JPH09323354A - Optical sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light-weight sheet which is hardly broken and is highly pliable, easily workable and further, can be freely shaped as a final finished product by press contacting a molding die with an uneven surface to the surface of the sheet of thermoplastic norbornene resin to form an uneven shape. SOLUTION: This optical sheet is obtained by press contact to a molding die with an uneven surface to the surface of a sheet consisting of thermoplastic norbornene resin to form an uneven shape. When transferring the uneven shape to the sheet consisting of thermoplastic norbornene resin, a method to transfer the uneven shape by increasing the temperature of either of the surface of the sheet or a molding die with an uneven surface, or a method to transfer the uneven shape by increasing the temperatures of both sheet and molding die, is employed. The surface temperature of the thermoplastic norbornene resin or the temperature of the molding die with an uneven surface when the molding die with the uneven surface is press contacted to the thermoplastic norbornene resin sheet, is set higher than the glass transition temperature of the thermoplastic norbornene resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sheet having an uneven surface, and more particularly to an optical sheet which is excellent in heat resistance and optical characteristics and also excellent in productivity.

[0002]

2. Description of the Related Art Transparent plates having an uneven shape are used in a wide variety of applications such as diffusion sheets for various displays such as liquid crystal displays, light collecting sheets, Fresnel lenses, lenticulars and holographic films. Conventionally, a transparent plate having an uneven shape used for these purposes is obtained by applying a photosensitive composition on the surface of a transparent glass substrate and then exposing it to form an uneven pattern on the surface of the glass substrate. Things have been mainly used. However, the transparent plate using these glasses has a problem that the manufacturing process takes time and the productivity of the transparent plate is inferior because it involves the steps of coating and exposing the glass substrate with a photosensitive composition. Further, although the glass substrate has excellent heat resistance and optical characteristics, it is easy to break, is heavy, and lacks flexibility and workability, so that there is a problem in that the shape of the final product such as a portable device is limited. It was Further, in the case of glass, there is a problem that the productivity of the product is lowered because it is difficult to handle it on the roll. In order to solve the above problems, polyethylene terephthalate resin (P
ET), polymethylmethacrylate resin (PMMA),
Alternatively, there is known a method of forming a concavo-convex pattern by pressing a die such as a roll having irregularities on a sheet made of a transparent resin such as a polycarbonate resin (PC) as a raw material. It is widely used for the above applications, and for example, a sheet made of these transparent resins may be used for the purpose of light diffusion or brightness enhancement in a liquid crystal display element. However, P
When ET is used, there is a problem that the image becomes darker or the quality of the image deteriorates as compared with the case of using glass because the light transmittance is small. In addition, PMMA has excellent optical characteristics, but it has poor heat resistance and its dimensions change greatly due to water absorption, which may cause irregularities in the sheet and limit the operating environment of the final product. There was a problem. Furthermore, even in the case of PC,
Since the birefringence is large and the heat resistance is not always sufficient, when the final product is mounted on, for example, an automobile, it is necessary to consider deformation of irregularities and sheet deformation due to heat, and its use is limited. There was such a problem.

[0003]

The present invention has been made against the background of the above-mentioned problems of the prior art, and is more resistant to cracking and lighter in weight than the case where glass is used as a base material, and has flexibility and workability. Since it has a large degree of freedom regarding the shape of the final product and is advantageous in terms of productivity as well, since it uses a base film having optical characteristics similar to glass, it can be used for a wide range of optical applications as in the case of glass. It is an object of the present invention to provide an optical sheet capable of

[0004]

The optical sheet of the present invention comprises:
The sheet is made of a thermoplastic norbornene-based resin, and the surface of a sheet is made to have an uneven shape by pressing a mold having unevenness on the surface of the sheet. The thermoplastic norbornene resin used in the present invention has a norbornane skeleton in its repeating unit. For example, the thermoplastic resin includes a norbornane skeleton represented by any of the general formulas (I) to (IV).

[0005]

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[0006]

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[0007]

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[0008]

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(In the formula, A, B, C and D represent a hydrogen atom or a monovalent organic group.) Examples of the thermoplastic norbornene-based resin which can be used in the present invention include JP-A-60- 168708
JP-A-62-252406, JP-A-62-252406
-252407, JP-A-2-133413, JP-A-63-145324, JP-A-63-2.
Resins described in JP-B No. 64626, JP-A No. 1-240517, JP-B No. 57-8815 and the like can be mentioned.

Specific examples of the thermoplastic norbornene-based resin include at least one tetracyclododecene derivative represented by the following general formula (V) or an unsaturated cyclic compound copolymerizable with the tetracyclododecene. A hydrogenated polymer obtained by hydrogenating a polymer obtained by metathesis polymerization of

[0011]

Embedded image (In the formula, A to D are the same as above.) In the tetracyclododecene derivative represented by the general formula (V), it is preferable that A, B, C and D contain a polar group in order to improve heat resistance and heat resistance. It is preferable from the viewpoint of adhesion with the functional film. Further, the polar group - (CH _{2) n} COOR
¹ (wherein R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, n is an integer of 0 to 10), the hydrogenated polymer obtained has a high glass transition temperature. It is preferable that the compound has-(CH ₂ ) _n COOR.
It is preferable that one polar substituent represented by ¹ is contained per molecule of the tetracyclododecene derivative represented by the general formula (V). In the general formula, R ¹ has 1 to ¹ carbon atoms.
Although it is a hydrocarbon group having 20 carbon atoms, it is preferable in that the hygroscopicity of the obtained hydrogenated polymer becomes smaller as the number of carbon atoms increases, but the number of carbon atoms is increased from the viewpoint of balance with the glass transition temperature of the obtained hydrogenated polymer. It is preferably a chain alkyl group having 1 to 4 or a (poly) cyclic alkyl group having 5 or more carbon atoms,
It is particularly preferably a methyl group, an ethyl group or a cyclohexyl group.

Further, the tetracyclododecene derivative of the general formula (V) in which a hydrocarbon group having 1 to 10 carbon atoms is simultaneously bonded as a substituent to a carbon atom to which a carboxylic acid ester group is bonded, has a hygroscopic property. It is preferable because it lowers it. In particular, the tetracyclododecene derivative of the general formula (V) in which the substituent is a methyl group or an ethyl group is preferable in that the synthesis is easy. Specifically, 8-methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^{2, 5} 1
^7,10 ] dodec-8-ene is preferred. These tetracyclododecene derivatives or mixtures of unsaturated cyclic compounds copolymerizable therewith are disclosed, for example, in JP-A-4-77520.
No. 4, page 4, upper right column, line 12 to page 6, lower right column, line 6, the thermoplastic resin used in the present invention can be obtained by metathesis polymerization and hydrogenation. Further, the glass transition temperature (Tg) of the thermoplastic norbornene-based resin is preferably in the range of 100 ° C to 250 ° C, and particularly preferably in the range of 120 to 200 ° C. If the temperature is less than 100 ° C, the heat resistance of the molded product made of the resin will be poor. On the other hand, when the Tg exceeds 250 ° C., the molding temperature becomes high, and it becomes difficult to obtain a high-quality molded product such that the resin is burnt and colored. The hydrogenation rate of the thermoplastic norbornene-based resin is 50% or higher, preferably 90% or higher, more preferably 98% or higher, as measured by ¹ H-NMR at 60 MHz. The higher the hydrogenation rate, the better the stability to heat and light. In the present invention, the gel content contained in the thermoplastic norbornene-based resin is preferably 5% by weight or less, and particularly preferably 1% by weight.

In the present invention, the thermoplastic norbornene-based resin is added to the thermoplastic norbornene-based resin, if necessary, within the range not impairing the effects of the present invention, such as 2,6-di-t-butyl-4.
-Methylphenol, 2,2'-dioxy-3,3'-
Di-t-butyl-5,5′-dimethylphenylmethane,
Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane,
1,1,3-tris (2-methyl-4-hydroxy-5)
-T-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4)
-Hydroxybenzyl-benzene, stearyl-β-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate, 2,2'-dioxy-3,3'-di-
t-butyl-5,5'-diethylphenylmethane, 3,
9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl], 2,4,8,10-tetraoxpyro [5 , 5] Undecane, Tris (2,4-di-t
-Butylphenyl) phosphite, cyclic neopentanetetraylbis (2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methyl) Phenyl) phosphite, 2,2-methylenebis (4,6-
Di-t-butylphenyl) octyl phosphite can be added. In addition to the above-mentioned antioxidants, the above-mentioned thermoplastic norbornene-based resin may optionally contain an ultraviolet absorber such as p-t-butylphenyl salicylate or 2,2'-dihydroxy-. 4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2
-Hydroxy-4-methoxybenzophenone, 2-
(2'-dihydroxy-4'-m-octoxyphenyl) benzotriazole; stabilizers, antistatic agents, flame retardants, impact resistance improving elastomers and the like can be added. Further, additives such as a lubricant may be added for the purpose of improving processability.

The optical sheet of the present invention is obtained by press-bonding a metal mold having irregularities on the surface of the sheet made of the thermoplastic norbornene-based resin to impart irregularities.
Here, the shape of the mold having irregularities is not particularly limited, and may be a roll shape or a plate shape. As a method for molding an optical sheet from the above-mentioned thermoplastic norbornene-based resin, a usual embossed sheet molding method, for example, a sheet-shaped melt-extruded thermoplastic norbornene-based resin is sandwiched by one or more embossing rolls or has an uneven shape. It is possible to use a method in which the sheet is cooled after pressure-pressing with a stamper die having In the present invention, the concavo-convex shape of the mold used for molding the optical sheet is not particularly limited, and it may be a fine one having a rough surface, a rough pattern, a mat-shaped one or a lenticular lens. It is also possible to use various pattern patterns such as those in which certain peaks are continuously formed, or those in which prism-shaped irregularities are regularly arranged.

In the present invention, when the unevenness is transferred to the sheet made of the thermoplastic norbornene-based resin, a method of transferring the unevenness by raising the temperature of either the sheet surface or the mold having the unevenness, or There is a method of raising the temperature of both the sheet and the mold to transfer the unevenness. The surface temperature of the thermoplastic norbornene-based resin sheet when the mold having irregularities is pressure-bonded to the thermoplastic norbornene-based resin sheet, or the temperature of the mold having irregularities is the glass transition temperature (T
g) +5 to Tg + 150 ° C., preferably Tg + 2
It is 0-Tg + 100 degreeC. When the surface temperature of the thermoplastic norbornene-based resin sheet is lower than Tg + 5 ° C. of the thermoplastic norbornene-based resin sheet, it is difficult to transfer unevenness to the resin surface. Further, when the surface temperature of the thermoplastic norbornene-based resin sheet is lower than Tg of the thermoplastic norbornene-based resin, which is lower than 5 ° C., the viscosity of the surface of the thermoplastic norbornene-based resin sheet increases, and it becomes difficult to relax stress. The sheet remains with residual internal stress (strain), and when heat-processed and molded at the time of secondary molding or the like, the elasticity is recovered and the unevenness of the sheet is likely to disappear. When the surface temperature of the thermoplastic norbornene-based resin sheet greatly exceeds the Tg of the thermoplastic norbornene-based resin + 150 ° C, the thermoplastic norbornene-based resin cannot be smoothly peeled from the uneven mold, and The thermoplastic norbornene-based resin is likely to cause thermal decomposition, resulting in poor quality of the obtained sheet.

The thickness of the optical sheet of the present invention is not particularly limited, but is usually 0.05 to 5.0 mm, preferably 0. 0, from the viewpoint of the balance between mechanical strength and optical characteristics.
It is 1 to 2.0 mm. The optical sheet of the present invention can be used as an ordinary embossed sheet, for example, a surface sheet of various displays such as a liquid crystal display and a transmissive display, a diffusion sheet, a condensing sheet, a Fresnel lens, a lenticular, a holographic film, etc. It is suitable for applications where the properties, moisture resistance and optical properties are strictly required.

[0016]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited by this. In addition,
In Examples, parts and% are based on weight unless otherwise specified. Reference Example 1 8-Methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodeca-3-en 10
2. A toluene solution of 0 g, 60 g of 1,2-dimethoxyethane, 240 g of cyclohexane, 9 g of 1-hexene, and 0.96 mol / l of diethylaluminum chloride.
4 ml was added to an autoclave having a volume of 1 liter. On the other hand, in another flask, 0.1 kg of tungsten hexachloride was added.
20 ml of a 05 mol / l 1,2-dimethoxyethane solution
And 10 ml of a 0.1 mol / l 1,2-dimethoxyethane solution of paraaldehyde were mixed. This mixed solution 4.9
ml was added to the mixture in the autoclave. After sealing, the mixture was heated to 80 ° C. and stirred for 4 hours.
To the obtained polymer solution, a mixed solvent of 2/8 (weight ratio) of 1,2-dimethoxyethane and cyclohexane was added to make the polymer / solvent 1/10 (weight ratio), and then 20 g of triethanolamine was added. Was added and stirred for 10 minutes. 500 g of methanol was added to the polymerization solution, and the mixture was stirred for 30 minutes and allowed to stand. The upper layer separated into two layers was removed, methanol was added again, and the mixture was stirred and allowed to stand, and then the upper layer was removed. The same operation was further performed twice, and the obtained lower layer was cyclohexane, 1,
Dilute appropriately with 2-dimethoxyethane and polymer concentration is 10
% Cyclohexane-1,2-dimethoxyethane solution. 20 g of palladium / silica magnesia [manufactured by Nikki Chemical Co., Ltd., palladium amount = 5%] was added to this solution, and the mixture was reacted in an autoclave at 165 ° C. under a hydrogen pressure of 40 kg / cm ² for 4 hours. Was removed by filtration to obtain a hydrogenated polymer solution. Further, pentaerythrityl-, an antioxidant, was added to this hydrogenated polymer solution.
After adding 0.1% of tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] to the hydrogenated polymer, the solvent was removed at 360 ° C. under reduced pressure. . Next, the molten resin was pelletized by an extruder in an atmosphere under nitrogen, and the weight average molecular weight was 7.0 × 10 ⁴ ,
A thermoplastic resin A having a hydrogenation rate of 99.5% and a glass transition temperature of 168 ° C. was obtained.

Reference Example 2 6-Ethylidene-2-tetracyclododecene was added to (a)
After the metathesis ring-opening polymerization as in the case of -1, hydrogenation was carried out,
Thermoplastic resin B pelletized to have a weight average molecular weight of 5.5 × 10 ⁴ , a hydrogenation rate of 99.5%, and a glass transition temperature of 140 ° C.
I got Example 1 The pellets of the thermoplastic resin A of Reference Example 1 were heated at a temperature of 270 ° C. to 300 ° C. in an extruder cylinder using a 50 mmφ extruder.
The sheet was melt-extruded at a temperature of 180 ° C., nipped and pressed using a roll-shaped mold having a minute unevenness of 180 ° C., and cooled to obtain a sheet having the transferred fine unevenness. This sheet was evaluated for total light transmittance, frontal luminance, and frontal luminance after each of a heat resistance test and a humidity resistance test. Table 1 shows the evaluation results. In addition, each measurement was performed as follows. The total light transmittance ASTM D103 was evaluated. According to the front brightness JIS C7641, a light receiver was installed in front of the seat, and a cold cathode (CDK-C301A manufactured by TDK) was used as a light source for evaluation. Heat resistance test The front brightness after standing for 500 hours in an atmosphere at a temperature of 130 ° C. was evaluated. Humidity resistance test The front luminance was evaluated after standing for 1 week in an atmosphere with a temperature of 60 ° C. and a humidity of 90%.

Example 2 The pellets of the thermoplastic resin B obtained in Reference Example 2 were used in the same extruder as in Example 1 and the cylinder temperature was 240 ° C.
The temperature was set to 280 ° C., melt-extruded, nipped and pressed using a roll-shaped mold having fine irregularities set to 150 ° C., and cooled to obtain a sheet on which the fine irregularities were transferred. This sheet was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results. Comparative Example 1 Polymethylmethacrylate resin (trade name “Acrypet VH”, manufactured by Mitsubishi Rayon Co., Ltd.) was used, and sheet forming was performed in the same manner as in Example 1 except that the cylinder temperature was 210 to 230 ° C. and the roll temperature was 120 ° C. The same evaluation as in Example 1 was performed. Table 1 shows the evaluation results.

Comparative Example 2 Polycarbonate resin (trade name "Panlite", manufactured by Teijin Chemicals Ltd.) was used, and the cylinder temperature was 250 to 270.
Sheet molding was performed in the same manner as in Example 1 except that the roll temperature was 110 ° C., and the same evaluation as in Example 1 was performed. Table 1 shows the evaluation results.

[0020]

[0021]

INDUSTRIAL APPLICABILITY The optical sheet of the present invention has excellent optical characteristics and maintains the optical characteristics even under severe operating environments such as high temperature and high humidity, and is lighter and more flexible than a glass substrate. Because it is excellent and has excellent productivity,
It can be applied to a wider range of applications than conventional optical sheets and optical substrates made of resin or glass.

Claims (1)

[Claims] 1. An optical sheet comprising a sheet made of a thermoplastic norbornene-based resin and having a concavo-convex shape provided by pressing a die having irregularities on the surface of the sheet.