KR20220118526A - Light diffuser plate and direct surface light source unit - Google Patents

Abstract

Provided is a light diffusing plate comprising a styrene-based resin composition, the light diffusing plate having excellent long-term durability and strength.
According to the present invention, there is provided a light diffusing plate containing a styrenic resin composition, wherein the styrenic resin composition contains a styrenic resin (A), an antioxidant (B) and a light diffusing agent (C), and the antioxidant ( B) contains at least 1 sort(s) of a phosphorus antioxidant (B-1), a phenolic antioxidant (B-2), and a phosphorus-phenolic antioxidant (B-3), 100 mass parts of said styrene resins 0.001 to 0.5 mass parts in total of the said phosphorus antioxidant (B-1) and the said phosphorus phenolic antioxidant (B-3) with respect to the said phenolic antioxidant (B-2) and the said phosphorus phenolic antioxidant 0.001 to 0.5 parts by mass of antioxidant (B-3) in total, 0.1 to 10 parts by mass of the light diffusing agent (C), and a content of t-butylcatechol contained in the styrenic resin composition is 0.1 A light diffuser plate of ˜10 μg/g is provided.

Description

Light diffuser plate and direct surface light source unit

The present invention relates to a light diffusion plate and a direct-type surface light source unit.

The light diffusing plate is used for direct type liquid crystal display devices and the like. The direct liquid crystal display device is a display device including a liquid crystal cell and a backlight device disposed directly under it, and an LED is used as a light source for the backlight device, and a light diffuser plate disposed on the front side thereof is used. And a styrenic resin composition may be used as resin which comprises a light-diffusion plate (patent document 1).

Japanese Patent Laid-Open No. 2010-134461

However, the LED used as a light source has been increased in output to meet the increase in luminance, and due to an increase in the amount of heat generated, the long-term durability of the conventional light diffusion plate made of a styrene-based resin composition is insufficient. There are also cases where the strength does not meet the needs.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a light diffusing plate comprising a styrene-based resin composition, the light diffusing plate having excellent long-term durability and strength.

According to the present invention, there is provided a light diffusing plate comprising a styrenic resin composition, wherein the styrenic resin composition contains a styrenic resin (A), an antioxidant (B) and a light diffusing agent (C), and the antioxidant ( B) contains at least 1 sort(s) of a phosphorus antioxidant (B-1), a phenolic antioxidant (B-2), and a phosphorus-phenolic antioxidant (B-3), 100 mass parts of said styrene resins 0.001 to 0.5 mass parts in total of the said phosphorus antioxidant (B-1) and the said phosphorus phenolic antioxidant (B-3) with respect to the said phenolic antioxidant (B-2) and the said phosphorus phenolic antioxidant 0.001 to 0.5 parts by mass of antioxidant (B-3) in total, 0.1 to 10 parts by mass of the light diffusing agent (C), and a content of t-butylcatechol contained in the styrenic resin composition is 0.1 to A light diffuser plate of 10 μg/g is provided.

When the present inventors conducted intensive studies, the content of t-butylcatechol, phosphorus antioxidant, phenolic antioxidant, phosphorus/phenolic antioxidant, and light diffusing agent in the styrenic resin composition was within a predetermined range. It was discovered that it was excellent in long-term durability and strength, and it led to the completion of this invention.

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

Preferably, the phosphorus antioxidant (B-1) 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'diylbisphosphonite, bis(2,4 The light-diffusing plate which is at least 1 sort(s) selected from -di-tert-butyl-6-methylphenyl)ethyl phosphite.

Preferably, the phenolic antioxidant (B-2) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra -tert-butyldibenzo[d,f][1,3,2]dioxaphosphepine, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylene Bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-triyl)propionate], pentaerythritol tetrakis[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]- A light diffusing plate which is at least one selected from 2,4,8,10-tetraoxaspiro[5,5]undecane.

Preferably, the phosphorus-phenolic antioxidant (B-3) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10 -Tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphospepine light diffuser plate.

Preferably, the light diffusing agent (C) is at least one selected from crosslinked acrylic polymer particles, crosslinked styrene polymer particles, and crosslinked siloxane polymer particles.

Preferably, the weight average molecular weight (Mw) of the styrene-based resin (A) 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 light diffuser.

Preferably, the light diffusion plate for the LED light source of the light diffusion plate.

Preferably, the direct type surface light source unit having the light diffusion plate.

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

1. light diffuser

A light-diffusing plate according to an embodiment of the present invention is a light-diffusing plate containing a styrene-based resin composition. The thickness of the light diffusing plate is not limited, but is, for example, 1 to 3 mm. Moreover, the ultraviolet-ray absorption layer which mix|blended the ultraviolet-ray absorber and the light stabilizer may be laminated|stacked on the light-diffusion plate.

An antistatic agent may be apply|coated to the surface of the light-diffusion plate which concerns on one Embodiment. By applying the antistatic agent, after the light diffusing plate is attached to the backlight device, adhesion of dust or the like due to static electricity is suppressed, so that it can be used for a long period of time without lowering the luminance. Further, in the light diffusion plate of the present invention, a delicate concave-convex shape such as embossing may be formed on both surfaces or one surface thereof, and a semicircular or elliptical lens shape or a prism shape may be formed on both surfaces or one surface.

<Styrene-based resin composition>

The styrene-based resin composition contains a styrene-based resin (A), an antioxidant (B), and a light-diffusing agent (C). Moreover, content of t-butylcatechol contained in a styrene resin composition is 0.1-10 microgram/g. By setting it as such a range, it is excellent in long-term durability and intensity|strength. Specifically, the content of t-butylcatechol is 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10 μg/g, among the numerical values exemplified here It may be in the range between any two. When the content of t-butylcatechol is less than 0.1 µg/g, the effect of inhibiting oxidative deterioration during thermoforming is small, so the strength of the light-diffusing plate is lowered, and the content of t-butylcatechol is 10 µg When it exceeds /g, t-butylcatechol itself becomes a coloring component, and not only the long-term durability of a light-diffusion plate falls, but also intensity|strength will fall.

<Styrenic resin (A)>

Styrenic resin (A) is resin obtained by superposing|polymerizing a styrenic monomer as a main component, Specifically, it is resin which contains more than 50 % of styrenic monomers. The styrene-based monomer is an aromatic styrene-based monomer, such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, ethylstyrene, and p-t-butylstyrene, alone or as a mixture of two or more, preferably It is styrene. Further, the styrene-based resin (A) may be a copolymer obtained by copolymerizing a monomer copolymerizable with a styrene-based monomer with a styrene-based monomer, and examples of the monomer copolymerizable with the styrene-based monomer include acrylic acid, methacrylic acid, etc. Vinyl cyanide monomers such as acrylic acid monomer, acrylonitrile and methacrylonitrile, acrylic monomers such as butyl acrylate, ethyl acrylate, methyl acrylate, and methyl methacrylate, α,β-ethylenically unsaturated carboxyl such as maleic anhydride and fumaric acid and imide-based monomers such as acids, phenyl maleimide, and cyclohexyl maleimide. These monomers can be used individually by 1 type or in combination of 2 or more types.

The weight average molecular weight (Mw) of a styrene resin (A) becomes like this. Preferably it is 200,000-400,000, More preferably, it is 200,000-290,000. Moreover, ratio (Mw/Mn) of the weight average molecular weight (Mw) and number average molecular weight (Mn) of a styrene resin (A) becomes like this. Preferably it is 1.0-3.0, More preferably, it is 1.5-2.5. Moreover, the ratio (Mz/Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) of the styrene resin (A) is preferably 1.0 to 2.0. By setting it as such a range, the formability and intensity|strength of a light-diffusion plate can be compatible. When a weight average molecular weight (Mw) is 200,000 or more, intensity|strength becomes favorable, and when it is 400,000 or less, a moldability is favorable. In addition, when the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.0 or more, the moldability is good, and when it is 3.0 or less, the strength is good. If the ratio (Mz/Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 1.0 or more, the moldability is good, and if it is 2.0 or less, the strength is good.

<Antioxidant (B)>

Antioxidant (B) contains at least 1 sort(s) of a phosphorus antioxidant (B-1), a phenolic antioxidant (B-2), and a phosphorus-phenolic antioxidant (B-3).

A styrenic resin composition contains 0.001-0.5 mass parts of phosphorus antioxidant (B-1) and a phosphorus phenolic antioxidant (B-3) in total with respect to 100 mass parts of styrene resins, Preferably it is 0.05 It contains -0.3 mass part. By setting it as such a range, a light-diffusion plate is excellent in long-term durability and strength. Specifically, content of the total of phosphorus antioxidant (B-1) and phosphorus phenolic antioxidant (B-3) is 0.001,0.005, 0.01, 0.02, 0.03, 0.04 with respect to 100 mass parts of styrene resins. , 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 parts by mass, and may be within the range between any two of the numerical values exemplified here.

0.001-0.5 mass part of phenolic antioxidant (B-2) and phosphorus-phenolic antioxidant (B-3) are contained in total, Preferably it contains 0.02-0.3 mass part More preferably, 0.05-0.15 mass part contains By setting it as such a range, a light-diffusion plate is excellent in long-term durability and strength. Specifically, the content of the total of the phenol-based antioxidant (B-2) and the phosphorus-phenol-based antioxidant (B-3) is 0.001,0.005, 0.01, 0.02, 0.03, 0.04, with respect to 100 parts by mass of the styrene-based resin; 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 mass parts, and may exist in the range between any two of the numerical values illustrated here.

Phosphorus antioxidant (B-1) is (phosphorous acid ester) which does not have a phenolic hydroxyl group in basic skeleton, Preferably they are phosphorous acid esters which are trivalent phosphorus compounds. Phosphorus antioxidant (B-1) 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[5,5]undecane, tetrakis(2,4-di-tert-butylphenyl)[1,1biphenyl]-4,4'diylbisphosphonite, bis(2,4 -di-tert-butyl-6-methylphenyl) at least 1 sort(s) chosen from ethyl phosphite etc.

A phenolic antioxidant (B-2) is antioxidant which has a phenolic hydroxyl group in basic skeleton and is not (phosphoric acid ester). The phenolic antioxidant (B-2) is, for example, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylenebis(oxyethylene)bis[3 -(5-tert)-butyl-4-hydroxy-m-triyl)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 - It is at least 1 sort(s) selected from tetraoxaspiro [5,5] undecane, etc.

The phosphorus-phenolic antioxidant (B-3) is a (phosphorous acid ester) having a phenolic hydroxyl group in the basic skeleton, and is preferably a phosphorous acid ester, which is a trivalent phosphorus compound having a phenolic hydroxyl group in the basic skeleton. Phosphorus-phenolic antioxidant (B-3) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyl dibenzo[d,f][1,3,2]dioxaphospepine, and the like.

<Light diffuser (C)>

A styrenic resin composition contains 0.1-10 mass parts of light-diffusion agents (C) with respect to 100 mass parts of styrene resins, Preferably it contains 0.5-3 mass parts, More preferably, it contains 0.8-1.5 mass parts. contains By setting it as such a range, a light-diffusion plate is excellent in long-term durability and strength. The content of the light-diffusing agent (C) is specifically 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2, 3, 4, 5, It is 6, 7, 8, 9, 10 mass parts, and the range between any two of the numerical values illustrated here may be sufficient.

The light diffusing agent (C) is a particle having a refractive index different from that of the styrenic resin composition and can be used as long as it has an effect of diffusing incident light. Organic particles such as polymer crosslinked particles and inorganic particles such as glass beads, silica particles, aluminum hydroxide particles, calcium carbonate particles, barium sulfate particles, titanium oxide particles and talc can be used. Especially, it is preferable that it is at least 1 sort(s) chosen from acrylic polymer crosslinked particle|grains, styrenic polymer crosslinked particle|grains, and siloxane type polymer crosslinked particle|grains. The average particle diameter of the light-diffusing agent (C) is preferably 1 to 20 µm. When the average particle diameter of a light-diffusion agent (C) is less than 1 micrometer, a hue may deteriorate, and when it exceeds 20 micrometers, provision of light-diffusion property may not be enough.

<Other additives>

Various additives can be mix|blended with a styrenic resin composition as needed in the range which does not impair the characteristic of this invention. The type of additive is not particularly limited as long as it is generally used in plastics, but a flame retardant, a lubricant, a processing aid, an antiblocking agent, an antistatic agent, an antifogging agent, a light resistance improver, a softener, a plasticizer, an inorganic reinforcing agent, a crosslinking agent, a pigment, a dye, etc. mixtures of

2. Styrene-based resin composition and manufacturing method of light diffusing plate

The styrene-based resin composition of the present invention can be produced by adding an antioxidant (B) and a light-diffusing agent (C) to the styrene-based resin (A). The antioxidant (B) and the light-diffusing agent (C) may be added at the time of polymerization of the styrene-based resin (A), and after polymerization of the styrene-based resin (A), the antioxidant (B) and the light-diffusing agent (C) ) may be drive-blended, melt-kneaded with an extruder, and manufactured. In addition, an antioxidant (B) and a light diffusing agent (C) were melt-kneaded in advance with a small amount of a styrene-based resin to prepare a pellet-shaped masterbatch, and dry-blended the styrene-based resin (A) and the masterbatch. Then, you may manufacture by melt-kneading.

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. From the point of quality or productivity, the bulk polymerization method and the solution polymerization method are preferable, and it is preferable that it is continuous polymerization. As the solvent, for example, alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used.

In the case of superposition|polymerization of a styrenic resin (A), polymerization adjuvant, such as a polymerization initiator, a chain transfer agent, and a crosslinking agent, and another polymerization adjuvant can be used as needed. As a polymerization initiator, a radical polymerization initiator is preferable, and a well-known and usual example is given, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2 -Peroxyketals such as di(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-di(t-amylperoxy)cyclohexane, cumene hydroperoxide, t-butyl hydroper Hydroperoxides such as oxide, alkyl peroxides such as t-amylperoxyisononanoate, t-butylcumylperoxide, di-t-butylperoxide, dicumylperoxide, di-t-hexylperoxide, etc. of dialkyl peroxides, peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxyisopropylcarbonate, polyether tetra Peroxycarbonates such as kiss (t-butylperoxycarbonate), N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N ,N'-azobis(2,4-dimethylvaleronitrile), N,N'-azobis[2-(hydroxymethyl)propionitrile], etc. are mentioned, These are 1 type, or 2 or more types. can be used in combination. Examples of the chain transfer agent include aliphatic mercaptan, aromatic mercaptan, pentaphenylethane, α-methylstyrene dimer and terpinolene.

In the case of continuous polymerization, a styrenic resin can be manufactured by the method provided with a polymerization process, a devolatilization process, and a granulation process.

First, in the polymerization step, the polymerization reaction is controlled by adjusting the polymerization temperature or the like so as to achieve the target molecular weight, molecular weight distribution, and reaction conversion using a known complete mixing tank type stirring tank or tower reactor.

The polymerization solution containing the polymer leaving the polymerization process is sent to the devolatilization process, and unreacted monomers and polymerization solvent are removed. The devolatilization process consists of a vacuum devolatilization tank with a heater, a devolatilization extruder with a vent, etc. The polymer in the molten state leaving the devolatilization process is transferred to the granulation process. In the granulation process, the molten resin is extruded from a perforated die into a strand shape, and it is processed into pellets by a cold cut method, an air hot cut method, or an underwater hot cut method.

As for content of t-butylcatechol in a styrene resin composition, adjustment of content in the case of polymerization start of a styrene resin (A), adjustment of content in a subsequent devolatilization process, etc. are possible. Moreover, you may add and adjust before and after adding antioxidant (B), a light-diffusion agent (C), etc. to a styrene resin (A).

The light-diffusing plate can be produced by molding the styrene-based resin composition by various methods such as extrusion molding and injection molding, but is preferably produced by extrusion molding. As an example of extrusion molding, after melt-kneading a styrene resin composition using a single screw extruder or a twin screw extruder, extruding continuously from a T-die, the method of cooling and solidifying with a cooling roll unit is mentioned. When the concave-convex shape is formed on the surface of the light diffusing plate, an arbitrary concavo-convex shape can be formed by providing a transfer die on the surface of the cooling roll and changing the shape of the transfer die. In addition, in the case of laminating the surface layer on both sides and one side of the light diffusing plate, methods such as co-extrusion method, sticking method, thermal bonding method, solvent bonding method, casting method, and surface coating method can be adopted.

3. Other

The light diffusing plate according to an embodiment of the present invention can be used as a light diffusing plate for an LED light source.

Further, a direct type surface light source unit according to an embodiment of the present invention is a direct type surface light source unit having the light diffusion plate.

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 this invention.

1. Measurement method

<Molecular Weight>

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

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

Column: Polymer Laboratories Ltd. PLgel 10㎛ MIXED-B

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 molecular weight in polystyrene conversion.

<Melt mass flow rate (MFR)>

In accordance with JIS K 7210, it was measured under the conditions of a temperature of 200° C. and a load of 49 N.

<Vicat softening temperature>

In accordance with JIS K 7206, it measured at a temperature increase rate of 50° C./hr and a test load of 50 N.

<Content of t-butylcatechol (TBC)>

After dissolving 0.2 g of a styrenic resin in a small amount of THF, 200 μL of BSTFA (M,O-bis(trimethylsilyl)trifluoroacetamide) was added, trimethylsilyl derivatization treatment was performed, and 10 mL of THF was used. The supernatant separated by centrifugation was measured by gas chromatography mass spectrometry (GC/MS) under the following conditions. In addition, the calibration curve prepared in advance was used for determination of a density|concentration.

GC device: Agilent 7890A

Column: DB-5ms made by Agilent (0.25mm i.d.Х30m), liquid film thickness 0.25㎛

Column temperature: 50°C (1min)→(20°C/min temperature rise)→320°C (6.5min) total 20min

Inlet: 300℃, 1.5mL/min, (split ratio 1:5)

Injection volume: 1 μL

MS device: Agilent 5975C

Interface temperature: 320℃

MS detection conditions: SIM measurement TBC (m/z 295 for quantification, m/z 310 for confirmation)

<Total light transmittance, YI>

Based on JIS-K7105, the total light transmittance of the thickness direction of a light-diffusion plate was measured using the Nippon Denshoku Industrial Co., Ltd. product turbidimeter NDH5000.

<YI>

Based on JIS-K7105, YI of the light-diffusing plate was measured by the reflection method using the Nippon Denshoku Industries Co., Ltd. colorimetric colorimeter NDJ4000.

<Average Luminance Difference>

After taking out a liquid crystal panel, various optical films, and a light diffusing plate from a commercially available 20-inch direct-type LED liquid crystal television, the central portion of the light diffusing plate was cut out in a square shape of 115 mmХ 115 mm, and the cut-out portion was placed in Examples and Comparative Examples. An evaluation test piece cut out of the obtained light diffusion plate to 115 mmХ115 mm or an evaluation test piece of 115 mmХ115 mm after an endurance test was mounted, and this was mounted on the frame of the liquid crystal television after taking out. Thereafter, two commercially available light-diffusing films were stacked on the front side of the light-diffusing plate, and one luminance enhancing film (“DBEF” manufactured by 3M) was stacked on the front side of the light-diffusing plate, and the LED was turned on. In , using a multi-point luminance meter, the luminance of each spot (51Х51 = 2601 places) was measured over the entire range of the front surface of the liquid crystal television, and the average value of these luminances was taken as the average luminance (cd/m ² ) . Moreover, the average luminance difference (%) was calculated|required by the following formula.

Average luminance difference (%) = {(Average luminance of Example)-(Average luminance of Comparative Example 1)}/(Average luminance of Comparative Example 1) Х100

<Diffusion rate>

Optech Inc. Using a goniophotometer, the light transmitted from the light source of white light in a direction perpendicular to the surface of the light diffusion plate is set to 0 degrees in the direction perpendicular to the surface of the light diffusion plate, 5 degrees, 20 degrees, 70 degrees The luminance in the figure was measured, and the diffusion rate was calculated|required by the following formula.

Light diffusivity (%) = (luminance of 20 degrees + luminance of 70 degrees) / (luminance of 5 degrees Х2)Х100

<Strength>

The light-diffusing plate was cut out in a square shape to 200 mm Х 200 mm, and it was set as the evaluation test piece. A sphere having a weight of 16.6 g was used, and in accordance with JIS K-7211, the 50% breaking height was measured and evaluated according to the following criteria.

○: 50% fracture height exceeds 40 cm

△: 50% destruction height 20-40 cm

Х: 50% destruction height less than 20cm

2. Endurance test

After the light-diffusing plate was cut out to 115 mmХ115 mm, the evaluation test piece was exposed for 1,000 hours in a tank in which the temperature was set to 80°C using a gear oven HISPEC HT310 manufactured by Kusumoto Chemicals.

About the result of long-term durability, the result of each measurement after the said endurance test is shown.

3. Synthesis of styrenic resin

Styrenic resins PS-1 to PS-5 were synthesized according to each condition in Table 1.

(Synthesis of PS-1)

A polymerization process was constituted by connecting in series the first reactor, the second reactor, and the third reactor, which is a plug flow reactor with a static mixer, which is a complete mixing type stirring tank, and the conditions shown in Table 1 were followed to manufacture a styrenic resin. 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. In the raw material composition shown in Table 1, a raw material solution was prepared, 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 concentrations shown in Table 1 (concentrations based on mass relative to the raw material styrene), and mixed uniformly. The polymerization initiators listed in Table 1 are as follows.

Polymerization initiator-1: 2,2-di(4,4-t-butylperoxycyclohexyl)propane (PERTETRA A manufactured by Nichiyu Corporation was used.)

Polymerization initiator-2: 1,1-di(t-butylperoxy)cyclohexane (PERHEXA C manufactured by Nichiyu Corporation was used.)

In addition, in the third reactor, a temperature gradient was set 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 is introduced into a vacuum devolatilization tank with a preheater configured in two stages in series, and the temperature of the preheater is adjusted so that the resin temperature shown in Table 1 is obtained. After separating unreacted styrene and ethylbenzene by adjusting the pressure, the strands were cooled, cut, and pelletized by extrusion from a perforated die into a strand shape by a cold cut method.

PS-2 to PS-5 were synthesized in the same manner as in PS-1 except that the conditions were changed according to Table 1.

4. Examples and Comparative Examples

By the method shown below, the Example and the comparative example were implemented.

<Example 1>

With respect to 100 parts by mass of the styrene resin (PS-1) containing t-butylcatechol (TBC) in the amount shown in Table 1, 0.2 parts by mass of a phosphorus antioxidant (HP-10) and a phosphorus/phenol antioxidant (GP) 0.1 parts by mass and 1.0 parts by mass of light diffusing agent (MBX-8) were mixed with a blender, using a single screw extruder having a screw diameter of 40 mm, and mixed at a cylinder temperature of 230° C. and a screw rotation speed of 100 rpm to obtain a styrene-based resin composition .

Next, the styrenic resin composition is supplied to an extruder with a single screw vent having a screw diameter of 90 mm and L/D = 32, melt-kneaded at 200 to 235° C., and then in a T-die with a lip width of 1000 mm and a lip opening of 3.0 mm , T-die temperature of 245-250 ° C., and after cooling and solidification with three vertical cooling rolls, the cross section was trimmed to obtain a light diffusion plate having a width of 800 mm and a thickness of 2.0 mm. The initial optical properties of the light diffusing plate were measured based on each measurement method, and the initial intensity was also measured. Next, the above endurance test was performed, and optical properties thereafter were measured based on each measurement method. These results are shown in Table 2.

<Examples 2-15, Comparative Examples 1-7>

Also about Examples 2-15 and Comparative Examples 1-7, except having changed according to the conditions of Table 2 and Table 3, the resin composition and the light-diffusion plate were obtained and measured similarly to Example 1. . The results are shown in Tables 2 and 3.

Each abbreviation in a table|surface is as follows.

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

168: tris (2,4-di-tert-butylphenyl) phosphite (manufactured by BASF Japan; Irgafos 168)

PEP-36: 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (made by ADEKA; PEP-36)

P-EPQ: tetrakis(2,4-di-tert-butylphenyl)[1,1biphenyl]-4,4'diylbisphosphonite (manufactured by BASF Japan; Irgafos P-EPQ)

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

GP: 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1, 3,2] dioxaphospepine (manufactured by Sumitomo Chemical Corporation; SUMILIZER GP)

1076: octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured by BASF Japan; Irganox 1076)

245: ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-triyl)propionate] (manufactured by BASF Japan; Irganox 245)

1010: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (manufactured by BASF Japan; Irganox 1010)

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 (made by ADEKA; AO-80)

MBX-8: acrylic crosslinked particles (average particle size of 8 µm, manufactured by Sekisui Kasei Kogyo Co., Ltd.; MBX-8)

SBX-8: polystyrene-based crosslinked particles (average particle diameter of 8 μm, manufactured by Sekisui Kasei Kogyo Co., Ltd.; SBX-8)

KMP-590: silicone-based crosslinked particles (average particle diameter of 2 μm, manufactured by Shin-Etsu Chemical Co., Ltd.; KMP-590)

Claims (8)

As a light diffusion plate containing a styrene-based resin composition,
The styrene-based resin composition contains a styrene-based resin (A), an antioxidant (B), and a light-diffusing agent (C),
The said antioxidant (B) contains at least 1 sort(s) of a phosphorus antioxidant (B-1), a phenolic antioxidant (B-2), and a phosphorus-phenolic antioxidant (B-3),
With respect to 100 parts by mass of the styrene-based resin,
0.001 to 0.5 parts by mass of the phosphorus-based antioxidant (B-1) and the phosphorus-phenol-based antioxidant (B-3) in total;
0.001 to 0.5 parts by mass of the phenolic antioxidant (B-2) and the phosphorus/phenolic antioxidant (B-3) in total;
0.1 to 10 parts by mass of the light diffusing agent (C),
contains,
A light diffusing plate having a content of t-butylcatechol contained in the styrene-based resin composition of 0.1 to 10 μg/g. The method of claim 1,
The phosphorus-based antioxidant (B-1),
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) [1,1 biphenyl] -4,4'diylbisphosphonite;
The light-diffusion plate which is at least 1 sort(s) selected from bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite. 3. The method of claim 1 or 2,
The phenolic antioxidant (B-2),
6-[3-(3-tert-Butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3, 2] dioxaphosphepine,
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;
ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-triyl)propionate],
pentaerythritol tetrakis [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]-2,4,8,10-tetraoxa The light-diffusing plate which is at least 1 sort(s) selected from spiro[5,5]undecane. 4. The method according to any one of claims 1 to 3,
The phosphorus-phenolic antioxidant (B-3) is 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert- Butyldibenzo[d,f][1,3,2]dioxaphospepinein, light diffuser plate. 5. The method according to any one of claims 1 to 4,
The light-diffusing plate, wherein the light-diffusing agent (C) is at least one selected from cross-linked acrylic polymer particles, cross-linked styrene-based polymer particles, and cross-linked siloxane-based polymer particles. 6. The method according to any one of claims 1 to 5,
The weight average molecular weight (Mw) of the styrene-based resin (A) 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, light diffusion board. 7. The method according to any one of claims 1 to 6,
Light diffuser for LED light source. The direct type surface light source unit which has the light-diffusion plate in any one of Claims 1-7.