KR20170039191A - Method for producing laminate - Google Patents

Abstract

A laminate capable of forming a polarizing film having uniform performance is provided. The method for producing a laminate of the present invention comprises the steps of heating the resin base material 11 to a glass transition temperature (Tg) of -15 ° C or higher of the resin base material 11 and heating the polyvinyl alcohol-based resin layer 12 are formed in this order.

Description

[0001] METHOD FOR PRODUCING LAMINATE [0002]

The present invention relates to a method for producing a laminate. More specifically, the present invention relates to a method for producing a laminate having a resin substrate and a polyvinyl alcohol (PVA) resin layer formed on the resin substrate.

There has been proposed a method in which a PVA resin layer is applied and formed on a resin substrate, and the laminate is stretched and stained to obtain a polarizing film (for example, refer to Patent Document 1 and Patent Document 2). From such a method, attention can be paid to the fact that a thin polarizing film can be obtained, for example, contributing to the thinning of an image display apparatus. However, in this case, there is a problem that the irregularity easily occurs in the performance (specifically, the film thickness optical property, appearance) of the obtained polarizing film.

Prior art literature

Patent Document 1: Japanese Patent Application Laid-Open No. 51-69644

Patent Document 2: Japanese Patent Application Laid-Open No. 2001-343521

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and its main object is to provide a laminate capable of producing a polarizing film having uniform performance.

The method for producing a laminate of the present invention comprises the steps of heating a resin substrate to a glass transition temperature (Tg) of -15 ° C or higher of the resin substrate and forming a polyvinyl alcohol-based resin layer on the resin substrate in this order .

In one embodiment, the resin base material is withdrawn from the resin base roll in which the elongated resin base material is rolled up, and the heating step is performed.

In one embodiment, the heating step is performed after being stored in the wound state.

In one embodiment, the step of winding, the step of heating, and the step of forming the polyvinyl alcohol-based resin layer are successively performed.

In one embodiment, the heating process is performed at a glass transition temperature (Tg) of the resin base + 15 DEG C or less.

In one embodiment, the heating step is performed while conveying the resin base material with a conveying roll installed in a heating furnace.

In one embodiment, the holding angle of the transport roll in the heating furnace is 90 DEG or more.

In one embodiment, the center-to-center distance of the transport rolls in the heating furnace is 2 m or less.

In one embodiment, the heating step is performed while the resin base material is transported with a tenter.

In one embodiment, the shrinkage percentage of the resin substrate by the heating is 3% or less.

In one embodiment, the resin substrate is formed of a polyethylene terephthalate resin.

In one embodiment, the resin substrate is preliminarily stretched.

In one embodiment, the polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin on the resin substrate by die coating and drying.

According to another aspect of the present invention, a method for manufacturing a polarizing film is provided. The method for producing the polarizing film uses a laminate obtained by the above-mentioned production method.

In one embodiment, it includes a step of stretching the laminate.

According to yet another aspect of the present invention, a method of manufacturing a polarizing plate is provided. The polarizing plate manufacturing method includes a step of laminating a protective film on the polarizing film obtained by the above manufacturing method.

According to yet another aspect of the present invention, a drawn laminate is provided. This oriented laminate has a resin substrate and a polyvinyl alcohol-based resin layer formed on the resin substrate. The film thickness irregularity of the polyvinyl alcohol-based resin layer within a size of 200 mm (MD) x 200 mm (TD) was 0.25 탆 or less, and the film thickness of the polyvinyl alcohol-based resin layer was 200 mm (MD) TD) is 0.50 or less.

According to yet another aspect of the present invention, an apparatus for producing a laminate is provided.

In one embodiment, the manufacturing apparatus includes an unwinding means for unwinding the resin base material from a resin base roll wound in a roll shape, and a transport roll for transporting the resin base material in a long shape, A heating furnace for heating the resin base material to a glass transition temperature (Tg) of -15 ° C or higher of the resin base material; and a coating means for applying a coating liquid containing a polyvinyl alcohol-based resin on the heated resin base material.

In one embodiment, the resin substrate is heated while being conveyed in a conveying roll provided in the heating furnace.

In one embodiment, the angle of the conveying roll in the heating furnace is 90 DEG or more.

In one embodiment, the center-to-center distance of the transport rolls in the heating furnace is 2 m or less.

In one embodiment, the manufacturing apparatus includes a winding means for winding the resin base material from a resin base roll wound in a roll shape, and a tenter for holding and conveying both ends of the long base resin base material Heating means for heating the resin base material held at both ends with a clip of the tenter to a glass transition temperature (Tg) of the resin base material at a temperature not lower than -15 ° C, and a polyvinyl alcohol-based resin And an application unit for applying the application liquid.

In one embodiment, the resin substrate is heated while conveying the resin substrate with the tenter.

According to the present invention, it is possible to alleviate (uniformize) the surface unevenness of the resin base material (for example, the gage band generated when the resin base material is wound) by subjecting the resin base material to heat treatment at a predetermined temperature or more. As a result, a PVA resin layer having excellent thickness uniformity can be formed on the resin substrate. By applying various treatments to the PVA resin layer having excellent thickness uniformity, it is possible to obtain a polarizing film (for example, a liquid crystal display panel having excellent transparency) without fluctuation in performance (specifically, Satisfying the required quality sufficiently) can be produced.

1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention.
2 (a) and 2 (b) are schematic views for explaining a heating method of a resin substrate according to an embodiment.
3 is a schematic view for explaining a heating method of a resin substrate according to another embodiment.
4 is a schematic diagram showing an example of the present invention.
5 is a schematic view for explaining a method for evaluating the appearance of the PVA resin layer.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Laminate

1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 10 can be obtained by forming a polyvinyl alcohol (PVA) resin layer 12 on a resin substrate 11. [

A-1. Resin substrate

Typically, the resin base material has a long shape. The thickness of the resin base material is preferably 20 mu m to 300 mu m, more preferably 50 mu m to 200 mu m.

As the material for forming the resin substrate, for example, an ester resin such as a polyethylene terephthalate resin, a cycloolefin resin, an olefin resin such as polypropylene, a (meth) acrylic resin, a polyamide resin, a polycarbonate resin , And the like. Preferably, a polyethylene terephthalate resin can be used. Among them, an amorphous polyethylene terephthalate resin can be preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as the dicarboxylic acid and a copolymer further containing cyclohexanedimethanol as the glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 170 占 폚 or less. By using such a resin base material, the laminate can be stretched at a temperature at which the crystallization of the PVA-based resin does not progress rapidly, and troubles due to the crystallization (for example, the orientation of the PVA-based resin layer by stretching is prevented) . On the other hand, the glass transition temperature of the resin substrate is preferably 60 DEG C or more. The glass transition temperature (Tg) is a value that can be obtained in accordance with JIS K 7121.

The resin substrate is molded by any suitable method. Examples of the molding method include a melt extrusion method, a solution casting method (solution casting method), a calendering method, and a compression molding method. Of these, the melt extrusion method is preferable.

The surface of the resin substrate may be subjected to surface modification treatment (e.g., corona treatment or the like) or may be formed with an easy adhesive layer. By such a treatment, the adhesion between the resin base material and the PVA-based resin layer can be improved. The surface modification treatment and / or the formation of the reverse adhesion layer may be performed before or after the heat treatment described later. When stretching described later is carried out, it may be carried out before the stretching or after stretching.

In one embodiment, the resin base material is stretched before the heat treatment to be described later. As the stretching method of the resin base material, any appropriate method can be employed. Specifically, it may be a fixed-end drawing or a free-end drawing. It may be simultaneous biaxial stretching or sequential biaxial stretching. The resin base material may be stretched in one step or in multiple steps. In the case of multi-stage operation, the drawing magnification of the resin substrate described later is the product of the drawing magnifications of the respective steps. The stretching method is not particularly limited, and may be a pneumatic stretching method or an underwater stretching method.

The resin base material stretching direction can be appropriately set. For example, the elongated resin base material is stretched in the width direction. Specifically, the resin base material is transported in the longitudinal direction and stretched in the direction (TD) perpendicular to the transport direction (MD). In the present specification, the term " orthogonal " includes the case where the orthogonal direction is substantially orthogonal. Here, " substantially orthogonal " includes the case of 90 DEG +/- 5.0 DEG, preferably 90 DEG +/- 3.0 DEG, more preferably 90 DEG +/- 1.0 DEG. The resin base material can be effectively used by stretching the resin base material in the transverse direction (TD). In addition, the thickness of the resin base material in the TD can be made uniform, and partial film thickness fluctuation, which will be described later, can be suppressed.

The drawing temperature of the resin base material can be set to any appropriate value in accordance with the forming material of the resin base material, the drawing method, and the like. The stretching temperature is typically from Tg-10 deg. C to Tg + 80 deg. C with respect to the glass transition temperature (Tg) of the resin substrate. When a polyethylene terephthalate resin is used as the material for forming the resin substrate, the drawing temperature is preferably 70 占 폚 to 150 占 폚, more preferably 90 占 폚 to 130 占 폚.

The stretch magnification of the resin base material is preferably 1.5 times or more the original length of the resin base material. By setting this range, it is possible to satisfactorily suppress partial film thickness fluctuation, which will be described later. On the other hand, the draw ratio of the resin base material is preferably 3.0 times or less with respect to the original length of the resin base material. By setting this range, the occurrence of wrinkles in the heating step to be described later can be satisfactorily suppressed.

A-2. Winding and Storage

In one embodiment, the elongated resin substrate is wound in a roll shape. There is a partial change in film thickness at the time of molding the resin substrate, and winding up in this state may cause irregularities in the resin substrate. The winding tension is typically 60 N / m to 150 N / m (unit: N / m is the tension per unit width length). The wound resin substrate (resin base roll) can be stored (left) in a wound state for an arbitrary suitable period until it is used in the next step. For example, if the PVA resin layer is not continuously formed after molding of the resin base material, the resin base material is kept in a wound state. When the storage period is prolonged (for example, 3 days or more), the occurrence of unevenness (the degree of irregularity, the number of irregularities generated) becomes conspicuous, and the film thickness variation tends to occur in the PVA resin layer (laminate) . Therefore, the longer the storage period of the resin base roll, the more remarkable the effect of the heat treatment to be described later can be obtained. The resin base roll may also be stored under any suitable atmosphere. The storage temperature is, for example, 15 占 폚 to 35 占 폚. The relative humidity is, for example, 40% RH to 80% RH.

A-3. heating

The resin base material is heated. Specifically, the resin base material is heated by hot air, an infrared heater, a roll heater, or the like. The heating temperature is a glass transition temperature (Tg) of the resin base of -15 ° C or higher, preferably Tg-10 ° C or higher, more preferably Tg-5 ° C or higher. When a polyethylene terephthalate resin is used as the resin base material, the heating temperature is preferably 68 占 폚 or higher. By heating the resin substrate at such a temperature, the surface irregularities of the resin substrate can be alleviated (uniform). As a result, a PVA-based resin layer to be described later can be formed well, and a PVA-based resin layer having excellent thickness uniformity can be formed. On the other hand, the heating temperature is preferably (Tg) + 15 deg. C or less, more preferably Tg + 10 deg. When a polyethylene terephthalate resin is used as the material for forming the resin substrate, the heating temperature is preferably 80 DEG C or less. By heating the resin base material at this temperature, occurrence of wrinkles (thermal creases) can be suppressed well.

The heating time is preferably 70 seconds to 150 seconds, more preferably 75 seconds to 100 seconds.

The resin substrate can be shrunk by heating. For example, when the resin substrate is stretched in the width direction before heating, the resin substrate may shrink (TD shrink) in the width direction by heating. The shrinkage ratio (TD shrinkage ratio) of the resin substrate is preferably 3% or less, more preferably 2% or less, particularly preferably 1.5% or less. In such a range, generation of wrinkles is suppressed and excellent appearance can be obtained. The TD shrinkage ratio is calculated by the following formula.

TD shrinkage ratio (%) = {1- (width of resin base after heating (W ₁ ) / width of resin base before heating (W ₀ )) × 100

In one embodiment, the resin substrate is heated while being conveyed. As described above, when the resin base material is rolled up, it is preferable to heat the resin base material wound from the resin base roll. Examples of the heating method include a method of transporting a resin substrate by a transport roll provided in a heating furnace, and a method of heating while transporting a resin substrate by a tenter. According to the former, it is possible to suppress the enlargement of the facility. According to the latter, the generation of wrinkles can be suppressed very well.

2 (a) and 2 (b) show specific examples of the case where the transport roll is used. In the illustrated example, the resin base material 11 is heated by conveying the resin base material 11 in its longitudinal direction by the pre-rolls R2 to R5 provided in the oven furnace A. From the viewpoint of production speed, it is preferable to install four or more pre rolls in the oven furnace as shown in the drawing.

The inclination of the pre-roll in the oven is preferably 90 DEG or more. In the example shown in Fig. 2 (a), the angle of inclination of the pre-rolls R2 and R5 is 90 degrees, and the angle of inclination of the pre-rolls R3 and R4 is 180 degrees. In the example shown in Fig. 2 (b), the angle of inclination of the pre-rolls R2 to R5 is 90 degrees. By such a grazing angle, shrinkage of the resin base material can be suppressed and occurrence of wrinkles can be suppressed. The term "envelope" as used herein means a straight line connecting the center point of the pre-roll and the point of contact between the resin base material and the pre-roll when viewed in a section perpendicular to the axial direction, and a straight line connecting the center point of the pre- The angle formed by the straight line connecting the contact end point. The pre-roll interval in the oven furnace (center-to-center distance of the roll) is preferably 2 m or less. In addition, it is preferable that the two pre-roll intervals (between R1 and R2 and between R5 and R6 in the illustrated example) installed so as to extend over the entrance to the oven are 2 m or less. With such an interval, shrinkage of the resin substrate is suppressed, and occurrence of wrinkles can be suppressed. In addition, in the present embodiment, shrinkage of the resin base material may also be related to the drawing magnification and heating temperature of the resin base material.

A specific example of the case of using a tenter is shown in Fig. In the illustrated example, both ends (on a line perpendicular to the conveying direction) of the resin base material 11 are gripped by the left and right clips 21 and 21 of the tenter, respectively, and the heating zone is conveyed at a predetermined speed in the longitudinal direction thereof, The substrate 11 is heated. The distance between the clips in the transport direction (the distance between adjacent clips) is preferably 20 mm or less, more preferably 10 mm or less. The clip width is preferably 20 mm or more, and more preferably 30 mm or more. In the present embodiment, the TD shrinkage of the resin base can be controlled by, for example, adjusting the distance between the left and right clips. Specifically, when the distance between the left and right clips is changed without changing the distance, the TD shrinkage ratio is substantially 0%. On the contrary, by stretching the distance between the left and right clips, the resin base material can be stretched in TD. The TD change rate of the resin base material is preferably 1.00 times or more, more preferably 1.00 times to 1.10 times. The TD change rate is calculated by the following equation.

TD change ratio (times) = width of resin substrate after heating (W ₁ ) / width of resin substrate before heating (W ₀ )

A-4. Formation of PVA resin layer

As the PVA-based resin forming the PVA-based resin layer, any suitable resin can be employed. Examples thereof include polyvinyl alcohol and ethylene vinyl alcohol copolymer. The polyvinyl alcohol can be obtained by subjecting the polyvinyl acetate to exposure. The ethylene vinyl alcohol copolymer can be obtained by subjecting the ethylene vinyl acetate copolymer to an impression. The degree of saponification of the PVA resin is usually from 85 mol% to 100 mol%, preferably from 95.0 mol% to 99.95 mol%, and more preferably from 99.0 mol% to 99.93 mol%. The degree of sensitization can be obtained according to JIS K 6726-1994. By using the PVA-based resin having such degree of impression, a polarizing film having excellent durability can be obtained. If the degree of impurity is excessively high, gelatinization may occur.

The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be obtained according to JIS K 6726-1994.

The PVA-based resin layer is preferably formed by applying a coating liquid containing a PVA-based resin on a resin substrate and drying the coating liquid. The coating liquid is typically a solution prepared by dissolving the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolitone, various glycols, polyhydric alcohols such as trimethylolpropane, amines such as ethylenediamine and diethylenetriamine Can be used. These may be used singly or in combination of two or more. Of these, water is preferred. The concentration of the PVA resin in the solution is preferably 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. If such a resin concentration is used, a uniform coating film adhered to the resin base material can be formed.

The coating liquid may contain an additive. Examples of additives include plasticizers, surfactants, and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These are used for further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer. As an additive, for example, an adherent component may be mentioned. Adhesion between the resin base material and the PVA resin layer can be improved by using the reverse adhesive component. As a result, troubles such as peeling of the PVA resin layer in the resin base can be suppressed, and dyeing and underwater stretching described later can be satisfactorily performed. As the reverse adhesive component, for example, modified PVA such as acetoacetyl modified PVA can be used.

Any suitable method may be employed as the coating method of the coating liquid. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (coma coating method)

In one embodiment, a die coating method is employed. In the die coating method, since the gap between the resin base material and the die (e.g., fountain die, slot die) is kept constant, the coating liquid is applied, so that a coating film having excellent thickness uniformity can be obtained. On the other hand, when unevenness is generated in the resin base material, the distance between the resin base material and the die lips is not uniform, and it becomes difficult to form a uniform coating film. Therefore, when the die coating method is employed, the effect of the heat treatment can be remarkably obtained.

The above-mentioned coating liquid is applied so that the thickness of the dried PVA resin layer is preferably 3 탆 to 40 탆, more preferably 3 탆 to 20 탆. The coating and drying temperature of the coating liquid is preferably 50 DEG C or more.

Preferably, the PVA resin layer is continuously formed after the heating. For example, a PVA resin layer is formed on a resin substrate without winding the resin substrate after heating. This is because the effect of the heating can be obtained well.

In addition, an undercoat layer (primer layer) may be previously formed on the side of the resin-based PVA resin layer before forming the PVA resin layer. The material constituting the primer layer is not particularly limited as long as it is a material exhibiting a strong adhesion to the resin base material and the PVA resin layer to some extent. For example, a thermoplastic resin having excellent transparency, thermal stability, stretchability and the like can be used. Examples of the thermoplastic resin include an acrylic resin, a polyolefin resin, a polyester resin, a polyvinyl alcohol resin or a mixture thereof.

A-5. Other

In one embodiment, the resin substrate is taken out from the resin base roll (unwinding step), the resin substrate is heated (heating step), and the PVA resin layer is formed (PVA resin layer forming step). According to this embodiment, the effect of the heat treatment can be satisfactorily obtained. As a specific example of this embodiment, there is a form in which the heating and the PVA resin layer forming step are sequentially performed by winding up a series of lines for conveying the resin substrate having a long shape as shown in Fig. 4 includes an unwinding roll 40 for winding a resin substrate 11 from a resin base roll 30, a heating device 50 for heating the resin base material 11, A coating apparatus 60 for applying a coating liquid containing the PVA resin to the surface of the base material 11, a drying apparatus 70 for drying the applied coating liquid and a take-up roll 80 are provided. In addition, the laminate manufacturing apparatus 100 is provided with a plurality of conveying rolls 90.

B. Stretch laminate

The oriented laminate of the present invention is produced by stretching the above-mentioned laminate. In one embodiment, the oriented laminate is produced by stretching the above laminate to a drawing magnification of 1.5 times or more and 3.0 times or less by a pneumatic drawing method. The details of the stretching method of the laminate will be described later. The film thickness variation within the size of 200 mm (MD) x 200 mm (TD) of the PVA resin layer in the drawn laminate is preferably 0.25 탆 or less, more preferably 0.20 탆 or less. In the stretched laminate, the PVA resin layer has a fluctuation in the slow axis within a size of 200 mm (MD) x 200 mm (TD), preferably 0.50 deg. Or less, more preferably 0.30 deg. Or less, particularly preferably 0.25 deg. to be.

C. polarizer film

The polarizing film of the present invention is produced by carrying out a treatment for converting the PVA resin layer of the laminate into a polarizing film.

Examples of the treatment for forming the polarizing film include a dyeing treatment, a stretching treatment, an insolubilizing treatment, a crosslinking treatment, a washing treatment, and a drying treatment. These processes can be appropriately selected according to the purpose. Also, the processing order, the processing timing, and the number of processing can be appropriately set. Each process will be described below.

(Dyeing treatment)

The dyeing treatment is typically performed by staining the PVA resin layer with a dichroic material. Preferably by adsorbing a dichroic substance to the PVA-based resin layer. Examples of the adsorption method include a method of immersing a PVA resin layer (laminate) in a dyeing solution containing a dichroic substance, a method of coating the PVA resin layer with the dye solution, a method of spraying the dye solution onto the PVA resin layer And the like. Preferably, the laminate is immersed in the dyeing solution. This is because the dichroic material can be adsorbed well.

Examples of the dichroic material include iodine and organic dyes. These may be used alone or in combination of two or more. The dichroic material is preferably iodine. When iodine is used as the dichroic substance, the dyeing solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.05 to 5.0 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to an aqueous solution of iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Of these, potassium iodide is preferable. The compounding amount of iodide is preferably 0.3 to 15 parts by weight based on 100 parts by weight of water.

The temperature of the liquid during dyeing of the staining solution is preferably 20 ° C to 40 ° C. When the PVA resin layer is immersed in the dyeing solution, the immersion time is preferably 10 seconds to 300 seconds. Under such conditions, the dichroic material can be sufficiently adsorbed to the PVA resin layer. The dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or the simple transmittance of the finally obtained polarizing film is in a predetermined range. In one embodiment, the immersion time is set so that the obtained degree of polarization of the polarizing film is 99.98% or more. In another embodiment, the immersion time is set so that the obtained polarizing film has a simple transmittance of about 40%.

(Drawing process)

Any suitable method may be employed for the laminate stretching method. Specifically, it may be a fixed-end stretching (for example, a method using a tenter stretcher) or a free-end stretching (for example, a method of uniaxially stretching between rolls different in circumferential speed). Further, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or biaxial stretching may be sequentially performed. The stretching of the laminate may be performed in one step or in multiple steps. In the case of multi-stage operation, the draw ratio (maximum draw ratio) of the laminate to be described later is the product of the draw ratio at each step.

The stretching treatment may be an in-water stretching method in which the laminate is immersed in a stretching bath, or a pneumatic stretching method. Preferably, the underwater stretching treatment is carried out at least once, and more preferably the underwater stretching treatment and the pneumatic stretching treatment are combined. According to the underwater stretching, the resin substrate or the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 캜), and the PVA resin layer can be stretched at a high magnification while suppressing its crystallization. As a result, a polarizing film having excellent optical characteristics (for example, polarization degree) can be produced.

Any suitable direction can be selected in the laminate elongation direction. In one embodiment, the elongated laminate is stretched in the longitudinal direction. Specifically, the laminate is transported in the longitudinal direction and its transport direction (MD). In another embodiment, the elongated laminate is stretched in the width direction. Specifically, it is the direction (TD) in which the stack is transported in the longitudinal direction and is perpendicular to the transport direction (MD).

The drawing temperature of the laminate can be set to any appropriate value in accordance with the forming material of the resin base material, the drawing method, and the like. In the case of adopting a pneumatic drawing method, the drawing temperature is preferably not less than the glass transition temperature (Tg) of the resin base, more preferably not less than the glass transition temperature (Tg) of the resin base + 10 DEG C or more, 15 ° C or higher. On the other hand, the stretching temperature of the laminate is preferably 170 占 폚 or less. By such stretching at such a temperature, rapid progress of crystallization of the PVA-based resin can be suppressed, and troubles due to the crystallization (for example, the orientation of the PVA-based resin layer due to stretching can be prevented) can be suppressed.

When an underwater stretching method is employed as the stretching method, the liquid temperature of the stretching bath is preferably 40 ° C to 85 ° C, more preferably 50 ° C to 85 ° C. With such a temperature, stretching can be performed at a high magnification while suppressing the dissolution of the PVA-based resin layer. Concretely, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60 ° C or more in relation to the formation of the PVA-based resin layer. In this case, when the stretching temperature is lower than 40 캜, there is a possibility that the stretching can not be performed satisfactorily even considering the plasticization of the resin substrate by the water. On the other hand, as the temperature of the drawing bath becomes higher, the solubility of the PVA resin layer becomes higher, and there is a possibility that excellent optical characteristics can not be obtained.

When the underwater stretching method is adopted, it is preferable to immerse the laminate in an aqueous boric acid solution to stretch it (stretching in boric acid in water). By using an aqueous boric acid solution as the drawing bath, the PVA-based resin layer can be provided with rigidity for enduring the tension required for drawing and water resistance not dissolving in water. Specifically, the boric acid can be crosslinked by hydrogen bonding with the PVA resin by generating a tetrahydroxyboric acid anion in an aqueous solution. As a result, the PVA resin layer can be stiffened and water-resistance imparted to the PVA resin layer, and a polarizing film having excellent optical characteristics can be produced.

The aqueous solution of boric acid is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight based on 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent can also be used.

Preferably, iodide is added to the drawing bath (boric acid aqueous solution). By combining iodide, the elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of the iodide are as described above. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of water.

The immersing time of the laminate in the drawing bath is preferably 15 seconds to 5 minutes.

The elongation percentage (maximum draw ratio) of the laminate is typically at least 4.0 times, and preferably at least 5.0 times, the original length of the laminate. Such a high stretching magnification can be achieved, for example, by adopting an in-water stretching method (boric acid in-water stretching). In the present specification, the "maximum draw ratio" means the draw ratio immediately before the laminate breaks, and refers to a value smaller than the value obtained by confirming the draw ratio at which the laminate breaks.

Preferably, the underwater stretching treatment is carried out after the dyeing treatment.

(Insolubilization treatment)

The insolubilization treatment is typically performed by immersing a PVA-based resin layer in an aqueous solution of boric acid. In particular, in the case of adopting an underwater stretching method, water resistance can be imparted to the PVA resin layer by performing the insolubilization treatment. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight based on 100 parts by weight of water. The liquid temperature of the insoluble base (aqueous solution of boric acid) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization treatment is carried out after the production of the laminate, before the dyeing treatment or underwater stretching treatment.

(Crosslinking treatment)

The crosslinking treatment is typically performed by immersing a PVA-based resin layer in an aqueous solution of boric acid. By subjecting the PVA resin layer to crosslinking treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight based on 100 parts by weight of water. When the cross-linking treatment is performed after the dyeing treatment, it is more preferable to blend iodide. By combining iodide, the elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 to 5 parts by weight based on 100 parts by weight of water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the crosslinking treatment is carried out before the underwater stretching treatment. In a preferred embodiment, dyeing treatment, crosslinking treatment and underwater stretching treatment are carried out in this order.

(Cleaning treatment)

The cleaning treatment is typically performed by immersing the PVA resin layer in an aqueous solution of potassium iodide.

(Dry treatment)

The drying temperature in the drying treatment is preferably 30 ° C to 100 ° C.

The obtained polarizing film is substantially a PVA-based resin film in which a dichroic substance is adsorbed and oriented. The thickness of the polarizing film is preferably 15 占 퐉 or less, more preferably 10 占 퐉 or less, further preferably 7 占 퐉 or less, particularly preferably 5 占 퐉 or less. Such a polarizing film can suppress the occurrence of cracks or the like in an environmental test (for example, an environmental test at 80 캜). On the other hand, the thickness of the polarizing film is preferably 0.5 탆 or more, and more preferably 1.0 탆 or more. Such a polarizing film can be very excellent in transportability at the time of production and the like.

The polarizing film preferably exhibits absorption dichroism at a wavelength within a wavelength range of 380 nm to 780 nm. It is preferable that the polarizing film has a polarization degree of 99.9% or more at a single transmittance of 42% or more.

D. Polarizer

The polarizing plate of the present invention has the polarizing film. Preferably, the polarizing plate has the polarizing film and a protective film disposed on at least one of the polarizing film. As the protective film, the resin base material may be used as it is or a film separate from the resin base material may be used. Examples of the material for forming the protective film include cellulose resins such as (meth) acrylic resin, diacetylcellulose and triacetylcellulose, olefinic resins such as cycloolefin resins and polypropylene, and ester resins such as polyethylene terephthalate resins Resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. The thickness of the protective film is preferably 10 mu m to 100 mu m.

As described above, in one embodiment, the resin base material can be used as a protective film without peeling from the polarizing film. In another embodiment, the resin substrate is peeled off from the polarizing film and another film is laminated. The protective film may be laminated to the polarizing film through the adhesive layer or may be laminated (without passing through the adhesive layer). The adhesive layer is typically formed of an adhesive or a pressure-sensitive adhesive. According to the present invention, since a polarizing film having an excellent thickness uniformity can be obtained, it is possible to favorably laminate the protective film to the polarizing film.

[Example]

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

[Example 1-1]

(Preparation of laminate)

A resin substrate made of amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) having a water absorption rate of 0.75% and a glass transition temperature (Tg) of 75 캜 and TD-elongated TD stretched 2.0 times at 115 캜 in advance and having a thickness of 100 탆 was stretched at a tension of 100 N / m in a rolled resin base material roll and kept at 25 DEG C and 60% relative humidity for 30 days.

Thereafter, the resin base material was taken out from the resin base roll, and heat treatment was carried out at 70 DEG C for 60 seconds while conveying the resin base material.

Then, one surface of the resin substrate was subjected to corona treatment. (Polymerization degree: 4200, degree of saponification: 99.2 mol%) and acetoacetyl modified PVA (degree of polymerization: 1200, degree of acetoacetyl modification: 4.6%, degree of saponification: 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., (GOHSEFIMER Z200) " at a ratio of 9: 1 was applied by a die coating method at 25 DEG C and then dried at 60 DEG C for 200 seconds to form a PVA resin layer having a thickness of 10 mu m, .

(Preparation of polarizing film)

The resulting laminate was subjected to free-end uniaxial stretching in an oven at 115 DEG C in 2.0 times the longitudinal direction between rolls having different circumferential velocities (air drawing).

Subsequently, the laminate was immersed (insolubilization treatment) for 30 seconds in an insolubilizing bath having a liquid temperature of 30 DEG C (an aqueous boric acid solution obtained by mixing 3 parts by weight of boric acid with 100 parts by weight of water).

Subsequently, the iodine concentration and the immersion time were adjusted so that the single light transmittance (Ts) of the obtained polarizing film was 40% or less in a dyeing bath at a liquid temperature of 30 ° C (an iodine aqueous solution obtained by mixing iodine and potassium iodide in water at a weight ratio of 1: 7) (Dyed).

Subsequently, the substrate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30 占 폚 for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 DEG C (an aqueous solution obtained by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) Uniaxial stretching was carried out by doubling (underwater stretching).

Thereafter, the laminate was immersed in a cleansing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) for 10 seconds at a liquid temperature of 30 DEG C, and then dried for 60 seconds with hot air at 60 DEG C Drying process).

Thus, a polarizing film having a thickness of 5 占 퐉 was formed on the resin substrate.

[Example 1-2]

A polarizing film was formed on the resin substrate in the same manner as in Example 1-1, except that the temperature of the heat treatment was changed to 75 캜 in the production of the laminate.

[Example 1-3]

A polarizing film was formed on the resin substrate in the same manner as in Example 1-1 except that the temperature of the heat treatment was changed to 80 캜 in the production of the laminate.

[Example 1-4]

A polarizing film was formed on the resin substrate in the same manner as in Example 1-1 except that the temperature of the heat treatment was changed to 90 캜 in the production of the laminate.

[Example 1-5]

A polarizing film was formed on a resin substrate in the same manner as in Example 1-1, except that the temperature of the heat treatment was changed to 100 캜 in the production of the laminate.

[Example 2-1]

(Preparation of laminate)

A laminate was produced in the same manner as in Example 1-1.

(Formation of polarizing film)

The laminate thus obtained was subjected to free-end uniaxial stretching using a tenter stretcher under heating at 115 캜 and stretched 4.0 times in the width direction (stretching treatment).

Subsequently, the laminate was immersed (insolubilization treatment) for 30 seconds in a insolubilizing bath having a liquid temperature of 30 DEG C (an aqueous boric acid solution obtained by mixing 3 parts by weight of boric acid with 100 parts by weight of water).

Subsequently, the iodine concentration (iodine concentration) was measured so that the single transmittance (Ts) of the obtained polarizing film was 40% or less in a dyeing bath having a liquid temperature of 30 DEG C (iodine aqueous solution obtained by mixing iodine and potassium iodide in water at a weight ratio of 1: 7) , And immersed while adjusting the immersion time (dyeing treatment).

Subsequently, the substrate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30 占 폚 for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a cleansing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30 DEG C for 10 seconds, followed by drying for 60 seconds with hot air at 60 DEG C fair).

Thus, a polarizing film having a thickness of 2.5 mu m was formed on the resin substrate.

[Example 2-2]

A polarizing film was formed on the resin substrate in the same manner as in Example 2-1, except that the temperature of the heat treatment was changed to 75 캜 in the production of the laminate.

[Example 2-3]

A polarizing film was formed on a resin substrate in the same manner as in Example 2-1, except that the temperature of the heat treatment was changed to 100 캜 in the production of the laminate.

[Comparative Example 1-1]

A polarizing film was formed on the resin substrate in the same manner as in Example 1-1, except that the heat treatment was not performed in the production of the laminate.

[Comparative Example 1-2]

A polarizing film was formed on a resin substrate in the same manner as in Example 1-1 except that the temperature of the heat treatment was changed to 50 캜 in the production of the laminate.

[Comparative Example 1-3]

A polarizing film was formed on the resin substrate in the same manner as in Example 1-1 except that the temperature of the heat treatment was changed to 55 캜 in the production of the laminate.

[Relative 2-1]

A polarizing film was formed on the resin substrate in the same manner as in Example 2-1, except that the temperature of the heat treatment was changed to 55 캜 in the production of the laminate.

(evaluation)

The following evaluations were conducted on each of the examples and comparative examples.

1. Film thickness variation

The film thickness of the PVA resin layer after (I) polyvinyl alcohol aqueous solution was applied and dried (before stretching) and (II) pneumatic stretching was measured using "MCPD3000" manufactured by Otsuka Electronics. The portion including the defect portion (the portion where the gauge band originally existed) was cut into a size of 200 mm (MD) x 200 mm (TD), and the film thickness was measured in a plane of 1 mm in both MD and TD, The difference between the thickness and the minimum film thickness was evaluated.

2. Variations of ground axis and absorption axis

(II) the slow axis direction of the PVA-based resin layer after the pneumatic stretching and the absorption axis direction of the (III) polarizing film after (I) a polyvinyl alcohol aqueous solution is applied and dried (before stretching) Axoscan " manufactured by Axometrics. The portion including the defect portion was cut into a size of 200 mm (MD) x 200 mm (TD) to obtain a measurement sample, and the maximum axial difference of the defect portion in the surface was measured. For (I) and (II), the PVA resin layer was attached to a glass plate through a pressure-sensitive adhesive layer, and the resin substrate was peeled off to measure the slow axis of the PVA resin layer.

3. Appearance

(I) a polyvinyl alcohol aqueous solution is applied and dried (before stretching), the PVA-based resin layer

(II) the PVA resin layer after the air drawing and (III) the polarizing film were visually observed.

(I) and (II), as shown in Fig. 5 (a), a commercially available polarizing plate was polymerized on each of the upper and lower sides of the laminate (sample). At that time, the two polarizing plates were arranged so that their absorption axes were orthogonal to each other, and the laminate elongation direction and the absorption axis of the lower polarizing plate were orthogonal to each other.

(III), as shown in Fig. 5 (b), a commercially available polarizing plate was polymerized under a layered product (sample), and light was irradiated from the bottom and observed from above. At that time, the absorption axis of the polarizing film of the laminate and the absorption axis of the lower polarizing plate were arranged to be perpendicular to each other.

The evaluation criteria shown in Table 1 are as follows.

○: Variation of defects is not allowed

X: Variation of defects is visible

4. Polarization degree

(Ts), a parallel transmittance (Tp) and a quadrature transmittance (Tc) of a polarizing film were measured using a spectrophotometer (product of Murakami Color Company, product name "Dot-41") and the degree of polarization P was obtained by the following formula . These transmittances are Y values measured by the second view field (C light source) of JIS Z 8701 and subjected to visibility correction.

Polarization degree (P) = {(Tp-Tc) / (Tp + Tc)} ^1/2 100

The film thickness variation and the ground axis variation and the absorption axis variation of the PVA resin layer were suppressed at all the time points in the Examples. The appearance was also excellent. In Examples 1-5 and 2-3, wrinkles were visually observed. It can be considered that this is caused by heat wrinkles generated in the resin substrate by the heat treatment.

[Industrial Availability]

The polarizing film of the present invention can be most suitably used, for example, in an image display apparatus. Specifically, it is suitably used as a liquid crystal panel such as a liquid crystal television, a liquid crystal display, a mobile phone, a digital camera, a camcorder, a portable game machine, a car navigation system, a copier, a printer, a fax machine, a clock, a microwave oven, .

10:
11: resin substrate
12: polyvinyl alcohol (PVA) -based resin layer

Claims (23)

A step of heating the resin base material to a glass transition temperature (Tg) of -15 ° C or higher of the resin base material,
And a step of forming a polyvinyl alcohol-based resin layer on the resin substrate in this order. The manufacturing method according to claim 1, wherein the resin substrate is wound from a resin base roll wound in a roll shape to form a long resin base material, and the heating step is performed. The manufacturing method according to claim 2, wherein the heating step is performed after being stored in the wound state. The manufacturing method according to claim 2, wherein the step of winding, the step of heating, and the step of forming the polyvinyl alcohol-based resin layer are continuously performed. The production method according to claim 1, wherein the heating step is performed at a glass transition temperature (Tg) + 15 ° C or less of the resin base material. The production method according to claim 1, wherein the heating step is carried out while conveying the resin base material with a conveying roll provided in a heating furnace. The manufacturing method according to claim 6, wherein the angle of the conveying rolls in the heating furnace is 90 degrees or more. The production method according to claim 6, wherein the center-to-center distance of the transport rolls in the heating furnace is 2 m or less. The manufacturing method according to claim 1, wherein the heating step is carried out while conveying the resin base material with a tenter. The production method according to claim 1, wherein the shrinkage percentage of the resin base material by heating is 3% or less. The production method according to claim 1, wherein the resin substrate is formed of a polyethylene terephthalate resin. The production method according to claim 1, wherein the resin substrate is stretched in advance. The production method according to claim 1, wherein the polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin on the resin substrate by a die coating method and drying the coating liquid. A method for producing a polarizing film using the laminate obtained by the manufacturing method according to claim 1. 15. The method of manufacturing a polarizing film according to claim 14, comprising a step of stretching the laminate. A process for producing a polarizing plate comprising a step of laminating a protective film on a polarizing film obtained by the manufacturing method according to claim 14. A stretched laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on the resin substrate,
(MD) x 200 mm (TD) of the polyvinyl alcohol-based resin layer in the size of 200 mm (MD) x 200 mm (TD) of the polyvinyl alcohol-based resin layer is 0.25 m or less Wherein a variation of the slow axis in the size is 0.50 or less. A winding means for winding the resin base material from a resin base roll wound in a roll shape in a long resin base material,
A heating furnace provided with a conveying roll for conveying the elongated resin substrate and heating the resin substrate to a glass transition temperature (Tg) of -15 ° C or higher of the resin substrate;
And a coating means for applying a coating liquid containing a polyvinyl alcohol-based resin on a heated resin base material. The manufacturing apparatus according to claim 18, wherein the resin substrate is transported while being heated in a transport roll provided in the heating furnace. 19. The manufacturing apparatus according to claim 18, wherein the angle of the conveying roll in the heating furnace is 90 DEG or more. 19. The production apparatus according to claim 18, wherein a distance between centers of the transport rolls in the heating furnace is 2 m or less. A winding means for winding the resin base material from a resin base roll wound in a roll shape in a long resin base material,
(Tg) of the resin base material to -15 占 폚 or higher with respect to the resin base material held at both ends by a clip of the tenter, and a tenter for holding and conveying both ends of the elongated resin base material Heating means,
And a coating means for applying a coating liquid containing a polyvinyl alcohol-based resin on a heated resin base material. 23. The manufacturing apparatus according to claim 22, wherein the resin substrate is heated while being transported by the tenter.

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