KR20100138965A - Optical sheet, process for producing optical sheet, formed object, and process for producing formed object - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical sheet having a high light transmittance, a method of manufacturing the same, and a method of manufacturing a molded article and a molded article formed by forming an uneven pattern on the surface of the optical sheet. The aromatic polycarbonate resin composition containing (A) 100 mass parts of aromatic polycarbonates with a viscosity average molecular weight of 22000 or less, and (B) 0.01-1 mass part of antioxidant, and does not contain a blue pigment or a pigment is extruder After extruding from, as an optical sheet cooled below the glass transition temperature, the total light transmittance in the thickness of 0.1-1 mm of this optical sheet is 91% or more, It is achieved by the optical sheet characterized by the above-mentioned.

Description

OPTICAL SHEET, PROCESS FOR PRODUCING OPTICAL SHEET, FORMED OBJECT, AND PROCESS FOR PRODUCING FORMED OBJECT}

TECHNICAL FIELD This invention relates to the manufacturing method of the optical sheet and optical sheet used for a light-guide plate, etc., and the manufacturing method and the manufacturing method of the molded object which formed the uneven | corrugated on the surface of the optical sheet. More specifically, an optical sheet excellent in transparency and light guide obtained by extruding a specific thermoplastic resin under specific conditions to control a higher order structure in the solid structure of the sheet, a method for producing the optical sheet, a molded article, and a molded article It is about a method.

In recent years, with the spread of mobile electronic devices such as mobile phones, portable music players, and notebook computers, thinning and screen enlargement of these product devices have been promoted. With the development of the thinning technology of the LED light source, the backlight for the liquid crystal display mounted here is also actively examined for thinning and screen enlargement. In light of the fact that the light guide plate dominates the product size among the members constituting the backlight, consideration has been given to the thinning of the light guide plate and the enlargement of the screen.

Specifically, the thickness having already been 0.8 mm has been thinned to 0.6 to 0.4 mm, and the thickness has been further advanced to 0.2 mm which is 0.3 mm or less in recent years. These thinnings are due to the thinning of the LED light source. On the other hand, screen sizes of about 1.8 to 2.8 inches are gradually expanding to 3 to 3.5 inches. Furthermore, in light notebooks, the LED light source from a CCFL light source advances, and examination of the light guide plate of 0.4-0.6 mm in thickness is tried also about the screen size of 12-inch class.

The light guide plate used for the backlight for mobile devices is mainly made of polycarbonate resin. These are mainly formed by the injection molding method to form a polycarbonate resin into a plate shape, and at the same time, fine irregularities that are optically designed for the purpose of uniformly emitting a backlight are formed on the surface thereof.

Among the polycarbonate resins used here, in particular, resin compositions in which light guide properties have been improved for light guide plate applications for injection molding have been extensively used (Patent Documents 1 and 2). However, in the injection molding method, these resin compositions are limited by the thickness of the light guide plate and the screen size, and also have a problem that birefringence (retardation) occurs due to the shear orientation during injection molding, and color shifting easily occurs during light emission. have.

In addition, about the resin composition, even if the sheet molding was performed by changing the injection molding method to the extrusion molding method, the sheet became cloudy at the time of extrusion molding, and in particular, when the thickness exceeded 2 mm, the cloudy appearance became remarkable, and the luminance characteristic There was a problem that this is lowered. It was difficult to obtain the original sheet for light guide plates in the resin composition by the extrusion molding method.

On the contrary, even if the fluidity | liquidity at the time of injection molding of the resin composition was improved (patent document 3), in the injection molding method, the light guide plate of 2.6 inches class or more and 0.25 mm or less in thickness is a product which expresses the brightness performance as a light guide plate as a limit region which cannot be molded. It was very difficult to get.

In addition, a light guide plate made of polymethyl methacrylate (PMMA) has conventionally been used for a large screen such as a notebook computer, but according to thinning, not only the impact strength is insufficient, but also the warpage (lack of dimension stability) causes the moire pattern. There existed problems, such as brightness fall by generation | occurrence | production and position shift from a light source.

In view of this background, attempts have been made to apply polyethylene terephthalate (PET) sheets to these thin light guide plates, but PET sheets have extremely high birefringence (retardation), so that color shift is liable to occur when the light guide plate is used. There is this.

Moreover, although the polycarbonate resin composition for light guide plates which mix | blends 0.02-2 weight part of phosphorus type and / or a phenolic antioxidant with respect to 100 weight part of polycarbonate resin is disclosed (patent document 4), it uses a blue dye etc. In addition, since the molding temperature is high, the total light transmittance remains in the 90% range, and further improvement is desired.

Japanese Unexamined Patent Publication No. Hei 10-73725 (Patent 3330498) Japanese Unexamined Patent Publication No. 2002-60609 (Patent 3516908) Japanese Laid-Open Patent Publication 2005-247947 Japanese Laid-Open Patent Publication 2008-24911

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

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, the present inventors discovered that the said subject can be achieved by using the aromatic polycarbonate and antioxidant of a specific molecular weight, and also shape | molding at specific temperature. This invention is completed based on this knowledge.

That is, the present invention,

(1) Aromatic polycarbonate resin composition containing (A) 100 mass parts of aromatic polycarbonates with a viscosity average molecular weight of 22000 or less, and (B) 0.01-1 mass part of antioxidant, and containing no blue pigment or pigment is extruded from an extruder An optical sheet cooled after the glass transition temperature or less, wherein the total light transmittance at a thickness of 0.1 to 1 mm of the optical sheet is 91% or more,

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

(3) In the visible-UV spectral spectrum measured at 0.4 mm of the sample plate thickness prepared with the aromatic polycarbonate resin composition used for the said optical sheet, 70% or more of the spectral light transmittance at wavelength 300nm or an aromatic polycarbonate The spectral light transmittance measured by dissolving in a good solvent (measured by the solution method: light guide length of the solution cell is 5 cm, sample solution concentration 12 g / dl, solvent dichloromethane, wavelength 450 nm) is 94% or more of the above (1) Optical sheet described in

(4) Optical sheet of said (1) containing 0.01-1 mass part of (C) thermoplastic polyacrylic-type resin with respect to 100 mass parts of said (A) component,

(5) The optical sheet according to the above (1), wherein the antioxidant of the component (B) is a phosphorus antioxidant and / or a phenolic antioxidant,

(6) The molding process of melt-extruding the aromatic polycarbonate resin composition into a sheet form, the cooling process of rapidly quenching the melt-extruded sheet form molded body below a glass transition temperature, and the cooled sheet-shaped molded article at 50 ° C or more, wherein the aromatic The manufacturing method of the optical sheet as described in said (1) characterized by the heat processing process of heat-processing below the glass transition temperature of a polycarbonate resin composition,

(7) A molded article formed by forming an uneven pattern on the surface of the optical sheet according to the above (1),

(8) The molded article according to (7), which is any one of a light guide plate, a diffusion sheet, a retroreflective plate, a prism sheet, and a Fresnel lens sheet.

(9) It provides a manufacturing method of the molded object characterized by forming an uneven | corrugated pattern on the surface of the optical sheet as described in said (1).

According to the present invention, an optical sheet, a light guide plate, and the like, which are excellent in optical properties (light guide, color tone) such as transferability, high transparency, low birefringence, and the like, which are suitable for the production of molded articles such as light guide plates having a thickness and area which are impossible in the injection molding method, are provided. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the transfer process by the steel belt method.
It is a figure which shows the transfer process by the pinching roll method.
It is a schematic diagram which shows the transfer process by a belt transfer method.
It is a schematic diagram of the manufacturing apparatus which performs the process of forming a sheet | seat and an uneven | corrugated pattern simultaneously.

To practice the invention  Best form for

The optical sheet of this invention contains (A) antioxidant in (A) aromatic polycarbonate with a viscosity average molecular weight of 22000 or less, and after the aromatic polycarbonate resin composition which does not contain a blue pigment or a pigment is extruded from an extruder, As an optical sheet cooled below glass transition temperature, the total light transmittance in 0.1-1 mm in thickness of this optical sheet is 91% or more.

It is preferable that birefringence (phase difference; retardation value in wavelength 550nm) is 150 nm or less, and the standard deviation value of the retardation value measured at arbitrary points in a sheet surface is 10 or less.

Since the optical sheet of this invention does not contain a blue pigment or a pigment, when processed with a light guide plate etc., there is no fall of a luminance characteristic. In addition, when it contains a blue type pigment | dye or a pigment, although it changes also with the compounding quantity, luminance number falls to the order of 10%.

Moreover, since the (A) aromatic polycarbonate was made into the optical resin which consists of an aromatic polycarbonate-type resin composition containing (B) antioxidant as a base resin, reduction of the yellowing at the time of shaping | molding into a sheet is aimed at, and this sheet Is reduced when processing the light guide plate or the like.

As an aromatic polycarbonate which is (A) component, the bicarbonate phenol type polycarbonate is preferable from a viewpoint of optical transparency, mechanical strength, and heat resistance.

An aromatic polycarbonate can be manufactured by making a polycarbonate precursor, such as a bivalent phenol, phosgene or carbonate ester compound, react normally. For example, in a solvent such as methylene chloride, in the presence of a known acid acceptor or molecular weight modifier, a branching agent is further added, if necessary, and reacted with a divalent phenol and a carbonate precursor such as phosgene, Or a transesterification reaction of a dihydric phenol with a carbonate precursor such as diphenyl carbonate or the like.

Although there exist various kinds of dihydric phenol, 2, 2-bis (4-hydroxyphenyl) propane [common name: bisphenol A] is preferable. As bisphenol other than bisphenol A, it is bis (4-hydroxyphenyl) methane, for example; 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 and 1,1-bis (4-hydroxyphenyl) cyclopentane; 1,1-bis (4-hydroxyphenyl) cyclohexane; Bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) -3,5,5-trimethylcyclohexane and 4,4'-dihydroxyphenyl ether; Dihydroxyaryl ethers such as 4,4'-dihydroxy-3,3'-dimethylphenyl ether and 4,4'-dihydroxydiphenyl sulfide; Dihydroxy diaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide and 4,4'-dihydroxydiphenyl sulfoxide; Dihydroxy diaryl sulfoxides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide and 4,4'-dihydroxydiphenyl sulfone; Dihydroxy diaryl sulfones, such as 4,4'- dihydroxy- 3,3'- dimethyl diphenyl sulfone, dihydroxy diphenyls, such as 4,4'- dihydroxy diphenyl, etc. are mentioned. . These dihydric phenols may be used independently, respectively and may mix and use 2 or more types.

Examples of the carbonate ester compound include diaryl carbonates such as diphenyl carbonate, dialkyl carbonates such as dimethyl carbonate and diethyl carbonate. And as a molecular weight modifier, what is necessary is just what is normally used for superposition | polymerization of polycarbonate, and various things can be used. Specifically, as monohydric phenol, it is phenol, on-butylphenol, mn-butylphenol, pn-butylphenol, o-isobutylphenol, m-isobutylphenol, p-isobutylphenol, ot-butyl, for example. Phenol, mt-butylphenol, pt-butylphenol, on-pentylphenol, mn-pentylphenol, pn-pentylphenol, on-hexylphenol, mn-hexylphenol, pn-hexylphenol, pt-octylphenol, o-cyclo Hexylphenol, m-cyclohexylphenol, p-cyclohexylphenol, o-phenylphenol, m-phenylphenol, p-phenylphenol, on-nonylphenol, m-nonylphenol, pn-nonylphenol, o-cumylphenol, m-cumylphenol, p-cumylphenol, o-naphthylphenol, m-naphthylphenol, p-naphthylphenol; 2,5-di-t-butylphenol; 2,4-di-t-butylphenol; 3,5-di-t-butylphenol; 2,5-dicumylphenol; 3,5-dicumylphenol; p-cresol, bromophenol, tribromophenol, etc. are mentioned. Among these monohydric phenols, p-t-butylphenol, p-cumylphenol, p-t-octylphenol, phenol and the like are preferably used.

In addition, as a branching agent, For example, 1,1,1-tris (4-hydroxyphenyl) ethane; α, α ', α "-tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene; 1- [α-methyl-α- (4'-hydroxyphenyl) ethyl] -4- [Α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene; You may use the compound which has 3 or more functional groups, such as a phloroglycine, trimellitic acid, and isatinbis (o-cresol).

The aromatic polycarbonate which is (A) component used in this invention needs to have a viscosity average molecular weight of 22000 or less, Preferably it is 12,000-20,000. If it is less than 12,000, mechanical strength will fall, and if it exceeds 22,000, the total light transmittance will be less than 91%, which is not preferable as an optical sheet. The birefringence (phase difference; retardation value at wavelength 550 nm) is 150 nm or less, Preferably it is 130 nm or less, and the standard deviation value of the retardation value measured by sampling at arbitrary points in a sheet surface is 10 or less. It is preferable. Moreover, the glass transition temperature of the aromatic polycarbonate which is (A) component is about 141-149 degreeC. After the aromatic polycarbonate is extruded from the extruder, the birefringence is 150 nm or less, and the standard deviation value can be 10 or less by cooling below such a glass transition temperature.

Although the lower limit of a standard deviation value is so preferable that it is low, it is preferable from a viewpoint of the optical isotropy, economical efficiency, etc. which are calculated | required by an optical sheet about 15 practically enough.

In the present invention, an arbitrary point is a 3 cm x 3 cm lattice image of a 1 cm pitch of 4 cm x 4 cm portions of two points at which each measurement point is separated by 60 cm or more from an optical sheet sample of 100 cm x 100 cm. We shall measure 18 points in total in nine points.

As antioxidant (B) component, what is phosphorus type, a phenol type, and pentaerythritol system is mentioned.

Especially, phosphorus antioxidant, More specifically, phosphorus antioxidant stabilizers, such as a phosphite ester and a phosphate ester, are used preferably. As a phosphite ester, a triphenyl phosphite, a trisnonyl phenyl phosphite, a tris (2, 4-di-tert- butylphenyl) phosphite, a trinoyl phosphite, a tridecyl phosphite, a trioctyl phosphate, for example Fight, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tricyclohexyl phosphite, monobutyl diphenyl phosphite, monooctyl diphenyl phosphite, distearyl pentaerythritol diphosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol phosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol phosphite, 2,2-methylenebis (4,6-di- Triester, diester, monoester, etc. of phosphorous acid, such as tert- butylphenyl) octyl phosphite and tetrakis (2, 4-di-tert- butylphenyl) -4, 4- diphenylene phosphonite, etc. are mentioned. have.

Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (nonylphenyl) phosphate and 2-ethylphenyl diphenyl phosphate. These phosphorus antioxidants may be used independently or may be used in combination of 2 or more type.

Among these phosphorus antioxidants, distearyl pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol phosphite and bis (2,6-di-tert-butyl-4-methylphenyl) Pentaerythritol phosphite and tris (2,4-di-tert-butylphenyl) phosphite are preferable, and pentaerythritol type | system | group, especially bis (2,6-di-tert- butyl- 4-methylphenyl) pentaerythrite Ritol phosphite is particularly preferred. The said phosphorus antioxidant can be used individually or in combination of 2 or more types.

Phosphorus antioxidant can use a commercial item as it is, For example, Asahi telephone industry Co., Ltd. product [brand name: Adecastab 2112], the product of Clariant Japan Inc. [Sandstav P-EPQ], the product of Sumitomo Chemical Corporation [Sumi Riser P-168], manufactured by Chiba Co., Ltd. (tris (2,4-di-tert-butylphenyl) phosphite, trade name: Irgafos 168), product of Asahi Telephone Co., Ltd. (trade name: Adega Stave PEP36) ] Etc. can be mentioned.

Phenolic antioxidants include α-tocopherol, butylhydroxytoluene, cinafil alcohol, vitamin E, n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate , 2-tert-butyl-6- (3'-tert-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenylacrylate, 2,6-di-tert-butyl-4- (N , N-dimethylaminomethyl) phenol, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate diethyl ester, 2,2'-methylenebis (4-methyl-6-tert-butylphenol) , 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylenebis (4 -Methyl-6-cyclohexylphenol), 2,2'-dimethylene-bis (6-α-methyl-benzyl-p-cresol), 2,2'-ethylidene-bis (4,6-di-tert -Butylphenol), 2,2'-butylidenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), tree Ethylene glycol-N-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 1,6-hexanediolbis [3- (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionate], bis [2-tert-butyl-4-methyl6- (3-tert-butyl-5-methyl-2-hydroxybenzyl) phenyl] Terephthalate, 3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10 Tetraoxaspiro [5,5] undecane, 4,4'-thiobis (6-tert-butyl-m-cresol), 4,4'-thiobis (3-methyl-6-tert-butylphenol) , 2,2'-thiobis (4-methyl-6-tert-butylphenol), bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 4,4'-dithiobis ( 2,6-di-tert-butylphenol), 4,4'-tri-thiobis (2,6-di-tert-butylphenol), 2,2-thiodiethylenebis- [3- (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis (n-octylthio) -6- (4-hydroxy-3 ', 5'-di-tert-butylanyl Lino) -1,3,5-triazine, N, N'-hexamethylenebis- (3,5-di-tert-butyl-4-hydroxyhydrocinnamid), N, N'-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydr Gin, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di- tert-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-tert-butyl-4-hydroxyphenyl) isocyanurate, tris (3,5-di-tert-butyl-4-hydrate Oxybenzyl) isocyanurate, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-tert-butyl -3-hydroxy-2,6-dimethylbenzyl) isocyanurate, 1,3,5-tris2 [3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl Isocyanurate, tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl] methane, and the like. These are all easy to obtain. Among them, n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5- Di-tert-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, tetrakis [3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl] methane is preferred, in particular n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate is preferred. The said hindered phenol type antioxidant can be used individually or in combination of 2 or more types.

A phenolic antioxidant can use a commercial item as it is, For example, Asahi Telephone Co., Ltd. product [brand name: Adecasta AO-80], the company product [brand name: Adecasta AO-30], Chiba Specialty Chemicals ( Note) Products (brand names: Irganox 1010, Irganox 1076), etc. are mentioned.

The antioxidant which is (B) component may use 1 or more types of said phosphorus antioxidants, 1 or more types of phenolic antioxidants may be used, 1 or more types of phosphorus antioxidants and 1 or more types of phenolic antioxidants may be used. You may use in combination.

The addition amount is the range of 0.01-1 mass part with respect to 100 mass parts of aromatic polycarbonate which is (A) component, Preferably it is the range of 0.05-0.3 mass parts. By setting it as such a range, the preferable characteristic as an optical sheet is obtained.

The optical sheet of this invention is 91% or more in the total light transmittance in 0.1-1 mm in thickness. After extruding from an extruder, total light transmittance can be 91% or more by cooling below said glass transition temperature. Preferably, it is 91.5 to 92%.

By setting it as 91% or more, the luminance is prevented from being lowered. If it exceeds 92%, industrial manufacture is difficult at present because of absorption from molecular skeleton of aromatic polycarbonate.

In general, injection molded articles are cooled in a mold with molecular orientation by shear at the time of injection molding, and the residual stress deformation tends to increase because the molecular orientation is frozen, so that residual stress is near the gate and half-gate ends of the mold. The degree of deformation becomes uneven. Usually, since the residual stress deformation of a gate periphery becomes large, a retardation value tends to show a larger measured value.

On the other hand, although the sheet by extrusion molding differs depending on the conditions at the time of extrusion molding and the viscosity (depending on the viscosity average molecular weight) of the material, the retardation value can be made low, and the distribution of the retardation in the sheet product is uniform. It is easy. For this reason, a light guide plate with a higher display quality than a light guide plate by injection molding can be obtained. By setting the retardation value to 150 nm or less and setting the standard deviation value of the retardation value measured by sampling at an arbitrary point in the sheet surface to 10 or less, the backlight using the light guide plate processed the optical sheet is mounted on the liquid crystal panel for display. The display quality in the case of using a device is prevented from falling. The retardation value is preferably 100 nm or less, more preferably 50 nm or less.

In the visible-UV spectral spectrum measured at a thickness of 0.4 mm, the optical sheet of the present invention has a spectral light transmittance measured by dissolving 70% or more of the spectral light transmittance at a wavelength of 300 nm or an aromatic polycarbonate in a good solvent. Measurement by the method: The light guide length of a solution cell is 5 cm, sample solution concentration 12 g / dl, solvent dichloromethane, wavelength 450 nm), The aromatic polycarbonate resin which becomes 94% or more is used for (A) component of a polycarbonate resin composition. It is preferable to use as.

Usually, in the light guide plate shape | molded using the optical sheet, the light ray of wavelength 400-700 nm of a visible light area | region enters from a cross section, guides and propagates in a cross-sectional direction, and the directionality of light in a thickness direction (plane direction) is carried out. Surface control is performed by controlling. The light suitable for the light propagation of the light guide plate can be evaluated by emitting the light incident in this cross section direction from the opposite end face and measuring the spectral characteristics of the light.

However, in such a measurement, the measurement in the thin molded piece of 1 mm or less needs to prepare a special measuring device, and is difficult in reality. Therefore, in this invention, the characteristic evaluation of the sheet was performed by the spectral characteristic of the thickness direction (surface direction) which measurement evaluation is easy. In general, when the thickness of the sheet becomes thinner than 1 mm, detection of the spectral characteristic inherent in the sheet substrate becomes difficult in the measurement of the spectral light transmittance in which visible light is transmitted in the thickness direction. However, even if the spectral characteristic measurement in the thickness direction is paid attention to the wavelength of 380 nm or less in the ultraviolet region, the spectral characteristic difference can be evaluated. In other words, the evaluation result of the spectral transmittance of 300 to 380 nm by measurement in the thickness direction does not directly reflect the spectral transmittance of the visible range, but the visible light wavelength region in the cross-sectional direction relative to the spectral transmittance of 300 to 380 nm. It tends to reflect the spectral characteristics of, and its substitution is possible.

Specifically, the optical resin base material having the characteristic of having a high spectral transmittance of 300 to 380 nm measured in the thickness direction tends to have high spectral characteristics in the visible light wavelength region when measured in the cross-sectional direction. If the spectral light transmittance is less than 70%, the light guide performance is insufficient, so that the luminance decreases. More preferably, it is 73% or more.

The viscosity average molecular weight of the said (A) aromatic polycarbonate in the optical sheet of this invention is 22000 or less, Preferably it is 14000-20000. More preferably, they are 15000-19000. If it is less than 14000, not only product strength will be insufficient, but the yield will fall by adhesion of the cutting powder at the time of external processing of a product. In particular, in the case where the thickness of the optical sheet is made thinner than 0.3 mm, there is a tendency to cause a lack of strength and to be easily broken.

When the viscosity-average molecular weight exceeds 22,000, depending on the extrusion molding conditions, the yellowing and the retardation value of the resin substrate tend to be large, and the total light transmittance is difficult to reach 91%.

The light guide plate or the like is produced by transferring a resin sheet to the surface of the sheet by roll embossing or press molding to transfer a fine concavo-convex pattern (prism, dot, dome-shaped convex lens) to form a concave-convex pattern. When the viscosity average molecular weight exceeds 22000, the transferability at this time also decreases.

The optical sheet of the present invention is produced by extrusion molding an aromatic polycarbonate resin composition, but in addition to the aromatic polycarbonate as the component (A) and the antioxidant as the component (B), a trace amount of a thermoplastic polyacrylic acid alkyl ester resin is added as the component (C). You may also By adding a trace amount of (C) component, the spectral characteristic improves further.

It is preferable to add (C) component so that the ratio of (A) component / (C) component may be 99.99 / 0.01-99.00 / 1.00 (mass ratio). More preferably, it is 99.95 / 0.05-99.50 / 0.50, Especially preferably, they are 99.90 / 0.10-99.70 / 0.30. The transparency of a molded object improves by setting the addition ratio of (C) component to 0.01 or more, and transparency can be maintained without damaging other desired physical property by setting it as 1.00 or less.

The thermoplastic polyacrylic acid alkyl ester resin as the component (C) is a polymer having at least one member selected from the monomer units of acrylic acid, acrylic acid ester, acrylonitrile and derivatives thereof as a repeating unit, and a homopolymer or styrene, butadiene or the like. A copolymer may be sufficient. Specifically, polyacrylic acid, polymethyl methacrylate (PMMA), polyacrylonitrile, ethyl acrylate--2-chloroethyl copolymer, acrylic acid-n-butyl-acrylonitrile copolymer, acrylonitrile-styrene air A copolymer, an acrylonitrile butadiene copolymer, an acrylonitrile butadiene styrene copolymer, etc. are mentioned. Among these, especially polymethyl methacrylate (PMMA) can be used preferably. As a polymethyl methacrylate (PMMA), a well-known thing can be used, Usually, it is preferable to manufacture by mass-polymerizing the methyl methacrylate monomer in presence of a peroxide and the azo-type polymerization initiator.

It is preferable that the molecular weights of the thermoplastic polyacrylic-acid alkylester type resin which is (C) component are 200-100,000, More preferably, it is 20,000-60,000. When the molecular weight is 200 to 100,000, phase separation between the component (A) and the component (C) is not too fast at the time of molding, so that sufficient transparency can be obtained in the optical sheet.

Although the method of manufacturing the optical sheet of this invention is not specifically limited, According to the manufacturing method of the following optical sheet of this invention, a desired optical sheet can be manufactured.

The manufacturing method of the optical sheet of this invention is a shaping | molding process which melt-extrudes the said aromatic polycarbonate resin composition to a sheet form, the cooling process of quenching a melt-extruded sheet-like molded object below glass transition temperature, and a cooled sheet-like molded object And a heat treatment step of heat treatment at 50 ° C. or higher and below the glass transition temperature of the polycarbonate resin.

In the cooling step, the sheet-shaped molded body can be cooled by passing the sheet-shaped molded body through the slit in which cooling water flows. The heat treatment step may be performed by sandwiching the front and back surfaces of the sheet-shaped molded body with a mirror-shaped metal endless belt and / or metal roll.

As an extrusion molding method, manufacture of the optical sheet which can be used as a light guide plate is possible by selecting shaping | molding conditions also in the sheet molding machine provided with the 3 rolls generally used. Although the cylinder temperature of the extruder and the temperature of die | dye depend on difference in resin composition, glass transition temperature, etc., it is 220-340 degreeC, Preferably it is about 240-320 degreeC.

When the ratio of (A) component / (C) component is 99.99 / 0.01-99.00 / 1.00 (mass ratio), and (B) extrusion molding is carried out as a raw material the resin composition containing antioxidant at the above ratios. The cooling process which quenchs the sheet-like molded object obtained by said melt extrusion below glass transition temperature is important, The one which applies the extrusion molding apparatus provided with such a cooling process is more optically transparent, and an optical sheet is higher. Can be obtained.

Cooling temperature needs to be below glass transition temperature, Preferably it is 140 degrees C or less, More preferably, it is 120 degrees C or less. By making cooling temperature below glass transition temperature, the total light transmittance in 0.1-1 mm of thickness of an optical sheet can be 91% or more. The lower limit of the cooling temperature depends on the difference in the composition of the resin, the glass transition temperature and the like, but is about 50 ° C. By setting it as 50 degreeC or more, residual strain in a molded optical sheet can be reduced and optical isotropy can be ensured. Cooling is normally performed using a some roll.

The cylinder temperature of an extruder is 220-340 degreeC, Preferably it is about 240-320 degreeC.

In addition, the cooled sheet-shaped molded body is 50 ° C. or more and uniformly free of wrinkles by opening and shaping the residual strain caused by the above-mentioned quenching step once by a heat treatment step of heat treatment at the glass transition temperature of the aromatic polycarbonate. With one thickness, an optical sheet with a low retardation value can be obtained.

By applying the extrusion molding machine provided with these manufacturing processes, the phase separation which arises in a cooling process from the molten state of the resin composition whose ratio of (A) component / (C) component is 99.99 / 0.01-99.00 / 1.00 (mass ratio) can be suppressed. It is possible to suppress the decrease in the light transmittance.

As a manufacturing method provided with these processes, an elastic roll method, the steel belt method, etc. are mentioned, Application of the extrusion molding machine provided with these is more preferable.

As a steel belt method, the manufacturing method disclosed by Unexamined-Japanese-Patent No. 2004-230598 is mentioned, for example.

In this manufacturing method, a sheet formed by winding in a plurality of rolls and mounted on an endless belt heated by a heating roll unit is brought into close contact with each other, and then the sheet is subjected to a planar or linear pressure contact between the endless belt and the roll. Then, as a manufacturing method of the sheet | seat which peels the sheet | seat from the said endless belt, the heated sheet | seat is heat-retained and / or heated while running from the opposite side to the endless belt of the sheet | seat (refer FIG. 1). Thermal insulation and / or heating is performed by a heat insulation board, hot air injection, and infrared rays.

1, 1 is a tension roll, 2 is a heating roll, 3 is a cooling roll, 4 is a pinching roll, 5 is an endless belt, 6 is a sheet feed roll, 7 is a tension roll, and 8 is a heating apparatus. S represents the sheet before transferring the uneven shape, and d represents the length of the sheet that is pinched between the pinching roll 4 and the endless belt 5.

As an elastic roll method, the method disclosed by Unexamined-Japanese-Patent No. 2004-155101 is mentioned, for example.

In this manufacturing method, a T-type die is attached to an extruder to form a sheet, and the sheet is passed through a first pinching roll, a second pinching roll, and a third pinching roll, and the plurality of feed rolls are arranged in a straight line to form a sheet. It is a method of manufacturing and manufacturing by passing a takeover roll (refer FIG. 2).

In FIG. 2, 21 is an extruder, 22, 23, 25 are pinching rolls, 24 is a take-up roll, 26a, 26b, and 26c are feed rolls.

Next, the molded object of this invention, such as a light guide plate in which the uneven | corrugated pattern was formed in the surface of the said optical sheet is demonstrated.

The optical sheet obtained by the above characteristics, composition, and manufacturing method is formed into a molded body by forming a fine concavo-convex pattern on the surface thereof, and light distribution control is possible, and a light guide plate, a diffusion sheet, a retroreflective plate, a prism sheet, a fresnel lens sheet, etc. It can be used as. Examples of the uneven pattern include a dot shape, a convex lens shape, a concave lens shape, a V groove prism shape, and a polygonal prism shape such as a triangular weight or a square weight.

In the light guide plate, it is preferable to give a gradation (lightness) to the uneven pattern.

It is preferable to form a uniform pattern in the usual diffusion sheet, retroreflective plate, and prism sheet.

In the case of the diffusion sheet used in the direct type backlight, the uniformity of luminance can be attained by forming the uneven pattern between the light source shadow on the light source and the distance between the light sources.

The roll embossing method, the vacuum press molding method, the belt transfer method, etc. are mentioned as a formation method of such an uneven | corrugated pattern. Above all, a mold in which a fine concavo-convex pattern is formed on a nickel plated foil on a belt-shaped thin stainless steel surface is produced, and each step of heating, pressure transfer, and peeling is continuously performed while synchronously conveying a resin film between the mold belts rotating up and down. It is preferable to apply the belt transfer method (for example, Unexamined-Japanese-Patent No. 2005-321681) using the apparatus provided with the means to implement. In this method, time for vacuuming, raising the temperature and lowering the temperature is unnecessary, and transfer to a large area can be performed with high productivity (see FIG. 3).

In FIG. 3, 31 is a heating roll, 32 is a transfer roll for forming an unevenness | corrugation, 33 is a preheating roll, 34 is a cooling roll, 35 is a conveyance roll, and 36 is an endless belt. The arrow on the left represents an optical sheet before transferring the uneven shape, and the arrow on the right represents a molded body such as an optical sheet after transfer, that is, a light guide plate.

In addition, a lithography method of curing with ultraviolet rays, a screen printing method using a white ink, or the like can be applied while using a mold having a fine concavo-convex pattern to push the acrylic ultraviolet curable resin into the optical sheet of the present invention and to touch it.

The molded article, such as a light guide plate, can also be manufactured by performing simultaneously the said optical sheet shaping | molding and the process of forming an uneven | corrugated pattern on a surface. As a manufacturing apparatus provided with such a simultaneous process, Toshiba Machine Co., Ltd. continuous extrusion embossing molding machine SPU-03026W can be used preferably (refer FIG. 4).

In the apparatus shown in FIG. 4, the crimping length becomes long by the flexibility of a special touch roll, and a transfer rate improves. In addition, the gap and the pressing force can be measured and controlled by the roll gap adjustment method (Pressure sensor and Positioning sensor).

Example

Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.

The compounding material etc. which were used in the Example and the comparative example are as follows.

<Compound material>

(1) aromatic polycarbonate PC1

Taflon FN1700A [Bisphenol A polycarbonate resin made by Idemitsu Heungsan Co., Ltd., glass transition temperature: 142 degreeC, viscosity average molecular weight: 17,300, refractive index: 1.585]

(2) aromatic polycarbonate PC2

Taflon FN1900A [Bisphenol A polycarbonate resin manufactured by Idemitsu Heungsan Co., Ltd., glass transition temperature: 145 degreeC, viscosity average molecular weight: 19,500, refractive index: 1.585]

(3) aromatic polycarbonate PC3

Taflon FN2500A [Bisphenol A polycarbonate resin manufactured by Idemitsu Heungsan Co., Ltd., glass transition temperature: 148 degreeC, viscosity average molecular weight: 23,500, refractive index: 1.585]

(4) phosphorus antioxidant

Adegastab PEP36 [bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol phosphite by Asahi Telephone Co., Ltd.]

(5) phenolic antioxidant

Irganox 1076 [Phenol-based antioxidant, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate manufactured by Chiba Specialty Chemicals Co., Ltd.] IRG1076 ".

(6) thermoplastic polyacrylic resin

Diamond BR83 [manufactured by Mitsubishi Rayon Co., Ltd., molecular weight: 25,000, refractive index 1.490, molecular weight using an Ostwald-type viscosity tube to measure the intrinsic viscosity [η] of the chloroform solution at 25 ° C. The average degree of polymerization PA was calculated and calculated. logPA = 1.613 log ([η] × 10 ⁴ /8.29)]

In Table 1, it describes as "acrylic acid ester resin."

(7) blue dye

HOSTALUX KSN [manufactured by Clarity Japan Co., Ltd., 4- (benzooxazol-2-yl) -4 '-(5-methylbenzooxazol-2-yl) stilbene and blue pigment]

<Kneading Extrusion>

Each material was mixed at the blending ratio in each Example and Comparative Example shown in Table 1 using a tumbler, melt-kneading extrusion was carried out at 280 degreeC using the single screw extruder of a screw diameter of 65 mm, and the pellet used in each example was used. Was produced.

<Optical sheet extrusion molding>

Condition 1 (applied in Examples 1 to 4 and Comparative Examples 1 and 2)

The optical sheet (thickness 0.4mm) was manufactured by the "three roll apparatus" which installed the extruder 21 shown in FIG. The 1st narrowing roll 22 of the screw diameter 65mm of the extruder 21 and the width | variety of a T die | dye of 650mm, and diameter 300mm was used. As for the 2nd pinching roll 23 and the 3rd pinching roll 25, the metal roll of 300 mm in diameter was used. The feed roll 26 used what arrange | positioned three metal rolls of diameter 70mm in linear form. In addition, the total distance between the first feed roll 26a and the last feed roll 26c was 3 m.

Condition 2 (applied in Example 5)

It carried out using the UF roll narrow compression extrusion machine (elastic roll method-refer FIG. 2) by Hitz-Sangi Techno Co., Ltd. product. The screw diameter of the extruder is 90 mm.

Condition 3 (applied in Example 6)

Using a continuous extrusion emboss molding machine SPU-03026W (see Fig. 4) manufactured by TOSHIBA MACHINERY CO., LTD., The sheet obtained by sheet molding was pressed strongly to a stamper in which a triangular prism array (50 μm in height) was formed by nickel plating, thereby simultaneously performing pattern transfer. The prism sheet was produced by performing (pattern formation 2). The screw diameter of 26 mmφ of an extruder and the temperature of each other part are as having shown in Table 1.

Condition 4 (applied in Comparative Example 3)

It carried out similarly to the condition 1 except having changed the temperature of each place into the temperature shown in Table 1.

Condition 5 (applies to Comparative Example 4)

Injection molding was performed at the molding temperature of 360 degreeC (mold temperature 120 degreeC) using the injection molding machine (Sumitomo Heavy Industries, Ltd. make, article number SG100M-HP) of 100 tons of mold clamping force.

<Pattern Transfer by Press Molding>

Each optical sheet produced in each of Examples and Comparative Examples other than Example 6 was vacuum sucked by a micro pattern transfer vacuum press manufactured by Macy Corporation, and a triangular prism array (50 µm in height) was formed by nickel plating. It pressed hard by a stamper and press-molded at 160 degreeC, and produced the light guide plate (pattern formation 1).

<Evaluation method>

(1) total light transmittance

It measured based on JIS-K-7105 using the haze meter (HGM-2DP) made from Suga Test Machine Co., Ltd.

(2) spectral light transmittance of the sheet

The optical sheet sample of thickness 0.4mm was measured with the UV visible spectrophotometer (UV-2450) by Shimadzu Corporation, and the spectral light transmittance (%) in wavelength 300nm was measured.

(3) birefringence (retardation) and its standard deviation value

The birefringence (retardation value) with respect to 550 nm was measured with the retardation measuring apparatus (RETS-100) made from Otsuka Electronics.

In the present invention, an arbitrary point is a 3 cm x 3 cm lattice image of a 1 cm pitch of 4 cm x 4 cm portions of two points at which each measurement point is 60 cm or more away from a sample of an optical sheet of 100 cm x 100 cm. The measurement of 18 points in total was performed about 9 points.

formula :

Standard deviation (σ) =

n is the total number of samples measured

Re _n is the Re value of the nth sampling point

Re _av represents the average value of Re.

(4) Optical properties by spectrophotometer (spectral light transmittance)

a) sample preparation

The cut sample (6 g) was put into a measuring flask (50 milliliters), and dissolved by adding dichloromethane. Upon dissolution, ultrasonic irradiation was performed for 3 hours.

b) Measuring device: Shimadzu Corporation UV-2450

c) measurement conditions

Cell length: 5 cm

Measurement wavelength: 900 to 200 μm

Scan Speed: Set to Low Speed Mode

Slit Width: 2.0 nm

Switching wavelength: 360 nm

d) order of measurement

After starting and stabilizing the apparatus 2 hours before the measurement, the baseline is measured, and then it is checked by measuring auto zero at 500 nm to determine whether a zero point is obtained.

Wash the cell well with dichloromethane and acetone, wait until the cell temperature reaches room temperature, add the measurement solution at the point of time when the cell temperature returns, place the cell in the measuring room, cover and leave for 1 minute. , Measurement starts. After completion of the measurement, the measurement solution is taken out and washed, and the sample is changed to repeat this.

(5) Transferability of uneven pattern

About each light guide plate obtained by Examples 1-6 and Comparative Examples 1-4, the transfer rate of the pattern which reflects a brightness characteristic was implemented instead of brightness evaluation.

Transfer rate (%) = [height of the triangular weight (μm) / stamper of the transferred light guide plate (50 μm)] × 100

[Examples 1 to 6]

Using each pellet manufactured by melt-kneading extrusion using the compounding material shown in Table 1, using the molding conditions of "condition 1", "condition 2", or "condition 3", an optical sheet was produced and each The light guide plate was produced by applying the said pattern formation 1 (Examples 1-5) or the pattern formation 2 (Example 6) to an optical sheet. The temperature at each site in each condition is as described in Table 1.

[Comparative Examples 1-4]

Using each pellet produced by melt-kneading extrusion using the compounding materials shown in Table 1, using the molding conditions of "Condition 1", "Condition 4" or "Condition 5", an optical sheet was produced, and each The light guide plate was produced by applying the said pattern formation 1 to an optical sheet. The temperature at each site in each condition is as described in Table 1.

Industrial availability

The optical sheet of the present invention controls a higher-order structure in a solid structure by extruding a resin composition containing a specific aromatic polycarbonate under specific conditions, and optimizes the concave-convex pattern to be formed on the surface according to the use, thereby guiding a light guide plate, a diffusion sheet, It is processed into a retroreflective plate or a brightness enhancing prism sheet.

1: tension roll
2: heating roll
3: cooling roll
4: pinch roll
5: stepless belt
6: sheet feed roll
7: tension roll
8: heating device
S: Sheet before transferring uneven shape
d: length of sheet clamped by pinching roll and endless belt
21: extruder
22: pinch roll
23: pinch roll
24: takeover roll
25: pinch roll
26a: feed roll
26b: feed roll
26c: feed roll
31: heating roll
32: transfer roll for forming irregularities
33: preheat roll
34: cooling roll
35: conveying roll
36: endless belt

Claims (9)

After the aromatic polycarbonate resin composition containing (A) 100 mass parts of aromatic polycarbonates with a viscosity average molecular weight of 22000 or less, and 0.01-1 mass part of (B) antioxidant, and does not contain a blue pigment or a pigment, is extruded from an extruder, An optical sheet cooled below the glass transition temperature,
The total light transmittance in thickness of 0.1-1 mm of the said optical sheet is 91% or more, The optical sheet characterized by the above-mentioned. The method of claim 1,
The optical sheet whose birefringence (phase difference; retardation value in wavelength 550nm) is 150 nm or less, and the standard deviation value of the retardation value in arbitrary points in a sheet surface is 10 or less. The method of claim 1,
In the visible-UV spectral spectrum measured at 0.4 mm of the sample plate thickness prepared with the aromatic polycarbonate resin composition used for the said optical sheet, 70% or more of the spectral light transmittance at wavelength 300nm, or an aromatic polycarbonate are good solvents The optical sheet whose spectral light transmittance (measured by the solution method: light guide length of a solution cell is 5 cm, sample solution concentration 12 g / dl, solvent dichloromethane, wavelength 450 nm) measured by melt | dissolving and measuring in 94% or more. The method of claim 1,
The optical sheet containing 0.01-1 mass part of (C) thermoplastic polyacrylic-type resins with respect to 100 mass parts of said (A) component. The method of claim 1,
The optical sheet whose antioxidant of the said (B) component is a phosphorus antioxidant and / or a phenolic antioxidant. As a manufacturing method of the optical sheet of Claim 1,
The molding process of melt-extrusion of the aromatic polycarbonate resin composition into a sheet shape, the cooling step of rapidly cooling the melt-extruded sheet-like molded product to a glass transition temperature or less, and the cooled sheet-shaped molded product are 50 ° C. or more and the aromatic polycarbonate resin The heat treatment process of heat-processing below the glass transition temperature of a composition, The manufacturing method of the optical sheet characterized by the above-mentioned. The molded object formed by forming an uneven | corrugated pattern on the surface of the optical sheet of Claim 1. The method of claim 7, wherein
The molded object which is any of a light guide plate, a diffusion sheet, a retroreflective plate, a prism sheet, and a Fresnel lens sheet. The uneven | corrugated pattern is formed in the surface of the optical sheet of Claim 1, The manufacturing method of the molded object characterized by the above-mentioned.

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