JP2005096421A - Aromatic polycarbonate resin pellet for light guide plate, light guide plate, method for manufacturing light guide plate and surface illuminant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate which does not mar the characteristics of an aromatic polycarbonate resin; shows high light transmittance/ brightness and high degree of brightness uniformity; an aromatic polycarbonate resin pellet best suited for the manufacture of the light guide plate; a method for manufacturing the light guide plate; and a surface illuminant using the light guide plate. <P>SOLUTION: The aromatic polycarbonate resin pellet for the light guiding plate contains not more than 50,000 pieces/g of dust with a particle diameter of 0.5 to 1.0 μm and not more than 3,000 pieces/g of dust with a particle diameter exceeding 1.0 μm. The light guiding plate is formed of the aromatic polycarbonate resin and contains not more than 50,000 pieces/g of dust with a particle diameter of 0.5 to 1.0 μm and not more than 3,000 pieces/g of dust with a particle diameter exceeding 1.0 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aromatic polycarbonate resin pellet for a light guide plate and a light guide plate comprising the same, and in particular, is excellent in mechanical properties, thermal properties, electrical properties and weather resistance, in particular, light transmittance, brightness and good brightness. The present invention relates to a light guide plate having a degree of uniformity and an aromatic polycarbonate resin pellet for a light guide plate suitable as a material for the light guide plate.

  Liquid crystal display devices used in personal computers, mobile phones, PDAs, and the like incorporate a surface light source device in order to achieve thinness, weight reduction, power saving, high brightness, and high definition of the device. . This planar light source device is provided with a light source and a light guide plate, and the light guide plate is usually a transparent plate-shaped article having a wedge-shaped cross section with one inclined surface having a uniform inclination. . Conventionally, the light guide plate has been formed from a material such as polymethyl methacrylate (PMMA) resin. However, in recent years, since heat generated in devices such as personal computers, mobile phones, and PDAs has increased, aromatic polycarbonate resin materials having high heat resistance are being used instead of PMMA resins.

  The aromatic polycarbonate resin is excellent in mechanical properties, thermal properties, electrical properties, and weather resistance, but its light transmittance is lower than that of the PMMA resin. Therefore, when an aromatic polycarbonate resin is used as the light guide plate of the surface light source body, there is a problem that the luminance is lowered.

  As a method for solving the above problem, there is a method of using, as a light guide plate material, an aromatic polycarbonate resin in which a substance that improves the luminance of a planar light source body such as an acrylic resin such as PMMA and / or an alicyclic epoxy compound is blended. It is known (see, for example, Patent Document 1). However, the light guide plate obtained from this aromatic polycarbonate resin composition becomes clouded by the addition of the acrylic resin, the light transmittance and the luminance are not sufficiently improved, and it is sufficient even if an alicyclic epoxy compound is added. Improvement effect is not recognized.

  It is also known to use a polycarbonate resin composition comprising a copolymerized polyester carbonate having an aliphatic segment and an aromatic polycarbonate and having improved mechanical strength and fluidity for a light guide plate (for example, Patent Document 2). reference). However, although the luminance of the planar light source body provided with the light guide plate made of this type of polycarbonate resin composition is improved, this type of polycarbonate resin composition has insufficient heat resistance. Problems arise.

  Furthermore, it is composed of 100 parts by mass of an aromatic polycarbonate resin and 0.001 to 1 part by mass of another thermoplastic resin such as PMMA whose refractive index difference between the aromatic polycarbonate resin is 0.001 or more, and has a thickness of 2 mm. An aromatic polycarbonate resin composition having a ratio (X) / (Y) of a spectral light transmittance (X) at a wavelength of 320 nm measured with a sample plate and a spectral light transmittance (Y) at a wavelength of 633 nm of 0.5 or more. The light guide plate used is also known (see, for example, Patent Document 3). However, even in this case, the light guide plate becomes clouded by the addition of the acrylic resin, and the light transmittance and luminance are not sufficiently improved.

JP-A-11-158364 JP 2001-215336 A JP 2002-060609 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide a light guide plate having excellent light transmittance, luminance, and luminance uniformity without impairing the characteristics of the aromatic polycarbonate resin, and such a light guide plate. To provide an aromatic polycarbonate resin pellet for a light guide plate suitable for obtaining, a method for producing the light guide plate, and a surface light source body using the light guide plate.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have focused on dust mixed from the raw material aromatic polycarbonate resin and the molding process, and the dust having a particle size close to the wavelength region of visible light. The use of aromatic polycarbonate resin pellets with a controlled number of materials as the material of the light guide plate, and the light transmittance, luminance, and brightness leveling of the surface light source body using the light guide plate with the number of dust particles having the specific particle size controlled. The knowledge that the degree was excellent was obtained, and the present invention was completed.

  The present invention has been completed based on the above findings, and the first gist thereof is that the content of dust having a particle size of 0.5 to 1.0 μm is 50,000 / g or less, and The present invention resides in an aromatic polycarbonate resin pellet for a light guide plate, wherein the content of dust having a particle size of 1.0 μm or less is 3,000 pieces / g or less.

  The second gist of the present invention is formed from an aromatic polycarbonate resin, the content of dust having a particle size of 0.5 to 1.0 μm is 50,000 / g or less, and a particle size of 1.0 μm. It exists in the light-guide plate characterized by the content of excess dust being 3,000 pieces / g or less.

  The third gist of the present invention resides in the above-described method for producing a light guide plate, wherein the aromatic polycarbonate resin pellet for the light guide plate is molded.

  The fourth gist of the present invention resides in a surface light source body including the light guide plate and a light source.

  Since the amount of dust having a specific particle diameter is controlled, the aromatic polycarbonate resin pellet for the light guide plate of the present invention can be suitably used as a light guide plate material having high total light transmittance and high brightness and high brightness uniformity. In addition, since the light guide plate of the present invention controls the amount of dust having a specific particle diameter, it is used together with a light source to obtain a surface light source body having high total light transmittance, high brightness, and high brightness uniformity. I can do it.

  Hereinafter, the present invention will be described in detail. First, the aromatic polycarbonate resin pellet for a light guide plate of the present invention will be described. The aromatic polycarbonate resin used as the raw material for the aromatic polycarbonate resin pellet for the light guide plate is a polymer or copolymer obtained by reacting a dihydroxydiaryl compound with a carbonate precursor such as phosgene or carbonic acid diester. A typical example is a polycarbonate resin produced from 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A).

  Examples of the raw material dihydroxydiaryl compound include bisphenol A, bis (4-hydroxydiphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxydiphenyl) butane, 2, 2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (4-hydroxy-3- Tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4 -Bis (hydroxyaryl) alkanes such as hydroxy-3,5-dichlorophenyl) propane, 1,1-bis (4 Bis (hydroxyaryl) cycloalkanes such as hydroxyphenyl) cyclohexane, dihydroxydiaryl ethers such as 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′-dimethyldiphenyl ether, 4,4′- Dihydroxyphenyl sulfide, dihydroxydiaryl sulfides such as 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide Dihydroxydiaryl sulfoxides such as 4,4′-dihydroxydiphenyl sulfone, and 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfone. It is below. The dihydroxydiaryl compounds may be used alone or in combination of two or more. In addition to the dihydroxydiaryl compound, biperazine, dipiperidyl, hydroquinone, resorcin, 4,4'-dihydroxydiphenyl and the like may be mixed and used.

  Examples of the carbonate precursor to be reacted with the dihydroxydiaryl compound include diaryl carbonates such as phosgene, diphenyl carbonate and ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, and phosgene or diphenyl carbonate is preferable.

  The method for producing the aromatic polycarbonate resin is not particularly limited, and a known method such as an interfacial method using phosgene or a transesterification method using carbonic acid diester can be employed. Since the resin material used for forming the light guide plate is usually in the form of pellets, the powdery or flaky aromatic polycarbonate obtained by the above method is further pelletized for use.

  The viscosity average molecular weight of the aromatic polycarbonate resin used as a raw material for the aromatic polycarbonate resin pellet for the light guide plate of the present invention is usually 10,000 to 30,000, preferably 12,000 to 28,000, and more preferably 15. , 4,000 to 24,000. When the viscosity average molecular weight of the aromatic polycarbonate resin is less than 10,000, the light guide plate produced from the pellet has low rigidity and cannot be put to practical use. On the other hand, when the viscosity average molecular weight of the aromatic polycarbonate resin exceeds 30,000, injection molding becomes difficult because of poor fluidity. In the present invention, the viscosity average molecular weight (Mv) means a value calculated from an intrinsic viscosity (η) in a methylene chloride solution and a Schnell viscosity formula, as will be described later.

  In the aromatic polycarbonate resin pellet for the light guide plate of the present invention, the content of dust having a particle diameter of 0.5 to 1.0 μm is 50,000 / g or less, preferably 30,000 / g or less, and The dust content exceeding 1.0 μm is 3,000 / g or less, preferably 2,000 / g or less. When the aromatic polycarbonate resin pellet for the light guide plate of the present invention is molded into a light guide plate because the number of dust particles close to the wavelength region of visible light (350 to 800 nm) is defined as described above, the light beam is high. A light guide plate having transmittance and high average luminance and luminance uniformity can be obtained.

  When the content of the dust having a particle size of 0.5 to 1.0 μm in the aromatic polycarbonate resin pellet for the light guide plate exceeds 50,000 / g, the light transmittance, the average luminance, and the luminance uniformity are deteriorated. On the other hand, when the content of dust exceeding the particle size of 1.0 μm exceeds 3,000 / g, the light transmittance, the average luminance, and the luminance uniformity are deteriorated when the light guide plate is molded. Although the content of dust is preferably small, it can be used as a raw material for a light guide plate having excellent light transmittance, average luminance, and luminance uniformity within the above range. In addition, the definition of the dust in this invention, the measuring method of the number of dust, and the method of controlling the number of dust are mentioned later.

  As a method for producing an aromatic polycarbonate resin pellet for a light guide plate of the present invention, an additive described below is usually blended with polycarbonate resin powder as necessary, and melted and kneaded with an extruder or the like to form a pellet. To do. At this time, since the amount of dust in the pellets needs to be within the above range, it is necessary to pay sufficient attention to materials, equipment used, and working environment in the additive blending and pelletizing steps.

  Next, the light guide plate of the present invention will be described. The light guide plate of the present invention is formed of an aromatic polycarbonate resin, and the content of dust having a particle size of 0.5 to 1.0 μm is 50,000 / g or less, preferably 30,000 / g or less, and The dust content exceeding 1.0 μm is 3,000 / g or less, preferably 2,000 / g or less. When the content of dust having a particle size of 0.5 to 1.0 μm in the light guide plate exceeds 50,000 / g, the light transmittance, average luminance, and luminance uniformity deteriorate. On the other hand, when the content of dust exceeding the particle size of 1.0 μm exceeds 3,000 / g, the light transmittance, average luminance, and luminance uniformity are deteriorated. Although the content of dust is preferably small, it can be used as a light guide plate having excellent light transmittance, average luminance, and luminance uniformity within the above range.

  Although the manufacturing method of a light-guide plate is not specifically limited, For example, it can manufacture by employ | adopting a well-known method, normally injection molding method, and using aromatic polycarbonate resin by which the dust amount was controlled. In particular, in the production of the light guide plate of the present invention, the content of dust having a particle size of 0.5 to 1.0 μm is not more than 50,000 / g and the dust content exceeds 1.0 μm. It is preferable to use an aromatic polycarbonate resin pellet for a light guide plate whose amount is 3,000 pieces / g or less, and the content of dust having a particle size of 0.5 to 1.0 μm is 30,000 pieces / g or less. It is more preferable to use aromatic polycarbonate resin pellets for light guide plates having a dust content exceeding 2,000 particles / g.

  The shape of the light guide plate of the present invention is not particularly limited, and may be a flat plate shape or a curved plate shape having a lens effect according to the purpose and application. Preferably, it has a wedge shape having a tapered inclined surface. Furthermore, a preferred embodiment of the present invention includes a structure in which a prism-shaped uneven pattern is formed on the inclined surface of the wedge-shaped light guide plate. Such a concavo-convex pattern is imparted by transferring a concavo-convex portion formed on a part of the surface of a mold during injection molding. It is convenient and preferable to form the concavo-convex part in a nest that is a part of the mold.

  The aromatic polycarbonate resin pellet for the light guide plate of the present invention and the dust contained in the light guide plate are impurities in the raw material and auxiliary material of the aromatic polycarbonate resin as a material, resin production process, pelletizing process, light guide plate It is a generic term for substances that come from the environment and equipment in the molding process, polycarbonate cross-linked products, burnt garbage, etc. that are produced during polymer production and / or local overheating in the molding process.

  The method for controlling the aromatic polycarbonate resin pellets for the light guide plate and the number of dust in the light guide plate can be achieved, for example, by appropriately combining the following known means.

  1) A series of manufacturing, transportation and storage environment of aromatic polycarbonate resin, pellets and light guide plate. 2) Use of raw materials and / or secondary materials with reduced dust. 3) Use of special alloys on the inner surfaces of reaction equipment, purification equipment, melt-kneading equipment, molding machines, piping, transportation equipment, etc., inactivate parts that come into contact with products and eliminate stagnant places. 4) Removal of dust in raw materials and resin by installing filters in reaction equipment, purification equipment, melt kneading equipment, etc. 5) Prevent dust from entering the reaction equipment, melt-kneading equipment, piping, transportation equipment, etc. by installing filters. 6) Prevention of generation of dust such as cross-linking and burnt waste by controlling reaction conditions, melt-kneading conditions, and molding conditions. 7) Prevention of generation of dust such as cross-linking and burnt waste by blowing inert gas into reaction equipment, melt-kneading equipment and molding machine. 8) Prevention of generation of dust such as cross-linking and burnt waste during melt-kneading by adding antioxidant and heat stabilizer to resin. 9) Dust removal by dissolving the resin in a solvent and filtering and purifying with a filter.

  The light guide plate of the present invention can achieve a higher luminance increasing effect and luminance uniformity by containing a luminance improving agent. In addition, the aromatic polycarbonate resin pellet for the light guide plate can also be used as a raw material for the light guide plate that can achieve a higher brightness increasing effect and brightness uniformity by including a brightness improver. Here, the brightness improving agent means a substance having a refractive index smaller by 0.01 or more than the refractive index of the aromatic polycarbonate resin. The brightness enhancer is not particularly limited as long as it has excellent compatibility with the aromatic polycarbonate resin, does not impair the transparency, thermal characteristics, and mechanical characteristics of the aromatic polycarbonate, and has a sufficient brightness enhancement effect. Illustrative are organosiloxane compounds, paraffin waxes, polyalkylene glycols and fatty acid esters thereof.

  As said polyorganosiloxane compound, what has a phenyl group at least in a side chain and has a branched siloxane structure is preferable. The polyorganosiloxane compound may be a single compound or a mixture. In the case of a mixture, a polyorganosiloxane having at least a phenyl group in a side chain, a polyorganosiloxane having at least a branched siloxane structure, and May be used in combination.

  The polyorganosiloxane compound has a kinematic viscosity at 25 ° C. of usually 1 to 200 cSt, preferably 5 to 100 cSt, and more preferably 10 to 50 cSt. If the kinematic viscosity at 25 ° C. is too small, the amount of gas generated at the time of forming the light guide plate increases, and molding defects due to gas, for example, unfilling, gas burnout, and transfer defects may occur. On the other hand, when the kinematic viscosity exceeds 200 cSt, the effect of improving the hue and transmittance of the aromatic polycarbonate resin composition cannot be sufficiently obtained.

  The polyorganosiloxane compound can be easily obtained by a conventional organic reaction, and a commercially available product can also be used. A specific polyorganosiloxane compound preferably has a structure represented by the following general formula (1).

  The polyorganosiloxane compound is used in an amount of usually 0.01 to 1 part by weight, preferably 0.02 to 0.5 part by weight, more preferably 0.04 to 0.3 part per 100 parts by weight of the aromatic polycarbonate resin. Parts by weight. If the amount of polyorganosiloxane compound used is too small, the brightness enhancement effect is insufficient, while if the amount of polyorganosiloxane compound used is too large, the amount of gas generated during the formation of the light guide plate increases, resulting in poor molding. Gas burns and transfer defects may occur.

  Examples of the paraffin wax include saturated aliphatic hydrocarbons such as n-paraffin and / or i-paraffin, or a low molecular weight polyethylene having a hydroxyl group at the terminal and having a waxy appearance. The molecular weight of the saturated aliphatic hydrocarbon measured by GPC method is usually 300 to 1500, preferably 300 to 1000. The paraffin wax can be easily produced by a conventional organic reaction, and a commercially available product can also be used.

  The amount of the paraffin wax used is 0.01 to 1 part by weight, preferably 0.02 to 0.7 part by weight, more preferably 0.04 to 0.5 part by weight, based on 100 parts by weight of the aromatic polycarbonate resin. It is. If the amount of paraffin wax is too small, the brightness enhancement effect is insufficient. On the other hand, if the amount of paraffin wax is too large, the amount of gas generated during light guide plate molding increases, resulting in molding defects, gas burns, and transfer defects. It can be a cause.

  The polyalkylene glycol and the fatty acid ester thereof are represented by the following general formula (2) and can be easily obtained by a conventional organic reaction.

  In the said General formula (2), the polymerization degree q is 10-400 normally, Preferably it is 15-200, More preferably, it is 20-100. When the degree of polymerization q is less than 10, the amount of gas generated during the formation of the light guide plate increases, which may cause molding defects, gas burns, and transfer defects. On the other hand, when the polymerization degree q exceeds 400, the effect of improving the hue and transmittance of the aromatic polycarbonate cannot be sufficiently obtained.

Specific examples of the polyalkylene glycol include polyethylene glycol in which R in the general formula (2) is a hydrogen atom, and polypropylene glycol in which a methyl group is used. In addition, as the fatty acid ester of polyalkylene glycol, polyethylene in which R in the general formula (2) is a hydrogen atom, and X and Y are aliphatic acyl groups having 18 carbon atoms (stearoyl group: C ₁₇ H ₃₅ CO—). Glycol stearate, R is a methyl group, polypropylene glycol stearate where X and Y are stearoyl groups, R is a hydrogen atom, X and Y are aliphatic acyl groups having 22 carbon atoms, R is methyl Polypropylene glycol behenate, in which the groups X and Y are aliphatic acyl groups having 22 carbon atoms, is preferred because it is readily available. The above polyalkylene glycols and fatty acid esters of polyalkylene glycols may be used alone or in combination of two or more. In addition, when the shaping | molding temperature at the time of obtaining a light-guide plate exceeds 300 degreeC, it is preferable to use the fatty acid ester of polyalkylene glycol from a heat resistant viewpoint.

  The polyalkylene glycol and the fatty acid ester thereof are used in an amount of 0.01 to 1 part by weight, preferably 0.05 to 0.8 part by weight, more preferably 0.08 to 100 parts by weight of the aromatic polycarbonate resin. 0.4 parts by weight. When the amount of the polyalkylene glycol and its fatty acid ester is too small, a sufficient brightness enhancement effect cannot be obtained. On the other hand, when the amount used is too large, the aromatic polycarbonate resin becomes cloudy and the transmittance decreases.

  It is preferable to add an antioxidant to the aromatic polycarbonate resin pellet for the light guide plate and the light guide plate of the present invention in order to improve light transmittance and hue and to prevent dust generation such as burned dust. Examples of the antioxidant include phosphorus-based antioxidants such as phosphites and phosphates.

  Examples of the phosphite include triphenyl phosphite, trisnonylphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, trinonyl phosphite, tridecyl phosphite, and trioctyl phosphite. , 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, bis (2,4-dicumylphenyl) pentaeryth Diphosphite, triester of 2,2-methylenebis (4,6-di -tert- butylphenyl) phosphite, such as octyl phosphite, diesters, monoesters, and the like.

  Examples of the phosphoric acid ester include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris (nonylphenyl) phosphate, 2-ethylphenyldiphenyl phosphate, tetrakis (2,4- And di-tert-butylphenyl) -4,4-diphenylene phosphonite.

  Among the above phosphorus antioxidants, distearyl pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol phosphite, bis (2,6-di-tert-butyl-4-) Methylphenyl) pentaerythritol phosphite and tris (2,4-di-tert-butylphenyl) phosphite are preferred, pentaerythritol type, especially bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol Phosphite is particularly preferred. In addition, a phosphorus antioxidant may be used independently and may be used in combination of 2 or more type. The usage-amount of phosphorus antioxidant is 0.005-0.2 weight part normally with respect to 100 weight part of aromatic polycarbonate resin, Preferably it is 0.01-0.1 weight part.

  The aromatic polycarbonate resin pellet for light guide plate and light guide plate of the present invention are not limited to other thermoplastic resins, flame retardants, impact resistance improvers, slip agents, lubricants, release agents as long as the object of the present invention is not impaired. Additives commonly used in light guide plate production such as molds, antifogging agents, and colorants can be blended.

  The surface light source body of the present invention comprises the light guide plate of the present invention and a light source. For example, a light source is placed at the thick end of a wedge-shaped light guide plate and used for mobile phones, mobile terminals, cameras, watches, notebook computers, displays, lighting, signals, automobile tail lamps, electromagnetic cooker thermal power displays, etc. The edge type surface light source body is configured. As a light source, a self-luminous body such as a cold cathode tube, an LED, and an organic EL can be used in addition to a fluorescent lamp.

  When the surface light source body of the present invention is used in a liquid crystal display device, either a backlight method or a front light method can be adopted. As an example, FIG. 1 shows a conceptual diagram of a backlight type surface light source body, and FIG. 2 shows a conceptual diagram of a front light type surface light source body.

  In the case of the backlight system shown in FIG. 1, the reflection member (4) is disposed to face the first surface (11) of the light guide plate (1). Further, a liquid crystal display element (panel) (3) is arranged facing the second surface (12) of the light guide plate (1). The light emitted from the light source (2) is incident from the end of the light guide plate (1), collides with the concavo-convex portion provided on the first surface (11), is scattered, and is emitted from the first surface (11). Then, the light is reflected by the reflecting member (4), reenters the first surface (11), is emitted from the second surface (12), and irradiates the liquid crystal display element (3). For example, a diffusion sheet (5) or a prism sheet (not shown) may be disposed between the liquid crystal display element (3) and the second surface (12). In addition, when not providing an uneven | corrugated | grooved part in a light-guide plate, directionality is provided to light using a some prism sheet.

  In the case of the front light system shown in FIG. 2, the liquid crystal display element (3) is arranged to face the second surface (12). The light emitted from the light source (2) is incident on the light guide plate from the end of the light guide plate (1), collides with the uneven portion provided on the first surface (11), and is scattered, and the second surface (12 ), Passes through the retardation film (or polarizing film) (6), and passes through the liquid crystal display element (3). And the light inject | emitted from the liquid crystal display element (3) is reflected by the reflection member (4) arrange | positioned on the outer side of a liquid crystal display element (3), passes again through a liquid crystal display element (3), and retardation film (Or polarizing film) passes through (6), further passes through the light guide plate (1), and is emitted from the first surface (11). This light is recognized as an image or the like displayed on the liquid crystal display element (3). Usually, an antireflection layer (not shown) is formed on the surface of the second surface (12).

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples, unless the summary is exceeded. Below, the raw material used in each Example and the comparative example is demonstrated.

Aromatic polycarbonate resin:
Poly-4,4-isopropylidene diphenyl carbonate (Mitsubishi Gas Chemical's "Iupilon H-4000F" flakes were treated by the following method to remove dust, and then a single screw extruder with a vent with a screw diameter of 40 mm was used. Then, melting, kneading and extruding were performed at a cylinder temperature of 250 ° C., and the obtained strand was cut to produce aromatic polycarbonate resin pellets for a light guide plate, where the viscosity average molecular weight (Mv) of these aromatic polycarbonate resins is 16,000, the refractive index (n _D ) is 1.58 (25 ° C.).

  PC1: "Iupilon H-4000F" flakes were dissolved in methylene chloride to prepare a 12% resin solution. This resin solution was filtered through a filter having a pore size of 5 μm. Further, the mixture was filtered with a filter having a pore size of 3 μm, further filtered twice with a filter having a pore size of 1 μm, the filtrate was heated to evaporate and remove the solvent, and the resulting resin flakes were pelletized in a clean room.

  PC2: “Iupilon H-4000F” flakes were dissolved in methylene chloride to prepare a 12% resin solution. This resin solution was filtered through a filter having a pore size of 5 μm. Further, the mixture was filtered through a filter having a pore diameter of 3 μm and then a filter having a pore diameter of 1 μm, the filtrate was heated to evaporate and remove the solvent, and the resulting resin flakes were pelletized in a clean room.

  PC3: “Iupilon H-4000F” flakes were dissolved in methylene chloride to prepare a 12% resin solution. This resin solution was filtered through a filter having a pore size of 5 μm. Furthermore, it filtered with the filter of 3 micrometers of hole diameters, the filtrate was heated, the solvent was evaporated and removed, and the obtained resin flakes were pelletized in the clean room.

  PC4: “Iupilon H-4000F” flakes were dissolved in methylene chloride to prepare a 12% resin solution. This resin solution was filtered through a filter having a pore size of 5 μm. The filtrate was heated to evaporate and remove the solvent, and the resulting resin flakes were pelletized in a clean room.

  PC5: “Iupilon H-4000F” flakes were pelletized in a clean room.

  PC6: “Iupilon H-4000F” flakes were dissolved in methylene chloride to prepare a 12% resin solution. This resin solution was filtered through a filter having a pore size of 5 μm. The filtrate was heated to evaporate and remove the solvent, and the resulting resin flakes were pelletized in a normal chamber.

  Regarding the “PC1” to “PC6” obtained above, the amount of dust in the resin flakes before pelletization and the pelletization conditions are summarized in Table 1 below. In addition, the dust 1 and the dust 2 in a table | surface were calculated | required according to the below-mentioned evaluation method.

  Antioxidant: “ADK STAB AS2112” manufactured by Asahi Denka Kogyo Co., Ltd. (phosphorus antioxidant, tris (2,4-di-t-butylphenyl) phosphite)

Brightness improver: “KF56” manufactured by Shin-Etsu Chemical Co., Ltd. (dimethyldiphenylsiloxane (containing branched type phenylsiloxane), n _D = 1.50 (25 ° C.), kinematic viscosity = 15 cSt)

Brightness improver: “SH556” manufactured by Toray Dow Corning Silicone (methylphenylsiloxane (containing branched type phenylsiloxane), n _D = 1.46 (25 ° C.), kinematic viscosity = 22 cSt)

Brightness improver: “NKL-9520” (polypropylene glycol distearate (degree of polymerization 30-40), n _D = 1.44 (25 ° C.)) manufactured by NOF Corporation

Brightness improver: “155WAX” (paraffin wax, n _D = 1.43 (80 ° C.)) manufactured by Nippon Seiki Co., Ltd.

  The evaluation methods used in each example and comparative example are as follows.

(1) Viscosity average molecular weight:
A methylene chloride solution (concentration 0.5 g / ml) of polycarbonate resin was prepared, and an intrinsic viscosity [η] at 25 ° C. was measured by a volumetric method using an Ubbelohde viscometer. The viscosity average molecular weight was calculated from the following Schnell equation.

(2) Dust:
A sample solution is prepared by dissolving 1 g of a polycarbonate resin pellet or a small piece of a light guide plate in 100 ml of methylene chloride filtered through a filter having a pore size of 0.05 μm. The sample solution was passed through a liquid fine particle counter manufactured by HIAC / ROYCO, and the number of dusts was measured by a light scattering method and a light blocking method. The number of dusts in 1 g of the sample was determined with the dust having a particle size of 0.5 to 1.0 μm as dust 1 and the dust having a particle size exceeding 1.0 μm as dust 2. In addition, when there is a possibility that the surface of the polycarbonate resin pellet or the light guide plate is contaminated with dust before being dissolved in methylene chloride, pure water with a particle size of 0.5 to 1.0 μm is 10 / g or less. After ultrasonic cleaning, it was dissolved in methylene chloride.

(3) Total light transmittance:
Using an injection molding machine (“J50” manufactured by Nippon Steel Co., Ltd.), an aromatic polycarbonate resin pellet for a light guide plate was molded into a plate (90 mm × 50 mm × 3 mm thickness) at a temperature of 300 ° C. Using a turbidity meter (“NDH-2000 type” manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance of the obtained plate was measured.

(4) Average brightness and brightness uniformity:
In the dark room, the light guide plate was arranged so that the concave / convex pattern forming surface was on the lower surface side, and the cold cathode tube was arranged at the thick end portion to produce an edge type front light type surface light source body. Next, a luminance meter ("Topcon BM-7" manufactured by Topcon Co., Ltd.) was installed at a position 30 cm above the uneven pattern non-forming surface side, and the luminance was measured. The average luminance was obtained by averaging the measured values at a total of 9 locations of 3 levels in width and 3 levels in length. Further, the luminance uniformity was calculated by the following formula.

Examples 1-4, Reference Examples 1-2 and Comparative Example 1:
The pellets obtained by blending a polycarbonate resin and a stabilizer with the formulation shown in Table 2 or Table 3 and pelletized in the environment shown in Table 1 above were dried at 120 ° C. for 5 to 7 hours with a hot air circulation dryer. . A light guide plate having a wedge-shaped cross-section formed by injection-molding this pellet, having a width of 40 mm, a length of 60 mm, a thin portion of 0.7 mm, and a thick portion of 0.9 mm and having a prism-shaped uneven pattern formed on an inclined surface. Molded. The prism shape was provided by a mold having a pitch of 200 μm and a depth of 5 μm. As an injection molding machine, “Sodick TR100EH” manufactured by Sodick Plustech Co. was used, and molding was performed under conditions of a mold temperature of 80 ° C. and a cylinder temperature of 300 ° C. The injection molding process was performed in a clean room.

  The average luminance and the luminance uniformity were measured for the obtained light guide plate. Furthermore, the total light transmittance was measured with respect to the aromatic polycarbonate resin pellet for light-guide plates. These evaluation results are shown in Tables 2 and 3.

Examples 5-8 and Reference Example 3:
The pellets obtained by blending polycarbonate, stabilizer and brightness improver with the formulation shown in Table 4 and pelletized in the environment shown in Table 1 above were dried at 120 ° C. for 5 to 7 hours with a hot air circulation dryer. . Pellets obtained by the same method as in Example 1 were injection molded to form a light guide plate having a wedge-shaped cross section. The average luminance was measured for the obtained light guide plate. Furthermore, the total light transmittance was measured with respect to the aromatic polycarbonate resin pellet for light-guide plates. These evaluation results are shown in Table 4.

  As is clear from Tables 2 and 3, all of the light guide plates of Examples 1 to 4 in which the dust amount was controlled within the definition of the present invention had a total light transmittance of 90% or more and an average luminance of 1350 or more. , Average brightness exceeding 1,400 can also be achieved. In addition, the brightness uniformity is 80% or more. In Reference Example 1, since the dust amount of the light guide plate is larger than that of the present invention, the average luminance is 1350, but the luminance uniformity is 75%. In Reference Example 2, since the dust amount of the light guide plate is larger than that of the present invention, the average luminance and the luminance uniformity are inferior. The light guide plate of Comparative Example 1 is further inferior in both average luminance and luminance uniformity.

The higher the average luminance of the light guide plate, the better. In the case of the measurement method employed in the examples, the difference in average luminance of 30 cd / cm ² shows a clear difference. Further, in order to improve visibility, it is required that the luminance uniformity is large even at 1%.

  Further, as apparent from Table 4, by using the brightness enhancer together with the dust amount control, the light guide plates of Examples 5 to 8 are greatly improved in both average brightness and brightness uniformity. In Reference Example 3, since the dust amount of the light guide plate is larger than that of the present invention, the average brightness and the brightness uniformity are improved by using the brightness improver, but the degree is compared with Examples 5 to 8. There are few.

Conceptual diagram of a backlight-type surface light source body Conceptual diagram of a front light type surface light source body

Explanation of symbols

1: Light guide plate 2: Light source 3: Liquid crystal display element 4: Reflective member 5: Diffusion sheet 6: Retardation film 11: First surface of light guide plate 12: Second surface of light guide plate

Claims (12)

  The content of dust having a particle size of 0.5 to 1.0 μm is 50,000 / g or less, and the content of dust having a particle size of 1.0 μm or less is 3,000 / g or less. Characteristic aromatic polycarbonate resin pellets for light guide plates.   The aromatic polycarbonate resin pellet for light guide plates according to claim 1, comprising 0.01 to 1 part by weight of a brightness enhancer with respect to 100 parts by weight of the aromatic polycarbonate resin.   The aromatic polycarbonate resin pellet for a light guide plate according to claim 2, wherein the brightness enhancer is at least one selected from the group consisting of polyorganosiloxane, paraffin wax, polyalkylene glycol and fatty acid ester thereof.   The brightness improving agent is a polyorganosiloxane, the polyorganosiloxane has a branched siloxane structure having at least a phenyl group in a side chain, and has a kinematic viscosity at 25 ° C of 1 to 200 cSt. Aromatic polycarbonate resin pellets for light plates. The aromatic polycarbonate resin pellet for a light guide plate according to claim 3 or 4, wherein the brightness enhancer is a polyorganosiloxane represented by the following general formula (1).
  It is formed from an aromatic polycarbonate resin, the content of dust having a particle size of 0.5 to 1.0 μm is 50,000 / g or less, and the content of dust having a particle size exceeding 1.0 μm is 3,000. A light guide plate having a number of pieces / g or less.   The light guide plate according to claim 6, wherein the aromatic polycarbonate resin contains a brightness enhancer.   The light guide plate according to claim 7, wherein the brightness enhancer is at least one selected from the group consisting of polyorganosiloxane, paraffin wax, polyalkylene glycol and fatty acid ester thereof.   The brightness improving agent is a polyorganosiloxane, the polyorganosiloxane has a branched siloxane structure having at least a phenyl group in a side chain, and has a kinematic viscosity at 25 ° C of 1 to 200 cSt. Light board. The light guide plate according to claim 8 or 9, wherein the brightness enhancer is a polyorganosiloxane represented by the following general formula (1).
  The method for producing a light guide plate according to any one of claims 6 to 10, wherein the aromatic polycarbonate resin pellet for a light guide plate according to any one of claims 1 to 5 is formed.   A surface light source body comprising the light guide plate according to claim 6 and a light source.