JPH07216078A - Phase-contrast film - Google Patents

Abstract

PURPOSE:To obtain a phase-contrast film made of an aromatic polycarbonate resin, capable of easily obtaining a solution cast film, sufficient in hue compensation, causing no trouble such as color drift or blur, and free from the problem of low color accuracy inherent in the conventional color display. CONSTITUTION:This phase-contrast film is obtained by uniaxially or biaxially orienting a film consisting of an aromatic polycarbonate resin >=0.364 in specific viscosity produced by reaction of a carbonate precursor with dihydric phenols composed of 50-99mol% of 2,2-bis(4-hydroxyphenyl)propane and 1-50mol% of at least one kind selected from 9,9-bis(4-hydroxyphenyl)fluorene, 4,4'-biphenol, 4,4'-dihydroxybiphenyl ether, 2,2-bis(3-methyl-4-hydroxyphenyl)propane and 2,2-bis(3-bromo-4-hydroxyphenyl)propane.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a retardation film. More specifically, it relates to a retardation film useful as a component of a liquid crystal display device, a composite polarizing plate using the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art STN type or TFT type liquid crystal display devices are generally used for large liquid crystal display panels, and such display devices are retardation films or optically isotropic films made of uniaxially stretched polymer. It is laminated on one side or both sides of the liquid crystal cell. However, such a display device cannot sufficiently compensate the phase difference caused by the STN cell over all the wavelengths of light depending on the laminated films, and thus the problem that coloring occurs and the contrast ratio becomes low is not enough. I couldn't solve it. In addition, this problem is an obstacle when performing color display by covering the display device with a color filter. In order to solve this problem, it is considered to stack an equivalent liquid crystal cell as an optical compensator or substitute an optical film having the same birefringence, and a uniaxially stretched or biaxially stretched film having various retardation values. Is being considered.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a solution cast film easily, has sufficient hue compensation, and has a color shift.
It is an object of the present invention to provide an aromatic polycarbonate resin retardation film that does not cause the inconvenience such as bleeding and solves the problem of poor color accuracy of conventional color display.

Aromatic polycarbonate resins made from 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), which is a typical aromatic polycarbonate resin, have excellent transparency and appropriate rigidity.
An attempt was made to produce a retardation film with this aromatic polycarbonate resin. However, when a film is produced from this aromatic polycarbonate resin by a solution casting method, the desired film cannot be obtained due to poor solubility in a non-halogen solvent, and gelation occurs even in a halogen solvent, or The cast film obtained is easily whitened, and the retardation film produced from the obtained cast film has a large fluctuation range of the retardation, and when the color display is performed, the hue compensation is insufficient, and color misregistration and bleeding easily occur. The problem arose.

The present inventor has solved the problems of the aromatic polycarbonate resin derived from bisphenol A, and conducted extensive studies as a means to achieve the above object. As a result, a part of bisphenol A was replaced with a specific dihydric phenol. The obtained aromatic polycarbonate resin having a specific viscosity can be easily formed into a film by a solution casting method, and if a retardation film obtained by stretching the obtained cast film is used, the above-mentioned problems are surprisingly solved. Based on this finding, they have completed the present invention.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides 50-99 mol% of 2,2-bis (4-hydroxyphenyl) propane.
And 9,9-bis (4-hydroxyphenyl) fluorene, 4,4'-biphenol, 4,4'-dihydroxybiphenyl ether, 2,2-bis (3-methyl-4-).
Obtained by reacting a carbonate precursor with a dihydric phenol consisting of at least 1 mol% and less than 50 mol% of at least one of hydroxyphenyl) propane and 2,2-bis (3-bromo-4-hydroxyphenyl) propane. The present invention relates to a retardation film in which a film made of an aromatic polycarbonate resin having a specific viscosity of 0.364 or more is oriented in at least uniaxial direction.

The divalent phenol used for synthesizing the aromatic polycarbonate resin constituting the retardation film of the present invention is mainly bisphenol A, and 1 mol% to 5% thereof.
Less than 0 mol% is 9,9-bis (4-hydroxyphenyl) fluorene, 4,4'-biphenol, 4,4'-
Dihydroxybiphenyl ether, 2,2-bis (3-
Methyl-4-hydroxyphenyl) propane, 2,2-
It is a mixture of two or more divalent phenols substituted with at least one of bis (3-bromo-4-hydroxyphenyl) propane. When the amount of the divalent phenol other than bisphenol A is less than 1 mol%, it is difficult to obtain a good film from the obtained aromatic polycarbonate resin by a solution casting method, and the obtained cast film is a retardation film obtained by stretching. Has a large fluctuation range of retardation, and the hue compensation is insufficient in color display, and problems such as color shift and bleeding easily occur. Also, 5
Above 0 mol%, the resulting polymer suffers from other excellent properties of aromatic polycarbonate resins from bisphenol A. Incidentally, a small amount of trifunctional or higher functional compound can be used at the same time for branching.

Examples of the carbonate precursor to be reacted with the dihydric phenol include phosgene, bischloroformate of the dihydric phenols, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate and di-p-. Examples thereof include chlorophenyl carbonate and dinaphthyl carbonate, and of these, phosgene and diphenyl carbonate are preferable.

The reaction with the carbonate precursor for synthesizing the aromatic polycarbonate resin using the above dihydric phenol is the reaction used when synthesizing the aromatic polycarbonate resin from bisphenol A, such as dihydric phenol and phosgene. Or a transesterification reaction between a dihydric phenol and a bisaryl carbonate is preferably used.

The reaction between the dihydric phenol and phosgene is usually carried out in the presence of an acid binder and a solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, pyridine or the like is used. As the solvent, for example, a halogenated hydrocarbon such as methylene chloride or chlorobenzene is used. Further, for the purpose of accelerating the reaction, for example, a tertiary amine, a catalyst such as a quaternary ammonium salt can be used, and as a molecular weight regulator, for example, phenol,
It is desirable to use an end-capping agent such as p-tert-butylphenol. The reaction temperature is usually 0 to 40 ° C., the reaction time is several minutes to 5 hours, and the pH during the reaction is usually preferably kept at 10 or higher.

In the transesterification reaction, the dihydric phenol and bisaryl carbonate are mixed in the presence of an inert gas, and the reaction is usually carried out at 120 to 350 ° C. under reduced pressure. The degree of reduced pressure is changed stepwise, and finally, the phenols produced at 1 mmHg or less are distilled out of the system. The reaction time is usually about 1 to 4 hours. Moreover, you may add a molecular weight regulator and antioxidant as needed.

The molecular weight of the aromatic polycarbonate resin is
0.7 g of the polymer was dissolved in 100 ml of methylene chloride and 2
The specific viscosity measured at 0 ° C. needs to be 0.364 or more. If the specific viscosity does not reach 0.364, the strength of the film becomes insufficient and the stretching process becomes difficult, which is not suitable. An aromatic polycarbonate resin having a specific viscosity of 0.418 to 4.89 is particularly preferable. Further, in such an aromatic polycarbonate resin, various additives such as a stabilizer, a lubricant, a mold release agent, a flame retardant, and the like are added within a range not impairing the gist of the present invention.
Antistatic agents, weathering agents, etc. may be added, and other polymers
Can be added. These additives can be mixed by any method such as a tumbler, a super mixer and a Nauta mixer.

As a method for producing a film from the above aromatic polycarbonate resin, for example, a solution casting method,
A melt extrusion method, a calender method and the like can be mentioned, but a method which is excellent in thickness uniformity and which does not cause optical defects such as gel, spots, fish eyes and scratches is preferable.

The film produced by such a method is
The retardation film is stretched and oriented in at least a uniaxial direction so as to have optimum birefringence characteristics. As the uniaxial stretching method, any method such as a horizontal uniaxial stretching by a tenter method, a longitudinal uniaxial stretching between rolls, or a roll-to-roll rolling method can be used. The stretching conditions are not particularly limited, but the stretching temperature is preferably 10 to 60 ° C. higher than the glass transition temperature of the resin used, and the stretching ratio is preferably about 1.1 to 4 times. After stretching, it is preferable to perform heat treatment in order to improve dimensional stability, uniformity of retardation, and stability. The film thickness is 5
The range of 300 μm is preferred.

If the retardation film thus obtained has a too low retardation value, the function as a retardation film becomes insufficient, and if it is too high, the film must be extremely thick. If it is too thick, the optical uniformity tends to be impaired, and the hue compensation effect tends to decrease, so the range of 60 to 1200 nm is preferable, and the range of 200 to 1000 nm is particularly preferable. Further, if the fluctuation range of the retardation becomes too large, a deviation in hue compensation occurs, causing color spots. Therefore, the fluctuation rate is preferably 10% or less, particularly preferably 5% or less,
2% or less is more preferable.

The retardation film of the present invention is preferably used as a composite polarizing plate by laminating it on a polarizing plate. This composite polarizing plate can be formed by laminating the optical axis of a normal polarizing plate and the optical axis of a retardation film within a range of 40 to 50 degrees in a single layer or multiple layers. This composite polarizing plate has excellent features such as excellent heat resistance and durability, and little change in retardation with time.

Further, in a liquid crystal display panel in which a polarizing plate is disposed on one side or both sides of a liquid crystal cell, by disposing the retardation film between the polarizing plate on the viewing side and the liquid crystal cell, birefringence of liquid crystal It is possible to form a black and white liquid crystal display panel in which coloring due to the above is eliminated. Furthermore, by covering this black and white liquid crystal panel with a color mask, the three RGB colors are developed with a black and white gray density, thereby producing a full color liquid crystal display panel. Can be formed.

[0018]

EXAMPLES The present invention will be further described below with reference to examples. In the examples, parts and% are parts by weight and% by weight.

Synthesis Example 1 A reaction vessel equipped with a stirrer, a thermometer and a reflux condenser was charged with 373.9 parts of a 48.5% sodium hydroxide aqueous solution and 5690 parts of ion-exchanged water and bubbled with nitrogen gas for 30 minutes. And deoxidized. To this, 9,9-bis (4-hydroxyphenyl) fluorene 3
9.7 parts and 2,2-bis (4-hydroxyphenyl)
Dissolve 232.6 parts of propane, add 0.54 parts of hydrosulfite, and similarly add 2540 parts of methylene chloride that has been deoxygenated by bubbling nitrogen gas, and add 157.1 parts of phosgene at 20 ° C for about 60 minutes. I blown in. Then
After 6.8 parts of p-tert-butylphenol was added for emulsification, 0.8 part of triethylamine was added and stirred at 30 ° C. for about 2 hours to complete the reaction. After the completion of the reaction, the organic phase is separated, washed with water, acidified with hydrochloric acid, and repeatedly washed with water. 0.7 part (yield 97%) was obtained. The specific viscosity of this polymer is 0.3
It was 75.

[Synthesis Example 2] The same apparatus as in Synthesis Example 1 was
255.9 parts of an 8.5% aqueous sodium hydroxide solution and 1884.1 parts of ion-exchanged water were charged, and 50 parts of 4,4′-biphenol, 240 parts of 2,2-bis (4-hydroxyphenyl) propane and hydro were added thereto. Sulfite 0.
Six parts were dissolved, 1030 parts of methylene chloride was further added, and 143 parts of phosgene was reacted in the same manner as in Synthesis Example 1. Then, 6 parts of p-tert-butylphenol was added and emulsified, and then 0.5 part of triethylamine was added to obtain 308.1 parts of a polymer (yield 95%) in the same manner as in Synthesis Example 1. The specific viscosity of this polymer was 0.470.

[Synthesis example 3] 4
Charge 892 parts of 8.5% aqueous sodium hydroxide solution and 5132 parts of ion-exchanged water to prepare 2,2-bis (3-bromo-).
254.7 parts of 4-hydroxyphenyl) propane and 2,2-bis (4-hydroxyphenyl) propane 42
After dissolving 7 parts, 1.6 parts of hydrosulfite was added, 1942 parts of methylene chloride was further added, and 312.9 parts of phosgene was reacted in the same manner as in Synthesis Example 1. Then p
After adding 1.8 parts of -tert-butylphenol and emulsifying the mixture, 1.6 parts of triethylamine was added to obtain 712.9 parts of a polymer (yield 96%) in the same manner as in Synthesis Example 1. The specific viscosity of this polymer was 1.059.

[Synthesis Example 4] 4,4'-biphenol 50
Example 2 except that 68.8 parts of 2,2-bis (3-methyl-4-hydroxyphenyl) propane were used in place of parts
332.9 parts of polymer (yield 97%) were obtained similarly to. The specific viscosity of this polymer was 0.478.

[Synthesis Example 5] 2,2-bis (3-bromo-)
4-Hydroxyphenyl) propane 254.7 parts in place of 4,4'-dihydroxybiphenyl ether 94.6
Parts, and the amount of p-tert-butylphenol used was 8.
Polymer 55 was prepared in the same manner as in Synthesis Example 3 except that 8 parts were used.
9.1 parts (yield 96%) was obtained. The specific viscosity of this polymer was 0.542.

[Synthesis Example 6] 9,2-bis (4-hydroxyphenyl) fluorene 39.7 parts and 2,2-bis (4-hydroxyphenyl) propane 232.6 parts in place of 2,2-bis ( 282 parts of polymer (yield 98%) were obtained in the same manner as in Synthesis Example 1 except that 258.4 parts of 4-hydroxyphenyl) propane was used. The specific viscosity of this polymer was 0.540.

Examples 1 to 5 10% 1,3-dioxolane solutions of the polymers synthesized in Synthesis Examples 1 to 5 were prepared,
After casting on a glass plate using a doctor blade, it was dried, peeled from the glass, and dried until the residual solvent disappeared. A uniaxially stretched film was produced from this film using a tenter under the conditions shown in Table 1. The retardation of the obtained film and its variation (%) are shown in Table 1.
It was shown to. These films were adhered to one surface of the polarizing plate with an adhesive so that the optical axis was 45 ° to obtain a composite polarizing plate. Then, this product was pasted and used between the liquid crystal cell of the STN liquid crystal display device and the upper polarizing plate, and a black and white display with a white background and a black display with good contrast was obtained. In addition, a clear full-color display device could be obtained by attaching a backlight to this black and white liquid crystal display, covering the upper part with a color filter, and displaying the RGB cells in black and white gray density.

[Comparative Example 1] A casting film was prepared in the same manner as in Example 1 using the polycarbonate prepared from bisphenol A prepared in Synthesis Example 6, and a uniaxially stretched film was obtained under the conditions shown in Table 1. When this film was used by adhering it between the STN liquid crystal cell and the upper polarizing plate in the same manner as in Example 1, almost black and white display was obtained, but hue compensation was insufficient and color misregistration occurred, resulting in a slightly reddish color tone. Became. In addition, I tried to make a color display by making a liquid crystal display with a backlight with the hue of this black and white display still insufficient, covering it with a color filter and making the RGB cells emit light, but there was a color shift and bleeding, etc. Could not be displayed.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION The retardation film of the present invention is easy to solution cast, and a composite polarizing plate and a liquid crystal display device using the same have few optical spots, which enables clear black and white display and color display. Since it has excellent performance and durability as compared with the conventional liquid crystal display device, it can be applied to a wider range of applications such as in-vehicle use and heat-generating parts, and its effect is remarkable.

Claims (4)

[Claims] 1. 50-99 mol% of 2,2-bis (4-hydroxyphenyl) propane and 9,9-bis (4-)
Hydroxyphenyl) fluorene, 4,4'-biphenol, 4,4'-dihydroxybiphenyl ether,
2,2-bis (3-methyl-4-hydroxyphenyl)
Propane, at least one of 2,2-bis (3-bromo-4-hydroxyphenyl) propane 1 mol% or more to 50
A retardation film obtained by orienting a film made of an aromatic polycarbonate resin having a specific viscosity of 0.364 or more obtained by reacting a carbonate precursor with a dihydric phenol of less than mol% in at least one axial direction. 2. The retardation film according to claim 1, wherein the retardation value of the retardation film is 60 to 1200 nm and the variation rate of the retardation is 10% or less. 3. A composite polarizing plate obtained by laminating at least one layer of the retardation film according to claim 1 or 2 on a polarizing plate. 4. A liquid crystal display device comprising the composite polarizing plate according to claim 3 arranged in a liquid crystal cell.