except that, it carried out similarly to Example 2, and produced the polarizing plate with a double-sided protective film. The moisture content of the iodine-based polarizer at the time of bonding the second protective film was 4.8 wt%, the visibility corrected polarization degree (Py) of the polarizing plate with double-sided protective film was 99.994%, and the visibility corrected single transmittance (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 conditions of the drying treatment (moisture content reduction step) at the end of the dyeing step were set at 40°C for 60 seconds and then at 50°C for 60 seconds. The moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film was 10.7 weight%.

<Comparative Example 2>

Except having made the conditions of the drying process (moisture content reduction process) of the dyeing process last at 40 degreeC for 120 second, it carried out similarly to Example 1, and produced the polarizing plate with double-sided protective film. The moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film was 12.5 weight%.

<Comparative Example 3>

After the drying treatment (moisture content reduction process) at the end of the dyeing process, without bonding the moisture-proof film, it is stored for about 2 days under an environment of 25°C and 55% RH to increase the moisture content of the iodine-based polarizer to the vicinity of the equilibrium moisture content, and then Except having bonded the 1st and 2nd protective films, it carried out similarly to Example 2, and produced the polarizing plate with a double-sided protective film. The moisture content of the iodine-type polarizer at the time of bonding a 2nd protective film was 15.3 weight%.

The water vapor transmission rate of the film in each Example and the comparative example, and the moisture content of an iodine type polarizer were measured by the following method.

(1) moisture permeability

Based on JIS Z 0208-1976 "Test method for moisture permeability of moisture-proof packaging material (cup method)", the water vapor transmission rate at a temperature of 40 degreeC and 90% of a relative humidity was measured.

(2) Moisture content of iodine-based polarizer

A calibration curve representing the relationship between the moisture content measured by a near-infrared moisture meter ("IRMA1100S" manufactured by Chino Co., Ltd.) and the moisture content obtained according to the dry weight method, as a linear equation, is obtained for a plurality of iodine-based polarizer samples having different moisture content. The moisture content was obtained in advance from the moisture content, and the moisture content measured by a near-infrared moisture meter was converted into a moisture content according to the dry weight method using the above calibration curve, and this was taken as the moisture content of the iodine-based polarizer. In addition, the moisture content according to the dry weight method is determined by the following formula:

Moisture content (wt%) = 100 x (W0-W1)/W0

is defined as

[Evaluation of heat resistance and heat resistance of polarizing plate with double-sided protective film]

(1) Evaluation of heat-and-moisture resistance

For the polarizing plates with double-sided protection film produced in Examples 1 and 2 and Comparative Examples 1 to 3, the visibility corrected polarization degree (Py) and Py before the test after the heat-and-moisture resistance test left still for 500 hours in an environment of 65°C and 90% RH , was measured using a light absorption spectrometer ("V7100" manufactured by Nippon Bunko Co., Ltd.), and heat-and-moisture resistance was evaluated from the difference (ΔPy) (Py before test - Py after test). The smaller the absolute value of ΔPy, the higher the heat-and-moisture resistance. A result is shown in Table 1. In the measurement of Py, the polarizing plate sample with a double-sided protective film was set so that incident light might be irradiated to the 2nd protective film side. In addition, the visibility correction|amendment polarization degree (Py) after a moist-and-heat resistance test was measured, after leaving still for about 12 hours in 23 degreeC 55%RH environment after a moist-and-heat resistance test.

Py before the heat-and-moisture resistance test (and the following heat resistance test) was 99.995 % in all about each Example and the comparative example. Moreover, the visibility correction|amendment single transmittance|permeability (Ty) measured using the copper absorption spectrometer was all 41.6 % about each Example and the comparative example.

(2) Evaluation of heat resistance

About the polarizing plate with double-sided protection film produced in Examples 1 and 2 and Comparative Examples 1-3, by performing the heat resistance test left still for 500 hours in the environment of 85 degreeC drying, it carried out similarly to the said evaluation of heat-and-moisture resistance, and ΔPy ( The heat resistance was evaluated from Py before the test - Py after the test). The smaller the absolute value of ΔPy, the higher the heat resistance. A result is shown in Table 1.

(3) Evaluation of heat-and-moisture resistance under accelerated conditions

About the polarizing plate with double-sided protective film produced in Examples 3-5, the heat-and-moisture resistance test left still in the environment of 80 degreeC and 90%RH for 48 hours was performed by the method similar to evaluation of said (1) heat-and-moisture resistance. A result is shown in Table 2.

(4) Evaluation of heat resistance under accelerated conditions

About the polarizing plate with double-sided protection film produced in Examples 3-5, the heat resistance test left still in 105 degreeC and a dry environment for 48 hours was done by the method similar to evaluation of said (2) heat resistance. A result is shown in Table 2.

In addition, about the polarizing plate with a double-sided protective film after a heat resistance test, the grade of light leakage (red discoloration) was confirmed visually. Specifically, two 10 cm x 20 cm sample pieces were cut out from the polarizing plate with double-sided protective film after the heat resistance test, and these samples were bonded together on both surfaces of a glass plate using an adhesive. At this time, it was made for the 2nd protective film side to become a glass plate side, and it was made for the sample piece arrange|positioned on both surfaces to become a cross nicol positional relationship. And the backlight was irradiated from the side of one polarizing plate in a dark room, and the visual evaluation of redness was performed according to the following evaluation criteria. A result is shown in Table 1 and Table 2.

A: It maintains a black state, and redness cannot be recognized by the naked eye.

B: A clear red flag is recognized.

5: iodine-based polarizer, 6: polyvinyl alcohol-based resin layer, 6': stretched polyvinyl alcohol-based 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)

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-sided protective film;
The process of bonding a 2nd protective film to the outer surface of the iodine type polarizer in the said polarizing plate with a single-sided protective film, and obtaining a polarizing plate with a double-sided protective film
including,
The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m 2 /24 hr or less,
The moisture content of the said iodine-type polarizer at the time of bonding the said 2nd protective film is 4.8 weight% or less,
Exposure of the iodine-based polarizer in the polarizing plate with a single-sided protective film so that the moisture content does not exceed 4.8 wt% between the step of obtaining the polarizing plate with single-sided protective film and the step of obtaining the polarizing plate with double-sided protective film The manufacturing method of the polarizing plate with a double-sided protective film which temporarily bonds a peelable moisture-proof film to a surface. According to claim 1, wherein the moisture content of the iodine-based polarizer at the time of bonding the second protective film is 4.2% by weight or less,
Exposure of the iodine-based polarizer in the polarizing plate with a single-sided protective film so that the moisture content does not exceed 4.2 wt% between the step of obtaining the polarizing plate with single-sided protective film and the step of obtaining the polarizing plate with double-sided protective film A manufacturing method of temporarily bonding a peelable moisture-proof film to a surface. The manufacturing method according to claim 1 or 2, wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive. The method according to claim 1 or 2, wherein the iodine-based polarizer has a thickness of 10 µm or less. In a polarizing plate with a single-sided protective film comprising an iodine-based polarizer and a first protective film laminated on one side thereof, a second protective film is bonded to the outer surface of the iodine-based polarizer to obtain a polarizing plate with double-sided protective film;
The first protective film and the second protective film are thermoplastic resin films having a moisture permeability of 150 g/m 2 /24 hr or less,
The moisture content of the said iodine-type polarizer at the time of bonding the said 2nd protective film is 4.8 weight% or less,
After obtaining the said polarizing plate with a single-sided protective film, between the process of obtaining the said polarizing plate with a double-sided protective film, so that the said moisture content may not exceed 4.8 weight%, the exposed surface of the iodine-type polarizer in the said polarizing plate with a single-sided protective film The manufacturing method of the polarizing plate with a double-sided protective film which temporarily bonds the moisture-proof film which can be peeled to. The manufacturing method according to claim 5, wherein the second protective film is bonded to the outer surface of the iodine-based polarizer using an active energy ray-curable adhesive. The method according to claim 5 or 6, wherein the iodine-based polarizer has a thickness of 10 µm or less. delete

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