TW201702651A - Method of manufacturing polarizing plate attached with protective film - Google Patents

Abstract

The present invention provides a method of manufacturing a polarizing plate attached with a protective film, comprising a following step: laminating a protective film on one side of a polarizing plate and passing through one pair of laminating rolls for compression. The roll of the one pair of the laminating rolls, which contacts the protective film, has a surface speed of V1 (m/s), and the roll of the one pair of the laminating rolls, which contacts the polarizing plate, has a surface speed of V2 (m/s), wherein V1 and V2 satisfy a following relation: V1 < V2. In the step of compression, strength applied to the lamination comprising the polarizing plate and the protective film is 0.09 MPa or more.

Description

Method for manufacturing polarizing plate with protective film

The present invention relates to a method for producing a polarizing plate with a protective film formed by protecting a film on a surface layer of a polarizing plate.

In recent years, mobile terminal devices such as smart phones have been rapidly moving toward large screens and simplifying from the viewpoint of design and portability. In order to realize long-term driving in a limited thickness, it is desirable to use a polarizing plate for high brightness and thinness.

As a polarizing plate, a protective film made of triethyl fluorenyl cellulose (TAC) is usually bonded to a polarizing film made of a polyvinyl alcohol-based resin by an adhesive.

However, in recent years, a protective film made of a resin other than TAC is also used from the viewpoints of film formation, durability, cost, productivity, and the like (for example, Japanese Laid-Open Patent Publication No. 2004-245925).

The polarizing plate is highly sensitive to the environment in which it is placed, and is easily deformed into a bow shape depending on environmental conditions. In this specification, this deformation is also referred to as "curl". Curl has "positive curl" and "reverse Curl" 2 types. When the first main surface of the polarizing plate is bonded to the side of the image display element such as the liquid crystal cell and the second main surface on the opposite side, the "positive curl" means that the first main surface side is The convex curl, "reverse curl" refers to a curl that is convex on the second main surface side. When the polarizing plate is reversely curled, the adhesive layer is bonded to the image display element, which may cause a bonding error or a defect such as a bubble easily formed at the interface between the adhesive layer and the image display element.

Accordingly, the present invention provides a method of manufacturing an optical member including a polarizing plate structure and capable of sufficiently suppressing reverse curl.

The inventors of the present invention have based on the following: 1) The polarizing plate is usually a polarizing plate with a protective film attached to a peelable protective film (also referred to as a surface protective film) for protecting the surface thereof. In the case of the image, the image is displayed on the surface of the image display device, and most of the cases are adhered in the form of a polarizing plate with a protective film. 2) Therefore, in order to solve the above problem, The polarizer having a protective film can sufficiently suppress the reverse curl; further review is made to achieve the present invention. That is, the present invention provides a method of producing a polarizing plate with a protective film as shown below.

[1] A method for producing a polarizing plate with a protective film, comprising the steps of: protecting a film in a single-layer layer of a polarizing plate and passing between a pair of bonding rolls, thereby being extruded; wherein, in the foregoing one pair of lamination rollers affixed in contact with the protective film of the bonding roll surface speed V ₁ [m / s], and the surface speed of the paste in contact with the roll of the polarizing plate bonded V ₂ [m / s], satisfy the following Relationship of formula (I): V ₁ <V ₂ (I)

In the extrusion step, the pressure of the laminate including the polarizing plate and the protective film is 0.09 MPa or more.

[2] The production method according to [1], wherein when the polarizing plate is formed into a blade body, a curl is formed so that a side on which the protective film is superposed is convex.

[3] The production method according to the above [2], wherein the polarizing plate comprises a polarizing film, a first thermoplastic resin film laminated on one surface thereof, and a second thermoplastic resin film laminated on the other surface. .

[4] The production method according to the above [3], wherein the first thermoplastic resin film has a higher equilibrium moisture content than the second thermoplastic resin film at a temperature of 23 ° C and a relative humidity of 55%.

[5] The production method according to the above [4], wherein a difference in the equilibrium moisture ratio between the first thermoplastic resin film and the second thermoplastic resin film is 0.5% by weight or more.

[6] The production method according to any one of [3] to [5] wherein the protective film is disposed on the side of the first thermoplastic resin film.

The production method according to any one of the above aspects, wherein the first thermoplastic resin film has an equilibrium moisture content of 1.5% by weight or more.

[8] The production method according to any one of [1] to [7] wherein the polarizing plate has a thickness of 100 μm or less.

According to the present invention, it is possible to manufacture a polarizing plate with a protective film which can sufficiently suppress reverse curl. According to the polarizing plate with the protective film, the above-described defects can be suppressed, and the image display element can be implemented with good productivity. The fit of the pieces.

1‧‧‧Protective film

2, 2a, 2b, 2c‧‧‧ polarizing plate

3‧‧‧Polarizer with protective film

5, 5'‧‧‧ affixing rolls

10‧‧‧ polarizing film

20‧‧‧1st thermoplastic resin film

30‧‧‧2nd thermoplastic resin film

40‧‧‧Adhesive layer

50‧‧‧Separation membrane

Fig. 1 is a side view schematically showing an example of a method for producing a protective film-attached polarizing plate of the present invention.

Fig. 2 is a schematic view showing the MD curl, (a) is a side view, and (b) is a top view.

Fig. 3 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate.

Fig. 4 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate.

Fig. 5 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate.

(1) Extrusion step

Referring to Fig. 1, a method of manufacturing a protective film-attached polarizing plate according to the present invention includes superposing a protective film 1 on one side of a polarizing plate 2 and passing between a pair of bonding rolls 5, 5', whereby The laminate of the protective film 1 and the polarizing plate 2 is subjected to a step of pressing up and down, and a polarizing plate 3 with a protective film is produced by this step. Usually, the protective film 1 and the polarizing plate 2 supplied in the pressing step are continuously drawn out by the take-up rolls not shown in the drawing, and are continuously conveyed and introduced into one pair of bonding rolls 5, 5'. between. The transport direction of the protective film 1 and the polarizing plate 2 is the longitudinal direction of the film, and generally, the transport directions of the two are parallel to each other. In the present specification, MD means the mechanical flow direction of the film, that is, the direction of the long side of the film. Orthogonal to the MD, That is, the broad side direction of the film is also referred to as TD in this specification.

In the pair of bonding rolls, the surface speed V ₁ [m/s] of the bonding roller 5 contacting the protective film 1 and the surface speed V 2 of the bonding roller 5' contacting the polarizing plate ₂ [m/ s], satisfying the relationship of the following formula (I): V ₁ <V ₂ (I)

In the extrusion step, the pressure applied to the laminate including the polarizing plate 2 and the protective film 1 is 0.09 MPa or more.

The surface speed V ₁ of the bonding roller 5 and the surface speed V _{2 of the} bonding roller 5' are the actual surface speeds (true rotational speeds) of the bonding roller 5 or the bonding roller 5' in the nip portion. The surface speed V is specifically a value obtained by the following formula (II).

Surface velocity V[m/s]=radius of the bonding roller r[m]×angular velocity ω[rad/s] (II)

In the step of pressing by the pair of bonding rolls 5, 5', the pressure (nip pressure) of the laminated body to which the protective film 1 and the polarizing plate 2 are applied is 0.09 MPa or more.

The protective film 1 and the polarizing plate 2 are bonded to the nip portion in a state where the stress is larger than the protective film 1 by setting the nip to 0.09 MPa or more under the condition of the above formula (I). Then, by the polarizing plate 3 with the protective film attached to the nip portion, the shape of the polarizing plate 2 can be corrected in a concave direction (ie, a positive curling direction) in which the main surface of the protective film 1 is superposed (curly correction). . Therefore, for example, when the polarizing plate 2 supplied in the pressing step is subjected to reverse curling when the blade body is formed (to overlap the main surface of the protective film 1) In the case where the side is convexly curled, according to the present invention, the reverse curl can be corrected in the direction of the positive curl, and as a result, when the blade body is formed, it is possible to obtain a flattening which sufficiently suppresses the reverse curl, or which has no curl or has a positive A polarizing plate 3 with a protective film attached thereto. The obtained polarizing plate 3 with a protective film is preferably a flattened person having no curl or having a positive curl when formed into a blade body.

In order to make the surface speed V ₁ of the bonding roller 5 and the surface speed V _{2 of the} bonding roller 5' satisfy the relationship of the above formula (I), it is possible to adopt: (1) setting the angular velocity of the bonding roller 5' to be more suitable. The angular velocity of the roller 5 is faster, and (2) the diameter of the bonding roller 5' is set to be larger than the diameter of the bonding roller 5, and the methods of the above (1) and (2) are combined.

In the above extrusion step, the pressure (nip pressure) of the laminate to which the protective film 1 and the polarizing plate 2 are applied is preferably 0.09 MPa to 1 MPa, and may be 0.1 MPa to 0.5 MPa or 0.1 MPa to 0.2 MPa. When the nip pressure is less than 0.09 MPa, the pressing force of the laminate of the protective film 1 and the polarizing plate 2 in the nip portion is insufficient, and the reverse curl cannot be suppressed.

According to the present invention, since the curl correction of the polarizing plate 2 is performed by adjusting the surface speeds of the bonding rolls 5, 5' and the nip pressure, the tension applied to the polarizing plate 2 does not need to be finely controlled. Therefore, the present invention does not cause a defect due to the tension of the polarizing plate, so even in the case where the polarizing plate is very thin, or the polarizing plate contains an optical film which is easily affected by the tension, it can be suitably used. .

Here is a description of the curl. The curling refers to a deformation in which an optical member (optical film) such as the polarizing plate 2 or the polarizing plate 3 with a protective film is bent into an arc shape, and this deformation is usually generated in the blade body of the optical member. Curl has The tendency for the optical member to become a thinner film is more likely to occur.

The curl can be classified into two types of "positive curl" and "reverse curl" depending on which of the two main faces of the optical member is convex. When the main surface to be bonded to the image display element such as the liquid crystal cell is regarded as the first main surface, and the main surface on the opposite side is the second main surface, "positive curl" means the first main surface. The side is a convex curl, and the "reverse curl" is a curl which is convex on the second main surface side. In the polarizing plate 2 supplied in the production method of the present invention, when the blade body is formed, it is typically caused by reverse curl (curing with a convex surface on the main surface side of the protective film 1 being superposed).

Further, the curl is generated according to which end portion (edge) of the optical member attached to the blade body, and can be classified into two types of "MD curl" and "TD curl". Referring to Fig. 2, when the blade body of the optical member is placed on a flat table with the convex side facing downward, "MD curl" means that the ends (typically both ends) of the MD are lifted. The curl, "TD curl" refers to the curling of the ends (typically the ends) of the TD. In summary, the manufacturing method of the present invention is particularly useful for the correction of MD curl.

The evaluation of the curl (positive curl, reverse curl, MD curl, type of TD curl, and the amount of curl thereof) which the optical member such as the polarizing plate 2 or the polarizing plate 3 with the protective film can have is obtained. The optical member is formed by cutting the blade body. The blade body is such that a pair of opposite sides are parallel to the MD, and the remaining opposite sides are square blade bodies parallel to the TD, the MD length is set to 300 mm, and the TD length is set to 200 mm.

According to the present invention, sufficient shape can be obtained when forming a blade body The polarizing plate 3 with the protective film which suppresses the reverse curl is preferably a flattened person having no curl or a polarizing plate 3 having a protective film with a positive curl. According to the protective film-attached polarizing plate 3, when the adhesive layer is attached to the image display element, it is possible to effectively suppress the occurrence of a bonding error, or to mix air bubbles or the like at the interface between the adhesive layer and the image display element. In the defect, the bonding of the polarizing plate 3 with the protective film and the image display element can be performed with good productivity. Further, in the case where the curl generated by the polarizing plate 3 with the protective film is positively curled, the amount of curl is relatively large, and there is no particular problem with respect to the above defects and productivity. The polarizing plate 3 with a protective film obtained by the present invention may have reverse curl in a range in which the above-mentioned unsuitable disadvantage (preferably, the above-described defects are not caused) can be suppressed.

The amount of correction for the positive curling direction by the present invention is related to the difference between the left and right sides of the above formula (I), and the larger the difference, the greater the correction amount tends to be. The polarizing plate 2 supplied in the pressing step differs depending on how much curl is generated when the blade body is formed, but in order to obtain the polarizing plate 3 with the protective film obtained, it is assumed that there is no reverse curl. In the case of being flat or having a positive curl, the above extrusion step is preferably carried out under the condition that the following formula (III) is satisfied: V _{2 -} V ₁ ≧ 0.01 (III) The polarizing plate 2 supplied in the extrusion step In the case of having a large reverse curl, in order to make the obtained protective film-attached polarizing plate 3 flat or have a positive curl, it is sometimes necessary to set the left side of the above formula (III) to be larger than 0.01 (for example) It is 0.02 or more, 0.05 or more, 0.06 or more, 0.10 or more, 0.15 or more, 0.20 or more, or 0.24 or more). The left side of the above formula (III) may be, for example, 0.5 or less.

The surface speed V ₁ is usually 5 to 25 [m/s], more preferably 10 to 20 [m/s]. The surface speed V ₂ is usually 6 to 30 [m/s], more preferably 11 to 25 [m/s].

As the bonding rolls 5 and 5', a conventionally known one made of a metal (an alloy containing SUS or the like) or a rubber can be used.

When the long protective film 1 is superposed on one surface of the polarizing plate 2 and passed between the pair of bonding rolls 5, 5', the above-mentioned adhesive layer of the protective film 1 and the polarizing plate 2 are used. The way of single-sided contact is overlapped. Before the lamination of the protective film 1 and the polarizing plate 2, the bonding surface of at least one of the adhesive layer of the protective film 1 and the polarizing plate 2 may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame). ) Surface treatment such as treatment or saponification treatment.

(2) Protective film

The protective film 1 is usually composed of a substrate film and an adhesive layer laminated thereon. The protective film 1 is a film for protecting the surface of the polarizing plate 2. Usually, for example, after bonding the polarizing plate 3 with a protective film attached thereto, such as an image display element, it is peeled off together with the adhesive layer it has. Remove. The base film is a thermoplastic resin, and may be, for example, a polyolefin resin such as a polyethylene resin, a polypropylene resin or a cyclic polyolefin resin; polyethylene terephthalate or polyethylene naphthalate; A polyester resin, a polycarbonate resin, a (meth)acrylic resin, or the like. The adhesive layer may be composed of a (meth)acrylic adhesive, an epoxy adhesive, an amine ester adhesive, and a polyoxynoxy adhesive. Also, it can also be made of polypropylene resin and poly A resin layer having a self-adhesive property such as a vinyl resin.

In the present specification, the "(meth)acrylic resin" is at least one selected from the group consisting of an acrylic resin and a methacrylic resin. Other terms with "(methyl)" have the same meaning.

The thickness T _{1 of the} protective film 1 may be, for example, 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 120 μm, still more preferably 25 to 100 μm (for example, 90 μm or less, further 75 μm or less). In the case where the thickness T _{1 is} less than 5 μm, the protection of the polarizing plate 2 may become insufficient, and it is also disadvantageous in terms of handleability. Even if the strength becomes insufficient, there is a possibility that the effect of curl correction is lowered. When the thickness exceeds 200 μm, it is disadvantageous in terms of cost or rework of the protective film 1. From the viewpoint of the film formation, it is difficult to adjust the thickness of the polarizing film and the protective film constituting the polarizing plate in order to make the curl generated when the polarizing plate 2 is formed into a blade body to be flat or positively curled, but the protective film In general, for example, when a polarizing plate 3 with a protective film attached thereto is attached to an image display element or the like, it is peeled off, so that the thickness can be adjusted for the purpose of curl correction.

(3) Polarizer

The polarizing plate 2 is a polarizing element including at least a polarizing film, and generally includes a thermoplastic resin film such as a protective film laminated on at least one surface of the polarizing film. The protective film is an optical film responsible for protecting the polarizing film.

(3-1) Example of structure of polarizing plate

The polarizing plate 2 may include a polarizing film and a layer or film other than the protective film, for example, an optical layer or light having optical functions other than the polarizing film. Learn film. Examples of the other optical layer or optical film having an optical function are a retardation film (or retardation layer), a brightness enhancement film, and the like. Various optical films containing a protective film may be laminated on the polarizing film through an adhesive layer or an adhesive layer. Further, the polarizing plate 2 may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer.

The thickness T _{2 of the} polarizing plate 2 is usually 200 μm or less, and is preferably 125 μm or less, more preferably 100 μm or less, and still more preferably 75 μm or less from the viewpoint of film formation. The smaller the thickness T _{2 is} , the more easily the polarizing plate 2 is curled in the blade body. However, according to the present invention, even if the thickness of the polarizing plate 2 is thin, when the polarizing plate 2 is formed into a blade body, the reverse curl is generated. The reverse curl is effectively corrected in the direction of the positive curl.

An example of the layer configuration of the polarizing plate 2 will be described with reference to Figs. 3 to 5, but the layer structure is not limited to these examples. The polarizing plate 2a shown in Fig. 3 includes a polarizing film 10, a first thermoplastic resin film 20 bonded to one surface of the polarizing film 10, and a second thermoplastic resin bonded to the other surface of the polarizing film 10. The film 30; an adhesive layer 40 laminated on the outer surface of the second thermoplastic resin film 30; and a separation film 50 laminated on the outer surface of the adhesive layer 40. The separation membrane 50 is a peelable film for protecting the surface (outer surface) of the adhesive layer 40. The first and second thermoplastic resin films 20 and 30 are, for example, protective films.

The polarizing plate 2b shown in Fig. 4 may be omitted from one of the first and second thermoplastic resin films 20 and 30. The second thermoplastic resin film 30 is omitted from the polarizing plate 2b, and is directly on the outer surface of the polarizing film 10 (the surface opposite to the surface on which the first thermoplastic resin film 20 is laminated) The adhesive layer 40 is bonded. Such a polarizing plate having a thermoplastic resin film only on one side of the polarizing film 10 is advantageous for thinning of the polarizing plate. In the case of only one of the area-layer thermoplastic resin films of the polarizing film 10, although the polarizing plate 2 is liable to cause curling in the blade body thereof, according to the present invention, even since only one of the area layers of the polarizing film 10 is attached to heat In the plastic resin film, when the polarizing plate 2 is formed into a blade body, the reverse curl is generated, and the reverse curl can be efficiently corrected in the positive curl direction.

Further, as in the polarizing plate 2c shown in Fig. 5, the adhesive layer 40 and the separation film 50 may be omitted. The polarizing plate 2 may have a protective film different from the protective film 1 supplied in the above-described pressing step in advance on one side. At this time, the obtained polarizing plate 3 with a protective film may be a polarizing plate having a protective film on both sides.

Although not shown in the drawings in FIGS. 3 to 5, the bonding of the polarizing film 10 to the first and second thermoplastic resin films 20 and 30 is preferably carried out using an adhesive.

(3-2) polarizing film

The polarizing film 10 may be a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and uniaxially stretched. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film can be obtained by saponification using a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to the polyvinyl acetate of the homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate can be exemplified. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups. Base) acrylamide and the like.

The degree of saponification of the polyvinyl alcohol-based resin may range from 80.0 to 100.0 mol%, preferably from 90.0 to 100.0 mol%, more preferably from 94.0 to 100.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and the moist heat resistance of the obtained polarizing plate 2 are lowered.

The degree of saponification is a ratio of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin to a hydroxyl group by a saponification step in a unit ratio (% by mole) As shown, it is defined by the following formula: Saponification degree (% by mole) = 100 × (hydroxyl number) / (hydroxyl number + number of acetate groups) The degree of saponification can be determined in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of hydroxyl groups, and thus the fact that the ratio of the acid group which inhibits crystallization is lower.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, still more preferably from 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarizing performance, and when it exceeds 10,000, the solubility in a solvent is deteriorated, and formation of a polyvinyl alcohol-based resin film becomes difficult.

The dichroic dye contained in the polarizing film 10 (adsorption alignment) may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye include: Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue Direct Fast Orange S, Fast Black. The dichroic dye may be used alone or in combination of two or more. The dichroic dye is preferably iodine.

The polarizing film 10 can be produced by a step of uniaxially stretching a polyvinyl alcohol-based resin film, and a step of dyeing the polyvinyl alcohol-based resin film by dichroic dye, thereby adsorbing the dichroic dye; a step of crosslinking the polyvinyl alcohol-based resin film to which the dichroic dye has been adsorbed; and a step of performing water washing after the crosslinking treatment.

The polyvinyl alcohol-based resin film is obtained by forming a film of the above polyvinyl alcohol-based resin. The film forming method is not particularly limited, and a known method such as a melt extrusion method or a solvent casting method can be employed. The thickness of the polyvinyl alcohol-based resin film is, for example, about 10 to 150 μm, preferably 50 μm or less, and more preferably 35 μm or less.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be carried out simultaneously with or after dyeing before dyeing of the dichroic dye. The uniaxial stretching is carried out after dyeing, and the uniaxial stretching can also be carried out before the crosslinking treatment or in the crosslinking treatment. Also, uniaxial stretching may be performed in these plural stages.

For uniaxial extension, it can be extended to a single axis between rolls with different circumferential speeds, or it can be extended to a single axis using a heat roller. Further, the uniaxial extension may be a dry extension extending in the atmosphere or may be carried out in a solution. The wet stretching of the polyvinyl alcohol resin film extension. The stretching ratio is usually about 3 to 8 times.

As a method of dyeing the polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing a dichroic dye can be employed. The polyvinyl alcohol-based resin film is preferably an immersion treatment (swelling treatment) which is first applied to water before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine or potassium iodide and dyed is usually used. The content of iodine in the aqueous dyeing solution is usually 0.01 to 1 part by weight per 100 parts by weight of water. Further, the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous dyeing solution is usually about 20 to 40 °C.

On the other hand, in the case where a dichroic organic dye is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in a dyeing aqueous solution containing a water-soluble dichroic organic dye and dyed is usually used. The content of the dichroic organic dye in the aqueous dyeing solution is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The aqueous dyeing solution may also contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. The temperature of the aqueous dyeing solution is usually about 20 to 80 °C.

The cross-linking treatment after dyeing by the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing a crosslinking agent. A suitable example of the crosslinking agent is boric acid, but other crosslinking such as borax-like boron compound, glyoxal, glutaraldehyde or the like can also be used. Agent. The crosslinking agent may be used alone or in combination of two or more.

The amount of the crosslinking agent in the aqueous solution containing the crosslinking agent is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of the water. In the case where iodine is used as the dichroic dye, the aqueous solution containing the crosslinking agent is preferably potassium iodide. The amount of potassium iodide in the aqueous solution containing the crosslinking agent is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution containing the crosslinking agent is usually 50 ° C or higher, preferably 50 to 85 ° C.

The polyvinyl alcohol-based resin film after the crosslinking treatment is usually subjected to a water washing treatment. The water washing treatment can be carried out, for example, by immersing the crosslinked polyvinyl alcohol resin film in water. The temperature of the water in the water washing treatment is usually about 1 to 40 °C.

After the water washing, drying treatment is carried out to obtain a polarizing film 10. The drying treatment may be drying by a hot air dryer, drying by contact with a hot roll, drying by a far infrared ray heater, or the like. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 90 ° C.

The thickness of the polarizing film 10 is usually about 2 to 40 μm. The thickness of the polarizing film 10 is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less from the viewpoint of thinning of the polarizing plate 2 . The smaller the thickness of the polarizing film 10, the more easily the polarizing plate 2 is curled in the blade body. However, according to the present invention, even if the thickness of the polarizing film 10 is small, the polarizing plate 2 is reversely curled when it is formed into a blade body. This reverse curl can be efficiently corrected in the positive curl direction.

(3-3) First and second thermoplastic resin films

The first and second thermoplastic resin films 20 and 30 are each independently formed of a light-transmissive thermoplastic resin, preferably an optically transparent thermoplastic resin. The thermoplastic resin constituting the first and second thermoplastic resin films 20 and 30 may be, for example, a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (a norbornene resin or the like). Polyolefin-based resin; such as cellulose-based resin such as triethylenesulfonyl cellulose or diethyl hydrazine cellulose; polyester resin such as polyethylene terephthalate or polybutylene terephthalate Polycarbonate resin; (meth)acrylic resin such as methyl methacrylate resin; polystyrene resin; polyvinyl chloride resin; acrylonitrile-butadiene-styrene resin; acrylonitrile - styrene resin; polyvinyl acetate resin; polyvinylidene chloride resin; polyamine resin; polyacetal resin; modified polyphenylene ether resin; polyfluorene resin; Resin; polyarylate resin; polyamidoximine resin; polyimide resin.

In addition to a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, a copolymer of two or more kinds of chain olefins may be mentioned as the chain polyolefin resin. More specific examples include a polypropylene resin (a polypropylene resin as a homopolymer of propylene, or a copolymer having propylene as a main component), and a polyethylene resin (polyethylene as a homopolymer of ethylene) Resin, or a copolymer of ethylene as the main body).

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin and a cyclic olefin. Addition polymer, a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene (represented by a random copolymer), and such modified by an unsaturated carboxylic acid or a derivative thereof Grafted polymers, and such hydrides and the like. Among them, as the cyclic olefin, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is preferably used.

Cellulose resin refers to a part or all of hydrogen atoms in the hydroxyl group of cellulose obtained from cellulose such as cotton or wood pulp (broadwood pulp, conifer pulp), or all of which are replaced by ethyl, propyl and/or butyl groups. The cellulose organic acid ester or cellulose mixed organic acid ester is obtained. For example, an acetate, a propionate, a butyrate of cellulose, a mixed ester of these, etc. are mentioned. Among them, triethyl fluorenyl cellulose, diethyl hydrazine cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferred.

The polyester resin has an ester bond, and the resin other than the above cellulose resin is generally composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and naphthalene dicarboxylic acid. Ester and the like. As the polyol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol. An example of a suitable polyester resin comprises polyethylene terephthalate.

The polycarbonate resin is an engineering plastic composed of a polymer having a monomer unit bonded through a carboxylate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. Polycarbonate-based resin In order to lower the photoelastic coefficient, the polycarbonate resin may also be a polymer skeleton. A modified resin called modified polycarbonate or a copolymerized polycarbonate having improved wavelength dependence.

The (meth)acrylic resin is a polymer containing a structural unit derived from a (meth)acrylic monomer. The polymer is typically a polymer containing methacrylate. It is preferred to contain a polymer having a ratio of structural units derived from methacrylate of 50% by weight or more based on the entire structural unit. The (meth)acrylic resin may be a homopolymer of methacrylate or a copolymer containing a structural unit derived from another polymerizable monomer. In this case, the ratio of the structural unit derived from the other polymerizable monomer is preferably 50% by weight or less based on the entire structural unit.

As the methacrylate which can constitute a (meth)acrylic resin, an alkyl methacrylate is preferable. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and butyl methacrylate. a methyl group having 1 to 8 carbon atoms of an alkyl group such as ester, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate or 2-hydroxyethyl methacrylate Alkyl acrylate. The alkyl group contained in the alkyl methacrylate preferably has 1 to 4 carbon atoms. In the (meth)acrylic resin, one type of the methacrylate may be used alone or two or more types may be used in combination.

Examples of the other polymerizable monomer which can constitute the (meth)acrylic resin include an acrylate and other compounds having a polymerizable carbon atom-carbon atom double bond in the molecule. The other polymerizable monomers may be used alone or in combination of two or more. As the acrylate, an alkyl acrylate is preferred. As the alkyl acrylate, there may be mentioned, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethyl acrylate. An alkyl acrylate having 1 to 8 carbon atoms in an alkyl group such as hexyl ester, cyclohexyl acrylate or 2-hydroxyethyl acrylate. The number of carbon atoms of the alkyl group contained in the alkyl acrylate is preferably from 1 to 4. In the (meth)acrylic resin, the acrylate may be used alone or in combination of two or more.

Examples of the other compound having a polymerizable carbon atom-carbon atom double bond in the molecule include a vinyl compound such as ethylene, propylene or styrene, or a vinyl cyanide compound such as acrylonitrile. Other compounds having a polymerizable carbon atom-carbon atom double bond in the molecule may be used alone or in combination of two or more.

The first and second thermoplastic resin films 20 and 30 may be a protective film that is laminated on one surface of the polarizing film 10 to protect the polarizing film 10. The first or second thermoplastic resin films 20 and 30 may be protective films having optical functions such as a retardation film and a brightness enhancement film. For example, by extending a thermoplastic resin film composed of the above material (uniaxial stretching or biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film, a phase difference which has been given an arbitrary phase difference value can be obtained. membrane. The first and/or second thermoplastic resin films 20 and 30 may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer laminated on the surface thereof. ).

Thickness of the first and second thermoplastic resin films 20 and 30 The degree is usually from 1 to 100 μm, preferably from 5 to 60 μm, more preferably from 5 to 50 μm, from the viewpoints of strength and handleability. When the thickness is within this range, the polarizing film 10 can be mechanically protected, and shrinkage of the polarizing film 10 when the polarizing plate 2 is exposed to a hot and humid environment can be suppressed. The smaller the thickness of the first thermoplastic resin film 20 or the second thermoplastic resin film 30, the more the polarizing plate 2 is curled in the blade body, but according to the present invention, the first thermoplastic resin film 20 or the second heat The thickness of the plastic resin film 30 is as thin as, for example, 40 μm or less, or even as thin as 30 μm or less, and even if the reverse curl is generated when the polarizing plate 2 is formed into a blade body, the reverse curl can be effectively corrected in the positive curl direction.

In the polarizing plates 2a and 2c shown in FIG. 3 and FIG. 5, the first thermoplastic resin film 20 is provided on one surface of the polarizing film 10, and the second thermoplastic resin film 30 is provided on the other surface. 1 The thermoplastic resin film 20 and the second thermoplastic resin film 30 may be composed of the same type of thermoplastic resin, or may be composed of different types of thermoplastic resins, but may be composed of different types of thermoplastic resins. In the case where the equilibrium moisture ratio or the moisture permeability of the thermoplastic resin film bonded to both surfaces are different from each other, curling is particularly likely to occur in the blade body of the polarizing plate 2, and thus the present invention is particularly advantageous in such a case.

For example, as the first thermoplastic resin film 20, a film having a higher equilibrium moisture ratio than the second thermoplastic resin film 30 can be used. When the difference between the equilibrium moisture ratios of the first thermoplastic resin film 20 and the second thermoplastic resin film 30 bonded to both surfaces of the polarizing film 10 is higher, the polarizing plate 2 is more likely to be curled in the blade body, but The present invention, the equilibrium moisture rate The difference is 0.5% by weight or more, further 1% by weight or more, and further 1.5% by weight or more. Even if the reverse curl is generated when the polarizing plate 2 is formed into a blade body, the reverse curl can be effectively corrected. Correction of the curl direction.

In the present specification, the equilibrium moisture content of the film is measured by the dry weight method, and specifically, it is determined according to the following formula: Equilibrium moisture content (% by weight) = {(film weight before drying treatment - film weight after drying treatment) / film weight before drying treatment} × 100 Here, the film weight before drying treatment is to store the film at temperature 23 The weight after 24 hours in an environment of ° C and a relative humidity of 55%, drying means that the film is dried at 105 ° C for 2 hours. The combination of a thermoplastic resin film having a difference in the moisture content of 0.5% by weight or more, for example, a combination of a cellulose resin film (such as a TAC film) and a cyclic polyolefin resin film, and a cellulose resin film. Combination of a (TAC film or the like) and a (meth)acrylic resin film, a combination of a cellulose resin film (such as a TAC film) and a polyester resin film, a cellulose resin film (such as a TAC film), and a chain polymerization The combination of an olefin resin film, a combination of a (meth)acrylic resin film and a cyclic polyolefin resin, a combination of a (meth)acrylic resin film and a polyester resin film, and the like. The difference in equilibrium moisture ratio between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5% by weight or less, preferably 2.5% by weight or less.

The equilibrium moisture content of the first thermoplastic resin film 20 is, for example, 1.5% by weight or more, and may be 2% by weight or more. The equilibrium moisture content of the first thermoplastic resin film 20 is usually 5% by weight or less.

In the case where the film having a higher equilibrium moisture ratio than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, the second The equilibrium moisture content of the thermoplastic resin film 20 is usually from 0.1 to 1.5% by weight, preferably from 0.1 to 1% by weight. Examples of the thermoplastic resin constituting the second thermoplastic resin film 20 that can achieve the relevant equilibrium moisture content include a cyclic polyolefin resin, a (meth)acrylic resin, a polyester resin, and a chain polyolefin resin. Wait.

The equilibrium moisture content of the thermoplastic resin film may be, depending on the material (the type of the thermoplastic resin constituting the film), depending on the thickness of the film, the presence or absence of a surface treatment layer (coating layer) which may be attached to the surface of the film, or Material and other adjustments.

When a film having a higher equilibrium water content than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, it is easy to cause the reverse curl of the polarizing plate 2 to be corrected in the positive curl direction. In the above-described pressing step, the protective film 1 is disposed on the side of the first thermoplastic resin film 20 of the polarizing plate 2.

Further, for example, as the first thermoplastic resin film 20, a film having a higher moisture permeability than the second thermoplastic resin film 30 can be used. The larger the difference in the moisture permeability between the first thermoplastic resin film 20 and the second thermoplastic resin film 30 bonded to both surfaces of the polarizing film 10, the more the polarizing plate 2 is curled in the blade body, but according to the present invention The difference in the moisture permeability is at least 30 g / (m ² ‧ 24 hr), further at 50 g / (m ² ‧ 24 hr) or more, and further at 100 g / (m ² ‧ 24 hr) or more, even if the polarizing plate 2 When the blade body is formed, the reverse curl is generated, and the reverse curl can be effectively corrected in the direction of the positive curl.

The moisture permeability of the film in the present specification is the moisture permeability at a temperature of 40 ° C and a relative humidity of 90% as measured by a cup method defined in JIS Z 0208. A combination of a thermoplastic resin film having a difference in moisture permeability of 30 g/(m ² ‧24 hr) or more, for example, a combination of a cellulose resin film (such as a TAC film) and a cyclic polyolefin resin film Combination of a cellulose resin film (such as a TAC film) and a (meth)acrylic resin film, a combination of a cellulose resin film (such as a TAC film) and a polyester resin film, and a cellulose resin film (TAC film) The combination with a chain polyolefin resin film, a combination of a (meth)acrylic resin film and a cyclic polyolefin resin, a combination of a (meth)acrylic resin film and a polyester resin film, and the like. The difference in moisture permeability between the first thermoplastic resin film 10 and the second thermoplastic resin film 20 is usually 5,000 g/(m ² ‧24 hr) or less.

The moisture permeability of the first thermoplastic resin film 20 is, for example, 300 g/(m ² ‧24 hr) or more, and may be 400 g/(m ² ‧24 hr) or more. When the moisture permeability is 300 g/(m ² ‧24 hr) or more, when the first thermoplastic resin film 20 and the polarizing film 10 are bonded together using a water-based adhesive, the water-based adhesive can be efficiently formed. Dry layering is also advantageous from the point of view that productivity can be improved. The moisture permeability of the first thermoplastic resin film 20 is usually 5,000 g/(m ² ‧24 hr) or less.

When a film having a higher moisture permeability than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, the moisture permeability of the second thermoplastic resin film 20 is usually from 1 to 350 g/(m ² ‧24 hr). It is preferably 5 to 200 g / (m ² ‧ 24 hr). Examples of the thermoplastic resin constituting the second thermoplastic resin film 20 that can achieve the relative moisture permeability include a cyclic polyolefin resin, a (meth)acrylic resin, a polyester resin, a chain polyolefin resin, and the like. .

The moisture permeability of the thermoplastic resin film may be, depending on the material (the type of the thermoplastic resin constituting the film), depending on the thickness of the film, the presence or absence of the surface treatment layer (coating layer) or the material on the surface of the film. Make adjustments.

When a film having a higher moisture permeability than the second thermoplastic resin film 30 is used as the first thermoplastic resin film 20, it is usually from the viewpoint of correcting the reverse curl of the polarizing plate 2 toward the positive curling direction. In the pressing step, the protective film 1 is disposed on the side of the first thermoplastic resin film 20 of the polarizing plate 2.

As described above, the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be bonded together using an adhesive. Before the first and second thermoplastic resin films 20 and 30 are laminated on the polarizing film 10, the bonding surface of the polarizing film 10 and/or the first and second thermoplastic resin films 20 and 30 may be subjected to, for example, plasma. Surface activation treatment such as treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, and the like. By the surface activation treatment, the adhesion between the polarizing film 10 and the first and second thermoplastic resin films 20 and 30 can be improved.

As the adhesive, a water-based adhesive, an active energy ray-curable adhesive or a thermosetting adhesive can be used, and a water-based adhesive or an active energy ray-curable adhesive is preferable. In the case where the thermoplastic resin film is laminated on both surfaces of the polarizing film 10, the adhesive on both sides may be the same type of adhesive or a different type of adhesive. In the case where different kinds of adhesives are used, the polarizing plate 2 is easy to produce in the blade body thereof. According to the present invention, even if a reverse curl is generated when the polarizing plate 2 is formed into a blade body by using different kinds of adhesives, the reverse curl can be effectively corrected in the positive curl direction.

A water-based adhesive is one in which the adhesive component is dissolved in water or dispersed in water. A water-based adhesive which can be preferably used is, for example, an adhesive composition using a polyvinyl alcohol-based resin or a polyurethane resin as a main component.

When a polyvinyl alcohol-based resin is used as a main component of the adhesive, the polyvinyl alcohol-based resin may be, for example, a polyvinyl alcohol resin such as partially saponified polyvinyl alcohol or fully saponified polyvinyl alcohol, or may be: A modified polyvinyl alcohol-based resin such as a carboxyl group-modified polyvinyl alcohol, an ethylene glycol-modified polyvinyl alcohol, a methylol-modified polyvinyl alcohol or an amine-modified polyvinyl alcohol. The polyvinyl alcohol-based resin may be a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate homopolymer of vinyl acetate, or may be vinyl acetate and other mono-polymerizable copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by subjecting a bulk copolymer to saponification.

A water-based adhesive which uses a polyvinyl alcohol-based resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the subsequent agent is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of water.

In order to improve adhesion, an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is, for example, a polyvalent aldehyde, a melamine-based compound, a zirconia compound, a zinc compound, glyoxal, a glyoxal derivative, or a water-soluble epoxy resin. It is preferred that a resin or the like contains a curable component or a crosslinking agent. As water As the soluble epoxy resin, a polyamidamine polyamine epoxy resin such as a polyalkylene polyamine such as di-ethyltriamine or tri-extended ethyltetraamine may be suitably used. A polyamidoamine obtained by a reaction of a dicarboxylic acid such as a diacid is obtained by reacting with epichlorohydrin. As a commercial product of the related polyamine polyamine epoxy resin, "Sumirez Resin 650" (made by Tajika Chemical Industry Co., Ltd.), "Sumirez Resin 675" (made by Tajika Chemical Industry Co., Ltd.), " WS-525" (Japan PMC (share) system) and so on. The amount of the curable component or the crosslinking agent added (as a total amount when the curable component and the crosslinking agent are simultaneously added) is usually 1 to 100 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin. It is preferably from 1 to 50 parts by weight. When the amount of the curable component or the crosslinking agent added is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving the adhesion tends to be small, and the amount of addition is relatively small. When 100 parts by weight of the polyvinyl alcohol-based resin is more than 100 parts by weight, the adhesive layer tends to become brittle.

Further, a suitable example of the case where a polyurethane is used as a main component of the adhesive agent is a mixture of a polyester-based ionic polymer-type amine ester resin and a compound having a glycidoxy group. The polyester-based ionic polymer type urethane resin refers to an amine ester resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. The ionic polymer type amine ester resin is emulsified directly into water to form a latex without using an emulsifier, and is therefore suitable as an aqueous adhesive.

In the case of using a water-based adhesive, after the polarizing film 10 is bonded to the first and/or second thermoplastic resin films 20 and 30, a drying step for removing moisture contained in the aqueous adhesive is performed. good. After the drying step, a ripening step of, for example, aging at a temperature of 20 to 45 ° C may be provided.

The active energy ray-curable adhesive is an adhesive which is cured by irradiation with active energy rays such as ultraviolet rays, visible rays, electron beams, and X-rays. When the active energy ray-curable adhesive is used, the adhesive layer of the polarizing plate 2 is a cured layer of the adhesive.

The active energy ray-curable adhesive may be an adhesive containing an epoxy compound which is cured by cationic polymerization as a curable component, and preferably contains an ultraviolet curing method in which the epoxy compound is used as a curable component. Sexual adhesive. The epoxy compound herein means a compound having an average of one or more, preferably two or more epoxy groups in the molecule. The epoxy compound may be used alone or in combination of two or more.

Specific examples of the epoxy-based compound which can be suitably used include a hydrogenated epoxy obtained by reacting an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol with epichlorohydrin. a compound (glycidyl ether of a polyhydric alcohol having an alicyclic ring); a polyglycidyl ether-like aliphatic epoxy compound such as an aliphatic polyhydric alcohol or an epoxide adduct thereof; one in the molecule The above alicyclic epoxy compound bonded to the epoxy compound of the alicyclic ring.

The active energy ray-curable adhesive may contain a radically polymerizable (meth)acrylic compound as a curable component instead of or in addition to the above epoxy compound. Examples of the (meth)acrylic compound include a (meth) acrylate monomer having at least one (meth) propylene fluorenyloxy group in the molecule; and a combination of two or more kinds of functional groups. A (meth)acryloxy group-containing compound having at least two (meth) acryloxy group-containing (meth) acrylate oligomers in the molecule, which is obtained by a reaction.

When the active energy ray-curable adhesive contains an epoxy compound which is cured by cationic polymerization as a curable component, it is preferred to contain a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include an aromatic diazonium salt; an onium salt such as an aromatic iodonium salt or an aromatic onium salt; and an iron-aromatic hydrocarbon complex. Further, when the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth)acrylic compound, it is preferred to contain a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, and xanthone. , fluorenone, camphorquinone, benzaldehyde, hydrazine and the like.

In the case where the active energy ray-curable adhesive is used in the lamination of the polarizing film 10 and the first and/or second thermoplastic resin films 20 and 30, after the lamination, the drying step is performed as needed, and then the irradiation is performed. The active energy ray active energy line hardens the active energy ray-curable adhesive to perform the hardening step. Although the light source of the active energy ray is not particularly limited, it is preferably an ultraviolet ray having a light-emitting distribution at a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, or a black light can be used. Lights, microwaves, mercury lamps, metal halide lamps, etc.

The active energy ray irradiation intensity of the adhesive layer composed of the active energy ray-curable adhesive is appropriately determined depending on the composition of the adhesive, but is effective in setting the activation wavelength of the polymerization initiator. The irradiation intensity is preferably 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and in the case of 6000 mW/cm ² or less, the yellow of the adhesive layer is caused by heat radiated from the light source and heat generated by curing of the adhesive. The variable or polarizing film 10 may be less likely to deteriorate.

For the active energy ray irradiation time, although depending on the composition of the adhesive agent are appropriately determined, but is set to be shown by the accumulation of the intensity of the irradiation light and the irradiation time of the product amounted to 10 10000mJ / cm ² are preferred. When the cumulative amount of light is 10 mJ/cm ² or more, the amount of active species derived from the polymerization initiator can be sufficiently increased to carry out the curing reaction more reliably. In the case of 10000 mJ/cm ² or less, the irradiation time does not become too long. The good productivity of the polarizing plate 2 can be maintained.

(3-4) Adhesive layer and separation membrane

As shown in FIGS. 3 and 4, the polarizing plate 2 may contain an adhesive layer 40. The adhesive layer 40 can be directly laminated on the surface of the first or second thermoplastic resin film 20, 30 or the polarizing film 10, and the polarizing plate 3 with the protective film can be used for bonding to the image. A display element (such as a liquid crystal cell).

The adhesive layer 40 for bonding the polarizing plate 3 with a protective film to an image display element (for example, a liquid crystal cell) is disposed on the main surface of the polarizing plate on the side of the image display element such as a liquid crystal cell. (1st main surface) side. For example, the polarizing plate 2 contains the first and second thermoplastic resin films 20 and 30, and a film having a higher moisture permeability than the second thermoplastic resin film 30 is used. In the case of the first thermoplastic resin film 20, the adhesive layer 40 may be disposed on the side of the second thermoplastic resin film 30.

The adhesive layer 40 may be an adhesive composition containing a resin such as (meth)acrylic, rubber, amine ester, ester, polyoxyn, or polyvinyl ether as a main component (base polymer). Composition. Among them, an (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, and the like is preferably used as an adhesive composition of a base polymer. The adhesive composition may also be an active energy ray-hardening type or a thermosetting type.

As the (meth)acrylic resin to be used in the adhesive composition, for example, it is suitably used: for example, butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, (A) One or two or more of the (meth) acrylate-like (meth) acrylate-based polymers or copolymers. Among the (meth)acrylic resins, it is preferred to copolymerize with a polar monomer. Examples of the polar monomer include, for example, (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, decyl (meth)acrylate, and N,N-di. A monomer having a carboxyl group, a hydroxyl group, a decylamino group, an amine group, an epoxy group or the like, such as methylaminoethyl (meth) acrylate or glycidyl (meth) acrylate.

The adhesive composition may be one containing only the above-mentioned base polymer, but usually may further contain a crosslinking agent. The crosslinking agent may, for example, be a metal ion having a valence of 2 or more and a metal carboxylic acid salt formed between the carboxyl group; a polyamine compound; and a guanamine bond may be formed between the carboxyl group; Or a polyol, and an ester bond is formed between the carboxyl group; a polyisocyanate compound, and a guanamine bond is formed between the carboxyl group and the carboxyl group. among them, A polyisocyanate compound is preferred.

The active energy ray-curable adhesive composition has a property of being cured by irradiation with an active energy ray such as ultraviolet rays or electron beams, and is also adhesive before adhesion to an active energy ray and can be adhered to a film or the like. In the above, there is an adhesive composition which can be cured by irradiation with an active energy ray to adjust the adhesion. The active energy ray-curable adhesive composition is preferably an ultraviolet curable type. The active energy ray-curable adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, a photopolymerization initiator or a photosensitizer or the like may be contained as occasion demands.

The adhesive composition may contain: fine particles for imparting light dispersibility, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers ( Additives such as metal powder or other inorganic powders, antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, corrosion inhibitors, photopolymerization initiators, and the like.

The adhesive layer 40 can apply the organic solvent diluent of the above-mentioned adhesive composition to the adhesive layer forming surface of the polarizing plate 2 (that is, the polarizing film 10 or the first or second thermoplastic resin film 20, 30) Upper coating, drying, and thereby formed. Alternatively, the organic solvent diluent of the above adhesive composition may be applied onto a separation membrane (for example, separation membrane 50), dried to form an adhesive layer, and then transferred to an adhesive layer of the polarizing plate 2. surface. In either method, it is preferred to apply a separation film to the outside of the adhesive layer 40 to protect the adhesive layer 40 in advance until use. In the case of using an active energy ray-curable adhesive composition, by the adhesion formed The agent layer illuminates the active energy ray to form a cured product having a desired degree of hardening. The thickness of the adhesive layer 40 is usually from 1 to 40 μm, but from the viewpoint of film formation of the polarizing plate 2, it is preferably from 3 to 25 μm.

The separation film 50 is used to protect the film adhered to the surface of the adhesive layer 40 before it is attached to an image display element (for example, a liquid crystal cell). The separation membrane 50 is usually composed of a thermoplastic resin film which has been subjected to release treatment on one side, and the release treatment surface is bonded to the adhesive layer 40. The thermoplastic resin constituting the separation membrane 50 may be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, or a polyester such as polyethylene terephthalate or polyethylene naphthalate. Resin or the like. The thickness of the separation membrane 50 is, for example, 10 to 100 μm.

(3-5) Other structural elements of the polarizing plate

The polarizing plate 2 may contain other components other than the above. The other constituent elements include an optical layer or an optical film having an optical function other than the polarizing film 10, and a specific example thereof is an optical film such as a retardation film or a brightness enhancement film. Other optical films can be laminated by an adhesive layer or an adhesive layer.

Further, the polarizing plate 2 may contain a protective film different from the protective film 1 supplied in the above-described pressing step. The protective film is disposed on one surface of the polarizing plate 2. Regarding the structure of this protective film, the above description about the protective film 1 is cited.

(3-6) Curl of polarizing plate

As described above, according to the present invention, the polarizing plate 2 can be corrected in the positive curling direction, whereby the reverse curl can be sufficiently suppressed when the blade body is formed. It is preferably a flat person having no curl or a polarizing plate 3 having a protective film attached with a positive curl. In the manufacturing method according to the present invention, when the polarizing plate 2 is formed into a blade body, reverse curling (curing in which the main surface side of the protective film 1 is superposed is convex) is formed (further, the film is curled and the MD is curled). Particularly advantageous.

In the above, one of the forms of the polarizing plate 2 which is likely to be reversely curled when the blade body is formed, and the first thermoplastic resin film 20 and the second thermoplastic resin film 30 have different equilibrium moisture ratios and/or moisture permeability. In other words, the polarizing plate 2 has a layer structure having an asymmetrical structure with respect to the polarizing film 10, and the reverse curl is likely to occur.

A structural example of the polarizing plate 2 which is likely to cause reverse curling is as follows. (a) A structure in which a thermoplastic resin film (protective film or the like) is bonded to only one surface of the polarizing film 10, (b) a protective film is bonded to one surface of the polarizing film 10, and a protective film is attached to the other surface. The structure of an optical film (such as a brightness enhancement film) other than the film, and (c) the structure of a thermoplastic resin film (protective film or the like) bonded to both surfaces of the polarizing film 10 (resin type, thickness, equilibrium moisture ratio, moisture permeability, The presence or absence of the surface treatment layer is different from each other, and (d) the adhesive layer for bonding the thermoplastic resin film (protective film or the like) on both surfaces of the polarizing film 10 is formed of different kinds of adhesives from each other. (e) a thermoplastic resin film (protective film) is bonded to both surfaces of the polarizing film 10 And the other structure of the optical film is bonded to one of the thermoplastic resin films, and (f) other, based on the polarizing film 10, the total of the film and the layer on one side thereof, and the other The total number of membranes and layers on one side is different.

(4) Other steps

The production method according to the present invention may further comprise the step of cutting the polarizing plate 3 with a protective film obtained by the above-described extrusion step to obtain a blade body of the polarizing plate 3 with a protective film. In the cutting, a generally available cutting device such as a shear cutter can be used.

Although the shape of the blade body is not particularly limited, it is usually a square shape, and a square shape having a long side and a short side is preferable, and a rectangular shape is more preferable. Although the blade body is usually cut in such a manner that a pair of opposing sides are parallel to the MD and the remaining opposing sides are parallel to the TD, the sides may be inclined from the MD or TD. The way to make a cut. The length of the long side and the short side of the blade body is not particularly limited, but usually the long side is 50 mm or more, and the short side is 30 mm or more. Curl is the larger the size of the blade body, the easier it is to produce. In the case where the size (long side and/or short side) is too small, the problem of curling is less likely to occur.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to these examples. Moreover, in the following examples, the equilibrium moisture content, the moisture permeability, the thickness, and the crimp amount were measured by the following methods.

(1) The equilibrium moisture rate of the membrane

A test piece having an MD length of 150 mm × TD and a length of 100 mm was cut out. The weight of the film after storage for 24 hours in an environment of a temperature of 23 ° C and a relative humidity of 55% was measured. Thereafter, drying treatment was performed at 105 ° C for 2 hours, and the weight of the film after the drying treatment was measured. The equilibrium moisture content was determined from the weight of the film before and after drying according to the following formula: equilibrium moisture ratio (% by weight) = {(film weight before drying treatment - film weight after drying treatment) / film weight before drying treatment} × 100

(2) The moisture permeability of the membrane

The moisture permeability [g/(m ² ‧24 hr)] at a temperature of 40 ° C and a relative humidity of 90% was measured in accordance with the weighing method defined in JIS Z 0208.

(3) Polarizer and film thickness

It was measured using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

(4) The polarizing plate with the protective film and the amount of curl of the polarizing plate

A rectangular test piece having an MD length of 300 mm × TD and a length of 200 mm was cut out from the obtained polarizing plate with a protective film, and left in an environment of a temperature of 25 ° C and a relative humidity of 55% for 24 hours. The test piece was placed on the reference surface (horizontal stage) with its concave surface facing upward, that is, in a state where the four end edges were lifted. In this state, the heights of the four corners of the test piece from the reference plane were measured, and the curl amount [mm] was determined as the height average of the four corners. When the amount of crimping is a positive value, it means that the side of the first thermoplastic resin film is concave (positive curl), and the case of negative value means that the side of the second thermoplastic resin film is concave (reverse curl).

(5) Clamping pressure of the bonding roller

A pressure sensitive paper [Prefilm Ultra Low Pressure (LLLW) manufactured by Fujifilm Co., Ltd.] is placed in a pressing portion between the bonding rolls, and is pressed, and then a pressure measuring system [Fuji Film Co., Ltd.] is used. FPD-305E and FPS-307 E], the clamping pressure at the extrusion was measured.

<Example 1>

(A) Production of polarizing film

While continuously transporting a long-length polyvinyl alcohol film (average degree of polymerization: about 2,400, degree of saponification: 99.9 mol% or more, thickness: 30 μm), it is uniaxially stretched by about 4 times in a dry manner, and further kept in tension. In the state, it was directly immersed in pure water of 40 ° C for 1 minute, and then immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.1/5/100 at 28 ° C for 60 seconds. Thereafter, it was immersed at 68 ° C for 300 seconds in an aqueous solution of potassium iodide / boric acid / water in a weight ratio of 10.5 / 7.5 / 100. The film was washed with pure water at 5 ° C for 5 seconds and then dried at 70 ° C for 180 seconds to obtain a long polarizing film in which iodine was adsorbed in the uniaxially stretched polyvinyl alcohol film. The thickness of the polarizing film was 11.1 μm.

(B) Production of polarizing plate

While continuously transporting the polarizing film obtained in the above (A), a long-shaped first thermoplastic resin film (a film of a "KC 2UAW" hard coat layer is formed on a TAC film manufactured by Konica Minolta Opto Co., Ltd.). Thickness: 32.4 μm, equilibrium moisture content: 1.9% by weight, moisture permeability: 455 g/(m ² ‧24 hr), and long-length second thermoplastic resin film [JSR (Rich)-based cyclic polyolefin resin film The product name "FEKB 015D3", thickness: 15.1 μm, equilibrium moisture content: 0.8% by weight, moisture permeability: 115 g / (m ² ‧ 24 hr)] is continuously transported between the polarizing film and the first thermoplastic resin film. And a water-based adhesive is injected between the polarizing film and the second thermoplastic resin film, and passes between the bonding rolls to obtain a first thermoplastic resin film/water-based adhesive layer/polarizing film/water-based adhesive layer/ A laminated film composed of a second thermoplastic resin film. The laminated film obtained was transported, and the water-based adhesive layer was dried by a heat-drying machine at 80 ° C for 300 seconds to obtain a polarizing plate. In the water-based adhesive, an aqueous solution obtained by dissolving the polyvinyl alcohol powder (trade name "Gohsefimer" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100] at 95 ° C is used. a cross-linking agent in a ratio of 1 part by weight based on 10 parts by weight of the polyvinyl alcohol powder in a polyvinyl alcohol aqueous solution having a concentration of 3 wt% obtained in hot water [glyoxylic acid manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) Aqueous solution obtained from sodium.

The thickness of the polarizing plate was 58.6 μm. The amount of curl of the polarizing plate was measured by the above method to be -10 mm (reverse curl).

(C) Production of polarizing plate with protective film

While continuously transporting the polarizing film obtained in the above (B), the long protective film is continuously conveyed [the base film is composed of polyethylene terephthalate and has thereon ( a protective film of a (meth)acrylic adhesive layer, having a total thickness of 57.3 μm], which is overlapped and passed between the bonding rolls, whereby the laminated body of the protective film and the polarizing plate is pressed up and down to produce an attached film. A polarizing plate with a protective film. The protective film is bonded to the surface of the first thermoplastic resin film (TAC film) of the polarizing plate through the adhesive layer.

In the above extrusion step, the surface speed V ₁ of the bonding roller in contact with the protective film is 11.76 [m/s], and the surface speed V ₂ of the bonding roller in contact with the polarizing plate is 12.00 [m/s]. The clamping pressure is 0.10 [MPa].

<Examples 2 to 6, Comparative Examples 1 to 3>

Except for the surface speed V _{1 of the} bonding roller that is in contact with the protective film in the pressing step, the surface speed V _{2 of the} bonding roller that is in contact with the polarizing plate, and the clamping pressure are as shown in Table 1, A polarizing plate with a protective film was produced in the same manner as in Example 1. The amount of curl of the polarizing plate with the protective film is shown in Table 1.

<Example 7>

The second thermoplastic resin film [Nippon ZEON Co., Ltd., a cyclic polyolefin resin film, trade name "ZF 14-023", thickness: 22.9 μm, equilibrium moisture content: 0.1% by weight, moisture permeability: 17 g/ (m ² ‧24 hr)], the surface speed V _{1 of the} bonding roller that is in contact with the protective film in the pressing step, the surface speed V _{2 of the} bonding roller that is in contact with the polarizing plate, and the clamping pressure are set as shown in Table 1. A polarizing plate with a protective film was produced in the same manner as in Example 1 except for the above. The amount of curl of the polarizing plate with the protective film is shown in Table 1.

1‧‧‧Protective film

2‧‧‧Polar plate

3‧‧‧Polarizer with protective film

5, 5'‧‧‧ affixing rolls

Claims (8)

A method for producing a polarizing plate, which is a method for producing a polarizing plate with a protective film, the method comprising the steps of: protecting a film in a single-layer layer of a polarizing plate, and passing between a pair of bonding rolls, thereby squeezing a surface speed V ₁ [m/s] of the bonding roller in contact with the protective film in the pair of bonding rolls, and a surface speed V _{2 of the} bonding roller in contact with the polarizing plate [m/ s] satisfies the relationship of the following formula (I): V ₁ <V ₂ (I) In the extrusion step, the pressure applied to the laminate including the polarizing plate and the protective film is 0.09 MPa or more. The manufacturing method according to claim 1, wherein when the polarizing plate is formed into a blade body, a curl is formed so that a side overlapping the protective film is convex. The manufacturing method according to the first aspect of the invention, wherein the polarizing plate comprises a polarizing film, a first thermoplastic resin film laminated on one surface thereof, and a second thermoplastic resin film laminated on the other surface. The manufacturing method according to the third aspect of the invention, wherein the first thermoplastic resin film has a higher equilibrium moisture content than the second thermoplastic resin film at a temperature of 23 ° C and a relative humidity of 55%. The manufacturing method according to the fourth aspect of the invention, wherein the first thermoplastic resin film and the second thermoplastic resin film have a difference in equilibrium moisture ratio of 0.5% by weight or more. The manufacturing method according to any one of claims 3 to 5, wherein the protective film is disposed in the first thermoplastic tree Lipid membrane side. The production method according to any one of claims 3 to 5, wherein the first thermoplastic resin film has an equilibrium moisture content of 1.5% by weight or more. The manufacturing method according to claim 1, wherein the polarizing plate has a thickness of 100 μm or less.