TWI442118B - An optical sheet, an optical sheet manufacturing method, a molded article, and a method of manufacturing the same - Google Patents

Description

Optical sheet, method for producing optical sheet, molded body and method for producing the same

The present invention relates to an optical sheet and a method for producing an optical sheet used in a light guide plate and the like, and a molded body in which irregularities are formed on the surface of the optical sheet, and a method of producing the molded body. Further, in detail, an optical sheet excellent in transparency and light guiding property obtained by controlling a high-order structure in a solid structure in which a specific thermoplastic resin is extruded under specific conditions to produce a sheet, and the optical sheet are used. A manufacturing method, a molded body, and a method of producing a molded body.

In recent years, with the spread of mobile electronic devices such as mobile phones, mobile music players, and notebook computers, the thinning of these products and the enlargement of the screen have been achieved. At the same time as the development of the thinning technology of the LED light source, the backlight for the liquid crystal display mounted thereon and the like are thinned. The screen is enlarged to conduct a positive review. In the members constituting the backlight, since the light guide plate dominates the size of the product, attention has been paid to the thinning of the light guide plate and the enlargement of the screen.

Specifically, those having a thickness of 0.8 mm have been thinned to 0.6 to 0.4 mm, and more recently, they have progressed to 0.2 mm or less and further thinned toward 0.2 mm. These thinnings have led to an increase in the thickness of the LED light source. On the other hand, although the screen size is about 1.8 to 2.8 inches, it has recently expanded to 3 to 3.5 inches. Furthermore, regarding the development of notebook computers from CCFL sources to LED light sources, attempts have also been made to use light guides with thicknesses of 0.4 to 0.6 mm for 12-inch screen sizes.

The light guide plate used in the backlight for mobile devices is mainly made of polycarbonate resin. In these cases, the polycarbonate resin is molded into a plate shape by the injection molding method, and fine irregularities of an optical design for the purpose of uniformly emitting the backlight are formed on the surface.

In the polycarbonate resin used herein, in particular, a resin composition which is improved in light guiding properties for use in a light guide plate for injection molding is used (Patent Documents 1 and 2). However, in the injection molding method, the resin composition is not only limited in thickness and screen size, but also birefringent (delayed) due to shear alignment during injection molding, and color aberration tends to occur when illuminating. The problem of moving.

Further, in the resin composition, for example, the injection molding method is replaced by an extrusion molding method, and sheet molding is performed, and the sheet is white turbid during extrusion molding. In particular, when the thickness exceeds 2 mm, white turbidity is remarkable, and brightness characteristics are lowered. Problems. It is difficult to obtain a raw material sheet for a light guide plate from the resin composition by an extrusion molding method.

On the other hand, even if the fluidity at the time of injection molding of the resin composition is improved (Patent Document 3), it is extremely difficult to obtain a light guide plate having a thickness of 2.6 inches or more and a thickness of 0.25 mm or less by the injection molding method. The product of the brightness performance of the light guide plate.

In addition, in the case of a large screen for a notebook computer, a light guide plate made of a conventional polymethyl methacrylate (PMMA) is used, but as the thickness is reduced, there is warpage due to insufficient impact strength (size stability). Insufficient) and cloud (moir ) streaks or problems such as a decrease in brightness due to shifting of the position of the light source.

Due to such a background, although polyethylene terephthalate (PET) sheets are also tried in these thin light guide plates, the birefringence (delay) of the PET sheets is extremely large, and when it is used as a light guide plate. It also produces the disadvantage of chromatic aberration.

In addition, a polycarbonate resin composition of a light guide plate tool containing 0.02 to 2 parts by weight of a phosphorus-based and/or phenolic antioxidant added to 100 parts by weight of a polycarbonate resin is disclosed (Patent Document 4), but In the blue dye, since the forming temperature is high, the total light transmittance is finally 90%, and further improvement is desired.

Patent Document 1: Japanese Patent Publication No. 10-73725 (No. 3330498)

Patent Document 2: JP-A-2002-60609 (No. 3516908) Bulletin

Patent Document 3: JP-A-2005-247947

Patent Document 4: JP-A-2008-24911

An object of the present invention is to provide an optical sheet which can be easily processed into a molded article such as a light guide plate which is thin and large in size, and which has a high light transmittance, and a method for producing the same.

The present inventors have repeated active research to achieve the above object, and have found that the above problems can be attained by molding at a specific temperature using an aromatic polycarbonate having a specific molecular weight and an antioxidant. The present invention has been completed based on this finding.

That is, the present invention provides the following:

(1) An optical sheet comprising (A) 100 parts by mass of an aromatic polycarbonate having a viscosity average molecular weight of 22,000 or less, and (B) an antioxidant having 0.01% by mass or less of a fragrance containing no blue pigment or pigment The family polycarbonate resin composition is extruded from an extruder and then cooled to an optical sheet having a glass transition temperature or lower, wherein the optical sheet has a total light transmittance of 91% or more at a thickness of 0.1 to 1 mm.

(2) The optical sheet according to (1) above, wherein birefringence (phase difference; retardation value at a wavelength of 550 nm) is 150 nm or less, and a standard deviation value of a retardation value at any position in the sheet surface is 10 or less.

(3) The optical sheet according to the above (1), wherein the sample sheet prepared from the aromatic polycarbonate resin composition used in the optical sheet is in a visible light-UV spectroscopic spectrum measured by a thickness of 0.4 mm. The spectral light transmittance at a wavelength of 300 nm is 70% or more, or the spectral transmittance of the aromatic polycarbonate dissolved in a good solvent (measured by the solution method: the light guide length of the solution measuring box is 5 cm, and the sample solution concentration is 12 g) /dl, the solvent is dichloromethane, the wavelength is 450 nm) is 94% or more.

(4) The optical sheet according to the above (1), wherein the (C) thermoplastic polyacrylic resin is contained in an amount of 0.01 to 1 part by mass based on 100 parts by mass of the component (A).

(5) The optical sheet according to the above (1), wherein the antioxidant of the component (B) is a phosphorus-based oxidizing agent and/or a phenol-based antioxidant.

(6) The method for producing an optical sheet according to the above (1), characterized in that the melt-extruded sheet is formed by a molding step of melt-extruding the aromatic polycarbonate resin composition in a sheet form. The cooling step of rapidly cooling the body to a temperature below the glass transition temperature, and the heat treatment step of heat-treating the sheet-like shaped body to be cooled at 50 ° C or higher and the glass transition temperature of the aromatic polycarbonate resin composition.

(7) A molded article characterized in that an uneven pattern is formed on the surface of the optical sheet of the above (1).

(8) The molded article according to (7) above, which is any one of a light guide plate, a diffusion sheet, a reversible reflection plate, a bismuth sheet, and a Freire lens sheet.

(9) A method of producing a molded article, characterized in that the surface of the optical sheet according to (1) above is formed into a concave-convex pattern.

According to the present invention, it is possible to provide a molded article such as a light guide plate which is suitable for producing a thickness and an area which is impossible to achieve by an injection molding method, and has optical properties such as transferability, high transparency, and low birefringence (light guiding property, Color tone) Excellent optical sheet, light guide plate, etc.

The optical sheet of the present invention is obtained by extruding an aromatic polycarbonate resin composition containing no (blue) coloring agent or pigment containing (B) an antioxidant in an aromatic polycarbonate having a viscosity average molecular weight of 22,000 or less. After extrusion, the film is cooled to an optical sheet having a glass transition temperature or lower, and the total light transmittance of the optical sheet at a thickness of 0.1 to 1 mm is 91% or more.

Preferably, the birefringence (phase difference; retardation value at a wavelength of 550 nm) is 150 nm or less, and the standard deviation value of the retardation value measured at any position in the sheet surface is 10 or less.

Since the optical sheet of the present invention does not contain a blue dye or a pigment, when processed into a light guide plate or the like, the luminance characteristics are not lowered. Incidentally, when a blue coloring matter or a pigment is contained, the amount of addition is also a level which reduces the number of brightness by 10%.

In addition, since the (A) aromatic polycarbonate is an optical sheet composed of an aromatic polycarbonate resin composition containing (B) an antioxidant as a base resin, it is possible to reduce yellowing when processing into a sheet. And to reduce the brightness of the sheet when it is processed into a light guide plate.

The aromatic polycarbonate of the component (A) is preferably a bisphenol A type polycarbonate from the viewpoint of optical transparency, mechanical strength, and heat resistance.

Aromatic polycarbonates can generally be produced by reacting a divalent phenol with a polycarbonate precursor of a carbonium chloride or carbonate compound. For example, in a solvent such as dichloromethane, in the presence of a conventional acid acceptor or a molecular weight regulator, and further adding a branching agent as needed, by reacting a divalent phenol with a carbonate precursor such as carbonium chloride, or It is produced by transesterifying a divalent phenol with a carbonate precursor such as diphenyl carbonate.

As the divalent phenol, various divalent phenols can be used, and especially 2,2-bis(4-hydroxyphenyl)propane [general name: bisphenol A] is suitable. Bisphenol other than bisphenol A, for example, bis(4-hydroxyphenyl)methane; 1,1-bis(4-hydroxyphenyl)ethane; 2,2-bis(4-hydroxyphenyl)butane 2,2-bis(4-hydroxyphenyl)octane; 2,2-bis(4-hydroxyphenyl)phenylmethane; 2,2-bis(4-hydroxy-1-methylphenyl)propane Bis(4-hydroxyphenyl)naphthylmethane; 1,1-bis(4-hydroxy-t-butylphenyl)propane; 2,2-bis(4-hydroxy-3-bromophenyl)propane; 2,2-bis(4-hydroxy-3,5-tetramethylphenyl)propane; 2,2-bis(4-hydroxy-3-chlorophenyl)propane; 2,2-bis(4-hydroxy- 3,5-tetrachlorophenyl)propane; bis(hydroxyaryl)alkanes such as 2,2-bis(4-hydroxy-3,5-tetrabromophenyl)propane; 1,1-bis(4- Hydroxyphenyl)cyclopentane; 1,1-bis(4-hydroxyphenyl)cyclohexane; 1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane, etc. a bis(hydroxyaryl)cycloalkane; a 4,4'-dihydroxyphenyl ether; a dihydroxy aryl ether such as 4,4'-dihydroxy-3,3'-dimethylphenyl ether; 4,4'-dihydroxydiphenyl sulfide; dihydroxydiaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; 4,4'- Dihydroxydiphenylarylene; 4,4'-dihydroxy-3,3'-dimethyldi Dihydroxydiaryl fluorenes such as phenyl arsine; 4,4'-dihydroxydiphenyl fluorene; 4,4'-dihydroxy-3,3'-dimethyldiphenyl hydrazine Hydroxydiaryl fluorenes; dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl. These divalent phenols may be used singly or in combination of two or more.

Further, examples of the carbonate compound include a diaryl carbonate such as diphenyl carbonate, a dialkyl carbonate or the like, and a dialkyl carbonate such as diethyl carbonate. Therefore, as the molecular weight modifier, any one can be used as long as it is usually used for polycarbonate synthesis. Specifically, as the monovalent phenol, for example, phenol, o-n-butyl phenol, m-n-butyl phenol, p-n-butyl phenol, o-isobutyl phenol, m-isobutyl phenol, -isobutyl phenol, o-tert-butyl phenol, m-tert-butyl phenol, p-tert-butyl phenol, o-n-pentyl phenol, m-n-pentyl phenol, p-n-pentyl phenol , o-n-hexyl phenol, m-n-hexyl phenol, p-n-hexyl phenol, p-t-octyl phenol, o-cyclohexyl phenol, m-cyclohexyl phenol, p-cyclohexyl phenol, o-phenyl phenol , m-phenylphenol, p-phenylphenol, o-n-nonylphenol, m-n-nonylphenol, p-n-nonylphenol, o-cumylphenol, m-cumylphenol, p-cumyl Phenol, o-naphthylphenol, m-naphthylphenol, p-naphthylphenol; 2,5-di-t-butylphenol; 2,4-di-t-butylphenol; 3,5-di- Third butyl phenol; 2,5-dicumylphenol; 3,5-dicumylphenol; p-cresol, bromophenol, tribromophenol, and the like. Among these monovalent phenols, p-t-butylphenol, p-cumylphenol, p-t-octylphenol, phenol, and the like are preferably used.

Further, as a branching agent, for example, 1,1,1-tris(4-hydroxyphenyl)ethane; α,α',α"-tris(4-hydroxyphenyl)-1,3,5-three can be used. Isopropylbenzene; 1-[α-methyl-α-(4'-hydroxyphenyl)ethyl]-4-[α,,α'-bis(4"-hydroxyphenyl)ethyl]benzene; A compound having three or more functional groups such as fluoroglycolic acid, trimellitic acid, indandione bis(o-cresol).

The viscosity average molecular weight of the aromatic polycarbonate of the component (A) used in the present invention is preferably 22,000 or less, preferably 12,000 to 20,000. If it is less than 12,000, the mechanical strength is deteriorated. If it exceeds 22,000, the total light transmittance is less than 91%, which is less preferable as an optical sheet. The birefringence (phase difference; retardation value at a wavelength of 550 nm) is 150 nm or less, preferably 130 nm or less, and the standard deviation value of the retardation value measured by sampling at any position in the sheet surface is preferably 10 or less. Further, the glass transition temperature of the aromatic polycarbonate of the component (A) is about 141 to 149 °C. After the aromatic polycarbonate is extruded from the extruder, the birefringence is 150 nm or less by cooling to a temperature lower than the glass transition temperature, and the standard deviation value is 10 or less.

The lower the lower limit of the standard deviation value, the better, but from the viewpoints of optical isotropy and economy required for the optical sheet, it is sufficient to practically 15 or so.

In the present invention, any space is sampled by an optical sheet of 100 cm × 100 cm, and each measurement site is placed on a grid of 3 cm × 3 cm at a distance of 1 cm apart from each other at a distance of 60 cm or more. Point the person measured.

As the antioxidant of the component (B), for example, a phosphorus-based, phenol-based or pentaerythritol-based one is used.

Among them, a phosphorus-based antioxidant stabilizer, specifically, a phosphorus-based antioxidant stabilizer such as a phosphite or a phosphate ester is preferably used. As the phosphite, for example, triphenyl phosphite, tridecyl phenyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tridecyl phosphite, three Mercaptophosphite, trioctyl phosphite, tris(octadecyl)phosphite, distearyl pentaerythritol diphosphite, tricyclohexyl phosphite, monobutyl diphenyl phosphite , monooctyl diphenyl phosphite, distearyl pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl) pentaerythritol phosphite, bis(2,6-di- Tributyl-4-methylphenyl)pentaerythritol phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, hydrazine (2,4- a phosphite triester, a diester, a monoester or the like such as di-t-butylphenyl)-4,4-diphenylenephosphonate.

As the phosphate ester, for example, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl) phosphate , 2-ethylphenyl diphenyl phosphate, and the like. These phosphorus-based antioxidants may be used singly or in combination of two or more.

Among these phosphorus-based antioxidants, distearyl pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol phosphite, and bis(2,6-di- Tributyl-4-methylphenyl)pentaerythritol phosphite, tris(2,4-di-t-butylphenyl)phosphite, in the pentaerythritol system, preferably bis(2,6-di- Third butyl-4-methylphenyl)pentaerythritol phosphite. These phosphorus-based antioxidants may be used singly or in combination of two or more.

Phosphorus-based antioxidants can be directly used by commercially available products, such as the Asahi Chemical Industry Co., Ltd. product name: ADEKASTAB 2112, CLIENT Japan Products [SANDOSTAB P-EPQ], Sumitomo Chemical Co., Ltd. [SUMILYZER P-168], steam Bajiaji company's products [tris(2,4-di-t-butylphenyl) phosphite, trade name: IRGANOX 168], Asahi (stock) products [trade name: ADEKASTAB PEP36].

As the phenolic antioxidant, for example, α-tocopherol, butylhydroxytoluene, cinnamyl alcohol, vitamin E, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) Propionate, 2-t-butyl-6-(3'-tert-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenyl acrylate, 2,6- Di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol, diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2,2' -methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-Asia Methyl bis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-dimethylenebis ( 6-α-methyl-benzyl-p-cresol), 2,2'-ethylenebis(4,6-di-t-butylphenol), 2,2'-butylene-bis (4 -methyl-6-tert-butylphenol), 4,4'-butylene bis(3-methyl-6-tert-butylphenol), triethylene glycol-N-bis-3-(3- Third butyl-4-hydroxy-5-methylphenyl)propionate, 1,6-hexanediol bis[3-(3,5-di-t-butyl-4-hydroxyphenyl) Propionate], bis[2-tert-butyl-4-methyl 6-(3-tert-butyl-5-methyl-2-hydroxybenzyl)phenyl]p-phenylene Acid ester, 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propenyloxy]-1,1-dimethylethyl}- 2,4,8,10-tetraoxaspiro[5,5]undecane, 4,4'-thiobis(6-tert-butyl-m-cresol), 4,4'-thio Bis(3-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3,5-di-third) 4--4-hydroxybenzyl) sulfide; 4,4'-di-thiobis(2,6-di-t-butylphenol), 4,4'-tri-thio-bis (2,6- Di-t-butylphenol), 2,2-thiodiethylidene-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4 - bis(n-octylthio)-6-(4-hydroxy-3',5'-di-t-butylanilino)-1,3,5-triazine, N,N'-hexamethylene Bis-(3,5-di-t-butyl-4-hydroxyhydrocinnamate), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl) Propionyl]bipyridine, 1,1,3-tris(2-ethyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4, 6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris(3,5-di-t-butyl-4-hydroxyphenyl)isocyanurate, tri 3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(3,5-di-third -4-hydroxybenzyl)isocyanurate, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, 1, 3,5-tris[[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxy]ethylisocyanurate, and 肆[3-(3,5- Di-t-butyl-4-hydroxyphenyl)propanoxymethyl]methane or the like. These are readily available. Among them, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 1,3,5-trimethyl-2,4 are preferred. 6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyano Urea, 肆[3-(3,5-di-t-butyl-4-hydroxyphenyl)propoxymethyl]methane, preferably n-octadecyl-3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate. These hindered phenol-based antioxidants may be used singly or in combination of two or more.

For the phenolic antioxidant, a commercially available product can be used as it is, for example, a product of Asahi Kasei Kogyo Co., Ltd. [trade name: ADEKASTAB AO-80], a product of Asahi Kasei Kogyo Co., Ltd. [trade name: ADEKASTAB AO-30], a chemical for steam batter ( Products) [product name: IRGANOX 1010, IRGANOX 1076] and so on.

(B) The antioxidant of the component may be one or more kinds of the above-mentioned phosphorus-based antioxidants, or one or more kinds of phenolic antioxidants may be used, or one or more kinds of phosphorus-based antioxidants and one or more kinds of phenol-based antioxidants may be used in combination. .

The amount thereof is in the range of 0.01 to 1 part by mass, preferably 0.05 to 0.3 part by mass, per 100 parts by mass of the aromatic polycarbonate of the component (A). By being such a range, preferable characteristics as an optical sheet can be obtained.

The optical sheet of the present invention has a total light transmittance of 91% or more at a thickness of 0.1 to 1 mm, and after being extruded from an extruder, the total light transmittance is 91 by cooling to the glass transition temperature or lower. %the above. It is preferably 91.5 to 92%.

By making the total light transmittance 91% or more, it is possible to prevent the brightness from decreasing. More than 92% of them have difficulty in industrial production due to the absorption of the molecular skeleton derived from aromatic polycarbonate.

In general, the molecular alignment caused by the shearing force of the injection molded product during injection molding is directly cooled in the mold, and the residual stress is increased due to the molecular alignment being frozen, and the residual stress is near the entrance of the mold and the opposite inlet end. It becomes uneven. In general, since the residual stress deformation at the peripheral portion of the inlet is large, the retardation value tends to show a larger measured value.

On the other hand, the conditions of the sheet produced by extrusion molding, the material viscosity (depending on the viscosity average molecular weight) may lower the retardation value, and may easily cause the distribution of retardation values in the sheet product. Uniformity. Therefore, it is possible to obtain a light guide plate which exhibits a higher quality than a light guide plate obtained by injection molding. By setting the retardation value to 150 nm or less and the standard deviation value of the retardation value measured by sampling at any position in the sheet surface to be 10 or less, it is possible to prevent the backlight of the light guide plate processed by using the optical sheet from being mounted on the liquid crystal panel. The display quality is lowered when the device is displayed. The retardation value is preferably 100 nm or less, more preferably 50 nm or less.

The optical sheet of the present invention is preferably used in a visible light-UV spectroscopic spectrum measured by a thickness of 0.4 mm, and the spectroscopic light transmittance at a wavelength of 300 nm is 70% or more, or the aromatic polycarbonate is dissolved in a good solvent. Spectral light transmittance (determined by solution method: light guide length of solution measuring box: 5 cm, sample solution concentration: 12 g/dl, solvent dichloromethane, wavelength: 450 nm), 94% or more of aromatic polycarbonate resin as polycarbonate resin (A) component of the composition.

In general, in a light guide plate formed by using an optical sheet, light having a wavelength of 400 to 700 nm incident on a visible light region from an end surface is guided and propagated in the end surface direction, and surface light is emitted by controlling the light directivity in the thickness direction (surface direction). The light incident on the end face direction is emitted from the opposite end surface, and the light splitting property of the light guide plate can be evaluated by measuring the light splitting characteristics of the light.

However, in these measurements, it is necessary to prepare a special measuring device for the measurement of a thin molded piece of 1 mm or less, which is actually difficult. Therefore, in the measurement evaluation of the present invention, the characteristics of the sheet are easily evaluated by the spectral characteristics in the thickness direction (surface direction). When the thickness of the sheet is as thin as 1 mm or less, the measurement of the transmittance of the spectroscopic light that transmits visible light in the thickness direction makes it difficult to detect the difference in the spectral characteristics inherent to the sheet substrate. However, even if the spectral characteristics in the thickness direction are measured, it is possible to evaluate the difference in spectral characteristics by focusing on the wavelength of 380 nm or less in the ultraviolet light region. That is, the measurement results of the spectral transmittance of 300 to 380 nm do not directly reflect the spectral transmittance of the visible light region, but relatively reflect the visible light wavelength in the direction of the end face in conjunction with the spectral transmittance of 300 to 380 nm. The tendency of the spectral characteristics of the region can be substituted.

Specifically, the optical resin substrate having a high spectral transmittance of 300 to 380 nm measured in the thickness direction tends to have a high spectral characteristic in the visible light wavelength region when measured in the end surface direction. When the spectral light transmittance is less than 70%, the brightness is lowered because the light guiding performance is insufficient. Better than 73%.

In the optical sheet of the present invention, the (A) aromatic polycarbonate has a viscosity average molecular weight of 22,000 or less, preferably 14,000 to 20,000. Better for 15000~19000. If it is less than 14,000, the strength of the product is insufficient, and the yield due to the adhesion of the cut powder during the processing of the product is also reduced. In particular, when the thickness of the optical sheet is 0.3 mm or less, the strength tends to be insufficient and it is liable to be broken.

When the viscosity average molecular weight exceeds 22,000, it depends on the extrusion molding conditions, but the yellowing or retardation value of the resin substrate tends to become large, and the total light transmittance is difficult to reach 91%.

Further, the resin sheet such as a light guide plate can be formed by transferring a fine concavo-convex pattern (a prismatic shape or a point-shaped convex shape) of several micrometers to several hundreds micrometers on the surface of the sheet by roll embossing or press molding. It is produced by a concave-convex pattern, but if the viscosity average molecular weight exceeds 22,000, the transfer property at this time also decreases.

The optical sheet of the present invention is produced by extrusion molding an aromatic polycarbonate resin composition, but may be added with a small amount of thermoplasticity in addition to the aromatic polycarbonate of the component (A) and the antioxidant of the component (B). A polyalkyl acrylate resin is used as the component (C). The addition of (C) component in a trace can further improve the spectral characteristics.

The component (C) is preferably added in such a manner that the ratio of the component (A)/(C) is from 99.99/0.01 to 99.00/1.00 (mass ratio). More preferably, it is 99.95/0.05~99.50/0.50, preferably 99.90/0.10~99.70/0.30. By setting the addition ratio of the component (C) to 0.01 or more, the transparency of the molded article can be improved, and by setting it to 1.00 or less, the transparency can be maintained without impairing other desired physical properties.

The thermoplastic polyalkyl acrylate resin of the component (C) may be at least one polymer, homopolymer or a repeating unit selected from monomer units of acrylic acid, acrylate, acrylonitrile and derivatives thereof. Copolymer with styrene, butadiene, and the like. Specifically, polyacrylic acid, polymethyl methacrylate (PMMA), polyacrylonitrile, ethyl acrylate-ethyl chloroacetate copolymer, n-butyl acrylate-acrylonitrile copolymer, acrylonitrile can be exemplified. a styrene copolymer, an acrylonitrile-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, or the like. Among these, polymethyl methacrylate (PMMA) is particularly preferably used. As the polymethyl methacrylate (PMMA), a known one can be used, but it is usually preferred to produce a methyl methacrylate monomer by bulk polymerization in the presence of a peroxide or an azo polymerization initiator. .

The (C) component of the thermoplastic polyalkyl acrylate resin preferably has a molecular weight of 200 to 100,000, more preferably 20,000 to 60,000. By setting the molecular weight to 200 to 100,000, the phase separation between the component (A) and the component (C) is not excessively accelerated during molding, and an optical sheet having sufficient transparency can be obtained.

The method for producing the optical sheet of the present invention is not particularly limited, but a desired optical sheet can be produced in accordance with the method for producing an optical sheet of the present invention described below.

The method for producing an optical sheet of the present invention comprises a step of melt-extruding the aromatic polycarbonate resin composition into a sheet form, and cooling the melt-extruded sheet-like formed body to a cooling step of a glass transition temperature or lower And a heat treatment step of heat-treating the cooled sheet-like molded body at 50 ° C or higher and a glass transition temperature of the polycarbonate resin or less.

In the cooling step, the sheet-like formed body can be cooled by passing the slit of the cooling water through the sheet-like formed body. Further, the heat treatment step can be carried out by sandwiching the front and back surfaces of the sheet-like molded body with a mirror-shaped metal ring-shaped belt and/or a metal roll.

As for the extrusion molding method, a sheet forming machine having a three-roll type which is generally used in general can also manufacture an optical sheet which can be utilized as a light guide plate by selecting molding conditions. The cylinder temperature and the mold temperature of the extruder may vary depending on the composition of the resin, the glass transition temperature, etc., but may be 220 to 340 ° C, preferably about 240 to 320 ° C.

When the ratio of the (A) component/(C) component is 99.99/0.01 to 99.00/1.00 (mass ratio) and the resin composition containing the antioxidant (B) in the above ratio is used as a raw material for extrusion molding, the above melting is performed. The cooling step of rapidly cooling the sheet-like formed body obtained by extrusion to a glass transition temperature or less is important, and an optical sheet having higher optical transparency can be obtained by using an extrusion molding apparatus having such a cooling step.

The cooling temperature needs to be equal to or lower than the glass transition temperature, preferably 140 ° C or lower, and more preferably 120 ° C or lower. By setting the cooling temperature to be lower than the glass transition temperature, the total light transmittance of the optical sheet at a thickness of 0.1 to 1 mm can be made 91% or more. The lower limit of the cooling temperature varies depending on the difference in resin composition, the glass transition temperature, and the like, but may be about 50 °C. When it is 50 ° C or more, it is possible to ensure optical isotropy in which the deformation of the formed optical sheet is small. Cooling is usually carried out using a plurality of rolls.

The cylinder temperature of the extruder is 220 to 340 ° C, preferably about 240 to 320 ° C.

Further, in the cooled sheet-like molded body, the heat treatment step of heat treatment at 50 ° C or higher and the glass transition temperature of the aromatic polycarbonate is performed, and the residual deformation caused by the rapid cooling process can be formed by the shape change. An optical sheet having a low hysteresis value of a uniform thickness without wrinkles is obtained.

By using an extrusion molding machine having such a manufacturing step, it is possible to suppress the resin composition having a ratio of (A) component/(C) component of 99.99/0.01 to 99.00/1.00 (mass ratio) from being cooled in a molten state. The resulting phase separation suppresses a decrease in light transmittance.

The manufacturing method including these steps includes, for example, an elastic roll method or a steel strip method, and it is more preferable to use an extrusion molding machine having the above.

As for the steel strip method, for example, a manufacturing method disclosed in Japanese Laid-Open Patent Publication No. 2004-230598 is exemplified.

In the manufacturing method, the formed sheet is adhered to the endless belt which is wound into a plurality of rolls and heated by the heating roll portion, and then the sheet is planarized between the endless belt and the roll or After the linear crimping, the sheet is peeled off from the ring-shaped belt to obtain a sheet, and the heated sheet is kept warm and/or heated from the opposite side of the sheet from the ring belt (refer to FIG. 1). . The heat preservation and/or heating is performed by a heat insulating plate, blowing hot air, and infrared rays.

In Fig. 1, 1 is a tension roller, 2 is a heating roller, 3 is a cooling roller, 4 is a rolling roller, 5 is a ring belt, 6 is a sheet supply roller, 7 is a tension roller, and 8 is a heating device. S is a sheet before the transfer of the uneven shape, and d is a sheet length which is pressed between the pressure roller 4 and the endless belt 5.

As for the elastic roll method, for example, the method disclosed in Japanese Laid-Open Patent Publication No. 2004-155101 is exemplified.

The manufacturing method is such that a T-die is mounted on an extruder to form a sheet, and the sheet is passed through a first rolling roll, a second rolling roll, and a third rolling roll, and the sheet is produced by linearly moving the plurality of transfer rolls in parallel, and The manufacturing method by the take-up roll (refer to FIG. 2).

In Fig. 2, 21 is an extruder, 22, 23, and 25 are rolling rolls, 24 is a take-up roll, and 26a, 26b, and 26c are transfer rolls.

Next, a molded article of the present invention such as a light guide plate having a concave-convex pattern formed on the surface of the optical sheet will be described.

The optical sheet obtained by the above characteristics, composition, and manufacturing method can be used as a light guide plate, a diffusion sheet, and a reversing type reflector by forming a fine concavo-convex pattern on the surface thereof as a molded body. , enamel sheets and Freire lenses. As the concavo-convex pattern, for example, a dot shape, a convex lens shape, a concave lens shape, a V-groove shape, a polygonal pyramid or a quadrangular pyramid, or the like can be used.

Regarding the light guide plate, it is preferable that a gradient (shade) is attached to the uneven pattern.

In the case of a usual diffusion sheet, a reversing reflection sheet, and a sheet, it is preferable to form a uniform pattern.

Moreover, in the case of a diffusion sheet used in a direct type backlight panel, the brightness of the concavo-convex pattern is formed between the distance from the light source on the light source to the distance between the light sources, and uniformity of brightness can be achieved.

As a method of forming such a concavo-convex pattern, a roll embossing method, a vacuum press molding method, a belt transfer method, and the like are exemplified. Among them, it is preferable to use a mold having a fine concavo-convex pattern formed on a nickel-plated foil on the surface of a strip-shaped thin stainless steel, and to continuously heat the resin film while rotating the resin film, and to perform pressure transfer and peeling steps. A belt transfer method of a device of the mechanism (for example, JP-A-2005-321681). This method can transfer large areas with high productivity because it does not require vacuuming, temperature rise, and temperature reduction (see Figure 3).

In Fig. 3, 31 is a heating roller, 32 is a transfer roller for forming irregularities, 33 is a preheating roller, 34 is a cooling roller, 35 is a conveying roller, and 36 is a ring belt. The left arrow is an optical sheet before the transfer of the uneven shape, and the right arrow is the transferred optical sheet, that is, a molded body such as a light guide plate.

Others, a lithographic etching method in which an acrylic ultraviolet curable resin is pressed against an optical sheet of the present invention by ultraviolet rays using a mold having a fine concavo-convex pattern, or a screen printing method using white ink can be used.

A molded body such as a light guide plate can be manufactured by simultaneously performing the steps of forming the optical sheet and forming a concave-convex pattern on the surface. For the manufacturing apparatus having such simultaneous steps, for example, a continuous extrusion embossing machine SPU-03026W manufactured by Toshiba Machine Co., Ltd. (refer to FIG. 4) can be preferably used.

With the apparatus shown in Fig. 4, the transfer length can be increased by lengthening the pressing length by the flexibility of the specific contact roller. Moreover, the measurement and control of the gap and the pressing force are made possible by the roll gap adjusting method (pressure sensor and positioning sensor).

Example

Next, the present invention will be described in more detail by way of examples and comparative examples, but the invention is not limited thereto.

The formulation materials used in the examples and comparative examples are as follows.

<Materials> (1) Aromatic polycarbonate PC1

TAFLON FN1700A [bisphenol A polycarbonate resin manufactured by Idemitsu Kosan Co., Ltd., glass transition temperature: 142 ° C, viscosity average molecular weight: 17,300, refractive index: 1.585]

(2) Aromatic polycarbonate PC2

TAFLON FN1900A [bisphenol A polycarbonate resin manufactured by Idemitsu Kosan Co., Ltd., glass transition temperature: 145 ° C, viscosity average molecular weight: 19,500, refractive index: 1.585]

(3) Aromatic polycarbonate PC3

TAFLON FN2500A [bisphenol A polycarbonate resin manufactured by Idemitsu Kosan Co., Ltd., glass transition temperature: 148 ° C, viscosity average molecular weight: 23,500, refractive index: 1.585]

(4) Phosphorus antioxidants

ADEGASTAB PEP36 [Shuang (2,6-di-t-butyl-4-methylphenyl) pentaerythritol phosphate manufactured by Asahi Kasei Co., Ltd.]

(5) Phenolic antioxidants

IRUGANOX 1076 [Vapor-based antioxidants made of steam batter chemicals, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], in the table 1, is described as "IRG1076".

(6) Thermoplastic polyacrylic resin

DAIANOL BR83 [Mitsubishi 嫘萦 (stock), molecular weight: 25,000, refractive index 1.490, molecular weight is determined by the Ostward type viscosity tube at 25 ° C chloroform solution ultimate viscosity [η], the average degree of polymerization PA is obtained from the following equation And the calculation. logPA=1.613log([η]×10 ⁴ /8.29)].

Table 1 describes "acrylic resin".

(7) Blue dye

HOSTALUX KSN [CLIANT made in Japan, 4-(benzoxazol-2-yl)-4,-(5-methylbenzoxazol-2-yl)stilbene (Stilbenes) and blue pigment Mixture]

<mixed extrusion>

Each material was mixed with a blending machine in the proportions of the respective examples and comparative examples shown in Table 1, and melt-kneaded and extruded at 280 ° C using a single-axis extruder having a screw diameter of 65 mm, and was produced in each case. The particles used.

<Optical Sheet Extrusion> Condition 1 (applicable in Examples 1 to 4 and Comparative Examples 1 and 2)

An optical sheet (thickness: 0.4 mm) was produced by a "three-roller apparatus" provided with an extruder 21 shown in Fig. 2. The first press roll 22 having a screw diameter of 65 mm and an T-die width of 650 mm and a diameter of 300 mm was used. The second pressure roller 23 and the third pressure roller 25 each use a metal roller having a diameter of 300 mm. The transfer roller 26 is a metal roller having three diameters of 70 mm in parallel in a straight line. Moreover, the total distance from the initial transfer roller 26a to the final transfer roller 26c was set to 3 m.

Condition 2 (applicable in Example 5)

This was carried out using a UF roll squeezing extruder (elastic roll method - see Fig. 2) manufactured by Hitz Machine Technology Co., Ltd. The screw diameter of the extruder was 90 mm.

Condition 3 (applicable in Example 6)

Using a continuous extrusion embossing machine SPU-03026W (refer to FIG. 4) manufactured by Toshiba Machine Co., Ltd., the sheet obtained by sheet formation was pressed against a triangular pyramidal array (height 50 μm) by a nickel-plated stamper. Pattern transfer was performed, thereby producing a prismatic sheet (pattern formation 2). The screw diameter of the extruder was 26 mm ψ, and the temperatures of the other parts were as shown in Table 1.

Condition 4 (applicable in Comparative Example 3)

Except that the temperature of each part was changed to the temperature shown in Table 1, the other conditions were the same as Condition 1.

Condition 5 (applicable in Comparative Example 4)

Injection molding was carried out using an injection molding machine having a mold clamping force of 100 tons [Sumitomo Heavy Industries Co., Ltd., product SG100M-HP] at a molding temperature of 360 ° C (mold temperature: 120 ° C).

<Pattern transfer by press molding>

Each of the optical sheets produced in each of the examples and the comparative examples except for Example 6 was vacuum-sucked by a vacuum presser for fine pattern transfer manufactured by a famous machine, and pressed against a triangular cone by a stamper formed of nickel plating. A prismatic array (having a height of 50 μm) was subjected to press molding at 160 ° C to fabricate a light guide plate (pattern formation 1).

<Evaluation method> (1) Total light transmittance

The measurement was carried out in accordance with JIS-K-7105 using a turbidity meter (HGM-2DP) manufactured by SUGA Testing Machine Co., Ltd.

(2) Spectral light transmittance of the sheet

The optical sheet sample having a thickness of 0.4 mm was measured for a light transmittance (%) of a wavelength of 300 nm by a UV-visible spectrophotometer (UV-2450) manufactured by Shimadzu Corporation.

(3) Birefringence (delay value) and its standard deviation value

The birefringence (delay value) at 550 nm was measured by a retardation measuring device (RETS-100) manufactured by Otsuka Electronics Co., Ltd.

In the present invention, any space is sampled by an optical sheet of 100 cm × 100 cm, and each measurement site is attached to a grid of 3 cm × 3 cm at a distance of 1 cm apart from each other at a distance of 60 cm or more. The measurement was performed at 18 o'clock.

Calculation formula:

Standard deviation (σ)= n represents the total number of samples measured, Re _n represents the Re value of the nth sample, and Re _av represents the average value of Re.

(4) Optical properties by solution method (spectral light transmittance) a) Sample preparation

The cut sample (6 g) was placed in an Erlenmeyer flask (50 ml) and dissolved by adding dichloromethane, and ultrasonic wave irradiation was performed for 3 hours.

b) Measuring device: Shimadzu Corporation UV-2450

c) Measurement conditions:

Measuring box (cell) length: 5cm

Measuring wavelength: 900~200 microns

Scan speed: set to low speed mode

Slit width: 2.0nm

Conversion wavelength: 360nm

d) Determination sequence

After the apparatus was stood up and stabilized 2 hours before the measurement, the reference line was measured, and then autozero was measured at 500 nm, and it was confirmed by measuring whether it was zero or not.

Wash thoroughly with dichloromethane and acetone. After the temperature of the measuring box becomes room temperature, add the measurement solution at the time when the temperature of the measuring box recovers. Place the measuring box on the lid of the measuring chamber cover and let it stand for about 1 minute. . After the measurement is completed, the measurement solution is taken out and washed, and the sample is changed repeatedly.

(5) Transfer of concave and convex patterns

Each of the light guide plates obtained in Examples 1 to 6 and Comparative Examples 1 to 4 was carried out in place of the brightness evaluation in accordance with the pattern transfer rate reflecting the brightness characteristics.

Transfer rate (%) = [transfer guide plate triangular cone height (micron) / triangular cone height in the stamper (50 microns)] × 100

[Examples 1 to 6]

Each of the pellets produced by melt-kneading extrusion using the blending materials shown in Table 1 was used to produce an optical sheet using the molding conditions of "Condition 1", "Condition 2" or "Condition 3", and the pattern was formed on each of the optical sheets. A light guide plate was formed by forming 1 (Examples 1 to 5) or pattern formation 2 (Example 6). The temperatures in each of the conditions are as shown in Table 1.

[Comparative Examples 1 to 4]

Each of the pellets produced by melt-kneading extrusion using the blending materials shown in Table 1 was used to produce an optical sheet using the molding conditions of "Condition 1", "Condition 4" or "Condition 5", and the pattern was formed on each of the optical sheets. Form 1 to make a light guide plate. The temperatures in each of the conditions are as shown in Table 1.

[Table 1]

Industrial useability

The optical sheet of the present invention can control the high-order structure in the solid structure by extrusion molding the resin composition containing the specific aromatic polycarbonate under specific conditions, and the unevenness formed on the surface by the use corresponding to the use. The pattern is optimized, and can be processed into a light guide plate, a diffusion sheet, a reversing reflection plate, or a thin sheet for improving brightness.

1. . . Tension roller

2. . . Heating roller

3. . . Cooling roller

4. . . Roller

5. . . Ring belt

6. . . Sheet supply roller

7. . . Tension roller

8. . . heating equipment

S. . . Sheet before transfer of concave and convex shape

d. . . Sheet length pressed by the rolling roll and the endless belt

twenty one. . . Extruder

twenty two. . . Roller

twenty three. . . Roller

twenty four. . . Take-up roll

25. . . Roller

26a. . . Transfer roller

26b. . . Transfer roller

26c. . . Transfer roller

31. . . Heating roller

32. . . Transfer roller for forming irregularities

33. . . Preheating roller

34. . . Cooling roller

35. . . Transfer roller

36. . . Ring belt

Fig. 1 is a schematic view showing a transfer step by a steel strip method.

Fig. 2 is a schematic view showing a transfer step by a roll method.

Fig. 3 is a schematic view showing a transfer step by a belt transfer method.

Fig. 4 is a schematic view showing a manufacturing apparatus for performing the steps of simultaneously forming a sheet and forming a concave-convex pattern.

Claims (9)

An optical sheet comprising: (A) 100 parts by mass of an aromatic polycarbonate having a viscosity average molecular weight of 22,000 or less, and (B) an antioxidant having 0.01% by mass or less of an aromatic poly group containing no blue coloring matter or pigment After the carbonate resin composition is extruded by an extruder, it is cooled to an optical sheet having a glass transition temperature or lower, and the total light transmittance of the optical sheet at a thickness of 0.1 to 1 mm is 91% or more. An optical sheet according to claim 1, wherein the birefringence (phase difference; retardation value at a wavelength of 550 nm) is 150 nm or less, and the standard deviation value of the retardation value at any position in the sheet surface is 10 or less. The optical sheet of claim 1, wherein the sample sheet made of the aromatic polycarbonate resin composition used in the optical sheet has a visible light-UV spectroscopic spectrum measured at a thickness of 0.4 mm at a wavelength of 300 nm. The light transmittance of the split light is 70% or more, or the spectral transmittance of the aromatic polycarbonate dissolved in a good solvent (measured by the solution method: the light guide length of the solution measuring box is 5 cm, and the concentration of the sample solution is 12 g/dl, The solvent was dichloromethane (wavelength: 450 nm) and was 94% or more. The optical sheet of the first aspect of the invention, wherein the (C) thermoplastic polyacrylic resin is contained in an amount of 0.01 to 1 part by mass based on 100 parts by mass of the component (A). The optical sheet of claim 1, wherein the antioxidant of the component (B) is a phosphorus-based antioxidant and/or a phenol-based antioxidant. A method for producing an optical sheet according to the first aspect of the invention, characterized in that the melt-extruded sheet-like formed body is rapidly cooled by a step of melt-extruding the aromatic polycarbonate resin composition in a sheet form. The cooling step below the glass transition temperature and the heat treatment step of heat-treating the sheet-shaped molded body to be cooled at 50 ° C or higher and the glass transition temperature of the aromatic polycarbonate resin composition. A molded article characterized in that the surface of the optical sheet of claim 1 is formed into a concave-convex pattern. The molded article of claim 7, which is any one of a light guide plate, a diffusion sheet, a reversible reflection plate, a crucible sheet, and a Freire lens sheet. A method of producing a molded article characterized in that an uneven pattern is formed on the surface of the optical sheet of claim 1 of the patent application.