JP2001051115A - Manufacture of phase difference plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a relatively low-cost phase difference plate excellent in an optical characteristic, a mechanical property, a thermal property and chemical resistance, and excellent in environmental adaptability because of no generation of harmful gas with a low combustion calorie when burning. SOLUTION: This manufacturing method is as follows. A polyethylene terephthalate-based polymer selected as a polymer is heated and melted at a temperature not less than the melting point, and is cooled and solidified at a temperature below the melting point with a magnetic field applied thereto until a birefringence not less than 10-4 or a light transmittance not less than 20% occurs. The temperature for the cooling and solidification is 230-255 deg.C, while a cooling time is 3-40 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a retardation plate, and more particularly, to a method for producing a retardation plate in which a magnetic field is applied to a polyethylene terephthalate-based polymer to orient the molecules.

[0002]

2. Description of the Related Art Conventionally, various retardation plates have been used for optically compensating a birefringence effect of a liquid crystal display device. Above all, a retardation plate made of a plastic material has the advantage of being able to continuously produce a large-area retardation plate having various optical anisotropies in a large amount as compared with an inorganic crystal material, and is widely used in practice. The main plastic materials used as the retardation plate include polycarbonate, polymethylmethacrylate, polyvinyl alcohol, and cellulose polymers. The method of manufacturing these plastic retarders is to mechanically stretch a film-shaped molded product obtained by melt extrusion molding or solvent casting using equipment such as a roll or tenter to orient the molecules in one direction. The method is generally used.

Further, in order to stabilize or improve optical characteristics such as thickness accuracy, retardation, wavelength dispersion, three-dimensionality, and temperature characteristics of a retardation plate, a material is specified by stretching processing conditions or a polymer alloy. Alternatively, addition of a solvent is being studied. On the other hand, JP-A-63-775037,
JP-A-1-71710, JP-A-3-122128
According to the publication, a method is disclosed in which a magnetic field is applied to a liquid crystalline polymer to align the polymer. Also, Japanese Patent Application Laid-Open
Japanese Patent Application No. 62121 discloses a method of orienting a polyacetylene derivative film by applying a magnetic field while immersing the film in a solvent such as ethyl acetate.

[0004]

However, the inventions of JP-A-63-775037, JP-A-1-71710 and JP-A-3-122128 disclose polyparabenzobisthiazole and polyparaphenylene terephthalamide. It was limited to a special liquid crystalline polymer having a liquid crystal forming ability. The purpose and effect of applying a magnetic field were mainly to improve mechanical strength such as flexural modulus by high orientation.

[0005] The method disclosed in Japanese Patent Application Laid-Open No. 7-62121 is that the raw material polyacetylene derivative film is difficult to obtain, that the film is immersed in a solvent before the orientation treatment, and that the solvent must be removed after the magnetic field orientation treatment. There was such a problem. Further, the polyacetylene derivative film oriented in a magnetic field by this method has no description about optical properties and mechanical properties such as retardation and transparency, and is not practical for an optical element such as a retardation plate.

The inventors of the present invention have excellent optical adaptability, mechanical properties, thermal properties, and chemical resistance, generate no harmful gases during combustion, reduce combustion calories, and have good environmental adaptability such as recyclability. Focusing on polyethylene terephthalate polymer, which is known as a relatively inexpensive polymer, and studied the method of manufacturing a retardation plate that applies a magnetic field to this polyethylene terephthalate polymer and orients it in any direction. As a result, the present invention has been achieved.

[0007]

That is, the present invention is a method for producing a retardation plate, which comprises applying a magnetic field to a polyethylene terephthalate-based polymer to orient the molecule in an arbitrary direction. Further, the polyethylene terephthalate polymer is heated and melted at a temperature equal to or higher than the melting point, and then cooled until a birefringence of 10 ⁻⁴ or more or a light transmittance of 20% or more occurs at a temperature equal to or lower than the melting point with a magnetic field applied. This is a method for manufacturing a retardation plate to be solidified. Furthermore, the temperature for cooling and solidifying is 230 to 255 ° C, and the cooling time is 3 to
A method for manufacturing a retardation plate, wherein the process time is 40 minutes.

[0008] The polyethylene terephthalate polymer used in the present invention is a general polyethylene terephthalate homopolymer in which the glycol component is ethylene glycol and the dicarboxylic acid component is terephthalic acid. A polyethylene terephthalate copolymer containing a glycol component or a dicarboxylic acid component is preferred.

Other glycol components of ethylene glycol include propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, neopentyl glycol, cyclohexanedimethanol, heptamethylene glycol, xylylene. Examples thereof include glycol, diethylene glycol, polyethylene glycol, bisphenol A, catechol, resorcinol, hydroquinone, dihydroxydiphenyl, dihydroxydiphenylether, dihydroxydiphenylmethane, dihydroxydiphenylketone, dihydroxydiphenylsulfide, dihydroxydiphenylsulfone, and the like. Other dicarboxylic acid components of terephthalic acid include isophthalic acid, naphthalenedicarboxylic acid,
Diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl methane dicarboxylic acid, diphenyl ketone dicarboxylic acid, diphenyl sulfide dicarboxylic acid, diphenyl sulfone dicarboxylic acid, aliphatic dicarboxylic acid such as succinic acid,
Adipic acid, sebacic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, tetralindicarboxylic acid, decalindicarboxylic acid and the like are exemplified.

[0010] These copolymer components are present in an amount of up to 40 mol%, preferably up to 20 mol%, more preferably 10 mol%, of the total glycol component and the total dicarboxylic acid component, respectively.
It may be copolymerized up to mol%. Usually, the polyethylene terephthalate-based polymer obtained by copolymerizing these copolymer components has a melting point lower than the melting point of the polyethylene terephthalate homopolymer, so that it is easy to process and the crystallization rate can be changed.

In addition, as long as the polyethylene terephthalate-based polymer maintains a substantially linear structure, a small amount of a polyfunctional copolymer component such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid, and pyromellitic acid is used. It may be copolymerized. In some cases, a polyethylene terephthalate copolymer synthesized by copolymerizing these polyfunctional copolymer components can improve the melt elasticity at the time of molding and improve the moldability.

Further, benzoic acid, t-butylbenzoic acid,
A small amount of a monofunctional copolymer component such as benzoylbenzoic acid, stearic acid, benzyl alcohol and stearyl alcohol may be copolymerized. By copolymerizing the monofunctional copolymer component, the thermal stability at the time of molding is improved, and the acetaldehyde content in the retardation plate can be further reduced. When these multifunctional copolymer components and monofunctional copolymer components are used in combination,
Usually 0.001 to 0.001 relative to all components constituting the copolymer.
It is desirably 2.0 mol%, preferably in the range of 0.01 to 1 mol%.

Although the intrinsic viscosity and average molecular weight of the polyethylene terephthalate polymer are not specified, the intrinsic viscosity is generally in the range of 0.6 to 1.4. Furthermore, for the purpose of improving heat resistance and moldability, polyarylate, polycarbonate, polybutylene terephthalate, polyethylene naphthalate, polyester-based elastomer, polystyrene-based polymer, acrylic-based polymer, known polyamide-based polymer and the like A small amount of a polymer can be added.

The polyethylene terephthalate polymer used in the retardation plate of the present invention may contain a pigment, a dye, a fluorescent brightener, a dispersant, a stabilizer, an ultraviolet absorber, an energy quencher, It is also possible to appropriately add an inhibitor, an antioxidant, a heat stabilizer, a lubricant, a solvent and the like.

As a means for generating a magnetic field to be applied, an electromagnet, a permanent magnet, a coil or the like can be used. Since the molecules are more likely to be oriented as the strength of the magnetic field is higher, 1 Tesla or more is preferable. If it is less than 1 Tesla, the molecular orientation is insufficient. A practical magnetic field strength of 2 Tesla or more, and a more preferable magnetic field strength of 3 Tesla to 20 Tesla is practical.

[0016] by applying a magnetic field as the conditions for molecular orientation in any direction, polyethylene terephthalate-based polymer by applying a magnetic field to After the amorphous state by heating and melting at a temperature above the melting point ^10-4 or more It is important to cool and solidify until birefringence occurs. The phenomenon utilizes the property that the polyethylene terephthalate-based polymer is easily oriented in a magnetic field in the initial stage of melt crystallization, that is, in the induction period of crystallization. If the birefringence is less than 10 ^-4 , the retardation is so small that it cannot function as a retardation plate.

The retardation of a retardation plate molecularly oriented in a direction parallel to the plate surface is represented by the product of the thickness of the retardation plate and the birefringence.
For example, to obtain a retardation plate having a retardation of a quarter wavelength of 570 nm, the product of birefringence and the thickness of the retardation plate is 142.
In order to obtain a retardation plate having a phase difference of 5 nm and a half wavelength, it is necessary to experimentally set the conditions for applying a magnetic field and molecular orientation so that the phase difference becomes 285 nm and the thickness of the retardation plate. It is possible. Although the thickness of the retardation plate of the present invention is not limited, it is 0.05 mm to 2.0 mm.
0 mm is preferable, and furthermore, the range of 0.1 mm to 1.0 mm is preferable.

The retardation plate manufacturing method of the present invention is characterized in that, unlike a retardation plate produced by a conventional mechanical stretching method, the molecules can be oriented in an arbitrary direction according to the direction of the magnetic field. If a magnetic field is applied perpendicularly to the thickness direction of the retardation plate, that is, in a direction parallel to the plate surface, it is possible to orient in the same direction as the retardation plate by a conventional mechanical stretching method. On the other hand, if a magnetic field is applied obliquely to the in-plane direction of the plate, a retardation plate having a phase difference in the oblique direction can be manufactured. Further, the thickness of the retardation plate obtained in the present invention is characterized in that the thickness before treatment is not extremely reduced by the stretching ratio as in the case of the conventional mechanical stretching method, and the thickness before the treatment can be maintained.

The light transmittance of the retardation plate expressed in the present invention means the light transmittance of visible light having a wavelength of about 400 to 800 nm, and the light transmittance is not particularly limited. The transmittance is preferably 20% or more, more preferably 40% or more. The higher the light transmittance, the more preferable the liquid crystal display element and the like appear to be bright.
% Is not suitable because it becomes darker.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION
It is characterized in that a magnetic field is applied to the polyethylene terephthalate-based polymer to cause molecular orientation in an arbitrary direction. More specifically, a polyethylene terephthalate-based polymer is heated and melted at a temperature equal to or higher than the melting point, and then cooled and solidified at a temperature equal to or lower than the melting point under application of a magnetic field until birefringence of 10 ⁻⁴ or more occurs. This is a method for producing a retardation plate in which molecules are oriented in the direction of.

The melting point of the polyethylene terephthalate polymer is generally in the range of 235 to 265 ° C. Although the polyethylene terephthalate-based polymer used in the production method of the present invention may be in the form of pellets or powder, the pellets or powdered polyethylene terephthalate-based polymer may be preformed by press molding, extrusion molding, inflation molding, etc., into a film or sheet. It is easier to handle if it is formed into a plate-like molded body. The plate-shaped molded body molded polyethylene terephthalate polymers were heated to melt at a temperature higher than the melting point is completely melted again in to the amorphous state, then, while applying a magnetic field at a temperature lower than the melting point 10 ^- Cooling solidification, that is, cooling crystallization, until birefringence of ⁴ or more occurs. Note that the crystallinity at this time is not specified. The temperature below the melting point is not specified as long as the temperature is lower than the melting point and can be cooled and solidified.

The temperature and time for cooling and solidification depend on the type, thermal properties, crystallinity, strength of the applied magnetic field, and required phase difference of the polyethylene terephthalate-based polymer. Usually, the temperature for cooling and solidifying until a birefringence of 10 ⁻⁴ or more occurs in a magnetic field atmosphere of 2 Tesla or more is 230 to 230 ° C.
The range of 255 ° C. and the time are preferably 3 to 40 minutes. If the time is shorter than 3 minutes, the birefringence becomes less than 10 ⁻⁴ , and if the time is longer than 40 minutes, crystallization proceeds and the light transmittance becomes 2 or less.
It is not preferable because it may be less than 0%.

Now, the present invention will be described in further detail with reference to Examples. The retardation and birefringence evaluated in the examples and comparative examples were measured at a wavelength of 589 n using a polarimeter manufactured by Shinko Seiki.
The value of m. The light transmittance is a light transmittance of each wavelength measured by an ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation.

[0024]

Example 1 Dehumidified and dried polyethylene terephthalate homopolymer (intrinsic viscosity = 1.05, melting point = 253 ° C.)
Was supplied to a T-die extruder to produce a transparent unstretched film having a thickness of 0.2 mm. The unstretched film was melted by heating to a temperature of 270 ° C. or higher at a melting point or higher in a magnetic field of 6 Tesla, and then cooled and solidified at 245 ° C. for 20 minutes in the same magnetic field. The direction of the magnetic field was parallel to the film surface. The retardation of the obtained retardation plate having a thickness of 0.2 mm is 24.
6 nm, the birefringence was 1.23 × 10 ⁻⁴ , and the light transmittance at a wavelength of 600 nm was 41.1%.

[0025]

Example 2 The same polyethylene terephthalate homopolymer as in Example 1 (intrinsic viscosity = 1.05, melting point = 253)
C) is heated to a temperature of 270 ° C. or higher at a melting point or higher in a magnetic field of 6 Tesla and melted.
The mixture was cooled and solidified at 45 ° C. for 25 minutes. The direction of the magnetic field was parallel to the film surface. The obtained retardation plate having a thickness of 0.2 mm has a retardation of 147 nm and a birefringence of 7.35 × 10
^-4 , the light transmittance at a wavelength of 600 nm was 28.2%.

[0026]

Example 3 Dehumidified and dried polyethylene terephthalate copolymer (PET 9921 manufactured by Eastman Chemical Co., Ltd.)
A polyethylene terephthalate-based polymer containing cyclohexanedimethanol as a copolymer component. Intrinsic viscosity = 0.7
6, melting point = 243 ° C.) was supplied to a T-die extruder to produce a transparent unstretched film having a thickness of 0.2 mm. The unstretched film was heated and melted at a temperature of 260 ° C. or higher in a magnetic field of 6 Tesla at a temperature equal to or higher than the melting point, and then cooled and solidified at 235 ° C. for 3 minutes in the same magnetic field. The direction of the magnetic field was parallel to the film surface. The obtained retardation plate having a thickness of 0.2 mm has a retardation of 71.2 nm and a birefringence of 3.56 × 10 6.
^-4 , the light transmittance at a wavelength of 600 nm was 70.7%.

[0027]

Example 4 The same polyethylene terephthalate copolymer as in Example 3 (PET 99 manufactured by Eastman Chemical Co., Ltd.)
21 A polyethylene terephthalate-based polymer containing cyclohexanedimethanol as a copolymer component. Intrinsic viscosity =
The unstretched film (0.76, melting point = 243 ° C.) was heated and melted at a temperature of 260 ° C. or higher in a magnetic field of 6 Tesla at a temperature higher than the melting point, and then cooled and solidified at 235 ° C. for 5 minutes in the same magnetic field. The direction of the magnetic field was parallel to the film surface. The obtained retardation plate having a thickness of 0.2 mm had a retardation of 230 nm, a birefringence of 1.15 × 10 ⁻³ , and a light transmittance at a wavelength of 600 nm of 65.7%.

[0028]

Example 5 The same polyethylene terephthalate copolymer as in Example 3 (PET99 manufactured by Eastman Chemical Co., Ltd.)
21 A polyethylene terephthalate-based polymer containing cyclohexanedimethanol as a copolymer component. Intrinsic viscosity =
The unstretched film (0.76, melting point = 243 ° C.) was heated and melted at a temperature of 260 ° C. or higher in a magnetic field of 6 Tesla at a temperature higher than the melting point, and then cooled and solidified at 235 ° C. for 8 minutes in the same magnetic field. The direction of the magnetic field was parallel to the film surface. The obtained retardation plate having a thickness of 0.2 mm had a retardation of 308 nm, a birefringence of 1.54 × 10 ⁻³ , and a light transmittance at a wavelength of 600 nm of 44.8%.

[0029]

Comparative Example 1 Dehumidified and dried polyethylene terephthalate homopolymer (intrinsic viscosity = 1.05, melting point = 253 ° C.)
Was supplied to a T-die extruder to produce a transparent unstretched film having a thickness of 0.2 mm. The retardation and birefringence of this unstretched film were too small to be measured.

[0030]

Comparative Example 2 The same polyethylene terephthalate homopolymer as in Example 1 and Comparative Example 1 (intrinsic viscosity = 1.0)
5, a transparent unstretched film having a thickness of 0.2 mm having a melting point of 253 ° C.) is heated to a temperature of 270 ° C. or higher in a magnetic field of 6 Tesla.
, And then cooled and solidified at 245 ° C. for 1 minute in the same magnetic field. The direction of the magnetic field was parallel to the film surface. The birefringence of the obtained 0.24 mm thick film was smaller than 10 ^-5 .

[0031]

Comparative Example 3 The same polyethylene terephthalate homopolymer as in Example 1 and Comparative Example 1 (intrinsic viscosity = 1.0)
5, a transparent unstretched film having a thickness of 0.2 mm having a melting point of 253 ° C.) is heated to a temperature of 270 ° C. or higher in a magnetic field of 6 Tesla.
And heated to 245 ° C in the same magnetic field at 60 ° C.
Cooled and solidified for minutes. The direction of the magnetic field was parallel to the film surface. The obtained 0.24 mm thick film was opaque and the birefringence could not be measured.

[0032]

Comparative Example 4 Dehumidified and dried polyethylene terephthalate copolymer (PET 9921 manufactured by Eastman Chemical Co., Ltd.)
A polyethylene terephthalate-based polymer containing cyclohexanedimethanol as a copolymer component. Intrinsic viscosity = 0.7
6, melting point = 243 ° C.) was supplied to a T-die extruder to produce a transparent unstretched film having a thickness of 0.2 mm. The retardation and birefringence of this unstretched film were too small to be measured.

[0033]

Comparative Example 5 The same polyethylene terephthalate copolymer as in Example 3 and Comparative Example 4 (PET 9921 manufactured by Eastman Chemical, a polyethylene terephthalate-based polymer containing cyclohexanedimethanol as a copolymer component. Intrinsic viscosity = 0.76, melting point = 243 ° C.) ) Thickness 0.2
The transparent unstretched film having a thickness of 2 mm was heated to a temperature of 260 ° C. or higher than the melting point in a magnetic field of 6 Tesla to be melted, and then cooled and solidified at 235 ° C. for 45 minutes in the same magnetic field. The direction of the magnetic field was parallel to the film surface. Obtained thickness 0.2m
The film of m was opaque and the birefringence could not be measured.

[0034]

Example 6 Dehumidified and dried polyethylene terephthalate homopolymer (intrinsic viscosity = 1.05, melting point = 253 ° C.)
Was supplied to a T-die extruder to produce a transparent unstretched film having a thickness of 0.2 mm. The unstretched film was melted by heating to a temperature of 270 ° C. or higher at a melting point or higher in a magnetic field of 6 Tesla, and then cooled and solidified at 245 ° C. for 20 minutes in the same magnetic field. The direction of the magnetic field was 45 degrees with respect to the film surface. The retardation in the direction of 45 degrees with respect to the film surface of the obtained retardation plate having a thickness of 0.2 mm is 34.4 n.
m, the birefringence was 1.72 × 10 ⁻⁴ , and the light transmittance at a wavelength of 600 nm was 40.8%.

Table 1 shows the heating and cooling conditions, birefringence and wavelength of 500 nm and 60 nm for the above Examples and Comparative Examples.
The light transmittances at 0 nm, 700 nm, and 800 nm are collectively described.

[Table 1]

[0036]

The comparative examples 1 and 4 are ordinary non-stretched films of a non-stretched polyethylene terephthalate polymer and have a very small retardation. In Comparative Example 2, although a magnetic field was applied, sufficient birefringence did not occur because the time for cooling and solidifying in a magnetic field atmosphere was short. Comparative Example 3 and Comparative Example 5
Although a magnetic field is applied, the time required for cooling and solidifying in a magnetic field atmosphere is long, so that crystallization proceeds too much, the light transmittance is small, the transparency is poor, and there is no practicality.

In Examples 1 to 5 of the present invention, the polyethylene terephthalate-based polymer was heated and melted at a temperature higher than the melting point, and then cooled until a birefringence occurred at a temperature lower than the melting point under a magnetic field. This is a method for manufacturing a retardation plate to be solidified, and has a practical birefringence of 10 ⁻⁴ or more and a light transmittance of 20% or more. The direction of the magnetic field in Examples 1 to 5 is parallel to the film surface, and the direction of the magnetic field in Example 6 is a direction of 45 degrees with respect to the film surface. It is a phase difference plate.

That is, according to the method for producing a retardation plate of the present invention, a polyethylene terephthalate-based polymer which is excellent in optical properties, mechanical properties, and thermal properties, has good environmental adaptability, and is relatively inexpensive. Using a polymer, it is possible to manufacture retardation plates with molecular orientation in any direction, including optical compensation applications for liquid crystal display devices, optical switches, optical filters, and optical devices composed of these components. A wide range of applications can be developed as an optical element. Further, the retardation plate obtained by the production method of the present invention can be applied to a more sophisticated optical element by combining or integrating it with a polarizing film or another optical element.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayuki Tobita 5-10-5 Tabata, Kita-ku, Tokyo Polymertec R & D Center F-term (reference) 2H049 BA06 BA24 BA42 BA42 BC02

Claims (4)

[Claims] 1. A method for producing a retardation plate, wherein a magnetic field is applied to a polyethylene terephthalate-based polymer to cause molecular orientation in an arbitrary direction. 2. A retardation plate for heating and melting a polyethylene terephthalate-based polymer at a temperature not lower than its melting point, and then cooling and solidifying it under a magnetic field at a temperature lower than the melting point until birefringence of 10 ^-4 or more occurs. Manufacturing method 3. A retardation plate for heating and melting a polyethylene terephthalate-based polymer at a temperature not lower than its melting point, and then cooling and solidifying it under a magnetic field at a temperature lower than the melting point until a light transmittance of 20% or more is generated. Manufacturing method 4. A cooling and solidifying temperature of 230 to 255 ° C.
The method according to claim 2 or 3, wherein the cooling time is 3 to 40 minutes.