TW201604016A - Method for producing laminate - Google Patents

Abstract

Provided is a laminate which enables the formation of a polarizing film having uniform performance. A method for producing a laminate according to the present invention comprises, in the following order, a step for heating a resin base to a temperature that is lower than the glass transition temperature (Tg) of the resin base by 15 DEG C or higher and a step for forming a polyvinyl alcohol resin layer on the resin base.

Description

Manufacturing method of laminated body Field of invention

The present invention relates to a method of manufacturing a laminate. 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.

Background of the invention

A method of forming a PVA-based resin layer on a resin substrate and stretching and dyeing the laminate to obtain a polarizing film has been proposed (for example, Patent Document 1 and Patent Document 2). According to the above method, a polarizing film having a small thickness can be obtained, which is attracting attention because it contributes to, for example, thinning of an image display device. However, in this case, there is a problem that the properties of the obtained polarizing film (specifically, film thickness, optical characteristics, and appearance) are liable to be inconsistent.

Prior technical literature Patent literature

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

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

Summary of invention

The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a laminate in which a polarizing film having uniform properties can be produced.

The method for producing a laminate of the present invention comprises a step 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 resin on the resin substrate. The steps of the layer.

In one embodiment, the resin substrate is wound up from a resin substrate roll in which a long resin substrate is wound into a roll shape, and the heating step is performed.

In one embodiment, after the storage in the winding state, the heating step is performed.

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

In one embodiment, the heating step is performed at a glass transition temperature (Tg) of the resin substrate of +15 ° C or lower.

In one embodiment, the resin substrate is conveyed by a transfer roller provided in a heating furnace, and the heating step is performed at the same time.

In one embodiment, the angle of the transport roller in the heating furnace is 90° or more.

In one embodiment, the distance between the centers of the conveying rollers in the heating furnace is 2 m or less.

In one embodiment, the resin substrate is conveyed by a tenter while the heating step is performed.

In one embodiment, the shrinkage ratio of the resin substrate caused 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 pre-stretched.

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

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

In one embodiment, the step of stretching the laminate is included.

According to still another aspect of the present invention, a method of manufacturing a polarizing plate can be provided. The method for producing a polarizing plate includes the step of laminating a protective film on a polarizing film, and the polarizing film is obtained by the above-described manufacturing method.

According to still another aspect of the present invention, a stretched laminate can be provided. The stretched laminate has a resin substrate and a polyvinyl alcohol-based resin layer formed on the resin substrate. The film thickness of the polyvinyl alcohol-based resin layer in a size of 200 mm (MD) × 200 mm (TD) is not more than 0.25 μm, and the polyvinyl alcohol-based resin layer is in a size of 200 mm (MD) × 200 mm (TD). The phase axis of the stagnation is not more than 0.50°.

According to still another aspect of the present invention, a manufacturing apparatus of a laminated body can be provided.

In one embodiment, the manufacturing apparatus includes a winding mechanism and a conveying roller that winds the resin base from a resin substrate roll in which a long resin substrate is wound into a roll shape. The conveyance roller conveys the long resin substrate; and the heating furnace and the coating mechanism are provided. In the hot furnace, the resin substrate is heated to a glass transition temperature (Tg) of -15 ° C or higher of the resin substrate, and the coating means applies a coating liquid containing a polyvinyl alcohol-based resin on the heated resin substrate.

In one embodiment, the resin substrate is conveyed by a transfer roller provided in the heating furnace while being heated.

In one embodiment, the angle of the transport roller in the heating furnace is 90° or more.

In one embodiment, the distance between the centers of the conveying rollers in the heating furnace is 2 m or less.

In one embodiment, the manufacturing apparatus includes a winding mechanism and a tenter, and the winding mechanism winds the resin base from a resin substrate roll in which a long resin substrate is wound into a roll shape. The tenter is configured to hold both end portions of the long resin substrate and carry it, and further includes a heating mechanism and a coating mechanism for holding two clips through the tenter of the tenter The resin substrate at the end portion is heated to a glass transition temperature (Tg) of -15 ° C or higher of the resin substrate, and the coating mechanism applies a coating liquid containing a polyvinyl alcohol-based resin on the heated resin substrate.

In one embodiment, the resin substrate is conveyed by the tenter while heating.

According to the present invention, by subjecting the resin substrate to a heat treatment at a predetermined temperature or higher, it is possible to alleviate (uniformize) the surface unevenness of the resin substrate (for example, a gauge band which occurs when the resin substrate is wound up). As a result, a PVA-based resin layer having a good thickness uniformity can be formed on the resin substrate. Correct By performing various treatments on the PVA-based resin layer having a good thickness uniformity, it is possible to produce a polarizing film which does not exhibit performance (specifically, film thickness, optical characteristics, and appearance) and has excellent uniformity (for example, it satisfies the requirements of the liquid crystal television). Quality).

10‧‧‧Layer

11‧‧‧Resin substrate

12‧‧‧Polyvinyl alcohol (PVA) resin layer

100‧‧‧Layered body manufacturing equipment

21‧‧‧Clamps

30‧‧‧Resin substrate roll

40‧‧‧Roll-out roller

50‧‧‧ heating device

60‧‧‧ Coating device

70‧‧‧Drying device

80‧‧‧Wind roller

90‧‧‧Transport roller

A‧‧‧ oven

R1, R2, R3, R4, R5, R6‧‧‧ free rolls

W ₀ , W ₁ ‧‧‧Width

θ ‧‧‧抱角

Fig. 1 is a schematic cross-sectional view showing a laminated body 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 in an embodiment.

Fig. 3 is a schematic view showing a heating method of a resin substrate in another embodiment.

Fig. 4 is a schematic view showing an example of the present invention.

(a) and (b) of FIG. 5 are schematic views for explaining the method of evaluating the appearance of the PVA-based resin layer.

Form for implementing the invention

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

A. Laminated body

Fig. 1 is a schematic cross-sectional view showing a laminated body according to an embodiment of the present invention. The laminated body 10 is obtained by forming a polyvinyl alcohol (PVA)-based resin layer 12 on the resin substrate 11.

A-1. Resin substrate

The above resin substrate is typically elongated. The thickness of the resin substrate is preferably It is from 20 μm to 300 μm, more preferably from 50 μm to 200 μm.

The material for forming the resin substrate may, for example, be polyethylene terephthalate. An ester resin such as a diester resin, a cycloolefin resin, an olefin resin such as polypropylene, a (meth)acrylic resin, a polyamide resin, a polycarbonate resin, or the like, or the like. It is preferred to use a polyethylene terephthalate resin. Among them, an amorphous polyethylene terephthalate resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer containing isophthalic acid as a dicarboxylic acid or a cyclohexanedimethanol as a glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 170 ° C or lower. By using the above-mentioned resin substrate, the laminate can be stretched at a temperature at which the crystallization of the PVA-based resin is not rapidly accelerated, and the problem caused by the crystallization can be suppressed (for example, PVA which is prevented from being caused by stretching) Orientation of the resin layer). Further, the glass transition temperature of the resin substrate is preferably 60 ° C or higher. Further, the glass transition temperature (Tg) is a value obtained based on JIS K 7121.

The resin substrate can be formed by any suitable method. Forming side The method may, for example, be a melt extrusion method, a solution casting method (solution casting method), a calender molding method, a compression molding method, or the like. Among them, the melt extrusion method is preferred.

Surface modification treatment (such as corona) can be performed on the surface of the resin substrate Processing, etc.), can also be formed with an easy layer. By the above treatment, the adhesion between the resin substrate and the PVA-based resin layer can be improved. The surface modification treatment and/or the formation of the easy-to-adhere layer may be performed before the heat treatment described later, or may be performed after the heat treatment. Further, if stretching is to be described later, it may be carried out before the stretching, or may be carried out after the stretching.

In one embodiment, the tree is stretched before the heat treatment described later. Lipid substrate. The stretching method of the resin substrate can be carried out by any appropriate method. Specifically, fixed end stretching or free end stretching may be employed. Moreover, simultaneous biaxial stretching or sequential biaxial stretching can also be employed. The stretching of the resin substrate can be carried out in one stage or in multiple stages. When the multi-stage is carried out, the stretching ratio of the resin substrate described later is the product of the stretching ratio at each stage. Further, the stretching method is not particularly limited, and it may be an air stretching method or an underwater stretching method.

The stretching direction of the resin substrate can be appropriately set. For example, will be long The strip-shaped resin substrate is stretched in the width direction. Specifically, the resin substrate is conveyed in the longitudinal direction and stretched in a direction (TD) orthogonal to the transport direction (MD). In the present specification, the term "orthogonal" also includes a substantially orthogonal pattern. Here, the term "substantially orthogonal" includes a case of 90 ° ± 5.0 °, preferably 90 ° ± 3.0 °, and more preferably 90 ° ± 1.0 °. By stretching the resin substrate in the width direction (TD), the resin substrate can be effectively utilized. Further, the thickness of the resin substrate can be made uniform in TD, and the film thickness of the latter will not be suppressed.

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

The stretching ratio of the resin substrate is preferably relative to the original length of the resin substrate The degree is 1.5 times or more. By setting it as the above range, it can suppress well after The case where some of the film thicknesses are inconsistent. Further, the stretching ratio of the resin substrate is preferably 3.0 times or less with respect to the original length of the resin substrate. By setting it as the said range, wrinkles generate|occur|produce in the heating process mentioned later can suppress favorably.

A-2. Reeling and storage

In one embodiment, the elongated resin substrate is wound into a roll shape. When the resin substrate is formed, the partial film thickness does not match, and the winding in this state may cause irregularities in the resin substrate. Typical web tension is from 60 N/m to 150 N/m (unit: N/m is the tension per unit width). The wound resin substrate can be kept in a bundled state for storage (placement) in any suitable period before being supplied to the next step. For example, when the PVA-based resin layer is not formed continuously after the resin substrate is molded, the resin substrate is kept in a wound state and stored. When the storage period is long (for example, three days or more), the occurrence of unevenness (the degree of unevenness and the number of occurrence of unevenness) becomes remarkable, and the PVA-based resin layer (layered body) obtained has a film thickness unevenness. tendency. Therefore, the longer the storage period of the resin substrate wrap, the more remarkable the effect of the heat treatment described later can be obtained. Further, the resin substrate roll can be stored in any suitable gas atmosphere. The storage temperature is, for example, 15 ° C to 35 ° C. The relative humidity is, for example, 40% RH to 80% RH.

A-3. Heating

The above resin substrate is heated. Specifically, the resin substrate is heated by a hot air, an infrared heater, a roller heater or the like. The heating temperature is preferably a glass transition temperature (Tg) of the resin substrate of -15 ° C or more, more preferably Tg - 10 ° C or more, and still more preferably Tg - 5 ° C or more. When a polyethylene terephthalate resin is used as a material for forming a resin substrate, the heating temperature is preferably 68 ° C or higher. By Heating the resin substrate at the above temperature can alleviate (uniformize) the unevenness of the surface of the resin substrate. As a result, the PVA-based resin layer to be described later can be favorably formed, and a PVA-based resin layer having a good thickness uniformity can be formed. Further, the heating temperature is preferably (Tg) + 15 ° C or less, and more preferably (Tg) + 10 ° C or less. When a polyethylene terephthalate resin is used as a material for forming a resin substrate, the heating temperature is preferably 80 ° C or lower. By heating the resin substrate at the above temperature, occurrence of wrinkles (hot wrinkles) can be satisfactorily suppressed.

The heating time is preferably from 70 seconds to 150 seconds, and more preferably from 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 can be shrunk in the width direction by heating (TD shrinkage). The shrinkage ratio (TD shrinkage ratio) of the resin substrate is preferably 3% or less, more preferably 2% or less, and particularly preferably 1.5% or less. When the shrinkage ratio is in the above range, the occurrence of wrinkles is suppressed, and a good appearance can be obtained. In addition, the TD shrinkage rate is calculated by the following formula.

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

In one embodiment, the resin substrate is heated while being conveyed. When the resin substrate is wound into a roll shape as described above, it is preferable to heat-treat the resin substrate wound from the resin substrate roll. The heating method is, for example, a method of conveying a resin substrate by a transfer roller provided in a heating furnace, and a method of heating the resin substrate while carrying it by a tenter. With the former, the size of the device can be suppressed. With the latter, wrinkles can be suppressed extremely well.

Figure 2 (a) and Figure 2 (b) show the specific use of the conveyor roller example. In the illustrated example, the resin substrate 11 is conveyed in the longitudinal direction by the free rolls R2 to R5 provided in the oven A, whereby the resin substrate 11 is heated. From the viewpoint of the production speed, it is preferable to provide four or more free rolls in the oven as shown in the figure.

The angle of the free roller in the oven should preferably be above 90 °C. In the picture In the example shown in 2 (a), the wrap angle θ of the free rolls R2 and R5 is set to 90°, and the wrap angle θ of the free rolls R3 and R4 is set to 180°. In the example shown in Fig. 2(b), the wrap angle θ of the free rolls R2 to R5 is set to 90°. By setting the hoop angle, the shrinkage of the resin substrate is suppressed, and wrinkles can be suppressed. In addition, when the wrap angle is viewed from a cross section perpendicular to the axial direction, a line connecting the center point of the free roll and the contact start point of the resin substrate and the free roll, and the center point of the connection free roll and The angle formed by the straight line of the contact end point of the resin substrate and the free roller. The interval between the free rolls in the oven (the distance between the centers of the rolls) is preferably 2 m or less. Further, the two free rolls provided in a state of crossing the inlet and outlet of the oven are preferably spaced apart from each other (between R1 and R2 and between R5 and R6 in the illustrated example) of 2 m or less. By setting the interval, the shrinkage of the resin substrate is suppressed, and wrinkles can be suppressed. Further, in the present embodiment, the shrinkage of the resin substrate is also related to the stretching ratio, the heating temperature, and the like of the resin substrate.

A specific example when a tenter is used is shown in FIG. Figure example In the clips 21 and 21 on the left and right sides of the tenter, the both ends of the resin substrate 11 are held on the line orthogonal to the transport direction, and are transported in the heating zone at a predetermined speed in the longitudinal direction, thereby heating the resin. Substrate 11. Transport direction The distance between the clips (the distance between the ends of the adjacent clips) is preferably 20 mm or less, and more preferably 10 mm or less. The width of the clip should be 20mm or more, and more preferably 30mm or more. In the present embodiment, the TD shrinkage of the resin substrate can be controlled by, for example, adjusting the distance between the left and right clips. Specifically, when the distance between the right and left clips is not changed and moved, the TD shrinkage rate is substantially 0%. On the contrary, the resin substrate can be subjected to TD stretching by widening the distance between the left and right clips. The TD change rate of the resin substrate is preferably 1.00 times or more, and more preferably 1.00 times to 1.10 times. In addition, the TD change rate is calculated according to the following formula.

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

A-4. Formation of PVA resin layer

The PVA-based resin forming the PVA-based resin layer may be any suitable resin. For example, polyvinyl alcohol or ethylene-vinyl alcohol copolymer can be cited. Polyvinyl alcohol can be obtained by saponification of polyethylene ethyl ester. The ethylene-vinyl alcohol copolymer is obtained by saponification of an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually from 85 mol% to 100 mol%, preferably from 95.0 mol% to 99.95 mol%, more preferably from 99.0 mol% to 99.93 mol%. The degree of saponification can be determined based on JIS K 6726-1994. By using the above-described saponification degree PVA-based resin, a polarizing film having excellent durability can be obtained. When the degree of saponification is too high, there is a fear of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually from 1,000 to 10,000, preferably from 1200 to 4500, and more preferably from 1,500 to 4,300. Further, the average degree of polymerization can be determined based on JIS K 6726-1994.

It is preferable to apply a coating liquid containing a PVA resin on a resin substrate. It is dried to form a PVA-based resin layer. Typically, the coating liquid is a solution obtained by dissolving the PVA-based resin in a solvent. As the solvent, a polyol such as water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, trimethylolpropane, or the like can be used. An amine, an amine such as diethylenetriamine. These may be used singly or in combination of two or more. Water is preferred among them. The concentration of the PVA-based resin of the solution is preferably from 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. When the above resin concentration is employed, a uniform coating film adhered to the resin substrate can be formed.

The coating liquid may also contain an additive. Additives such as plasticization Agent, surfactant, etc. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. The surfactant may be exemplified by a nonionic surfactant. The above may be used for the purpose of further improving the uniformity, dyeability or stretchability of the obtained PVA-based resin layer. Further, the additive may be exemplified by an easy-to-contact component. By using an easy-to-contact component, the adhesion between the resin substrate and the PVA-based resin layer can be improved. As a result, it is possible to suppress problems such as peeling of the PVA-based resin layer from the resin substrate, and it is possible to satisfactorily perform dyeing and underwater stretching which will be described later. The easy-to-use component may be a modified PVA such as an ethylene-based modified PVA.

The coating method of the coating liquid can be any suitable method. 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, a knife coating method (comma blade coating method, etc.) may be mentioned.

In one embodiment, a die coating method is employed. In the die coating method, since the coating liquid is applied by fixing the gap between the resin substrate and the mold (such as a fountain mold or a slit mold), a coating film having excellent thickness uniformity can be obtained. another On the other hand, when unevenness occurs in the resin substrate, the distance between the resin substrate and the lip is not uniform, and it may be difficult to form a uniform coating film. Therefore, when the die coating method is employed, the effect of the above heat treatment can be remarkably obtained.

Applying the above coating liquid to PVA resin after drying The layer thickness is preferably from 3 μm to 40 μm, and more preferably from 3 μm to 20 μm. The coating and drying temperature of the coating liquid is preferably 50 ° C or higher.

It is preferred to form a PVA-based resin layer after the above heating. E.g, After heating, the resin substrate is not wound, and a PVA-based resin layer is formed on the resin substrate. This is because the effect of the above heating can be obtained satisfactorily.

In addition, before the formation of the PVA-based resin layer, the resin substrate may also be used. An undercoat layer (primer layer) is formed in advance on the PVA-based resin layer forming side. The material constituting the primer layer is not particularly limited as long as it exerts a certain degree of strong force on both the resin substrate and the PVA-based resin layer. For example, a thermoplastic resin excellent in transparency, heat stability, stretchability, and the like can be used. The thermoplastic resin may, for example, be an acrylic resin, a polyolefin resin, a polyester resin, a polyvinyl alcohol resin or a mixture thereof.

A-5. Others

In one embodiment, the resin substrate is wound up from the resin substrate roll (winding step), the resin substrate is heated (heating step), and the PVA resin layer (pVA resin layer forming step) is formed. According to the above embodiment, the effect of the above heat treatment can be favorably obtained. As a specific example of the present embodiment, as shown in FIG. 4, a step of winding, heating, and PVA-based resin layer formation on a series of lines for transporting a long resin substrate is sequentially performed. The laminated body manufacturing apparatus 100 shown in FIG. 4 includes a take-up roll 40, a heating device 50, The coating device 60, the drying device 70, and the winding roller 80; the winding roller 40 is for unwinding the resin substrate 11 from the resin substrate roll 30, and the heating device 50 is for heating the resin substrate 11 The coating device 60 is for applying a coating liquid containing the PVA resin to the surface of the resin substrate 11, the drying device 70 is for drying the applied coating liquid, and the winding roller 80 is used. The laminated body 10 is wound. In addition to this, the laminated body manufacturing apparatus 100 further includes a plurality of conveying rollers 90.

B. Stretched laminate

The stretched laminate of the present invention is obtained by stretching the above laminate. In one embodiment, the stretched laminate is produced by stretching the laminate at a draw ratio of 1.5 times or more and 3.0 times or less by an air stretching method. The details of the laminate stretching method will be described later. In the stretched laminate, the film thickness of the PVA-based resin layer in a size of 200 mm (MD) × 200 mm (TD) is preferably 0.25 μm or less, more preferably 0.20 μm or less. In the stretched laminate, the phase of the slow phase of the PVA-based resin layer in a size of 200 mm (MD) × 200 mm (TD) is preferably 0.50 or less, more preferably 0.30 or less, and particularly preferably 0.25 or less.

C. Polarizing film

The polarizing film of the present invention is obtained by subjecting a PVA-based resin layer of the laminate to a polarizing film.

Examples of the treatment for forming the polarizing film include a dyeing treatment, a stretching treatment, an insolubilization treatment, a crosslinking treatment, a washing treatment, and a drying treatment. These processes can be appropriately selected depending on the purpose. Further, the processing order, the processing timing, the number of processing, and the like can be appropriately set. The following describes each process.

(dyeing treatment)

The above dyeing treatment is typically carried out by dyeing a PVA-based resin layer with a dichroic substance. It is preferable to carry out the adsorption of the dichroic substance by the PVA-based resin layer. The adsorption method may be a method in which a PVA-based resin layer (layered body) is immersed in a dyeing liquid containing a dichroic substance, a method of coating the dyeing liquid on a PVA-based resin layer, and spraying the dyeing liquid on a PVA system. A method of a resin layer or the like. It is preferred to immerse the laminate in the dyeing solution. This is because the dichroic substance can be adsorbed well.

Examples of the above dichroic substance include iodine and an organic dye. These may be used singly or in combination of two or more. The dichroic material is preferably iodine. When iodine is used as the dichroic substance, the above dyeing liquid is preferably an aqueous iodine solution. The blending amount of iodine is preferably from 0.05 part by weight to 5.0 parts by weight relative to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is preferred to incorporate iodide in an aqueous solution of iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, titanium iodide and the like. Among them, potassium iodide is preferred. The amount of the iodide blended is preferably from 0.3 part by weight to 15 parts by weight per 100 parts by weight of the water.

The liquid temperature at the time of dyeing the dyeing solution is preferably from 20 ° C to 40 ° C. When the PVA-based resin layer is immersed in the dyeing liquid, the soaking time is preferably from 10 seconds to 300 seconds. The PVA-based resin layer can sufficiently adsorb the dichroic substance under the above conditions. Further, the dyeing conditions (concentration, liquid temperature, soaking time) may be set such that the polarizing degree or the monomer light transmittance of the finally obtained polarizing film is within a predetermined range. In one embodiment, the soaking time is set such that the degree of polarization of the obtained polarizing film is 99.98% or more. In another embodiment, the soaking time is set to The light transmittance of the obtained polarizing film was about 40%.

(stretching treatment)

The stretching method of the laminate may be carried out by any suitable method. Specifically, a fixed end stretching method (for example, a method using a tenter stretching machine) or a free end stretching method (for example, a method in which a laminated body is passed between rolls having different peripheral speeds for uniaxial stretching) may be employed. ). Further, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or sequential biaxial stretching may be employed. The stretching of the laminate can be carried out in one stage or in multiple stages. When the multi-stage is carried out, the stretching ratio (maximum stretching ratio) of the laminated body to be described later is the product of the stretching ratio at each stage.

Stretching treatment can be carried out by soaking the laminated body in a stretching bath. The method of stretching in water can also be carried out in the air. It is preferred to carry out at least one water stretching treatment, and the combined water stretching treatment and the aerial stretching treatment are better. When stretching in water, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80 ° C) of the resin substrate or the PVA-based resin layer, thereby suppressing crystallization of the PVA-based resin layer. In the case of high magnification stretching. As a result, a polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

The direction of stretching of the laminate can be selected in any suitable direction. Yu Yi In the embodiment, the film is stretched in the longitudinal direction of the long laminated body. Specifically, the laminated body is conveyed in the longitudinal direction, and the stretching direction is the conveying direction (MD). In another embodiment, the film is stretched in the width direction of the long laminated body. Specifically, the laminated body is conveyed in the longitudinal direction, and the stretching direction is a direction (TD) orthogonal to the conveying direction (MD).

The stretching temperature of the laminate can correspond to the formation of the resin substrate Set the material and the stretching method to any appropriate value. When the air stretching method is employed, the stretching temperature is preferably a glass transition temperature (Tg) or more of the resin substrate, and the glass transition temperature (Tg) of the resin substrate is preferably 10 ° C or more, and more preferably Tg + 15 ° C or more. Further, the stretching temperature of the laminate is preferably 170 ° C or less. When the stretching is carried out at the above temperature, the rapid crystallization of the PVA-based resin can be suppressed, and the problem caused by the crystallization (for example, the orientation of the PVA-based resin layer which occurs due to stretching) can be suppressed.

When the stretching method is in the water stretching mode, the temperature of the stretching bath is preferably It is preferably from 40 ° C to 85 ° C and from 50 ° C to 85 ° C. When it is the above temperature, it can be stretched at a high rate while suppressing dissolution of the PVA-based resin layer. Specifically, 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. At this time, if the stretching temperature is lower than 40 ° C, even if plasticization of the resin substrate due to water is considered, stretching may not be performed satisfactorily. Further, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and the excellent optical properties may not be obtained.

When using the water stretching method, it is advisable to soak the laminate in boric acid water. Stretching in solution (boring in boric acid water). By using a boric acid aqueous solution as a stretching bath, the PVA-based resin layer can be imparted with rigidity to withstand the tension at the time of stretching and water-insoluble water resistance. Specifically, boric acid can form a tetrahydroborate anion in an aqueous solution and hydrogen-bond and crosslink with a PVA-based resin. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, and can be favorably stretched, and a polarizing film having excellent optical properties can be obtained.

The above boric acid aqueous solution is preferably dissolved by dissolving boric acid and/or borate It is prepared in water as a solvent. The boric acid concentration is preferably from 1 part by weight to 10 parts by weight relative to 100 parts by weight of water. When the concentration of the boric acid is 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having better characteristics can be produced. Further, 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 may also be used.

It is preferred to incorporate an iodide in the above stretching bath (aqueous boric acid solution). borrow By dispersing the iodide, the dissolution of the adsorbed iodine in the PVA-based resin layer can be suppressed. Specific examples of the iodide are as described above. The concentration of the iodide is preferably from 0.05 part by weight to 15 parts by weight, more preferably from 0.5 part by weight to 8 parts by weight, per 100 parts by weight of the water.

The time during which the laminate is soaked in the stretching bath is preferably from 15 seconds to 5 minutes.

The draw ratio (maximum draw ratio) of the laminate is typically 4.0 times or more with respect to the original length of the laminate, and 5.0 or more is preferable. Such a higher draw ratio can be achieved, for example, by stretching in water (stretching in boric acid water). In the present specification, the "maximum stretching ratio" means a stretching ratio immediately before the laminate is broken, and it is also confirmed that the stretching ratio for breaking the laminate is 0.2 lower than the value.

The stretching treatment in water is preferably carried out after the dyeing treatment.

(insolubilization treatment)

The above insolubilization treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. In particular, when the water stretching method is employed, the insolubilization treatment can impart water resistance to the PVA-based resin layer. Thickening of the boric acid aqueous solution The amount is preferably from 1 part by weight to 4 parts by weight per 100 parts by weight of the water. The liquid temperature of the insoluble bath (aqueous boric acid solution) is preferably from 20 ° C to 50 ° C. The insolubilization treatment is preferably carried out after the layered body is formed, before the dyeing treatment and the water stretching treatment.

(cross-linking processing)

The above crosslinking treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, the PVA-based resin layer can be imparted with water resistance. The concentration of the aqueous boric acid solution is preferably from 1 part by weight to 4 parts by weight based on 100 parts by weight of the water. Further, when the crosslinking treatment is carried out after the above dyeing treatment, it is preferable to further mix the iodide. By mixing the iodide, the dissolution of the adsorbed iodine in the PVA-based resin layer can be suppressed. The amount of the iodide blended is preferably from 1 part by weight to 5 parts by weight relative to 100 parts by weight of water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably from 20 ° C to 50 ° C. The crosslinking treatment is preferably carried out before the stretching treatment in water. In a preferred embodiment, the dyeing treatment, the crosslinking treatment, and the underwater stretching treatment are sequentially performed.

(washing treatment)

The above washing treatment is typically carried out by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.

(drying treatment)

The drying temperature for the drying treatment is preferably from 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 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and particularly preferably 5 μm or less. The above polarizing film can suppress the occurrence of cracks or the like in an environmental test (for example, an environmental test at 80 ° C). Further, the thickness of the polarizing film is preferably 0.5 μm or more, and more preferably 1.0 μm or more. The above polarizing film is extremely excellent in conveyability at the time of production or the like.

The polarizing film should be at any wavelength from 380nm to 780nm With absorption dichroism. When the monomer transmittance is 42% or more, the degree of polarization of the polarizing film is preferably 99.9% or more.

D. Polarizer

The polarizing plate of the present invention has the above polarizing film. Preferably, the polarizing plate has the polarizing film and a protective film disposed on at least one side of the polarizing film. As the protective film, the above resin substrate may be used as it is, or a film different from the above resin substrate may be used. Examples of the material for forming the protective film include (meth)acrylic resin; cellulose resin such as cellulose diacetate or cellulose triacetate; cycloolefin resin; olefin resin such as polypropylene; and polyethylene terephthalate An ester resin such as a diester resin; a polyamide resin; a polycarbonate resin; and a copolymer resin thereof. The thickness of the protective film is preferably from 10 μm to 100 μm.

As described above, in one embodiment, the resin substrate is not directly peeled off from the polarizing film, and it is directly used as a protective film. In another embodiment, the resin substrate is peeled off from the polarizing film, and another film is laminated. The protective film is permeable to the layer of the polarizing film, or may be laminated (not through the adhesive layer). The layer is then typically formed with an adhesive or an adhesive. According to the present invention, a polarizing film having excellent thickness uniformity can be obtained, so that the protective film can be favorably laminated on the polarizing film.

Example

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

[Example 1-1] (production of laminated body)

The resin substrate is composed of amorphous isononic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) having a water absorption ratio of 0.75% and a glass transition temperature (Tg) of 75 ° C, and is previously at 115 ° C. TD was stretched to 2.0 times, and was elongated and had a thickness of 100 μm. The resin substrate was wound into a roll shape at a tension of 100 N/m to form a resin substrate roll, and it was wound at 25 ° C. Store in an environment with a relative humidity of 60% RH for 30 days.

Thereafter, the resin substrate was taken up from the resin substrate roll, and the resin substrate was transferred and heat-treated at 70 ° C for 60 seconds.

Next, one surface of the resin substrate is subjected to corona treatment. It will contain polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetonitrile modified PVA in a ratio of 9:1 (degree of polymerization 1200, acetylation degree 4.6%, degree of saponification) An aqueous solution of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Co., Ltd., trade name "Gohsefimer Z200", was applied to the corona-treated surface by a die coating method at 25 ° C, and dried at 60 ° C for 200 seconds to form a thickness of 10 μm. A PVA-based resin layer is used to produce a laminate.

(production of polarizing film)

The obtained laminate was placed in an oven at 115 ° C and uniaxially stretched to 2.0 times (air stretch) at the free end in the longitudinal direction between rolls having different peripheral speeds.

Next, the laminate was immersed in an insoluble bath at a liquid temperature of 30 ° C (an aqueous solution of boric acid prepared by mixing 3 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).

Next, it is immersed in a dye bath at a liquid temperature of 30 ° C (an aqueous solution of iodine prepared by mixing iodine and potassium iodide in a ratio of 1:7 by weight in water), and adjusting the iodine. The concentration and the soaking time are such that the transmittance (Ts) of the obtained polarizing film is 40% or less (dyeing treatment).

Next, it was immersed in a crosslinking bath at a liquid temperature of 30 ° C (a boric acid aqueous solution prepared by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid at a liquid temperature of 70 ° C (an aqueous solution prepared by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water), and between rolls having different peripheral speeds. Uniaxial stretching in the length direction to 2.7 times (water stretching).

Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 30 ° C (an aqueous solution prepared by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water), and then dried at 60 ° C for 60 seconds in warm air (washing) Net, drying step).

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

[Example 1-2]

In the case of producing a laminate, 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 °C.

[Example 1-3]

In the case of producing a laminate, 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 °C.

[Example 1-4]

In the case of producing a laminate, 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 °C.

[Example 1-5]

When making a laminate, except that the heat treatment temperature is set to 100 ° C, The rest was set to be the same as in Example 1-1 to form a polarizing film on a resin substrate.

[Example 2-1] (production of laminated body)

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

(formation of polarizing film)

The obtained laminate was stretched to 4.0 times in the width direction by a tenter stretching machine at a free end uniaxial stretching under heating at 115 ° C (stretching treatment).

Next, the laminate was immersed in an insoluble bath at a liquid temperature of 30 ° C (an aqueous solution of boric acid prepared by mixing 3 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).

Next, it is immersed in a dye bath (liquid iodine solution prepared by mixing iodine and potassium iodide in a ratio of 1:7 by weight in water at a liquid temperature of 30 ° C), and adjusting the iodine concentration and the soaking time to obtain the obtained The light transmittance (Ts) of the polarizing film is 40% or less (dyeing treatment).

Next, it was immersed in a crosslinking bath at a liquid temperature of 30 ° C (a boric acid aqueous solution prepared by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) (crosslinking treatment).

Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 30 ° C (an aqueous solution prepared by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water), and then dried at 60 ° C for 60 seconds in warm air (washing) Net, drying step).

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

[Example 2-2]

In the case of producing a laminate, 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 °C.

[Example 2-3]

In the case of producing a laminate, 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 100 °C.

[Comparative Example 1-1]

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

[Comparative Example 1-2]

In the case of producing a laminate, 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 50 °C.

[Comparative Example 1-3]

In the case of producing a laminate, 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 °C.

[Comparative Example 2-1]

In the case of producing a laminate, 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 °C.

(Evaluation)

The following evaluations were performed for each of the examples and comparative examples.

1. Inconsistent film thickness

The film thickness of the PVA-based resin layer after the polyvinyl alcohol aqueous solution was applied and dried (before stretching) and (II) in the air was measured using "MCPD3000" manufactured by Otsuka Electronics Co., Ltd. The part including the defect portion (the portion having the gluten) was cut out to a size of 200 mm (MD) x 200 mm (TD) as a measurement sample, and both MD and TD were measured in a plane at intervals of 1 mm to evaluate the defect. The difference between the maximum film thickness and the minimum film thickness.

2. The phase axis is inconsistent and the absorption axis is inconsistent

The "Axoscan" manufactured by Axometrics, Inc. was used to measure (I) the PVA-based resin layer of the PVA-based resin layer after coating the polyvinyl alcohol aqueous solution and drying (before stretching), and (II) the PVA-based resin layer after aerial stretching. The direction of the slow axis and (III) the absorption axis direction of the polarizing film. The portion including the defective portion was cut into a size of 200 mm (MD) x 200 mm (TD) as a measurement sample, and the maximum axial direction difference of the defective portion in the plane was measured. Further, in (I) and (II), the PVA-based resin layer was bonded to a glass plate in an adhesive layer, and the resin substrate was peeled off, and the slow axis of the PVA-based resin layer was measured.

3. Appearance

The appearance of (I) the PVA-based resin layer after coating the polyvinyl alcohol aqueous solution and drying (before stretching), (II) the PVA-based resin layer after aerial stretching, and (III) the polarizing film were visually observed.

(I) and (II), as shown in Fig. 5 (a), in a state in which a commercially available polarizing plate is superposed on the upper and lower sides of the laminated body (sample), light is irradiated from below and visually observed from above. In this case, the absorption axes of the two polarizing plates are arranged to be orthogonal to each other, and the extending direction of the laminated body is orthogonal to the absorption axis of the lower polarizing plate.

(III), as shown in FIG. 5(b), in a state in which a commercially available polarizing plate is laminated under a laminate (sample), light is irradiated from below and visually observed from above. At this time, the absorption axis of the polarizing film disposed as the laminated body is in a state of being orthogonal to the absorption axis of the lower polarizing plate.

In addition, the evaluation criteria shown in Table 1 are as follows.

○: Failure to see the inconsistency of the defects

×: You can see the inconsistency of the defects.

4. Polarization

The transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance of the polarizing film were measured using a spectrophotometer (manufactured by MURAKAMI COLOR RESEARCH LABORATORY, trade name "Dot-41"). (Tc), and the degree of polarization (P) is obtained by the following formula. Further, the light transmittance is a Y value measured by a 2 degree field of view (C light source) of JIS Z 8701 and subjected to visual sensitivity correction.

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

In the examples, at all time points, the film thickness of the PVA-based resin layer did not match and the slow axis was inconsistent, and the absorption axis inconsistency was suppressed. Moreover, its appearance is also good. Further, in Examples 1-5 and 2-3, wrinkles were visually confirmed. This wrinkle may be caused by thermal wrinkles which occur on the resin substrate due to heat treatment.

Industrial availability

The polarizing film of the present invention is suitable for use in, for example, an image display device. Specifically, it is suitable for use as a liquid crystal television, a liquid crystal display, a mobile phone, and a number A liquid crystal panel such as a camera, a video camera, a portable game machine, a car navigation, a copying machine, a printing machine, a facsimile machine, a clock, a microwave oven, or the like, and a reflection preventing plate of an organic EL device.

10‧‧‧Layer

11‧‧‧Resin substrate

12‧‧‧Polyvinyl alcohol (PVA) resin layer

Claims (23)

A method for producing a laminate, comprising the steps of: heating a resin substrate to a glass transition temperature (Tg) of the resin substrate (Tg) of -15 ° C or higher; and forming a polyvinyl alcohol-based resin layer in the heating step A polyvinyl alcohol-based resin layer is formed on the resin substrate. The manufacturing method of claim 1, wherein the resin substrate is wound from a resin substrate roll in which a long resin substrate is wound into a roll shape, and the heating step is performed. The manufacturing method of claim 2, wherein the heating step is performed after being stored in the winding state. The production method of claim 2, wherein the winding-out step, the heating step, and the polyvinyl alcohol-based resin layer forming step are continuously performed. The manufacturing method of claim 1, wherein the heating step is performed at a glass transition temperature (Tg) of the resin substrate of +15 ° C or lower. The manufacturing method of claim 1, wherein the resin substrate is conveyed by a transfer roller provided in the heating furnace, and the heating step is performed. The manufacturing method of claim 6, wherein the conveying roller in the heating furnace has a wrap angle of 90 or more. The manufacturing method of claim 6, wherein a distance between centers of the conveying rollers in the heating furnace is 2 m or less. The manufacturing method of claim 1, wherein the resin substrate is conveyed by a tenter while the heating step is performed. The manufacturing method of claim 1, wherein the shrinkage ratio of the resin substrate caused by the heating is 3% or less. The manufacturing method of claim 1, wherein the resin substrate is formed of a polyethylene terephthalate resin. The manufacturing method of claim 1, wherein the aforementioned resin substrate is pre-stretched. The production method of claim 1, wherein the polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin onto the resin substrate by a die coating method and drying the coating liquid. A method for producing a polarizing film using the laminate produced by the production method of claim 1. A method of producing a polarizing film according to claim 14, comprising the step of stretching said laminate. A method for producing a polarizing plate, comprising the step of laminating a protective film on a polarizing film, and the polarizing film is produced by the method for producing a polarizing film according to claim 14. A stretched laminate comprising a resin substrate and a polyvinyl alcohol-based resin layer formed on the resin substrate; and the polyvinyl alcohol-based resin layer is in a size of 200 mm (MD) × 200 mm (TD) The film thickness is not equal to 0.25 μm or less, and the retardation axis of the polyvinyl alcohol-based resin layer in a size of 200 mm (MD) × 200 mm (TD) is not more than 0.50°. A manufacturing apparatus for a laminated body, comprising: a winding mechanism for winding a resin substrate from a resin substrate roll in which a long resin substrate is wound into a roll shape; and a heating furnace a conveying roller for conveying the long resin substrate, wherein the heating substrate heats the resin substrate to a glass transition temperature (Tg) of -15 ° C or higher; and the coating mechanism is heated A coating liquid containing a polyvinyl alcohol-based resin is applied onto the resin substrate. The manufacturing apparatus according to claim 18, wherein the resin substrate is conveyed while being heated by a transfer roller provided in the heating furnace. The manufacturing apparatus of claim 18, wherein the conveying roller in the heating furnace has a wrap angle of 90 or more. The manufacturing apparatus of claim 18, wherein a distance between centers of the conveying rollers in the heating furnace is 2 m or less. A manufacturing apparatus for a laminated body, comprising: a winding mechanism for winding a resin substrate from a resin substrate roll in which a long resin substrate is wound into a roll shape; and a heating mechanism provided for use A tenter that transports both end portions of the long-length resin substrate, and the heating mechanism holds the resin substrate that is held at both ends by the clip of the tenter, and heats the resin to the resin The substrate has a glass transition temperature (Tg) of -15 ° C or higher; and the coating means applies a coating liquid containing a polyvinyl alcohol-based resin on the heated resin substrate. The manufacturing apparatus of claim 22, wherein the aforementioned tenter is used to transport the aforementioned tree The lipid substrate is simultaneously heated.