KR20140080356A

KR20140080356A - Method for preparing polarizing plate

Info

Publication number: KR20140080356A
Application number: KR1020120150058A
Authority: KR
Inventors: 김진숙; 김도원; 신직수
Original assignee: 제일모직주식회사
Priority date: 2012-12-20
Filing date: 2012-12-20
Publication date: 2014-06-30

Abstract

The present invention relates to a method for producing a polarizing plate in which polarizing properties are imparted to a polyvinyl alcohol film among a first laminate in which a polyvinyl alcohol film is laminated on both surfaces of a substrate and a first polarizer and a second polarizer are laminated on the other surface A first polarizer and a second polarizer are laminated on the first polarizer and the second polarizer, respectively, and a first optical film and a second optical film are laminated on each of the first polarizer and the second polarizer, A method for producing a third laminate in which a first polarizing plate including one optical film and a second polarizing plate including the second polarizing film and a second optical film are laminated, And separating the polarizing plate and the second polarizing plate, respectively, to produce two polarizing plates.

Description

METHOD FOR PREPARING POLARIZING PLATE [0002]

The present invention relates to a method for producing a polarizing plate. More specifically, the present invention relates to a method of producing a polarizing plate capable of producing two polarizing plates in a single step and minimizing the occurrence of curl of a laminate of a substrate and a polarizing plate during a polarizing plate manufacturing process.

Conventionally, a polarizing plate has a polyvinyl alcohol (PVA) resin film stretched in a predetermined direction and a dichroic polarizing material including an iodine compound is adsorbed and oriented. 2. Description of the Related Art Recently, a market for a slim liquid crystal display device such as a slim large wall-mounted TV, a mobile type computer, and the like is rapidly expanding. Accordingly, there is a demand for a thin film type polarizing plate which is made thin and light in order to thin the entire module of the liquid crystal display device. In addition, with the development of OLED technology, researches on flexible displays have been accelerated, and demand for low shrinkage thin film films is accelerating. However, since the polyvinyl alcohol film used in the polarizer is subjected to an elongation treatment, contraction in the stretching direction occurs after commercialization. Therefore, it is required to reduce the thickness to solve this problem.

As a method of producing a thin film polarizer, a method of producing a polarizer integrated with a substrate is most widely used. However, in the above method, there is a problem that the yield is lowered due to the problem of polarizing plate production such as curl by forming a protective film on one side only.

In order to produce a substrate-type thin film polarizing film by a conventional method, the PVA itself is reduced in thickness and laminated on a substrate and stretched. However, when the protective film is peeled off after the laminating process, the yield of the process is not high due to the problem of curling, and the productivity may be low.

An object of the present invention is to provide a process for producing a thin film polarizer excellent in productivity.

Another object of the present invention is to provide a method for producing a polarizing plate which prevents curl from occurring during the production of polarizing plate.

A polarizing plate manufacturing method of the present invention is a polarizing plate manufacturing method in which a polarizing property is imparted to a polyvinyl alcohol film among a first laminate in which a polyvinyl alcohol film is laminated on both surfaces of a substrate, A first polarizer and a second polarizer are laminated on the first polarizer and the second polarizer, and a first optical film and a second optical film are laminated on one side of each of the first polarizer and the second polarizer, A third laminate in which a first polarizer plate including the first polarizer and the first optical film and a second polarizer plate including the second polarizer and the second optical film are laminated is manufactured, And peeling the first polarizing plate and the second polarizing plate from the substrate to produce two polarizing plates.

The present invention provides a method of producing a polarizing plate capable of producing two polarizing plates in one step and minimizing curling.

1 is a conceptual view of a method of manufacturing a polarizing plate according to one embodiment of the present invention.

A polarizing plate manufacturing method of the present invention is a polarizing plate manufacturing method in which polarizing properties are imparted to a polyvinyl alcohol film of a first laminate in which a polyvinyl alcohol film is laminated on both surfaces of a substrate to produce a second laminate in which polarizers are laminated on both surfaces of the substrate ; Laminating an optical film on each of the surfaces of the polarizer, and producing a third laminate in which the polarizer and the polarizing plate including the optical film are laminated on both surfaces of the substrate; And peeling each of the polarizing plates from the substrate to produce two polarizing plates.

1, the present invention can produce a polarizing plate by using the first laminate 100. [ The first laminate 100 may be a laminate of polyvinyl alcohol films 110 and 115 on both sides of the substrate 105.

The substrate is a film made of a polypropylene (PP) resin, but not limited thereto. The thickness of the base material may be 50 占 퐉 to 200 占 퐉, preferably 70 占 퐉 to 120 占 퐉.

The polyvinyl alcohol-based film may be a commercially available product or one produced by a solvent casting method, a melt extrusion method, or the like. In the solvent casting method, a solution in which a resin is dissolved in a solvent is coated on a casting roll or a belt, and then the solvent is evaporated to produce a film. In the melt extrusion method, the resin is melted by raising the melting temperature or higher and then extruded and cooled in a cold roll to produce a film.

The first laminate may be produced by a solvent casting method. That is, a thin film polyvinyl alcohol-based film can be laminated on both sides of the substrate, or a polyvinyl alcohol-based resin can be applied to the substrate and dried to produce the first laminate as a substrate-integrated type. A thin film polarizing plate can be manufactured by preparing it as a monolithic substrate.

The 'integrated monolithic substrate' may mean that the polyvinyl alcohol-based film is laminated on the substrate. The first laminate may be a product in which a polyvinyl alcohol film is laminated on both surfaces of the substrate.

The first laminate 100 may be transported through the roll 10 and made into a second laminate 200 by a polarizer manufacturing process 20, though it is not limited. The second layered body 200 may have a first polarizer 205 and a second polarizer 210 stacked on both sides of the substrate 105.

The polarizer manufacturing process imparts a polarizing property to the polyvinyl alcohol-based film in the first laminate, and may include a process including dyeing, stretching, and the like. That is, the polyvinyl alcohol film can be made into the first polarizer and the second polarizer through the polarizer manufacturing process.

The polyvinyl alcohol film may be washed and swelled before dyeing. The washing process can remove foreign substances and the like present in the polyvinyl alcohol film. The swelling step is a step of swelling the subsequent dyeing step so as to smoothly proceed. That is, the polyvinyl alcohol film is passed through a swelling tank containing water or a chloride, boric acid, inorganic acid, organic solvent and the like. The temperature of the swelling bath can be maintained at a temperature of 20 to 40 캜. The manufacture and selection of the swelling bath can be easily carried out by a person having ordinary skill in the art to which the present invention belongs.

It can be dyed with a dichroic material which imparts a polarizing property to the swollen polyvinyl alcohol film. The dichroic material may be iodine or dichroic dye. In addition to iodine, the iodine dyeing vessel for dyeing with iodine molecules may further contain potassium iodide, and may further include boric acid. The iodine staining may be performed at a temperature of 20-40 < 0 > C. In the iodine dyeing tank, the concentration of iodine may be 0.1-0.5 wt%, the concentration of potassium iodide may be 0.5-1.5 wt%, and the concentration of boric acid may be 0-1 wt%.

After the dyeing process, the crosslinking process can be further roughened. That is, it is for strongly attaching the iodine molecule to the polyvinyl alcohol polymer matrix. The crosslinking agent may be boric acid, and may further contain phosphoric acid compounds and the like.

The dyed (stained) polyvinyl alcohol film may undergo a stretching process. As the stretching method, both dry stretching and wet stretching are possible. As the dry type softening method, an inter-roll stretching method, a compression stretching method, a heated roll stretching method, or the like can be used. It is also possible to carry out wet drawing after dry drawing.

The stretching bath for wet stretching may include boric acid. The temperature of the stretching bath may be in the range of 50-90 占 폚. The concentration of boric acid in the stretching tank may be 1-5% by weight.

The elongation can be made to be the same or different from that of the first polarizer and the second polarizer. In an embodiment, the difference in elongation between the first polarizer and the second polarizer may be 0-1%. In the above range, curling can be prevented in the step of drying after attaching the optical film.

In one embodiment, the elongation of the first polarizer can be 500-700%, and the elongation of the second polarizer can also be 500-700%.

The stretching process may be performed simultaneously with the dyeing process, or may be performed simultaneously with the crosslinking process. In the case of simultaneous with the dyeing step, it may be carried out in a solution containing iodine, and in the case of simultaneous with the cross-linking step, it may proceed in a solution containing boric acid.

After the stretching process, a boric acid treatment may be added. The boric acid treatment process may include a step of treating the first laminate in a solution containing 1-5% by weight of boric acid.

The polyvinyl alcohol film that has undergone the stretching process may undergo a complementary process for color correction. The complementary process can be carried out through a borohydrone containing potassium iodide and / or boric acid, but is not limited thereto. The complementary process may be carried out in a boron color bath containing 1-5% by weight of potassium iodide and 1-3% by weight of boric acid.

The polarizer produced therefrom is dried through a drying zone. During the drying process, the drying temperature, the retention path of the polarizer, and the air volume in the drying zone can be controlled. The drying temperature may be 50-100 ° C.

It is preferable that the difference in thickness between the first polarizer and the second polarizer is 0-3 탆. Within this range, curl can be prevented.

The thickness ratio of the first polarizer to the second polarizer is preferably 1: 1 to 1: 1.1. Within this range, curl can be prevented.

The thickness of each of the first polarizer and the second polarizer may be 3-100 占 퐉, preferably 3-20 占 퐉, more preferably 3-10 占 퐉.

Then, the third laminated body 400 can be manufactured by laminating the first optical film 405 and the second optical film 410 on each polarizer side of the second laminate.

The third laminate 400 includes a first polarizer 600 and a first polarizer 600 laminated on one surface of the base 105 and including a first polarizer 205 and a first optical film 405, And the second polarizer 500 including the second polarizer 210 and the second optical film 410 may be laminated on the other side of the first polarizer 210. [

The first optical film 405 and the second optical film 410 are supplied from the optical film feed rolls 40a and 40b to the first polarizer 205 and the second polarizer 210, Can be stacked.

The first optical film and the second optical film may include at least one of a protective film and a retardation film.

The protective film is a film having transparency, which is conventionally used as a protective film of a polarizer, and is not particularly limited. For example, the protective film may be a film of a cellulose, a polyester, a cyclic polyolefin, a polycarbonate, a polyether sulfone, a polysulfone, a polyamide, a polyimide, a polyolefin, a polyarylate, Based, polyvinyl chloride-based, and polyvinylidene chloride-based materials.

The retardation film can be used without limitation as long as it is a film having a? / 2 or? / 4 retardation function. For example, a film made of an olefinic, acrylic, cellulose, or a mixture thereof including a cycloolefin polymer (COP) can be used.

The ratio of the thickness of the first optical film to the thickness of the second optical film may be 1: 1 to 1: 1.5. In the above range, it can be used for a polarizing plate, and curling may not occur during drying after bonding an optical film.

The thickness of each of the first optical film and the second optical film may be 10 탆 to 100 탆. Within this range, it is possible to use a polarizing plate, to provide a thin film polarizing plate, and to prevent curling. Preferably 10 占 퐉 to 60 占 퐉.

The lamination of the optical film may be carried out by a conventional method using an adhesive layer. The lamination of the optical film by the adhesive layer can be performed by applying an adhesive or by laminating an adhesive film.

That is, as shown in Fig. 1, an adhesive can be applied to each of the polarizers from the adhesive supply tanks 30a and 30b. From this, the intermediate laminate 300 can be produced. The intermediate laminate 300 has a first polarizer 205 and a first adhesive layer 305 sequentially stacked on one surface of the base material 105 and a second polarizer 210 and a second adhesive material 2 adhesion layer 310 may be sequentially stacked.

Alternatively, an adhesive layer formed on the polarizer can be formed using an adhesive film formed on the release film.

The adhesive may include at least one of an aqueous adhesive and a pressure-sensitive adhesive. In an embodiment, an acrylic adhesive may be used.

Then, the third laminate 400 may be subjected to a pressing process by the rolls 50a and 50b for adhesion of the polarizer and the optical film.

Further, the third layered product may be subjected to a drying step (60) in order to increase the degree of adhesion between the polarizer and the optical film. The drying process is not limited, but may be carried out at 50-90 占 폚 for 1-5 minutes. In this range, curl may not occur.

The pressing and drying process may be performed at the same time or may be changed in order.

Further, before the drying step, the length of the first optical film and the length of the second optical film in the third laminate is set to be equal to the length of the first polarizer and the second polarizer, It is possible to further perform a step of cutting the end portion.

Then, the first polarizer plate 600 and the second polarizer plate 500 are peeled from the base material 105 in the third laminate body 400 to produce two polarizer plates.

The peeling can be carried out by both winding rolls.

And the length of the first optical film and the second optical film in the third laminate is equal to the length of the first polarizer and the second polarizer after the drying and the peeling, It is possible to further perform a step of cutting the end portion.

In order to prevent the wrinkles from being generated by applying pressure to the polarizing plate in the process of peeling the polarizing plate from the base material, the pressing may be performed by the rolls 70a and 70b at the time of separation.

The thickness of the first polarizing plate and the second polarizing plate may be 20-120 mu m. Within this range, it can be used as a polarizing plate of an optical display device including a liquid crystal display device.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Example

A laminate having a polyvinyl alcohol film laminated on both sides of a polypropylene substrate was immersed in a dyeing solution containing iodine and potassium iodide at 30 캜. The iodine content of the dyeing solution was 0.1 parts by weight based on 100 parts by weight of water, and the amount of potassium iodide was 1.5 parts by weight. And then uniaxially stretched at an elongation of 580% in an aqueous solution of boric acid at 55 ° C. The stretched laminated film was taken out from the aqueous solution of boric acid and dried by hot air at 60 캜. On each side of the polarizer, a triacetyl cellulose film having a thickness of 40 mu m was stacked on each polarizer side as a protective film using an acrylic adhesive as an aqueous adhesive. Dried at 70 DEG C for 3 minutes, and 2 polarizers were peeled off from the substrate.

Comparative Example

Except that a polyvinyl alcohol film was laminated on only one surface of the polypropylene base film in the above example, a polarizing plate was manufactured.

The curl was evaluated with respect to the laminate before the polarizing plate peeling in the above process. A laminate having a size of 100 mm x 150 mm (total thickness of embodiment: 115 mu m, comparative example: 70 mu m) was prepared at 25 DEG C, and the height of the four corners of the floor was measured. Curl means the maximum height at which the laminate is curved with respect to the bottom. The laminate according to the examples had a curl of 1-3 mm, whereas the laminate according to the comparative example had a curl of 10-30 mm, indicating that curl was low and two polarizers could be produced at the same time according to the present invention Respectively.

Claims

A polarizer is imparted to the polyvinyl alcohol film in a first laminate in which a polyvinyl alcohol film is laminated on both surfaces of a substrate, and a second polarizer is laminated on the other surface of the substrate, A laminate was prepared,
A first optical film and a second optical film are laminated on one surface of each of the first polarizer and the second polarizer, and a second polarizer and a second optical film are laminated on one surface of the substrate, Producing a third laminate in which a first polarizer, a second polarizer including the second polarizer and a second optical film are laminated, and
And peeling the first polarizing plate and the second polarizing plate from the substrate of the third laminate to produce two polarizing plates.

The method of manufacturing a polarizing plate according to claim 1, wherein the first laminate is an integrated laminate of the substrate and the polyvinyl alcohol film.

The method of manufacturing a polarizing plate according to claim 1, wherein the production of the second laminate comprises dyeing and stretching the first laminate.

4. The method of producing a polarizing plate according to claim 3, wherein the dyeing is carried out in a dyeing bath in which the first laminate is at a temperature of 20-40 DEG C and a concentration of iodine of 0.1-0.5 wt%.

The method of manufacturing a polarizing plate according to claim 1, wherein a difference in elongation between the first polarizer and the second polarizer is 0-1%.

The method of manufacturing a polarizing plate according to claim 3, further comprising boric acid treatment after the dyeing and stretching treatment.

The method of manufacturing a polarizing plate according to claim 1, wherein a ratio of the thickness of the first polarizer to the thickness of the second polarizer is 1: 1 to 1: 1.1.

The method of manufacturing a polarizing plate according to claim 1, wherein the lamination of the first optical film and the second optical film uses an adhesive.

The method of manufacturing a polarizing plate according to claim 8, wherein the adhesive comprises at least one of an aqueous adhesive and a pressure-sensitive adhesive.

The method of manufacturing a polarizing plate according to claim 1, wherein the first optical film and the second optical film include at least one of a protective film and a retardation film.

The method according to claim 10, wherein the protective film is at least one selected from the group consisting of cellulose, polyester, cyclic polyolefin, polycarbonate, polyether sulfone, polysulfone, polyamide, polyimide, polyolefin, A polyvinyl alcohol-based film, a polyvinyl chloride-based film, and a polyvinylidene chloride-based film.

The method of manufacturing a polarizing plate according to claim 1, wherein a ratio of the thickness of the first optical film to the thickness of the second optical film is 1: 1 to 1: 1.5.

The method of manufacturing a polarizing plate according to claim 1, further comprising a step of drying the third laminate at 50-90 DEG C for 1-5 minutes before peeling.