TW201713967A - Method for manufacturing polarizing plate - Google Patents

Abstract

The present invention provides a method for manufacturing polarizing plate which can suppress cracking of a polarizer accompanying a temperature change. The method for manufacturing polarizing plate comprises a coating step of forming a coating film 12a containing an active energy ray-curable resin on the surface of a film-like polarizer 8; and a curing step of irradiating the coating film 12a with the active energy ray L after 5 seconds or more since the coating film 12a was formed on the surface of the polarizer 8, and forming a resin layer 12b from the coating film 12a.

Description

Method for manufacturing polarizing plate

The present invention relates to a method of manufacturing a polarizing plate.

A polarizing plate is an optical component constituting a liquid crystal display device. The polarizing plate includes a film-shaped polarizer and a protective film which is then on one or both sides of the polarizer. For example, the polarizing plate described in the following Patent Document 1 includes a polarizer and a protective film which are bonded via a photocationically curable epoxy resin-based adhesive.

[Previous Technical Literature] [Patent Literature]

(Patent Document 1) Japanese Patent No. 5046735

In recent years, with the thinning of mobile communication devices such as smart phones, the polarizing plates used in mobile communication devices have been thinned. One of the methods for thinning a polarizing plate is to laminate a thinner protective layer on the polarizer to replace the conventional protective film. For example, a coating film containing an active energy ray-curable resin is formed, and the coating film is cured by irradiation with an active energy ray, that is, A thinner protective layer than a conventional protective film can be easily formed. It is also possible to form a thin protective layer from the succeeding active energy ray-curable resin itself which has been used in the polarizer and the protective film. However, the thinner the protective layer, the more easily the polarizer laminated with the protective layer is deformed and broken accompanying temperature changes (for example, thermal shock). When the active energy ray-curable resin as an adhesive is passed between the polarizer and the conventional protective film, the polarizing plate is broken along with the temperature change.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a polarizing plate which can suppress cracking of a polarizer with a change in temperature.

A method for producing a polarizing plate according to a first embodiment of the present invention, comprising: a coating step of forming a coating film containing an active energy ray-curable resin on a surface of a film-shaped polarizing film; and forming a coating on a surface of the polarizing film After the film has passed for 5 seconds or more, the coating film is irradiated with an active energy ray ray to form a resin layer hardening step.

A method for producing a polarizing plate according to a second embodiment of the present invention includes a coating step of forming a coating film containing an active energy ray-curable resin on a surface of a film-form substrate; and bonding the substrate through a coating film a bonding step on the surface of the film-shaped polarizer; and a hardening step of irradiating the coating film with an active energy ray ray to form a resin layer from the coating film after the substrate is bonded to the surface of the polarizer for 5 seconds or more .

A method for manufacturing a polarizing plate according to a second embodiment, which may further comprise: a peeling step of peeling the substrate from the resin layer after the hardening step Step.

In the coating step of the method for producing a polarizing plate according to the second embodiment, the coating film may be formed on the surface of the substrate which has not been subjected to the roughening treatment.

In the first embodiment or the second embodiment of the present invention, the resin layer may also be a protective layer for protecting the polarizer.

According to the present invention, it is possible to provide a method of producing a polarizing plate which can suppress cracking of a polarizer with a change in temperature.

1, 1a, 1b‧‧‧ coating device

2a, 2b‧‧‧ laminated body

3, 3a, 3b‧‧‧ illumination device

4, 34‧‧‧ protective film

5a, 5b, 5c, 5d, 5e, 5f‧‧‧ guide rolls

6‧‧‧ adhesive layer

7a, 7b, 7c, 7d ‧ ‧ rolls

8, 38‧‧‧ polarizers

9‧‧‧Cooling roller

12a, 32a, 52a, 54a‧ ‧ coating film

12b, 32b, 52b, 54b‧‧‧ resin layer (protective layer)

22a, 42a, 44a‧‧‧ substrate

22b‧‧‧Second layered body

24‧‧‧First laminate

26a‧‧‧The third layer

26b‧‧‧Fourth laminate

36‧‧‧ adhesive layer

42b, 44b, 46‧‧‧ laminated body

L‧‧‧Active energy ray

Fig. 1(a), Fig. 1(b) and Fig. 1(c) are schematic views showing a method of manufacturing a polarizing plate according to the first embodiment of the present invention.

Fig. 2 is a schematic view showing a method of manufacturing a polarizing plate according to a second embodiment of the present invention.

Fig. 3(a), Fig. 3(b) and Fig. 3(c) are schematic views showing a method of manufacturing a polarizing plate according to a second embodiment of the present invention.

Fig. 4 is a schematic view showing a method of manufacturing a polarizing plate according to a third embodiment of the present invention.

(a) and (b) of Fig. 5 are schematic views showing a method of manufacturing a polarizing plate according to a third embodiment of the present invention.

(Embodiment of the invention)

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings, the same structural elements are denoted by the same symbols. The present invention is not limited to the following embodiments.

(First embodiment)

The method for producing a polarizing plate according to the first embodiment of the present invention includes at least a coating step and a curing step. In the coating step, a coating film containing an active energy ray-curable resin is formed on the surface of the film-shaped polarizer. In the hardening step, after the coating film is formed on the surface of the polarizer, the active film dose is irradiated onto the coating film for 5 seconds or more, and a resin layer is formed from the coating film. Hereinafter, each step will be described in detail.

As shown in (a) and (b) of Fig. 1, in the coating step of the first embodiment, the layered body 2a is used. The laminate 2a includes a film-shaped polarizer 8 , an adhesive layer 6 laminated on the polarizer 8 , and a protective film 4 bonded to the polarizer 8 via the adhesive layer 6 .

The film-shaped polarizer 8 can be produced, for example, in the following order.

First, a film-shaped polyvinyl alcohol-based resin is extended in a uniaxial direction or a biaxial direction. Then, the polyvinyl alcohol-based resin is dyed with iodine or a dichroic dye. In order to crosslink the dyed polyvinyl alcohol-based resin, it is treated with a solution of a crosslinking agent (for example, an aqueous solution of boric acid). After the treatment with the crosslinking agent, the polyvinyl alcohol-based resin is washed with water and then dried. Through the above procedure, the polarizer 8 can be obtained. A polyvinyl alcohol-based resin can be obtained by saponifying a polyvinyl acetate-based resin. Polyacetate B The enester resin may be a polyvinyl acetate such as a homopolymer of vinyl acetate or a copolymer of vinyl acetate and another monomer (for example, an ethylene-vinyl acetate copolymer). Other monomers copolymerized with vinyl acetate may be, in addition to ethylene, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids or acrylamides having ammonium groups. The polyvinyl alcohol resin can also be modified. The modified polyvinyl alcohol-based resin may be, for example, polyvinyl formaldehyde modified with an aldehyde, polyvinyl acetal, or polyvinyl butyral.

The thickness of the polarizer 8 may be 10 μm or less or 8 μm or less. The thinner the polarizer 8, the thinner the polarizer becomes. The polarizer 8 may have a thickness of 2 μm or more. The thicker the polarizer 8, the easier it is to increase the mechanical strength of the polarizer 8.

The protective film 4 has a function of protecting the polarizer 8. The protective film 4 may be an optically transparent thermoplastic resin as long as it is a translucent thermoplastic resin. The resin constituting the protective film 4 may be, for example, a chain polyolefin resin, a cyclic polyolefin resin, a cellulose ester resin, a polyester resin, a polycarbonate resin, or a (meth)acrylic resin. A mixture or copolymer of a polystyrene resin, or the like.

The chain polyolefin resin may be, for example, a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin. The chain polyolefin resin may be a copolymer containing two or more kinds of chain polyolefins.

The cyclic polyolefin resin may be, for example, a ring-opening (co)polymer of a cyclic olefin or an addition polymer of a cyclic olefin. The cyclic polyolefin resin may be, for example, a copolymer of a cyclic olefin and a chain olefin (for example: none Copolymer). The chain olefin constituting the copolymer may be, for example, ethylene or propylene. The cyclic polyolefin resin may be a graft copolymer in which the above polymer is modified with an unsaturated carboxylic acid or a derivative thereof, or a hydrogenated product thereof. The cyclic polyolefin-based resin may be, for example, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer.

The cellulose ester-based resin may be, for example, cellulose triacetate (triethylenesulfonyl cellulose), cellulose diacetate, cellulose tripropionate or cellulose dipropionate. Copolymers thereof can also be used. A cellulose ester-based resin in which one of the hydroxyl groups is partially modified with another substituent may also be used.

A polyester resin other than the cellulose ester resin can also be used. The polyester resin may be, for example, a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. The polycarboxylic acid or a derivative thereof may be a dicarboxylic acid or a derivative thereof. The polycarboxylic acid or a derivative thereof may be, for example, terephthalic acid, isophthalic acid, dimethyl terephthalate or dimethyl naphthalene dicarboxylate. The polyol may be, for example, a diol. The polyol may be, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol or cyclohexane dimethanol.

The polyester resin may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, or polybutylene terephthalate. Ester, poly(butylene naphthalate), poly(cyclohexanedimethylene terephthalate) or cyclohexanedimethyl dimethyl naphthalate.

The polycarbonate resin is a polymer in which a polymerization unit (monomer) is bonded via a carbonate group. The polycarbonate resin may be a modified polycarbonate having a modified polymer skeleton or a copolymerized polycarbonate.

(meth)acrylic resin, for example, poly(methyl) Acrylate (for example: polymethyl methacrylate); methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth) acrylate copolymer; methyl methacrylate-acrylate - (meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (for example: MS resin); copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methacrylic acid) Methyl ester - cyclohexyl methacrylate copolymer, methyl methacrylate - methyl methacrylate copolymer, etc.).

The protective film 4 may contain at least one additive selected from the group consisting of a smoothing agent, a plasticizer, a dispersing agent, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.

The thickness of the protective film 4 may be 90 μm or less, 50 μm or less, or 30 μm or less. The thinner the protective film 4 is, the easier it is to reduce the thickness of the polarizing plate. The thickness of the protective film 4 may be 5 μm or more. The thicker the protective film 4, the easier it is to improve the mechanical strength and workability of the protective film 4.

The protective film 4 may also be an optically functional film such as a retardation film or a brightness enhancement film. For example, by stretching a film containing the above thermoplastic resin, forming a liquid crystal layer or the like on the film, a retardation film imparted with an arbitrary retardation value can be obtained.

The subsequent agent layer 6 may contain a water-based adhesive such as polyvinyl alcohol, or may contain an active energy ray-curable resin to be described later. The thickness of the cured adhesive layer 6 may be, for example, 0.05 μm or more and 10 μm or less. The thicker the layer 6 is, the more difficult it is to form bubbles between the polarizer 8 and the protective film 4, and the polarizer 8 and the protective film 4 are easily and firmly adhered. The thinner the layer 6 is, the easier it is to reduce the thickness of the polarizing plate.

As shown in (a) and (b) of Fig. 1, in the coating step, the laminated body 2a is conveyed in the direction d2. Then, as shown in (a) and (c) of the first embodiment, the coating device 1 is used to form a coating film 12a containing an active energy ray-curable resin on the surface of the polarizing plate 8 of the laminated body 2a. In other words, the coating film 12a is formed on the surface of the laminated body 2a on the side of the polarizer 8 to obtain the laminated body 2b. The coating device 1 may be a gravure coater such as a Micro Chamber Doctor. The coating film 12a can be formed only of an active energy ray curable resin.

The active energy ray-curable resin is a resin that can be cured by irradiation with an active energy ray. The active energy ray may be, for example, ultraviolet light, visible light, electron rays or X-rays. The active energy ray curable resin may be an ultraviolet curable resin. The ultraviolet curable resin can be prepared as a solventless type of adhesive. Therefore, when the active energy ray-curable resin is an ultraviolet curable resin, the drying step for removing the solvent may not be performed after the coating step or the irradiation step. Further, the ultraviolet curable resin is more easily used in combination with a water-based adhesive than a protective film having a low moisture permeability.

The active energy ray-curable resin may be a single resin or may contain a plurality of resins. For example, the active energy ray-curable resin may contain a cationically polymerizable curable compound or a radically polymerizable curable compound. The active energy ray-curable resin may contain a cationic polymerization initiator or a radical polymerization initiator which starts the curing reaction of the curable compound.

The cationically polymerizable curable compound may be, for example, an epoxy compound (a compound having at least one epoxy group in the molecule), or An oxetane compound (a compound having at least one oxetane ring in the molecule). The radically polymerizable curable compound may be, for example, a (meth)acrylic compound (a compound having at least one (meth)acryloxy group in the molecule). The radically polymerizable curable compound may be a vinyl compound having a radical polymerizable double bond.

The active energy ray-curable resin may also contain a cationic polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, an adhesive, a thermoplastic resin, a filler, a flow regulator, a plasticizer, or a consumer. A foaming agent, an antistatic agent, a leveling agent or a solvent.

In the hardening step, the coating film 12a is irradiated with the active energy ray L after the coating film 12a is formed on the surface of the polarizer 8 for 5 seconds or more, and then the irradiation device 3 is used. The coating film 12a is cured by irradiation of the active energy ray L to form the resin layer 12b. Hereinafter, the time from when the coating film 12a is formed on the surface of the polarizer 8 to the time when the coating film 12 is irradiated with the active energy ray L at a is set as the elapsed time T1. That is, the elapsed time T1 is 5 seconds or longer.

By adjusting the elapsed time T1 to 5 seconds or longer, the unhardened coating film 12a can be bleed on the surface of the polarizing plate 8 without spots, and the unhardened coating film 12a can be sufficiently adhered to the surface of the polarizing plate 8. After the uncured coating film 12a is sufficiently adhered to the surface of the polarizer 8, the resin film 12b firmly adhered to the polarizer 8 can be obtained by irradiating the coating film 12a with the active energy ray L. Since the resin layer 12b is firmly adhered to the polarizer 8, even if the polarizer 8 is subjected to a sharp temperature change (thermal shock), the deformation of the polarizer 8 due to temperature change (for example, expansion and contraction) can be suppressed by the resin layer 12b. ). because Thereby, it is possible to suppress the polarizer 8 from being broken due to a temperature change.

The elapsed time T1 may be, for example, 7 seconds or longer. From the viewpoint of productivity, the elapsed time T1 is preferably, for example, 300 seconds or less, 250 seconds or less, or 240 seconds or less. The longer the elapsed time T1, the easier it is to suppress the crack of the polarizer 8. The shorter the elapsed time T1, the shorter the time required for the hardening step, and the productivity of the polarizing plate can be improved. The elapsed time T1 can be adjusted by the distance between the coating device 1 and the irradiation device 3. The elapsed time T1 can also be adjusted via the conveying speed of the laminated body 2b.

The illuminating device 3 can be, for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a fluorescent lamp, a black light lamp, a microwave excited mercury lamp or a metal halide lamp.

In the hardening step, the coating film 12a is directly or indirectly irradiated with the active energy ray L. For example, as shown in (a) of Fig. 1, the active energy ray L is directly irradiated on the surface of the coating film 12a. When the active energy ray L can penetrate the protective film 4 and the polarizer 8, the active energy ray L can also be irradiated to the coating film 12a from the side of the protective film 4. In other words, the irradiation device 3 can be disposed on the side of the protective film 4, and the active energy ray L can be irradiated to the coating film 12a via the protective film 4 and the polarizing plate 8. The active energy ray L may be irradiated to the coating film 12a from the side of the coating film 12a and the side of the protective film 4. That is, the active energy ray L can be irradiated onto both sides (front and bottom) of the coating film 12a.

The surface temperature of the coating film 12a before the irradiation of the active energy ray L to the coating film 12a can be adjusted, for example, to 20 ° C or more and 140 ° C or less, or 20 ° C or more and 80 ° C or less. When the temperature of the surface of the coating film 12a is within such a temperature range, the coating film 12a is easily adhered to the polarizing plate 8, and the polarizing film is easily suppressed. The breakdown of 8 The surface temperature of the coating film 12a may also be referred to as the temperature around the coating film 12a or the temperature of the environment.

The polarizing plate (layered body 2b) produced in the above-described steps is provided with a resin layer 12b, a polarizer 8 directly laminated on the resin layer 12b, and a direct superimposing polarized light, as shown in (c) of Fig. 1 . The adhesive layer 6 of the sheet 8 and the protective film 4 of the polarizer 8 are bonded via the adhesive layer 6. As described above, even if the polarizer 8 of the polarizing plate is subjected to a sharp temperature change (thermal shock), deformation of the polarizer 8 due to temperature change can be suppressed by the resin layer 12b. Therefore, cracking of the polarizer 8 with a change in temperature can be suppressed.

The resin layer 12b may be a protective layer that protects the polarizer 8. The resin layer 12b may also be an optical compensation layer. The polarizing plate (layered body 2b) may have another optical layer laminated on the protective film 4 or the resin layer 12b. Other optical layers may be, for example, a reflective polarizing film, a film with an anti-glare function, a film with a surface reflection preventing function, a reflective film, a semi-transmissive reflective film, a viewing angle compensation film, a hard coat layer, an adhesive layer, and a touch. Control the sensing layer, antistatic layer or antifouling layer.

(Second embodiment)

The method for producing a polarizing plate according to the second embodiment of the present invention is the same as that of the first embodiment except for the matters described below. As in the first embodiment, the second embodiment can also suppress cracking of the polarizing plate with a change in temperature. Hereinafter, the description of common items in the first embodiment and the second embodiment will be omitted.

The method for producing a polarizing plate according to the second embodiment includes at least an application step, a bonding step, and a curing step. In the coating step of the second embodiment, a coating film containing an active energy ray-curable resin is formed on the surface of a film-form substrate. In the bonding step of the second embodiment, the substrate is bonded to the surface of the film-shaped polarizer via a coating film. In the hardening step of the second embodiment, after the substrate is bonded to the surface of the polarizer for 5 seconds, the coating film is irradiated with an active energy ray, and a resin layer is formed from the coating film. Hereinafter, each step will be described in detail.

As shown in (a) of Fig. 2 and Fig. 3, in the coating step of the second embodiment, the first layered body 24 is used. The first layered body 24 includes a film-shaped polarizer 38, an adhesive layer 36 laminated on the polarizer 38, and a protective film 34 bonded to the polarizer 8 via the adhesive layer 36. The first layered body 24 of the second embodiment can be the same as the layered body 2a of the first embodiment. That is, the polarizer 38 of the second embodiment can be the same as the polarizer 8 of the first embodiment. The adhesive layer 36 of the second embodiment can be the same as the adhesive layer 6 of the first embodiment. The protective film 34 of the second embodiment can be the same as the protective film 4 of the first embodiment.

As shown in Fig. 2 and Fig. 3(a), in the second embodiment, the first layered body 24 is conveyed in the direction d24 and supplied between a pair of bonding rolls (rollers 7a and 7b). . The guide roller 5a is in contact with the surface of the protective film 34 having the first laminate 24.

As shown in FIG. 2 and FIG. 3(a), in the coating step of the second embodiment, the coating device 1 is used to form an active energy ray-curable resin on the surface of the film-form substrate 22a. Coating film 32a. also That is, in the coating step, the second layered body 22b including the base material 22a and the coating film 32a formed on the surface of the base material 22a is produced. The composition of the coating film 32a of the second embodiment can be the same as that of the coating film 12a of the first embodiment. The base material 22a of the second embodiment can be the same film as the protective film 4 of the first embodiment.

As shown in Fig. 2 and Fig. 3(a), in the second embodiment, the second layered body 22b is conveyed in the direction d22 and supplied between the pair of rolls 7a and 7b. The guide roller 5b is in contact with the surface of the substrate 22a having the second laminate 22b.

As shown in Fig. 2 and Fig. 3, in the bonding step of the second embodiment, the coating film 32a of the second layered body 22b is opposed to the polarizing plate 38 of the first layered body 24, and the first layered body 24 is placed. And the second laminate is superposed. The superposed first laminate body 24 and the second laminate body 22b are sandwiched by a pair of rolls 7a and 7b. In other words, the base material 22a is bonded to the surface of the polarizer 38 via the coating film 32a using a pair of bonding rolls. As a result, the third layered body 26a having the base material 22a, the coating film 32a laminated on the substrate 22a, the polarizing plate 38 laminated on the coating film 32a, and the polarizing film 38 superimposed thereon can be obtained. The agent layer 36 and the protective film 34 laminated on the adhesive layer 36.

As shown in Fig. 2, in the hardening step of the second embodiment, the third layered body 26a is conveyed in the direction d26 between the pair of rolls 7a and 7b. Then, after the substrate 22a is bonded to the surface of the polarizer 38 for 5 seconds or more, the active energy ray L is applied to the coating film 32a by using the irradiation device 3. That is, the coating film 32a can be cured into the resin layer 32b by irradiation with the active energy ray L. Hereinafter, it will pass through the coating film 32a. The elapsed time T2 is obtained when the base material 22a is bonded to the surface of the polarizer 38 and the active energy ray L is irradiated onto the coating film 32a.

The elapsed time T2 of the second embodiment corresponds to the elapsed time T1 of the first embodiment. The elapsed time T2 may be 7 seconds or more, and may be 300 seconds or less, 250 seconds or less, or 240 seconds or less. The elapsed time T2 can be adjusted by the distance between the rollers 7a and 7b and the irradiation device 3. The elapsed time T2 can also be adjusted by the transfer speed of the third layered body 26a.

As shown in Fig. 2, in the hardening step, the active energy ray L is irradiated onto the coating film 32a from the side of the substrate 22a. That is, the active energy ray L can be irradiated to the coating film 32a via the substrate 22a. The active energy ray L can also be irradiated to the coating film 32a from the side of the protective film 34. In other words, the irradiation device 3 is disposed on the side of the protective film 34, and the active energy ray L is irradiated to the coating film 32a via the protective film 34 and the polarizer 38. The active energy ray L may be irradiated onto the coating film 32a from the side of the substrate 22a and the side of the protective film 34.

In the second embodiment, the peeling step can be performed after the hardening step. As shown in (b) and (c) of Fig. 2 and Fig. 3, in the peeling step, the base material 22a is peeled off from the resin layer 32b of the third layered body 26a. In the peeling step, the guide roller 5c is in contact with the substrate 22a having the third laminate 26a. The fourth layered body 26b of the peeled base material 22a is conveyed in the direction d26.

When the peeling step is performed, the polarizing plate completed in the second embodiment does not have the substrate 22a. In other words, as shown in FIG. 3(c), the polarizing plate (fourth laminate 26b) which has been subjected to the peeling step includes a resin layer 32b, a polarizer 38 which is directly laminated on the resin layer 32b, And the protective film 34 adhered to the polarizer 38 via the adhesive layer 36. The polarizing plate (the fourth laminated body 26b) may be the same as the polarizing plate (the laminated body 2b) of the first embodiment.

When the peeling step is performed, in the coating step, the coating film 32a may be formed on the surface of the substrate 22a which has not been subjected to the roughening treatment. When the base material 22a is subjected to the roughening treatment, the coating film 32a is easily adhered to the surface of the base material 22a, so that the base material 22a is difficult to peel off from the coating film 32a (resin layer 32b) after curing. Therefore, when the peeling step is performed, the coating film 32a is formed on the surface of the base material 22a which is not subjected to the roughening treatment, and in the peeling step, the base material 22a is easily peeled off from the resin layer 32b. The roughening treatment may be, for example, a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, or a flame treatment.

In the second embodiment, the peeling step may not be performed. When the peeling step is not performed, the surface of the substrate 22a may be subjected to a roughening treatment before the coating step. In the subsequent coating step, the coating film 32a may be formed on the surface of the roughened substrate 22a. As a result, the base material 22a becomes difficult to be peeled off by the resin layer 32b. When the peeling step is not performed, the polarizing plate completed in the second embodiment is provided with the substrate 22a. The base material 22a also functions as a film for protecting the polarizing plate 38. The thickness of the polarizing plate including the resin layer 32b and the base material 22a is thicker than the polarizing plate of the peeled base material 22a. However, the polarizing plate not only includes the resin layer 32b but also the base material 22a, and it is easy to suppress cracking of the polarizer 38 with temperature change. That is, the thick substrate 22a helps to suppress cracking of the polarizer 38. The polarizing plate provided with the substrate 22a may have other layers laminated on the substrate 22a Optical layer.

(Third embodiment)

The method for producing a polarizing plate according to the third embodiment of the present invention is the same as the first embodiment and the second embodiment except for the matters described below. The third embodiment is similar to the first embodiment and the second embodiment in that cracking of the polarizer with temperature changes can be suppressed. Hereinafter, the description of the common matters in the first embodiment, the second embodiment, and the third embodiment will be omitted.

The method for producing a polarizing plate according to the third embodiment includes at least an application step, a bonding step, and a curing step, as in the second embodiment. However, in the coating step of the third embodiment, a coating film is formed on each surface of a pair of substrates. In the bonding step of the third embodiment, the film-shaped polarizer is disposed between a pair of substrates. Further, a pair of substrates are bonded to both sides of the polarizer via a coating film. In the hardening step of the third embodiment, after a pair of substrates are bonded to both sides of the polarizer, the active film dose is irradiated to the coating film for 5 seconds, and a resin layer is formed from the coating film. These steps are detailed below.

As shown in Fig. 4 and Fig. 5(a), in the coating step of the third embodiment, the active energy ray-curable resin is formed on the surface of the film-form substrate 44a by using the coating device 1a. The coating film 54a is formed into a laminated body 44b. The laminated body 44b of the third embodiment may be the same as the second laminated body 22b of the second embodiment. In the coating step, the coating film 52a containing the active energy ray-curable resin is formed on the surface of the film-form substrate 42a by using the coating device 1b, and the layered body 42b is produced. Third implementation The laminated body 42b of the form can be the same as the second laminated body 22b of the second embodiment. The composition of the coating film 54a of the laminated body 44b can be the same as that of the coating film 52a of the laminated body 42b. The composition of the coating film 54a of the laminated body 44b may be different from the coating film 52a of the laminated body 42b. The composition of the base material 44a of the laminated body 44b can be the same as that of the base material 42a of the laminated body 42b. The composition of the base material 44a of the laminated body 44b may be different from the base material 42a of the laminated body 42b.

As shown in Fig. 4, in the third embodiment, the laminated body 44b is conveyed in the direction d44 and supplied between a pair of bonding rolls (rollers 7c and 7d). The guide roller 5d is in contact with the surface of the substrate 44a having the laminated body 44b. Further, the laminated body 42b is conveyed in the direction d42 and supplied between the rollers 7c and 7d. The guide roller 5e is in contact with the surface of the substrate 42a having the laminated body 42b. Further, a film-shaped polarizer 38 is supplied between the rolls 7c and 7d.

As shown in Fig. 4 and Fig. 5, in the bonding step of the third embodiment, the polarizer 38 is sandwiched between the pair of laminated bodies 44b and 42b. The coating film 54a of the laminated body 44b is opposed to one surface of the polarizing plate 38. The coating film 52a of the laminate 42b faces the other surface of the polarizer 38. Then, the laminated body 44b, the polarizer 38, and the laminated body 42b are laminated, and sandwiched by a pair of rolls 7c and 7d. As a result, as shown in FIG. 5(b), the base material 44a is bonded to one surface of the polarizer 38 via the coating film 54a, and the base material 42a is attached to the polarizer 38 via the coating film 52a. a surface. That is, in the bonding step, the laminated body 46 having the base material 42a, the coating film 52a laminated on the base material 42a, the polarizing plate 38 laminated on the coating film 52a, and the polarizing film are laminated. a coating film 54a of 38 and a substrate laminated on the coating film 54a 44a.

As shown in Fig. 4, in the hardening step of the third embodiment, the laminated body 46 is conveyed between the pair of rollers 7c and 7d in the direction d46. Then, after the base materials 42a and 44a are bonded to the surface of the polarizer 38, the active energy ray L is applied to the coating films 52a and 54a by using the irradiation device 3a. That is, the coating films 52a and 54a are cured by irradiation of the active energy ray L. Then, after the laminated body 46a is conveyed via the guide roller 5f, the coating film 52a and 54a are irradiated with the active energy ray L again using the irradiation device 3b. The hardening of each coating film is promoted by the irradiation of the second active energy ray L. By the above hardening step, the resin layer 52b can be formed from the coating film 52a, and the resin layer 54b can be formed from the coating film 54a. In the following, the time from when the base materials 42a and 44a are bonded to the surface of the polarizer 38 via the coating films 52a and 54a, and immediately after the application of the active energy rays L to the coating films 52a and 54a is made is made. After time T3.

The elapsed time T3 of the third embodiment corresponds to the elapsed time T2 of the second embodiment. The elapsed time T3 may be 7 seconds or longer, or may be 300 seconds or less, 250 seconds or less, or 240 seconds or less. The elapsed time T3 can be adjusted by the distance between the rollers 7c and 7d and the irradiation device 3a. The elapsed time T3 can also be adjusted by the conveying speed of the laminated body 46.

In the hardening step of the third embodiment, the active energy ray L is applied to the coating films 52a and 54a from the side of the base material 44a in a state where the surface of the substrate 42a on the side of the base material 42a is brought into contact with the cooling roll 9. That is, the active energy ray L is irradiated to the coating films 52a and 54a via the substrate 44a.

In a modification of the third embodiment, the active energy can also be The measuring line L is irradiated to the coating film 52a by the side of the base material 42a of the laminated body 46. In other words, the irradiation device 3a can be disposed on the side of the base material 42a of the laminated body 46, and the active energy ray L can be applied to the coating films 52a and 54a via the base material 42a. The active energy ray L may be irradiated to the coating films 52a and 54a from both sides of the layered body 46.

In the third embodiment, the peeling step may be performed after the hardening step. For example, in the peeling step, the base material 42a can be peeled off from the resin layer 52b of the laminated body 46. The base material 44a may be peeled off from the resin layer 54b of the laminated body 46.

When the peeling step is performed, the polarizing plate completed in the third embodiment does not include the base material 42a or 44a. For example, the polarizing plate which has been subjected to the peeling step may have at least the resin layer 52b, the polarizing plate 38 directly laminated on the resin layer 52b, and the other resin layer 54b directly laminated on the polarizing plate 38. The polarizing plate may have other optical layers laminated on the resin layer 52b or 54b.

When the peeling step is performed, the substrates 42a and 44a which have not been subjected to the roughening treatment can be used in the coating step.

In the third embodiment, only one of the base materials 42a or 44a may be peeled off in the peeling step. When only one of the base materials 42a or 44a is peeled off, the substrate which is not peeled off may be used as long as the substrate which has not been subjected to the roughening treatment is used in the coating step. In the third embodiment, the peeling step may not be performed. When the peeling step is not performed, the substrate subjected to the roughening treatment may be used in the coating step. When the stripping step is not performed, the polarizing plate completed in the third embodiment may be (b) in FIG. The laminate body 46 shown is itself. The polarizing plate may have another optical layer laminated on the substrate 42a or 44a.

(Example)

Hereinafter, the contents of the present invention will be described in more detail by way of examples and comparative examples, but the invention is not limited by the following examples.

[Example 1]

(1) Undercoat layer forming step

The polyvinyl alcohol powder was dissolved in hot water at 95 ° C to prepare a 3 wt% aqueous solution of polyvinyl alcohol. As the polyvinyl alcohol powder, "Z-200" (average degree of polymerization 1100, saponification degree: 99.5 mol%) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. was used. The crosslinking agent is mixed in an aqueous solution of polyvinyl alcohol. The amount of the crosslinking agent added was adjusted to 5 parts by weight based on 6 parts by weight of the polyvinyl alcohol powder. As the crosslinking agent, "Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd. can be used. By the above steps, a coating liquid for forming an undercoat layer (coating liquid 1) was obtained.

As the base film, an unstretched polypropylene film (melting point: 163 ° C) having a thickness of 90 μm was prepared. Corona treatment was applied to one side of the substrate film. The coating liquid 1 was applied on the surface of the substrate film subjected to corona treatment using a small gravure coater. The undercoat layer was formed by drying the coating liquid 1 coated on the substrate film at 80 ° C for 10 minutes. The thickness of the undercoat layer was 0.2 μm.

(2) Production of laminated film (resin layer forming step)

The polyvinyl alcohol powder was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%. As the polyvinyl alcohol powder, "PVA 124" (average degree of polymerization 2400, degree of saponification 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd. was used. This polyvinyl alcohol aqueous solution is used as a coating liquid (coating liquid 2) for forming a polyvinyl alcohol-based resin layer.

The coating liquid 2 was applied to the surface of the undercoat layer formed on the base film using a nozzle coater. A polyvinyl alcohol-based resin layer was formed on the undercoat layer by drying the coating liquid 2 applied on the surface of the undercoat layer at 80 ° C for 20 minutes. By the above steps, a laminated film made of a base film, an undercoat layer laminated on the base film, and a polyvinyl alcohol-based resin layer laminated on the undercoat layer is obtained.

(3) Production of stretch film (extension step)

The free end uniaxial extension of the 5.3-fold laminated film was carried out at 160 ° C to obtain a stretched film. In the extension of the laminated film, a longitudinal uniaxial stretching device of a floating type is used. The thickness of the stretched polyvinyl alcohol-based resin layer was 5.0 μm.

(4) Production of polarizing laminated film (dyeing step)

The stretched film was immersed in an aqueous solution (dyeing solution) of iodine and potassium iodide for about 180 seconds to carry out a dyeing treatment of the polyvinyl alcohol-based resin layer. The temperature of the staining solution was adjusted to 30 °C. The weight of iodine in the dyeing liquid was adjusted to 0.6 parts by weight per 100 parts by weight of water. Adjust the weight of potassium iodide in the dye solution to 100% The water by weight is 10 parts by weight. After the dyeing treatment, the remaining amount of the dyeing liquid was washed away from the polyvinyl alcohol-based resin layer using pure water at 10 °C.

Then, in the first crosslinking treatment, the stretched film was immersed in an aqueous solution containing boric acid (first cross-linking liquid) for 120 seconds. The temperature of the first cross-linking liquid was adjusted to 78 °C. The weight of boric acid in the first cross-linking liquid was adjusted to 9.5 parts by weight per 100 parts by weight of water.

Then, in the second crosslinking treatment, the stretched film was immersed in an aqueous solution (second cross-linking liquid) containing boric acid and potassium iodide for 60 seconds. The temperature of the second cross-linking liquid was adjusted to 70 °C. The weight of boric acid in the second cross-linking liquid was adjusted to 9.5 parts by weight per 100 parts by weight of water. The weight of potassium iodide in the second cross-linking liquid was adjusted to 4 parts by weight per 100 parts by weight of water.

After the second crosslinking treatment, the stretched film was washed with pure water at 10 ° C for 10 seconds. The stretched film after washing was dried at 40 ° C for 300 seconds.

By the above steps, a polarizing laminated film made of a base film and a film-shaped polarizer laminated on the base film can be obtained. Further, the thickness of the film-shaped polarizer was 5.0 μm.

(5) Production of polarizer with protective film

As the first protective film, a film containing triethylenesulfonyl cellulose is prepared. The thickness of the first protective film was 25 μm. The first protective film is disposed on the outer side (the side opposite to the display lattice) when the polarizing plate is placed on the display lattice.

The surface of the first protective film is subjected to corona treatment. Applying ultraviolet curability to the surface of the first protective film subjected to corona treatment The agent forms a first adhesive layer. As the ultraviolet curable adhesive, "KR-70T" manufactured by ADEKA Corporation was used. The application of the ultraviolet curable adhesive is a small gravure coater.

The first protective film is bonded to the surface of the polarizer having the polarizing laminated film via the first adhesive layer. For the bonding of the first protective film, a pair of bonding rolls can be used.

Next, the first adhesive layer is cured by irradiating the ultraviolet ray from the side of the polarizing laminate film to the first adhesive layer using a high pressure mercury lamp. The thickness of the first adhesive layer after hardening was 1.2 μm. The cumulative amount of ultraviolet light was adjusted to 200 mJ/cm ² .

By the above steps, a first protective layer comprising a base film, a polarizer laminated on the base film, a first adhesive layer laminated on the polarizer, and a first adhesive layer adhered to the polarizer are obtained. A laminate formed by a film. By peeling the base film from the laminated body, the protective layer formed by the polarizer, the first adhesive layer laminated on the polarizer, and the first protective film bonded to the polarizer via the first adhesive layer is obtained. Film polarizer.

(6) Production of polarizing plate

(coating step)

In order to form a protective layer, it is prepared as an epoxy resin of an ultraviolet curable resin. The protective layer is disposed on the display lattice side when the polarizing plate is placed on the display lattice. As the epoxy resin, "KR-25T" manufactured by ADEKA Corporation is used. The epoxy resin is applied to the surface of the polarizer constituting the polarizer having the protective film by using a gravure coater. Form a film.

(hardening step)

When a coating film was formed on the surface of the polarizer, the coating film was irradiated with ultraviolet rays using a high-pressure mercury lamp for 7 seconds. The coating film was exposed to an ultraviolet ray at 25 ° C. The coating film is cured by irradiation of ultraviolet rays to form a resin layer. The cumulative amount of ultraviolet light irradiated by the coating film was adjusted to 200 mJ/cm ² . The thickness of the resin layer was 3.5 μm.

Through the above steps, the polarizing plate of the first embodiment is provided, which comprises a resin layer, a polarizer laminated on the resin layer, a first adhesive layer, and a first protection bonded to the polarizer via the first adhesive layer. membrane.

(7) Thermal shock test (temperature cycle test)

The polarizing plate of Example 1 was cut first to prepare 50 samples. The size of the sample was 50 mm x 50 mm. An adhesive is attached to the surface of the first protective film of each sample. Each sample was bonded to a glass plate via an adhesive. The glass plate was placed in a test tank. After cooling the test vessel and maintaining the temperature in the test vessel at -40 ° C for 30 minutes, the test vessel was heated to maintain the temperature in the test vessel at 85 ° C for 30 minutes. After the cooling and heating cycle operation was repeated 100 times, the glass plate was taken out from the test tank. The number of samples having polarizers that were broken by repeated cycle operations was counted. The ratio (breakage generation rate) of the sample having the cracked polarizer in 50 samples was calculated. The rupture generation rate of Example 1 is shown in Table 1 below.

[Examples 2, 3]

In the examples 2 and 3, the time from the formation of the coating film on the surface of the polarizing plate to the time when the coating film was irradiated with ultraviolet rays (elapsed time) was adjusted to the time shown in Table 1 below. Each of the polarizing plates of Examples 2 and 3 was produced in the same manner as in Example 1 except for the elapsed time. Each of the thermal shock tests of Examples 2 and 3 was carried out in the same manner as in Example 1. The respective rupture generation rates of Examples 2 and 3 were calculated in the same manner as in Example 1. The respective rupture generation rates of Examples 2 and 3 are shown in Table 1 below.

[Comparative Example 1]

In the coating step of Comparative Example 1, a coating film containing an epoxy resin was formed on the surface of the film-form transfer substrate. Then, the transfer substrate is bonded to the surface of the polarizer constituting the polarizer having the protective film via the coating film.

In the hardening step of Comparative Example 1, when the transfer substrate was bonded to the surface of the polarizer via the coating film, the high pressure mercury lamp was used to irradiate the coating film with ultraviolet rays for 2 seconds.

A polarizing plate of Comparative Example 1 was produced in the same manner as in Example 1 except for the above steps. The thermal shock test of Comparative Example 1 was carried out in the same manner as in Example 1. The crack generation rate of Comparative Example 1 was calculated in the same manner as in Example 1. The rupture generation rate of Comparative Example 1 is shown in Table 1 below.

(industrial availability)

According to the present invention, it is possible to manufacture a polarizing plate which can suppress cracking of a polarizer with a change in temperature.

1‧‧‧ Coating device

2a, 2b‧‧‧ laminated body

3‧‧‧Irrigation device

4‧‧‧Protective film

6‧‧‧ adhesive layer

8‧‧‧ polarizer

12a‧‧·coating film

12b‧‧‧Resin layer (protective layer)

Claims (5)

A method for producing a polarizing plate, comprising: a coating step of forming a coating film containing an active energy ray-curable resin on a surface of a film-shaped polarizing film; and forming the coating film on a surface of the polarizing film after 5 seconds or more A step of hardening the coating film with an active energy ray to form a resin layer from the coating film. A method for producing a polarizing plate, comprising: a coating step of forming a coating film containing an active energy ray-curable resin on a surface of a film-form substrate; and bonding the substrate to the film-shaped polarizer via the coating film And a step of curing the resin layer by applying the active energy ray to the coating film after the substrate is bonded to the surface of the polarizer for 5 seconds or more. The method for producing a polarizing plate according to claim 2, further comprising: a peeling step of peeling off the substrate from the resin layer after the curing step. The method for producing a polarizing plate according to the second or third aspect of the invention, wherein the coating step is performed by forming the coating film on a surface of the substrate on which the roughening treatment is not performed. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the resin layer is a protective layer for protecting the polarizer.