JP2010250080A - Optical member, manufacturing method thereof, and liquid crystal using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical member composed of a polyvinyl alcohol resin film, which is subjected to cross-linking treatment so as to have a low deformation shrinkage ratio, even at a high temperature and has high optical characteristics, and to provide a manufacturing method thereof, and a liquid crystal device using the optical member. <P>SOLUTION: The optical member 11 is composed of a polyvinyl alcohol resin cross-linked and fixed by using a boron, wherein the ratio of a peak intensity height I(OH) derived from stretching vibrations of an OH group, coupled to carbon of a main chain at a wavenumber of about 3,322 cm<SP>-1</SP>to a peak intensity height I(CH<SB>2</SB>) derived from stretching vibrations of a CH<SB>2</SB>group, in a carbon chain of the main chain at a wavenumber of about 2,914 cm<SP>-1</SP>in an infrared absorption spectrum is ≤1.05. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical member such as a polarizing film used in a liquid crystal device or the like, a method for producing the same, and a display device using the same.

  The liquid crystal device is configured by arranging a pair of polarizing plates so as to sandwich a liquid crystal cell. The polarizing plate is configured by, for example, laminating a protective film such as a TAC (triacetyl cellulose) film on a polarizing film as an optical member formed by adsorbing iodine or the like on a polyvinyl alcohol (PVA) resin.

  In general, a polarizing film is produced by dyeing, stretching, and fixing a PVA substrate. The PVA substrate has an amorphous region and a crystal region. First, iodine ions are adsorbed on the PVA substrate by dyeing. Next, by stretching, the amorphous region of the PVA substrate is reduced and the crystal region is expanded, and further, the crystal region is aligned along the stretching direction, and accordingly, the iodine ions adsorbed on the PVA substrate are also in the stretching direction. line up. Since the light passing through the polarizing film is absorbed by the iodine ions, a polarizing film having polarization characteristics can be obtained. After stretching, cross-linking with boric acid is performed to fix the molecules in the PVA substrate.

  Since the PVA-based resin has a hydroxyl group (OH group), the polarizing film is likely to undergo dimensional deformation due to heat or moisture, and the optical characteristics are likely to deteriorate. On the other hand, in order to improve the moisture resistance of the polarizing film, a polarizing film is produced by impregnating and adsorbing the polarizing element in a polymer film having a low hygroscopic property and a low photoelastic coefficient such as polyethylene terephthalate in a supercritical state. It has been proposed (see, for example, Patent Document 1). In addition, for the purpose of improving the water resistance of polyvinyl alcohol, there is a report of acylating a hydroxyl group of a film substrate (see Non-Patent Document 1).

JP 2002-350636 A (paragraphs [0014] and [0053])

The 46th Annual Meeting of the Adhesion Society of Japan 109-P. 110 (2008)

  However, in patent document 1, although the problem with respect to moisture resistance is solved by using another polymer film instead of a PVA-type film, in the case of using a PVA base material, the moisture resistance and the deformation | transformation by heat, Furthermore, There is no mention of cross-linking between PVA molecules. Further, in Non-Patent Document 1, although water resistance is improved by acylating a hydroxyl group, there is no mention of deformation due to heat or cross-linking fixation between molecules in a PVA resin.

  In view of the circumstances as described above, an object of the present invention is to provide an optical member comprising a polyvinyl alcohol-based resin film having high optical properties that has been subjected to crosslinking treatment so that the deformation shrinkage rate becomes low even at high temperatures, a method for producing the same, and the method thereof. It is an object to provide a liquid crystal device using this.

In order to achieve the above object, an optical member according to an embodiment of the present invention is made of a polyvinyl alcohol-based resin that is cross-linked and fixed using boron. The optical member has a peak intensity height I (OH) derived from stretching vibration of an OH group bonded to carbon of the main chain in the vicinity of a wave number of 3322 cm ⁻¹ in an infrared absorption spectrum as a first peak intensity height, and a wave number of 2914 cm. ^When the peak intensity height I (CH ₂ ) derived from the CH ₂ group stretching vibration of the carbon chain of the main chain in the vicinity of ⁻¹ is defined as the second peak intensity height, the first peak intensity height described above The ratio to the second peak intensity height is in the range of 1.05 or less.

By setting the I (OH) / I (CH ₂ ) intensity ratio to 1.05 or less, that is, by reducing the abundance of OH groups, an optical member having a small dimensional expansion / contraction change at high temperatures can be obtained. When a liquid crystal device is manufactured by providing such an optical member inside the liquid crystal cell, the dimensional expansion / contraction change rate of the optical member can be kept small even during high-temperature processing during the liquid crystal cell manufacturing process, and the characteristics of the optical member deteriorate. Is suppressed, and a liquid crystal device having excellent display characteristics can be obtained.

  The polyvinyl alcohol resin is impregnated with a dichroic dye.

  Thus, an optical member having polarization characteristics can be obtained by impregnating the optical member with the dichroic dye.

  The manufacturing method of the optical member which concerns on one form of this invention includes processing polyvinyl alcohol-type resin with the crosslinking material containing a boric acid under the medium of a supercritical state. The said polyvinyl alcohol-type resin is heat-processed at the temperature of 100 degreeC or more and 130 degrees C or less after the said process.

According to the above method for producing an optical member, by treating a polyvinyl alcohol resin with a crosslinking material in a supercritical atmosphere, water contained in the portion where the intermolecular voids in the polyvinyl alcohol resin are narrowed is removed. Further, the cross-linking material is impregnated. By heat-treating this at a high temperature of 100 ° C. or more and 130 ° C. or less, the uncrosslinked OH group bonded to the carbon of the main chain of the polyvinyl alcohol resin reacts with the crosslinking material, and the polyvinyl alcohol molecules are crosslinked. Fixed. As a result, the I (OH) / I (CH ₂ ) strength ratio of the optical member can be made 1.05 or less, and it is crosslinked to the inside of the polyvinyl alcohol-based resin, and is resistant to deformation even under high temperature and high humidity. Can be obtained. In addition, I (OH) is the peak intensity height derived from the stretching vibration of the OH group bonded to the main chain carbon in the vicinity of a wave number of 3322 cm ⁻¹ in the infrared absorption spectrum of the polyvinyl alcohol resin. I (CH ₂ ) is a peak intensity height I derived from the CH ₂ group stretching vibration of the main chain carbon chain in the vicinity of a wave number of 2914 cm ⁻¹ in the infrared absorption spectrum of the polyvinyl alcohol resin.

  The medium is carbon dioxide.

  In this way, treatment in a supercritical carbon dioxide atmosphere is possible.

  The polyvinyl alcohol-based resin is dried before the heat treatment and before or after the treatment with the cross-linking material containing boric acid under the supercritical medium.

  Thus, by providing a drying process, the contained water which exists in the part where the space | gap between the film surface and molecule | numerator is wide is removed. And the contained water which exists in the part where the space | gap between the molecules which cannot be removed in this drying process is narrow is removed by the process in a supercritical atmosphere, and a high temperature heat processing.

A liquid crystal device according to one embodiment of the present invention includes a first substrate, a second substrate, a liquid crystal, and an optical member.
The first and second substrates are spaced apart from each other. The liquid crystal is sandwiched between the first substrate and the second substrate. The optical member is disposed on one surface of each of the first substrate and the second substrate. The optical member is made of a polyvinyl alcohol resin that is cross-linked and fixed using boron and impregnated with a dichroic dye. The optical member, the peak intensity derived from the stretching vibration of the -OH group attached to the carbon of the main chain in the vicinity of a wave number 3322cm ^-1 in the infrared absorption spectrum height I a (OH) a first peak strength and high Satoshi, When the peak intensity height I (CH ₂ ) derived from the —CH ₂ — group stretching vibration of the main chain carbon chain near the wave number of 2914 cm ⁻¹ is defined as the second peak intensity height, the first peak intensity high The ratio of the height to the second peak intensity height is in the range of 1.05 or less.

By setting the I (OH) / I (CH ₂ ) intensity ratio of the optical member to 1.05 or less, that is, by reducing the residual ratio of OH groups, an optical member having a small dimensional expansion / contraction change at high temperatures can be obtained. . Therefore, it is possible to obtain a liquid crystal device including an optical member in which changes in optical characteristics are suppressed even under high temperature and high humidity, and a liquid crystal device having stable display characteristics can be obtained.

  The optical member is provided on the liquid crystal side surface of each of the first substrate and the second substrate.

  As described above, the optical member can be arranged on the liquid crystal side surface of the substrate of the liquid crystal device. Since this liquid crystal device includes an optical member that has a small dimensional expansion / contraction change at high temperatures, the dimensional expansion / contraction change rate of the optical member can be kept small even during high temperature processing during the manufacturing process of the liquid crystal device. A liquid crystal device which is suppressed and has excellent display characteristics can be obtained.

  As described above, according to the present invention, an optical member having a small dimensional expansion / contraction change rate at a high temperature can be obtained.

It is a figure which shows the infrared absorption spectrum characteristic of the polarizing film which concerns on embodiment and comparative example of this invention. The basic structure in the molecular level in the supercritical carbon dioxide bridge | crosslinking treatment process and high temperature annealing process of the polarizing film which concerns on embodiment of this invention is shown. It is a flowchart figure which shows the manufacturing method of the polarizing film which concerns on one Embodiment of this invention. It is a figure which shows the supercritical system used at the time of a supercritical carbon dioxide bridge | crosslinking treatment process among the manufacturing methods shown in FIG. It is a schematic sectional drawing of the liquid crystal device provided with the polarizing film of this invention. (A) shows the change of storage elastic modulus (E ′) with respect to the temperature rise of the polarizing film according to the first embodiment, the second embodiment, and Comparative Example 1 and the change of tan δ indicating the occurrence state of local molecular motion, (B) shows the sample length change of the polarizing film which concerns on 1st Embodiment, 2nd Embodiment, and the comparative example 1. FIG. Based on the data of the dimensional expansion / contraction change rate with the temperature rise of the polarizing film according to each embodiment and the comparative example, the dimensional expansion / contraction change rate at 130 ° C. and 150 ° C. is obtained by using the parameter I ( The plot is made against the intensity ratio of (OH) / I (CH ₂ ). It is a flowchart figure which shows the manufacturing method of the polarizing film which concerns on other embodiment. It is a flowchart figure which shows the manufacturing method of the polarizing film which concerns on other embodiment.

  Hereinafter, a polarizing film as an optical member according to an embodiment of the present invention will be described with reference to the drawings. The polarizing film of the present invention can be used, for example, as a polarizing plate for a liquid crystal device.

The polarizing film of the present invention is made of a polyvinyl alcohol-based resin, and is characterized in that it is produced by crosslinking treatment in a supercritical atmosphere at the time of production and high-temperature annealing treatment. By performing the crosslinking treatment in the supercritical atmosphere as described above, the crosslinking can be advanced to a crosslinked state that cannot be realized under the conventional manufacturing conditions in which the supercritical atmosphere crosslinking treatment is not performed. In the present embodiment, the polyvinyl alcohol resin is treated with a cross-linking material made of a solution containing boric acid in a supercritical atmosphere, and then subjected to a high temperature annealing treatment (high temperature heat treatment), whereby the polyvinyl alcohol resin is treated with boron. A part of the hydroxyl group inside can be crosslinked. In the infrared absorption spectrum of the polarizing film according to the present embodiment, the peak intensity high I (OH) derived from the stretching vibration of the hydroxyl group (OH group) and the peak intensity high derived from the methylene group (CH ₂ group) stretching vibration. The ratio to I (CH ₂ ) is in the range of 1.05 or less. Thus, by reducing the residual ratio of OH groups in the polarizing film, it is possible to obtain a polarizing film having excellent durability that is difficult to shrink and deform even under a heat load of about a few hundred degrees. In addition, I (OH) is the peak intensity height derived from the stretching vibration of the OH group bonded to the carbon of the main chain of the polyvinyl alcohol resin near the wave number of 3322 cm ⁻¹ . I (CH ₂ ) is the peak intensity height derived from the CH ₂ group stretching vibration of the carbon chain of the polyvinyl alcohol-based resin main chain in the vicinity of a wave number of 2914 cm ⁻¹ .

  FIG. 1 is a diagram showing infrared absorption spectrum characteristics of a polarizing film as an optical member according to an embodiment of the present invention and a comparative example, and a first embodiment and a second embodiment manufactured by a manufacturing method described later. The characteristics of the polarizing film of Comparative Example 1 are shown. In FIG. 1, the Fourier transform infrared absorption spectrum of the surface of the polarizing film was determined by the ATR (Attenuated Total Reflection) method. FIG. 2 shows a basic structure at a molecular level when manufacturing a polarizing film according to an embodiment of the present invention. FIG. 3 is a flowchart showing a method for manufacturing a polarizing film according to an embodiment of the present invention. FIG. 4 is a diagram showing a supercritical system used in the supercritical carbon dioxide crosslinking treatment step in the manufacturing method shown in FIG.

[Production method of polarizing film]
First, the manufacturing method of the polarizing film which concerns on embodiment is demonstrated using FIG.3 and FIG.4.

  First, after a polyvinyl alcohol-based resin film (PVA base material) is installed and fixed on a manual uniaxial stretching machine, it is swollen in pure water at 35 ° C. for 3 minutes (swelling step, S1). Examples of the polyvinyl alcohol-based resin film include a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, a poly (ethylene-vinyl acetate) copolymer film, a partially saponified or completely saponified film thereof, and a partial polyeneization of polyvinyl alcohol. A film or the like can be used. When a copolymer film is used, the degree of polymerization is not particularly limited, but the degree of polymerization is preferably in the range of 1500 to 3000 in order to obtain high optical properties. In the case of using a partially saponified film or a fully saponified film, the saponification degree is not particularly limited, but it is desirable that the saponification degree range is 98 to 100 mol% in order to obtain high optical properties. In this embodiment, a commercially available atactic PVA (polyvinyl alcohol) resin film (polymerization degree: 2400, saponification degree: 99%, film thickness: 75 μm) was used. In addition, the thickness of a film is not specifically limited, either, A film about 50-150 micrometers can be used.

  A swelling process swells a film as pre-processing of the extending process mentioned later. The solvent used for swelling is not particularly limited, and a solvent used in a swelling step in a normal method for producing a polarizing film can be used. For example, as the solvent used in the swelling process, pure water, an aqueous potassium iodide solution, or the like can be used. In this embodiment, pure water was used because of the ease of swelling. The liquid temperature of the swelling bath is not particularly limited, and can be arbitrarily set according to the thickness of the film and the type of the solvent. For example, the temperature is set to 20 ° C. or higher and 45 ° C. or lower, and in this embodiment, 35 ° C. In the present embodiment, the swelling step (S1) is provided, but the swelling process may not be performed and the swelling process may be performed in the subsequent dyeing process.

  Next, the swollen polyvinyl alcohol-based resin film is immersed in an aqueous dye solution, and the film is dyed (dyeing step, S2). In this embodiment, a mixed aqueous solution having iodine / potassium iodide and boric acid weight concentrations of 0.02 wt% / 3.0 wt% and 3.0 wt%, respectively, was used as the dyeing aqueous solution. The dye used for dyeing is not particularly limited as long as it is a dichroic substance, and dyes used in the dyeing process in a normal method for producing a polarizing film can be used. For example, iodine, red R, or the like can be used. As the dyeing aqueous solution, a mixed aqueous solution of iodine, potassium iodide, and boric acid can be used as described above. The weight concentrations of iodine, potassium iodide, and boric acid are in the range of 0.015 wt% to 0.025 wt%, 1.5 wt% to 4.0 wt%, and 1.0 wt% to 3.0 wt%, respectively. It is preferable that Further, the temperature of the dyeing aqueous solution, the immersion time, etc. may be appropriately set in consideration of the relationship with the film material and other processes. In this embodiment, the temperature of the dyeing aqueous solution is set to 25 ° C. or more and 35 ° C. or less.

  Next, the polyvinyl alcohol-based resin film is lifted from the dyeing bath, and the polyvinyl alcohol-based resin film is immersed in a stretching aqueous solution for 5 minutes in order to impart polarization characteristics to the polyvinyl alcohol-based resin film (stretching step, S3). The draw ratio is not particularly limited, and can be set as appropriate so as to impart the desired polarization characteristics. In the present embodiment, the draw ratio is 6 times that of the film before swelling.

  In the stretching step, various stretching methods such as wet stretching and dry stretching can be employed. In this embodiment, wet stretching is adopted. When performing wet extending | stretching, the aqueous solution of a extending | stretching bath is not specifically limited, The aqueous solution used at the extending | stretching process in manufacture of a normal polarizing film can be used. For example, a mixed aqueous solution composed of potassium iodide and boric acid can be used. In this case, the concentrations of potassium iodide and boric acid are not particularly limited and can be set as appropriate. Potassium iodide is 2.0 wt% to 4.0 wt%, boric acid is 2.5 wt% to 4.0 wt%. In this embodiment, a mixed aqueous solution in which the weight concentrations of potassium iodide and boric acid are 3.0 wt% is used. Further, the temperature of the aqueous solution of the stretching bath can be appropriately set in consideration of the relationship with the film material and other processes. In the present embodiment, the temperature is set to 45 ° C. or more and 60 ° C. or less.

  Next, the polyvinyl alcohol-based resin film stretched at a predetermined magnification is immersed in a crosslinking step bath to be crosslinked and fixed (crosslinking and fixing step, S4). The aqueous solution of the cross-linking immobilization bath is not particularly limited, and an aqueous solution used in the cross-linking immobilization step in the production of a normal polarizing film can be used. For example, a mixed aqueous solution composed of potassium iodide, boric acid and zinc chloride can be used. In this case, the concentrations of potassium iodide, boric acid and zinc chloride are not particularly limited and can be set as appropriate. For example, potassium iodide is 2.0 wt% to 4.0 wt%, and boric acid is 1.0 wt% to 4 wt. 0.0 wt% and zinc chloride can be in the range of 1.0 wt% to 2.0 wt%. In this embodiment, a mixed aqueous solution of potassium iodide 2.5 wt%, boric acid 2.5 wt%, and zinc chloride 1.0 wt% was used. The temperature of the aqueous solution of the cross-linking immobilization bath can be appropriately set in consideration of the relationship with the material of the film and other processes. In the present embodiment, the temperature is set to 30 ° C. or higher and 45 ° C. or lower.

  Next, after crosslinking and fixing, the polyvinyl alcohol-based resin film is pulled up from the crosslinking and fixing bath, and the polarizing film is dried in a drying facility at 60 ° C. for 30 minutes (drying step, S5). Thereby, the removal of the contained water in the surface of a polarizing film and the part where the space | gap between molecules is wide can be performed. The drying temperature and drying time in the drying step can be appropriately set in consideration of the relationship with the material of the film and other steps.

Next, the polyvinyl alcohol-based resin film is taken out from the drying facility and cut into a sheet to obtain a polarizing film sheet. This polarizing film sheet, using supercritical carbon dioxide fluid extraction system 100 shown in FIG. 4, the cross-linking process is performed under the supercritical carbon dioxide atmosphere (supercritical CO ₂ crosslinking treatment step, S6). This supercritical carbon dioxide (CO ₂ ) crosslinking step is a step of removing the contained water stretched in the stretching step and sandwiched between intermolecular voids in a supercritical atmosphere, and additionally introducing a crosslinking material.

  Here, the supercritical carbon dioxide fluid extraction system 100 used in the supercritical carbon dioxide crosslinking treatment step will be described with reference to FIG. The supercritical carbon dioxide fluid extraction system 100 is a device that performs a crosslinking treatment in a supercritical carbon dioxide atmosphere.

  As shown in FIG. 4, the supercritical carbon dioxide fluid extraction system 100 includes a pressure resistant chamber 107, a cross-linking material solution storage unit 102, a carbon dioxide cylinder 101, conduits 103, 104, 111 to 113, and a pressurizing unit 105. , 106, constant temperature bath 108, decompression adjusting unit 109, gas-liquid separation bath 110, valves 121 to 125, and pressure gauge 131.

  The pressure-resistant chamber 107 accommodates a polarizing film sheet to be processed. The pressure chamber 107 is temperature-controlled by a thermostatic chamber 108, the pressure in the pressure chamber 107 can be controlled, and the pressure gauge 131 is designed to check the pressure in the pressure chamber 107.

  Carbon dioxide, which is a medium, is accommodated in a carbon dioxide cylinder 101, which is a supply source of carbon dioxide fluid. In the cross-linking material solution storage unit 102, boric acid ethanol obtained by dissolving boric acid as a cross-linking material in ethanol is stored as an additive solution. In this embodiment, 8.7 wt% ethanolic borate was used as the additive solution.

  The cross-linking material solution storage unit 102 and the pressure-resistant chamber 107 are connected to each other via a conduit 104 and a conduit 112 so that the boric acid ethanol in the cross-linking material solution storage unit 102 can flow into the pressure-resistant chamber 107. In the middle of the conduit 104, a pressurizing unit 106 for pressurizing ethanol borate and a valve 123 for adjusting the amount of borate ethanol flowing into the pressure resistant chamber 107 are provided.

  The carbon dioxide cylinder 101 and the pressure resistant chamber 107 are connected to each other via a conduit 103 and a conduit 112, and the carbon dioxide in the carbon dioxide cylinder 101 is designed to flow into the pressure resistant chamber 107. In the middle of the conduit 103, a pressurizing unit 105 that pressurizes carbon dioxide to form supercritical carbon dioxide, a valve 121 that adjusts the amount of carbon dioxide from the carbon dioxide cylinder 101 that flows into the pressurizing unit 105, and a pressure-resistant chamber 107. A valve 122 for adjusting the amount of supercritical carbon dioxide supplied inside is provided.

  The conduit 104 and the conduit 103 are connected to the conduit 112, and the amount of borate ethanol and / or supercritical carbon dioxide flowing into the pressure resistant chamber 107 is adjusted by a valve 124 provided in the middle of the conduit 112.

  The decompression adjusting unit 109 adjusts the inside of the pressure resistant chamber 107 to a decompressed state in order to discharge the supercritical carbon dioxide fluid in the pressure resistant chamber 107 to the outside of the pressure resistant chamber 107. The conduit 113 connecting the pressure-resistant chamber 107 and the decompression adjusting unit 109 is provided with a valve 125, and the discharge of the supercritical carbon dioxide fluid in the pressure-resistant chamber 107 is controlled by the valve 125.

  The gas-liquid separation tank 110 performs gas-liquid separation of the supercritical carbon dioxide fluid discharged out of the pressure resistant chamber 107. The carbon dioxide gas that has become gas in the gas-liquid separation tank 110 is supplied to the carbon dioxide cylinder 102 through the conduit 111 and reused.

Next, the supercritical CO ₂ cross-linking process (S6) using the supercritical carbon dioxide fluid extraction system 100 described above will be described.

  First, a polarizing film sheet (not shown) to be processed is placed in the pressure resistant chamber 107 in advance. After supplying 8.7 wt% boric acid ethanol addition solution from the cross-linking material solution storage unit 102 into the pressure chamber 107, supercritical dioxide is supplied from the carbon dioxide cylinder 101 and pressurized by the pressurization unit 105. Supply carbon.

  The boric acid ethanol addition solution used as a cross-linking material was supplied so as to be about 1/3 to 1/2 of the volume of the pressure-resistant chamber 107. The temperature in the pressure-resistant chamber 107 was adjusted so that the ambient temperature of the polarizing film sheet was 50 ° C. and the ambient pressure was 10 MPa. Thereby, the inside of the pressure-resistant chamber 107 is maintained in a supercritical carbon dioxide atmosphere.

  Under such conditions, the polarizing film sheet was immersed for 2 hours. After the immersion, the inside of the pressure-resistant chamber 107 is depressurized to release the pressurized state to an atmospheric pressure state. Thereby, the contained water in the portion where the intermolecular voids in the polarizing film are narrowed is removed, and a polarizing film additionally impregnated with the crosslinking material can be obtained.

This polarizing film has a structure in which a crosslinking material is impregnated into the inside of the film, and as shown in FIG. 2A, B (OH) ₄ ⁻ exists between the molecules of the polyvinyl alcohol-based resin.

  Next, the polarizing film additionally impregnated with the cross-linking material is taken out from the supercritical carbon dioxide fluid extraction system 100 and left in an air oven at 100 ° C. for 30 minutes to perform high temperature annealing (high temperature heat treatment) (high temperature annealing). The polarizing film of 1st Embodiment was obtained by returning a process, S7), and room temperature. In this embodiment, the high-temperature annealing process is performed under atmospheric pressure, but it may be performed under vacuum, or the supercritical carbon dioxide fluid extraction system may be designed so that the high-temperature annealing process can be performed in the pressure resistant chamber. Good. By performing the high temperature annealing treatment in this way, the uncrosslinked OH group bonded to the carbon of the main chain of the polyvinyl alcohol resin reacts with the cross-linking material, and B (boron) as shown in FIG. By this, the polyvinyl alcohol molecules are cross-linked and fixed.

  In this embodiment, the film can be cross-linked by impregnating with a cross-linking material in a supercritical atmosphere, and a polarizing film excellent in durability that is not easily deformed even under high temperature and high humidity can be obtained. That is, when impregnated with a cross-linking material under non-supercritical conditions, only the film surface is cross-linked and the cross-linking does not proceed to the inside of the film. If such a film is kept at a high temperature, the film is deformed and the polarization characteristics deteriorate. Resulting in. In contrast, the polarizing film of the present embodiment is cross-linked and fixed to the inside of the film, and the local molecular motion related to the dimensional stability of the film is greatly regulated, so that deformation of the film at high temperatures is suppressed, and the polarizing property Deterioration is prevented.

  In this embodiment, after performing drying process S5, supercritical carbon dioxide bridge | crosslinking process S6 and high temperature annealing process S7 are performed. In the drying step S5, the contained water is removed from the film surface and the portions where the intermolecular voids are wide. And the contained water which exists in the part where the space | gap between the molecules which cannot be removed by this drying process S5 is narrow is removed by supercritical carbon dioxide bridge | crosslinking process S6 and high temperature annealing process S7.

  The manufacturing method of the polarizing film according to the second embodiment is different from the manufacturing method of the polarizing film according to the first embodiment only in that the processing temperature at the high temperature annealing step is different, and the other manufacturing conditions are the first. This is the same as the embodiment. The polarizing film according to the second embodiment was manufactured at a processing temperature of 120 ° C. during the high temperature annealing step.

  The manufacturing method of the polarizing film according to the third embodiment is different only in that the immersion time in the supercritical carbon dioxide crosslinking step is different from the manufacturing method of the polarizing film according to the first embodiment, and other manufacturing conditions are This is the same as in the first embodiment. The polarizing film according to the third embodiment was produced by setting the immersion time in the supercritical carbon dioxide crosslinking step to 24 hours.

  The manufacturing method of the polarizing film according to the fourth embodiment is different from the manufacturing method of the polarizing film according to the third embodiment only in that the processing temperature at the high temperature annealing step is different, and the other manufacturing conditions are the third. This is the same as the embodiment. The polarizing film according to the fourth embodiment was manufactured at a processing temperature of 110 ° C. during the high temperature annealing step.

  The polarizing film manufacturing method according to the fifth embodiment is different from the polarizing film manufacturing method according to the first embodiment only in that the ambient temperature in the supercritical carbon dioxide fluid system during the supercritical carbon dioxide crosslinking process is different. The other manufacturing conditions are different from those of the first embodiment. The polarizing film according to the fifth embodiment was manufactured at an ambient temperature of 70 ° C. in the supercritical carbon dioxide fluid system.

  The polarizing film manufacturing method according to the sixth embodiment is different from the polarizing film manufacturing method according to the fifth embodiment only in that the processing temperature during the high-temperature annealing process is different, and the other manufacturing conditions are the fifth. This is the same as the embodiment. The polarizing film according to the sixth embodiment was manufactured at a processing temperature of 120 ° C. during the high temperature annealing step.

  Compared with the polarizing film manufacturing method according to the first embodiment, the polarizing film of Comparative Example 1 is not subjected to the supercritical carbon dioxide crosslinking step and the high temperature annealing step, and the other manufacturing conditions are the same as in the first embodiment. Manufactured. This polarizing film is almost the same as a normal commercially available polarizing plate except that there is no protective film such as a TAC film.

  The manufacturing method of the polarizing film of Comparative Example 2 is a heat treatment step after the supercritical carbon dioxide crosslinking step (corresponding to the high temperature annealing step in the first embodiment), compared with the manufacturing method of the polarizing film according to the first embodiment. It differs only in that the processing temperature at that time is different, and the other manufacturing conditions are the same as in the first embodiment. The polarizing film according to Comparative Example 2 was manufactured by setting the heat treatment after the supercritical carbon dioxide crosslinking step to a low temperature of 80 ° C.

In Table 1, the manufacturing conditions in each embodiment and each comparative example mentioned above, the infrared absorption spectrum result of a polarizing film, an optical characteristic, and a dimensional expansion / contraction ratio are shown. In FIG. 1, the infrared absorption spectrum of the polarizing film in 1st Embodiment, 2nd Embodiment, and the comparative example 1 is shown. In FIG. 1, the horizontal axis represents the wave number (cm ⁻¹ ), the vertical axis represents the absorptance, and the vertical axis represents the spectrum result shifted in the vertical axis direction so that the spectrum characteristics of the respective polarizing films can be compared. . FIG. 6A shows the change in storage elastic modulus (E ′) with respect to the temperature rise of the polarizing film according to the first embodiment, the second embodiment, and comparative example 1, and the change in tan δ indicating the occurrence state of local molecular motion. Show. FIG. 6B shows the sample length change of the polarizing film according to the first embodiment, the second embodiment, and the comparative example 1. FIG. 7 is a cross-sectional view showing the dimensional expansion / contraction change rate at 130 ° C. and 150 ° C. based on the data of the dimensional expansion / contraction change rate with the temperature rise of the polarizing film according to each embodiment and comparative example. Is plotted against the parameter I (OH) / I (CH ₂ ) intensity ratio. In addition, Table 1 shows the dimensional expansion and contraction change rates at 130 ° C. and 150 ° C. in the respective embodiments and comparative examples.

The infrared absorption spectrum was measured using a Nicolet Magna-550 + DuraSampl II ATR, which is a type of infrared spectrophotometer manufactured by Thermo Electron, with the wave number range set to 400 to 4000 cm ⁻¹ . The measurement was performed with the stretching direction of the polarizing film and the traveling direction of the optical axis in parallel. For the obtained infrared spectrum analysis, OMNIC32 was applied to the software program.

From the obtained Fourier transform infrared absorption spectrum peak intensity derived from the stretching vibration of the OH group bonded to a carbon of the main chain of the polyvinyl alcohol resin in the vicinity of a wave number 3322cm ^-1 height I (OH), wavenumber 2914cm ^-1 The peak intensity height I (CH ₂ ) derived from the CH ₂ group stretching vibration of the main chain carbon chain in the vicinity was determined. Then, by obtaining the height ratio of the peak intensity of the infrared absorption spectrum of the OH groups stretching peak intensity height and CH ₂ groups stretching vibration of the vibration, a hydroxyl group remaining rate, i.e. guessed crosslinked state of the polarizing film.

In general, since the infrared absorption spectrum is easily affected by the sample shape and the like, qualitative analysis is the main, and it is said that it is not suitable for quantitative analysis. However, since the peak intensities I (OH) and I (CH ₂ ) are relatively close wavelengths and are affected by the sample shape to almost the same extent, there is a merit that the relative values can be quantitatively shown. Further, in the assumed system, the influence of the contained water on the stretching vibration peak intensity of the OH group is small, and the hydroxyl group of the polyvinyl alcohol resin contributes almost. Further, since the CH ₂ group stretching peak intensity itself is not significantly affected by crosslinking, there is an advantage that the crosslinked state is directly reflected in these peak intensity ratios.

  The optical properties were measured using a single transmittance with a corrected visibility, using an automatic polarizing film measuring device VAP-7070, which is a kind of UV-visible spectrophotometer manufactured by JASCO Corporation, with a wavelength range set to 380-780 nm. The degree of polarization was measured.

  About durability, durability was judged by performing the temperature rising test at the low temperature which assumed high temperature environment preservation | save with the viscoelasticity measuring test machine. Specifically, using DVA-220 manufactured by IT Laboratories, we observed changes in storage elastic modulus (E '), changes in tan δ indicating the occurrence of local molecular motion, and changes in sample length in constant strain mode. Went. In the temperature rise test at low humidity, the heating rate is 2 ° C./min. The temperature was increased from room temperature to 150 ° C. and observation was performed. At this time, each polarizing film was cut so that the sample shape had a grip length of 15 mm and a sample width of 5 mm. The thickness of each polarizing film was determined using a TESA module. In the case of a normal durability confirmation test, only changes in optical properties and shapes before and after storage for a predetermined period can be observed, and the storage time for a predetermined period is about 1000 hours. On the other hand, in the durability test adopted here, information on the microstructure such as local molecular motion in the film and changes in the sample length can be obtained continuously and quantitatively by using a viscoelasticity measuring tester. Furthermore, these measurements can be performed in a short time, and the efficiency is high.

As shown in Table 1, the polarizing film according to the first to sixth embodiments and Comparative Example 2 has almost the same optical characteristics required for the polarizing film as compared with Comparative Example 1 equivalent to a commercially available polarizing plate. On the other hand, the polarizing film according to the first to sixth embodiments and the comparative example 2 has a parameter I (OH) / I (CH ₂ ) intensity ratio indicating the crosslinking state obtained from the infrared absorption spectrum, as compared with the comparative example 1. It can also be seen that the number of uncrosslinked hydroxyl groups decreases and the number of crosslinking points increases. In addition, I (OH) / I (CH ₂ ) of the polyvinyl alcohol raw film before dye stretch-crosslinking is 1.660, and even in Comparative Example 1 where the critical carbon dioxide crosslinking treatment is not performed, It can be seen that cross-linking proceeds in the manufacturing process of the polarizing plate. From the above results, it can be seen that the optical properties necessary for the polarizing film are maintained even when the crosslinking is advanced by additional impregnation of the crosslinking material under a supercritical state and high-temperature annealing treatment.

  As shown in FIG. 6A, in the polarizing film according to the first and second embodiments, the storage elastic modulus (E ′) slightly decreases as the temperature rises as compared with Comparative Example 1, but the tan δ Almost no dispersion is seen. Furthermore, as shown in FIG. 6B, the dimensional expansion / contraction change is also greatly improved as compared with Comparative Example 1. For example, when compared with the dimensional expansion / contraction change rate at 150 ° C., the dimensional expansion / contraction change rate of Comparative Example 1 is 4.38%, whereas the dimensional expansion / contraction change rates of the first embodiment and the second embodiment are each half. The following 1.62% and 0.25% were confirmed to be very small.

When judging the quality related to the dimensional expansion / contraction change amount of the polarizing film, in general, when a polarizing plate comprising a TAC film so as to sandwich the polarizing film is attached to the outside of the liquid crystal cell, the contraction is about 3%. Is allowed. In contrast, when a polarizing film is provided on the inner side of the liquid crystal cell (in-cell), that is, on the liquid crystal side surface of the substrate constituting the liquid crystal cell without providing the TAC film, the transparent electrode is formed in the state where the polarizing film exists. Through the process. For this reason, it is necessary to consider the dimensional expansion / contraction change rate of the polarizing film during the transparent electrode film formation. The processing temperature varies depending on the manufacturing process of the liquid crystal cell. However, from the processing temperature at the time of forming the ITO (Indium Tin Oxide) transparent electrode and the alignment film, as a quality judgment regarding the dimensional expansion / contraction change amount of the polarizing film, the dimensional expansion / contraction change rate at 150 ° C. or 130 ° C. is ± 0. One guideline is to keep it within 5%. Therefore, in each embodiment and each comparative example, as shown in FIG. 7, the parameter I (OH) / I (CH indicating the crosslinking state obtained by the dimensional expansion / contraction change rate and the infrared absorption spectrum at 130 ° C. and 150 ° C. The relationship with ₂ ) was plotted. Table 2 shows the dimensional expansion / contraction change rate at 130 ° C. and 150 ° C. in each embodiment and each comparative example. As shown in FIG. 7, the value of I (OH) / I (CH ₂ ) is equivalent to that of a conventional polarizing plate in order to suppress the dimensional expansion / contraction change rate at high temperatures such as 130 ° C. and 150 ° C. It turns out that it is necessary to bring from the value of Comparative Example 1 to a value where the crosslinking has further progressed. As shown in FIG. 7 and Table 2, in all of the first to sixth embodiments, the dimensional expansion / contraction change rate at 130 ° C. or 150 ° C. is within ± 0.5%. In this case, I (OH) It can be seen that / I (CH ₂ ) is 1.05 or less. Moreover, even if supercritical carbon dioxide cross-linking treatment is performed, in Comparative Example 2 in which the subsequent heating process was performed at a temperature not so high as 80 ° C., Comparative Example 1 equivalent to a commercially available polarizing film and I (OH) / I ( CH ₂₎ intensity ratio does not change much, as compared with the first to sixth embodiments, it is understood that the crosslinking of the film does not so proceed.

As described above, by proceeding with the crosslinking of the polyvinyl alcohol-based resin and setting the I (OH) / I (CH ₂ ) strength ratio to 1.05 or less, a polarizing film having a small dimensional expansion / contraction change at high temperatures is obtained. Can do. Therefore, even if such a polarizing film is provided inside the liquid crystal cell, the dimensional expansion / contraction change rate can be kept small even during high-temperature treatment during the liquid crystal cell manufacturing process, and deterioration of the properties of the polarizing film can be suppressed. . Thus, a polarizing film having significantly improved dimensional stability while maintaining high optical characteristics can be obtained. And as one of the methods for producing such a polarizing film having an I (OH) / I (CH ₂ ) intensity ratio of 1.05 or less, as described above, a polyvinyl alcohol resin is cross-linked under supercritical conditions. There is a method of performing a high temperature annealing treatment after the treatment.

Here, the supercritical state is a liquid that exceeds a specific pressure / temperature range by pressurizing and heating a substance, in addition to impregnation / diffusivity / penetration / viscosity such as gas, This means a specific state with fluidity. In the present embodiment, carbon dioxide is used as a medium for creating a supercritical atmosphere, but in the case of carbon dioxide, such a state is obtained at 31 ° C. and 7.3 PAa or more. In the present embodiment, carbon dioxide is used as the main medium for creating a supercritical atmosphere, but the present invention is not limited to this. Any medium can be used as long as it can extract the water contained in the polarizing film in consideration of the glass transition temperature of the polarizing film, and can take in the cross-linking material solution and impregnate it into the film. For example, in addition to carbon dioxide (CO ₂ ), ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ), nitric oxide (NO), xenon (Xe), chlorotrifluoromethane (CF ₃ Cl), monofluoro methane _(CH 3 F), methane _(CH 4), propane _{(C 3 H} 8), propylene (C3 H6), or the like can be used krypton (Kr). In the present embodiment, carbon dioxide (CO ₂ ), ethane (C ₂ H ₆ ), ethylene (C ₂ H ₄ ), nitric oxide (NO), xenon (Xe), chlorotrifluoromethane (CF ₃ Cl), Monofluoromethane (CH ₃ F) or the like is preferable, and carbon dioxide is more preferable from the viewpoint of ease of handling. The respective critical temperatures and critical pressures are shown in Table 2 below.

  As described above, in the supercritical carbon dioxide crosslinking step, boric acid ethanol was added as an additive solution in order to impregnate the additional crosslinking material in addition to removing water contained in the polarizing film. The solvent to be added to boric acid is not particularly limited as long as it removes water contained in the polarizing film and dissolves the cross-linking material and does not damage the polarizing film, and a known solvent can be used. In addition to using ethanol as the solvent as in this embodiment, for example, an alcohol solvent system such as normal propyl alcohol is preferable in consideration of the solubility of boric acid and damage to the polarizing film. Further, boric acid may be used as a cross-linking material instead of boric acid ethanol.

[Liquid Crystal Device]
Next, the case where the polarizing film of this invention is used for a liquid crystal device is demonstrated using FIG. FIG. 5 is a schematic cross-sectional view of a TN (twisted nematic) liquid crystal device.

  As shown in FIG. 5, the liquid crystal device 1 includes a liquid crystal cell 30 and a backlight 31 that irradiates the liquid crystal cell 30 with light.

  The liquid crystal cell 30 includes a pair of first transparent substrate 13 and second transparent substrate 213 that are spaced apart from each other, a spacer 17 that maintains a desired gap between these substrates, a pair of first transparent substrate 13, And a liquid crystal 14 sandwiched between second transparent substrates 213. On the surface of the first transparent substrate 13 on the liquid crystal 14 side, the polarizing film 11 of the above-described embodiment, the color filter layer 12 made of R (red), G (green), and B (blue), and the ITO made of a solid film are common. An electrode 12 and an alignment film 15 made of polyimide are sequentially laminated. On the surface of the second transparent substrate 213 on the liquid crystal 14 side, a polarizing film 11, a signal line (not shown) and a scanning line (not shown) intersecting each other, and an intersection of the signal line and the scanning line are provided. A switching element (not shown), an ITO pixel electrode 212, and an alignment film 15 made of polyimide are formed.

The backlight 31 includes a light source 20 and a light guide plate 21. The polarizing film 11 is a polyimide-based resin film that is manufactured by the manufacturing method described in the above-described embodiment and is cross-linked with boron having an I (OH) / I (CH ₂ ) intensity ratio of 1.05 or less.

  The liquid crystal device 1 is an in-cell type in which the polarizing film 11 is provided in the liquid crystal cell 30. In such an in-cell type liquid crystal device 1, the ITO common electrode 12, the ITO pixel electrode 212, the alignment film 15 and the like are formed in the state where the polarizing film 11 is present. Since these electrodes and the like are formed at a high temperature, it is desirable that the polarizing film 11 has a small dimensional deformation even at such a processing temperature. In the present embodiment, as described above, the polarizing film 11 is formed by supercritical carbon dioxide crosslinking treatment and high-temperature annealing treatment. Therefore, the liquid crystal has small change in dimensional expansion and contraction even at high temperatures and stable display characteristics. Device 1 can be obtained. Further, in such a liquid crystal device 1, a protective film such as a TAC film is not required unlike a conventional polarizing plate, so that the liquid crystal device 1 can be thinned.

  Moreover, a liquid crystal cell and a polarizing film may be manufactured separately, and a pair of polarizing films may be provided so as to sandwich the liquid crystal cell, thereby constituting a liquid crystal device. In this case, a polarizing film is provided on the outer side of the liquid crystal cell, that is, on the surface side facing the liquid crystal side surface of the substrate constituting the liquid crystal cell. Thereby, compared with the conventional polarizing plate, the liquid crystal device can be reduced in thickness because the TAC film is not provided.

  Further, the polarizing film according to the present invention, if necessary, a hard coat layer, an antireflection layer, an ultraviolet absorption layer, an antiglare layer, an antireflection layer, a half reflection layer, a reflection layer, a phosphorescent layer, a diffusion layer, an electroluminescence layer, A polarizing plate may be produced by providing functional layers such as a viewing angle widening layer and a brightness enhancement layer. The functional layer can be provided on the polarizing film by pasting together using a known adhesive and solidifying the adhesive with an electron beam or the like.

  Moreover, since the polarizing film itself has extremely high durability as described above, it is not necessary to laminate a protective film such as a TAC film as in a conventional polarizing plate, as described above. However, in order to further improve heat resistance and moisture resistance, a polarizing plate may be produced by laminating an optically isotropic protective film on one side or both sides of a polarizing film in addition to the functional layer described above. it can. A known protective film can be used as the protective film. For example, triacetyl cellulose, diacetyl cellulose, polycarbonate, polymethyl methacrylate, polystyrene, polyether sulfone, polyarylene ester, poly-4-methylpentene, polyphenylene oxide, cyclo-based or norbornene-based polyolefin can be used.

  In the above-described embodiment, the supercritical carbon dioxide crosslinking step S6 is performed after the drying step S5. However, as shown in FIG. 8, the drying step S6 is performed after the supercritical carbon dioxide crosslinking step S5. Also good. Moreover, as shown in FIG. 9, you may perform supercritical carbon dioxide bridge | crosslinking process S5, S7 once before and after drying process S6, respectively. In FIGS. 8 and 9, the same process names are assigned to the same processes as those in the above-described embodiment.

  Moreover, in the above-mentioned embodiment, although the polarizing film was mentioned as an example as an optical member, it is applicable also to a phase difference film etc.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device 11 ... Polarizing film 13 ... 1st transparent substrate 14 ... Liquid crystal 213 ... 2nd transparent substrate

Claims (7)

It consists of a polyvinyl alcohol-based resin cross-linked and fixed using boron,
Infrared absorption spectrum at a wave number 3322cm peak intensity height from stretching vibration of OH groups bonded to the carbon of the main chain in the vicinity of ^-1 first peak strength and high Satoshi, carbon of the main chain in the vicinity of a wave number 2914Cm ^-1 When the peak intensity height derived from the stretching vibration of the CH ₂ group of the chain is the second peak intensity height, the ratio of the first peak intensity height to the second peak intensity height is 1.05. An optical member in the following range. The optical member according to claim 1,
An optical member in which the polyvinyl alcohol resin is impregnated with a dichroic dye. A polyvinyl alcohol-based resin is treated with a cross-linking material containing boric acid under a medium in a supercritical atmosphere,
The manufacturing method of the optical member which heat-processes the said polyvinyl alcohol-type resin at the temperature of 100 to 130 degreeC after the said process. It is a manufacturing method of the optical member according to claim 3,
The method for manufacturing an optical member, wherein the medium is carbon dioxide. The method for producing an optical member according to claim 4, further comprising:
The method for producing an optical member, wherein the polyvinyl alcohol-based resin is dried before or after the heat treatment and before or after the treatment with the cross-linking material containing boric acid under the medium in the supercritical atmosphere. A first substrate and a second substrate spaced apart from each other;
A liquid crystal sandwiched between the first substrate and the second substrate;
An optical member disposed on one surface of each of the first substrate and the second substrate,
The optical member is
It consists of a polyvinyl alcohol-based resin cross-linked and fixed using boron,
Infrared absorption spectrum at a wave number 3322cm peak intensity height from stretching vibration of OH groups bonded to the carbon of the main chain in the vicinity of ^-1 first peak strength and high Satoshi, carbon of the main chain in the vicinity of a wave number 2914Cm ^-1 When the peak intensity height derived from the stretching vibration of the CH ₂ group of the chain is the second peak intensity height, the ratio of the first peak intensity height to the second peak intensity height is 1.05. The range of liquid crystal devices. The liquid crystal device according to claim 6,
The optical member is provided on a surface on the liquid crystal side of each of the first substrate and the second substrate.

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