KR101653849B1 - Molded object for optical use, and lightguide plate and light diffuser both comprising same - Google Patents

Abstract

Disclosed is an optical molded article having a low hygroscopicity, a small warping and dimensional change, a small loss of light transmittance in a long-wavelength light, and excellent light resistance, and a light guide plate and an optical diffuser using the molded article. According to the present invention, there is provided an optical molded article obtained by molding a styrenic resin obtained by polymerization reaction of a styrenic monomer having a polymerization inhibitor of less than 10 ppm and a phenylacetylene compound of 50 ppm or less, and a light guide plate and a light diffuser using the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a molded article for optical use, and a light guide plate and an optical diffuser using the same,

The present invention relates to an optical molded article, and a light guide plate and an optical diffuser using the same.

BACKGROUND ART [0002] Acrylic resins have excellent transparency and have been widely used as optically molded articles such as light guide plates, diffuser plates, and lenses. Further, in recent years, various styrenic resins have also been proposed and used as optical molding products in place of acrylic resins.

For example, Patent Document 1 proposes a resin molded article composed of a copolymer mainly composed of methyl methacrylate and a styrene monomer, and Patent Document 2 proposes a light guide plate made of a styrene- (meth) acrylic acid ester copolymer resin . In Patent Documents 3 and 4, a resin composition comprising a copolymer containing an aromatic vinyl monomer and a methyl methacrylate monomer has been proposed. Patent Document 5 proposes a multilayer diffuser of a styrene-based polymer or a styrene-based monomer-methyl methacrylate copolymer.

Japanese Patent Application Laid-Open No. 2001-342263 Japanese Patent Application Laid-Open No. 2003-075648 Japanese Patent Laid-Open No. 2006-052349 Japanese Patent Application Laid-Open No. 2006-052350 Japanese Patent Application Laid-Open No. 2007-264598

Acrylic resin is widely used as an optical molding product, but has a problem that warpage and dimensional change are likely to occur because of high hygroscopicity. Further, since the acrylic resin has high thermal decomposability at the time of molding, there is a problem that when the molding is performed at a high temperature, the molded article is liable to cause defective appearance.

In response to these problems, various styrenic resins have been proposed and used as described above, but styrenic resins have lowered transparency and light resistance compared with acrylic resins, and thus their use has been limited.

Particularly, there is a problem in that a styrene resin having a low light transmittance can not be used for a molded article for use in a long optical path length (hereinafter referred to as " long optical path ") in an optical molded article such as a light guide plate of a medium- .

In recent years, with the technological innovation of LEDs as a background, a new optical system suitable for LED light (for example, a fluorescent tube (FL tube), an external electrode tube (EEFL tube) and a cold cathode tube (CCFL tube) A molded article is desired.

An object of the present invention is to provide an optical molded article having low hygroscopicity, low loss of light transmittance in a long-wavelength light path, and excellent light resistance.

It is also an object of the present invention to provide a molded article for optical use useful as a light guide plate for a liquid crystal display, a light guide plate for illumination or various light diffusers, particularly a light guide plate useful as a light guide plate for medium to large- To provide an optical diffuser useful in the present invention.

As a result of intensive studies on the above problems, the present inventors have found that an optical molded article obtained by molding a styrenic resin obtained by polymerizing a styrenic monomer having a small amount of a polymerization inhibitor and a small amount of a phenylacetylene compound has a low hygroscopicity, The present invention has been accomplished on the basis of these findings. The present invention has been accomplished on the basis of these findings.

The optical molded article according to the present invention is an optical molded article obtained by molding a styrene resin obtained by polymerization reaction of a styrenic monomer having a polymerization inhibitor of less than 10 ppm and a phenylacetylene compound of 50 ppm or less.

The molded article for optical use according to the present invention, particularly the light guide plate and light diffuser, has a low hygroscopicity and thus has less warping and dimensional change, less loss of light transmittance in the long-wavelength light path, and good light resistance. In addition, the light diffuser has a good overall light transmittance and diffusivity.

<Explanation of Terms>

In the present specification, the term &quot; to &quot; means &quot; above &quot; and &quot; below &quot;. For example, &quot; A to B &quot; means that A is A or more and B or less.

In the present specification, the term &quot; optical molding article &quot; means used for optical applications such as a light guide plate, a diffusion plate, and a lens.

In the present specification, the (meth) acrylate ester monomer is a general term of an acrylic acid ester monomer and a methacrylate ester monomer.

In the present specification, the term &quot; optical diffuser &quot; means diffusing light to cause surface light emission on a plane or a curved surface, which is typified by a diffusion plate or a diffusion cover.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an optical molded article according to the present invention, particularly a light guide plate and an optical diffuser, will be described in detail.

The optical molded article according to this embodiment is an optical molded article obtained by molding a styrene resin obtained by polymerization reaction of a styrenic monomer having a polymerization inhibitor of less than 10 ppm and a phenylacetylene compound of 50 ppm or less.

The molded article for optical use having the above-described structure has low hygroscopicity and therefore has less warping and dimensional change, less loss of light transmittance in the long-wavelength light path, and good light resistance. In addition, the light diffuser has a good overall light transmittance and diffusivity.

[Styrene-based resin]

The styrene-based resin is a polymer obtained by polymerizing a styrene-based monomer.

Examples of the styrene-based monomer include styrene,? -Methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene and p-t-butylstyrene. These styrene-based monomers may be used singly or in combination of two or more.

The styrene-based resin may be a copolymer of a styrene-based monomer and a monomer copolymerizable with a styrene-based monomer, or a styrene- (meth) acrylate-based copolymer obtained by copolymerizing a styrene-based monomer and a (meth) desirable.

The styrene-based resin is a styrene- (meth) acrylate-based copolymer, whereby an effect that the light resistance is good can be obtained.

Examples of the (meth) acrylic acid ester monomer include methacrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) Acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate. Of these, methyl methacrylate is particularly preferable. These (meth) acrylic acid ester-based monomers may be used singly or as a mixture of two or more thereof.

The ratio of the styrene-based monomer units in the styrene-based resin is 3% by mass or more, preferably 6% by mass to 90% by mass, and more preferably 10% by mass to 60% by mass.

When the ratio of the styrene monomer unit is 3 mass% or more, the hygroscopicity of the optically molded article is lowered and the thermal stability is improved. When the ratio of the styrene-based monomer units is 6% by mass to 90% by mass, the hygroscopicity of the optically molded article is lowered, and not only the thermal stability is improved, but also the effect of reducing the loss of light transmittance of the long-wavelength light path can be obtained.

The ratio of (meth) acrylic acid ester monomer units in the styrene type resin is 97 mass% or less, preferably 10 mass% to 94 mass%, and more preferably 40 mass% to 90 mass%.

When the ratio of the (meth) acrylic acid ester monomer unit is 97 mass% or less, the hygroscopicity of the optically molded article is lowered, and the thermal stability is improved. When the ratio of the (meth) acrylic acid ester monomer units is from 10% by mass to 94% by mass, the hygroscopicity of the optically molded article is lowered, so that not only the thermal stability is improved but also the loss of light transmittance of the long- .

The styrenic resin may be a copolymer of an ethylenically unsaturated monomer copolymerizable with a styrenic monomer and a styrenic monomer, if necessary. Examples of the ethylenically unsaturated monomer include acrylonitrile, (meth) acrylic acid, Methacrylate, maleic anhydride and the like. When the heat resistance of the light guide plate is improved, methacrylic acid or maleic anhydride is preferable. The ethylenically unsaturated monomer may be a mixture of two or more kinds.

Here, the ratio of the ethylenically unsaturated monomer units in the styrene-based resin is 35 mass% or less, preferably 25 mass% or less, and more preferably 20 mass% or less.

When the ratio of the ethylenically unsaturated monomer units is 35 mass% or less, the effect of improving the heat resistance and the like without losing low hygroscopicity and moldability characteristic of the styrenic resin can be obtained.

(Molecular weight of styrene resin)

The molecular weight of the styrene resin is preferably from 7 to 450,000 and the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) in terms of polystyrene measured by GPC (gel permeation chromatography) is preferably from 1.7 to 2.3 .

When Mw is 70,000 or more, a strong molded body is obtained. When the Mw is 450,000 or less, workability in injection molding is improved. When Mw / Mn is 1.7 or more, the workability in extrusion molding becomes good, and when it is 2.3 or less, a strong molded article can be obtained. Mw and Mw / Mn can be adjusted by the temperature at the time of polymerization, the amount of polymerization initiator, and the like.

(The photoelastic coefficient of the styrenic resin)

The photoelastic coefficient of the styrenic resin is preferably in the range of -6 × 10 ^-12 to 6 × 10 ^-12 / Pa. More preferably, it is -4 x 10 ^-12 to 4 x 10 ^-12 / Pa.

When the photoelastic coefficient is in the range of -6 × 10 ^-12 to 6 × 10 ^-12 / Pa, unevenness in luminance is reduced when the light guide plate is used. The photoelastic coefficient can be adjusted by the ratio of the styrene-based monomer and the copolymerizable monomer.

(Melt mass flow rate of styrene resin)

The melt mass flow rate (MFR, measured at a temperature of 200 占 폚 under a load of 49 N based on JIS K7210) of the styrene type resin is preferably 0.5 to 30 g / 10 min, more preferably 3 to 20 g / 10 Min.

When the MFR is 0.5 g / 10 min or more, injection moldability is favorable, and when the MFR is 30 g / 10 min or less, extrusion moldability is favorable. The MFR can be adjusted by the molecular weight, the kind of the monomer copolymerizable with the styrene monomer, or the ratio thereof at the time of polymerization.

(Shape of styrene-based resin)

The shape of the styrene-based resin is preferably a pellet shape. For example, a strand having a diameter of 2 to 5 mm is melt-extruded from a die nozzle and passed through a cooling water bath to form a strand which is cooled to a length of 2 to 5 mm, 4 mm.

Here, the amount of cuts contained in the pellets is preferably less than 300 ppm, more preferably 1 to 200 ppm. If the cut-off amount is less than 300 ppm, the light transmittance at the long-wavelength light path becomes high. In addition, the cutting powder often contains 1 ppm or more in the pellets in the manufacturing process.

Cutting powder can be calculated by measuring the amount of cut through a wire netting when a 100 g of styrene resin is sieved with a sieve for 5 minutes using, for example, a tyler-20 mesh wire netting. The cutting amount can be adjusted according to the strand cutting condition or classification.

The total amount of the monomer and the solvent remaining in the styrene-based resin is preferably less than 1000 ppm, more preferably from 10 to 800 ppm. In addition, the amount of the monomers and solvent remaining in the styrene-based resin is often 10 ppm or more in the production process.

When the total amount of the monomers and the solvent remaining in the styrene-based resin is less than 1000 ppm, odor during molding and discoloration during long-term use can be reduced. The remaining monomers and residual solvents can be adjusted by temperature or pressure conditions in devolatilization.

The amount of the oligomer in the styrene-based resin is not particularly limited, but if a large amount of a polymerization initiator is added in order to reduce the oligomer amount, the light transmittance of the long-side light path is lowered.

A less than 0.5 part by mass of known antioxidants, light stabilizers, lubricants, plasticizers, and antistatic agents may be added to 100 parts by mass of the styrenic resin. Particularly, in the case of a light guide plate, it is preferable not to add them. When the amount of the additive is less than 0.5 parts by mass, the decrease in light transmittance of the long-wavelength light is small.

[Polymerization inhibitor]

The molded article for optical use according to this embodiment is characterized in that the content of the polymerization inhibitor in the styrene-based monomer is less than 10 ppm. When the polymerization inhibitor is less than 10 ppm, the light transmittance in the long-wavelength light path becomes high and the light resistance becomes good.

The content of the polymerization inhibitor is preferably less than 5 ppm, more preferably less than 1 ppm. When the content of the polymerization inhibitor is less than 5 ppm, the light transmittance in the long-wavelength light path is further increased, and the light resistance is improved.

Examples of the polymerization inhibitor include hydroquinone, catechol, and the like.

Normally, styrene-based monomers available on the market contain about 10 to 30 ppm of a polymerization inhibitor, and therefore, it is necessary to remove or reduce them. The method of removing or reducing is not particularly limited and a known method such as distillation or adsorption can be adopted. This method is preferably a distillation under reduced pressure.

When a styrene-based monomer is copolymerized with a copolymerizable monomer, the polymerization inhibition system in the monomer copolymerizable with the styrene-based monomer is preferably less than 10 ppm each.

[Phenylacetylene compound]

The molded article for optical use according to this embodiment is characterized in that the content of the phenylacetylene compound in the styrene-based monomer is 50 ppm or less. When the phenylacetylene compound is contained in an amount of 50 ppm or less, the light transmittance in the long-wavelength light path becomes high, and the light resistance becomes good.

The content of the phenylacetylene compound is preferably less than 40 ppm, more preferably less than 20 ppm. When the content of the phenylacetylene compound is less than 40 ppm, the light transmittance in the long-wavelength light path becomes high and the light resistance becomes good.

Since phenylacetylene in styrene usually has a low boiling point and is difficult to separate, styrene which can be obtained on the market contains about 150 ppm of phenylacetylene and needs to be removed or reduced. The method of removing or reducing is not particularly limited, and a known method such as hydrogenation or adsorption may be employed. As this method, hydrogenation treatment carried out in the presence of a hydrogenation catalyst is preferable.

[polymerization]

The styrene-based resin used in the optical molding product according to the present embodiment is preferably obtained in the polymerization reaction, in particular, by solution polymerization.

As the solvent for solution polymerization, known solvents such as toluene, xylene, ethylbenzene, hexane, cyclohexane, acetone, methyl ethyl ketone, methyl isobutyl ketone and the like can be used.

The amount of the solvent to be used is preferably from 1 to 70 parts by mass, more preferably from 2 to 30 parts by mass, based on 100 parts by mass of the total amount of the monomers to be used.

When the amount of the solvent to be used is in the range of 1 to 70 parts by mass relative to the total of 100 parts by mass of the monomers to be used, viscosity control at the time of polymerization is easily controlled by solution polymerization, and in copolymerization, the copolymer composition distribution becomes narrow, The loss of transmittance is small.

The polymerization reaction is preferably a radical solution polymerization in particular. As the radical solution polymerization, the influence of the initiator and the auxiliary agent remaining in the styrene-based resin is less and the light transmittance and light resistance of the long-wavelength light path are higher than those of the anion polymerization, cation polymerization and coordination polymerization.

(Polymerization initiator)

At the time of radical polymerization, a known polymerization initiator such as an organic peroxide or an azo compound may be added as a radical generating source.

As the polymerization initiator, it is preferable that the one-hour half-life temperature is 95 to 140 占 폚, the hydrogen releasing ability is low, and the benzene ring is not contained. The low hydrogen emission ability means that the loss of light transmittance of the long-wavelength light path is small because a fine gel component is hardly generated. In addition, when a benzene ring is not contained, coloring components are hardly produced, and loss of light transmittance of the long-wavelength light path is small.

Examples of preferred polymerization initiators include 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) -cyclohexane, Isopropyl monocarbonate, di-t-hexyl peroxide, and the like.

The addition amount of the polymerization initiator is preferably 0.01 to 0.5 parts by mass based on 100 parts by mass of the total of the monomers. More preferably, it is 0.02 to 0.2 parts by mass. When the addition amount of the polymerization initiator is 0.01 to 0.5 parts by mass, the light transmittance and light fastness of the long-wavelength light path are good.

(Chain transfer agent)

In radical polymerization, known chain transfer agents such as n-dodecylmercaptan, t-dodecylmercaptan and 2,4-diphenyl-4-methyl-1-pentene may also be added.

The addition amount of the chain transfer agent is preferably 0.001 to 0.5 parts by mass, more preferably 0.005 to 0.2 parts by mass based on 100 parts by mass of the total of the monomers. When the addition amount of the chain transfer agent is 0.001 to 0.5 part by mass, the light transmittance in the long-wavelength light path becomes high and the light resistance becomes good.

The polymerization temperature in the polymerization of the styrene-based resin is preferably 90 to 180 占 폚, more preferably 95 to 170 占 폚. When the temperature is from 90 to 180 占 폚, the light transmittance and light fastness of the long-wavelength light path become good.

(Removal of dissolved oxygen)

It is preferable that the styrene monomer and the solvent to be used in the optical molded article according to the present embodiment are provided for polymerization after removing dissolved oxygen. The method for removing dissolved oxygen is not particularly limited, and a method of bubbling with nitrogen gas can be employed.

When the dissolved oxygen is removed, the color of the molded article may be colorless and may be good for optical use. When copolymerizing a styrene-based monomer with a copolymerizable monomer, it is preferable to remove dissolved oxygen of a monomer copolymerizable with the styrene-based monomer and then to provide the monomer for polymerization.

(Removal of foreign matter)

Further, it is preferable that the styrene monomer and the solvent used in the optical molding product according to the present embodiment are provided for polymerization after removing the foreign substance. The method for removing foreign matters is not particularly limited, and a method of filtration with a filter can be employed.

If the foreign matter is removed, the light transmittance of the long-wavelength light path may be increased. When a styrene-based monomer is copolymerized with a monomer copolymerizable with the styrene-based monomer, it is preferable to remove foreign matters of a monomer copolymerizable with the styrene-based resin and then to provide the monomer for polymerization.

In the styrenic resin according to the present embodiment, a styrenic resin can be molded by a known method such as an injection molding method, an extrusion molding method, or a solvent casting method to obtain an optical molding. Particularly, an injection molding method or an extrusion molding method is preferable.

The molding conditions are not particularly limited, but molding at 200 to 300 캜 is preferable.

[Light guide plate]

Examples of applications of the optical molded article according to the present embodiment include a light guide plate, a diffusion plate, and a lens. Particularly, since the optical molded article according to the present embodiment has a small loss in light transmittance in the long-wavelength light path, and is particularly excellent in light resistance against light having a wavelength of 400 nm or more, it is useful as a light guide plate for a liquid crystal display or a light- In particular, it is useful as a light guide plate for medium to large liquid crystal displays using LED as a light source.

The thickness of the light guide plate of the present embodiment is preferably 0.3 to 8 mm, more preferably 0.4 to 5 mm. The light guide plate having such a thickness is advantageous in that it can sufficiently introduce light as a light guide plate for a medium to large display of 20 inches or more, and has sufficient rigidity for handling.

The light guide plate according to the present embodiment may contain other components such as an organic light-diffusing agent such as crosslinked acrylic particles, crosslinked styrene-based particles and siloxane resin particles, barium sulfate, calcium carbonate, oxidized An inorganic light-diffusing agent such as titanium can be compounded.

[Optical Diffuser]

In addition, as the use of the optical molded article according to the present embodiment, the optical properties such as the total light transmittance (or the light transmittance) and the diffusivity become good even in the case of the light diffusion. Therefore, it is useful as a light diffuser used for various purposes such as illumination.

As a method for diffusing light as the light diffusing body, various methods such as a method of putting the light diffusing agent into the inside of the light diffusing body, a method of attaching the light diffusing agent to the surface, and a method of applying the light diffusing agent to the surface of the light diffusing agent can be adopted.

As the light diffusing agent, an organic light diffusing agent such as crosslinked acrylic particle, crosslinked styrene particle, siloxane resin particle or the like, or an inorganic light diffusing agent such as barium sulfate, calcium carbonate or titanium oxide can be used. When a crosslinked acrylic particle, a crosslinked styrene particle, a siloxane resin particle or a calcium carbonate is used as a light diffuser, it is preferable to have a good balance of optical properties such as total light transmittance and diffusivity.

The content of the light-diffusing agent in the light-diffusing body is not particularly limited, but if it is contained in the range of 0.1 to 10 mass%, it is possible to obtain an optical diffusing body having an excellent balance of the total light transmittance and the diffusing ratio or both . By containing 0.1% by mass or more of the light-diffusing agent, it is possible to obtain a high diffusion property, and when it is 10% by mass or less, the decrease in the total light transmittance is small.

As means for containing the light-diffusing agent in the light-diffusing body, a known method such as extrusion molding can be adopted.

In the light diffusing body according to the present embodiment, less than 0.5 part by mass of known antioxidants, light stabilizers, lubricants, plasticizers, antistatic agents, fluorescent whitening agents, fluorescent materials and phosphorescent materials can be added to 100 parts by mass of the styrene- have. If the amount of the additive is less than 0.5 parts by mass, deterioration of optical properties such as total light transmittance (or light transmittance) and diffusivity is small.

&Lt; Action &gt;

Hereinafter, the operation effects of the optical molded article, particularly the light guide plate and light diffuser, according to the above embodiments will be described.

The optical molded article according to the above embodiment is an optical molded article obtained by molding a styrene resin obtained by polymerization reaction of a styrenic monomer having a polymerization inhibitor of less than 10 ppm and a phenylacetylene compound of 50 ppm or less.

The optical molded article according to the above embodiment has a low hygroscopicity and thus has less warping and dimensional change, less loss of light transmittance in the long-wavelength light path, and good light fastness.

Particularly, when the styrene-based resin is a styrene- (meth) acrylate-based copolymer, it is possible to obtain an effect that the balance of warpage, dimensional change, light transmittance in the long-side light path and light resistance becomes better.

In addition, since the polymerization reaction is a radical solution polymerization reaction, the effect of the initiator and the auxiliary agent remaining in the styrene-based resin is less and the light transmittance and light resistance of the long-wavelength light path can be increased.

The optical molded article according to the above embodiment is useful as a light guide plate for a liquid crystal display or a light guide plate for illumination, particularly, since it has good light resistance against light having a wavelength of 400 nm or more, , And is useful as a light guide plate for medium to large liquid crystal displays using LED as a light source.

In addition, the optical molded article according to the above embodiment has good optical properties such as total light transmittance (or light transmittance) and diffusivity. Therefore, it is useful as a light diffuser used for various purposes such as illumination.

The optical molded article according to the present invention, in particular, the light guide plate and the optical diffuser have been described by way of examples, but the present invention is not limited thereto.

For example, since the optical molded article according to the present invention has less warping and dimensional changes, it can be suitably used not only for a medium to large display but also for a small display requiring precise size adjustment. It can also be suitably used for a lighting device other than a display and a display device.

Further, the optical molded article according to the present invention may be obtained by a manufacturing method including the following steps.

A step of reducing the polymerization inhibitor contained in the styrene-based monomer to less than 10 ppm; a step of reducing the phenylacetylene-based compound contained in the styrene-based monomer to 50 ppm or less; A polymerization reaction step of polymerizing the monomer to obtain a styrene-based resin; and a molding step of molding the styrene-based resin.

The molded article for optical use obtained by the above-mentioned production method has a low hygroscopicity and therefore has less warping and dimensional change, less loss of light transmittance in the long-wavelength light path, and good light resistance.

[Example]

Hereinafter, the details of the optical molded article according to the present invention, in particular, the light guide plate and the optical diffuser will be described with reference to examples, but the present invention is not limited to the following examples.

[Styrene-based monomer]

First, styrenic monomers used in Examples and Comparative Examples will be described.

(Styrene-1)

Industrial styrene was prepared, and it was found that 4-t-butyl catechol as a polymerization inhibitor was contained at 12 ppm and phenoxy acetylene as an impurity at 130 ppm. This industrial styrene is hydrogenated in the presence of a hydrogenation catalyst to selectively hydrogenate the phenylacetylene contained therein and then distillation under reduced pressure to obtain 4-t-butylcateol of less than 0.1 ppm and 10 ppm of phenylacetylene Styrene-1 was obtained.

(Styrene-2)

4-t-butylcatechol was added to styrene-1 to obtain styrene-2 containing 7 ppm of 4-t-butylcatechol.

(Styrene-3)

Styrene-1 was added with 4-t-butylcatechol to obtain styrene-3 containing 12 ppm of 4-t-butylcatechol.

(Styrene-4)

Phenylacetylene was added to styrene-1 to obtain styrene-4 containing 43 ppm of phenylacetylene.

(Styrene-5)

Phenylacetylene was added to styrene-1 to obtain styrene-5 containing 130 ppm of phenylacetylene.

[(Meth) acrylic acid ester monomer]

(MMA-1)

Next, the (meth) acrylate monomer will be described.

When industrially methyl methacrylate was prepared, it was found that 5 ppm of topanol was included as a polymerization inhibitor. Let this be MMA-1.

[Example 1]

52 parts by mass of the styrene-1, 48 parts by mass of the MMA-1 and 12 parts by mass of ethylbenzene as a solvent were mixed and bubbled with nitrogen for 1 hour to remove dissolved oxygen. The supernatant was filtered Thereby obtaining a raw material solution.

Then, a first complete mixing type reactor having a volume of about 5 liters, a second complete mixing type reactor having a volume of about 15 liters, a tower type plug flow type reactor having a capacity of about 40 liters, and a preheater were connected in series to each other with a stirrer .

0.03 parts by mass of 1,1-di (t-hexylperoxy) -cyclohexane (manufactured by Nippon Oil and Fats Co., Ltd.) and 0.015 parts by mass of n-dodecylmercaptan (thioalcohol 20 manufactured by Kao Corporation) And introduced into a first complete mixing type reactor controlled at a temperature of 95 ° C at a rate of 6 kg per hour.

Further, the rotation speed of the stirrer of the first fully-mixed type reactor was 300 rpm. The reaction solution was continuously extracted from the first complete mixed type reactor and introduced into a second complete mixed type reactor controlled at a temperature of 125 캜.

Further, the rotation speed of the stirrer of the second fully-mixed type reactor was 180 rpm. The reaction liquid was continuously extracted from the second complete mixed-type reactor and introduced into a column-type plug flow type reactor adjusted to have a slope of from 125 ° C to 160 ° C toward the direction of flow.

The reaction solution was introduced into a devolatilizer controlled at a temperature of 240 캜 at a pressure of 1.0 kPa while being heated by a preheater to remove volatile components such as solvent and unreacted monomers.

Then, this resin liquid was extracted with a gear pump, extruded into a strand shape, and cut while cooling to obtain a pellet-shaped styrene resin. Further, the fine powder contained in the pellets was removed by classification.

The obtained styrene resin had Mw = 180,000 and Mw / Mn = 1.8, and it was confirmed that the total amount of the monomer and solvent remaining in the styrene resin was less than 1000 ppm and the cut amount was less than 300 ppm.

The cuts were calculated by measuring the amount of cut through the wire netting when a 100 g of styrene resin was sieved with a sieve for 5 minutes using a wire mesh of Tyler-20 mesh.

The pellets were molded by J350 ELIII manufactured by Nippon Seiko Kogyo Co., Ltd. in a motor-driven injection molding machine at a molding temperature of 270 占 폚 and having a length of 292.5 mm, a width of 220 mm and a thickness of 2 mm. The optical characteristics of the obtained molded article were evaluated. The results are shown in Table 1.

[Example 2]

Styrene-1 was changed to 40 parts by mass, and MMA-1 was changed to 60 parts by mass. The results are shown in Table 1.

[Example 3]

Styrene-1 was changed to 11 parts by mass, and MMA-1 was replaced by 89 parts by mass. The results are shown in Table 1.

[Example 4]

Styrene-1 was changed to 100 parts by mass, and MMA-1 was changed to 0 parts by mass. The results are shown in Table 1.

[Example 5]

The procedure of Example 1 was repeated except that styrene-2 was used instead of styrene-1. The results are shown in Table 1.

[Example 6]

Styrene-4 was used in place of styrene-1. The results are shown in Table 1.

The evaluation of the properties of the molded product was carried out by the following method.

(1) Polymerization inhibitor (4-t-butylcatechol)

Sodium hydroxide was added to the sample and stirred. The colored solution was measured for absorbance (wavelength: 486 nm) with a spectrophotometer, and the concentration was calculated from the previously prepared calibration curve.

(2) residual monomer, residual solvent, phenylacetylene

The measurement was performed under the GC measurement conditions described below.

Device: GC12A FID detector manufactured by Shimadzu Corporation

Column: Glass column φ3 mm × 3 m

Filler: Polyethylene glycol

Carrier: nitrogen

Temperature: Column 115 ° C, inlet 220 ° C

0.5 g of the sample pellets, 0.001 g of cyclopentane, and N, N-dimethylformamide were dissolved and cyclopentane was used as an internal standard.

(3) Hygroscopicity

Using the molded plate, the saturation absorption rate (unit:%) was determined by the method A based on JIS K7209. Less than 1.5% were accepted.

(4) Hayes

The haze (unit:%) was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) based on JIS K7105 in a 2 mm thickness portion of the molded plate. Less than 0.3% was accepted.

(5) Transparency of long-light path (light transmittance)

The end face of the molded plate was polished by using a gate processing machine GCPB manufactured by Megaro Technica Co., Ltd. The transmittance (unit:%) of light transmitted vertically through the polished surface was measured using a long-wavelength light measuring apparatus ASA-300A manufactured by Nippon Denshoku Kogyo Co.,

(6) Refractive index

The refractive index was measured using an Abbe refractometer (Abbe refractometer 2-T manufactured by Atago Co., Ltd.) in 2 mm thickness portions of the molded plate.

(7) Reflectance

The reflectance (unit:%) was calculated using the refractive index measured in (6) using the following formula.

(8) Transparent loss ratio

(Unit:%) was calculated using the light transmittance of the long-wavelength light path measured in (5) and the reflectance calculated in (7) using the following formula. The fact that the reflectance is doubled indicates two surfaces, that is, the light incidence surface and the light exiting surface. Less than 8% were accepted.

(9) Light fastness

PMMA VH5 manufactured by Mitsubishi Rayon Co., Ltd., Tinuvin P manufactured by Ciba Specialty Chemicals Co., Ltd., and Tinuvin P manufactured by Ciba Specialty Chemicals Co., Ltd. were used under the conditions of a cylinder temperature of 230 캜 using a single screw extruder PMS40 manufactured by IKG A light stabilizer, Hostavin PR-25, manufactured by ANT Japan Co., Ltd., was melt-kneaded in a mass ratio of 99: 0.5: 0.5 to obtain a resin for an ultraviolet light filter. This resin was subjected to an ultraviolet light filter having a length of 292.5 mm, a width of 220 mm and a thickness of 2 mm at a molding temperature of 270 DEG C by J350 ELIII manufactured by Nippon Seiko Kogyo Co., Ltd. in a motor-driven injection molding machine. It was confirmed that this ultraviolet light filter hardly transmits light having a wavelength of less than 400 nm.

The molded product of the styrene-based resin obtained in the examples and comparative examples was superimposed on the ultraviolet light filter. Using a weather-ometer Ci65A manufactured by Atlas Co., the temperature was 63 ° C and the irradiation intensity was 0.35 W / m ² Intensity), the light of the xenon light source was irradiated from the ultraviolet light filter side for 200 hours. That is, light of 400 nm or more transmitted through an ultraviolet light filter was applied to the molded article of the styrene type resin. The b value (unit: -) at 2 mm portions of the light-irradiated molded article was measured in accordance with JIS K7105 using a color difference system Σ80 manufactured by Nippon Denshoku Kogyo Co., Ltd., and Δb was calculated by the following equation Respectively. And? B was less than 1.

Δb = b value after irradiation for 200 hours - b value before irradiation

As can be seen from Table 1, the optical molded article of the example according to the present invention had low hygroscopicity, reduced loss of light transmittance in the long-wavelength light path, and good light resistance.

[Comparative Example 1]

Styrene-1 was replaced by 0 part by mass, and MMA-1 was replaced by 100 parts by mass. The results are shown in Table 1.

[Comparative Example 2]

The procedure of Example 1 was repeated except that styrene-3 was used instead of styrene-1. The results are shown in Table 1.

[Comparative Example 3]

The procedure of Example 1 was repeated except that styrene-5 was used instead of styrene-1. The results are shown in Table 1.

<Review>

Since the molded article for optical use of the example of the present invention has low hygroscopicity, warpage and dimensional change are small, loss of light transmittance in the long-wavelength light is small, and light resistance of 400 nm or more is good.

In Comparative Example 1, since only acrylic resin is used, the hygroscopicity is remarkably high.

In Comparative Example 2, the light transmittance of the long optical path is low and the light transmittance loss of the long optical path is large. In addition, it can be seen that the value of DELTA b is large and the light resistance is bad. This is presumably because the content of the polymerization inhibitor is 10 ppm or more.

Further, in Comparative Example 3, the transparent loss of the long-wavelength light path is large, and the value of? B is remarkably large, so that the light resistance is poor. This is presumably because the content of the phenylacetylene compound is 50 ppm or more.

As described above, the molded article for optical use according to the present invention has a low hygroscopicity and therefore has less warpage and dimensional changes, has a high light transmittance in a long-wavelength light path, and has good light resistance.

In addition, when the optical molded article according to the present invention is used as a light guide plate, it is useful as a light guide plate for a liquid crystal display or a light guide plate for illumination, and particularly has good light resistance against light having a wavelength of 400 nm or more. Or as a light guide plate for a large liquid crystal display.

[Optical Diffuser]

The details of the optical diffuser according to the present invention will be described with reference to Examples, but the present invention is not limited to the following Examples.

[Styrene-based resin]

The styrene resin used in Examples and Comparative Examples will be described.

The styrene resin obtained by the method of Example 1 is referred to as styrene resin 1. The styrene resin obtained by the method of Example 2 is referred to as styrene resin 2. The styrene resin obtained by the method of Example 3 is referred to as styrene resin 3. The styrene resin obtained by the method of Example 4 is referred to as styrene resin 4.

The styrene resin obtained by the same method as in Example 1 using styrene 2 is referred to as styrene resin 5. The styrene-based resin obtained by the same method as in Example 2 using styrene 2 is referred to as styrene-based resin 6. The styrene resin obtained by the same method as in Example 3 using styrene 2 is referred to as styrene resin 7. The styrene resin obtained by the same method as in Example 4 using styrene 2 is referred to as styrene resin 8.

The styrene resin obtained by the same method as in Example 1 using styrene 3 is referred to as styrene resin 9. The styrene resin obtained by the same method as in Example 2 using styrene 3 is referred to as styrene resin 10. The styrene resin obtained by the same method as in Example 3 using styrene 3 is referred to as styrene resin 11. The styrene resin obtained by the same method as in Example 4 using styrene 3 is referred to as styrene resin 12.

The styrene resin obtained by the same method as in Example 1 using styrene 4 is referred to as styrene resin 13. The styrene resin obtained in the same manner as in Example 2 using styrene 4 is referred to as styrene resin 14. The styrene resin obtained by the same method as in Example 3 using styrene 4 is referred to as styrene resin 15. The styrene-based resin obtained by the same method as in Example 4 using styrene 4 is referred to as styrene-based resin 16.

The styrene-based resin obtained by the same method as in Example 1 using styrene 5 is referred to as styrene-based resin 17. The styrene-based resin obtained by the same method as in Example 2 using styrene 5 is referred to as styrene-based resin 18. The styrene resin obtained by the same method as in Example 3 using styrene 5 is referred to as styrene resin 19. The styrene resin obtained by the same method as in Example 4 using styrene 5 is referred to as styrene resin 20.

[Example 7]

, 96% by mass of the styrene-based resin 1 was melt-kneaded using a twin-screw extruder TEM-35B manufactured by Toshiba Machine Co., Ltd. under the conditions of a tip temperature of 230 占 폚, calcium carbonate (manufactured by Konpontokushugaku Co., Product name: Lumi Pearl DSN-7) was mixed and kneaded at a mixing ratio of 4% by mass to obtain a pellet-like resin composition. This pellet-shaped resin composition was molded under the conditions of a cylinder temperature of 230 캜 and a mold temperature of 60 캜 by using an injection molding machine J140 AD-180H manufactured by Nippon Seiko Kogyo Co., To obtain a 2 mm-shaped molded article.

[Example 8]

The procedure of Example 7 was repeated except that styrene resin 1 was used as the styrene resin and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 9]

The procedure of Example 7 was repeated except that styrene type resin 1 was used as styrene type resin 1 in an amount of 98% by mass and a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials as a light diffusing agent was used in an amount of 2% by mass .

[Example 10]

The procedure of Example 7 was repeated except that styrene resin 2 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 11]

Styrene resin 2 as a styrene resin, and calcium carbonate (trade name: Lumipulse DSN-7, manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Example 12]

The procedure of Example 7 was repeated except that styrene type resin 2 was used as a styrene type resin 2 in an amount of 98% by mass and a siloxane resin particle (trade name: Tospearl 120) manufactured by Momentive Performance Materials Co., Ltd. as a light diffusing agent was used in an amount of 2% by mass .

[Example 13]

The procedure of Example 7 was repeated except that styrene resin 3 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 14]

Styrene resin 3 as a styrene resin, and calcium carbonate (trade name: Lumi Pearl DSN-7 manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Example 15]

The procedure of Example 7 was repeated except that styrene resin 4 was used as the styrene resin and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 16]

Styrene resin 5 as a styrene resin, and calcium carbonate (trade name: Lumipulse DSN-7 manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Example 17]

Styrene resin 5 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Example 18]

The procedure of Example 7 was repeated except that styrene type resin 5 was used as a styrene type resin 5 in an amount of 98% by mass and a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials Co., Ltd. as a light diffusing agent was used in an amount of 2% by mass .

[Example 19]

The procedure of Example 7 was repeated except that styrene resin 6 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 20]

Styrene resin 6 as a styrene resin, and calcium carbonate (trade name: Lumi Pearl DSN-7 manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Example 21]

The procedure of Example 7 was repeated except that styrene type resin 6 was used as a styrene type resin 6 in an amount of 98% by mass and a siloxane resin particle (product name: Tosulfur 120) manufactured by Momentive Performance Materials Co., Ltd. as a light diffusing agent was used in an amount of 2% by mass .

[Example 22]

Styrene resin 7 as a styrene resin, and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Example 23]

Except that styrene resin 7 was used as the styrene resin and calcium carbonate (trade name: Lumipulse DSN-7, manufactured by Gonpot Tokushu Kagaku Co., Ltd.) was used as the light diffusing agent.

[Example 24]

Styrene resin 8 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Example 25]

Styrenic resin 13 as a styrene resin, and calcium carbonate (trade name: Lumi Pearl DSN-7) manufactured by Gonpot Tokushu Kagaku Co., Ltd. as a light diffusing agent.

[Example 26]

Styrene resin 13 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Example 27]

The same procedures as in Example 7 were carried out except that styrene type resin 13 was used in an amount of 98% by mass and a light diffusing agent was used in an amount of 2% by mass of siloxane resin particles (trade name: Tosulfur 120) manufactured by Momentive Performance Materials Co. .

[Example 28]

The procedure of Example 7 was repeated except that styrene resin 14 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 29]

The procedure of Example 7 was repeated except that styrene resin 14 was used as the styrene resin and calcium carbonate (trade name: Lumipulse DSN-7) manufactured by Gonpot Tokushu Kagaku Co., Ltd. was used as the light diffusing agent.

[Example 30]

The same procedures as in Example 7 were carried out except that styrene type resin 14 was used in an amount of 98% by mass and a light diffusing agent was used in an amount of 2% by mass of a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials Co. .

[Example 31]

The procedure of Example 7 was repeated except that styrene resin 15 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Example 32]

Styrene resin 15 as a styrene resin, and calcium carbonate (trade name: Lumipulse DSN-7, manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Example 33]

Styrene resin 16 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Comparative Example 4]

Styrenic resin 9 as a styrene resin and calcium carbonate (trade name: Lumipulse DSN-7 manufactured by Gonpot Tokushu Kagaku Co., Ltd.) as a light diffusing agent.

[Comparative Example 5]

Styrene resin 9 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Comparative Example 6]

The procedure of Example 7 was repeated except that the styrene type resin 9 was used in an amount of 98% by mass and the light diffusing agent was 2% by mass of a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials, Inc. .

[Comparative Example 7]

The procedure of Example 7 was repeated except that styrene resin 10 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Comparative Example 8]

The procedure of Example 7 was repeated except that styrene resin 10 was used as the styrene resin and calcium carbonate (trade name: Lumipulse DSN-7) manufactured by Gonpot Tokushu Kagaku Co., Ltd. was used as the light diffusing agent.

[Comparative Example 9]

The procedure of Example 7 was repeated except that the styrene type resin 10 was used in an amount of 98% by mass and the light diffusing agent was used in an amount of 2% by mass of a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials, Inc. .

[Comparative Example 10]

Except that styrene resin 11 as a styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent were used.

[Comparative Example 11]

The procedure of Example 7 was repeated except that styrene resin 11 was used as the styrene resin and calcium carbonate (trade name: Lumi Pearl DSN-7) manufactured by Gonpotto Cushing Co., Ltd. was used as the light diffusing agent.

[Comparative Example 12]

Styrene resin 12 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Comparative Example 13]

Styrenic resin 17 as a styrene resin and calcium carbonate (trade name: Lumi Pearl DSN-7 manufactured by Gonpot Corporation) as a light diffusing agent.

[Comparative Example 14]

Styrene resin 17 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

[Comparative Example 15]

The same procedures as in Example 7 were carried out except that styrene type resin 17 was used as a styrene type resin 17 in an amount of 98% by mass and a siloxane resin particle (product name: Tospearl 120) manufactured by Momentive Performance Materials Co., Ltd. as a light diffusing agent was used in an amount of 2% .

[Comparative Example 16]

The procedure of Example 7 was repeated except that styrene resin 18 was used as the styrene resin and crosslinked styrene particles (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. as the light diffusing agent.

[Comparative Example 17]

Styrenic resin 18 as a styrene resin, and calcium carbonate (trade name: Lumi Pearl DSN-7) manufactured by Gonpot Tokushu Kagaku Co., Ltd. as a light diffusing agent.

[Comparative Example 18]

The procedure of Example 7 was repeated except that styrene type resin 18 was used as styrene type resin 18 in an amount of 98% by mass and a siloxane resin particle (trade name: Tosulfur 120) manufactured by Momentive Performance Materials Co., Ltd. as a light diffusing agent was used in an amount of 2% by mass .

[Comparative Example 19]

A styrene resin 19 was used as the styrene resin and a crosslinked styrene particle (trade name: Tech polymer SBX-8) manufactured by Sekisui Plastics Co., Ltd. was used as the light diffusing agent.

[Comparative Example 20]

Styrenic resin 19 as a styrene resin and calcium carbonate (trade name: Lumi Pearl DSN-7) manufactured by Gonpot Tokushu Kagaku Co., Ltd. as a light diffusing agent.

[Comparative Example 21]

Styrene resin 20 as a styrene resin, and crosslinked acrylic particles (trade name: Tech polymer MBX-8) manufactured by Sekisui Plastics Co., Ltd. as a light diffusing agent.

The following evaluations were carried out on each of the molded articles of Examples 7 to 33 and Comparative Examples 4 to 21.

(10) Overall light transmittance, haze

Based on JIS K7105, the total light transmittance and haze (unit:%) of the molded article were measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

(11) Spreading rate

The light transmittance at each angle of the molded article was measured using a goniophotometer (GC5000L, manufactured by Nippon Denshoku Kogyo Co., Ltd.). Using the numerical value of the light transmittance at a specific angle, the diffusivity (%) defined by the following formula was calculated (diffusivity: JIS Z8113 No. 04100).

(12) Distribution of illuminance

The illuminance was measured by the following method based on JIS C7612 using an illuminance meter (manufactured by Tokyo Optical Manufacturing Co., Ltd., IM-3). The illuminance distribution on a horizontal plane with a vertical distance of 1 m from the molded article attached to the illumination was determined as the illuminance distribution with a half width (unit: cm).

[Measurement method of illuminance]

The cover provided on the LED lighting (manufactured by Toshiba Latec Co., Ltd., Mid Reflector type, LEL-SL5N-F 40W) was peeled off and each molded body was attached (distance between the LED chip and the molded body was 8 mm). This was lighted in a dark place, allowed to stand for 30 minutes or longer to stabilize the light source, and the illuminance at a predetermined place was measured.

(13) Light fastness

(9) Light resistance test "was carried out except that the molded articles of Examples 7 to 33 and Comparative Examples 4 to 21 were used in the test samples.

The results of the above Examples and Comparative Examples are shown in Tables 2 to 6.

<Review>

As shown in Tables 2 to 4, the optical molded article of the example according to the present invention had good light transmittance and diffusivity, and good light resistance of 400 nm or more.

It is considered that the reason why the diffusion rate is lowered in the comparative example is that the amount of the inhibitor is 10 ppm or more, or the amount of the phenylacetylene compound is 50 ppm or more. The reason why the Δb value indicating the light resistance is large in the comparative example is that the amount of the polymerization inhibitor is 10 ppm or more and the content of the phenylacetylene compound is 50 ppm or more.

INDUSTRIAL APPLICABILITY As described above, the optical diffusing material according to the present invention has good total light transmittance and diffusivity, and has good light resistance. Therefore, it is useful as a light diffuser used for various purposes such as illumination.

Also, since the light resistance against light having a wavelength of 400 nm or more is good, it is also useful as an optical diffuser (diffusion plate, diffusion cover, etc.) using an LED as a light source.

Claims (6)

Wherein the polymerization inhibitor is less than 10 ppm and the phenylacetylene compound is 50 ppm or less. The molded article for optical use according to claim 1, wherein the styrene-based resin is a styrene- (meth) acrylate-based copolymer. The optical molded article according to claim 1 or 2, wherein the polymerization reaction is a radical solution polymerization reaction. A light guide plate using the optical molded article according to claim 1 or 2. An optical diffuser using the optical molded article according to claim 1 or 2. The optical diffuser according to claim 5, wherein the light diffusing agent comprises at least one kind of light diffusing agent selected from the group consisting of crosslinked acrylic particles, crosslinked styrene particles, siloxane resin particles and calcium carbonate at not less than 0.1 mass% and not more than 10 mass%.