JPH0713683B2 - Retardation plate, composite polarizing plate using the same, and liquid crystal display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel retardation plate, a composite polarizing plate using the same, and a liquid crystal display device.

[Conventional technology]

The retardation plate is a film or sheet having birefringence. Since the light transmitted through the retardation plate has different refractive indexes in two directions orthogonal to each other, a phase difference occurs between the light rays orthogonal to each other after transmission.

A so-called 1 / 4λ plate having a function of producing a phase difference of 1 / 4λ with respect to the wavelength λ of an incident light ray is commercially available as a retardation plate and is put to practical use. This conventional 1 / 4λ
The plate is formed by uniaxially stretching a cellulose acetate film.

The 1/4 λ plate becomes a circularly polarizing plate when it is attached at an angle of 45 ° with respect to the optical axis of the linear polarizing plate, and it has an antiglare function that cuts reflected light, so it is used for various antiglare materials including VDT filters. Has been done.

In addition to the above cellulose-based resins, vinyl chloride-based resins (Japanese Patent Publication No.
JP-A-56-125702), polycarbonate resin (JP-B-41-12190, JP-A-56-130703), acrylonitrile-based resin (JP-A-56-130702), styrene Resins (Japanese Patent Laid-Open No. 56-125703), polyolefin-based resins (Japanese Patent Laid-Open No. 60-24502), and the like have been proposed, but in both cases, the so-called 1 / It is a 4λ plate. The retardation value (hereinafter sometimes abbreviated as R value) is represented by the product of the thickness (d) of the film or sheet and the birefringence index (Δn) of the film, that is, R = Δn × d.

On the other hand, as described in JP-A-61-186937 and JP-A-60-26322, the twist angle of the liquid crystal molecules is 90 degrees, and a pair of polarizing plates are provided on both sides of the liquid crystal cell. In a liquid crystal display device (generally referred to as a TN type liquid crystal display device) in which liquid crystals are arranged so that they are orthogonal or parallel to each other, it is attempted to improve the display quality by applying a retardation plate between one polarizing plate and a liquid crystal cell. There is also an attempt to do. Furthermore, in recent years, in response to a demand for an increase in display capacity and an increase in display screen, a liquid crystal display device in which a twist angle of liquid crystal molecules is set to about 180 to 270 degrees (generally, ST
It is called N-type liquid crystal display device) was developed. This S
In the TN type liquid crystal display device, coloring due to birefringence of liquid crystal molecules occurs and black and white display is impossible. As an example, the background color is yellow green and the display color is dark blue.

When the display device has such a hue, it is often restricted when performing color display such as multicolor and full color. In order to solve this problem, for example, as described in Nikkei Microdevice, October 1987, p. 84, another STN type liquid crystal cell is added with an achromatic liquid crystal cell as an optical compensator, and coloring is performed. A method for solving the problem and enabling a black and white display is shown.

[Problems to be Solved by the Invention]

The method of adding another achromatic liquid crystal cell as an optical compensator to the STN liquid crystal cell described above can eliminate coloring and enable black and white display, but (1) is expensive and inferior in economic efficiency,
There are problems of (2) being heavy and (3) being thick, and in addition to the above-mentioned improvement in display performance, it is required to solve these problems together.

It is also possible in principle to use a retardation plate instead of this achromatic liquid crystal cell, but with the conventional 1 / 4λ plate, (1) the retardation value does not match optically.

(2) The optical axis is not constant.

(3) A uniform black-and-white display cannot be achieved due to large optical color unevenness.

Therefore, it cannot be applied to new applications such as the liquid crystal display device described above.

[Means for Solving the Problems]

The present invention has been completed as a result of repeated studies in view of the above points, and is as follows.

(1) A polymer film or sheet formed by uniaxially stretching a thermoplastic polymer film or sheet so that the neck-in rate is 10% or less, and having a birefringence (Δ
The measured value of the retardation (Δn × d) defined by the product of n) and thickness (d) is in the range of 200 to 1000 nm, and the optical axis of the film or sheet is set to 45 degrees under the crossed Nicols. The color difference (Δ
A retardation plate having an E ^* ) of 20 or less.

(2) The retardation plate according to claim 1, wherein the α value defined by the formula (1) is 1.00 or more.

Here, R _F : Retardation value measured with hydrogen F line (486.1 nm) R _D : Retardation value measured with sodium D line (589.3 nm) (3) The retarder according to claim 1 is used. A composite polarizing plate laminated on a polarizing plate.

(4) A liquid crystal display device in which the retardation plate according to claim 1 is laminated on one surface of a liquid crystal cell, and a pair of polarizing plates are laminated so as to sandwich it.

The retardation plate of the present invention relates to a novel retardation plate having an appropriate retardation value and having little optical color unevenness.
The retardation value used is in the range of 30 to 1200 nm, but preferably adjusted to the range of 200 to 1000 nm.
A more appropriate retardation value is selected according to the specific application. For example, the retardation value is 20
Those in the range of 0 to 350 nm and those in the range of 475 to 625 nm can be exemplified for liquid crystal display devices.

Further, in the present invention, when a thermoplastic film or sheet is uniaxially stretched to form a retardation plate, the retardation plate is arranged under a crossed Nicols so that its optical axis is 45 degrees and measured. It was found that by controlling the color difference (ΔE ^* ) to be 20 or less, an excellent retardation plate without optical color unevenness can be obtained.

As the thermoplastic resin used in the retardation film of the present invention, when formed into a film or sheet, the above properties are satisfied, and the average transmittance in the visible light wavelength range of 400 to 700 nm is 50% or more, It is not particularly limited as long as it shows 80% or more, more preferably 85% or more, and it can be applied to the present invention.

For example, poly (meth) acrylate resin such as methyl methacrylate copolymer obtained by copolymerizing polymethylmethacrylate or methylmethacrylate as a main component with another ethylene-based comonomer, polystyrene or styrene as a main component. A polystyrene resin such as a styrene copolymer obtained by copolymerizing with another ethylene comonomer,
Acrylonitrile-based resins such as polyacrylonitrile and acrylonitrile copolymers, polyester-based resins such as polyethylene terephthalate and polyester copolymers, polyamide-based resins such as nylon 6 and nylon 66, polychlorinated polyvinyl chloride and vinyl chloride copolymers Vinyl resin, polyolefin resin such as polyethylene, polypropylene, ethylene copolymer, propylene copolymer, polysulfone, polyether sulfone, fluorine resin, polycarbonate resin and the like, and modified products thereof.
And at least one resin material selected from blends of these resins with a transparent low-molecular compound such as a high-molecular liquid crystal or a low-molecular liquid crystal or a transparent inorganic compound.

Among them, preferred resins include polyethylene terephthalate, polyester resins such as polyester copolymers,
Polyvinyl chloride resin such as porsulphone, polyvinyl chloride, vinyl chloride group polymer, acrylonitrile resin,
Examples thereof include polycarbonate resins.

In order to improve the display quality of a liquid crystal display device, the retardation plate of the present invention has an α value defined by the following formula (1) of 1.00 or more,
Preferably, a thermoplastic resin showing 1.03 or more is used.

Here, R _F : Retardation value measured with hydrogen F line (486.1 nm) R _D : Retardation value measured with sodium D line (589.3 nm) Display when the retarder is applied to STN type liquid crystal display device The α value dependency of quality will be described using an example.

The light transmittance (T) of the optical system when the birefringent body depends on the optical axis at 45 degrees under parallel Nicols is expressed by the following equation (2).

Tr: transmittance of birefringent material Tp: transmittance when two polarizing plates are arranged in parallel Rr: retardation of birefringent material (nm) λ: wavelength of light (nm) Twist angle of liquid crystal is about 200 And a product of the birefringence of the liquid crystal and the thickness (Δn × d) is about 850 nm, a pair of polarizing plates are arranged in parallel Nicols on both sides of the liquid crystal cell, and the upper polarizing plate and the liquid crystal are arranged. The display quality is improved in the STN type liquid crystal display device having a structure in which a retardation plate (retardation is about 550 nm) is arranged between cells at about 45 degrees with respect to the polarization axis. That is, the coloring disappears and the background color becomes white. It is preferable that the background color be as clear as white, which is excellent in display quality, and in the formula (2), the condition that the light transmittance is constant in the wavelength range of visible light, that is, if T = constant, the background The color is completely white.

In the equation (2), the condition that T = constant is And the retardation Rc of the composite of the liquid crystal cell and the retardation plate is Rc = 0 (4), and the value of R changes according to the wavelength λ of the light,
As shown in (3), when R of the liquid crystal cell is compensated by R of the retardation plate and T = constant in all wavelength regions of visible light, a perfect white background color is obtained and display quality is good.

1 to 3 show spectra of transmitted light of the STN type liquid crystal display device when the value of α of the retardation plate was changed to 1.00, 1.03 and 1.06. It can be seen that the larger the value of α, the closer to perfect white the display is.

As is clear from the above description, the α value of the retardation plate used for the liquid crystal display is better than 1.00 for better display quality,
It is preferably 1.03 or more. The thermoplastic polymer having an α value of 1.03 or more, which is a preferable range, is a polymer compound containing an aromatic ring in the main repeating unit of the polymer or a polymer having a polar group such as a halogen atom or a nitrile group. A compound can be illustrated. These polymer compounds include polysulfones having aromatic rings, polyether sulfones, polyether ether ketones, polyarylates, polyesters,
Examples thereof include polymer compounds such as polystyrenes and polycarbonates, fluororesins such as acrylonitrile polymers and trifluoromonochloride ethylene polymers, polyvinyl chloride and the like. Further, modified products and mixtures of these polymer compounds can be appropriately used as necessary. Further, even if it is a thermoplastic resin having an α value of 1.03 or less alone, the retardation plate of the present invention can be obtained by blending with a low molecular weight liquid crystal or a high molecular weight liquid crystal having a large α value.

A method of using the thermoplastic polymer compound as a retardation plate will be described below. The retardation plate of the present invention is formed into a raw film or sheet by a known film forming method of the thermoplastic polymer, that is, a solvent casting method, a calendering method, or an extrusion method, and then appropriately stretched in a uniaxial direction. Is manufactured by

In order to obtain a retardation plate having a constant optical axis and little optical color unevenness, the original film or sheet is required to have good thickness accuracy and be as optically uniform as possible.
It is not preferable that a die line or the like is formed on the film or sheet during molding. Usually, when a film or sheet is molded, minute orientations often occur, and it is also a preferable method to reduce these minute orientations before stretching. Heat treatment is effective as a method of reducing the fine orientation before stretching. In order to manufacture the retardation plate of the present invention,
Before stretching, heat treatment is performed at a temperature equal to or higher than the heat distortion temperature of the film or sheet.

When the heat treatment is performed, the birefringence of the original film or sheet becomes substantially 0, and the film or sheet becomes almost completely non-oriented.

As a method for uniaxially stretching the raw film or sheet thus obtained, a uniaxial transverse uniaxial stretching method by a tenter method, a roll-to-roll compression stretching method, a longitudinal uniaxial stretching method using rolls having different peripheral speeds, etc. are known. The uniaxial stretching method can be adopted.

In the present invention, in order to obtain a retardation plate having a small color unevenness optically and a small swing of retardation, a neck-in ratio (100 which is defined by a film width A before stretching and a film width B after stretching (100 It is necessary to suppress x (A−B) / A) to 10% or less, preferably 5% or less, and more preferably substantially 0. Therefore, the most effective stretching method in the present invention is the lateral uniaxial stretching method by the tenter method in which neck-in does not substantially occur.

The transverse uniaxial stretching by the tenter method generally includes three steps of a preheating step, a stretching step and a heat treatment step. The preheating step is useful because it has the same role as the heat treatment step for making the birefringence of the film or sheet substantially zero. The stretching step is the most important step for forming a retardation plate, and it is necessary to change the processing conditions depending on the type and thickness of the thermoplastic resin used, the required retardation value and the like.

The heat treatment step after stretching is a useful step for improving the dimensional stability of the obtained stretched film or sheet and for improving the uniformity of retardation.

In the present invention, the average transmittance in the visible light wavelength range of 400 to 700 nm is defined as follows. That is, 10 nm in the range of 400 to 700 nm with a spectrophotometer or spectrometer.
It is a value obtained by measuring the transmittance for each and averaging the transmittances at 31 points obtained. Since this retardation plate is used for optical purposes,
The average light transmittance is preferably as high as possible, and usually 50% or more, preferably 80% or more is necessary.

The optical color unevenness referred to in the present invention is ΔE ^* defined below ^.
Can be displayed quantitatively. That is, L ^* when placed so that its optical axis is 45 degrees under orthogonal Nicols,
The values of a ^* and b ^* are measured by a spectrophotometer or a spectrophotometer according to JIS Z8729 (display method of object color by L ^* u ^* v ^* color system). The above L ^* , a ^* , for n different sample locations
Calculate (ΔE ^* ) i, j from b ^* by the following formula.

(ΔE ^* ) i, j = (((ΔL ^* ) i, j) ² + ((Δa ^* ) i, j) ² + ((Δb ^* ) i, j) ² 1/2 where (ΔL ^* ) i , j = (L ^* ) i− (L ^* ) j (Δa ^* ) i, j = (a ^* ) i− (a ^* ) j (Δb ^* ) i, j = (b ^* ) i− (b ^* ) J i = 1 to n j = 1 to n i ≠ j The maximum value among these (ΔE ^* ) i, j is ΔE ^* . The sample is randomly sampled at 10 points and measured by the above formula. The smaller ΔE ^* is, the smaller the optical color unevenness is, so the smaller the ΔE ^{*, the} more preferable it is. Therefore, the value of ΔE ^* must be 20 or less.

The retardation plate thus obtained can be applied to new uses such as a composite polarizing plate and a liquid crystal display device as well as an optical filter.

The retardation plate according to the present invention can also be applied to a liquid crystal display device or the like by laminating it on one surface of a polarizing plate to form a composite polarizing plate.

As the polarizing plate constituting the composite polarizing plate of the present invention, any polarizing plate can be used. For example, polyvinyl alcohol, or a film made of a derivative thereof is uniaxially stretched and oriented, and after adsorbing iodine or a dichroic dye as a polarizing element, a non-optically rotating cellulose-based film such as cellulose triacetate is used. It is pasted on both sides. Furthermore, a dichroic dye was blended with a hydrophobic resin such as a polyene-based polarizing plate or polyethylene terephthalate obtained by dehydrochlorination of a polyvinyl chloride film or a dehydration treatment of a polyvinyl alcohol-based film, and uniaxially oriented. A type polarizing plate or the like can be used. Among them, polyvinyl alcohol film, iodine or dichroic dye is adsorbed, the one having a cellulose-based film such as cellulose triacetate adhered on both sides as a protective film to the uniaxially oriented polarizer has a polarizing property, It is preferable in terms of hue characteristics.

To form the composite polarizing plate of the present invention using the retardation plate of the present invention and the polarizing plate, the optical axis of the polarizing plate and the optical axis of the retardation plate are
15-75 degrees, preferably 30-60 degrees, more preferably 40-
It is achieved by sticking together using an adhesive or an adhesive in the range of 50 degrees.

Furthermore, the protective film on one side of the linear polarizing plate is removed, and a structure in which a retardation plate is directly attached to the polarizer by using an adhesive or an adhesive, a protective polymer-free hydrophobic polymer film A linear polarizing plate composed of a combination of chromatic dyes and a structure in which a retardation plate is attached to one side of the linear polarizing plate using an adhesive or a pressure sensitive adhesive is also included in the scope of the composite polarizing plate of the present invention. .

The retardation plate of the present invention has a twist angle of liquid crystal molecules of 90 degrees or more, specifically, arranged on one surface of a liquid crystal cell of about 180 to 270 degrees, and a pair of polarizing plates is arranged so as to sandwich them. Thus, the liquid crystal display device of the present invention is obtained. At this time, the display quality is improved by bonding the retardation plate and the polarizing plate so that their optical axes fall within the range of 30 to 60 degrees, preferably 40 to 50 degrees. By arranging the pair of polarizing plates so that their optical axes are orthogonal, or nearly orthogonal, or parallel or nearly parallel, good display quality can be obtained.

〔The invention's effect〕

The retardation plate or composite polarizing plate thus obtained has good optical performance and at the same time 80 ° C. and 60 ° C. ×
It can pass the durability promotion test at 90% RH.
Therefore, when these are used in a liquid crystal display device having a twist angle of liquid crystal molecules of 90 degrees or more, specifically about 180 to 270 degrees, a liquid crystal display device of the present invention having a highly reliable and high quality black and white display is obtained. can get. In addition, it can be applied to various optical filters.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. The present invention is not limited to these. In addition, the measurement of the retardation value of the retardation plate in the example uses a Senarmont compensator (546 nm) provided in a polarization microscope,
A halogen lamp was used as the light source. ΔE ^* was measured and calculated by the above method using a spectrophotometer.

The value of α of the retardation plate defined by the equation (1) was obtained by the following procedures (I) to (IV) using an Abbe refractometer.

(I) Using the D line of sodium (589.3 nm), the refractive index n _{D1 in} the ray direction and the refractive index n _{D2 in the} direction orthogonal thereto were measured, and the letter was measured at 589.3 nm by the following formula (2). Calculate the foundation value R _D.

R _D = | n _D1 −n _D2 | × d (2) d: Thickness of retardation plate (nm) (II) Apparent refractive index n in the optical axis direction using F line (486.1 nm) of hydrogen _F1 and the apparent refractive index n _F2 in the direction orthogonal thereto are measured, and the actual refractive indices N _F1 and N _F2 are calculated by the following equations (3) and (4).

However, P is the refractive index of the main prism of the refractometer at 486.1 nm, and the value calculated by the following equation (5) was used.

(III) Using the values of N _F1 and N _F2 , the retardation value R _F measured at 486.1 nm is calculated by the following formula (6).

R _F = | N _F1 −N _F2 | × d (6) d: Thickness of retardation film (nm) (IV) Using the values of R _F and R _D , the value of α is calculated by equation (1). calculate.

Further, the linear polarizing plate in the examples is, for example, JP-A-61-200.
It is prepared by a method as described in JP-A No. 03, in which polyvinyl alcohol is uniaxially adsorbed and oriented as a dichroic dye. If necessary, a transparent non-optically rotating polymer film such as cellulose triacetate is laminated as a protective film.

Example 1 A polycarbonate film (molecular weight: about 26,000) having a thickness of 300 μm and a width of 300 mm was preheated at a temperature of 190 ° C. and then 1
Lateral uniaxial stretching was performed by a tenter method at a temperature of 75 ° C. to obtain a stretched film having a thickness of about 200 μm and a width of 450 mm. The stretched film has a light transmittance of about 91%, an α value of about 1.06, and an R value of about 56.
A retardation plate of the present invention having a uniform quality of 0 nm and ΔE ^* of 7.5 and having almost no optical color unevenness was obtained. The retardation plate was attached to one surface of the polarizing plate with an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees to obtain a composite polarizing plate of the present invention. Furthermore, the twist angle of the liquid crystal molecules is about 200
When the liquid crystal cell of the liquid crystal display device in which the liquid crystal Δn × d is about 850 nm and the upper polarizing plate are pasted together with an adhesive, the background color is white and the display part is almost black and white. A liquid crystal display device of the present invention having a good display quality without any color unevenness such as a rainbow pattern was obtained.

Example 2 A polyester copolymer film (PETG6763, Eastman Chemical Co.) having a thickness of 400 μm and a width of 300 mm was preheated at a temperature of 135 ° C. and then uniaxially stretched by a tenter method at a temperature of 120 ° C. About 250 μm, width 480 mm
To obtain a stretched film. The stretched film had a light transmittance of about 89%, an α value of about 1.06, an R value of 535 nm, and a ΔE ^* of 11.0, which showed uniform quality and gave the retardation plate of the present invention having almost no optical color unevenness. It was When applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of the present invention having good display quality was obtained as in Example 1.

Example 3 A polyvinyl chloride film (SANLOID VIPCHA150, manufactured by Tsutsunaka Plastic Industry Co., Ltd.) having a thickness of 250 μm and a width of 300 mm was used as 1
After preheating at a temperature of 10 ° C, transverse uniaxial stretching by a tenter method is performed at a temperature of 100 ° C, and the thickness is about 140μ.
A stretched film having a width of m and a width of 540 mm was obtained. The stretched film has an α value of about 1.04, a light transmittance of 87%, an R value of about 300 nm, and a ΔE
^{* Indicates} a retardation plate of the present invention having a uniform quality of 8.0 and almost no optical color unevenness. This retardation plate was attached to one surface of the polarizing plate using an acrylic pressure-sensitive adhesive so that the optical axis was about 45 degrees, to obtain a composite polarizing plate of the present invention. Furthermore, this retardation plate is used by pasting an adhesive between the liquid crystal cell and the upper polarizing plate of the liquid crystal display device in which the twist angle of the liquid crystal molecule is about 180 degrees and the liquid crystal Δn × d is about 950 nm. As a result, a liquid crystal display device of the present invention having a white background and a black and white display with almost no black-and-white display, no color unevenness such as a rainbow pattern, and good display quality was obtained.

Example 4 A polysulfone film (Sumilite FS-1200, manufactured by Sumitomo Bakelite) having a thickness of 150 μm and a width of 300 mm was preheated at a temperature of 230 ° C. and then laterally uniaxially stretched by a tenter method at a temperature of 210 ° C. to a thickness of about 75 μm. A stretched film having a width of 600 mm was obtained. The stretched film had an α value of about 1.10, a light transmittance of about 89%, an R value of about 590 nm, and a ΔE ^* of 9.5, which had a uniform quality and had almost no optical color unevenness. I got a plate. When applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of the present invention having good display quality was obtained as in Example 1.

Example 5 A polyethylene terephthalate film having a thickness of 200 μm and a width of 300 mm was preheated at a temperature of 210 ° C. and then laterally uniaxially stretched by a tenter method at a temperature of 195 ° C. to a thickness of about 14
A stretched film of 0 μm and a width of 430 mm was obtained. The stretched film has a light transmittance of about 90%, an α value of about 1.05 and an R value of about 915n.
m and ΔE ^* were 12.8, and the retardation plate of the present invention having uniform quality and almost no optical color unevenness was obtained. The optical axis of this retardation plate is approximately one side of the polarizing plate using an acrylic adhesive.
The composite polarizing plate of the present invention was obtained by sticking at 45 degrees.

Furthermore, this retardation plate is used by pasting an adhesive between the liquid crystal cell and the upper polarizing plate of the liquid crystal display device in which the twist angle of the liquid crystal molecules is about 220 degrees and the liquid crystal Δn × d is about 800 nm. As a result, a liquid crystal display device having a good display quality without a color unevenness such as a rainbow pattern, which is a substantially monochrome display with a white background and a black display portion, was obtained.

Comparative Example 1 When a retardation plate made of cellulose diacetate and having a thickness of about 400 μm (α value of about 0.96, R value of about 525 nm) was applied to a liquid crystal display device in the same manner as in Example 1, it was found to be Example 1. In comparison, only a liquid crystal display device having a poor contrast was obtained.

Comparative Example 2 A retardation plate made of polypropylene and having a thickness of about 20 μm (α value of about 0.99, R value of about 610 nm) was prepared in the same manner as in Example 1,
When applied to a liquid crystal display device, as compared with Example 1,
Only a liquid crystal display device having poor contrast was obtained. Example 6 75 wt% of polyvinyl chloride and 25 wt% of a polymer liquid crystal compound represented by the following formula (7) were blended at 150 ° C. and then formed into a film of about 200 μm. Roll temperature 100 ℃, linear pressure 200kg / cm
Under the conditions of, compression stretching is performed between a pair of rolls, and the thickness is about
A 100μ stretched film was obtained. (Neck-in rate 2%) The stretched film has a light transmittance of about 87%, an α value of about 1.06, R
The value was about 240 nm and ΔE ^* was 17.8, and the retardation plate of the present invention with little optical color unevenness was obtained.

Example 7 Polycarbonate (molecular weight: about 16,000) and styrene / maleic anhydride copolymer (styrene / maleic anhydride (weight ratio) = 92/8) were uniformly blended in a weight ratio of 80:20. 18 mm transparent film with a width of 200 μm and a width of 300 mm
After preheating at a temperature of 0 ° C., transverse uniaxial stretching was performed at a temperature of 155 ° C. by a tenter method to obtain a stretched film having a thickness of about 135 μm and a width of 515 mm. The stretched film has an α value of about 1.05,
R value is about 460 nm, ΔE ^* is 8.8, and it has uniform quality,
A retardation plate of the present invention having almost no optical color unevenness was obtained.
This retardation plate was attached to a polarizing plate using an acrylic pressure-sensitive adhesive so that their optical axes would be about 45 degrees to obtain a composite polarizing plate of the present invention. When applied to a liquid crystal display device in the same manner as in Example 1, a liquid crystal display device of the present invention having good display quality was obtained as in Example 1.

Example 8 A polymethylmethacrylate film having a thickness of about 220 nm and a width of 300 mm (extruded film of Sumipex-MMO, trade name, manufactured by Sumitomo Chemical Co., Ltd.) was preheated at about 90 ° C., and then 80
Horizontally uniaxially stretched by the tenter method at a temperature of about 150μ
A stretched film having a width of m and a width of about 440 mm was obtained.

This stretched film has an R value of about 570 nm, a ΔE ^* value of 7.2, a light transmittance of about 90%, and an α value of about 1.01, showing uniform quality and good phase difference with almost no optical color unevenness. I got a plate.

Example 9 Low-density polyethylene with a thickness of 60 μm (Sumitomo Chemical Co., Ltd.)
The registered trademark Sumikasen F208-1) film is compressed and stretched between a pair of rolls under the conditions of a roll temperature of 100 ° C. and a linear pressure of 250 kg / cm to obtain a stretched film having a thickness of 15 μm and a neck-in rate of 3%. It was

The obtained stretched film has an R value of about 630 nm and a ΔE ^* value of 14.
4. The light transmittance was about 86%, and the α value was about 1.00, showing uniform quality, and a good retardation plate with almost no optical color unevenness was obtained.

Example 10 Using the same raw polysulfone film as in Example 4,
After preheating at 215 ℃, uniaxially longitudinally stretched between rolls with different peripheral speeds, thickness of about 70 μm, neck-in ratio 6%
To obtain a stretched film.

This stretched film has a light transmittance of about 88% and an R value of about 560n.
m and ΔE ^* were 15.0, showing uniform quality, and a good retardation plate with almost no optical color unevenness was obtained.

Example 11 The retardation plate obtained in each of Examples 8 to 10 was provided between a liquid crystal cell and an upper polarizing plate of a liquid crystal display device in which the twist angle of liquid crystal molecules is about 200 degrees and Δn × d of the liquid crystal molecules is about 850 nm. When the liquid crystal display device was pasted through an adhesive and used, a liquid crystal display device of good display quality was obtained, showing a substantially black and white display with a white background and a black display portion and no uneven color such as a rainbow pattern. Above all, the α value is 1.03
Excellent display quality was obtained when the retardation plate shown above was used.

Comparative Example 3 In Example 10, stretching was performed by increasing the distance between the rolls of the longitudinal uniaxial stretching device to obtain a stretched film having a thickness of about 80 μm. (Neck-in rate 30%) The stretched film had a light transmittance of about 88% and an R value of about 720 nm, but ΔE ^* was 32.
It was 4, and only a retardation plate with large optical color unevenness was obtained. When the retardation plate was applied to the same liquid crystal display device as in Example 11, color unevenness such as a rainbow pattern was large and the display quality was rather deteriorated.

Comparative Example 4 250 μm thick polyester copolymer film (Example 2
The same drawing apparatus as in Comparative Example 3 was used,
Was uniaxially stretched to obtain a 170 μ stretched film.
(Neck-in rate 40%), the stretched film had a light transmittance of about 89% and an R value of about 490 nm, but ΔE ^* was 34.5 and only a retardation plate with large optical color unevenness was obtained. . When the retardation plate was applied to the same liquid crystal display device as in Example 11, color unevenness such as a rainbow pattern was large and the display quality was rather deteriorated.

Example 12 The same polycarbonate film as in Example 1 was preheated at a temperature of 185 ° C. and then transversely uniaxially stretched by a tenter method at a temperature of 175 ° C. to obtain a stretched film having a thickness of about 160 μ and a width of 560 mm. The stretched film has a light transmittance of about
A retardation plate of the present invention having 91%, an α value of about 1.06, an R value of about 885 nm, and a ΔE ^* of 9.3, having uniform quality and having almost no optical color unevenness was obtained. When applied to a liquid crystal display device in the same manner as in Example 5, a liquid crystal display device having good display quality without white spots such as a rainbow pattern and a substantially black-and-white display with a black background is obtained. It was

Example 13 A polycarbonate film (molecular weight: about 26,000) having a thickness of 200 μm and a width of 300 mm was preheated at a temperature of 190 ° C., then transversely uniaxially stretched by a tenter method at a temperature of 175 ° C., and then heat treated at 180 ° C. for 2 minutes. Was done. The stretched film has a light transmittance of about 91%, an α value of about 1.06, an R value of about 60 nm, and a ΔE ^* of 13.1 with uniform quality and almost no optical color unevenness. Obtained.

Example 14 A transparent polycarbonate film having a thickness of 100 μm and a width of 500 mm was preheated at a temperature of 160 ° C., and then stretched uniaxially in the longitudinal direction between rolls having the same peripheral speed as in Example 10, and a thickness of about 60 μm. A stretched film having a width of 465 mm (neck-in rate 7%) was obtained. The film has an R value of about 500 nm and a ΔE
^* Indicates uniform quality at 15.1, and a good retardation plate with almost no optical color unevenness was obtained.

Example 15 A transparent polycarbonate film having a thickness of 100 μm and a width of 500 mm was preheated at a temperature of 170 ° C., and then stretched uniaxially in the longitudinal direction between rolls having the same peripheral speed as in Example 10, to obtain a thickness of about 60 μm. A stretched film having a width of 465 mm (neck-in rate 7%) was obtained. The film has an R value of about 255 nm and a ΔE
^* Indicates uniform quality at 14.8, and a good retardation plate with almost no optical color unevenness was obtained.

[Brief description of drawings]

In all of Figures 1 to 3, the liquid crystal twist angle is about 200.
A pair of polarizing plates are placed in parallel Nicol state on both sides of the liquid crystal cell where the value of Δn × d of the liquid crystal is about 850 nm, and the R value is about 550 nm between the upper polarizing plate and the liquid crystal cell. 7 shows a transmitted light spectrum in an STN type liquid crystal display device having a structure in which a retardation plate is arranged. However, the α value of the retardation film is 1.00 in FIG. 1, 1.03 in FIG. 2 and 1.06 in FIG.

Continuation of front page (31) Priority claim number Japanese Patent Application No. Sho 63-89478 (32) Priority date Sho 63 (1988) April 11 (33) Country of priority claim Japan (JP) Judgment No. 5-5710 (72) ) Inventor Toyokazu 2-10-1 Tsukahara, Takatsuki City, Osaka Prefecture Sumitomo Kagaku Kogyo Co., Ltd. (72) Inventor Kazuaki Sakakura 2-10-1, Tsukahara Takatsuki City, Osaka Sumitomo Kagaku Kogyo Co., Ltd. ( 72) Inventor Koji Higashi, 2-10-1, Tsukahara, Takatsuki City, Osaka Prefecture, Sumitomo Chemical Co., Ltd. (56) Reference JP 61-25105 (JP, A) JP 61-231503 (JP, A) ) JP-A 64-519 (JP, A)

Claims (4)

[Claims] 1. A polymer film or sheet formed by uniaxially stretching a thermoplastic polymer film or sheet so as to have a neck-in ratio of 10% or less, and having a birefringence (Δn) and a thickness. The retardation (Δn × d) defined by the product of (d) is in the range of 200 to 1000 nm, and the film or sheet is placed under a crossed Nicols so that its optical axis is 45 degrees. A retardation plate having a color difference (ΔE ^* ) of 20 or less when measured by. 2. The retardation plate according to claim 1, wherein the α value defined by the formula (1) is 1.00 or more. R _F : Retardation value measured with hydrogen F line (486.1 nm) R _D : Retardation value measured with sodium D line (589.3 nm) 3. A composite polarizing plate obtained by laminating the retardation plate according to claim 1 on a polarizing plate. 4. A liquid crystal display device in which the retardation plate according to claim 1 is laminated on one surface of a liquid crystal cell, and a pair of polarizing plates are laminated so as to sandwich it.