KR20120049650A - Backlight unit - Google Patents

Abstract

PURPOSE: A backlight unit is provided to obtain high brightness and superior brightness uniformity. CONSTITUTION: A first bonding pad(30) includes a first bonding layer(31) on a substrate(10). The first bonding layer includes a scattering particle(32). A second bonding pad(40) is attached to an upper part of the first bonding pad. The second bonding pad includes a second bonding layer(41). The second bonding layer includes scattering particles(42).

Description

Backlight unit

The present invention relates to a backlight unit.

The backlight unit (BLU) is a light source device included in the display device. For example, the liquid crystal screen of a liquid crystal display (LCD) does not emit light, so the light incident on the front side is reflected back to the mirror on the rear side of the liquid crystal, or the light is emitted from the back light unit. To display the screen.

The backlight unit is directly related to the brightness and power consumption of the display device. Accordingly, a light guide plate, a diffuser sheet, a diffuser plate, or the like may be designed to improve performance of the unit, or a cold cathode tube or a light emitting diode (LED) may be used. Researches such as designing the shape and arrangement of the light emitting body, researches for inducing light emission at low power, and the like are being conducted. In addition, attempts have been made to improve luminance by placing optical elements such as diffuser plates or retroreflective plates on top of light sources or light guide plates.

An object of the present invention is to provide a backlight unit.

The present invention, the light emitting body is located on the substrate; A monomer or polymer component attached to the top of the substrate; And a first pressure sensitive adhesive pad having a first pressure sensitive adhesive layer that is a cured product of the first pressure sensitive adhesive composition including scattering particles; And a monomer or a polymer component attached to an upper portion of the first adhesive pad; And a second pressure sensitive adhesive pad having a second pressure sensitive adhesive layer that is a cured product of the second pressure sensitive adhesive composition containing a larger amount of scattering particles than the first pressure sensitive adhesive composition.

Hereinafter, the backlight unit of the present invention will be described in detail.

The backlight unit may be used as a light source device of a display device such as a liquid crystal display, and in one example, the backlight unit may be a direct backlight unit (Direct BLU).

1 is a cross-sectional view schematically showing the backlight unit 1 according to one example. As illustrated in FIG. 1, the backlight unit 1 may include a substrate 10 and a light emitter 20 disposed on the substrate 10. The specific kind of the substrate included in the unit and the light emitting body present thereon is not particularly limited. In one example, the substrate may be a printed circuit board (PCB), and the light emitting body on the substrate may be a light emitting diode (LED). Such light emitting diodes may be arranged in a predetermined pattern on a printed circuit board. In addition, an appropriate reflective layer may be formed between the substrate and the light emitter. The reflective layer may serve to refract the light emitted from the light emitter upwards. The specific kind, design, and the like of the substrate and the light emitting body are not particularly limited. In the art, various structures, designs, materials, and the like of substrates and light emitters that may be used in the backlight unit are known, and all of the above contents may be applied to the backlight unit.

The unit includes first and second adhesive pads sequentially attached to the upper portion of the substrate. In the above description, "adhesion to the top" means that the pad is directly attached to the upper part of the adherend, as well as other elements on the upper part of the adherend, for example, an optical film or a plastic film. It also includes the case where is attached. As illustrated in FIG. 1, the backlight unit 1 may include a first adhesive pad 30 including a first adhesive layer 31 including scattering particles 32 on a substrate 10, and the first adhesive pad 30. The first adhesive pad 30 may include a second adhesive pad 40 attached to an upper portion of the adhesive pad 30 and having a second adhesive layer 41 including scattering particles 42.

It is preferable that the adhesive layer of a said 1st adhesive pad adheres to the upper part of the said board | substrate. In the above-mentioned "pressure sensitive adhesive layer adhered to the upper part of a board | substrate", in the board | substrate with a light emitting body in the upper part, an adhesive layer is attached to the whole surface of the said board | substrate and a light emitting body, and is substantially between the said board | substrate, a light emitting body, and an adhesive layer. This means that there is no air gap. In the unit, it is preferable that the air layer is not substantially present between the first and second adhesive pads. In this manner, if the air layer is substantially excluded, the loss of light emitted from the light emitting body can be prevented and the luminance can be improved.

A pressure sensitive adhesive is a type of adhesive material, and exhibits viscoelastic properties while maintaining a semi-solid state, unlike an adhesive generally changing from liquid to solid after adhesion. By the above characteristics, the adhesive pad can be effectively adhered to the substrate while effectively overcoming the step by the light emitter. In addition, the adhesive pad is effective in the configuration of a flexible element without causing warping, lifting, or peeling even under severe conditions such as high temperature or high temperature and high humidity.

In the above, both the first and second adhesive pads include scattering particles, and the content of the scattering particles included in the first adhesive pad is relatively small compared to the content of the scattering particles included in the second adhesive pad. As described above, the first and second adhesive pads having controlled weight ratios of scattering particles are sequentially formed on the substrate, and the first adhesive pads scatter light from the light emitter and induce light toward the second adhesive pad. It acts as a layer and the second adhesive pad can act as a diffusion layer to diffuse scattered light.

Therefore, in the above unit, it is generally not necessary to separately install a diffuser plate provided in the backlight unit of the direct type, and the air layer existing between the light emitter and the diffuser plate can be eliminated, so that excellent luminance and A surface light source having luminance uniformity can be provided.

In the above, the pressure-sensitive adhesive layer of the first or second pressure-sensitive adhesive pad may be a monomer or a polymer component; And it can be configured by curing the pressure-sensitive adhesive composition containing scattering particles. Curing of the pressure-sensitive adhesive composition in the above means a process in which the pressure-sensitive adhesive composition is converted to the pressure-sensitive adhesive through a process such as drying, heating, aging and / or light irradiation. In addition, the monomer or polymer in the above is a component that forms the base of the pressure-sensitive adhesive through the above curing process. In addition, the term "polymer" means generically the compound of the form in which 2 or more monomers superposed | polymerized here, for example, it is the meaning containing the component normally called an oligomer. In the manufacture of pressure-sensitive adhesives, various monomers or polymer components used to form the pressure-sensitive adhesive composition are known, and these components can be used without limitation in the present invention.

For example, the pressure-sensitive adhesive composition may be composed of a thermosetting or photocuring type according to the monomer or polymer component.

For example, when the pressure-sensitive adhesive composition is a thermosetting type, the monomer or polymer component may be an acrylic polymer having a crosslinkable functional group. The specific kind of polymer that can be used in this case is not particularly limited, and polymers commonly used as adhesive resins such as (meth) acrylic acid alkyl esters and air which can provide crosslinkable functional groups in the side chains or ends of the polymers Acrylic polymers comprising a synthetic monomer in a polymerized form can be used. Specific examples of the (meth) acrylic acid alkyl esters include alkyl groups having 1 to 14 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate or ethylhexyl (meth) acrylate. An alkyl (meth) acrylate etc. which have a branch are mentioned. In addition, the copolymerizable monomer may be a copolymerizable moiety such as an ethylenic double bond in a molecule; And monomers having a crosslinkable functional group such as a hydroxy group, a carboxyl group, an epoxy group, an isocyanate group or an amide group and the like at the same time, and such monomers are well known in the art.

The weight ratio of each monomer included in the acrylic polymer having a crosslinkable functional group as described above is not particularly limited, and may be adjusted in consideration of initial adhesive force, adhesive force and cohesion force of the desired adhesive. In addition, in the acrylic polymer, if necessary, various copolymerizable monomers other than those described above may also be included in a polymerized form. The polymer may be prepared by conventional polymerization methods in the art, such as solution polymerization, photo polymerization, bulk polymerization, suspension polymerization or emulsion polymerization. It can be produced by such a method.

The thermosetting type pressure-sensitive adhesive composition may further include a polyfunctional crosslinking agent capable of crosslinking the polymer together with the acrylic polymer described above. In this case, the kind of specific crosslinking agent is not specifically limited, For example, well-known crosslinking agents, such as an isocyanate type crosslinking agent, an epoxy type crosslinking agent, an aziridine type crosslinking agent, and a metal chelate crosslinking agent, can be used. In addition, the ratio of the crosslinking agent in the composition is not particularly limited, and may be appropriately adjusted in consideration of the desired cohesive force.

The first or second pressure-sensitive adhesive composition may also be composed of a photocurable type. The term "photocuring pressure-sensitive adhesive composition" means a composition which is converted into an adhesive through a curing process induced by light irradiation, that is, irradiation of electromagnetic waves. The electromagnetic wave may be microwave, infrared (IR), ultraviolet (UV), X-ray, γ-ray, α-particle beam, proton beam, neutron beam, and It is used generically to refer to a particle beam such as an electron beam.

When the first or second pressure-sensitive adhesive composition is composed of a photocurable type, the monomer or polymer component may include a photocurable oligomer and a monomer for reactive dilution. Examples of the photocurable oligomer may include all oligomer components used in the manufacture of a photocurable pressure-sensitive adhesive composition such as UV curable. For example, the oligomer may include urethane acrylate obtained by reacting a polyisocyanate having two or more isocyanate groups and a hydroxyalkyl (meth) acrylate in the molecule; Ester acrylates obtained by dehydration condensation of polyester polyols and (meth) acrylic acid; Ester urethane acrylate in which an ester urethane resin reacted with a polyester polyol and a polyisocyanate is reacted with hydroxyalkyl acrylate; Ether acrylates such as polyalkylene glycol di (meth) acrylate and the like; Ether-based urethane acrylates in which an ether-based urethane resin obtained by reacting a polyether polyol and a polyisocyanate with hydroxyalkyl (meth) acrylate is reacted; Or an epoxy acrylate to which an epoxy resin and (meth) acrylic acid are added and reacted, but is not limited thereto.

As the monomer for reactive dilution included with the oligomer, any monomer having a reactive functional group such as a (meth) acryloyl group in the molecular structure can be used without particular limitation. Such monomers may serve to adjust the viscosity of the composition and to implement adhesion after curing. As such a monomer, Alkyl (meth) acrylate; Hydroxy group-containing monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate or hydroxybutyl (meth) acrylate; Carboxyl group-containing monomers such as (meth) acrylic acid or β-carboxyethyl (meth) acrylate; Alkoxy group-containing monomers such as 2- (2-ethoxyethoxy) ethyl (meth) acrylate and the like; Aromatic group-containing monomers such as benzyl (meth) acrylate or phenoxyethyl (meth) acrylate; Heterocyclic moieties containing monomers such as tetrahydrofurfuryl (meth) acrylate or (meth) acryloyl morpholine; Or polyfunctional acrylate, and the like, but is not limited thereto.

Specific types and blending ratios of the oligomer and the reactive diluent monomer are not particularly limited and may be appropriately selected in consideration of the viscosity of the desired composition and the adhesive properties to be implemented after curing.

The first or second pressure-sensitive adhesive composition, as described above, may be composed of a thermosetting or photocuring type, preferably a photocuring type. When the pressure-sensitive adhesive composition is composed of a photocurable type, the monomer or polymer component may be a type including a photocurable oligomer and a diluent monomer, as described above, but may preferably be a photocurable syrup. In the above photocurable syrup, Alkyl (meth) acrylate; And monomer mixtures comprising hydrophilic monomers or partial polymers thereof.

The kind of alkyl (meth) acrylate contained in the monomer mixture is not particularly limited. For example, in consideration of the cohesion force and the glass transition temperature of the pressure-sensitive adhesive, a linear or branched alkyl group having 1 to 14 carbon atoms is included. The branch can use alkyl (meth) acrylate. Examples of such monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl ( Meta) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n- Octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate, and the like. Mixing can be used.

In addition, the hydrophilic monomer contained in a monomer mixture is a monomer which has a polar functional group in a molecule | numerator, and can prevent the whitening phenomenon from occurring in an adhesive.

As a hydrophilic monomer, if it contains a polar functional group in a molecule | numerator, it can use without a restriction | limiting, It is preferable to use the monomer represented by following formula (1), (2) or (3).

[Formula 1]

[Formula 2]

(3)

In Chemical Formulas 1 to 3, R represents hydrogen or an alkyl group, R ₁ represents hydrogen or -A ₃ -C (= 0) -OH, R ₂ represents -A ₄ -OH, and R ₃ represents an alkyl group And A ₁ to A ₄ each independently represent alkylene.

In Formulas 1 to 3, R may preferably be hydrogen or an alkyl group having 1 to 4 carbon atoms, and more preferably hydrogen or a methyl group.

In addition, in R ₁ to R ₃ and A ₁ to A ₄ of Formulas 1 to 3, alkyl may be linear having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. Or branched alkyl, and alkylene may be linear, branched, or cyclic alkylene having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. .

In addition, the alkyl or alkylene in the above formulas (1) to (3) is optionally a general substituent known in the chemical field, for example, halogen atoms, hydroxy groups, carboxyl groups, thiol groups, alkoxy groups, alkyl groups, alkenyl groups or alkoxy It may be substituted by the nil group or the like.

In addition, in the compound of Formula 1, R ₁ may preferably represent hydrogen or — (CH ₂ ) _m —C (═O) —OH (m is an integer of 1 to 4). Specific examples of the compound of Formula 1 include (meth) acrylic acid or β-carboxyethyl (meth) acrylate, but are not limited thereto.

In addition, in the compound of Formula 2, R ₂ may preferably represent-(CH ₂ ) _n -OH (where n is an integer of 1 to 4). Specific examples of the compound of Formula 2 include, but are not limited to, hydroxyethyl (meth) acrylate or hydroxybutyl (meth) acrylate.

In addition, in the compound of Formula 3, R ₃ may be alkyl having 1 to 4 carbon atoms, and A ₁ and A ₂ may be each independently alkylene having 1 to 4 carbon atoms. Specific examples of such compounds include, but are not limited to, 2- (2-ethoxyethoxy) ethyl (meth) acrylate.

The monomer mixture in the photocurable syrup may include 50 parts by weight to 99.9 parts by weight of alkyl (meth) acrylate and 0.1 parts by weight to 50 parts by weight of hydrophilic monomer, preferably 60 parts by weight to alkyl (meth) acrylate. 95 parts by weight and 5 to 40 parts by weight of the hydrophilic monomer. The weight ratio of the hydrophilic monomer in the monomer mixture may be adjusted in consideration of the anti-clouding effect of the pressure-sensitive adhesive, handling properties, process efficiency and storage stability. For example, if the weight ratio of the monomer of the formula (1) is excessively increased, there is a fear that the heat generation occurs in the process, the process efficiency may decrease, and if the weight ratio of the monomer of the formula (2) is too high, the storage stability of the pressure-sensitive adhesive is There exists a possibility that it may fall, and when the weight ratio of the monomer of General formula (3) becomes too high, there exists a possibility that an adhesive may become soft too much and handleability may fall. On the other hand, if the weight ratio of the monomers of the formulas (1) to (3) is too low, there is a risk that the cloudiness of the pressure-sensitive adhesive may not be prevented efficiently, and in view of this point, the weight ratio of the monomers may be adjusted. In this specification, unless otherwise specified, a unit "weight part" means a weight ratio.

In one example, the composition of the photocurable syrup may be further controlled to satisfy the required physical properties of the pressure-sensitive adhesive, to prevent cloudiness, and to ensure durability.

That is, in one example, the syrup is alkyl (meth) acrylate; (Meth) acrylic acid or a monomer of the formula (4); And it may be a monomer mixture or a partial polymer thereof comprising a hydrophilic monomer represented by the following formula (5), (2) or (3).

[Formula 4]

[Chemical Formula 5]

In Formulas 4 and 5, R represents hydrogen or an alkyl group, R ₄ represents a monovalent moiety derived from an aliphatic saturated hydrocarbon cyclic compound, and R ₅ represents -A ₅ -C (= 0) -OH. In the above, A ₅ represents alkylene.

In Formulas 4 and 5, R may preferably be hydrogen or an alkyl group having 1 to 4 carbon atoms, more preferably hydrogen or a methyl group.

In addition, in Formulas 4 and 5, A ₅ may be linear, branched or cyclic alkylene having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. .

In addition, the alkyl or alkylene in the general formula (4) and (5) is optionally a general substituent known in the chemical field, for example, a halogen atom, hydroxy group, carboxyl group, thiol group, alkoxy group, alkyl group, alkenyl group or alkoxy It may be substituted by the nil group or the like.

In addition, in the compound of Formula 4, R ₄ may preferably be a monovalent residue derived from an aliphatic saturated hydrocarbon cyclic compound having 3 to 20 carbon atoms, preferably 6 to 15 carbon atoms. Examples of such a compound of Formula 4 include, but is not limited to, isobornyl (meth) acrylate.

In addition, in the compound of Formula 5, R ₅ may be preferably-(CH ₂ ) _m -C (= 0) -OH (m is an integer of 1 to 4). Specific examples of the compound of Formula 5 include, but are not limited to, β-carboxyethyl (meth) acrylate.

In addition, more specific examples of Chemical Formulas 2 and 3 are as described above.

The monomer mixture of the above examples may include 50 parts by weight to 99.9 parts by weight of alkyl (meth) acrylate; 5 to 40 parts by weight of (meth) acrylic acid or the monomer of Formula 4; 0.1 to 40 parts by weight of the hydrophilic monomer may be included, and preferably 60 to 95 parts by weight of alkyl (meth) acrylate; 10 to 30 parts by weight of (meth) acrylic acid or the monomer of Formula 4; 5 to 30 parts by weight of the hydrophilic monomer may be included. In the composition, (meth) acrylic acid or the monomer of the formula (4) mainly plays a role of securing the durability of the pressure-sensitive adhesive, if the weight ratio is too low, there is a fear that the effect of securing durability. In addition, when the weight ratio of (meth) acrylic acid is excessively high, there is a possibility that heat generation is greatly caused and the process efficiency is lowered. If the weight ratio of the monomer of Formula 4 is too high, the adhesiveness of the pressure-sensitive adhesive may be degraded. Considering the weight ratio can be controlled.

When the said adhesive composition contains the partial polymer of the above-mentioned monomer mixture as said syrup, the polymerization rate of a monomer mixture or conversion rate of a monomer is not specifically limited. For example, the polymerization rate or the conversion rate can be controlled in consideration of process efficiency, desired adhesive properties, and the like.

The first and second pressure-sensitive adhesive compositions each contain scattering particles. The term "scattering particle" means a particle having a refractive index different from that of the pressure-sensitive adhesive, which can impart a property capable of diffusing or scattering incident light. The adhesive in the relationship of the refractive index with the said scattering particle means the hardened | cured material of the adhesive composition except the said scattering particle in the adhesive composition which forms each said adhesive layer. Specifically, the scattering particles included in the first pressure-sensitive adhesive pad, the difference in refractive index with the first pressure-sensitive adhesive may be 0.05 to 1.0, preferably 0.05 to 0.6, more preferably 0.05 to 0.4, and second The scattering particles included in the pressure-sensitive adhesive pad may also have a difference in refractive index from the second pressure-sensitive adhesive of 0.05 to 1.0, preferably 0.05 to 0.6, more preferably 0.05 to 0.4. In addition, the scattering particles may have a relationship as described above, respectively having a high refractive index compared to the first or second pressure-sensitive adhesive. If the difference in refractive index is less than 0.05, the light scattering or light diffusing effect of each pad may be insignificant. If the refractive index difference is more than 0.6, the total light transmittance of each pad may be lowered, making it difficult to apply to optical applications.

Specific kinds of the scattering particles are not particularly limited as long as they have good compatibility and dispersing properties with other components of the composition, and can perform the same role as described above. In addition, the shape of the particles is not limited, but may be any shape such as spherical, polyhedral or amorphous, but may preferably be spherical. In this case, the sphere includes geometrically complete spheres as well as substantially or approximately spheres.

Specific examples of the scattering particles include particles made of an organic material such as acrylic resin, styrene resin, urethane resin, melamine resin, benzoguanamine resin, epoxy resin or silicone resin; Or particles made of an inorganic material such as silica, titanium oxide (TiO ₂ ), magnesium fluoride (MgF ₂ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), or glass. It is not limited to this. In the above, the acrylic resin, the styrene resin, or the urethane resin may form particles in a crosslinked or non-crosslinked state. As the scattering particles, for example, a benzoguanamine-formaldehyde condensate (EPOSTAR M30: refractive index 1.66), a melamine formaldehyde condensate (EPOSTAR, refractive index 1.66), poly (manufactured by NIPPON SHOKUBAI) Methyl methacrylate-based crosslinked product (EPOSTAR MX, refractive index 1.49), crosslinked poly (methyl methacrylate) (MBX, refractive index 1.49) made by Sekisui Chemical Co., Ltd. (SEKISUI CHEM.), Crosslinked polystyrene (SBX, refractive index 1.59), Polyester resin beads (KSR-3, refractive index 1.59) made by Soken Chemical Co., Ltd. (Toss pearl, refractive index 1.43) made by TOSHIBA SILICON, Toray pearl made by TORAY company Refractive index 1.59), polystyrene beads (GS-0459S-6, refractive index 1.59) manufactured by Ganz, or polystyrene beads (HR-59-40, refractive index 1.59) manufactured by advanced chemicals, etc., but are not limited thereto. It is not.

The scattering particles may have an average particle diameter of about 1,000 nm to 30,000 nm, preferably about 1,000 nm to 20,000 nm, more preferably about 1,000 nm to 10,000 nm, even more preferably about 1,000 nm to 6,000 nm. . If the size of the scattering particles is too small, there is a fear that the light scattering or light diffusion effect is lowered. If the size of the scattering particles is too large, the adhesiveness may be reduced.

In the above, the content of the particles in the first and second pressure-sensitive adhesive composition is, as described above, as long as the second pressure-sensitive adhesive layer is controlled to include a larger amount of particles than the first pressure-sensitive adhesive layer, the desired light scattering or light It can be changed in consideration of the diffusibility. For example, the first and second pressure-sensitive adhesive composition is 0.02 to 50 parts by weight, preferably 0.02 to 20 parts by weight, more preferably 0.02 to 100 parts by weight of each monomer or polymer component. It may comprise from 10 parts by weight to 10 parts by weight, more preferably 0.02 parts by weight to 5 parts by weight of scattering particles, respectively. If the weight ratio of the scattering particles is too small, there is a fear that the light scattering or light diffusion effect is lowered, if too high, there is a fear that the adhesiveness is lowered, the weight ratio can be controlled in consideration of this.

The first or second pressure-sensitive adhesive composition may further include a dye. The dye may adjust the color of the pressure-sensitive adhesive and appropriately included to prevent whitening and yellowing from occurring in the pressure-sensitive adhesive. The specific kind of the dye is not particularly limited, and for example, a conventional organic dye used for coloring a plastic material may be used. For example, nitroso dyes, nitro dyes, azo dyes, triphenylmethane dyes, phthalic anhydride dyes, indigo (indigo) -based dyes or anthraquinone-based dyes and the like may be used, and preferably anthraquinone-based dyes may be used as blue dyes. Examples of the dye that can be suitably used in the present invention include, but are not limited to, the Macrox series manufactured by Lanxess.

The addition amount of the dye is not particularly limited, and may be appropriately selected in consideration of, for example, the color tone of the adhesive pad. For example, the dye component may be included in the composition in an amount of 0.001 ppm to 10 ppm, preferably 0.05 ppm to 6 ppm, thereby effectively controlling the color tone of the pressure-sensitive adhesive, while preventing a decrease in luminance and the like. .

The 1st or 2nd adhesive composition can contain a polyfunctional acrylate with the above-mentioned component as needed. The multifunctional acrylate may be preferably included, but is not limited thereto, especially when the monomer or polymer component is the photocurable syrup described above. As a kind of polyfunctional acrylate, 1, 4- butanediol di (meth) acrylate, 1, 6- hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethyleneglycol, for example Di (meth) acrylate, neopentylglycol adipate di (meth) acrylate, hydroxyl puivalic acid neopentylglycol di (meth) acrylate, dicyclopentanyl di ( Meta) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified di (meth) acrylate, di (meth) acryloxy ethyl isocyanurate, allylated cyclohexyl di (Meth) acrylate, tricyclodecane dimethanol (meth) acrylate, dimethylol dicyclopentane di (meth) acrylate, ethylene oxide modified hexahydrophthalic acid di (meth) acrylate, tri Cyclodecane dimethanol (meth) acrylate, neopentylglycol modified trimethylpropane di (meth) acrylate, adamantane di (meth) acrylate or 9,9-bis [4- (2-acryloyl Bifunctional acrylates such as oxyethoxy) phenyl] fluorine and the like; Trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide Trifunctional acrylates such as modified trimethylolpropane tri (meth) acrylate, trifunctional urethane (meth) acrylate or tris (meth) acryloxyethyl isocyanurate; Tetrafunctional acrylates such as diglycerin tetra (meth) acrylate or pentaerythritol tetra (meth) acrylate; 5-functional acrylates, such as propionic acid modified dipentaerythritol penta (meth) acrylate; And dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate or urethane (meth) acrylate (ex. Isocyanate monomers and trimethylolpropane tri (meth) acrylate 6 functional acrylates such as reactants, etc. may be used, but are not limited thereto .. The multifunctional acrylate may be included in the composition at 0.05 to 50 parts by weight, based on 100 parts by weight of the monomer or polymer component, but this is a process It may be changed in consideration of the efficiency, or the physical properties of the adhesive pad.

When the first or second pressure-sensitive adhesive composition is composed of a photocuring type, the composition may further include a photoinitiator, and may control the degree of polymerization according to the amount of the component used. As a photoinitiator, as long as it can start hardening reaction through light irradiation etc., any can be used. For example, alpha-hydroxy ketone type compounds (ex. IRGACURE 184, IRGACURE 500, IRGACURE 2959, DAROCUR 1173; Ciba Specialty Chemicals); Phenylglyoxylate compounds (ex. IRGACURE 754, DAROCUR MBF; Ciba Specialty Chemicals); Benzyl dimethyl ketal compounds (ex. IRGACURE 651; Ciba Specialty Chemicals); a-aminoketone compounds (ex. IRGACURE 369, IRGACURE 907, IRGACURE 1300; Ciba Specialty Chemicals); Monoacylphosphine-based compounds (MAPO) (ex. DAROCUR TPO; Ciba Specialty Chemicals); Bisacylphosphene compounds (BAPO) (ex. IRGACURE 819, IRGACURE 819DW; Ciba Specialty Chemicals); Phosphine oxide compounds (ex. IRGACURE 2100; Ciba Specialty Chemicals); Metallocene compounds (ex. IRGACURE 784; Ciba Specialty Chemicals); Iodonium salts (ex. IRGACURE 250; Ciba Specialty Chemicals); And mixtures of one or more of the above (ex. DAROCUR 4265, IRGACURE 2022, IRGACURE 1300, IRGACURE 2005, IRGACURE 2010, IRGACURE 2020; Ciba Specialty Chemicals, etc.). However, the present invention is not limited thereto.

The photoinitiator may be included in the composition in an amount of 0.05 to 20 parts by weight based on 100 parts by weight of the monomer or polymer component described above, but this may be changed in consideration of process efficiency or physical properties of the cured product.

The first or second pressure-sensitive adhesive composition may further include an antioxidant. Antioxidants may be appropriately blended to prevent yellowing of the pressure-sensitive adhesive. The specific kind of the antioxidant is not particularly limited, and conventional ingredients known in this field (ex. Songwon Industries, Songnox series, Songnox 1076, Songnox 1035, Songnox 1135, Songnox 1010, etc .; Ciba Corporation) Irganox PS-800, 1010) can be used, and its content can also be appropriately adjusted in consideration of the intended physical properties.

The first or second pressure sensitive adhesive composition may also further comprise a re-workability improver. By further including a reworkability improving agent, it is possible to improve workability and re-peelability, etc. in the process of applying the adhesive pad. The specific kind of reworkability improving agent that can be used is not particularly limited, and various materials known in the art, for example, a fluorine-based compound, a silicone compound or a low molecular weight, can be appropriately used. In addition, the content of the reworkability improving agent is also not particularly limited, and may be appropriately selected in consideration of the desired physical properties and the composition of the composition.

If necessary, the first or second pressure-sensitive adhesive composition may contain one or more kinds of thermosetting agents, catalysts, UV curing agents, silane coupling agents, scattering bodies, ultraviolet stabilizers, colorants, reinforcing agents, fillers, antifoaming agents, surfactants, and plasticizers. The same additive may further be included.

The first or second pressure-sensitive adhesive composition as described above may have a viscosity at 25 ° C. of about 500 cps to 10,000 cps, preferably about 1,000 cps to 8,000 cps, and more preferably about 1,000 cps to 7,000 cps. In one example, the first pressure sensitive adhesive composition has a viscosity ranging from about 4,500 cps to 10,000 cps, preferably about 4,500 cps to 7,000 cps, and the second pressure sensitive adhesive composition has a viscosity of about 500 cps to 4,000 cps, preferably Preferably from about 1,000 cps to 4,000 cps. In the present invention, by controlling the viscosity of the composition in the above-mentioned range, respectively, it is possible to efficiently form the interface between the first and second adhesive pads while ensuring excellent process efficiency and adhesion characteristics of the adhesive pads. The method of controlling the viscosity of the pressure-sensitive adhesive composition as described above is not particularly limited. For example, if the composition is a thermosetting type described above, a method of controlling the solid content of the polymer, the molecular weight or the dilution ratio with the solvent can be used, and in the case of containing a photocurable oligomer and a monomer for reactive dilution, the oligomer and / Or the kind of monomer and the method of controlling a compounding ratio can be used, and when using a monomer mixture or its partial polymerization product, the method of adjusting the weight ratio or polymerization rate between monomers can be used.

The thicknesses of the first and second adhesive pads may be appropriately selected in consideration of the desired effects. In one example, the first adhesive pad may have a thickness of about 1.6 mm to 2 mm, and the second adhesive pad may have a thickness of about 0.1 mm to 1 mm. By controlling the thicknesses of the first and second adhesive pads in the above ranges, the respective adhesive pads can be effectively exerted in the desired physical properties.

As exemplarily shown in FIGS. 2 and 3, the units 2 and 3 may also be arranged between the first and second adhesive pads 30 and 40 or as shown in FIG. 2. 40 may further include a transparent plastic film 50 on which the light shielding pattern 60 is printed. As described above, the sheet having the light shielding pattern can be used to prevent unevenness of the display device due to light emitted from the light emitting body. 2 and 3 illustrate the case where the light shielding pattern is printed on the upper portion of the film, the light shielding pattern may be printed on the lower portion of the film, and may be simultaneously printed on the upper and lower portions as necessary. .

The specific kind of the transparent plastic film is not particularly limited. For example, a polyester resin film, an acrylic resin film, a polycarbonate resin film, a polysulfone resin film, a polyimide resin film, an olefin resin film, etc. can be used as said plastic film. In addition, the method of forming the light shielding pattern on the film is not particularly limited, and may be formed by, for example, a printing process using a known light shielding ink.

The invention also relates to monomer or polymer components; And using the first pressure sensitive adhesive composition including scattering particles, forming a first pressure sensitive adhesive layer on an upper portion of a substrate including a light emitter thereon; And monomer components or polymer components; And forming a second adhesive coating layer on the first adhesive coating layer by using a second adhesive composition including a larger amount of scattering particles than the first adhesive composition. .

As used herein, the term "adhesive coating layer" is a layer formed by the pressure-sensitive adhesive composition, wherein the composition is formed by directly coating the target site, or the composition is first coated on another release moldable sacrificial substrate, and then uncured, dried, and radiused. It is used to encompass a layer formed by being transferred to a target site in a hardened or hardened state. In addition, the adhesive coating layer includes all of the uncured, dried, semi-cured or hardened layers. Thus, for example, once a layer is formed, the formed layer can be dried, cured or semi-cured before the next process is performed.

The method of forming the first adhesive coating layer on the upper portion of the substrate is not particularly limited. For example, the first pressure-sensitive adhesive composition may be directly coated on top of the substrate to form a coating layer, or the composition may be first coated on a suitable release mold sacrificial substrate to form a layer, and then transferred to the substrate. . In view of increasing the adhesion efficiency and the degree of freedom of processing of the first adhesive coating layer to the substrate, a direct coating method is preferred, but is not limited thereto.

In addition, the method of forming the second adhesive coating layer on the first adhesive coating layer is also not particularly limited, and for example, a direct coating or a transfer method using the second adhesive composition may be applied as described above.

In one example, the method includes coating the first pressure-sensitive adhesive composition on top of the substrate to form a first pressure-sensitive adhesive layer, and then coating the second pressure-sensitive adhesive composition on top of the first pressure-sensitive adhesive layer to form a second pressure-sensitive adhesive layer. It may comprise the step of forming. For example, by adjusting the viscosity of each pressure-sensitive adhesive composition in the above range in this process, it is possible to effectively form an interface between the pressure-sensitive adhesive coating layer.

In another example, the method also forms a second pressure-sensitive adhesive layer by coating the second pressure-sensitive adhesive composition on a plastic sheet having a light shielding pattern after forming the first pressure-sensitive adhesive layer by the above-described direct coating or transfer method. step; And laminating the plastic sheet on which the second adhesive coating layer is formed on the first adhesive coating layer to form a second adhesive coating layer.

In another example, the method, after forming the first adhesive coating layer, laminates a plastic sheet having a light shielding pattern printed on top of the first adhesive coating layer, and forms a second adhesive coating layer on the laminated plastic sheet. It may also comprise the step.

In each of the above examples, the order and manner of curing the first and second adhesive coating layers to form the first and second adhesive pads are not particularly limited.

For example, a method of forming the first adhesive coating layer, curing the coating layer first, and then again forming a second adhesive coating layer, and curing the coating layer; A method of forming the second adhesive coating layer while the first adhesive coating layer is dried, uncured or semi-cured, and curing the first and second adhesive coating layers simultaneously or sequentially may be applied, which may be considered in consideration of process efficiency. Can be adjusted.

The method for curing or semi-curing the pressure-sensitive adhesive coating layer is not particularly limited, and in consideration of the composition of the composition used, an appropriate photocuring method or thermosetting method may be employed. For example, when the pressure-sensitive adhesive composition is a thermosetting type composition, the coated composition may be cured or semi-cured by applying to an appropriate drying, heating or aging process, and in the case of the photocuring type, a photoinitiator or the like contained in the composition. It can be cured or semi-cured by irradiating electromagnetic waves, such as UV, which can affect and cause a polymerization or curing reaction. The conditions such as the temperature or time at the time of drying, heating or aging, the amount of light or illuminance at the time of irradiation of electromagnetic waves are not particularly limited, and may be appropriately selected in consideration of the composition of the composition and the desired degree of curing.

The method of manufacturing the backlight unit is not limited to the above-described method. For example, the pressure-sensitive adhesive composition may be directly coated on a substrate and cured to prepare a unit.

The present invention also relates to a display device including the backlight unit as a light source.

The display device may be, for example, a liquid crystal display device. In this case, the device may further include a liquid crystal panel installed on the backlight unit. In addition, the display device may further include an optical film such as a brightness enhancement film (BEF) or a dual brightness enhancement film (DBEF).

Various elements constituting the display device, arrangement or design thereof, etc. are not particularly limited, and all the usual methods and elements constituting the device may be employed according to the type of the device.

In the present invention, by using an adhesive pad that can be effectively adhered to a substrate or the like, effectively overcome the step of the light emitter, and the scattering particles are mixed with an adhesive excellent in physical properties such as durability and stress relaxation under high temperature or high temperature and high humidity conditions. A light scattering layer and a light diffusing layer are respectively formed. Accordingly, it is possible to provide a light source device having high brightness and excellent brightness uniformity, which can be formed in a thin thickness, and which is also advantageous for application to a flexible element.

1 to 3 are cross-sectional views showing various examples of the backlight unit.

Hereinafter, the present invention will be described in more detail through examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the examples given below.

Example 1.

A monomer mixture was prepared by combining 70 parts by weight of ethylhexyl acrylate, 30 parts by weight of isobornyl acrylate and 10 parts by weight of acrylic acid. Thereafter, an appropriate amount of di (2-ethylhexyl) peroxydicarbonate (EHPDC, di (2-ethylhexyl) peroxydicarbonate) was added to the monomer mixture as a initiator, and the viscosity (25 ° C) was about 5,000 cps after polymerization in a bulk polymerization manner. Partially polymerized to about 6,000 cps to prepare a first photocurable syrup. Then, based on 100 parts by weight of the syrup, 0.5 parts by weight of photoinitiator (2,4,6-trimethylbenzoyl diphenyl phosphoine (TPO)), 0.05 parts by weight of 1,6-hexanediol diacrylate (HDDA) and scattering particles (refractive index: 1.59 , Average diameter: 4,000 nm, polystyrene beads, HR-59-40, 0.02 parts by weight of advanced chemical (manufactured) was added to prepare a first pressure-sensitive adhesive composition. Apart from the above, bulk polymerization is carried out in the same manner as in the case of the first pressure-sensitive adhesive composition with respect to the monomer mixture having the same composition as the first pressure-sensitive adhesive composition, but after polymerization, the viscosity (25 ° C.) is about 2,000 cps to about 3,000 cps. Partially polymerized to obtain a second photocurable syrup. Then, based on 100 parts by weight of the second syrup, 0.5 parts by weight of photoinitiator (TPO), 0.5 parts by weight of 1,6-hexanediol diacrylate (HDDA) and scattering particles (refractive index: 1.59, average diameter: 4,000 nm, Polystyrene beads, HR-59-40, advanced chemical (manufactured) 4 parts by weight was added to prepare a second pressure-sensitive adhesive composition. Subsequently, after curing the first pressure-sensitive adhesive composition on a PCB (47-inch BLU PCB, about 500 ㎛ thickness) on which the LED is arranged on top of the coating so that the thickness is about 1.4 mm, and after curing the second pressure-sensitive adhesive composition is thick Coating was made to about 0.5 mm. Thereafter, using a black light source, the backlight unit having a total thickness of about 2.5 mm or less was cured by irradiating ultraviolet light for about 6 minutes while maintaining the distance between the light source and the coating layer at 15 cm. Prepared.

Example 2.

The content of 1,6-hexanediol diacrylate is changed to 0.3 parts by weight when preparing the first pressure-sensitive adhesive composition, and the content of 1,6-hexanediol diacrylate is changed to 1 part by weight when preparing the second pressure-sensitive adhesive composition. Except one, the backlight unit was manufactured in the same manner as in Example 1.

Example 3.

The content of 1,6-hexanediol diacrylate is changed to 0.3 parts by weight when preparing the first pressure-sensitive adhesive composition, and the content of 1,6-hexanediol diacrylate is changed to 1 part by weight when preparing the second pressure-sensitive adhesive composition. Except for one, the first and second pressure-sensitive adhesive compositions were prepared in the same manner. Thereafter, the prepared first pressure-sensitive adhesive composition is directly coated on a PCB (47-inch BLU PCB, about 500 μm in thickness) on which LEDs are arranged to have a thickness of about 1.4 mm after curing, and on the coated first pressure-sensitive adhesive composition After applying a polyethylene terephthalate sheet printed with a blocking pattern according to the arrangement of the LED, and irradiated with an appropriate amount of ultraviolet light with a black light source in a manner similar to that of Example 1 was semi-cured. Thereafter, the second pressure-sensitive adhesive composition is coated directly onto the sheet on which the light-shielding pattern is printed so that the thickness is about 0.5 mm after curing, and by irradiating an appropriate amount of ultraviolet light with a black light source in the manner described above, the total thickness is achieved. A backlight unit having a length of about 2.5 mm was manufactured.

Example 4.

A thermosetting acrylic oligomer containing a hydroxyl group (manufactured by Soken, product name: UT-3001, viscosity (25 ° C): about 3,500 cps to 4,500 cps) isocyanate curing agent (manufacturer: Nippon Polyurethane Industry Co, product name: Coronate L- 55E) and 0.02 parts by weight of scattering particles (refractive index: 1.59, average diameter: 4,000 nm, polystyrene beads, HR-59-40, advanced chemical) in an acrylic thermosetting pressure-sensitive adhesive composition suitably blended with 100 parts by weight of the total resin component (Agent) was blended to prepare a first pressure-sensitive adhesive composition. Thereafter, 4 parts by weight of scattering particles (refractive index: 1.59, average diameter: 4,000 nm, polystyrene-based beads, HR-59) in the acrylic thermosetting composition having the same composition as used in the first pressure-sensitive adhesive composition, based on 100 parts by weight of the total resin component. -40, advanced chemicals (manufactured)) was combined to prepare a second pressure-sensitive adhesive composition. Subsequently, the first pressure-sensitive adhesive composition is directly coated on the PCB having the LEDs arranged thereon to have a thickness of about 1.5 mm after curing, and the second pressure-sensitive adhesive composition is directly coated to have a thickness of about 0.4 mm after curing. The backlight unit was prepared by curing in an oven at 80 ° C. for 20 minutes.

Example 5

60 parts by weight of ethylhexyl acrylate, 10 parts by weight of acrylic acid, 10 parts by weight of hydroxyethyl acrylate, 10 parts by weight of 2- (2-ethoxyethoxy) ethyl acrylate and isobornyl acryl in preparing the photocurable syrup Using a monomer mixture prepared by blending 10 parts by weight rate, 1 ppm of a dye (Blue dye, MACROLEX Blue RR Gran manufactured by Lanxess) was further added in the process of preparing the first and second pressure-sensitive adhesive compositions using the syrup. Except for that, a backlight unit was manufactured in the same manner as in Example 1.

Test Example 1. Durability Test

Heat resistance and moisture resistance were evaluated for the light sources (horizontal and vertical lengths of 10 cm and 30 cm, respectively) (samples) prepared in Examples. Heat resistance was evaluated by visually observing whether the sample was left at 80 ° C. for 240 hours, and then whether bubbles were generated, lifting and peeling occurred. Moisture and heat resistance were measured at 60 ° C. and 90% relative humidity. After standing for 240 hours, the same was observed by visually observing whether bubbles, lifting and peeling occurred. Each evaluation criterion is as follows.

<Bubble outbreak evaluation>

(Circle): When the visual observation does not generate | occur | produce bubble in the inside or interface of an adhesive, or when bubble is very small and cannot be observed visually.

X: When visual observation observes the single bubble or the bubble of a large quantity clustered in an adhesive or interface.

<Floating and Peeling Evaluation>

(Circle): When there is no rise and peeling at the interface between an adhesive and a to-be-adhered body

X: When lifting, partial peeling, or complete peeling occurred at the interface between the adhesive and the adherend

Test Example 2 Curling Characteristics Evaluation

The same sample as in Test Example 1 was left to stand in heat-resistant conditions, and the presence or absence of curvature was evaluated. Specifically, the sample was placed in a vertical direction and left at 80 ° C. for 240 hours in a high state, then taken out and slowly cooled at room temperature for about 30 minutes. Thereafter, the samples in the longitudinal direction were placed in contact with each other in a state of facing the flat glass substrate, and the distance farthest from the reference glass substrate to the sample was measured with a tape measure to evaluate whether warpage occurred. .

The measurement results are summarized in Table 1 below.

Example One 2 3 4 5
durability
evaluation
Bubble generation suppression (heat-resistant condition) ○ ○ ○ ○ ○ Bubble generation inhibition (moisture heat condition) ○ ○ ○ ○ ○ Lifting / Peeling (Heat Resistant Condition) ○ ○ ○ ○ ○ Lifting / peeling off (heat-and-moisture condition) ○ ○ ○ ○ ○ Warpage Evaluation (cm) 0 0 0 0 0

From the results of Table 1, in the case of the embodiment of the present invention, it can be seen that both excellent durability and warpage characteristics and the like.

1, 2, 3: backlight unit
10: printed circuit board 20: light emitting diode
30: first adhesive pad 40: second adhesive pad
31, 41: base portion (cured product of adhesive composition)
32, 42: scattering particles
50: transparent resin film 60: shading pattern
70: reflective layer

Claims (24)

A substrate having a light emitting body on top; A monomer or polymer component attached to the top of the substrate; And a first pressure sensitive adhesive pad having a first pressure sensitive adhesive layer that is a cured product of the first pressure sensitive adhesive composition including scattering particles; And a monomer or a polymer component attached to an upper portion of the first adhesive pad; And a second pressure sensitive adhesive pad having a second pressure sensitive adhesive layer that is a cured product of the second pressure sensitive adhesive composition containing a larger amount of scattering particles than the first pressure sensitive adhesive composition. The backlight unit of claim 1, wherein the first pressure sensitive adhesive layer is faced to an upper portion of the substrate. The method of manufacturing a backlight unit according to claim 1, wherein the light emitter is a light emitting diode. The backlight unit according to claim 1, wherein the monomer or polymer component of the first or second pressure sensitive adhesive composition comprises an acrylic polymer having a crosslinkable functional group. The backlight unit of claim 4, wherein the first or second pressure sensitive adhesive composition further comprises a multifunctional crosslinking agent. The backlight unit of claim 1, wherein the monomer or polymer component of the first or second pressure sensitive adhesive composition comprises a photocurable oligomer and a monomer for reactive dilution. The method of claim 1, wherein the monomer or polymer component of the first or second pressure-sensitive adhesive composition is alkyl (meth) acrylate; And a monomer mixture comprising a hydrophilic monomer represented by the formula of any one of Formulas 1 to 3 or a backlight unit thereof:
[Formula 1]

(2)

(3)

In Chemical Formulas 1 to 3, R represents hydrogen or an alkyl group, R ₁ represents hydrogen or -A ₃ -C (= 0) -OH, R ₂ represents -A ₄ -OH, and R ₃ represents an alkyl group And A ₁ to A ₄ each independently represent alkylene. The method of claim 1, wherein the monomer or polymer component of the first or second pressure-sensitive adhesive composition is alkyl (meth) acrylate; (Meth) acrylic acid or a monomer of the formula (4); And a backlight unit which is a monomer mixture or a partial polymer thereof, including a hydrophilic monomer represented by Formula 2, Formula 3, or Formula 5 below:
(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

In Formulas 2 to 5, R represents hydrogen or an alkyl group, R ₂ represents -A ₄ -OH, R ₃ represents an alkyl group, R ₄ represents a monovalent residue derived from an aliphatic saturated hydrocarbon cyclic compound R ₅ represents -A ₅ -C (= 0) -OH, wherein A ₁ , A ₂ , A ₄ and A ₅ each independently represent alkylene. The backlight unit of claim 1, wherein the scattering particles have a difference in refractive index from the pressure-sensitive adhesive of 0.05 to 1.0. The scattering particles are acrylic resin particles, styrene resin particles, urethane resin particles, melamine resin particles, benzoguanamine resin particles, epoxy resin particles, silicone resin particles, silica particles, titanium oxide particles, magnesium fluoride particles. And zirconium oxide particles, aluminum oxide particles or glass particles. The backlight unit of claim 1, wherein the scattering particles have an average particle diameter of 1,000 nm to 30,000 nm. The backlight unit of claim 1, wherein each of the first and second pressure-sensitive adhesive compositions comprises 0.01 to 50 parts by weight of scattering particles based on 100 parts by weight of the monomer or polymer component. The backlight unit of claim 1, wherein the first or second pressure sensitive adhesive composition further comprises a dye. The backlight unit of claim 1, wherein the first or second pressure sensitive adhesive composition further comprises a polyfunctional acrylate. The backlight unit of claim 1, wherein the first or second pressure sensitive adhesive composition further comprises a photoinitiator. The backlight unit of claim 1, wherein the first or second pressure sensitive adhesive composition further comprises an antioxidant. The backlight unit of claim 1, wherein the first or second pressure sensitive adhesive composition further comprises a reworkability improving agent. The backlight unit of claim 1, further comprising a plastic sheet printed with a light shielding pattern present between the first adhesive pad and the second adhesive pad or on an upper portion of the second adhesive pad. Monomer or polymer components; And using the first pressure sensitive adhesive composition including scattering particles, forming a first pressure sensitive adhesive layer on an upper portion of a substrate including a light emitter thereon; Monomer component or polymer component; And forming a second adhesive coating layer on the first adhesive coating layer by using a second adhesive composition including a larger amount of scattering particles than the first adhesive composition. The backlight unit of claim 19, wherein the first adhesive composition is coated on the substrate to form a first adhesive coating layer, and the second adhesive composition is coated on the first adhesive coating layer to form a second adhesive coating layer. Method of preparation. The method of claim 20, wherein the first pressure sensitive adhesive composition has a viscosity at 25 ° C. of 4,500 cps to 10,000 cps, and the second pressure sensitive adhesive composition has a viscosity at 25 ° C. of 500 cps to 4,000 cps. The method of claim 19, wherein the second pressure-sensitive adhesive layer comprises: coating the second pressure-sensitive adhesive composition on a plastic sheet having a light shielding pattern to form a second pressure-sensitive adhesive layer; And laminating a plastic sheet on which the second adhesive coating layer is formed on the first adhesive coating layer. 20. The method of claim 19, further comprising laminating a plastic sheet having a light shielding pattern printed on the first adhesive coating layer after forming the first adhesive coating layer, and forming a second adhesive coating layer on the laminated plastic sheet. The manufacturing method of the backlight unit. A display device comprising the backlight unit of claim 1 as a light source.

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