KR101842858B1 - Methacrylate copolymer for light guide plate and light guide plate using thereof - Google Patents

Abstract

The present invention relates to a methacrylate copolymer used for producing a light guide plate constituting a backlight for liquid crystal displays mounted with a light-emitting device (LED) light source. More specifically, the present invention relates to a methacrylate copolymer capable of being applied to light guide plates in thin films due to excellent heat resistance, low moisture absorptiveness, and low high-temperature/high-humidity expansion rate. The present invention further relates to a light guide plate using the same.

Description

[0001] METHACRYLATE COPOLYMER FOR LIGHT GUIDE PLATE AND LIGHT GUIDE PLATE USING THEREOF [0002]

The present invention relates to a methacrylate copolymer used for producing a light guide plate constituting a backlight for a liquid crystal display to which an LED light source is attached. The methacrylate copolymer is excellent in heat resistance, low hygroscopicity, And a light guide plate using the methacrylate copolymer.

The light guide plate is used for various liquid crystal displays and is known as an optical member that guides light from a light source disposed on the back surface of a light guide plate and sends the light to the surface of the liquid crystal display.

Recently, an LED (light emitting diode) array is used as a light source for a liquid crystal display. When the LED light source is used, the temperature inside the display increases due to the heat of the LED, and the light guide plate is exposed to high temperature for a long time.

For this reason, heat resistance and moisture resistance are required for the light guide plate. Studies have been conducted to copolymerize methyl methacrylate with various monomers for the moisture resistance. In order to improve moisture resistance, styrene (styrene) It has been known that it can be used as a comonomer. However, recently, the thickness of the light guide plate has become thinner as the display has become thinner, and in order to maintain the heat resistance even at a thinner thickness, a methacrylic resin having a heat resistance higher than that of the conventional resin is required.

 In addition, there is a demand for a process for manufacturing a light guide plate and a property that does not cause deformation under high temperature and high humidity conditions that may occur during transportation.

An object of the present invention is to provide a methacrylate copolymer for producing a light guide plate constituting a backlight for a liquid crystal display equipped with an LED light source.

It is another object of the present invention to provide a methacrylate copolymer which is further improved in heat resistance so as to be applicable to a thin film light guide plate, has low hygroscopicity, and has a low temperature and high humidity expansion rate.

Another object of the present invention is to provide a light guide plate having excellent optical properties, excellent heat resistance, low hygroscopicity and low expansion rate at high temperature and high humidity by using the methacrylate copolymer.

In order to achieve the above object, the present invention provides a copolymer of methyl methacrylate, styrene, and comonomer,

Wherein the comonomer is at least one aromatic vinyl compound selected from a-methylstyrene, m-methylstyrene, p-methylstyrene and p-methoxystyrene;

An acid anhydride monomer represented by the following formula (1);

[Chemical Formula 1]

In the above formula, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

One or more imide compound selected from N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-cyclohexylmaleimide; Or a mixture of two or more thereof,

A glass transition temperature of 110 ° C or higher, and a moisture absorption rate according to KS M ISO 62 of 0.2% or lower.

The present invention also relates to a light guide plate comprising the methacrylate copolymer.

The methacrylate copolymer for a light guide plate according to the present invention is produced by continuous bulk polymerization and has excellent optical properties. In addition, since the glass transition temperature is 110 ° C or more and the heat resistance is excellent and the expansion ratio at high temperature and high humidity is low, The present invention can be applied to a liquid crystal display mounted thereon, and it is possible to manufacture a thin light guide plate.

In addition, the light guide plate using the methacrylate copolymer for a light guide plate according to the present invention has a small expansion and warpage, and is excellent in dimensional stability.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described more fully hereinafter with reference to the accompanying drawings, It should be understood, however, that the invention is not limited thereto and that various changes and modifications may be made without departing from the spirit and scope of the invention.

Unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention is merely intended to effectively describe a specific embodiment and is not intended to limit the invention.

Also, the singular forms as used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The inventors of the present invention conducted studies to solve the problem of deformation of LED light source due to high temperature when manufacturing a thin film light guide plate as an acrylic polymer used in a conventional light guide plate, , The optical properties, that is, the long-wavelength light transmittance of 85% or more, can satisfy the properties required of the light guide plate, and the high temperature and high humidity measured at 60 ° C and 90% RH after 24 hours It is possible to satisfy the physical properties that the expansion ratio is 0.3% or less and the heat resistance can be further improved at a glass transition temperature of 110 캜 or higher, and thus the present invention has been completed.

One aspect of the invention is a copolymer of methyl methacrylate, styrene, and comonomers,

Wherein the comonomer is at least one aromatic vinyl compound selected from a-methylstyrene, m-methylstyrene, p-methylstyrene and p-methoxystyrene;

An acid anhydride monomer represented by the following formula (1);

[Chemical Formula 1]

In the above formula, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

One or more imide compound selected from N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-cyclohexylmaleimide; Or a mixture of two or more thereof,

Is a methacrylate copolymer for a light guide plate having a glass transition temperature of 110 ° C or higher and a moisture absorption rate according to KS M ISO 62 of 0.2% or less.

In one embodiment of the present invention, the methacrylate copolymer may be a copolymer containing 65 to 80% by weight of methyl methacrylate, 15 to 25% by weight of styrene, and 5 to 10% by weight of a comonomer.

In one embodiment of the present invention, the methacrylate copolymer may be one produced by continuous bulk polymerization.

In one embodiment of the present invention, the methacrylate copolymer may have a polymerization conversion of 40 to 55%.

In one embodiment of the present invention, the methacrylate copolymer may have a weight average molecular weight of 110,000 to 150,000 g / mol.

In one embodiment of the present invention, the methacrylate copolymer may have a melt index of 7 to 15 g / 10 minutes measured at 230 DEG C and 3.8 kg.

Another embodiment of the present invention is a light guide plate comprising the methacrylate copolymer.

In one embodiment of the light guide plate of the present invention, the light guide plate may be one used in a liquid crystal display equipped with an LED light source.

In one embodiment of the light guide plate of the present invention, the light guide plate may have a long-light transmittance of 85% or more according to ISO 13468-1.

In one embodiment of the light guide plate of the present invention, the light guide plate may have a high temperature and high humidity expansion rate of 0.3% or less as measured after 24 hours at 60 ° C and 90% RH.

Hereinafter, each configuration of the present invention will be described in more detail.

In one embodiment of the present invention, the methacrylate copolymer is characterized by a combination of methyl methacrylate, styrene, and comonomers, wherein 65 to 80 wt% of methyl methacrylate, 15 to 25 wt% of styrene, 5 to 10% by weight is preferably copolymerized.

By using the methyl methacrylate in an amount of 65 to 80% by weight, it is possible to provide a light guide plate having excellent optical properties and excellent moldability, and a copolymer having improved moisture resistance in the range of 15 to 25% by weight of styrene . The comonomer is added in order to increase the glass transition temperature of the copolymer, lower the hygroscopicity, and lower the high temperature and high humidity expansion rate in order to further improve the heat resistance. The content of the comonomer may be in the range of 5 to 10% desirable. The comonomers may be used singly or in combination of two or more, and when they are used in combination, the total content of the comonomers used is preferably from 5 to 10% by weight because the optical properties are not deteriorated .

In one embodiment of the present invention, the comonomer may be any one or two or more aromatic vinyl compounds selected from a-methylstyrene, m-methylstyrene, p-methylstyrene and p-methoxystyrene;

An acid anhydride monomer represented by the following formula (1);

[Chemical Formula 1]

In the above formula, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

One or more imide compound selected from N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-cyclohexylmaleimide; Or a mixture of two or more thereof.

By using the comonomer, the glass transition temperature can be 110 ° C or higher, more specifically 110 to 120 ° C, and the glass transition temperature is improved by 5 ° C or more as compared with the case where no comonomer is used . In addition, it is possible to satisfy the property that the moisture absorption rate according to KS M ISO 62 is 0.2% or less. Accordingly, when the light guide plate of the thin film is manufactured, the property having the high temperature and high humidity expansion rate measured at 60 캜 and 90% RH for 24 hours is 0.3% can do.

From the viewpoint of further lowering the moisture absorption rate of the comonomer, further lowering the high-temperature high-humidity expansion rate, and further increasing the glass transition temperature, any one selected from a-methylstyrene, maleic anhydride and N-cyclohexylmaleimide Or a mixture of two or more thereof.

When the comonomer is used in combination, the respective monomers may be mixed at a weight ratio of 1:10 to 10: 1, or at a ratio of 1: 3: 1 to 3: 1 to 3 at a weight ratio.

The polymerization method for polymerizing the above-mentioned monomer components is not particularly limited, and known methods such as bulk polymerization, solution polymerization and suspension polymerization can be used. However, And a continuous bulk polymerization in view of producing a copolymer having a melt index that is excellent in moldability.

Continuous bulk polymerization is a polymerization method in which a monomer component and a polymerization initiator are continuously fed into a reaction vessel, and a partial polymer obtained by the retention of components in the reaction vessel for a predetermined time is continuously discharged. Continuous bulk polymerization can lead to the production of polymers with high productivity.

The polymerization temperature at the time of the continuous bulk polymerization is not limited, but it may be 120 to 160 ° C, and the residence time of the reactor may be 0.5 to 5 hours.

The polymerization initiator used in the continuous bulk polymerization is not particularly limited. Specific examples thereof include azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanenitrile, 1,1'-azobis (1-acetoxy-1-phenylethane), dimethyl 2,2 ' Azo compounds such as azobisisobutyrate, 4,4'-azobis-4-cyanovalerate and the like; Benzoyl peroxide, lauroyl peroxide, acetyl peroxide, caprylyl peroxide, 2,4-dichlorobenzoyl peroxide, isobutyl peroxide, acetyl cyclohexylsulfonyl peroxide, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-butyl peroxy-2-ethylhexanoate, 1,1-di (t-butylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, isopropyl peroxydicarbonate, Butyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butyl peroxydicarbonate, isopropyl peroxydicarbonate, isobutyl peroxydicarbonate, Amyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1,1,2-trimethylpropylperoxy-2-ethylhexanoate Butyl peroxy allyl carbonate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyisopropyl carbonate, t- , 1,1,3,3-tetramethylbutylperoxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy isononano Organic peroxides such as 1,1,2-trimethylpropyl peroxy isononanoate, t-butyl peroxybenzoate, and the like. One type of polymerization initiator may be used, or two or more types of polymerization initiators may be used. The initiator is preferably included in an amount of 0.02 to 0.05 part by weight based on 100 parts by weight of the total monomer. It is preferable to obtain the desired molecular weight within the above range and to control the reaction heat of the reactor.

A chain transfer agent may also be used as needed in the continuous bulk polymerization of the present invention. The chain transfer agent is not particularly limited. For example, n-propylmercaptane, isopropylmercaptan, n-butylmercaptan, t-butylmercaptan, n-hexylmercaptan, n-octylmercaptan, n-dodecylmercaptan, Mercaptans such as mercaptan, 2-ethylhexyl thioglycolate, phenyl mercaptan, thiocresol, ethylene thioglycol and the like are preferable. One kind of chain transfer agent may be used, or two or more kinds of chain transfer agent may be used. The content may be 0.01 to 1.0 part by weight based on 100 parts by weight of the total weight of the monomers, but is not limited thereto.

Further, if necessary, various additives commonly used in the art, for example, plasticizers, antioxidants, UV stabilizers, heat stabilizers, and the like may be further added as needed during the production of the acrylic polymer. At this time, the additives may be contained in an appropriate amount within a range that does not impair the physical properties of the acrylic polymer. For example, the additives may be included in an amount of about 0.1 to 5 parts by weight based on 100 parts by weight of the whole monomer.

The methacrylate copolymer produced by the continuous bulk polymerization according to an embodiment of the present invention may have a polymerization conversion rate of 40 to 55% and is preferably, but not necessarily, superior in productivity within the above range. The polymerization conversion means the total solid content due to the conversion of the monomer.

In addition, the methacrylate copolymer of the present invention is suitable for application to a light guide plate having a weight average molecular weight of 110,000 to 150,000 g / mol, but is not limited thereto.

In addition, the methacrylate copolymer of the present invention is advantageous for molding into a light guide plate in a range of a melt index of 7 to 15 g / 10 min measured at 230 캜 and 3.8 kg, but is not limited thereto.

In one embodiment of the present invention, the light guide plate may be manufactured by an extrusion or injection method. In addition to the methacrylate copolymer, an additive may be further included if necessary. As the additive, various additives such as a release agent, a heat stabilizer, a light diffusing agent, an ultraviolet absorber, an antioxidant, and a photostabilizer may be contained as long as the effect of the present invention is not impaired. When the additive is added to the composition, it is preferable to add the additive so that the content of the methacrylate copolymer relative to the total amount of the composition is 95 to 99.9 wt%.

As the release agent, for example, higher fatty acid esters, higher aliphatic alcohols, higher fatty acids, higher fatty acid amides, higher fatty acid metal salts and the like can be used.

More specifically, the above-mentioned higher fatty acid esters include methyl laurate, ethyl laurate, propyl laurate, butyl laurate, octyl laurate, methyl palmitate, ethyl palmitate, propyl palmitate, butyl palmitate, octyl palmitate , Methyl stearate, ethyl stearate, propyl stearate, butyl stearate, octyl stearate, stearyl stearate, myristyl myristate, methyl behenate, ethyl behenate, propyl behenate, butyl behenate, octyl behenate Saturated fatty acid alkyl esters such as < RTI ID = 0.0 > Unsaturated fatty acid alkyl esters such as methyl oleate, ethyl oleate, propyl oleate, butyl oleate, octyl oleate, methyl linoleate, ethyl linoleate, propyl linolate, butyrylnolate and octyl linolate; There may be mentioned stearic acid monoglyceride, lauric monoglyceride, lauric diglyceride, lauric triglyceride, palmitic monoglyceride, palmitic diglyceride, palmitic triglyceride, stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, behenic monoglyceride, Saturated fatty acid glycerides such as glyceride, behenic triglyceride; Oleic diglycerides, oleic triglycerides, linolenic monoglycerides, linolenic diglycerides, and unsaturated fatty acid glycerides such as linolenic triglycerides.

Specific examples of the above-mentioned higher aliphatic alcohols include saturated fatty (or aliphatic) alcohols such as lauryl alcohol, palmityl alcohol, stearyl alcohol, isostearyl alcohol, behenyl alcohol, myristyl alcohol and cetyl alcohol; Unsaturated fatty (aliphatic) alcohols such as oleyl alcohol, linolyl alcohol and the like.

Specific examples of the above-mentioned higher fatty acids include fatty acids such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, Saturated fatty acids such as 12-hydroxyoctadecanoic acid; Unsaturated fatty acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, cetoleic acid, erucic acid, and ricinoleic acid.

Specific examples of the above-mentioned higher fatty acid amides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide and behenic acid amide; Unsaturated fatty acid amides such as oleic acid amide, linoleic acid amide, and erucic acid amide; And amides such as ethylene-bis-lauric acid amide, ethylene-bis-palmitic acid amide, ethylene-bis-stearic acid amide and N-oleyl stearamide.

Examples of the above-mentioned higher fatty acid metal salts include sodium salts, potassium salts, calcium salts and barium salts of the above-mentioned higher fatty acids.

As the thermal stabilizer, a phosphorus-based thermal stabilizer and an organic disulfide compound can be used. As the phosphorus thermal stabilizer, for example, tris (2,4-di-t-butylphenyl) phosphite, 2- [ [2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphper-6-yl] oxy] Dibenzo [d, f] [1,3,2] dioxaphosperpin-6-yl] oxy] - ethyl (2, ] 2,2-methylenebis (4,6-di-tert-butylphenyl) octylphosphite, bis (2,6-di-tert- butyl- 4-methylphenyl) pentaerythritol diphosphite, and the like.

Examples of the above organic disulfide compound include dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, di-n-butyl disulfide, di- Di-tert-amyl disulfide, dicyclohexyl disulfide, di-tert-octyl disulfide, di-n-dodecyl disulfide, and di-tert-dodecyl disulfide.

In an embodiment of the present invention, the thickness of the light guide plate may be 0.1 to 5 mm, more preferably 0.4 to 3 mm, but is not limited thereto.

In general, when used in a liquid crystal display equipped with an LED light source, a thickness of 2 mm or more, specifically, 2 to 3 mm is required for durability of the light guide plate. The present invention uses a methacrylate copolymer having excellent heat resistance, Not only in thickness, but also in thicknesses less than 2 mm.

A liquid crystal display equipped with an LED light source includes a television, a monitor of a personal computer, a mobile phone, and a liquid crystal screen of a digital camera. The light guide plate of the present invention can be suitably used for a large liquid crystal display equipped with an LED light source such as a television.

Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the following examples and comparative examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

The physical properties of the film were measured by the following measuring method.

1. Glass transition temperature (T _g ): Measured by a differential scanning calorimeter (DSC) at a rate of 10 ° C / min.

2. Weight average molecular weight: The prepared copolymer was dissolved in tetrahydrofuran and measured by gel permeation chromatography (GPC).

The weight average molecular weight was measured using a gel permeation chromatography (GPC) instrument manufactured by Waters. The instrument consisted of a mobile phase pump (M515 Pump), a column heater (ALLCOLHTRB), a detector (2414 RI Detector) and an injector (2695 EB automatic injector). The analytical column used was Styragel HR from WATERS. (PMMA) American polymer standard corporation STD. As the mobile phase solvent, HPLC grade tetrahydrofuran (THF) is used and the column heater temperature is 40 ° C and the mobile phase solvent flow rate is 1.0 mL / min. The resin prepared for the sample analysis was dissolved in tetrahydrofuran (THF), a mobile phase solvent, and injected into a GPC machine to measure the weight average molecular weight.

3. Melt Index

According to ASTM 1238 method, the weight of a resin sample was measured by extruding it from an orifice having a constant inner diameter at 230 캜 and a load of 3.8 kg for 10 minutes.

4. Polymerization Conversion

After the polymerization, 5 g of the sample was completely dissolved in 20 g of acetone to prepare a solution. The solution was slowly added dropwise to 200 g of methanol again, followed by non-solvent treatment. The total weight of the dripped solution was measured, and the weight of unreacted monomer in the weight of the dripped solution was calculated as follows.

Weight of unreacted monomer = total weight of solution dripped × (5/20)

The solution dropped on the methanol was filtered to obtain a solid polymer. The polymer was vacuum-dried at 120 DEG C for 24 hours, and its weight was measured to determine the solid content.

The polymerization conversion ratios were calculated as follows.

(%) = (Weight of solid content / weight of unreacted monomer) x 100

5. Water Absorption Rate

It was measured according to the KSM ISO 62 method. The specimens were prepared in 5 cm width and 5 cm length and 3 mm thickness, respectively, and immersed in pure water.

Water absorption rate = (weight before immersion after immersion) / weight before immersion × 100

6. High temperature and high expansion rate

A light guide plate having a width of 95 cm, a length of 55 cm and a thickness of 3 mm produced by extrusion was evaluated in terms of the initial length by measuring the amount of expansion after 24 hours under the conditions of 60 ° C and 90% RH in a closed chamber.

High temperature and high humidity expansion rate = (initial transverse length after processing) / initial transverse length x 100

The transverse length after the treatment means the transverse length of the specimen measured after 24 hours at 60 ° C and 90% RH.

7. Long-light transmittance

Specimens of 150 mm width, 80 cm length, and 4 mm thickness produced by extrusion were measured by ISO 13468-1 method.

[Example 1]

0.03 part by weight of tert-butyl peroxy-2-ethylhexanoate (Luperox 26) as an initiator was added to 100 parts by weight of a monomer mixture solution containing 70% by weight of methyl methacrylate, 20% by weight of styrene and 10% And 0.2 part by weight of n-octanoylmercaptan were added to prepare a polymerization solution.

The prepared polymerization solution was retained at a temperature of 140 캜 for 2 hours to carry out copolymerization.

Thereafter, the unreacted monomers were removed while staying in a twin-screw extruder at 250 DEG C for 10 minutes, and a methacrylate copolymer in the form of pellets was prepared. The conversion rate was 42%.

The pellets were extruded through an extruder (German blower) at a temperature of 250 ° C. to prepare specimens. Physical properties of the specimens were shown in Table 1 below.

[Examples 2 to 7]

A methacrylate copolymer in the form of pellets was prepared in the same manner as in Example 1, except that the kind and content of monomers were changed as shown in Table 1 below. Specimens were prepared using the same, Respectively.

[Comparative Examples 1 and 2]

A methacrylate copolymer in the form of pellets was prepared in the same manner as in Example 1, except that the kind and content of monomers were changed as shown in Table 1 below. Specimens were prepared using the same, Respectively.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Monomer
Furtherance MMA 70 70 70 70 70 70 70 97 70 SM 20 23 25 27 20 20 24 - 30 AMS 10 7 - - 5 5 - - - MAH - - 5 - 5 - 3 - - CHMI - - - 3 - 5 3 - - MA - - - - - - - 3 - Reaction temperature (캜) 140 140 150 150 140 140 140 170 150
Suzy
Properties

Tg (占 폚)  113 112 114 113 112 113 116 112 106 Weight average molecular weight 132,000 134,000 142,000 139,000 135,000 140,000 141,000 116,000 125,000 MI 7.6 7.3 8.6 8.1 8.5 8.6 8.7 2.3 8.4 Conversion Rate (%) 42 45 49 48 48 48 49 53 50 Water Absorption Rate (%) 0.19 0.2 0.19 0.19 0.18 0.16 0.14 0.29 0.23 High temperature and high expansion rate (%) 0.28 0.29 0.29 0.27 0.25 0.24 0.22 0.45 0.33 Long-light transmittance (%) 88.0 88.1 87.9 87.7 88.0 87.5 86.4 89.5 87.5

MMA: methyl methacrylate

SM: Styrene

AMS: alpha methyl styrene

MAH: Maleic anhydride

CHMI: cyclohexylmaleimide

MA: methyl acrylate

As shown in Table 1, in Examples 1 to 7, the heat resistance was superior to that of Comparative Examples 1 and 2, the water absorption rate was low, and the high temperature and high humidity expansion rate was low. Further, as shown in Examples 3, 4 and 7, by using any one selected from maleic anhydride and N-cyclohexylmaleimide or a mixture thereof, the heat resistance can be further improved even by using a smaller amount of the comonomer .

Claims (10)

A copolymer of 65 to 80% by weight of methyl methacrylate, 15 to 25% by weight of styrene and 5 to 10% by weight of a comonomer,
Wherein the comonomer is at least one aromatic vinyl compound selected from a-methylstyrene, m-methylstyrene, p-methylstyrene and p-methoxystyrene;
An acid anhydride monomer represented by the following formula (1);
[Chemical Formula 1]

In the above formula, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
One or more imide compound selected from N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-cyclohexylmaleimide; Or a mixture of two or more thereof,
A methacrylate copolymer for a light guide plate having a glass transition temperature of 110 ° C or higher and a moisture absorption rate according to KS M ISO 62 of 0.2% or less. delete The method according to claim 1,
Wherein the methacrylate copolymer is produced by continuous bulk polymerization. The method of claim 3,
Wherein the methacrylate copolymer has a polymerization conversion of 40 to 55%. The method according to claim 1,
Wherein the methacrylate copolymer has a weight average molecular weight of 110,000 to 150,000 g / mol. The method according to claim 1,
Wherein the methacrylate copolymer has a melt index of 7 to 15 g / 10 minutes measured at 230 캜 and 3.8 kg. A light guide plate comprising a methacrylate copolymer according to any one of claims 1 to 6. 8. The method of claim 7,
Wherein the light guide plate is used in a liquid crystal display equipped with an LED light source. 8. The method of claim 7,
Wherein the light guide plate has a long-light transmittance of 85% or more according to ISO 13468-1. 8. The method of claim 7,
Wherein the light guide plate has a high temperature and high humidity expansion rate measured after 24 hours at 60 DEG C and 90% RH of 0.3% or less.