CN103201656A - Methods for producing polarizing laminate film and polarizing plate - Google Patents

Abstract

A method for producing a polarizing laminated film, which is a method for producing a polarizing laminated film having a base film and a polarizer layer formed on one surface of the base film, the method comprising sequentially: A resin film laminating process of laminating a resin film containing a polyvinyl alcohol-based resin with a thickness of 50 μm or less to obtain a laminated film; a stretching process of uniaxially stretching the laminated film; and using a dichroic dye A dyeing step of dyeing the resin film of the uniaxially stretched laminated film to form a polarizer layer. According to the present invention, it is possible to provide a method for producing a polarizing laminated film having a thin polarizer layer without causing a problem that the edge of the base film is bent.

Description

Polarizing laminated film and method for producing polarizing plate

technical field

The present invention relates to a method for manufacturing a polarizing laminated film and a polarizing plate.

Background technique

A polarizing plate is widely used as a polarized light supply element and the like in display devices such as liquid crystal display devices. As the polarizing plate, a polarizing plate in which a polarizer layer made of a polyvinyl alcohol-based resin and a protective film such as triacetyl cellulose are laminated has been conventionally used. The polarizer layer (polarizing film) is not only required to have high optical performance, but also has been required to be thinner and lighter in recent years with the development of liquid crystal display devices in mobile devices such as notebook PCs and mobile phones.

As an example of a method for producing a polarizing plate, a method is known in which a polarizing film is produced by stretching a film made of a polyvinyl alcohol-based resin alone, or performing dyeing treatment and crosslinking treatment while stretching, and A polarizing plate is manufactured by laminating this on a protective film etc. (for example, refer JPH11-49878-A).

As another example of the method for producing a polarizing plate, a method is proposed in which a solution containing a polyvinyl alcohol-based resin is coated on the surface of a base film, and after the resin layer is provided, the base film and the resin layer are stretched. A method for obtaining a polarizing laminated film having a polarizing layer by dyeing the laminated film, forming a polarizer layer from a resin layer (for example, refer to JP2000-33829-A). A method is disclosed in which it is used as a polarizing plate as it is, or a product obtained by peeling off a base film after bonding the film to a protective film is disclosed.

As another example of the method for producing a polarizing plate, a resin for a protective film and a polyvinyl alcohol-based resin are co-extruded to produce a laminated film, the laminated film is stretched, and then dyed to obtain a polarizer layer and a polarizer layer. A method of protecting a polarizing plate made of a film (for example, refer to JP2009-25821-A).

However, in the method of manufacturing a polarizing film by stretching, dyeing, and crosslinking a film made of polyvinyl alcohol-based resin alone, it is difficult to handle a thin film of 50 μm or less because it is prone to breakage, wrinkles, etc. Therefore, it is difficult to reduce the thickness of the polarizing film.

In the method of applying a solution containing a polyvinyl alcohol-based resin on the surface of a base film to form a resin layer, the resin layer tends to shrink due to the drying shrinkage of the solution containing a polyvinyl alcohol-based resin, and as a result, bases sometimes occur. The phenomenon that both ends of the material film are warped toward the resin layer side, if the base film with the resin layer is kept flowing continuously in this state, it will cause the end of the base film to bend in the drying furnace or at the outlet of the drying furnace. Bad condition.

In the method of producing a laminated film by co-extruding a protective film resin and a polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin is usually melted together with a solvent and extruded. A defect that causes the edge of the base film to bend.

Therefore, an object of the present invention is to provide a method for producing a polarizing laminated film and a polarizing plate having a thin polarizer layer without causing a problem that the edge of the base film is bent.

Contents of the invention

The present invention includes the following aspects.

[1] A method for producing a polarizing laminated film having a substrate film and a polarizer layer formed on one surface of the substrate film, the method comprising the following steps in sequence: A resin film laminating process of laminating a resin film containing a polyvinyl alcohol-based resin with a thickness of 50 μm or less on one surface of the film to obtain a laminated film;

A stretching step of uniaxially stretching the laminated film; and

A dyeing step of dyeing the resin film of the uniaxially stretched laminated film with a dichroic dye to form a polarizer layer.

[2] The method according to [1], wherein, in the resin film bonding step, the resin film is bonded to the One side of the substrate film.

[3] The method according to [1] or [2], wherein in the resin film bonding step, the resin film has a thickness of 15 μm or more.

[4] The method according to any one of [1] to [3], wherein the resin film used in the resin film bonding step is a resin film produced by a production method sequentially including the following steps,

A resin layer forming step of forming a resin layer containing a polyvinyl alcohol-based resin on the support,

A first drying step of drying the resin layer, a resin layer separation step of peeling the resin layer from the support to obtain the resin layer, and

A second drying step of drying the resin layer at a drying temperature higher than that in the first drying step.

[5] A method of manufacturing a polarizing plate having a polarizer layer and a protective film formed on one surface of the polarizer layer, wherein the method of manufacturing polarizers by the method described in [1] After laminating the film, the following steps are included in sequence:

A protective film bonding step of bonding a protective film to a surface of the polarizer layer opposite to the surface of the base film in the polarizing laminate film; and

A base film peeling process of peeling the said base film from this polarizing laminated film.

According to the present invention, it is possible to manufacture a polarizing laminated film and a polarizing plate having a thin polarizer layer without bending the edge of the base film in the production process.

Description of drawings

FIG. 1 is a flowchart showing an embodiment of a method for producing a polarizing laminated film of the present invention.

FIG. 2 is a flow chart showing an embodiment of a method of manufacturing a polarizing plate of the present invention.

FIG. 3 is a flowchart showing one embodiment of a method for producing a polyvinyl alcohol-based resin film.

Detailed ways

Hereinafter, preferred embodiments of the method for producing a polarizing laminated film and the method for producing a polarizing plate according to the present invention will be described in detail with reference to the drawings.

[Manufacturing method of polarizing laminated film]

FIG. 1 is a flowchart showing an embodiment of a method for producing a polarizing laminated film according to the present invention. The polarizing laminated film produced in this embodiment has a base film and a polarizer layer formed on one surface of the base film. In the method for producing a polarizing laminated film according to the present embodiment, the resin film bonding step (S10) of bonding a resin film containing a polyvinyl alcohol-based resin to one surface of a base film to obtain a laminated film is usually carried out in sequence (S10). A stretching step (S20) of uniaxially stretching the laminated film, and a dyeing step (S30) of dyeing the resin film of the laminated film with a dichroic dye to form a polarizer layer.

In this specification, a laminate having a resin film containing a polyvinyl alcohol-based resin (hereinafter also referred to as a "polyvinyl alcohol-based resin film") bonded to one surface of a base film is referred to as a "laminated film". The polyvinyl alcohol-type resin film which functions as a polarizer is called a "polarizer layer", and the laminate which has a polarizer layer on one surface of a base film is called a "polarizing laminated film." Moreover, the laminated body which has a protective film on one surface of a polarizing plate layer is called "polarizing plate".

According to the production method described above, a polarizing laminated film having a polarizer layer having sufficient polarizing performance, eg, a thickness of 25 μm or less, on a base film can be obtained. The thickness of the polarizer layer of the polarizing laminated film obtained by the above production method is preferably 25 μm or less, more preferably 20 μm or less. As will be described later, this polarizing laminated film can also be used as an intermediate product for transferring the polarizer layer to the protective film. In addition, when the base film has the function of the protective film, the polarizing layer can also be used The polarized laminated film is directly used as a polarizing plate.

[Manufacturing method of polarizing plate]

FIG. 2 is a flow chart showing one embodiment of the method of manufacturing a polarizing plate according to the present invention. The polarizing plate produced by this embodiment has a polarizing layer and a protective film formed on one surface of the polarizing layer. Regarding the manufacturing method of the polarizing plate of the present embodiment, the following steps are generally carried out sequentially: the resin film bonding step (S10) of bonding a polyvinyl alcohol-based resin film to one surface of the base film to obtain a laminated film; The stretching step (S20) of uniaxially stretching the laminated film, and the dyeing step (S30) of dyeing the polyvinyl alcohol-based resin film of the laminated film with a dichroic dye to form a polarizer layer, thereby obtaining polarizing properties. After the film is laminated, there are usually a protective film bonding step (S40) of laminating a protective film on the surface of the polarizer layer of the polarizing laminated film opposite to the surface of the base film (S40), and peeling the substrate from the polarizing laminated film. The substrate film peeling process (S50) of a material film.

A polarizing plate having a polarizer layer having sufficient polarizing performance, for example, a thickness of 25 μm or less on a protective film can be obtained by the above-mentioned production method. The thickness of the polarizer layer of the polarizing plate obtained by the above production method is preferably 25 μm or less, more preferably 20 μm or less. This polarizing plate can be used, for example, to be bonded to other optical films, liquid crystal cells, and the like via a pressure-sensitive adhesive.

Each step of S10 to S50 in FIG. 1 and FIG. 2 will be described in detail below. In addition, each process of S10-S30 of FIG. 1 and FIG. 2 is the same process.

<Resin film bonding process (S10)>

A polyvinyl alcohol-based resin film is bonded to one surface of the base film. The bonding method of the base film and the polyvinyl alcohol-based resin film is not particularly limited as long as it does not peel off even through the subsequent stretching step ( S20 ) and dyeing step ( S30 ). For example, an adhesive layer or an adhesive layer is formed on the bonding surface of a polyvinyl-alcohol-type resin film and/or a base film, and both are bonded via an adhesive layer or an adhesive layer.

(polyvinyl alcohol-based resin film)

The thickness of the polyvinyl alcohol-type resin film used in a resin film bonding process shall be 50 micrometers or less. Although the polyvinyl alcohol-based resin film can form a polarizer layer through the subsequent stretching process and dyeing process, the polyvinyl alcohol-based resin film in the resin film bonding process (S10), that is, the polyvinyl alcohol-based resin before stretching When the thickness of the film exceeds 50 μm, the operations of the stretching step and the dyeing step can be performed even if it is not bonded to the base film as described in the present invention, so the advantages of the present invention are few. Moreover, when the thickness of a polyvinyl-alcohol-type resin film exceeds 50 micrometers, it may become difficult to form a film whose thickness of a polarizer layer is 25 micrometers or less. Furthermore, the thickness of the polyvinyl alcohol-based resin film (before stretching) is preferably 10 μm or more, more preferably 15 μm or more. When the thickness of a polyvinyl-alcohol-type resin film is less than 10 micrometers, it is difficult to obtain a polyvinyl-alcohol-type resin film independently. The thickness of the polyvinyl alcohol-based resin film is more preferably 15 to 45 μm.

As a polyvinyl-alcohol-type resin which forms a polyvinyl-alcohol-type resin film, what saponified polyvinyl acetate-type resin can be used. Examples of the polyvinyl acetate-based resin include copolymers with other monomers copolymerizable with vinyl acetate other than polyvinyl acetate that is a homopolymer of vinyl acetate. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The polyvinyl alcohol-based resin is preferably a completely saponified product. The range of the degree of saponification is preferably 80 mol % to 100 mol %, more preferably 90 mol % to 100 mol %, and most preferably 94 mol % to 100 mol %. When the degree of saponification is less than 80 mol%, water resistance and heat-and-moisture resistance after forming a polarizing plate layer may deteriorate remarkably.

The degree of saponification referred to here refers to a value representing the ratio of acetic acid groups contained in polyvinyl acetate-based resins, which are raw materials for polyvinyl alcohol-based resins, into hydroxyl groups by a saponification step, in terms of unit ratios (mol %), and is The numerical value defined by the following formula. It can be obtained by the method stipulated in JIS K6726 (1994).

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

The higher the degree of saponification, the higher the proportion of hydroxyl groups, that is, the lower the proportion of acetate groups that inhibit crystallization.

In addition, the polyvinyl alcohol-based resin may be partially modified modified polyvinyl alcohol. Examples thereof include polyvinyl alcohol-based 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, acrylamides, and the like. The ratio of modification is preferably less than 30 mol%, more preferably less than 10%. When the modification exceeds 30 mol %, it becomes difficult to adsorb the dichroic dye, and the problem of low polarization performance occurs.

The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, either, but is preferably 100 to 10,000, more preferably 1,500 to 8,000, and even more preferably 2,000 to 5,000. The average degree of polymerization referred to here is also a value obtained by the method specified in JIS K6726 (1994).

As a polyvinyl alcohol-based resin having such characteristics, for example, PVA124 (saponification degree: 98.0 to 99.0 mol %), PVA117 (saponification degree: 98.0 to 99.0 mol %), PVA624 (saponification degree: 95.0～96.0 mole %) and PVA617 (saponification degree: 94.5～95.5 mole %); For example, AH-26 (saponification degree: 97.0～98.8 mole %), AH-22 (saponification degree: 97.5～98.5 mole %), NH-18 (saponification degree: 98.0～99.0 mole %), and N-300 (saponification degree: 98.0～99.0 mole %); such as JAPAN VAM&OVAL CO.LTD (strain) JC-33 ( Saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5-95.5 mol%), JM-26 (saponification degree: 95.5-97.5 mol%), JP-45 (saponification degree: 86.5-89.5 mol%) , JF-17 (saponification degree: 98.0-99.0 mol%), JF-17L (saponification degree: 98.0-99.0 mol%), and, JF-20 (saponification degree: 98.0-99.0 mol%), etc. It is suitably used for formation of the polyvinyl-alcohol-type resin film of this invention.

A polyvinyl alcohol-based resin film is formed by forming a film of the above-mentioned polyvinyl alcohol-based resin. It does not specifically limit as a film-forming method of a polyvinyl-alcohol-type resin film. Examples include a solvent casting method in which a polyvinyl alcohol-based resin solution is coated on a support and dried; or a melt extrusion method in which a polyvinyl alcohol-based resin containing water is melt-kneaded and extruded onto a support with an extruder. Furthermore, a gel film-forming method in which an aqueous solution of polyvinyl alcohol-based resin is sprayed into a poor solvent (low solubility solvent), etc. Among them, the casting method or the melt extrusion method is preferable because a more transparent film is obtained.

Preferred embodiment of the manufacturing method of a polyvinyl-alcohol-type resin film is demonstrated below. FIG. 3 shows a flowchart of a method for producing a polyvinyl alcohol-based resin film according to the present embodiment. In this embodiment, the resin layer forming step (S110) of forming a resin layer containing a polyvinyl alcohol-based resin on a support body (S110), the first drying step (S120) of drying the resin layer, A resin layer separating step (S130) of peeling the resin layer to obtain the resin layer, and a second drying step (S140) of drying the resin layer at a temperature higher than that of the first drying step.

Examples of the support mentioned here include a release film, a stainless steel belt, and a chilled roll. As a method of forming a resin layer on a support body in a resin layer forming process (S110), the above-mentioned solvent casting method and melt extrusion method can be illustrated. For example, it is preferable to apply a polyvinyl alcohol-based resin solution obtained by dissolving the powder of a polyvinyl alcohol-based resin in a good solvent (highly soluble solvent) on one surface of the support, and to form a solvent cast by evaporating and drying the solvent. Law. By forming the polyvinyl alcohol-based resin layer in this way, a polyvinyl alcohol-based resin layer having a thickness of 10 to 50 μm can be formed.

As a method for coating the polyvinyl alcohol-based resin solution on the support, roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, and comma coating can be appropriately selected. , lip coating method, spin coating method, screen coating method, fountain coating method (fountain coating method), dipping method, spraying method and other known methods.

The polyvinyl alcohol-based resin solution used in these methods can be obtained by dissolving a polyvinyl alcohol-based resin in water heated up to 80-90 degreeC, for example.

The solid content concentration of the polyvinyl alcohol-based resin is preferably in the range of 6 wt % to 50 wt %. When the solid content concentration is less than 6 wt%, the viscosity becomes too low, the fluidity at the time of forming the resin layer becomes too high, and it becomes difficult to obtain a uniform film. On the other hand, when the concentration of the solid content exceeds 50 wt%, the viscosity becomes too high, and the fluidity at the time of forming the resin layer becomes too low, making it difficult to form a film.

A plasticizer may be added to the polyvinyl alcohol-based resin solution. Among them, polyols are preferably used, and examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane. Multiple combinations are also possible. Ethylene glycol and glycerin are particularly preferably used. Moreover, antiblocking agents, such as a surfactant, etc. can also be used together as needed.

After the resin layer forming step (S110), in the first drying step (S120), dry at a low temperature, usually at a drying temperature of 60° C. or lower, until the resin layer formed on the support can be peeled off from the support. Degree. The extent to which the coating liquid can be peeled from the support means a state in which the coating liquid is solid to some extent and can be peeled off as a film. Generally, the entire film can be peeled off stably as long as it is dried to a moisture content of 30 wt % or less. If it dries to 20 wt% or less, it can be peeled off more easily, so it is preferable. The moisture content mentioned here means the moisture content calculated|required by the dry weight method, and can be calculated|required by the following method.

- After leaving the peeled PVA film at normal temperature (approximately 25° C. 55% RH) for 30 minutes or more, the film weight was measured.

• Then, after drying at 105° C. for 60 minutes, it was taken out, and then left to stand for several minutes until the film temperature returned to normal temperature.

• After standing for several minutes, re-measure the weight of the film.

- The obtained value was substituted into the following formula.

Moisture rate = (weight before drying - weight after drying) / weight before drying × 100 (wt/wt%)

As a specific way of drying it to the extent that the resin layer formed on the support can be peeled from the support, for example, it is preferable to study the drying conditions in advance in a preliminary experiment to achieve a state where the peel can be achieved in actual production, and under these conditions. For example, it is preferable to dry at a temperature range of 40° C. to 60° C. for 1 to 30 minutes, more preferably at 50° C. for about 3 to 20 minutes.

In the 1st drying process (S120), by drying at a low temperature, and by drying to the extent that the resin layer can be peeled from the support without being completely dried, drying shrinkage in the resin layer is difficult to occur, and it is possible to prevent the resin layer from drying. The ends are curled.

Next, in the resin layer separation step ( S130 ), the resin layer dried in the first drying step is peeled from the support to obtain a resin layer. Moreover, in the 2nd drying process (S140), the resin layer peeled from a support body is dried. In the second drying step (S140), the resin layer is sufficiently dried. Therefore, it is made to dry at the drying temperature of high temperature compared with a 1st drying process. The high temperature mentioned here is usually below 150°C, preferably below 120°C, more preferably below 100°C, preferably above 60°C, more preferably above 70°C. As the drying method, there are various methods such as a method of blowing hot air, a method of contacting with a heat roller, and a method of heating with an IR heater, but any of them can be used appropriately. In addition, the drying temperature mentioned in the 1st drying process and the 2nd drying process refers to the atmospheric temperature in a drying furnace in the case of the method of blowing hot air or the drying equipment which installs a drying furnace, such as an IR heater. , in the case of a contact type drying device such as a heat roll, refers to the surface temperature of the heat roll. Through the above steps, a polyvinyl alcohol-based resin film is manufactured.

The polyvinyl-alcohol-type resin film produced by the method of this embodiment becomes a favorable film in which curling was suppressed.

(substrate film)

As the resin used for the base film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, stretchability, etc. can be used, and appropriate resins can be selected according to their glass transition temperature Tg or melting point Tm. As the base film, it is preferable to use a base film that can be stretched in a temperature range suitable for stretching the polyvinyl alcohol-based resin film laminated thereon.

Specific examples of thermoplastic resins include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth)acrylic resins, cellulose ester resins, polycarbonate resins, and polyolefin resins. Resin, polyvinyl alcohol-based resin, vinyl acetate-based resin, polyarylate-based resin, polystyrene-based resin, polyethersulfone-based resin, polysulfone-based resin, polyamide-based resin, polyimide-based resin ; And their mixtures, copolymers, etc.

The base film may be a film composed of only one kind of the above-mentioned resins, or may be a film obtained by mixing two or more kinds of resins. The base film may be a single-layer film or a multi-layer film.

Examples of the polyolefin-based resin include polyethylene, polypropylene, and the like, and it is preferable to stretch it easily and stably at a high ratio. In addition, a propylene-ethylene copolymer obtained by copolymerizing ethylene and propylene may also be used. Other types of monomers may be used for copolymerization, and examples of other types of monomers that can be copolymerized with propylene include ethylene and α-olefins. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and an α-olefin having 4 to 10 carbon atoms is more preferably used. Specific examples of α-olefins having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene. ; 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene and other branched monoolefins; vinylcyclohexane, etc. The copolymer of propylene and other monomers that can be copolymerized therewith may be a random copolymer or a block copolymer. The content rate of the constituent unit derived from the other monomer in the copolymer can be determined based on the method described on page 616 of "Polymer Analysis Handbook (Polymer Analysis Handbook)" (1995, published by Kinokuniya Shoten) by It was determined by performing infrared (IR) spectrometry.

Among the above, as the propylene-based resin constituting the propylene-based resin film, it is preferable to use a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and a propylene-ethylene-1-butene random copolymer.

In addition, the stereoregularity of the propylene-based resin constituting the propylene-based resin film is substantially preferably isotactic or syndiotactic. A propylene-based resin film substantially composed of a propylene-based resin having isotactic or syndiotactic stereoregularity has relatively good handling properties and is excellent in mechanical strength in a high-temperature environment.

Polyester-based resins are polymers with ester bonds, mainly polycondensates of polycarboxylic acids and polyhydric alcohols. As the polyvalent carboxylic acid, dibasic dicarboxylic acids are mainly used, for example, isophthalic acid, terephthalic acid, dimethyl terephthalate, dimethyl naphthalene dicarboxylate, and the like. In addition, dihydric diols are also mainly used as polyols to be used, and examples thereof include propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Specific resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyterephthalic acid Propylene glycol ester, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexanedimethyl naphthalate, and the like. Mixed resins and copolymers thereof are also preferably used.

As the cyclic polyolefin-based resin, norbornene-based resin is preferably used. Cyclic polyolefin-based resins are a general term for resins polymerized using cyclic olefins as polymer units, and examples thereof include resins described in JPH01-240517-A, JPH03-14882-A, and JPH03-122137-A. Specific examples include ring-opening (co)polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers (typically random copolymers) of cyclic olefins and α-olefins such as ethylene and propylene. ); and graft polymers modified with unsaturated carboxylic acids or derivatives thereof; and their hydrides, etc. Specific examples of cyclic olefins include norbornene-based monomers.

Various products are commercially available as a cyclic polyolefin resin. Specific examples include Topas (registered trademark) (manufactured by Ticona Corporation), ARTON (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Japan ZEON Corporation), ZEONEX (registered trademark) ( Japan ZEON Co., Ltd.), APEL (registered trademark) (Mitsui Chemicals Co., Ltd.) and the like.

Any appropriate (meth)acrylic resin can be adopted as the (meth)acrylic resin. Examples thereof include poly(meth)acrylates such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylate copolymers, methyl Methyl acrylate-acrylate-(meth)acrylic acid copolymer, (meth)methyl acrylate-styrene copolymer (MS resin, etc.), polymers with alicyclic hydrocarbon groups (such as methyl methacrylate- cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.), and the like.

Preferably, poly (meth)acrylate C1-6 alkyl esters, such as polymethyl (meth)acrylate, are mentioned. As the (meth)acrylic resin, it is more preferable to use a methyl methacrylate resin in which methyl methacrylate is a main component (50 to 100% by weight, preferably 70 to 100% by weight).

Cellulose ester-based resins are esters of cellulose and fatty acids. Specific examples of cellulose ester-based resins include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like.

In addition, those obtained by modifying part of these copolymers or hydroxyl groups with other types of substituents and the like can also be mentioned. Among them, cellulose triacetate is particularly preferable. Cellulose triacetate is commercially available in various products, and it is also advantageous in terms of ease of acquisition and cost. Examples of commercially available cellulose triacetate include FUJITAC (registered trademark) TD80 (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark ) TD80UZ (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD40UZ (manufactured by Fujifilm Co., Ltd.), KC8UX2M (manufactured by KONICA MINOLTA OPTO Co., Ltd.), KC4UY (manufactured by KONICA MINOLTA OPTO Co., Ltd.), etc.

Polycarbonate-based resins are engineering plastics composed of polymers in which monomer units are bonded via carbonate groups, and are resins having high impact resistance, heat resistance, and flame retardancy. Moreover, since it has high transparency, it can also be used suitably for an optical use. Resins called modified polycarbonates in which the polymer backbone is modified to lower the photoelastic coefficient, copolycarbonates with improved wavelength reliability, and the like are also commercially available, and are suitable for optical applications. Such polycarbonate resins are widely commercially available, for example, Panlite (registered trademark) (Teijin Chemical Co., Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering Plastics Co., Ltd.), SD POLYCA (registered trademark) (Sumitomo Ceramics Co., Ltd.) Co., Ltd.), CALIBER (registered trademark) (Dow Chemical Co., Ltd.), etc.

In addition to the above-mentioned thermoplastic resin, arbitrary appropriate additives may be added to a base film. Such additives include, for example, ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants and the like. The content of the thermoplastic resins exemplified above in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight. The reason is that when the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency originally possessed by the thermoplastic resin may not be sufficiently expressed.

The thickness of the base film before stretching can be appropriately determined, but usually from the viewpoint of handling properties such as strength and handleability, it is preferably 1 to 500 μm, more preferably 1 to 300 μm, still more preferably 5 to 200 μm, and particularly preferably 5 to 200 μm. 5~150μm.

About a base film, in order to improve the adhesiveness with a polyvinyl-alcohol-type resin film, you may corona-treat, plasma-treat, flame-treat, etc. the surface on the side to which a polyvinyl-alcohol-type resin film is bonded at least. Moreover, in order to improve adhesiveness, you may form thin layers, such as a primer layer, on the surface of the side where the polyvinyl-alcohol-type resin film was formed in the base film.

(base coat)

A primer layer may be formed on the surface of the base film on which the polyvinyl alcohol-based resin film is bonded. The undercoat layer will not be particularly limited as long as it is a material that exhibits somewhat strong adhesive force in both the base film and the polyvinyl alcohol-based resin film. Thermoplastic resins excellent in, for example, transparency, thermal stability, stretchability, and the like can be used. Specifically, acrylic resins and polyvinyl alcohol-based resins may be mentioned, but not limited thereto. Among them, it is preferable to use a polyvinyl alcohol-based resin having good adhesiveness.

As a polyvinyl-alcohol-type resin used as an undercoat layer, polyvinyl-alcohol resin and its derivative(s) are mentioned, for example. As derivatives of polyvinyl alcohol resin, in addition to polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; Alkyl esters of saturated carboxylic acids; substances obtained by modifying polyvinyl alcohol resins such as acrylic amides. Among the above-mentioned polyvinyl alcohol-based resin materials, polyvinyl alcohol resins are preferably used.

In order to increase the strength of the undercoat layer, a crosslinking agent may also be added to the aforementioned thermoplastic resin. As the crosslinking agent added to the thermoplastic resin, known crosslinking agents such as organic and inorganic ones can be used. For the thermoplastic resin to be used, it is only necessary to properly select a more suitable crosslinking agent. For example, in addition to low-molecular cross-linking agents such as epoxy-based cross-linking agents, isocyanate-based cross-linking agents, dialdehyde-based cross-linking agents, and metal chelate-based cross-linking agents, methylolated honey can also be used. Amine resins, polyamide epoxy resins and other high-molecular cross-linking agents. When a polyvinyl alcohol-based resin is used as the thermoplastic resin, it is particularly preferable to use a polyamide epoxy resin, methylolated melamine, dialdehyde, a metal chelate crosslinking agent, or the like as the crosslinking agent.

The thickness of the undercoat layer is preferably 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When it is thinner than 0.05 micrometer, the adhesive force of a base film and a polyvinyl alcohol film will fall, and when it is thicker than 1 micrometer, since a polarizing plate will become thick, it is unpreferable.

(adhesive layer)

The adhesive constituting the adhesive layer is called a pressure-sensitive adhesive, and generally contains acrylic resin, styrene resin, silicone resin, etc. as the base polymer, and isocyanate compound, epoxy compound, etc. , aziridine compounds and other cross-linking agents. Furthermore, fine particles may be blended into the adhesive to form a light-scattering adhesive layer.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm, and is preferably applied thinly within a range that does not impair processability and durability, more preferably 3 to 25 μm. If it is 3-25 micrometers, it will have favorable processability, and it is also suitable thickness for controlling the dimensional change of a polarizing film. When the pressure-sensitive adhesive layer is less than 1 μm, the adhesiveness decreases, and when it exceeds 40 μm, problems such as pressure-sensitive adhesive overflow are likely to occur.

The method of forming the adhesive layer on the base film or the polyvinyl alcohol resin film is not particularly limited, and the surface of the base film or the surface of the polyvinyl alcohol resin film may be coated with a After the solution of each component is dried to form an adhesive layer, it is attached to a spacer or other types of film; it can also be attached to the substrate film surface or polyvinyl alcohol after forming an adhesive layer on the spacer. The resin film surface is laminated. In addition, when the adhesive layer is formed on the substrate film or the polyvinyl alcohol-based resin film surface, one or both of the substrate film surface, the polyvinyl alcohol-based resin film surface, or the adhesive layer may be Those who carry out close treatment, such as corona treatment and so on.

(adhesive layer)

Examples of the adhesive constituting the adhesive layer include water-based adhesives using a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based latex adhesive, and the like. Among them, it is preferable to use an aqueous solution of polyvinyl alcohol-based resin. As for the polyvinyl alcohol-based resin used as an adhesive, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, there are also vinyl acetate and Vinyl alcohol-based copolymers obtained by saponification of copolymers of other monomers copolymerized with them, modified polyvinyl alcohol-based polymers obtained by partially modifying the hydroxyl groups of the above substances, and the like. Polyhydric aldehydes, water-soluble epoxy compounds, melamine compounds, zirconium dioxide compounds, zinc compounds, etc. may also be added as additives to the water-based adhesive. When such a water-based adhesive is used, the adhesive layer obtained therefrom is usually much thinner than 1 μm, and the adhesive layer is virtually invisible even when the cross-section is observed with a normal optical microscope.

The method of laminating the film using the water-based adhesive is not particularly limited, and examples include uniformly coating or pouring the adhesive on the surface of a base film or a polyvinyl alcohol-based resin film, and overlapping another adhesive on the coated surface. The film is bonded with a roll or the like, a method of drying, and the like. Usually, after the adhesive is prepared, it is applied at a temperature of 15 to 40°C, and the bonding temperature is usually in the range of 15 to 30°C.

In the case of using a water-based adhesive, drying is performed to remove water contained in the water-based adhesive after laminating the film. The temperature of the drying furnace is preferably 30°C to 90°C. If it is less than 30°C, the adhesive surface tends to be easily peeled off. When it is 90 degreeC or more, the optical performance of a polarizing plate etc. may deteriorate by heat. The drying time can be set to 10 to 1000 seconds.

After drying, it can also be cultured at room temperature or a temperature slightly higher than room temperature, for example, at a temperature of about 20 to 45° C. for about 12 to 600 hours. The temperature during cultivation is usually set lower than that used during drying.

In addition, as the non-aqueous adhesive, a photocurable adhesive can also be used. As a photocurable adhesive agent, the mixture of a photocurable epoxy resin and a photocationic polymerization initiator, etc. are mentioned, for example.

As a method of laminating films with a photocurable adhesive, conventionally known methods can be used, and examples thereof include a casting method, a wire bar coating method, a gravure coating method, a comma coating method, and a doctor blade method. , Die coating method, dip coating method, spray method, etc., apply an adhesive to the bonding surface of the film, and overlap two films. The casting method is a method in which an adhesive is flowed onto the surface of two films to be coated and diffused while moving them in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between them.

After the adhesive is applied to the surface of the film, the film is sandwiched between nip rolls and the like to bond the film together. Moreover, the method of pressurizing this laminated body with a roll etc. and spreading it uniformly can also be used preferably. In this case, metal, rubber, or the like can be used as the material of the roller. Furthermore, it is also preferable to adopt a method of spreading the laminated body by passing it between rolls and applying pressure. At this time, these rollers may be made of the same material or different materials. The thickness of the adhesive layer bonded using the nip roll or the like before drying or curing is preferably 5 μm or less and 0.01 μm or more.

In order to improve the adhesiveness, surface treatments such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment may be appropriately performed on the adhesion surface of the film.

As a saponification process, the method of immersing in the aqueous solution of alkalis, such as sodium hydroxide and potassium hydroxide, is mentioned.

In the case of using a photocurable resin as an adhesive, after laminating the film, the photocurable adhesive is cured by irradiating active energy rays. The light source of the active energy ray is not particularly limited, but is preferably an active energy ray having a luminescence distribution below a wavelength of 400 nm. Specifically, it is preferable to use a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, Black light lamps, microwave excited mercury lamps, metal halide lamps, etc.

The light irradiation intensity to the photocurable adhesive can be appropriately determined according to the composition of the photocurable adhesive, and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is preferably 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1mW/ ^cm2 or more, the reaction time is not too long, and when it is 6000mW/ ^cm2 or less, the heat radiated from the light source and the curing of the photocurable adhesive rarely occur Yellowing of the epoxy resin and deterioration of the polarizing film caused by the heat generated during the time. The light irradiation time to the photocurable adhesive is a light irradiation time that can be used depending on the photocurable adhesive to be cured, and is not particularly limited, but it is preferably expressed in the form of the product of the above-mentioned irradiation intensity and irradiation time It is set in such a way that the accumulated light intensity reaches 10 to 10000mJ/cm ² . When the cumulative amount of light on the photocurable adhesive is 10mJ/cm2 or ^more , it can generate a sufficient amount of active species from the polymerization initiator to make the curing reaction more reliable, and it is ^below 10000mJ/cm2 In some cases, the irradiation time will not be too long, and good productivity can be maintained. The thickness of the adhesive layer after active energy ray irradiation is usually about 0.001 to 5 μm, preferably 0.01 μm to 2 μm, more preferably 0.01 μm to 1 μm.

When the photocurable adhesive on the base film and polyvinyl alcohol-based resin film is cured by irradiation with active energy rays, it is preferable to pass through all the steps without reducing the transmittance, hue, transparency, etc. of these films. Curing is carried out under the conditions of each function of the polarizing plate.

<Stretching process (S20)>

Here, the laminated film which consists of a base film and a polyvinyl-alcohol-type resin film is uniaxially stretched. It is preferable to perform uniaxial stretching at a draw ratio of more than 5 times and 17 times or less. More preferably, it is uniaxially stretched at a draw ratio of more than 5 times and 8 times or less. If the draw ratio is 5 times or less, the polyvinyl alcohol-based resin film will not be sufficiently oriented, and as a result, there may be a problem in which the degree of polarization of the polarizing plate layer cannot be sufficiently improved. On the other hand, when the stretching ratio exceeds 17 times, since the laminated film is likely to be broken during stretching, the workability and handleability in the post-process may be reduced. The stretching treatment in the stretching step (S20) is not limited to stretching in one stage, and may be carried out in multiple stages. When carrying out in multiple stages, it is preferable to perform stretching treatment at a stretching ratio exceeding 5 times in total for the total stages of stretching treatment.

In the stretching step ( S20 ) in the present invention, longitudinal stretching treatment in the longitudinal direction of the laminated film, transverse stretching treatment in the width direction, etc. may be performed. Examples of the longitudinal stretching method include an inter-roll stretching method, a compression stretching method, and the like, and examples of the lateral stretching method include a tenter method and the like.

<Dyeing process (S30)>

Here, the resin layer of the laminated film is dyed with a dichroic dye. Examples of dichroic dyes include iodine and organic dyes. As organic dyes, for example, red BR, red LR, red R, pink LB, ruby red BL, bordeaux GS, sky blue LG, tartrazine, blue BR, blue 2R, navy blue (Navy) RY, Green LG, Purple LB, Purple B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Bright Purple BK, Supra Blue G, Spra blue GL, Spra orange GL, direct sky blue, direct firm orange S, firm black, etc. These dichroic substances may be used alone or in combination of two or more.

The dyeing process is performed, for example, by immersing the entire stretched film in an aqueous solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution obtained by dissolving the aforementioned dichroic dye in a solvent can be used. As a solvent of the dyeing solution, water is usually used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, particularly preferably 0.025 to 5% by weight.

In the case of using iodine as the dichroic dye, it is preferable to further add iodide because the dyeing efficiency can be further improved. 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, titanium iodide wait. In the dyeing solution, the addition ratio of these iodides is preferably 0.01 to 20% by weight. Among iodides, potassium iodide is preferably added. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight, more preferably in the range of 1:6 to 1:80, particularly preferably in the range of 1:7 to 1: 70 range.

The immersion time of the stretched film in the dyeing solution is not particularly limited, but usually it is preferably in the range of 15 seconds to 15 minutes, more preferably 1 minute to 3 minutes. In addition, the temperature of the dyeing solution is preferably in the range of 10 to 60°C, more preferably in the range of 20 to 40°C.

<Crosslinking process>

Adhesive cross-linking treatment can be performed in the dyeing process. The crosslinking treatment can be performed, for example, by immersing the stretched film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, conventionally known ones can be used. For example, boron compounds, such as boric acid and borax, glyoxal, glutaraldehyde, etc. are mentioned. These may be used alone or in combination of two or more.

As the crosslinking solution, a solution obtained by dissolving a crosslinking agent in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is not limited thereto, but is preferably in the range of 1 to 20% by weight, more preferably 6 to 15% by weight.

In the crosslinking solution, iodide may be added. The addition of iodide can make the in-plane polarization characteristics of the resin layer more uniform. 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 iodide content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The immersion time of the laminated film in the crosslinking solution is usually preferably 15 seconds to 20 minutes, more preferably 30 seconds to 15 minutes. In addition, the temperature of the crosslinking solution is preferably in the range of 10 to 80°C.

<Washing process>

After the crosslinking step, it is preferable to perform a washing step. As the washing step, water washing treatment may be performed. The water washing treatment can generally be performed by immersing the laminated membrane in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 to 50°C, preferably in the range of 4°C to 20°C. The immersion time is usually 2 to 300 seconds, preferably 3 seconds to 240 seconds.

In the washing process, washing treatment with an iodide solution and water washing treatment may be combined, and a solution containing liquid alcohol such as methanol, ethanol, isopropanol, butanol, propanol, or the like may be suitably used.

<Drying process>

You may implement a drying process after a washing process. As a drying process, arbitrary appropriate methods (for example, natural drying, air drying, heat drying) can be employ|adopted. For example, the drying temperature during heat drying is usually 20 to 95° C., and the drying time is usually about 1 to 15 minutes.

Through the above steps, the polyvinyl alcohol-based resin film has a function as a polarizing plate layer, and a polarizing laminated film having a polarizing plate layer on one surface of a base film can be produced.

(polarizer layer)

Specifically, the polarizer layer is a polarizer layer in which an alignment dichroic dye is adsorbed on a uniaxially stretched polyvinyl alcohol-based resin film. The draw ratio is preferably more than 5 times, more preferably more than 5 times and 17 times or less.

The thickness of the polarizer layer (thickness of the stretched polyvinyl alcohol-based resin film) is preferably 25 μm or less, more preferably 20 μm or less, and preferably 2 μm or more. By setting the thickness of the polarizer layer to 25 μm or less, a thin polarizing laminated film can be constituted.

<Protective film bonding process (S40)>

A protective film is bonded to the surface of the polarizer layer in the polarizing laminated film opposite to the surface on the base film side. The bonding method of the polarizer layer and the protective film is not particularly limited. For example, an adhesive layer or an adhesive layer is formed on the bonding surface of the polarizer layer and/or the protective film, and both are bonded via the adhesive layer or the adhesive layer. The materials used for the adhesive layer and the adhesive layer are the same as the adhesive layer and the adhesive layer described in the column of the above-mentioned resin film bonding step (S10).

(protective film)

The protective film may be a simple protective film without an optical function, or a protective film having an optical function such as a retardation film or a brightness improvement film.

The material of the protective film is not particularly limited, and examples thereof include cyclic polyolefin-based resin films; cellulose acetate-based resin films formed of resins such as triacetylcellulose and diacetylcellulose; polyethylene terephthalate Polyester-based resin films made of resins such as glycol esters, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin films; acrylic-based resin films; polypropylene-based resin films etc., which have been widely used in this field.

As the cyclic polyolefin resin, suitable commercially available products such as Topas (registered trademark) (manufactured by Ticona Corporation), ARTON (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Japan ZEON Co., Ltd.) can be preferably used. Co., Ltd.), ZEONEX (registered trademark) (manufactured by Japan Zeon Co., Ltd.), APEL (registered trademark) (manufactured by Mitsui Chemicals Co., Ltd.), and the like. When forming such a cyclic polyolefin-based resin into a film, known methods such as a solvent casting method and a melt extrusion method can be appropriately used. In addition, ESCENA (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), ZEONOR (registered trademark) membrane (manufactured by Sekisui Chemical Co., Ltd.), etc., which have been prepared in advance, can also be used. The film is a commercially available film made of a cyclic polyolefin-based resin.

The cyclic polyolefin-based resin film may be uniaxially stretched or biaxially stretched. By stretching, arbitrary phase difference values can be provided to a cyclic polyolefin resin film. Usually, stretching can be performed continuously while winding up a film roll, and stretching can be performed in a heating furnace in the traveling direction of the roll, in a direction perpendicular to the traveling direction, or in both directions. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin-based resin to the glass transition temperature +100°C. The stretching ratio is usually 1.1 to 6 times per direction, preferably 1.1 to 3.5 times.

Cyclic polyolefin-based resin films generally have poor surface activity, so it is preferable to perform surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment on the surface to be bonded to the polarizer layer. Among them, plasma treatment and corona treatment, which can be performed relatively easily, are preferable.

As the cellulose acetate-based resin film, an appropriate commercial item can be used in advance, for example, FUJITAC (registered trademark) TD80 (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by Fujifilm Co., Ltd.), FUJITAC (manufactured by Fujifilm Co., Ltd. Registered trademark) TD80UZ (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD40UZ (manufactured by Fujifilm Co., Ltd.), KC8UX2M (manufactured by KONICA MINOLTA OPTO Co., Ltd.), KC4UY (manufactured by KONICA MINOLTA OPTO Co., Ltd.), etc.

In order to improve viewing angle characteristics, a liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film. In addition, the cellulose acetate-based resin film may be stretched in order to provide a phase difference. In order to improve the adhesiveness with a polarizing film, saponification treatment is generally given to a cellulose acetate resin film. As the saponification treatment, a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide can be employed.

Optical layers such as a hard coat layer, an antiglare layer, and an antireflection layer may also be formed on the surface of the above-mentioned protective film. The method of forming these optical layers on the surface of the protective film is not particularly limited, and known methods can be used.

The thickness of the protective film is preferably as thin as possible, preferably 90 μm or less, more preferably 50 μm or less, in view of the need for thinning. Conversely, if it is too thin, the strength will decrease and the workability will be poor, so it is preferably 5 μm or more.

<Base Film Peeling Step (S50)>

In the manufacturing method of the polarizing plate of this embodiment, as shown in FIG. 2, a base film peeling process (S50) is performed after the protective film bonding process (S40) of bonding a protective film to a polarizer layer. In a base film peeling process (S50), a base film is peeled from a polarizing laminated film. The peeling method of a base film is not specifically limited, The method similar to the peeling process of the peeling film performed in the polarizing plate with an ordinary adhesive agent can be employ|adopted. After the protective film bonding process (S40), it may be peeled off immediately, or may be wound up once in a roll shape, and another peeling process may be provided separately and peeled off. Through the above steps, a polarizing plate having a protective film on one surface of the polarizer layer can be manufactured.

(other optical layers)

In practical terms, the polarizing plate described above can be used as a polarizing plate in which other optical layers are laminated.

Moreover, the said protective film may also have the function of these optical layers.

Examples of other optical layers include a reflective polarizing film that transmits a certain polarized light and reflects polarized light that exhibits the opposite property, a film with an anti-glare function having an uneven surface, and a film with a surface anti-reflection function. film, reflective film with reflective function on the surface, semi-transmissive reflective film with both reflective and transmissive functions, viewing angle compensation film, etc.

As a commercially available product corresponding to a reflective polarizing film that transmits a certain polarized light and reflects polarized light that exhibits the opposite property, for example, DBEF (manufactured by 3M Co., Ltd., available from Sumitomo 3M Co., Ltd.), APF (3M Co., Ltd. company, available from Sumitomo 3M Co., Ltd.), etc. Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystalline compound is coated on the surface of a substrate and oriented, a retardation film made of polycarbonate resin, and a retardation film made of cyclic polyolefin resin. wait. Commercially available products corresponding to an optical compensation film in which a liquid crystalline compound is coated on the surface of a base material and oriented include WV film (manufactured by Fujifilm Co., Ltd.), NH film (manufactured by Nippon Oil Co., Ltd.) , NR film (manufactured by Nippon Oil Co., Ltd.), etc. Moreover, as a commercial item equivalent to the retardation film which consists of a cyclic polyolefin resin, ARTON (registered trademark) film (made by JSR (KK)), ESCENA (registered trademark) (Sekkisui Chemical Co., Ltd. )), ZEONOR (registered trademark) film (manufactured by OPTES Co., Ltd.), etc.

Example

[Example 1]

<Production of polyvinyl alcohol-based resin film>

Completely saponified polyvinyl alcohol resin (trade name: PVA124) powder sold by Kuraray Co., Ltd. was dissolved in warm water at 90°C to prepare a polyvinyl alcohol resin aqueous solution with a solid content concentration of 10 wt%. The obtained polyvinyl alcohol resin aqueous solution was applied to a thickness of about 400 μm by a lip coating method on a PET substrate subjected to a release treatment. After drying at 50° C. for 10 minutes, the polyvinyl alcohol-based resin film was peeled off from the PET substrate, and further dried at 80° C. for 5 minutes to obtain a polyvinyl alcohol-based resin film without curl. The thickness after drying was 41 μm.

<Resin film bonding process>

Polyvinyl alcohol powder and a crosslinking agent were dissolved in hot water to prepare an aqueous adhesive solution having the following composition. In addition, corona discharge treatment was performed on a 110 μm thick base film formed of polypropylene resin (trade name: FLX80E4, manufactured by Sumitomo Chemical Co., Ltd.), and the thickness after drying was about 0.2 μm using a gravure coater. way to apply the above-mentioned adhesive solution. Then, after bonding the above-mentioned polyvinyl alcohol-based resin film, it was made to dry at 50 degreeC for 3 minutes, and the laminated|multilayer film was obtained. The obtained laminated film was flat and easy to handle.

(adhesive aqueous solution)

Water: 100 parts by weight, polyvinyl alcohol resin powder (manufactured by Kuraray, average polymerization degree 18000, trade name: KL-318): 3 parts by weight, polyamide epoxy resin (crosslinking agent, Sumika CHEMTEX Co., Ltd. ), product name: SR650(30)): 1.5 parts by weight.

<Stretching process>

The laminated film was subjected to 5.8 times free-end uniaxial stretching at 160° C. using a tenter apparatus. The thickness of the stretched polyvinyl alcohol-based resin film was 18 μm.

<Dyeing process>

Then, the laminated film was immersed in a dyeing solution that was a mixed aqueous solution of iodine and potassium iodide at 30°C for about 180 seconds to dye the polyvinyl alcohol-based resin film, and the excess iodine solution was rinsed with pure water at 10°C. Next, it was immersed for 300 seconds in the crosslinking solution which is a mixed aqueous solution of borax and potassium iodide at 76°C. Then wash with pure water at 10° C. for 4 seconds, and finally remove excess water on the surface with pinch rollers. The compounding ratio of the chemical solution of each layer is as follows. The dyed laminated film was dried at 80° C. for 5 minutes to obtain a polarizing laminated film.

(staining solution)

Water: 100 parts by weight, iodine: 0.6 parts by weight, potassium iodide: 10 parts by weight.

(crosslinking solution)

Water: 100 parts by weight, boric acid: 9.5 parts by weight, potassium iodide: 5 parts by weight.

<Protective film bonding process>

An aqueous adhesive solution similar to that in the resin film bonding step was prepared. After coating the above-mentioned aqueous adhesive solution on the surface of the polarizer layer of the above-mentioned polarizing laminated film opposite to the surface of the base film, a protective film (TAC: KC4UY manufactured by KONICA MINOLTA OPTO Co., Ltd.) was attached, A polarizing plate composed of five layers of a base film, an adhesive layer, a polarizer layer, an adhesive layer, and a protective film was obtained.

<Substrate film peeling process>

After drying the above-mentioned polarizing plate at 80° C. for 5 minutes, a polarizing plate was obtained. The base film was peeled off from the obtained polarizing plate. The base film was easily peeled off, and a polarizing plate composed of four layers of an adhesive layer, a polarizer layer, an adhesive layer, and a protective film was obtained. The thickness of the polarizer layer was 18 μm. The polarization performance of the obtained polarizing plate was measured with a spectrophotometer (V7100) manufactured by JASCO Corporation. The incident direction of light is from the polarizer layer side. The transmittance of the visibility compensation monomer was 41.8%, and the degree of polarization of the visibility compensation was 99.997%. The polarization performance was very excellent, and it was performance sufficient to be used as a polarizing plate.

[Comparative Example 1]

After performing corona discharge treatment on the substrate film in the same manner as in Example 1, the aqueous solution of polyvinyl alcohol resin used to produce the polyvinyl alcohol-based resin film in Example 1 was directly coated by the gap coating method. . Thereafter, drying at 50° C. for 10 minutes and drying at 80° C. for 5 minutes were successively performed, but the polyvinyl alcohol resin layer was significantly curled due to drying shrinkage, and end bending occurred at the outlet of the drying oven. The thickness after drying of the obtained polyvinyl alcohol resin layer was about 39 μm.

Claims (5)

1. A method for producing a polarizing laminated film, the polarizing laminated film having a base film and a polarizer layer formed on one side of the base film, the method comprising the following steps in sequence: A resin film bonding step, bonding a resin film containing a polyvinyl alcohol-based resin with a thickness of 50 μm or less on one surface of the base film to obtain a laminated film; a stretching step of uniaxially stretching the laminated film; and In the dyeing step, the resin film of the uniaxially stretched laminated film is dyed with a dichroic dye to form a polarizer layer. 2. The method of claim 1, wherein, In the said resin film bonding process, the said resin film is bonded to one surface of the said base film via an adhesive layer or an adhesive layer. 3. The method according to claim 1 or 2, wherein, In the resin film bonding step, the resin film has a thickness of 15 μm or more. 4. The method according to any one of claims 1 to 3, wherein, The resin film used in the resin film bonding step is a resin film manufactured by a method including the following steps in order, The resin layer forming step is to form a resin layer containing a polyvinyl alcohol-based resin on the support, The first drying step is to dry the resin layer formed on the support body, a resin layer separation process of peeling the dried resin layer from the support to obtain the resin layer, and In the second drying step, the peeled resin layer is dried at a drying temperature higher than that in the first drying step. 5. A method of manufacturing a polarizing plate, the polarizing plate having a polarizer layer and a protective film formed on one surface of the polarizer layer, The method comprises the following steps in sequence after the polarizing laminated film is manufactured by the manufacturing method according to claim 1: a protective film bonding step of bonding a protective film to a surface of the polarizer layer in the polarizing laminated film opposite to the surface of the base film; and In the base film peeling step, the base film is peeled from the polarizing laminated film.

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