KR20120050069A - Composition for resin type light guide panel, backlight unit comprising the light guide panel manufactured by thereof and liquid crystal display including the backlight unit - Google Patents

Abstract

PURPOSE: A composition for light guide plate, a backlight unit including the light guide plate formed by using thereof, and a liquid crystal display equipped with the backlight unit are provided to reduce hardening shrinkage and enhance adhesive force. CONSTITUTION: A composition for light guide plate comprises at least one of silane compound which is selected from a group consisting of compounds which are represented by chemical formula 1 and 2, urethane-(meth)acrylate oligomer and acryl-based monomer which has a maximum shrinkage ratio of 15% or less, and a photo initiator. The silane compound is included 1-10 parts by weight based on 100 parts by weight of the composition for light guide plate.

Description

Composition for resin type light guide panel, backlight unit comprising the light guide panel manufactured by approximately and liquid crystal display including the backlight unit}

The present invention relates to a resin light guide plate composition, a backlight unit including the light guide plate formed thereon, and a liquid crystal display device including the backlight unit.

Liquid crystal display devices are used in various fields such as TVs, outdoor electronic displays, as well as notebook PCs and monitors due to their small size, light weight, and low power consumption. The liquid crystal display device includes a liquid crystal panel and a backlight unit. The backlight unit provides light to the liquid crystal panel, and the light passes through the liquid crystal panel. In this case, the liquid crystal panel displays an image by adjusting the light transmittance. The backlight unit is classified into an edge type and a direct type according to the shape of the light source. In the edge type, the light source is disposed on the side of the liquid crystal panel, the light guide plate is disposed on the rear side of the liquid crystal panel, and guides the light provided from the side of the liquid crystal panel to the rear side of the liquid crystal panel. In contrast, the direct type is provided with a plurality of light sources on the back of the liquid crystal panel, and the light emitted from the plurality of light sources is provided directly to the back of the liquid crystal panel. As the light source, EL (Electro Luminescence), CCFL (Cold Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), Light Emitting Diode (LED) and the like are used. Among these, light emitting diodes have low power consumption and excellent luminous efficiency, and thus their use is increasing.

1 is a view showing the structure of a backlight unit of an edge type light emitting diode. As shown in the figure, when the light emitting diode is applied in an edge type, the light emitting diode 30 is mounted on the printed circuit board 10 and fixed to the side of the light guide plate 40 -A. The light guide plate 40 -A diffuses the light incident from the plurality of light emitting diodes 30 into the liquid crystal panel by spreading the light guide plate 40 -A evenly through a large area of the light guide plate 40 -A by a plurality of total reflections. Provide a surface light source. The reflector 20 is positioned on the rear surface of the light guide plate 40 -A, and reflects light passing through the rear surface of the light guide plate 40 -A toward the liquid crystal panel to improve the brightness of the light. However, this edge type is difficult to apply local dimming, that is, part of the lamp to turn off the lamp of the unnecessary part.

2 is a diagram illustrating a structure of a backlight unit of a direct type light emitting diode. As shown in FIG. 2, when the light emitting diode is applied in a direct type, the light emitting diode 30 may be formed on the front surface of the printed circuit board 10 and the reflecting plate 20 to partially turn on / off the light emitting diode. Dimming is possible. However, it is difficult to effectively apply the effect of reducing the power consumption of locale dimming because the number of light emitting diodes 30 is increased for uniformity of brightness.

In order to solve the above problems, a modular backlight structure having a mixture of an edge type and a direct type has been proposed. The modular backlight unit has an edge type structure, but like the direct type structure, the LED package 30 is regularly formed on the front surface of the printed circuit board 10 and the reflecting plate 20 to reduce the number of light emitting diodes and maintain the effect of local dimming. It is possible to implement. However, the light guide plate is required to evenly distribute the light generated from the light emitting diodes to the side, but there is a problem that the light guide plate cannot be mounted on the front surface of the printed circuit board.

An object of the present invention to solve the above problems is to form a light guide plate that can be applied to a modular backlight unit having excellent adhesion to the substrate and less shrinkage of the local dimmable by a simple curing method, the resin light guide plate capable of forming a thick film A composition, a backlight unit including a light guide plate formed therefrom, and a liquid crystal display device including the backlight unit are provided.

The present invention to achieve the above object,

At least one silane compound selected from the group consisting of compounds represented by Formulas 1 and 2 below; Urethane- (meth) acrylate oligomers prepared by reacting a compound prepared by reacting a divalent polyol with a divalent isocyanate with a (meth) acrylate monomer containing a hydroxy group; Acrylic monomers having a maximum shrinkage ratio of 15% or less; And it provides a resin light guide plate composition comprising a photoinitiator.

<Formula 1>

<Formula 2>

또는

이며, n 및 m은 각각 독립적으로 1 내지 10의 정수이고, R₅ 은 탄소수 1 내지 10의 알킬렌 또는 페닐렌이다.)In Formulas 1 and 2, each R ₁ is independently an alkyl group or a phenyl group having 1 to 10 carbon atoms, and R ₂ is a single bond or includes or does not include-(C═O) O— in the middle or at the end of a chain. Alkylene having 5 to 5, R ₃ is hydrogen or a methyl group, R ₄ is alkylene having 1 to 15 carbon atoms with or without-(C = O) O- in the middle or at the end of the chain,

or

N and m are each independently an integer of 1 to 10, R ₅ is alkylene or phenylene having 1 to 10 carbon atoms.)

<Equation 1>

Maximum Shrinkage (%) = -2.58 + 3000 * [(meth) acrylic functional group number of said acrylic monomer / molecular weight of said acrylic monomer]

The silane compound may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate.

The number average molecular weight of the urethane- (meth) acrylate oligomer may be 2,000 to 5,000.

The urethane- (meth) acrylate oligomer may be included in an amount of 10 to 70 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate.

The acrylic monomer may be included in 10 to 60 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate.

The resin light guide plate composition may further include a hydrogen bond type (meth) acrylate including a hydroxyl group or a carboxyl group.

The hydrogen bond type (meth) acrylate may include at least one selected from the group consisting of compounds represented by the following Chemical Formulas 4 and 5.

&Lt; Formula 4 >

In Formula 4, R ₁ Is a single bond, alkylene or heteroalkylene having 1 to 10 carbon atoms, cycloalkylene having 3 to 8 carbon atoms, phenylene, alkylphenylene having 1 to 10 carbon atoms, phosphorus, alkoxyphosphonoyl group having 1 to 10 carbon atoms, or Phosphinicosuccinic Nikko group and, R ₂ is H when R ₁ is a single bond, a hydroxy group or a carboxyl group when R ₁ is not a single bond, R ₃ is hydrogen or a methyl group. )

<Formula 5>

(Formula 5, R ₁ Is a C1-C10 alkyl group or heteroalkyl group, a C3-C8 cycloalkyl group, a phenyl group, a C1-C10 alkylphenyl group, R <_3> is hydrogen or a methyl group. )

The hydrogen bond type (meth) acrylate may be an acid-modified (meth) acrylate oligomer formed by reaction of an acid anhydride with a (meth) acrylate monomer containing a hydroxy group.

The acid-modified (meth) acrylate oligomer may include at least one selected from the group consisting of compounds represented by the following Chemical Formulas 6a to 6f.

<Formula 6a>

<Formula 6b>

<Formula 6c>

<Formula 6d>

<Formula 6e>

<Formula 6f>

,

,

,

또는

에서 선택되며, 상기 n 은 1 내지 10 의 정수이며, R₃는 각각 독립적으로 수소, 탄소수 1 내지 10 의 포화 또는 불포화알킬기, 헤테로알킬기, 벤질기, 카르복실기기, 히드록시기 또는 할로겐 원소에서 선택되며, R₄는 탄소수 1 내지 10 의 포화 또는 불포화알킬렌기이다.)In Formulas 6a to 6f, R ₁ are each independently hydrogen or a methyl group, and R ₂ is each independently

,

,

,

or

N is an integer of 1 to 10, R ₃ is each independently selected from hydrogen, a saturated or unsaturated alkyl group of 1 to 10 carbon atoms, heteroalkyl group, benzyl group, carboxyl group, hydroxy group or halogen element, R ₄ is a saturated or unsaturated alkylene group having 1 to 10 carbon atoms.)

The hydrogen bond type (meth) acrylate may be included in 10 to 60 parts by weight based on 100 parts by weight of the total composition.

The resin type light guide plate composition may include two or more kinds of the acrylic monomer, and in this case, the maximum shrinkage rate calculated by Equation 2 may be 3 to 7%.

<Formula 2>

Max Shrinkage (%) =

(In Formula 2, i represents the number of acryl-type monomers contained in the said resin type light-guide plate composition, and each acryl-type monomer is called nth monomer, regardless of the order contained,

XnSn represents the product of Xn and Sn,

Xn represents the mass fraction of the nth monomer,

Sn represents the maximum shrinkage of the n-th monomer and is calculated by Equation 1 above.)

The resin light guide plate composition may further include an ultraviolet stabilizer or a heat stabilizer.

In order to achieve the other object of the present invention,

Light emitting diodes; And it provides a backlight unit comprising a light guide plate formed on the reflecting plate with the composition for the resin light guide plate of the present invention so that the light emitting diode is covered.

The thickness of the light guide plate may be 0.2 to 2 mm.

In order to achieve another object of the present invention, the present invention,

A liquid crystal display device having the backlight unit is provided.

The composition of the present invention is not only hardening shrinkage and excellent adhesion but also no change in color coordinates.

The composition of the present invention can form a thick film of 1 mm or more, it is possible to form a light guide plate for converting the point light source into a surface light source by a simple curing method by applying the composition of the present invention irrespective of the position of the light emitting diode.

The composition of the present invention can be used to form a light guide plate in a local dimmable modular backlight structure in which an edge type and a direct type are mixed.

1 is a view showing the structure of a backlight unit of an edge type light emitting diode.
2 is a diagram illustrating a structure of a backlight unit of a direct type light emitting diode.
3 is a view illustrating the structure of a modular light emitting diode backlight unit in which an edge type and a direct type are mixed according to an embodiment of the present invention.
4 is a photograph showing a state of light emission in a state in which a light guide plate is not formed of a resin light guide plate composition in a light emitting diode package.
5 is a photograph showing a state of light emission in a state where a light guide plate is formed of a resin light guide plate composition.

Hereinafter, the present invention will be described in detail so that those skilled in the art can easily practice.

The present invention is a silane compound; Urethane- (meth) acrylate oligomers; Acrylic monomers; And it provides a resin light guide plate composition comprising a photoinitiator. In addition, the composition for a resin light guide plate of the present invention may further include a hydrogen bond type (meth) acrylate.

The resin-type light guide plate composition of the present invention has a very good adhesion due to the silane compound, the shrinkage rate is small, and can form a thick film to cover the light emitting diode in the local dimmable edge type backlight unit mixed edge type and direct type. The light guide plate can be formed.

The silane compound serves to improve the adhesion of the resin light guide plate composition of the present invention.

The silane compound may be at least one selected from the group consisting of compounds represented by the following Chemical Formulas 1 and 2.

<Formula 1>

<Formula 2>

또는

이며, n 및 m은 각각 독립적으로 1 내지 10의 정수이고, R₅ 은 탄소수 1 내지 10의 알킬렌 또는 페닐렌이다.)In Formulas 1 and 2, each R ₁ is independently an alkyl group or a phenyl group having 1 to 10 carbon atoms, and R ₂ is a single bond or includes or does not include-(C═O) O— in the middle or at the end of a chain. Alkylene having 5 to 5, R ₃ is hydrogen or a methyl group, R ₄ is alkylene having 1 to 15 carbon atoms with or without-(C = O) O- in the middle or at the end of the chain,

or

N and m are each independently an integer of 1 to 10, R ₅ is alkylene or phenylene having 1 to 10 carbon atoms.)

The silane compound may be included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate. When the silane compound is included in less than 1 part by weight, it is difficult to realize sufficient adhesive strength, and when included in more than 10 parts by weight, the compatibility decreases.

The urethane- (meth) acrylate oligomers not only control shrinkage but also have excellent transparency and mechanical properties.

The urethane- (meth) acrylate oligomer may be prepared by reacting a compound prepared by reacting a divalent polyol with a divalent isocyanate with a (meth) acrylate monomer containing a hydroxyl group. That is, the divalent polyol may be prepared by reacting with an excess divalent isocyanate to prepare a compound having an isocyanate end group and reacting it with a (meth) acrylate monomer containing a hydroxyl group.

It is preferable that the divalent polyol has a number average molecular weight of 1500 or more, and specifically, polyester polyol, polycaprolactone modified polyol, polycarbonate polyol, polybutadiene polyol, polyisophorene polyol, polyethylene glycol, polypropylene glycol , Polyethylene-propylene glycol and polytetramethylglycol may be used alone or a mixture thereof, but is not limited thereto.

Specific examples of the divalent isocyanate include toluene-2,4-diisocyanate and isomers thereof, xylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, 2,2-bis -4'-propane isocyanate, 6-isopropyl-1,3-phenyldiisocyanate, bis (2-isocyanate ethyl) -fumarate, 1,6-hexanediisocyanate, 4,4'-biphenylene diisocyanate, 3 , 3'-dimethylphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-phenylenedi isocyanate, 1,5-naphthalene diisocyanate, 1,4 -Xylene diisocyanate, 1,3-xylene diisocyanate and 4,4'-dicyclohexyl methane diisocyanate alone or mixtures thereof 2,4-toluene diisocyanate and isomers thereof, isophorone diisocyanate, 1,5-naphthalenedi isocyanate, 1,4-xylene diisocyanate, 1,3-xylene diisocyanate, 4, It can be used alone or a mixture thereof selected from the group consisting of 4-dicyclohexyl methane diisocyanate and 1,6-hexamethylene diisocyanate, but is not limited thereto.

Specific examples of the (meth) acrylate monomer containing a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and caprolactone Modified (meth) acrylate, polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate may be used alone or a mixture thereof selected from the group consisting of, but is not limited thereto.

A catalyst may be used to improve reactivity in the process of preparing the urethane- (meth) acrylate oligomer, and a polymerization inhibitor may be used to improve reaction stability and storage stability. The catalyst is specifically triethylamine, triethanolamine, 1,4-diazabiscyclo- (2,2,2) -octane, N, N-diethylcyclohexylamine, N-methylmorpholine, N, N Tertiary amines such as, N ', N'-tetramethyl-methanediamine or dibutyltindilaurate, dibutyltindibutoxide, di- (2-ethylhexyl) tinoxide, dibutyltindiisooctyl maleate, di One or more types of tin-based catalysts such as butyl tin bis- (acetylacetonate), butyl tin trichloride, tributyl tin cyanate can be selected and used, and preferably dibutyl tin dilaurate may be used. The said polymerization inhibitor can use a small amount of phenol type polymerization inhibitors, such as methoxy hydroquinone, hydroquinone, and t-butyl hydroquinone.

The urethane- (meth) acrylate oligomer may be represented by the following Chemical Formula 3:

<Formula 3>

,

,

,

또는

이며, 상기 n 은 각각 독립적으로1 내지 10 의 정수이며, 상기 R₄는 수소 또는 메틸기이다. In Formula 3, R ₁ means a structure excluding the terminal hydroxyl group in the divalent polyol, R ₂ means a structure excluding the terminal isocyanate group from the divalent isocyanate, wherein R ₃ is

,

,

,

or

N is each independently an integer of 1 to 10, and R ₄ is hydrogen or a methyl group.

The urethane- (meth) acrylate oligomer may have a number average molecular weight of 2,000 to 5,000. When the molecular weight is less than 2,000, the curing shrinkage may be increased, and when the molecular weight is more than 5,000, the viscosity of the resin light guide plate composition may be increased to reduce workability.

The urethane- (meth) acrylate oligomer may be included in an amount of 10 to 70 parts by weight, and preferably 20 to 60 parts by weight, based on 100 parts by weight of the total composition for the resin light guide plate. If it is included in less than 10 parts by weight, the mechanical properties of the adhesive after curing may be lowered, and when included in excess of 70 parts by weight, the adhesive force is lowered and the viscosity may be high and workability may be lowered.

The hydrogen bond type (meth) acrylate may form an ionic bond with the substrate or dissolve a portion of the substrate to impart adhesion to the physical bond.

The hydrogen bond type (meth) acrylate can be used without limitation as long as it can form a hydrogen bond, preferably (meth) acrylate containing a hydroxy group or a carboxyl group can be used.

The hydrogen bond type (meth) acrylate may preferably include at least one selected from the group consisting of compounds represented by the following Chemical Formulas 4 and 5.

&Lt; Formula 4 >

In Formula 4, R ₁ Is a single bond, alkylene or heteroalkylene having 1 to 10 carbon atoms, cycloalkylene having 3 to 8 carbon atoms, phenylene, alkylphenylene having 1 to 10 carbon atoms, phosphorus, alkoxyphosphonoyl group having 1 to 10 carbon atoms, or Phosphinicosuccinic Nikko group and, R ₂ is R ₁ is and when is a single bond H, R a hydroxyl group or a carboxyl group, if _one is not a single bond and R ₃ is hydrogen or a methyl group. )

<Formula 5>

(Formula 5, R ₁ Is a C1-C10 alkyl group or heteroalkyl group, a C3-C8 cycloalkyl group, a phenyl group, a C1-C10 alkylphenyl group, R <_3> is hydrogen or a methyl group. )

Specific examples of the (meth) acrylate having a hydroxy group introduced therein among the hydrogen bond type (meth) acrylates represented by Formula 4 include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone modified (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, phosphoric acid (meth) acrylate, and the like, and carboxyl group Specific examples of the (meth) acrylate to which is introduced are (meth) acrylic acid and the like.

The hydrogen bond type (meth) acrylate represented by Formula 5 may be prepared by reacting a monomer having an epoxy functional group with (meth) acrylic acid. Although the number of the said epoxy functional groups is preferable monofunctional, when molecular weight is large, polyfunctional may be sufficient. Specific examples of the monomer having an epoxy functional group include ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and phenol glycidyl ether. , Nonylphenol glycidyl ether, polybisphenol A diglycidyl ether, polybisphenol F diglycidyl ether, polybisphenol S diglycidyl ether, polybisphenol AD diglycidyl ether, and the like may be used. It is not limited. A catalyst may be used in the reaction of the monomer having the epoxy functional group with (meth) acrylic acid. As the catalyst, tertiary amine-based, quaternary ammonium salt-based, inorganic alkali salt-based and phosphorus-based catalysts may be used. Specifically, triethylamine, pyridine, trimethylamine, tributylamine, triethylamine benzyl chloride, triethylamine Benzyl bromide, tributylamine benzyl chloride, tributylamine benzyl bromide, tetrabutylamine chloride, tetrabutylamine bromide, triphenylphosphine, chromium octate and the like may be used, but is not limited thereto.

The hydrogen bond type (meth) acrylate may be an acid-modified (meth) acrylate oligomer formed by the reaction of an acid anhydride and a (meth) acrylate monomer containing a hydroxy group in the presence of a catalyst. The acid anhydride is preferably a cyclic acid anhydride, and the (meth) acrylate monomer containing the hydroxy group is specifically 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4 Hydroxybutyl (meth) acrylate, caprolactone modified (meth) acrylate, polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate alone or mixtures thereof may be used. However, the present invention is not limited thereto. As the catalyst, tertiary amine-based, quaternary ammonium salt-based, inorganic alkali salt-based and phosphorus-based catalysts may be used. Specifically, triethylamine, pyridine, trimethylamine, tributylamine, triethylamine benzyl chloride, triethylamine Benzyl bromide, tributylamine benzyl chloride, tributylamine benzyl bromide, tetrabutylamine chloride, tetrabutylamine bromide, triphenylphosphine, chromium octate, etc. may be used, but is not limited thereto.

Preferably, the acid-modified (meth) acrylate oligomer may include at least one selected from the group consisting of compounds represented by the following Chemical Formulas 6a to 6f.

<Formula 6a>

<Formula 6b>

<Formula 6c>

<Formula 6d>

<Formula 6e>

<Formula 6f>

,

,

,

또는

에서 선택되며, 상기 n 은 1 내지 10 의 정수이며, R₃는 각각 독립적으로 수소, 탄소수 1 내지 10 의 포화 또는 불포화알킬기, 헤테로알킬기, 벤질기, 카르복실기기, 히드록시기 또는 할로겐 원소에서 선택되며, R₄는 탄소수 1 내지 10 의 포화 또는 불포화알킬렌기이다.)In Formulas 6a to 6f, R ₁ are each independently hydrogen or a methyl group, and R ₂ is each independently

,

,

,

or

N is an integer of 1 to 10, R ₃ is each independently selected from hydrogen, a saturated or unsaturated alkyl group of 1 to 10 carbon atoms, heteroalkyl group, benzyl group, carboxyl group, hydroxy group or halogen element, R ₄ is a saturated or unsaturated alkylene group having 1 to 10 carbon atoms.)

The hydrogen bond type (meth) acrylate may include at least one selected from the group consisting of compounds represented by Formulas 4, 5, 6a to 6f, as necessary. The hydrogen bond type (meth) acrylate may be included in an amount of 10 to 60 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the total composition for the resin light guide plate. When the hydrogen bond type (meth) acrylate is included in less than 10 parts by weight, the viscosity of the entire composition may be increased workability and adhesion may be lowered, when included in more than 60 parts by weight, the viscosity is lowered light emitting diode package It may not cover, and compatibility may be inferior.

The acrylic monomer serves to lower the viscosity of the composition for workability without affecting the physical properties of the composition.

The acrylic monomer can be used that the maximum shrinkage of the formula 1 is 15% or less, preferably, the maximum shrinkage of 3 to 10% can be used. If the maximum shrinkage is less than 3%, the reactivity is too low to increase the degree of cure, and if the maximum export rate exceeds 10%, the cure rate is fast but the degree of cure is difficult to realize sufficient physical properties. However, the maximum shrinkage rate may not have a value smaller than zero in meaning.

<Equation 1>

Maximum shrinkage percentage (%) = -2.58 + 3000 * [(meth) acrylic functional group number of the said acrylic monomer / molecular weight of the said acrylic monomer]

The maximum shrinkage rate of Equation 1 is shown on the assumption that the degree of curing is 100%.

Typically, the shrinkage ratio may be expressed as the ratio of specific gravity before curing and specific gravity difference after curing, as shown in Formula A, but the shrinkage ratio can be easily estimated using Equation 1, and the product of the maximum shrinkage ratio and the degree of curing of Formula 1 is shown in Formula A below. It shows the same result as the shrinkage ratio of.

<Formula A>

Shrinkage (%) = {(specific gravity before cure-specific gravity after cure) / (specific gravity before cure)} × 100

The acrylic monomer having a maximum shrinkage of 15% or less specifically includes 2-phenoxyethyl acrylate (13%), cyclic trimethylolpropane foam acrylate (12.4%), tridecyl acrylate (9.2%), and octyldecyl acryl. Rate (12.6%), isobornyl acrylate (11.8%), 2- (2-ethoxyethoxy) ethyl acrylate (13.4%) isodecyl acrylate (11.6%), caprolactone acrylate (6.1%), Lauryl acrylate (9.9%), stearic acrylate (6.7%), methoxy polyethylene glycol 600 monoacrylate (2.1%), nonylphenol ethylene oxide (4 mol) acrylate (4.1%), nonylphenol ethylene oxide (8 moles) acrylate (2.2%), methoxy polyethylene glycol 600 monoacrylate (1.8%), isodecyl methacrylate (10.7%), stearic methacrylate (6.3%), 2-phenoxyethyl meth Acrylate (12%), isobornyl methacrylate (11%), tridecyl methacrylate (8.6%) and the like can be used.

The acrylic monomer may be included in 10 to 60 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate, preferably 20 to 50 parts by weight. When included in less than 10 parts by weight of the resin-type light guide plate composition may have a high coating properties and the appearance may have a problem, when included in more than 60 parts by weight may reduce the mechanical properties and adhesion.

The photoinitiator serves to change the liquid resin into a solid phase by light irradiation.

The photoinitiator includes a type 1 initiator and a tertiary amine in which a radical is generated by decomposition of a molecule due to a difference in chemical structure or molecular binding energy, and a hydrogen decyclic type 2 initiator. Specific examples of the type 1 initiator include 4-phenoxydichloroacetphenone, 4-t-butyldichloroacetphenone, 4-t-butyltrichloroacetphenone, diethoxyacetphenone, 2-hydroxy-2-methyl -l-phenylpropane-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-l-one, 1- (4-dodecylphenyl) -2-hydroxy-2 Acetphenones such as -methylpropan-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, and 1-hydroxycyclohexylphenyl ketone, benzoin, benzo Benzoin, such as phosphine ether, benzoin ethyl ether, benzyl dimethyl ketal, an acyl phosphine oxide, a titanocene compound, etc. are mentioned. Specific examples of the type 2 initiator include benzophenone, benzoyl benzoic acid, benzoyl benzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzol-4'-methyldiphenyl sulfide, 3,3 Such as benzophenones such as' -methyl-4-methoxy benzophenone, thioxanthone, 2-chlorothioxanthone, 2-methyl thioxanthone, 2,4-dimethyl thioxanthone and isopropyl thioxanthone Thioxanthone and the like. These photoinitiators can be used individually or in mixture of these, You may use together a 1st type and a 2nd type.

The photoinitiator may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total composition for a resin light guide plate, preferably 0.2 to 3 parts by weight. When the photoinitiator is included in less than 0.2 parts by weight, it is difficult to realize sufficient mechanical properties or adhesive strength due to insufficient curing, and when included in excess of 3 parts by weight, poor adhesion or cracking may occur due to curing shrinkage.

The composition for a resin light guide plate of the present invention may include an ultraviolet stabilizer and a heat stabilizer as necessary.

The UV stabilizer serves to block or absorb UV light to prevent degradation by prolonged UV exposure of the cured composition.

The UV stabilizers are classified into absorbers, quenchers, and hindered amine light stabilizers (HALS) according to functional mechanisms. Depending on the chemical structure, it can be classified into phenyl salicylates (sorbents), benzophenones (sorbents), benzotriazoles (sorbents), nickel derivatives (quenchers), and radical scavengers. Can be. It will not specifically limit, if it is an ultraviolet stabilizer which does not change the initial color of the resin-type light-guide plate composition largely in this invention.

The heat stabilizer may be used both commercially applicable polyphenol-based, phosphite-based, lactone-based. The UV stabilizer and the heat stabilizer may be used by appropriately adjusting the content at a level that does not affect the curability.

The resin-type light guide plate composition of the present invention may be added by adjusting the content according to the needs of those skilled in the art within the range that does not impair the object of the present invention, additives commonly used in the art in addition to the UV stabilizer or heat stabilizer.

The resin-type light guide plate composition of the present invention may include two or more kinds of acrylic monomers, in which case the maximum shrinkage rate represented by the following Formula 2 may be 3 to 7%. By the following formula 2, the maximum shrinkage rate when several types of acrylic monomers are mixed can be calculated.

<Formula 2>

Max Shrinkage (%) =

In Formula 2, i represents the number of acryl-type monomers contained in the said resin type light-guide plate composition, and each acrylic monomer is called nth monomer, regardless of the order contained, XnSn represents the product of Xn and Sn, and Xn is n The mass fraction of the first monomer is shown, and Sn represents the maximum shrinkage of the nth monomer. In this case, the maximum shrinkage rate of the n-th monomer may be calculated by the formula (1).

When the maximum shrinkage rate is increased, the adhesion decreases, the curing property is faster, and when the maximum shrinkage rate is decreased, the opposite tendency is observed. Curing degree due to UV irradiation shows the same tendency as the shrinkage rate, the composition for resin-type LGP having a maximum shrinkage rate of less than 7% shows a result of 90% or more, and can eliminate curl problems due to post-curing at various high temperature tests.

The present invention also provides a light emitting diode; Provided is a backlight unit including a light guide plate formed on a reflecting plate with the resin type light guide plate composition of the present invention so that the light emitting diode is covered.

3 is a view illustrating the structure of a modular light emitting diode backlight unit in which an edge type and a direct type are mixed according to an embodiment of the present invention.

Referring to FIG. 3, the modular LED backlight unit of the present invention includes a printed circuit board 10; Reflector 20; The light emitting diode 30 and the light guide plate 40 -B may be included. In addition, although not shown in FIG. 3, a diffusion plate, a diffusion film, a light collecting film, a reflective polarizing film, and the like stacked on the upper surface of the light guide plate 40 -B may be further included.

In the modular backlight unit having a mixture of edge type and direct type as shown in FIG. 3, the light emitting diode is distributed on the front surface of the printed circuit board 10 and the reflecting plate 20, making it difficult to mount the light guide plate. Accordingly, the light guide plate 40-B may be formed by applying the resin composition for the light guide plate of the present invention to the upper surface of the reflecting plate 20 flatly or higher than the height of the light emitting diode 30. The light guide plate 40 -B may have a thickness of 0.2 to 2 mm. The light guide plate 40-B plays a role of converting a point light source into a surface light source, and has excellent adhesive strength, small curing shrinkage, and no change in color coordinates.

4 is a photograph showing a state of light emission in a state in which a light guide plate is not formed with a resin light guide plate composition in a light emitting diode package, and FIG. 5 is a photograph showing a state of light emission in a state in which a light guide plate is formed of a resin light guide plate composition. . 4 and 5, the light guide plate formed of the composition of the present invention serves to convert the point light source into a surface light source.

The present invention also provides a liquid crystal display device having the backlight unit. The liquid crystal display device includes a backlight unit including a light guide plate formed of the composition of the present invention.

The liquid crystal display device is also not limited in structure, and may employ a structure known in the art.

The present invention will be further illustrated by the following examples, which are only specific examples of the present invention, and are not intended to limit or limit the protection scope of the present invention.

< Synthetic example  1> urethane- ( Meta ) Acrylate Oligomer  Produce

A 2000 ml glass reactor equipped with a stirrer, heating mantle, cooling tube, and temperature control unit 400 g of polypropylene glycol (average concentration, PPG 2000) with an average molecular weight of 2,000 g, isophorone diisocyanate (Biel, IPDI) 111 g, dibutyl tin di 0.1 g of laurate (Achemy, Fascat 4202) was added to the reactor and the temperature was maintained at 70 ° C. for 3 hours. At this time, the NCO% by the wet analysis method was 4.9%. The reactor temperature was cooled to room temperature, 107.2 g of 2-hydroxyethyl methacrylate (Kognis, 2-HEMA), 71 g of isobonol acrylate (Osaka Yuki, IBXA), 0.7 g of smudgeage (Sumitomo Chemical) , 0.8 g of methoxyhydroquinone (Eastman, HQMME) and 0.2 g of dibutyltin dilaurate (Achemy, Fascat 4202) were added and the reaction was carried out at 75 ° C. for 6 hours, and an isocyanate characteristic peak (2260 cm ⁻¹ ) was obtained. The reaction was terminated when it disappeared completely. At this time, the resin viscosity was 34,000 cps (25 ° C). At this time, the number average molecular weight is 2,700, the maximum shrinkage rate according to the formula 1 is 0.86%,

< Synthetic example  2> urethane- ( Meta ) Acrylate Oligomer  Produce

2000 g glass reactor equipped with a stirrer, heating mantle, cooling tube, and temperature control device 600 g of polytetraethylene glycol (PTOL 3000, Korea Polyol Co., Ltd.), 131 g of hexamethylene diisocyanate (Biel Co., Desmodur W) 0.1 g of butyl tin dilaurate (Achemy, Fascat 4202) was put in a reactor, and the reaction was performed for 3 hours while maintaining the reaction temperature at 70 ° C. At this time, the NCO% by the wet analysis method was 3.5%. The reactor temperature was cooled to room temperature, 107.2 g of 2-hydroxyethyl methacrylate (Cognis Co., 2-HEMA), 93.3 g of isobonol acrylate (Osaka Yuki Co., IBXA), Smilage Phi (Sumitomo Chemical) 0.7 g, methoxyhydroquinone (Eastman, HQMME) 0.8g, dibutyltin dilaurate (Akemi, Fascat 4202) was added to the reaction was carried out for 6 hours at 75 ℃, the isocyanate characteristic peak (2260cm ^-1 ) The reaction was terminated when it disappeared completely. At this time, the resin viscosity was 95,000 cp (25 degreeC). At this time, the number average molecular weight is 3,800, the maximum shrinkage ratio by the formula 1 is 0.28%.

< Synthesis Example 3 > Urethane- ( Meta ) Acrylate Oligomer  Produce

800g polyethylene glycol (Hanong Chemical, PEG 4000 (F)) 800g, isophorone diisocyanate (Biel, IPDI) 111g, dibutyl in 2000ml glass reactor equipped with stirrer, heating mantle, cooling tube, temperature control device 0.1 g of tindilaurate (Achemy, Fascat 4202) was put in a reactor and the reaction was carried out for 3 hours while maintaining the reaction temperature at 70 ℃. At this time, NCO% by wet analysis method was 2.7%. The reaction temperature was cooled to room temperature, 107.2 g of 2-hydroxyethyl methacrylate (Cognis, 2-HEMA), 115.5 g of isobonol acrylate (Osaka Yuki, IBXA), Smilage Phi (Sumitomo Chemical) 0.7 g, methoxyhydroquinone (Eastman, HQMME) 0.8g, 0.2 g of dibutyl tin dilaurate (Akemisa, Fascat 4202) was added and the reaction proceeded at 75 ℃ for 6 hours, the isocyanate characteristic peak (2260cm ^-1 ) The reaction was terminated when it disappeared completely. At this time, the resin viscosity was 125,000 cps (25 ° C). At this time, the number average molecular weight is 4,700, the maximum shrinkage ratio according to the formula 1 is 0.14%.

< Synthetic example  4> Silane  Preparation of compounds

247 g of 3-isocyanatopropyltriethoxysilane (KBM-9007, Cinnetchu) in a 1 L three-necked reactor equipped with a mechanical motor, a cooling tube, a thermometer and a thermostat (FA-2D Daisel Corporation) ) 378g, methoxyhydroquinone (Eastman, HQMME) 0.6g, dibutyltin laurate (Akemi, FASCAT 4202) was added to the reaction after 6 hours at 65 ℃ FT-IR isocyanate characteristic peak 2260cm ^-1 The reaction was terminated when completely disappeared.

< Synthetic example  5> Silane  Preparation of compounds

The reaction was carried out in the same manner as in Synthesis Example 4, except that 370 g of polyethylene glycol monoacrylate (PEA-6, Cognis) was used instead of caprolactone-modified acrylate (FA-2D Daicel).

< Synthetic example  6> Silane  Preparation of compounds

The reaction was carried out in the same manner as in Synthesis Example 4, except that 146 g of 2-hydroxyethyl methacrylate (2-HEMA, Cognis) was used instead of FA-2D.

< Synthetic example  7> Silane  Preparation of compounds

278 g of 3-glycidoxypropyltrimethoxysilane (KBM-403, Synthechu) in a 1 L three-necked reactor equipped with a mechanical motor, cooling tube, thermometer, and thermostat, 86 g of methacrylic acid (LG Chemistry), methoxy hydroquinone ( 0.6 g of Eastman, HQMME) and 0.3 g of triethylamine (Aldrich) were added and the reaction was terminated when the acid value reached 2 mg / g KOH or less after 7 hours of reaction at 80 ° C.

< Synthetic example  8> Silane  Preparation of compounds

It proceeded in the same manner as in Synthesis example 7, except that 72 g of acrylic acid (LG Chemical Company) was used instead of methacrylic acid.

< Synthetic example  9> Silane  Preparation of compounds

It proceeded in the same manner as in Synthesis Example 7 except that 144 g of 2-carboxyethyl acrylate (BETA-CEA, Cytec Co., Ltd.) was used instead of methacrylic acid.

< Example  1 to 11> Preparation of Resin Light Guide Plate Composition

To the resin composition of the light guide plate was prepared by a method known in the art using the resin prepared in the synthesis example in the composition of Table 1. The unit of Table 1 below is g.

Example One 2 3 4 5 6 7 8 9 10 11 Synthesis Example 1 50 50 50 50 50 50 - - 50 50 Synthesis Example 2 - - - - - - 50 - 50 - - Synthesis Example 3 - - - - - - - 50 - - - Synthesis Example 4 5 - - - - - 5 One 10 13 Synthesis Example 5 - 5 - - - - - - - - - Synthesis Example 6 - - 5 - - - - - - - - Synthesis Example 7 - - - 5 - - - - - - - Synthesis Example 8 - - - - 5 - - - - - - Synthesis Example 9 - - - - - 5 - 5 - - - NPEA ^{1 )} 25 25 25 25 25 25 25 25 29 20 17 IBXA ^{2 )} 18 18 18 18 18 18 18 18 18 18 18 Igacure184 ^{3 )} 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Iganox1010 ^{4 )} 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Maximum Shrinkage (%) 5.4 5.9 6.7 4.7 5.1 3.5 5.6 3.8 4.8 6.3 6.8

1) NPEA: Nonylphenol Ethylene Oxide (4mol) Acrylate (Han Thickening, NP-041), Shrinkage 4.1%

2) IBXA: Isobonylacrylate (AGI, TM-2870), shrinkage rate 11.8%

3) Igacure184: 1-hydroxycyclohexylphenyl ketone (BASF Corporation)

4) Iganox 1010: Phenolic Thermal Stabilizer (Shiba Gauge)

< Comparative example  1 to 3> Preparation of Resin Light Guide Plate Composition

To the resin composition of the light guide plate was prepared by a method known in the art using the resin prepared in the synthesis example in the composition of Table 2. The unit of Table 2 below is g.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Synthesis Example 1 50 - - Synthesis Example 2 - 50 - Synthesis Example 3 - - 50 Synthesis Example 4 - - - Synthesis Example 5 - - - Synthesis Example 6 - - - Synthesis Example 7 - - - Synthesis Example 8 - - - Synthesis Example 9 - - - NPEA ^{1 )} 30 30 30 IBXA ^{2 )} 18 18 18 Igacure184 ^{3 )} 1.5 1.5 1.5 Iganox1010 ^{4 )} 0.5 0.5 0.5 Maximum Shrinkage (%) 6.9 7.1 7.3

1) NPEA: Nonylphenol Ethylene Oxide (4mol) Acrylate (Han Thickening, NP-041), Shrinkage 4.1%

2) IBXA: Isobonylacrylate (AGI, TM-2870), shrinkage rate 11.8%

3) Igacure184: 1-hydroxycyclohexylphenyl ketone ( BASF Corporation)

4) Iganox 1010: Phenolic Thermal Stabilizer (Shiba Gauge)

Experimental Example 1 Adhesion Measurement

The composition of the above Examples and Comparative Examples to the structure shown in Figure 4 to the table coating thickness of 1.5 mm and the first curing at 350 mJ / cm ² in a Black Light lamp under a nitrogen atmosphere and then 1 J / cm ² light amount in the metal halide lamp Secondary curing was performed to prepare specimens. Each specimen was subjected to a T test using Instron's UTM. The adhesive force was measured at a rate of 2 mm / min, and the adhesive force between the two types of glass and metal was evaluated using the average value except the maximum and minimum values, and the results are shown in Table 3 below.

< Experimental Example  2> Of color coordinates  Change measurement

The specimen prepared in the same manner as in Experimental Example 1 was separated from the substrate and attached to a glass plate, and the color values of the glass plate and the specimen were measured in a transmission mode using a Spectro color meter SE200 manufactured by Nippon Denshoku Co., Ltd. to obtain ΔE * ab. The results are shown in Table 3 below.

< Experimental Example  3> Hardness and shrinkage measurement

Take the resin part of the specimen prepared in the same manner as in Experimental Example 1 to about 1 g and accurately measure the weight (W _o ), and leave it in 10 g of ethyl acetate solution for 24 hours, and then put the specimen in a 60 ℃ oven 4 After drying time, the weight (W _i ) was measured, and the degree of curing was calculated by the following Equation 3, and the actual shrinkage was calculated by the following Equation 4.

<Formula 3>

Hardness (%) = (W _i / W _o ) × 100

<Equation 4>

Actual shrinkage (%) = {hardness (%) × maximum shrinkage (%) in equation 2} / 100

< Experimental Example  4> Lightfast  Measure

The specimen produced in the same manner as in Experimental Example 1 was left for 100 hours in CT-UVT equipment (UV-B, 280 ~ 360nm) of KOTECH, and the initial value in the transmission mode using the Spectro color meter SE200 of Nippon Denshoku Co., Ltd. After the light resistance test, color values were measured to obtain ΔE * ab. The results are shown in Table 3 below.

ΔE * ab = {(ΔL *) ² + (Δa *) ² + (Δb *) ² } ^1/2

< Experimental Example  5> High temperature and high humidity  evaluation

The specimens were prepared in the same manner as the specimens prepared for the elongation measurement with the compositions of Examples and Comparative Examples in a constant temperature and humidity chamber with a humidity of 60 ° C and 95%, and the difference from the initial color difference value after 500 hours was expressed as ΔE * ab value. . The results are shown in Table 3 below.

Example Comparative Example One 2 3 4 5 6 7 8 9 10 11 One 2 3 Adhesiveness (N) 37 36 32 39 39 41 41 29 27 30 32 24 28 29 Initial color value 0.3 0.4 0.3 0.5 0.4 0.4 0.4 0.4 0.5 0.4 0.5 0.5 0.4 0.5 Hardness (%) 93 90 89 94 95 96 95 90 92 93 90 89 88 87 Shrinkage (%) 5.1 5.6 6 4.4 4.9 3.4 5.6 3.5 4.3 5.9 6.3 6.1 5.8 6.5 Light resistance 4.2 5.1 4.4 5.2 3.7 5.8 4.2 4.4 3.8 4.0 4.2 5.8 6.0 7.2 High temperature and high humidity 2.7 2.5 2.4 1.5 1.8 1.3 1.5 1.3 2.7 2.5 2.3 3.0 3.2 3.1

As shown in Table 3, when the light guide plate was formed using the resin type light guide plate composition of the present invention, not only the adhesive strength was excellent but also the shrinkage rate was small, and the color value was changed even after the light guide plate was formed and left for a long time in ultraviolet light or high temperature and high humidity. Was small.

10: printed circuit board
20: reflector
30: light emitting diode
40-B: Light guide plate

Claims (15)

At least one silane compound selected from the group consisting of compounds represented by Formulas 1 and 2 below;
Urethane- (meth) acrylate oligomers prepared by reacting a compound prepared by reacting a divalent polyol with a divalent isocyanate with a (meth) acrylate monomer containing a hydroxy group;
Acrylic monomers having a maximum shrinkage ratio of 15% or less; And
Resin type light guide plate composition comprising a photoinitiator:
<Formula 1>

<Formula 2>

In Formulas 1 and 2, each R ₁ is independently an alkyl group or a phenyl group having 1 to 10 carbon atoms, and R ₂ is a single bond or includes or does not include-(C═O) O— in the middle or at the end of a chain. Alkylene having 5 to 5, R ₃ is hydrogen or a methyl group, R ₄ is alkylene having 1 to 15 carbon atoms with or without-(C = O) O- in the middle or at the end of the chain,

or

N and m are each independently an integer of 1 to 10, R ₅ is alkylene or phenylene group having 1 to 10 carbon atoms. )
<Equation 1>
Maximum Shrinkage (%) = -2.58 + 3000 * [Number of (meth) acrylic functional groups of the acrylic monomer / molecular weight of the acrylic monomer] The method according to claim 1,
The silane compound is a resin type light guide plate composition, characterized in that contained in 1 to 10 parts by weight based on 100 parts by weight of the total composition for a resin type light guide plate. The method according to claim 1,
The number average molecular weight of the said urethane- (meth) acrylate oligomer is 2,000-5,000, The composition for resin type light-guide plates characterized by the above-mentioned. The method according to claim 1,
The resin-type light guide plate composition, wherein the urethane- (meth) acrylate oligomer is included in an amount of 10 to 70 parts by weight based on 100 parts by weight of the total composition for the resin type light guide plate. The method according to claim 1,
The resin-based light guide plate composition, characterized in that the acrylic monomer is contained in 10 to 60 parts by weight based on 100 parts by weight of the total composition for the resin light guide plate. The method according to claim 1,
The resin light guide plate composition further comprises a hydrogen bond type (meth) acrylate containing a hydroxyl group or a carboxyl group. The method of claim 6,
The hydrogen bond type (meth) acrylate is a resin type light guide plate composition, characterized in that it comprises at least one selected from the group consisting of compounds represented by the formula (4) and (5).
&Lt; Formula 4 >

In Formula 4, R ₁ Is a single bond, alkylene or heteroalkylene having 1 to 10 carbon atoms, cycloalkylene having 3 to 8 carbon atoms, phenylene, alkylphenylene having 1 to 10 carbon atoms, phosphorus, alkoxyphosphonoyl group having 1 to 10 carbon atoms, or Phosphinicosuccinic Nikko group and, R ₂ is H when R ₁ is a single bond, a hydroxy group or a carboxyl group when R ₁ is not a single bond, R ₃ is hydrogen or a methyl group. )
&Lt; Formula 5 >

(Formula 5, R ₁ Is a C1-C10 alkyl group or heteroalkyl group, a C3-C8 cycloalkyl group, a phenyl group, a C1-C10 alkylphenyl group, R <_3> is hydrogen or a methyl group. ) The method of claim 6,
The said hydrogen bond type (meth) acrylate is an acid-modified (meth) acrylate oligomer formed by reaction of the (meth) acrylate monomer containing an acid anhydride and a hydroxyl group, The composition for resin type light-guide plates characterized by the above-mentioned. The method according to claim 8,
The acid-modified (meth) acrylate oligomer is at least one selected from the group consisting of compounds represented by the formulas (6a to 6f) for resin type light guide plate composition.
<Formula 6a>

<Formula 6b>

<Formula 6c>

<Formula 6d>

<Formula 6e>

<Formula 6f>

In Formulas 6a to 6f, R ₁ are each independently hydrogen or a methyl group, and R ₂ is each independently

,

,

,

or

N is an integer of 1 to 10, R ₃ is each independently selected from hydrogen, a saturated or unsaturated alkyl group of 1 to 10 carbon atoms, heteroalkyl group, benzyl group, carboxyl group, hydroxy group or halogen element, R ₄ is a saturated or unsaturated alkylene group having 1 to 10 carbon atoms.) The method of claim 6,
The hydrogen bond type (meth) acrylate is a resin type light guide plate composition, characterized in that it comprises 10 to 60 parts by weight based on 100 parts by weight of the total composition. The method according to claim 1,
The resin-type light guide plate composition comprises two or more kinds of the acrylic monomer, the resin-type light guide plate composition characterized in that the maximum shrinkage is 3 to 7% calculated by the following formula (2):
<Equation 2>
Max Shrinkage (%) =

(In Formula 2, i represents the number of acryl-type monomers contained in the said resin type light-guide plate composition, and each acryl-type monomer is called nth monomer, regardless of the order contained,
XnSn represents the product of Xn and Sn,
Xn represents the mass fraction of the nth monomer,
Sn represents the maximum shrinkage of the n-th monomer and is calculated by Equation 1 above.) The method according to claim 1,
The resin-type light guide plate composition further comprises an ultraviolet stabilizer or a heat stabilizer. Light emitting diodes; And a light guide plate formed on a reflecting plate with the composition of any one of claims 1 to 12 so that the light emitting diode is covered. The method according to claim 13,
And a thickness of the light guide plate is 0.2 to 2 mm. A liquid crystal display device comprising the backlight unit of claim 13.

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