JP3431255B2 - Retardation film - Google Patents

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 or TFT type liquid crystal display devices are generally used for large-sized liquid crystal display panels, and such display devices use a retardation film made of a polymer uniaxially stretched film or an optically isotropic film. 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 or 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 retardation film made of an aromatic polycarbonate resin, which has sufficient hue compensation, does not cause inconveniences such as color shift and bleeding, and solves the problem of poor color accuracy of conventional color display. The purpose is to provide.

The present inventor has conducted earnest studies to achieve the above object, and as a result, obtained a retardation film obtained by stretching a film made of an aromatic polycarbonate resin having a specific viscosity, which is obtained by using a specific dihydric phenol. It was surprisingly found that the above problems could be solved by using them, and the present invention was completed based on this finding.

[0005]

The present invention provides 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,
At least one kind of 3,5-trimethylcyclohexane, 4,4′-dihydroxytetraphenylmethane, and 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane 50 to 100 mol% and 2,2- Bis (4-hydroxyphenyl) propane less than 50 mol% to 0 mol%
And a film of an aromatic polycarbonate resin having a specific viscosity of 0.364 or more, which is obtained by reacting a carbonate precursor with a dihydric phenol consisting of the above-mentioned.

The divalent phenol used in the synthesis of the aromatic polycarbonate resin constituting the retardation film of the present invention includes 1,1-bis (4-hydroxyphenyl) -1-phenylethane and 1,1-bis ( 4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane,
4,4'-dihydroxytetraphenylmethane, 1,3
-Bis (4-hydroxyphenyl) -5,7-dimethyladamantane, which may be used alone or in combination of two or more kinds. Further, a part of the divalent phenol is 2,2-bis (4-hydroxyphenyl) within a range where the properties of the obtained aromatic polycarbonate resin as a retardation film are not impaired, that is, less than 50 mol% thereof. It may be replaced with propane (hereinafter abbreviated as bisphenol A). It is also possible to branch by using a small amount of a tri- or higher functional compound at the same time.

The reaction with the carbonate precursor for synthesizing the aromatic polycarbonate resin using the above dihydric phenol is a reaction used when synthesizing a usual aromatic polycarbonate resin, for example, the reaction between dihydric phenol and phosgene, Alternatively, a transesterification reaction between a dihydric phenol and a bisaryl carbonate is preferably used. Examples of carbonate precursors include phosgene, bischloroformates of the above dihydric phenols, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-
Examples thereof include tolyl carbonate, di-p-chlorophenyl carbonate, dinaphthyl carbonate, etc. Among them, phosgene and diphenyl carbonate are preferable.

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, 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, to such an aromatic polycarbonate resin, various additives such as a stabilizer, a lubricant, a release agent, a flame retardant, an antistatic agent, a weathering agent and the like may be added within a range that does not impair the gist of the present invention. Other polymers may 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 as it is or in at least a uniaxial direction so as to have optimum birefringence properties. 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.

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 variation of the retardation becomes too large, a deviation of the hue compensation will occur, resulting in a color spot. Therefore, the variation rate is preferably 10% or less, particularly preferably 5% or less, and 2
% Or less is more preferable. Film thickness is 5-300μ
A range of m is preferred.

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 arranged on one side or both sides of a liquid crystal cell, by disposing the retardation film between the polarizing plate on the viewing surface side and the liquid crystal cell, birefringence of liquid crystal is obtained. 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.

[0016]

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

Synthesis Example 1 A reaction tank equipped with a stirrer, a thermometer and a reflux condenser was charged with 2738.4 parts of a 48.5% aqueous sodium hydroxide solution and 23800 parts of water, and nitrogen gas was bubbled for 30 minutes. Deoxygenated. 1,1-
Dissolve 3566 parts of bis (4-hydroxyphenyl) -1-phenylethane, add 7.1 parts of hydrosulfite, and similarly add 16700 parts of methylene chloride deoxygenated by nitrogen gas bubbling and add 1400 parts of phosgene at 20 ° C. Was blown in for about 60 minutes. Then, 506.8 parts of a 48.5% sodium hydroxide aqueous solution which was deoxygenated in the same manner, and
36.9 parts of p-tert-butylphenol was added for emulsification, 11 parts of triethylamine was added, and the mixture was stirred at 30 ° C. for about 2 hours to complete the reaction. After completion of the reaction, the organic phase is separated, washed with water, acidified with hydrochloric acid and repeatedly washed with water. Parts (yield 98%) were obtained. The specific viscosity of this polymer is 0.4
It was 64.

[Synthesis Example 2] 1,62 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane in place of 3,566 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane and 2,2 Synthesis Example 1 except that 1262 parts of 2-bis (4-hydroxyphenyl) propane was used
In the same manner as in (3), 3437 parts of polymer (yield 97%) was obtained. The specific viscosity of this polymer was 0.471.

[Synthesis Example 3] A device similar to that of Synthesis Example 1 is used.
Charge 569 parts of 8.5% sodium hydroxide aqueous solution and 3374 parts of ion-exchanged water, 226.6 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane and 2,2-
After dissolving 157.7 parts of bis (4-hydroxyphenyl) propane, 0.8 part of hydrosulfite was added,
Further, 1692 parts of methylene chloride was added, and 195 parts of phosgene was blown thereinto at about 23 ° C. over about 60 minutes while stirring. Then p
After adding 2.2 parts of -tert-butylphenol and emulsifying the mixture, 0.5 part of triethylamine was added and stirred at about 30 ° C. for 2 hours to complete the reaction. After the completion of the reaction, the same treatment as in Synthesis Example 1 was carried out to obtain 415.7 parts of a polymer (yield 98%). The specific viscosity of this polymer was 0.891.

[Synthesis Example 4] The same apparatus as in Synthesis Example 1 was
Charge 464 parts of 8.5% sodium hydroxide aqueous solution and 2213 parts of ion-exchanged water, dissolve 389 parts of 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, and add hydrosulfite 0.2. After adding 4 parts, 1380 parts of methylene chloride was added, and 149 parts of phosgene was blown in at 20 ° C. over about 60 minutes. Then p-te
After adding 5.7 parts of rt-butylphenol and emulsifying,
0.4 part of triethylamine was added and stirred at about 30 ° C. for 2 hours to complete the reaction. After the completion of the reaction, the same treatment as in Synthesis Example 1 was performed to obtain 403 parts of a polymer (yield 96%). The specific viscosity of this polymer was 0.428.

[Synthesis Example 5] The same apparatus as in Synthesis Example 1 was used.
264 parts of 8.5% sodium hydroxide aqueous solution and 2300 parts of ion-exchanged water were charged, and 1,3-bis (4-hydroxyphenyl) -5.7-dimethyladamantane 380 was added.
Parts and 0.7 parts of hydrosulfite were dissolved, 1620 parts of methylene chloride was added, and 141 parts of phosgene was blown in at 20 ° C. for about 60 minutes. Thereafter, 29 parts of a 48.5% aqueous sodium hydroxide solution and 4.1 parts of p-tert-butylphenol were added to emulsify the mixture, and then triethylamine (0.1 part) was added.
The reaction was completed by adding 8 parts and stirring at about 30 ° C. for 2 hours. After completion of the reaction, the same treatment as in Synthesis Example 1 was carried out to prepare polymer 4
00 parts (yield 98%) were obtained. The specific viscosity of this polymer was 0.375.

[Synthesis Example 6] 2,2-bis (4-hydroxyphenyl) propane 28 instead of 3,566 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane 28
Polymer 3061 parts (98%) was obtained in the same manner as in Synthesis Example 1 except that 03.6 parts were used. The specific viscosity of this polymer was 0.540.

[Examples 1 to 5] A 10% methylene chloride solution of the polymer synthesized in Synthesis Examples 1 to 5 was prepared, cast on a glass plate using a doctor blade, dried and then peeled from the glass to leave a residue. Dry to dryness. 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. 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. Next, when this product was used by pasting it between the liquid crystal cell of the STN liquid crystal display device and the upper polarizing plate, the background color was white,
A black-and-white display with a black display color and 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 by using the polycarbonate made from bisphenol A synthesized 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, we 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 and covering it with a color filter to make the RGB cells emit light, but there was a color shift and bleeding etc. and a clear full color display. I couldn't.

[0025]

[Table 1]

[0026]

INDUSTRIAL APPLICABILITY The retardation film of the present invention, the composite polarizing plate and the liquid crystal display device using the same have few optical spots and can perform clear black and white display and color display. Since it is excellent in performance and durability, it can be applied to a wider range of applications such as in-vehicle use and heat-generating parts, and its effect is exceptional.

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Claims (7)

(57) [Claims] 1. 1,1-Bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3 , 5-Trimethylcyclohexane, 4,4′-dihydroxytetraphenylmethane, 1,3-bis (4-hydroxyphenyl) -5,7
-At least one dimethyl adamantane 50-100
Reaction of a carbonate precursor with a dihydric phenol consisting of mol% (excluding 100 mol% of 4,4'-dihydroxytetraphenylmethane) and 2,2-bis (4-hydroxyphenyl) propane of less than 50 mol% to 0 mol%. The value of the retardation obtained by orienting a film made of an aromatic polycarbonate resin having a specific viscosity of 0.364 or more obtained in at least uniaxial direction is 60 to 1200 nm and the variation rate of the retardation is 10% or less. Phase difference film. 2. The retardation film according to claim 1, wherein the method for orienting the film in the uniaxial direction is transverse uniaxial stretching by the Denter method, longitudinal uniaxial stretching by rolls or rolling between rolls. 3. The stretching temperature for uniaxial stretching is Tg + of the resin used.
The retardation film according to claim 2, which has a temperature of 10 ° C to Tg + 60 ° C. 4. The retardation film according to claim 2 , wherein the stretching ratio of uniaxial stretching is 1.1 to 4 times. 5. The retardation film according to claim 1, wherein the film has a thickness of 5 to 300 μm. 6. The method of claim 1 to 5 or of a composite polarizer made to further laminated at least on the polarizing plate retardation film according. 7. A liquid crystal display device comprising the composite polarizing plate according to claim 6 arranged in a liquid crystal cell.