KR20220002423A - Edge light type light guide plate and edge light type surface light source unit - Google Patents

Abstract

Provided are an edge light type light guide plate that can be easily manufactured because it is excellent in uniformity of luminance and excellent formability in manufacturing a light guide plate by extrusion molding and roll transfer, and an edge light type surface light source unit using the light guide plate.
According to the present invention, there is provided an edge light type light guide plate comprising a styrenic resin composition, having a plurality of lenticular and/or prismatic convex portions on the surface of the light guide plate, the thickness T of the light guide plate being 1.0 to 3.0 mm, The styrenic resin composition contains a styrenic resin, a phosphorus antioxidant (A) and/or a phenolic antioxidant (B), The edge light type light-guide plate which satisfy|fills at least one of following (1) and (2) this is provided
(1) The height H of the convex part is 10-500 μm
(2) Pitch P of the said convex part is 30-800 micrometers

Description

Edge light type light guide plate and edge light type surface light source unit

The present invention relates to an edge light type light guide plate and an edge light type surface light source unit.

The backlight of the liquid crystal display includes a direct type backlight in which a light source is arranged in front of the display device and an edge light type backlight in which a light source is arranged in a side surface of the display device. The light guide plate is included in the edge light type backlight, serves to guide the light from the side to the liquid crystal panel, and is used for a wide range of purposes, such as televisions, desktop PC monitors, laptops, mobile phones, and car navigation. In addition, the backlight using the light guide plate is also used for illumination. For the light guide plate, it has been proposed to use a styrenic resin that has lower water absorption than an acrylic resin typified by PMMA (polymethyl methacrylate), and is less prone to warpage or dimensional change in a molded article (Patent Document 1). Also, it has been proposed to use polystyrene for the light guide plate.

) 등에 의해 패턴을 형성시킬 수 있다. The light guide plate is a member with the function of emitting light by entering the light from the end face (side) of the plate-shaped molded article and guiding the light to the front (light emitting surface) of the molded article by the reflection pattern formed on the rear surface (non-light emitting surface) of the molded article. to be. In recent years, the light guide plate tends to be large and thin, and it has become mainstream in industry to provide a prism pattern or the like on the front surface (light emitting surface) of a plate-shaped molded article in order to increase the uniformity of the emitted light. The pattern on the front or back side of the plate-shaped molded product can be formed during the formation of the plate-shaped molded product, for example, a mold shape in injection molding and roll transfer (

) and the like to form a pattern.

Japanese Patent Laid-Open No. 2003-075648 International Publication No. 2013/094642

However, in a light-guide plate using polystyrene inferior in optical characteristics to an acrylic resin, the moldability of a pattern is a big subject. When providing an uneven pattern on the entire surface (light emitting surface) of the light guide plate, in extrusion molding, the pattern can be formed by roll transfer, but there are problems in molding such as generation of residues and poor transferability and releasability. and it was difficult to easily manufacture a light guide plate providing uniform luminance. On the other hand, when pattern shaping|molding was insufficient, not only an optical characteristic was inferior, but also the subject of becoming a light-guide plate which is low in intensity|strength with thickness reduction and is not enough for practical use existed.

The present invention was implemented in consideration of these problems, and at the same time, it has excellent uniformity in luminance and excellent formability in manufacturing a light guide plate by extrusion molding and roll transfer. It is to provide a light type surface light source unit.

According to the present invention, in the edge light type light guide plate comprising a styrenic resin composition, the light guide plate has a plurality of lenticular and/or prismatic convex portions on the surface of the light guide plate, and the thickness T of the light guide plate is 1.0 to 3.0 mm, The styrene-based resin composition contains a styrene-based resin, a phosphorus-based antioxidant (A) and/or a phenol-based antioxidant (B), and satisfies at least one of the following (1) and (2), An edge light type light guide plate is provided.

(1) The height H of the convex part is 10-500 μm

(2) Pitch P of the said convex part is 30-800 micrometers

The present inventors have intensively studied, in an edge light type light guide plate containing a styrenic resin composition, it has a plurality of lenticular and/or prismatic predetermined pattern convex portions on the surface, and the thickness of the light guide plate is within a predetermined range And, when the styrene-based resin composition contains a specific antioxidant, it has excellent uniformity of luminance and excellent moldability.

Hereinafter, various embodiments of the present invention will be exemplified. Embodiments shown below can be combined with each other.

Preferably, the height H of the convex part is 10-500 μm and the pitch P of the convex part is 30-800 μm.

Preferably, 0.001-0.5 mass part of said phosphorus antioxidant (A) and 0.001-0.5 mass part of said phenolic antioxidant (B) are contained with respect to 100 mass parts of said styrene resin compositions.

Preferably, the phosphorus-based antioxidant (A) is 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, tris(2,4) -di-tert-butylphenyl)phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-dipo Spaspiro[5,5]undecane, tetrakis(2,4-di-tert-butylphenyl)[1,1biphenyl]-4,4-diylbiphosphonite, bis(2,4-di-tert- It is at least 1 sort(s) chosen from butyl-6-methylphenyl)ethyl phosphite.

Preferably, the phenolic antioxidant (B) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert- Butyldibenzo[d,f][1,3,2]dioxaphospepine, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylenebis(oxy Ethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxy phenyl) propionate], 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4 and at least one selected from 8,10-tetraoxaspiro[5,5]undecane.

Preferably, the weight average molecular weight (Mw) of the styrene-based resin is 200,000 to 400,000, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.0 to 3.0.

Preferably, the average transmittance of the styrene-based resin composition at a wavelength of 380 to 780 nm in an initial optical path length of 115 mm is 80% or more.

According to another aspect of the present invention, there is provided an edge light type surface light source unit having the edge light type light guide plate and a light source for supplying light to an end surface of the edge light type light guide plate.

1 is a perspective view schematically showing a light guide plate of the present invention. Fig. 1A is a perspective view of the convex part having a lenticular shape, and Fig. 1B is a perspective view showing the convex part having a prism shape.
2 is a cross-sectional view of the light guide plate of the present invention. Fig. 2A is a cross-sectional view of the convex part having a lenticular shape, and Fig. 2B is a cross-sectional view showing the convex part having a prism shape.
3 is a schematic diagram showing an example of a method for manufacturing a light guide plate of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described. Various characteristics exemplified in the embodiments shown below can be combined with each other. In addition, the invention is established independently for each characteristic.

1. Edge light type light guide plate

[Shape of light guide plate]

(iron part)

The edge light type light guide plate of the present invention has an uneven shape on the surface of the light guide plate. More specifically, as shown in Fig. 1, the light guide plate 1 has a plurality of lenticular (Fig. 1A) and/or prismatic (Fig. 1B) convex portions 3 on its surface. The convex portion is preferably provided on at least one surface of the light guide plate, and in particular needs to be provided on one surface that is the front surface (light emitting surface) of the light guide plate. Although you may provide also about another surface if necessary, it is more preferable to provide only on the front surface (light-emitting surface) of a light-guide plate.

)로 되어 있다(도2A). 또한, 프리즘 형상은, 도1B에 나타내는 바와 같은 원호 형상의 철부(3B)이고 단면의 가장자리 형상이 삼각 산형의 돌조체로 되어 있다(도2B). 또한, 철부는 복수의 조(

)가 서로 평행 관계로 되도록 형성되어 있다(도1). 또한, 철부는 도광판에 일체적으로 형성되어 있는 것이 바람직하다. Here, the lenticular-shaped convex part is an arc-shaped convex part 3A as shown in Fig. 1A, and the edge shape of the cross section is an arc-shaped protrusion (

) (Fig. 2A). Further, the prism shape is an arc-shaped convex portion 3B as shown in Fig. 1B, and the edge shape of the cross section is a triangular ridge protrusion (Fig. 2B). In addition, the iron part has a plurality of sets (

) are formed in a parallel relationship with each other (FIG. 1). Moreover, it is preferable that the convex part is integrally formed with the light guide plate.

Although it will not restrict|limit if the some convex part on the surface of a light-guide plate is formed in multiple numbers, Preferably, it is a periodic pattern.

The pitch P of the convex portion is preferably 30 to 800 μm, more preferably 100 to 600 μm, and still more preferably 200 to 400 μm. If it is within this range, it is easy to manufacture a light guide plate of sufficient strength with excellent extrusion stability, roll transferability and roll releasability in molding a styrene-based resin composition to which an antioxidant is added. Specifically, the pitch P of the convex portion is, for example, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700 , 750 or 800 µm, and may be within a range between any two numerical values exemplified herein. Here, the pitch P of the convex portions is the average value of the distances between the vertices of the adjacent convex portions, as shown in Fig. 2 . In a specific example, it is an average value of the distances between the vertices of adjacent convex parts in 100 continuous convex parts in an arbitrary range.

The height H of the convex portion is preferably 10 to 500 μm, more preferably 50 to 300 μm, and still more preferably 90 to 200 μm. If it is within this range, it is easy to manufacture a light guide plate of sufficient strength with excellent extrusion stability, roll transferability and roll releasability in molding of a styrene-based resin composition to which an antioxidant is added. Specifically, the height H of the convex portion is, for example, 10, 20, 21, 25, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500 μm. and may be within the range between any two numerical values exemplified here. Here, the height H of the convex portion is the average value of the difference between the lowest portion and the highest portion of the convex portion, as shown in Fig. 2 . In a specific example, it is an average value of the difference between the lowest part and the highest part of a convex part in 100 continuous convex parts in an arbitrary range.

The width W of the convex portion is preferably 30 to 800 μm, more preferably 100 to 600 μm, and still more preferably 200 to 400 μm. If it is within this range, it is easy to manufacture a light guide plate of sufficient strength with excellent extrusion stability, roll transferability and roll releasability in molding of a styrene-based resin composition to which an antioxidant is added. Specifically, the width W of the convex portion is, for example, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700 , 750, 800 μm, and may be within a range between any two values exemplified herein. Here, the width W of the convex portions is an average value of the distances between the lowest portions of the convex portions, as shown in Fig. 2 . In a specific example, in 100 consecutive convex parts in an arbitrary range, it is an average value of the distance between the lowest site|part of a convex part.

The ratio (H/P) of the height H of the convex portion to the pitch P is preferably 0.1 to 1.0, more preferably 0.26 to 0.7, and still more preferably 0.3 to 0.5. If it is within this range, it is easy to manufacture a light guide plate of sufficient strength with excellent extrusion stability, roll transferability and roll releasability in molding of a styrene-based resin composition to which an antioxidant is added. Specifically, the ratio (H/P) is, for example, 0.10, 0.15, 0.20, 0.25, 0.26, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.66, 0.67 , 0.68, 0.70, and may be within a range between any two numbers exemplified herein.

(thickness)

The thickness T of the light guide plate is 1.0 to 3.0 mm, preferably 1.5 to 2.5 mm, and more preferably 1.6 to 2.4 mm. If it is within this range, it is easy to manufacture a light guide plate having sufficient strength due to excellent extrusion stability, roll transferability and roll releasability in molding of a styrene-based resin composition to which an antioxidant is added. The thickness T of the light guide plate is specifically, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9. , 3.0 mm, and may be within a range between any two numerical values exemplified herein.

[Styrenic resin composition]

The edge light type light guide plate of the present invention is an edge light type light guide plate containing a styrene-based resin composition. That is, it is a molded article which consists of a styrene resin composition.

The styrene-based resin composition contains a styrene-based resin and a phosphorus antioxidant (A) and/or a phenol-based antioxidant (B).

(Styrenic resin)

The styrenic resin can be obtained by polymerizing a styrenic monomer. The styrene-based monomer is an aromatic vinyl-based monomer, such as styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene, m-methyl styrene, ethyl styrene, and pt-butyl styrene, alone or a mixture of two or more, preferably It is styrene. Moreover, you may copolymerize with monomers other than a styrenic monomer in the range which does not impair the characteristics of this invention, Acrylonitrile, Acrylonitrile, such as acrylic acid, methacrylic acid, butyl acrylate, ethyl acrylate, methyl acrylate, methyl methacrylate. and vinyl cyanide monomers such as methacrylonitrile, α,β-ethylenically unsaturated carboxylic acids such as maleic anhydride and fumaric acid, and imide-based monomers such as phenyl maleimide and cyclohexyl maleimide. The styrenic resin is preferably substantially composed of only styrenic monomers and more preferably a homopolymer of styrenic monomers.

The styrenic resin composition is preferably composed of a styrene resin and various additives, and contains, for example, 90 to 99.998 parts by mass and 95 to 99.98 parts by mass of the styrene resin to 100 parts by mass of the styrene resin composition. desirable. Specifically, the ratio of the styrene-based resin is, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5 with respect to 100 parts by mass of the styrene-based resin composition. , 99.6, 99.7, 99.8, 99.85, 99.88, 99.9, 99.98, 99.998 parts by mass, and may be within the range between any two numerical values exemplified herein.

As a polymerization method of a styrene resin, well-known styrene polymerization methods, such as a block polymerization method, the solution polymerization method, the suspension polymerization method, the emulsion polymerization method, are mentioned. In terms of quality and productivity, bulk polymerization and solution polymerization are preferable, and continuous polymerization is preferable. As the solvent, for example, alkyl benzenes such as benzene, toluene, ethyl benzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used.

In polymerization of the styrene-based resin, a polymerization initiator or a chain transfer agent may be used as needed. As a polymerization initiator, a radical polymerization initiator is preferable, and a well-known and usual example is 1, 1- di (t-butylperoxy) cyclohexane, 2, 2- di (t- butyl peroxy) butane, 2, 2-di Peroxyketals such as (4,4-di-t-butylperoxycyclohexyl)propane and 1,1-di(t-amylperoxy)cyclohexane, cumene hydroperoxide, t-butyl hydroperoxide, etc. of hydroperoxides, t-butylperoxy acetate, alkyl peroxides such as t-amylperoxyisononanoate, t-butylcumylperoxide, di-t-butylperoxide, dicumylperoxide, di-t -Dialkyl peroxides such as hexyl peroxide, peroxy esters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropylmonocarbonate, t-butylperoxyiso Peroxy carbonates such as propyl carbonate and polyether tetrakis (t-butylperoxy carbonate), N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methyl) butyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), N,N'-azobis[2-(hydroxymethyl)propionitrile], and these It can be used 1 type or in combination of 2 or more types. Examples of the chain transfer agent include aliphatic mercaptan, aromatic mercaptan, pentaphenylethane, α-methyl styrene dimer and terpinolene.

4-t-butyl catechol (TBC) is often used as a polymerization inhibitor of a styrenic monomer used for polymerization of a styrenic resin, and a small amount of 4-t-butyl catechol remains in the styrenic resin composition. have. Since 4-t-butyl catechol itself becomes a coloring component and reduces color and transmittance, it is preferable not to contain 4-t-butyl catechol as much as possible in the styrene-based resin composition, but it is difficult to completely remove it. A preferable range of 4-t-butyl catechol is 0.001 to 10 µg/g, more preferably 0.01 to 8 µg/g, and particularly preferably 0.1 to 6 µg/g.

In the case of continuous polymerization, the polymerization reaction is first controlled by adjusting the polymerization temperature so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate using a known complete mixing tank type stirring tank or tower type reactor in the polymerization process. The polymerization solution containing the polymer after the polymerization process is transferred to the devolatilization process to remove unreacted monomers and polymerization solvent. The devolatilization process consists of a vacuum devolatilization tank equipped with a heater, a devolatilization extruder equipped with a vent, etc. After the devolatilization process, the molten polymer is transferred to the granulation process. In the granulation process, the molten resin is extruded in a strand shape from a perforated die and processed into pellets by a cold cut method, an air hot cut method, or an underwater hot cut method.

The weight average molecular weight (Mw) of the styrene-based resin is preferably 200,000 to 400,000, more preferably 220,000 to 380,000, and more preferably 250,000 to 300,000. By setting it as such a range, moldability and the intensity|strength of a light-guide plate are compatible. When it is less than 200,000, the strength of the molded article becomes insufficient, and when it exceeds 400,000, the moldability deteriorates remarkably. Specifically, the weight average molecular weight (Mw) of the styrene-based resin is, for example, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,000, 390,000, and 400,000, and may be within a range between any two numerical values exemplified herein. The weight average molecular weight of the styrenic resin can be controlled by the reaction temperature, residence time, type and amount of polymerization initiator, type and amount of chain transfer agent, type and amount of solvent used during polymerization of the polymerization process.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrenic resin is preferably 1.0 to 3.0, more preferably 1.2 to 2.8, and more preferably 1.5 to 2.5. If it is within this range, it is easy to manufacture a light guide plate having sufficient strength due to excellent extrusion stability, roll transferability, and roll releasability in molding of a styrene-based resin composition to which an antioxidant is added. Specifically, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene-based resin is, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 , 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, and may be within a range between any two numerical values exemplified herein. The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene-based resin is the reaction temperature of the polymerization process, residence time, type and amount of polymerization initiator, type and amount of chain transfer agent added, and polymerization time. It can be controlled by the type and amount of the solvent used for

(phosphorus antioxidant (A) / phenolic antioxidant (B))

The styrene-based resin composition may contain either the phosphorus-based antioxidant (A) or the phenol-based antioxidant (B), but higher moldability and strength can be obtained by using both of them together.

It is preferable to contain 0.001-0.5 mass part with respect to 100 mass parts of styrene resin compositions, as for a phosphorus antioxidant (A), it is more preferable to contain 0.01-0.4 mass part, It is more preferable to contain 0.05-0.3 mass part. Moreover, it is preferable to contain 0.001-0.5 mass part with respect to 100 mass parts of styrenic resin compositions, as for a phenolic antioxidant (B), it is more preferable to contain 0.01-0.3 mass part, It is more preferable to contain 0.05-0.2 mass part. do. If it is in such a range, it is excellent in a moldability and intensity|strength. The content of the phosphorus antioxidant (A) and the phenol antioxidant (B) with respect to 100 parts by mass of the styrene resin composition is specifically, for example, 0.001, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, respectively. , 0.08, 0.09, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50 parts by mass, and may be within a range between any two numerical values exemplified herein.

Phosphorus antioxidant (A) is, for example, 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, tris(2,4-di -tert-butylphenyl)phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro (Diphosphaspiro) [5, 5] undecane, tetrakis (2,4-di-tert-butylphenyl) [1, 1-biphenyl] -4, 4-diylbiphosphonite, bis (2,4- It is at least 1 sort(s) selected from di-tert- butyl-6-methylphenyl) ethyl phosphorous acid ester.

The phenolic antioxidant (B) is, for example, 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldi Benzo[d,f][1,3,2]dioxaphospepine, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylenebis(oxyethylene) Bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8 , at least one selected from 10-tetraoxaspiro[5,5]undecane.

6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1, 3,2] With respect to a compound having both a phosphite structure and a phenolic structure in the same molecule, such as dioxaphospepine (for example, manufactured by Sumitomo Chemical Co., Ltd., SUMILIZER GP), phosphorus oxidation with respect to the styrene-based resin composition It is believed to contain antioxidants and phenolic antioxidants, respectively. For example, when 0.1 mass part of phosphorus-phenolic compounds are contained, it is considered that 0.1 mass parts of phosphorus antioxidants and 0.1 mass parts of phenolic antioxidants are contained with respect to 100 mass parts of styrene resin compositions.

As a method of adding the phosphorus antioxidant (A), phenolic antioxidant (B) and other additives, a method of adding and mixing a styrene-based resin polymerization step, a devolatilization step, and a granulation step, or an extruder during molding processing A method of adding and mixing with an injection molding machine, etc., a method of diluting and mixing a resin composition prepared with high concentrations of phosphorus antioxidant (A) and phenolic antioxidant (B) to a desired content with an additive-free styrene resin, etc. are mentioned. It is not specifically limited.

(Other additives)

The styrene-based resin composition may contain sulfur-based antioxidants, lactone-based antioxidants, ultraviolet absorbers, hindered amine-based stabilizers, antistatic agents, hydrophilic additives, liquid paraffin (mineral oil), polyethylene wax, It may contain various additives such as microcrystalline wax and blueing agent.

The styrenic resin composition contains, as an additive, a higher fatty acid such as lauric acid, myristic acid, palmitic acid, and stearic acid, a higher fatty acid such as stearic acid amide, erucic acid amide, and ethylenebis stearic acid amide, as long as the effects of the present invention are not impaired. Although mold release agents, such as higher alcohols, such as amide, myristyl alcohol, cetyl alcohol, and stearyl alcohol, may be included, it is preferable not to contain more than necessary because the transmittance|permeability may deteriorate. As content of a mold release agent, Preferably it is 500 ppm or less in a styrene resin composition, More preferably, it is 200 ppm or less, More preferably, it is 100 ppm or less. From a viewpoint of obtaining a high transmittance|permeability, it is preferable that a styrenic resin composition does not contain a mold release agent substantially.

It is preferable that it is 95-104 degreeC, and, as for the Vicat softening temperature of a styrene resin composition, it is more preferable that it is 97-104 degreeC. If the Vicat softening temperature is less than 95°C, heat resistance is insufficient, and the light guide plate may be deformed depending on the use environment.

The haze of the styrene-based resin composition is preferably 5% or less in a molded article having a thickness of 4 mm, and more preferably 1% or less.

The average transmittance of the styrene-based resin composition at a wavelength of 380 to 780 nm in the initial optical path length of 115 mm is preferably 80% or more, more preferably 84% or more.

The average transmittance at a wavelength of 380 to 780 nm in an optical path length of 115 mm after the long-term durability test of the styrenic resin composition is preferably 80% or more, more preferably 83% or more.

The initial YI value of the styrenic resin composition is preferably 7.0 or less, and more preferably 6.0 or less.

The difference (ΔYI) between the initial YI value and the YI value after the long-term durability test is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less.

The total light transmittance and YI value were measured as follows. Injection molding was performed at a cylinder temperature of 230°C and a mold temperature of 50°C using pellets of the styrene-based resin composition, and a plate-shaped molded article having a thickness of 127×127×3 mm was molded. Here, the sample for evaluating the durability of the long term (the sample after the long-term durability test) was stored in an oven at 80°C for 1000 hours. Next, a 115x85x3mm-thick test piece was cut out from a plate-shaped molded article, the cross section was grind|polished by buff grinding, and the plate-shaped molded article which has a mirror surface in the cross section was created. The plate-shaped molded article after polishing was measured using an ultraviolet visible spectrophotometer V-670 manufactured by Nippon Bunko Co., Ltd. for incident light having a size of 20 x 1.6 mm and a diffusion angle of 0°, and a wavelength of 350 nm to 800 nm at an optical path length of 115 mm. The spectral transmittance of was measured, and the YI value in the field of view of 2 degrees in C light source was computed according to JISK7105. In addition, the average transmittance|permeability of wavelength 380nm - 780nm is total light transmittance.

[Method for manufacturing light guide plate]

)을 구비하는 연속 시트 압출 성형법을 들 수 있고, 해당 전사형의 형상을 변경함으로써, 시트 표면에 임의의 요철 형상을 전사할 수 있다. The edge light type light guide plate of the present invention can be obtained by molding the styrene-based resin composition, and as a molding method, well-known methods such as sheet extrusion molding, injection molding, and compression molding can be used, but productivity and enlargement of the molded product are easy It is preferable that it is continuous sheet extrusion molding provided with the surface shape transfer type|mold from the point which will be performed. As an example of such sheet extrusion molding, an extrusion step of supplying a resin to a feed block in a heat-melted state and continuously producing an extruded sheet from a die, a pressing step of sandwiching the resin sheet with a pressing roll and a cooling roll, the above After the pressing step, there is a conveying step of conveying the resin sheet while closely adhering to the cooling roll, and a transfer type (

), and by changing the shape of the transfer die, arbitrary concavo-convex shapes can be transferred to the sheet surface.

In addition, the edge light type light guide plate of the present invention has a concave-convex shape on the front surface (light emitting surface), but reflection processing for diffusely reflecting light is applied to the rear surface. As reflective processing, for example, in addition to silk printing or inkjet printing, a method of imparting dot-shaped irregularities by laser irradiation is exemplified. For dot pattern printing, an ink having fine particles for diffusing light is used. can be used

2. Edge light type surface light source unit

The edge light type surface light source unit of the present invention is an edge light type surface light source unit having an edge light type light guide plate and a light source for supplying light to an end surface of the light guide plate.

The edge light type surface light source unit of the present invention can be preferably used as a surface light source device for a liquid crystal display device.

[Example]

Hereinafter, the present invention will be described in more detail by way of Examples. In addition, these are all exemplary and do not limit the content of the present invention.

(Production of styrene-based resins PS-1 to PS-3)

The first reactor, which is a fully-mixed stirring tank, and the third reactor, which is a plug-flow reactor equipped with a second reactor and a static mixer, were connected in series to constitute a polymerization process, and a styrenic resin was produced under the conditions shown in Table 1. . The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. A raw material solution was prepared with the raw material composition described in Table 1, and the raw material solution was continuously supplied to the first reactor at the flow rate indicated in Table 1. The polymerization initiator was added to the raw material solution at the inlet of the first reactor so as to have the concentration to be added (concentration based on mass relative to raw material styrene) shown in Table 1, and mixed uniformly.

The polymerization initiators listed in Table 1 are as follows.

Polymerization initiator-1: 2,2-di(4,4-t-butylperoxycyclohexyl)propane (Nichi Oil Co., Ltd. tank PERTETRA A was used.)

Polymerization initiator-2: 1,1-di(t-butylperoxy)cyclohexane (Nichiyu Co., Ltd. tank PERHECA C was used.)

On the other hand, in the third reactor, a temperature gradient was created according to the flow direction, and the temperature in Table 1 was adjusted in the middle part and the outlet part.

Next, the solution containing the polymer continuously taken out from the third reactor was introduced into a vacuum devolatilization tank equipped with a preheater composed of two stages in series, and the temperature of the preheater was adjusted so as to reach the resin temperature shown in Table 1, Table 1 After separating unreacted styrene and ethylbenzene by adjusting the pressure as described in , it was extruded into a strand shape from a perforated die, and the strands were cooled and cut by a cold cut method to form pellets.

Melt flow rate (MFR) was measured according to JIS K 7210 under conditions of a temperature of 200 ° C. and a load of 49 N, and the Vicat softening temperature was measured according to JIS K 7206 at a temperature increase rate of 50 ° C./hr and a test load of 50 N.

The weight average molecular weight (Mw), the Z average molecular weight (Mz), and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) under the following conditions.

GPC model: Shodex GPC-101, manufactured by Showa Denko Co., Ltd.

Column: PLgel 10 μm MIXED-B manufactured by Polymer Laboratories

Mobile phase: tetrahydrofuran

Sample concentration: 0.2% by mass

Temperature: Oven 40℃, Inlet 35℃, Detector 35℃

Detector: Differential Refractometer

Molecular weight computed the molecular weight in each elution time from the elution curve of monodisperse polystyrene, and computed it as polystyrene conversion molecular weight.

[Examples 1 to 19, Comparative Examples 1 to 7]

<Preparation of resin composition>

Styrenic resins PS-1, PS-2, PS-3 and phosphorus antioxidant (A) and/or phenolic antioxidant (B) at the content shown in Tables 2 and 3 were mixed using a single screw extruder having a screw diameter of 40 mm. The pellet was obtained by melt-kneading at a cylinder temperature of 230°C and a screw rotation speed of 100 rpm.

In addition, about the phosphorus antioxidant (A) and phenolic antioxidant (B) in Tables 2 and 3, respectively, it is as follows.

(phosphorus antioxidant (A))

HP-10: 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus (ADEKA STAB HP-10 manufactured by ADEKA Corporation)

168: tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168 manufactured by BASF JAPAN Co., Ltd.)

PEP-36: 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5] Undecane (ADEKA STAB PEP-36 manufactured by ADEKA Corporation)

P-EPQ: tetrakis (2,4-di-tert-butylphenyl) [1,1 biphenyl] -4,4-diyl biphosphonite (Hostanox P-EPQ manufactured by CLARIANT Co. Ltd.)

38: bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite (Irgafos 38 manufactured by BASF JAPAN Co., Ltd.)

(Phenolic antioxidant (B))

GP: 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d, f][1, 3,2] Dioxaphospepine (Sumitomo Chemical Co., Ltd. SUMILIZER GP)

1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (Irganox 1076 manufactured by BASF JAPAN Co., Ltd.)

245: ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] (Irganox 245 manufactured by BASF JAPAN Co., Ltd.)

1010: pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010 manufactured by BASF JAPAN Co., Ltd.)

AO80: 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10- Tetraoxaspiro [5.5] undecane (ADEKA STBA AO-80 manufactured by ADEKA Corporation)

<Evaluation of optical properties of resin composition>

Injection molding was performed using the obtained pellets at a cylinder temperature of 230°C and a mold temperature of 50°C to form a plate-shaped molded article having a thickness of 127×127×3 mm. In order to evaluate long-term durability, the obtained molded article was stored in an oven at 80 degreeC for 1000 hours. In order to evaluate the optical properties of the initial molded article before storage (initial sample) and the molded article after storage (sample after long-term durability test), a 115 × 85 × 3 mm thick specimen was cut out of a plate-shaped molded article and the cross-section was buffed. It grinded and created the plate-shaped molded article which has a mirror surface in the cross section. For the plate-shaped molded article after polishing, using an ultraviolet visible spectrophotometer V-670 manufactured by Nippon Bunko Co., Ltd., in incident light with a size of 20 x 1.6 mm and a diffusion angle of 0°, a wavelength of 350 nm to an optical path length of 115 mm The spectral transmittance of 800 nm was measured, and the YI value in the field of view of 2 degrees in C light source was computed according to JISK7105. The total light transmittance shown in Table 2 and Table 3 shows the average transmittance|permeability of wavelength 380nm - 780nm.

<Manufacture of light guide plate>

As shown in Fig. 3, the obtained pellets are fed to a single screw extruder 5 with a screw diameter of 120 mm and L/D = 32, and the cylinder temperature is set at 150 to 230 ° C. and melt-kneaded, followed by a gear pump 7 The sheet was extruded by discharging from a T-die 9 having a width of 1500 mm at a resin temperature of 260° C. Next, the extruded sheet is sandwiched between the compression roll 11 (mirror surface cooling roll) and the first cooling roll 13 (mirror surface cooling roll) and conveyed in a state wrapped around the first cooling roll 13, and then The resin sheet peeled from the second cooling roll 15 after being sandwiched by the first cooling roll 13 and the second cooling roll 15 (transfer-type mounting roll) and transferring the concave-convex shape to one surface of the resin sheet It took up with the take-up roll 17 at the take-up speed of 5.2 m/min. On the other hand, the compression roll 11, the 1st cooling roll 13, and the 2nd cooling roll 15 are chrome-plated, and the temperature of each roll is the compression roll 11/1st cooling roll 13/ It was set to 2nd cooling roll 15 =80 degreeC/85 degreeC/90 degreeC. Further, by changing the shape of the transfer die attached to the second cooling roll 15, a resin sheet having a surface convex shape shown in Tables 2 and 3 was obtained.

Meanwhile, in Tables 2 and 3, "shape", "height P", "pitch P", and "H/P" are the values defined as described above, respectively, and "lenti" represents "lenticular".

<Evaluation of formability and strength of light guide plate>

The extrusion stability (residue), roll transferability, roll releasability, and strength of the light guide plate in Table 2 and Table 3 were evaluated as follows.

(Extrusion stability (residue))

The resin temperature of die|dye was adjusted to 300 degreeC, and the following reference|standard evaluated the residue generation|occurrence|production situation in die|dye vicinity.

(circle): Residue is not recognized even if 30 minutes pass after the start of sheet extrusion.

(triangle|delta): Residue is confirmed in 10 to 30 minutes after the start of sheet extrusion.

x: Residue is confirmed within 10 minutes after starting sheet extrusion.

On the other hand, "residue" is a brown or black resin deterioration that occurs around the exit nozzle of the die, and generally increases with the extrusion amount, and when it exceeds a predetermined amount, it detaches from the nozzle and adheres to the sheet surface.

(Roll transferability)

The roll transfer rate T was calculated|required by the following formula, and roll transferability was evaluated by setting the roll transfer rate T to 95% or more as ○, 85 to 95% as △, and 85% or less as ×.

Roll transfer rate T (%) = Height of convex part of resin sheet H / Depth of groove part of transfer type H' x 100

(Roll Releasability)

The resin temperature of the die was adjusted to 270°C and 290°C, and continuous extrusion was performed at each temperature for 30 minutes, and then the appearance of the sheet surface was observed. Roll with no change in appearance at 290°C as ○, roughness or whitening on the sheet surface at 290°C and no change in appearance at 270°C as △, and roughness or whitening on the sheet surface at 270°C as ×. The releasability was evaluated.

(robbery)

A 200 mm x 200 mm test piece was cut out from the resin sheet obtained above, and the 50% fracture height was measured in accordance with JIS K-7211 using a ball weighing 16.6 g. The strength of the light-guide plate was measured with a 50% fracture height of 50 cm or more as (circle), a thing of 30-50 cm as (triangle|delta), and a thing of 30 cm or less as x.

1: light guide plate, 3A: convex part (lenticular shape), 3B: convex part (prism shape), 5: single screw extruder, 7: gear pump, 9: T-die, 11: compression roll, 13: first cooling roll, 15: second 2 cooling rolls, 17: take-up rolls

Claims (8)

An edge light type light guide plate comprising a styrene-based resin composition, comprising:
Having a plurality of lenticular and/or prism-shaped convex portions on the surface of the light guide plate,
The thickness T of the light guide plate is 1.0 to 3.0 mm,
The styrene-based resin composition contains a styrene-based resin, a phosphorus-based antioxidant (A) and/or a phenol-based antioxidant (B),
An edge light type light guide plate satisfying at least one of the following (1) and (2).
(1) The height H of the convex part is 10-500 μm
(2) Pitch P of the said convex part is 30-800 micrometers According to claim 1,
A height H of the convex portion is 10 to 500 μm and a pitch P of the convex portion is 30 to 800 μm, an edge light type light guide plate. 3. The method of claim 1 or 2,
The edge light type light-guide plate containing 0.001-0.5 mass parts of said phosphorus antioxidant (A) and 0.001-0.5 mass parts of said phenolic antioxidant (B) with respect to 100 mass parts of said styrene resin compositions. 4. The method according to any one of claims 1 to 3,
The phosphorus antioxidant (A) is 2,2'-methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, tris(2,4-di-tert) -Butylphenyl)phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5 ,5] Undecane, tetrakis(2,4-di-tert-butylphenyl)[1,1biphenyl]-4,4-diylbiphosphonite, bis(2,4-di-tert-butyl-6- The edge light type light guide plate which is at least 1 sort(s) selected from methylphenyl)ethyl phosphite. 5. The method according to any one of claims 1 to 4,
The phenolic antioxidant (B) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[ d,f][1,3,2]dioxaphospepine, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylenebis(oxyethylene)bis[ 3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propio nate], 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10 - At least one selected from tetraoxaspiro [5, 5] undecane, an edge light type light guide plate. 6. The method according to any one of claims 1 to 5,
The weight average molecular weight (Mw) of the styrene-based resin is 200,000 to 400,000, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.0 to 3.0, an edge light type light guide plate. 7. The method according to any one of claims 1 to 6,
An edge light type light guide plate having an average transmittance of 80% or more at a wavelength of 380 to 780 nm in an initial optical path length of 115 mm of the styrene-based resin composition. An edge light type surface light source unit comprising the edge light type light guide plate according to any one of claims 1 to 7 and a light source for supplying light to an end surface of the edge light type light guide plate.

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