TWI624373B - Laminated body for thin polarizing film - Google Patents

Abstract

The present invention provides a method of producing a thin polarizing film having excellent optical characteristics.

The method for producing a thin polarizing film of the present invention comprises the following steps: a thermoplastic resin substrate composed of a polyethylene terephthalate resin having a repeating unit (isodecanoic acid unit) represented by the general formula (I) a step of forming a layered body by forming a polyvinyl alcohol-based resin layer thereon; and a step of extending the layered body in water in an aqueous boric acid solution.

Description

Laminated body for thin polarizing film Field of invention

The present invention relates to a method of producing a thin polarizing film.

Background of the invention

A typical display device, that is, a liquid crystal display device, has an optical layered body having a polarizing film disposed on both sides of a liquid crystal cell due to an image forming method. In recent years, an optical layering system having a polarizing film has been expected to be thinned. It is proposed to disclose a method (for example, Patent Document 1), which is a thermoplastic resin substrate and a polyvinyl alcohol-based resin layer (hereinafter referred to as "PVA-based resin"). The layered body of the layer" is air-dried and then immersed in a dyeing liquid to obtain a thin polarizing film. However, such a method has a problem that the optical characteristics (for example, the degree of polarization) of the obtained thin polarizing film are insufficient.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-343521

Summary of invention

The present invention has been made to solve the above problems, and its main purpose is A thin polarizing film having excellent optical properties is provided.

The method for producing a thin polarizing film of the present invention comprises the following steps: having the general formula (I) a step of forming a layered body by forming a polyvinyl alcohol-based resin layer on a thermoplastic resin substrate composed of a polyethylene terephthalate resin of a repeating unit (isodecanoic acid unit), and a layered body in boric acid The step of extending the water in an aqueous solution.

In a preferred embodiment, the total amount of the above isoindole units is from 1 mol% to 20 mol% based on the total of the total repeat units.

In a preferred embodiment, the above polyethylene terephthalate resin has the general formula (IV) The repeating unit represented (diethylene glycol unit).

In a preferred embodiment, the total amount of the diethylene glycol unit is from 0.1 mol% to 5 mol% based on the total of the total repeat units.

In a preferred embodiment, the weight of the above polyethylene terephthalate resin is The average molecular weight (Mw) is 30,000 to 200,000.

In a preferred embodiment, the thermoplastic resin substrate has a water absorption of 0.2% or more.

In a preferred embodiment, the laminate has a maximum stretch ratio of 5.0 or more.

In a preferred embodiment, prior to extending the boric acid water, the step of extending the laminate in the air at 95 ° C or higher is included.

According to another aspect of the present invention, there is provided a thin polarizing film obtained by the above production method.

According to still another aspect of the present invention, an optical laminate having the above-described thin polarizing film is provided.

According to still another aspect of the present invention, a laminate is provided. The laminated system comprises: having the general formula (I) A thermoplastic resin substrate composed of a polyethylene terephthalate resin of a repeating unit (isodecanoic acid unit); and a PVA-based resin layer formed on the thermoplastic resin substrate.

According to the present invention, by using a thermoplastic resin substrate composed of a polyethylene terephthalate resin having an isophthalic acid unit, and using boron The acid aqueous solution is an extension bath, and the laminate in which the PVA-based resin layer is formed can be stretched with high magnification at a high rate. Specifically, such a thermoplastic resin substrate can obtain very excellent extensibility. Further, such a thermoplastic resin substrate is extended in water to absorb water, and water acts as a plasticizer to be plasticizable. As a result, it is possible to greatly reduce the elongation stress, and it is possible to extend at a high magnification, and the elongation of the thermoplastic resin substrate can be excellent as compared with the air stretching. Therefore, the maximum stretching ratio of the laminate using the thermoplastic resin substrate can be higher than that of the water extending step. Moreover, by using a boric acid aqueous solution, it is possible to impart rigidity to the PVA-based resin layer that can withstand the tension applied during stretching and water-resistance to water. In this way, the laminated body can be favorably extended in water, and a thin polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

10‧‧‧Layer

11, 11'‧‧‧ thermoplastic resin substrate

12‧‧‧PVA resin layer

12'‧‧‧Thin polarizing film

13‧‧‧Adhesive layer

14‧‧‧Separation piece

15‧‧‧ adhesive layer

16‧‧‧Optical functional film

16'‧‧‧2nd optical functional film

100‧‧‧Devolution

110‧‧‧Bath of boric acid aqueous solution

111, 112, 121, 122, 131, 132, 141, 142, 151, 152‧‧ ‧ rolls

120‧‧‧ bath of aqueous solution of dichroic substance and potassium iodide

130‧‧‧ bath of aqueous solution of iodic acid and potassium iodide

140‧‧‧Bath of aqueous boric acid solution

150‧‧‧Bath of potassium iodide solution

160‧‧‧Winding Department

200‧‧‧Optical film laminate

300,400‧‧‧Optical functional film laminate

Fig. 1 is a schematic cross-sectional view showing a laminate of a preferred embodiment of the present invention.

Fig. 2 is a schematic view showing an example of a method for producing a thin polarizing film of the present invention.

3(a) to 3(b) are schematic cross-sectional views showing an optical thin film laminate of a preferred embodiment of the present invention.

4(a) to 4(b) are schematic cross-sectional views showing an optical thin film laminate of another preferred embodiment of the present invention.

Form for implementing the invention

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

A. Manufacturing method

The method for producing a thin polarizing film of the present invention comprises the steps of: forming a PVA-based resin layer on a thermoplastic resin substrate to produce a laminate; (Step A); and extending the laminate in water in an aqueous solution of boric acid Step (Step B) (extension in boric acid water). The respective steps are explained below.

A-1. Step A

Fig. 1 is a schematic configuration diagram of a laminate according to a preferred embodiment of the present invention. The laminated body 10 has the thermoplastic resin substrate 11 and the PVA-based resin layer 12, and can be produced by forming the PVA-based resin layer 12 on a thermoplastic resin substrate. The method of forming the PVA-based resin layer 12 can be any appropriate method. The PVA-based resin layer 12 is preferably formed by applying a coating liquid containing a PVA-based resin layer to the thermoplastic resin substrate 11 and drying it.

The thermoplastic resin substrate is composed of a polyethylene terephthalate resin, and the polyethylene terephthalate resin has the general formula (I).

The repeating unit (isodecanoic acid unit) indicated.

Thus, by introducing an isophthalic acid unit, the obtained thermoplastic resin substrate can be excellent in extensibility. It is considered that by introducing an isononic acid unit, it is possible to impart a large deflection to the main chain, and it is possible to obtain crystallization by heat suppression. And a polyethylene phthalate resin which is aligned and crystallized during stretching.

The above poly(ethylene terephthalate) resin has the general formula (II) Repeated unit (for tannic acid unit) and general formula (III) The repeating unit (ethylene glycol unit) indicated.

The content ratio of the above-mentioned citric acid unit is preferably from 35 mol% to 50 mol%, more preferably from 40 mol% to 50 mol%, based on the total of the total repeat units. The content ratio of the above ethylene glycol unit is preferably from 35 mol% to 50 mol%, more preferably from 40 mol% to 50 mol%, based on the total of the total repeat units.

The content ratio of the above-mentioned isononanoic acid unit is preferably 0.5 mol% or more, more preferably 1 mol% or more, and still more preferably 3 mol% or more, based on the total of the total repeating units. On the other hand, the content ratio of the isononanoic acid unit is preferably 20 mol% or less, and preferably 10 mol% or less, based on the total of the total repeating units. By using such a polyethylene terephthalate-based resin, a thermoplastic resin substrate having excellent elongation can be obtained.

Preferably, the above polyethylene terephthalate resin has the formula (IV) [Chemical 7] The repeating unit (diethylene glycol unit) indicated.

Thus, by introducing a diethylene glycol unit, the obtained thermoplastic resin substrate can be excellent in extensibility.

The content ratio of the diethylene glycol unit is preferably from 0.1 mol% to 5 mol%, preferably from 0.5 mol% to 2 mol%, based on the total of the total repeat units.

As a method of producing the above polyethylene terephthalate resin, any appropriate method can be employed. For example, a method of dehydrating and shrinking citric acid, isophthalic acid, and diethylene glycol can be mentioned. The isophthalic acid unit may be contained in a random manner in the polyethylene terephthalate resin, or may be contained periodically.

The weight average molecular weight (Mw) of the above polyethylene terephthalate resin is preferably 30,000 to 200,000, more preferably 40,000 to 90,000. In the case of such a polyethylene terephthalate resin, the film can be formed by extrusion molding. The weight average molecular weight (Mw) is a molecular weight of converted polymethyl methacrylate (PMMA) measured by the following method.

GPC device: HLC-8120GPC (manufactured by TOSOH)

Sample pretreatment: The sample was weighed and a predetermined amount of the eluent was added and allowed to stand at room temperature overnight to dissolve. Subsequently, the sample after standing was slowly vibrated and mixed and filtered using a 0.5 μm PTF filter cartridge.

Calibration curve: A three-time approximation curve using a standard PMMA manufactured by Polymer Laboratories was used.

The thermoplastic resin substrate may contain any additives insofar as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, a plasticizer, a stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, and the like.

The water absorption of the thermoplastic resin substrate is preferably 0.2% or more, more preferably 0.3% or more. Such a thermoplastic resin substrate absorbs water in the step B described later, and the water can be plasticized by the action of a plasticizer. As a result, it is possible to greatly reduce the elongation stress, and it is possible to extend at a high magnification, and the elongation of the thermoplastic resin substrate can be excellent as compared with the air extension. As a result, a thin polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced. On the other hand, the water absorption of the thermoplastic resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a thermoplastic resin substrate, it is possible to prevent the dimensional stability of the thermoplastic resin substrate from being significantly lowered during production, resulting in deterioration of the appearance of the obtained thin polarizing film. Moreover, when extending in water, it is possible to prevent the base material from being broken or the PVA-based resin layer from being peeled off from the thermoplastic resin substrate. Further, the water absorption rate is a value obtained in accordance with JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 85 ° C or lower, more preferably 80 ° C or lower. By using such a thermoplastic resin substrate, it is possible to sufficiently ensure the elongation of the laminate while suppressing the crystallization of the PVA-based resin layer. On the other hand, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60 ° C or more, more preferably 70 ° C or more. By using such a thermoplastic resin substrate, the coating liquid containing the above PVA resin is applied. Prevents deformation of the thermoplastic resin substrate when dry The laminated body is favorably produced by a defect such as unevenness, sagging, wrinkles, or the like. Moreover, the extension of the PVA-based resin layer can be favorably performed at an appropriate temperature (for example, about 60 ° C). Further, the glass transition temperature (Tg) is a value obtained in accordance with JIS K 7121.

The thickness of the thermoplastic resin substrate before stretching is preferably 20 μm to 300 μm , more preferably 50 μm to 200 μm . When it is less than 20 μm , the formation of the PVA-based resin layer may become difficult. When it is more than 300 μm , in the step B, it is necessary for the thermoplastic resin substrate to absorb water for a long time, and at the same time, there is a possibility that an excessive load is required at the time of stretching.

Any suitable resin can be used for the PVA resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned. Polyethylene can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-ethyl acetate copolymer. The degree of deuteration 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 in accordance with JIS K 6726-1994. By using such a saponification degree PVA-based resin, a thin polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a possibility 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 1000 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 obtained in accordance with JIS K 6726-1994.

The coating liquid is typically a solution obtained by dissolving the PVA-based resin in a solvent. As a solvent, water, dimethyl arylene is mentioned, for example. Anthracene, dimethylformamide, dimethylacetamide N-methylpyrrolidone, various glycols, trimethylolpropane and other polyols, amines such as ethylenediamine and diethylenetriamine class. These may be used alone or in combination of two or more. Among these, water is preferred. The PVA-based resin concentration of the solution is preferably from 3 parts by weight to 20 parts by weight per 100 parts by weight of the solvent. When such a resin concentration is formed, a uniform coating film formed by adhering a thermoplastic resin substrate can be formed.

The additive may be formulated in the coating liquid, and examples of the additive include a plasticizer, a surfactant, and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As a surfactant, a nonionic surfactant is mentioned, for example. These can be used for the purpose of further improving the uniformity, dyeability, and extensibility of the obtained PVA-based resin layer.

As a coating method of a coating liquid, any appropriate method can be employ|adopted. 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 flow coating method, a spray coating method, a knife coating method (comma coating method, a doctor blade coating method, etc.).

Coating of the above coating liquid. The drying temperature is preferably 50 ° C or more.

The thickness of the PVA-based resin layer before stretching is preferably 3 μm to 20 μm .

Before the PVA-based resin layer is formed, a surface treatment (for example, corona treatment or the like) may be applied to the thermoplastic resin substrate, and an easy-adhesion layer may be formed on the thermoplastic resin substrate. By performing such a treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved.

A-2. Step B

In the above step B, the layered body is stretched in water (extension in boric acid water). By extending in water, it is possible to extend at a temperature lower than the glass transition temperature (about 80° C.) of the thermoplastic resin substrate and the PVA-based resin layer, and it is possible to suppress the crystallization of the PVA-based resin layer. The extension is performed at a high magnification. As a result, a thin polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

The method of extending the laminate can be any suitable method. Specifically, it may extend at a fixed end or may extend at a free end (for example, a method of uniaxially extending a laminated body between rolls of different peripheral speeds). The extension of the laminate can be carried out in one stage or in multiple stages. When the multi-stage is used, the stretching ratio (maximum stretching ratio) of the laminated body to be described later is the product of the stretching ratio at each stage.

The water extension system is preferably carried out by immersing the layered body in an aqueous boric acid solution (extension in boric acid water). By using an aqueous solution of boric acid as the stretching bath, it is possible to impart rigidity to the PVA-based resin layer which can withstand the tension applied during stretching and water-resistance to water. Specifically, boric acid can be crosslinked with a PVA-based resin by hydrogen bonding by forming a tetrahydroxyborate anion in an aqueous solution. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and the water can be favorably extended in water, and a thin polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or borate in water, that is, water. The boric acid concentration is preferably from 1 part by weight to 10 parts by weight per 100 parts by weight of water. By making boric acid concentration When it is 1 part by weight or more, the dissolution of the PVA-based resin molded body can be effectively suppressed, and a thin polarizing film having higher characteristics can be produced. Further, in addition to boric acid or borate, an aqueous solution obtained by dissolving glyoxal, glutaraldehyde or the like in a solvent can also be used.

In the case where a dichroic substance (typically iodine) is adsorbed to the PVA-based resin layer in advance by a dyeing step to be described later, it is preferred to formulate an iodide in the extension bath (aqueous boric acid solution). By dissolving the iodide, it is possible to suppress elution of iodine adsorbed by the PVA-based resin layer. 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, and titanium iodide. . Among these, potassium iodide is preferred. The concentration of the iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, per 100 parts by weight of water.

The extension temperature in step B (liquid temperature of the stretching bath) is preferably 40 ° C to 85 ° C, more preferably 50 ° C to 85 ° C. At such a temperature, it is possible to perform stretching at a high magnification while suppressing dissolution of the PVA-based resin. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is related to the formation of the PVA-based resin layer, and is preferably 60 ° C or higher. At this time, when the stretching temperature is lower than 40 ° C, the plasticization of the thermoplastic resin substrate using water may be considered, and there is a possibility that the film may not be well extended. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and the possibility that excellent optical characteristics are not obtained. The immersion time of the laminate in the extension bath is preferably from 15 seconds to 5 minutes.

By combining the above-mentioned thermoplastic resin substrate and water extension (boric acid water extension), it is possible to extend at a high magnification and to produce excellent light. A thin polarizing film that has characteristics (such as polarization). Specifically, the maximum stretching ratio is preferably 5.0 times or more with respect to the original length of the laminated body. In the present specification, the "maximum stretching ratio" refers to the stretching ratio when the laminated body is about to be broken, and refers to the stretching ratio at which the laminated body is broken, and is lower than the value by 0.2. Further, the maximum stretching ratio of the laminate using the above thermoplastic resin substrate is higher than that of the step of extending through the water as compared with the case of extending only in the air.

A-3. Other steps

The method for producing the thin polarizing film of the present invention may include other steps in addition to the above steps A and B. As another step, for example, an insolubilization step, a dyeing step, a crosslinking step, an additional stretching step in the above step B, a washing step, a drying (moisture adjusting rate) step, and the like can be given. Other steps can be performed at any suitable timing.

The insolubilization step is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. The water resistance of the PVA-based resin layer can be imparted by performing the insolubilization step. The concentration of the aqueous boric acid solution is preferably from 1 part by weight to 4 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilizing bath (aqueous boric acid solution) is preferably 20 ° C to 40 ° C. The insolubilization step is preferably carried out after the production of the laminate and before the dyeing step and step B.

The above dyeing step is typically a step of dyeing a PVA-based resin layer using a dichroic material. It is preferred to carry out the adsorption of the dichroic substance by the PVA-based resin layer. Examples of the adsorption method include a method of immersing a PVA-based resin layer (layered body) in a dyeing liquid containing a dichroic substance, a method of applying the dyeing liquid on a PVA-based resin layer, and a dyeing solution to PVA. A method in which a resin layer is sprayed or the like. A method of immersing the layered body in the dyeing liquid containing the dichroic substance is preferable because the dichroic substance can be adsorbed well.

Examples of the dichroic substance include iodine and a dichroic dye. Preferably it is iodine. When iodine is used as the dichroic substance, the above dyeing liquid is an aqueous iodine solution. The amount of iodine to be added is preferably 0.1 parts by weight to 0.5 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferred to formulate iodide in an aqueous iodine solution. Specific examples of the iodide are as described above. The amount of the iodide compounded is preferably 0.02 part by weight to 20 parts by weight, more preferably 0.1 part by weight to 10 parts by weight per 100 parts by weight of water. In order to suppress the dissolution of the PVA-based resin, the liquid temperature at the time of dyeing the dyeing liquid is preferably 20 ° C to 50 ° C. When the PVA-based resin layer is immersed in the dyeing liquid, the immersion time is preferably 5 seconds to 5 minutes in order to secure the transmittance of the PVA-based resin layer. Further, the dyeing conditions (concentration, liquid temperature, immersion time) can be set such that the degree of polarization or the monomer transmittance of the polarizing film finally obtained is within a predetermined range. In one embodiment, the immersion time is set such that the degree of polarization of the obtained polarizing film is 99.98% or more. In another embodiment, the immersion time is set such that the obtained single polarizing film has a single transmittance of 40% to 44%.

Preferably, the dyeing step is carried out before step B above.

The crosslinking step is typically carried out by impregnating a PVA-based resin layer with a boric acid aqueous 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 water, and further after the dyeing step. In the step of crosslinking, it is preferred to formulate iodide. By disposing the iodide, it is possible to suppress elution of iodine which has been adsorbed to the PVA-based resin layer. The amount of the iodide compounded is preferably from 1 part by weight to 5 parts by weight per 100 parts by weight of the water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20 to 50 ° C. Preferably, the crosslinking step is carried out before step B above. In a preferred embodiment, it can be carried out in accordance with the order of the dyeing step, the crosslinking step, and the step B.

As another extension step of the above step B, for example, a step of stretching the laminate at a high temperature (for example, 95 ° C or higher) in the air may be mentioned. This aerial extension step is preferably carried out prior to step B (extension in boric acid water) and the dyeing step. This aerial extension step is capable of positioning as a preliminary or auxiliary extension to the extension of boric acid water, hereinafter referred to as "airborne extension".

By combining the air-assisted extension, there is a case where the laminated body can be extended at a higher magnification. As a result, a thin polarizing film having more excellent optical characteristics (for example, a degree of polarization) can be produced. For example, when polyethylene terephthalate is used as the thermoplastic resin substrate, it is stretched in combination with the use of boric acid in water, and the combination of the airborne auxiliary extension and the boric acid water can be extended while suppressing the alignment of the thermoplastic resin substrate. When the thermoplastic resin substrate is improved in the alignment property, the stretching tension becomes large, which makes the elongation of stability difficult, or the thermoplastic resin substrate is broken. Therefore, the laminate can be stretched more at a higher rate while suppressing the elongation of the alignment of the thermoplastic resin substrate.

Further, by combining the air-assisted extension, the alignment of the PVA-based resin is improved, whereby the PVA can be made even after extending in boric acid water. The alignment of the resin is improved. Specifically, the orientation of the PVA-based resin is improved by the advance of the air-assisted extension, and the PVA-based resin and the boric acid are easily crosslinked when extended in boric acid water, and it is estimated that the state is extended by the state in which boric acid is a node. After extending in boric acid water, the alignment of the PVA resin is also increased. As a result, a thin polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

The extension method of the air-assisted extension is the same as the above-mentioned step B, and may be extended at the fixed end or extended at a free end (for example, a method of uniaxially extending the laminated body between rolls of different peripheral speeds). The extension system can be carried out in one stage or in multiple stages. When the multi-stage is used, the stretching ratio described later is the product of the stretching ratio at each stage. It is preferable that the extending direction of this step is substantially the same as the extending direction of the above step B.

The extension ratio in the air-assisted extension is preferably 3.5 times or less. The extension temperature of the air-assisted extension is preferably at least the glass transition temperature of the PVA-based resin. The elongation temperature is preferably from 95 ° C to 150 ° C. Further, when the airborne auxiliary stretching and the above-mentioned boric acid water are extended, the maximum stretching ratio is preferably 5.0 times or more, more preferably 5.5 times or more, and more preferably 6.0 times or more, relative to the original length of the laminated body.

The washing step is typically carried out by immersing the iodinated aqueous solution in a PVA-based resin layer. The drying temperature in the above drying step is preferably from 30 ° C to 100 ° C.

Fig. 2 is a schematic view showing an example of a method for producing a thin polarizing film of the present invention. The laminated body 10 is taken up from the unwinding portion 100, and after being immersed in the bath 110 of the boric acid aqueous solution by the rolls 111 and 112, (Insolubilization step), the rolls 121 and 122 are immersed in a bath 120 of an aqueous solution of a dichroic substance (iodine) and potassium iodide (dyeing step). Subsequently, it is immersed in a bath 130 of an aqueous solution of boric acid and potassium iodide by rolls 131 and 132 (crosslinking step). Subsequently, the laminated body 10 is immersed in the bath 140 of the boric acid aqueous solution, and the rolls 141 and 142 of different speed ratios are stretched in the longitudinal direction (longitudinal direction) to be stretched (step B). The layered body 10 subjected to the elongation treatment is immersed in a bath 150 of a potassium iodide aqueous solution by a roll 151 and 152 (washing step) and supplied to a drying step (not shown). Subsequently, it is taken up by the winding unit 160.

B. Thin polarizing film

The thin polarizing film of the present invention can be obtained by the above-described production method. The thin polarizing film of the present invention is substantially a PVA-based resin film in which a dichroic substance is adsorbed and aligned. The thickness of the thin polarizing film is preferably 10 μm or less, preferably 7 μm or less, more preferably 5 μm or less, and particularly preferably 0.5 μm to 5 μm . The thin polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The monomer transmittance of the thin polarizing film is preferably 40.0% or more, more preferably 41.0% or more, and still more preferably 42.0% or more. The polarizing film of the thin polarizing film is preferably 99.8% or more, more preferably 99.9% or more, and even more preferably 99.95% or more.

The method of using the above-mentioned thin polarizing film can employ any appropriate method. Specifically, it may be used in the same state as the thermoplastic resin described above, or may be used by transferring the thermoplastic resin substrate to another member.

C. Optical laminate

The optical layering system of the present invention has the above-mentioned thin polarizing film. 3(a) and (b) are schematic cross-sectional views showing an optical thin film laminate of a preferred embodiment of the present invention. The optical film laminate 100 has a thermoplastic resin substrate 11', a thin polarizing film 12', an adhesive layer 13, and a separator 14 in the following order. The optical film laminate 200 has a thermoplastic resin substrate 11', a thin polarizing film 12', an adhesive layer 15, an optical function polarizing film 16, an adhesive layer 13, and a separator 14 in the following order. In the present embodiment, the thermoplastic resin substrate described above is used as an optical member without being peeled off from the obtained thin polarizing film 12'. The thermoplastic resin substrate 11' can function as a protective film of the thin polarizing film 12'.

4(a) and 4(b) are schematic cross-sectional views showing an optical thin film laminate of another preferred embodiment of the present invention. The optical film laminate 300 has the separator 14, the adhesive layer 13, the thin polarizing film 12', the adhesive layer 15, and the optical function polarizing film 16 in the following order. In addition to the structure of the optical film laminate 300, the optical film laminate 400 is provided with the second optical function polarizing film 16' passing through the adhesive layer 13 between the thin polarizing film 12' and the separator 14. In the present embodiment, the thermoplastic resin substrate is removed.

The layers constituting the optical layered body of the present invention are not limited by the examples, and any appropriate adhesive layer or adhesive layer can be used. Representative of the adhesive layer is formed using an acrylic adhesive. The adhesive layer is typically formed using a vinyl alcohol-based adhesive. The optical functional film can have, for example, a function equivalent to a polarizing film protective film or a retardation film.

[Examples]

The invention is illustrated by the following examples, but the invention is not limited by the examples. Moreover, the measuring method of each characteristic is as follows.

Thickness

The measurement was carried out using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C").

2. Water absorption of thermoplastic resin substrate

The measurement was carried out in accordance with JIS K 7209.

3. Glass transition temperature (Tg) of thermoplastic resin substrate

The measurement was carried out in accordance with JIS K 7121.

4. Weight average molecular weight (Mw) of polyethylene terephthalate resin

GPC (manufactured by TOSOH, product name "HLC-8120GPC") was used for measurement and was expressed by converting the molecular weight of PMMA.

[Example 1]

(Step A)

As the thermoplastic resin substrate, a polyethylene terephthalate film having an isophthalic acid unit having a water absorption ratio of 0.75% and a Tg of 75 ° C was used (thickness: 100 μm, isodecanoic acid unit: 7 mol%, p-citric acid unit: 44 mol%) Ethylene glycol unit: 48 mol%, diethylene glycol unit: 1 mol%, weight average molecular weight (Mw): 72,000).

An aqueous solution of a polyvinyl alcohol (PVA) resin (manufactured by Nippon Synthetic Chemical Co., Ltd., trade name "Gohsenol (registered trademark) NH-26) having a degree of polymerization of 2,600 and a degree of saponification of 99.9% on one side of the thermoplastic resin substrate was 60. The coating was dried at ° C to form a PVA-based resin layer having a thickness of 7 μm . In this way, a laminate is produced.

The obtained laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C (a boric acid aqueous solution obtained by dispersing 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization step).

Subsequently, it was immersed in a dyeing bath at a liquid temperature of 30 ° C (an aqueous solution of iodine obtained by disposing 0.2 part by weight of iodine with respect to 100 parts by weight of water and blending 1.4 parts by weight of potassium iodide) for 60 seconds (dyeing step).

Subsequently, the mixture was immersed in a crosslinking bath at a liquid temperature of 30 ° C (a boric acid aqueous solution obtained by dispersing 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 step).

Subsequently, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 60 ° C (an aqueous solution obtained by dispersing 4 parts by weight of boric acid with 5 parts by weight of potassium iodide in 100 parts by weight of water) while passing between rolls of different peripheral speeds. The uniaxial extension is performed in the longitudinal direction (longitudinal direction) (step B). The immersion time in the aqueous boric acid solution was 120 seconds and extended until the laminate was about to break.

Subsequently, the laminate was immersed in a washing bath (an aqueous solution obtained by disposing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water), and then dried at 60 ° C in a warm air (washing and drying step).

In this manner, an optical film laminate in which a thin polarizing film was formed on a thermoplastic resin substrate was obtained.

(Comparative Example 1)

The laminate produced in the same manner as in Example 1 was stretched in the air at 100 ° C until the laminate was about to be broken. The stretching ratio (maximum stretching ratio) at this time was 4.5 times.

Subsequently, in the same manner as in Example 1, a thin polarizing film obtained by drying in a warm air at 60 ° C after the dyeing step, the crosslinking step, and the washing step were carried out in the following order. The thickness of the obtained thin polarizing film was 4 μm .

[Example 2-1]

In addition to the thermoplastic resin substrate, a polyethylene terephthalate film having a water absorption ratio of 0.75% and a Tg of 72 ° C having an isophthalic acid unit (manufactured by Bell Polyester Products, trade name "PIFG5H", thickness: 200 μm, was used. The same amount as in Example 1 except that the isononanoic acid unit: 3 mol%, p-citric acid unit: 48 mol%, ethylene glycol unit: 48 mol%, diethylene glycol unit: 1 mol%, weight average molecular weight (Mw): 59,000) The film was formed to obtain a thin polarizing film.

[Example 2-2]

(Step A)

On one surface of the thermoplastic resin substrate used in Example 2-1, an aqueous solution having a polymerization degree of 4,200 and a saponification degree of 99.2% of PVA resin powder dissolved in water was applied in an amount of 4 to 5% by weight, and 50% was applied thereto. The laminate was dried at a temperature of 60 ° C to form a PVA-based resin layer having a thickness of 9 μm to produce a laminate.

The obtained laminate was subjected to a uniaxial extension of the free end 2.0 times in the longitudinal direction (longitudinal direction) between rolls of different peripheral speeds in an oven at 130 ° C (air assisted extension step).

Subsequently, the layer body was immersed in an insolubilizing bath at a liquid temperature of 30 ° C (a boric acid aqueous solution obtained by dispersing 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization step).

Subsequently, a liquid dye containing potassium iodide at a liquid temperature of 30 ° C with an iodine concentration of 0.12 to 0.25 wt% is used to obtain a monomer transmittance of the polarizing film finally obtained. 42.8% of the way to make it dipped (dyeing step). Here, the ratio of iodine to potassium iodide is 1:7.

Subsequently, the mixture was immersed for 60 seconds in a crosslinking bath having a liquid temperature of 40 ° C (a boric acid aqueous solution obtained by dispersing 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 step).

Subsequently, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 75 ° C (an aqueous solution obtained by dispersing 4 parts by weight of boric acid with 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) while passing between rolls of different peripheral speeds. The free end uniaxial extension is performed in the longitudinal direction (longitudinal direction) (step B). The immersion time in the aqueous boric acid solution was 120 seconds and extended until the laminate was about to break.

Subsequently, the laminate was immersed in a washing bath (an aqueous solution obtained by disposing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water), and then dried at 60 ° C in a warm air (washing and drying step).

In this manner, an optical film laminate in which a thin polarizing film was formed on a thermoplastic resin substrate was obtained.

(Comparative Example 2)

The laminate produced in the same manner as in Example 2 was stretched in the air in an oven at 100 ° C until the laminate was about to be broken. The stretching ratio (maximum stretching ratio) at this time was 4.5 times.

Subsequently, in the same manner as in Example 2, a thin polarizing film obtained by drying in a warm air at 60 ° C after the dyeing step, the crosslinking step, and the washing step were carried out in the following order. The thickness of the obtained thin polarizing film was 4 μm .

[Example 3]

In addition to being a thermoplastic resin substrate, the water absorption rate is 0.75%, Tg72 Polyethylene terephthalate film having an isophthalic acid unit at °C (manufactured by Bell Polyester Products, trade name "PIFG5", thickness: 200 μm, isodecanoic acid unit: 3 mol%, p-citric acid unit: 48 mol% A thin polarizing film was obtained in the same manner as in Example 1 except that the ethylene glycol unit: 48 mol%, diethylene glycol unit: 1 mol%, and weight average molecular weight (Mw): 55,000).

(Comparative Example 3)

The laminate produced in the same manner as in Example 3 was stretched in the air in an oven at 100 ° C until the laminate was about to be broken. The stretching ratio (maximum stretching ratio) at this time was 4.5 times.

Subsequently, in the same manner as in Example 1, a thin polarizing film obtained by drying in a warm air at 60 ° C after the dyeing step, the crosslinking step, and the washing step were carried out in the following order. The thickness of the obtained thin polarizing film was 4 μm .

[Example 4]

In addition to the thermoplastic resin substrate, a polyethylene terephthalate film having a water absorption ratio of 0.75% and a Tg of 72 ° C having an isophthalic acid unit (manufactured by Bell Polyester Products, trade name "PIFG30", thickness: 200 μm, The same amount as in Example 1 except that the isononanoic acid unit: 6 mol%, p-citric acid unit: 45 mol%, ethylene glycol unit: 48 mol%, diethylene glycol unit: 1 mol%, weight average molecular weight (Mw): 52,000) The film was formed to obtain a thin polarizing film.

(Comparative Example 4)

The laminate produced in the same manner as in Example 4 was stretched in the air in an oven at 100 ° C until the laminate was about to be broken. The stretching ratio (maximum stretching ratio) at this time was 4.5 times.

Subsequently, in the same manner as in Example 4, a thin polarizing film obtained by drying in a warm air at 60 ° C after the dyeing step, the crosslinking step, and the washing step were carried out in the following order. The thickness of the obtained thin polarizing film was 4 μm .

[Comparative Example 5-1]

In addition to the thermoplastic resin substrate, a polyethylene terephthalate (PET) film having a water absorption of 0.1% and a Tg of 110 ° C (manufactured by Teijin DuPont Co., Ltd., trade name "Teijin Tetoron G2", thickness: 100 μm, weight average molecular weight ( Mw): 39,000) and the temperature of the boric acid aqueous solution were set to 80 ° C, and the laminate was tried in the same manner as in Example 1, but the laminate was not extended at all.

(Comparative Example 5-2)

The laminate produced in the same manner as in Example 5-1 was stretched in the air in an oven at 130 ° C until the laminate was about to be broken. The stretching ratio (maximum stretching ratio) at this time was 2.0 times.

Subsequently, in the same manner as in Comparative Example 5-1, a thin polarizing film obtained by drying in a warm air at 60 ° C after the dyeing step, the crosslinking step, and the washing step was carried out in the following order. The thickness of the obtained thin polarizing film was 5 μm .

(Reference example)

In addition to the thermoplastic resin substrate, an amorphous polyethylene terephthalate (A-PET) film having a water absorption of 0.60% and a Tg of 80 ° C (manufactured by Mitsubishi Plastics Co., Ltd., trade name "NOVACLEAR", thickness: 100 μm, weight) was used. A laminate polyester film was obtained in the same manner as in Example 1 except that the average molecular weight (Mw): 20,000).

In each of the examples and comparative examples, the extended product was visually observed. The appearance of the layer. The evaluation results are shown in Table 1 together with the maximum stretching ratio. Further, the stretching ratio of Example 2-2 includes the total stretching ratio of the air-assisted extension.

(Evaluation criteria for appearance)

○: Good.

X: The appearance was poor due to unevenness, sagging, deformation, and dimensional change.

The degree of polarization of the thin polarizing film obtained in each of the examples and the comparative examples was measured. The method of measuring the degree of polarization is as follows. The measurement results are shown in Table 1 together with the thickness of the obtained thin polarizing film.

(Method for measuring the degree of polarization)

The transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) of the thin polarizing film were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and Determine the degree of polarization (P).

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

Further, the above Ts, Tp, and Tc are Y values measured by a 2 degree field of view (C light source) of JIS Z 8701 and corrected for visual sensitivity.

In Examples 1 to 4, a thin polarizing film having a very excellent single transmittance and a degree of polarization can be produced.

Industrial availability

The thin polarizing film of the present invention has higher polarizing performance than the prior thin polarizing film. Therefore, according to the present invention, a thin polarizing film can be widely applied to a liquid crystal television, a liquid crystal display, a mobile phone, a digital camera, a video camera, a portable game machine, a car navigator, a photocopying machine, a printer, and a fax. A liquid crystal panel such as a machine, a clock, or an electric furnace.

Claims (1)

A laminate comprising: a thermoplastic resin substrate composed of a polyethylene terephthalate resin, and the polyethylene terephthalate resin has a repeating unit represented by the formula (I) The content of the isononanoic acid unit is 0.5 mol% or more based on the total of the total repeating units; And a polyvinyl alcohol-based resin layer formed on the thermoplastic resin substrate.