KR101056694B1 - Thermally Conductive Adhesive Composition - Google Patents

Abstract

The present invention is a) partially polymerized acrylic adhesive resin having a solid content of 20% or less; b) thermally conductive ceramic minerals; And c) a thermally conductive adhesive composition comprising a metal hydroxide, a thermally conductive adhesive sheet having the thermally conductive adhesive sheeted on one or both sides of the substrate, a backlight unit and a liquid crystal display device comprising the same, and the thermoelectric of the present invention. The conductive adhesive not only has excellent workability and formability, but also has high thermal conductivity and flame retardancy of 2.5 W / mK or more.

Acrylic adhesive resin, thermally conductive adhesive, thermally conductive, flame retardant, thermally conductive ceramic inorganic material, metal hydroxide, particle size

Description

Thermally conductive adhesive composition {THERMALLY CONDUCTIVE PRESSURE-SENSITIVE ADHESIVES}

1 is a cross-sectional view illustrating a liquid crystal display device using a backlight unit according to an exemplary embodiment of the present invention.

2 is a cross-sectional view illustrating a direct type backlight unit according to an exemplary embodiment of the present invention.

3 is a cross-sectional view illustrating a side light type backlight unit according to an exemplary embodiment of the present invention.

The present invention relates to a thermally conductive adhesive composition excellent in thermal conductivity and flame retardancy, a thermally conductive adhesive sheet in which the thermally conductive adhesive is sheeted on one or both sides of a substrate, a backlight unit and a liquid crystal display device including the same.

Recently, research is being conducted on a product applying an organic light emitting diode having excellent color reproducibility and excellent contrast to contrast ratio as a backlight of a liquid crystal display panel. However, when the organic light emitting diode is used, the amount of heat generated is much higher than that of the liquid crystal display panel in which the cold cathode fluorescent lamp used as a backlight is used. Therefore, a structure that radiates the generated heat to the outside through the back plate heat sink at the rear is adopted. Should be. Previously, the structure of dissipating heat by using a heat pipe has been examined, but it is known to use a thermally conductive adhesive in which thermally conductive ceramic inorganic particles are dispersed in a polymer as a method for reducing the thickness of the product. The thermal conductivity of the thermally conductive adhesive sheet applied to the liquid crystal display panel using the organic light emitting diode as a backlight is required to be 2.5 W / mK or more. In practice, if the thermal conductivity is less than the above value, the heat transfer efficiency may be very low, causing the organic light emitting diode to burn out. In order to manufacture such a high thermal conductive adhesive sheet, an excessive amount of thermal conductive filler should be added, and in this case, due to the problem of viscosity increase, the processability problem during coating is a serious situation.

Among the thermally conductive adhesives, the polymer provides adhesiveness between the adherends, and the thermally conductive ceramic inorganic particles transmit and release heat generated from the electronic and electronic component elements to the metal PCB on the rear surface. As the polymer, a polymer using a (meth) acrylic ester monomer or the like is used, and thermally conductive ceramic inorganic particles have thermal conductivity and are electrically insulated aluminum oxide, magnesium oxide, calcium oxide, calcium carbonate, boron nitride, and nitride. Fillers, such as aluminum or silicon carbide, are used a lot.

On the other hand, in order to prevent the risk of fire that may occur due to the high heat generated in the electrical and electronic components, recently developed thermally conductive adhesives often have flame retardancy in addition to adhesiveness and thermal conductivity. As a flame retardant for adding flame retardancy to a thermally conductive adhesive as described above, halogen-based flame retardants are avoided due to environmental problems. Therefore, it is required to use a flame retardant containing no halogen element.

Japanese Patent Laid-Open No. 11-269438 discloses a thermally conductive adhesive comprising a metal oxide, a metal nitride, a metal hydroxide as a thermal conductive filler, and a non-halogen organic flame retardant containing both phosphorus and nitrogen as a flame retardant. However, when a thermally conductive flame-retardant adhesive sheet having a thermal conductivity of 2.5 / mK or more using a polymer derived from an acrylic polymer adhesive resin having an ether bond in a molecule, a thermally conductive inorganic filler having high ether bonds in a polymer structure And increase the viscosity of the slurry mixture, so workability and moldability are very deteriorated, making it difficult to produce a product in a sheet state.

Japanese Patent Application Laid-Open No. 2002-294192 discloses a flame retardant in which 100 parts by mass of an acrylic polymer containing a meta acrylic acid ester monomer is used as a flame retardant, 40 to 80 parts by weight of aluminum hydroxide having a particle size of 1 to 50 mm, and a thermally conductive filler having a particle diameter of 50 to 120 mm. Disclosed is a thermally conductive adhesive sheet prepared by adding 40 to 120 parts by weight of aluminum. Although the adhesive sheet implements a thermally conductive adhesive sheet having flame retardancy according to UL94V, the thermal conductivity measured in the embodiment is about 0.7 W / mK, which requires a high heat dissipation effect such as the light emitting diode backlight of the liquid crystal display panel mentioned above. The application is not suitable for electronic component parts.

In Japanese Patent Laid-Open No. 2004-27039, a thermally conductive adhesive prepared by photopolymerization using particles and metal hydride compounds such as metal hydroxides, hydrated metal compounds and metal nitrides using only acrylic acid ester monomers having 1 to 14 carbon atoms, not acrylic polymers. Is described. However, when only the acrylic monomer, not the polymer, is used, since the hardness of the pressure-sensitive adhesive sheet prepared after photopolymerization is very high and the drawing property is very low, workability of the substrate is very poor. In addition, the viscosity of the slurry mixture during processing may cause the filler to sink during blending, thereby making it difficult to uniformly prepare the pressure-sensitive adhesive. In addition, when the use of less than 50-400 parts by mass of the thermally conductive filler described in this invention and 100 parts by weight of a hydrated metal compound that is a flame retardant, it is impossible to produce a thermally conductive adhesive sheet of 2.5 W / mK or more. If the thermally conductive filler is used at 400 parts by mass or less, no matter how much the metal compound is used, it is difficult to realize high thermal conductivity because its thermal conductivity is low. As a result, it is judged that the composition described in the present invention is difficult to be used for the adhesive use of electronic components requiring a high heat conductivity due to the generation of much heat.

Due to the problems of the prior art as described above, research and development of a thermally conductive adhesive having a high thermal conductivity of 2.5 W / mK or more, excellent flame retardancy, and easy processability, and making it possible to produce a uniform product with a desired thickness, is continued. It is required.

The present inventors use acrylic adhesive resin, thermally conductive ceramic inorganic material and metal hydroxide when preparing the thermally conductive adhesive, and when adjusting the content of solid content and / or the weight average molecular weight of the partially polymerized resin, the ceramic inorganic material is solved with excellent processability. It can be thickened to produce a pressure-sensitive adhesive sheet having a thermal conductivity of 2.5W / mK or more, and at the same time, by using a thermally conductive ceramic inorganic material having a particle size of 2 or more, it can provide a higher thermal conductivity by effectively filling the voids between the particles. It has been found that the present invention has been completed.

Accordingly, an object of the present invention is a) partially polymerized acrylic adhesive resin having a solid content of 20% or less; b) thermally conductive ceramic minerals; And c) to provide a thermally conductive adhesive composition comprising a metal hydroxide.

Another object of the present invention is to provide a thermally conductive adhesive sheet in which the thermally conductive adhesive according to the present invention is sheeted on one or both surfaces of the substrate.

Another object of the present invention is a thermally conductive adhesive sheet according to the present invention; And a backlight unit including a light source.

Still another object of the present invention is a backlight unit according to the present invention; And a liquid crystal panel which displays an image using light.

The present invention

a) partially polymerized acrylic adhesive resin having a solid content of 20% or less;

b) thermally conductive ceramic minerals; And

c) metal hydroxides

It relates to a thermally conductive adhesive composition comprising a.

As described above, the prior art has been able to provide a thermally conductive adhesive having thermal conductivity and flame retardancy by using a thermally conductive ceramic inorganic material and a metal hydroxide to an acrylic monomer or an acrylic polymer resin. However, when the thermally conductive ceramic inorganic material and a metal hydroxide are added, a slurry As the viscosity of the mixture in the state rises sharply, workability and formability are drastically decreased, and there is no example of high thermal conductivity of 2.5W / mK or higher.

However, the present invention has a solid content of 20% or less, a weight average molecular weight of 10,000 ~ 1,000,000 adhesive resin; Two or more kinds of thermally conductive ceramic inorganic materials having different or different particle diameters; And by using the metal hydroxide to provide an appropriate viscosity of the slurry mixture to improve the workability and formability, thereby providing a high thermal conductivity can be easily prepared sheet even when the inorganic material is high-filled, It is possible to provide a thermally conductive adhesive having excellent thermal conductivity and flame retardancy without any other flame retardant.

Hereinafter, the composition according to the present invention will be described in detail.

The thermally conductive adhesive composition according to the present invention is characterized by using a partially polymerized acrylic adhesive resin having a solid content of 20% or less, preferably 1 to 20%, more preferably 1 to 18%. Partially polymerized resin refers to a mixed state of a polymer and a monomer, and processability of the pressure sensitive adhesive sheet depends on a content of a polymer that occupies most of a nonvolatile content (solid content) in the partially polymerized resin. That is, when the solid content exceeds the above range, the viscosity of the slurry mixture becomes very high, making it impossible to prepare a uniform adhesive sheet.

In addition, since the viscosity of the slurry mixture depends on the weight average molecular weight of the resin, it is preferable to control the weight average molecular weight of the resin in addition to the solid content in the high filling compounding process for high thermal conductivity. It is preferable that the molecular weight of the adhesive resin which concerns on this invention is 10,000-1,000,000, More preferably, it is 50,000-750,000. If the molecular weight is higher than the above, even if the solid content is low, the viscosity becomes high, and the processability is poor when mixed with the inorganic filler, and if it is lower than the molecular weight, the viscosity is too low when mixed with the inorganic filler to settle the inorganic filler. As a result, a sheet having different double-sided adhesive properties is produced, and thus long-term reliability cannot be guaranteed.

On the other hand, the partially polymerized acrylic adhesive resin usable in the present invention is not particularly limited, but is a polar monomer capable of copolymerization with the monomer in 100 parts by weight of the (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms and an optional component. It is preferable to include 0-20 weight part.

The (meth) acrylic acid ester monomers include ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethyl One or more selected from the group consisting of hexyl (meth) acrylate and isononyl (meth) acrylate may be used, but is not limited thereto.

In addition, the polar monomer copolymerizable with the (meth) acrylic acid ester monomer serves to impart cohesion to the pressure-sensitive adhesive and to improve adhesion. The polar monomer may be used alone or in combination with a monomer containing a carboxyl group such as (meth) acrylic acid, maleic acid, fumaric acid, or a monomer containing nitrogen such as acrylamide, N-vinyl pyrrolidone, and N-vinyl caprolactam. However, the present invention is not limited thereto. Although the ratio of the said polar monomer is not restrict | limited in particular, When the quantity of the said monomer is too large, since adhesiveness and peeling force fall, it can be used for 0-20 weight part with respect to 100 weight part of (meth) acrylic acid ester monomers.

The thermally conductive ceramic inorganic material according to the present invention may use one or more selected from the group consisting of aluminum oxide, magnesium oxide, calcium oxide, calcium carbonate, boron nitride, aluminum nitride, and silicon carbide, but is not limited thereto. The amount of the thermally conductive ceramic inorganic material is preferably 500-1,500 parts by weight based on 100 parts by weight of the partially polymerized acrylic adhesive resin. If the content is less than 500, it is difficult to obtain a desired thermal conductivity, and if it exceeds 1,500, workability may be degraded.

As the metal hydroxide used in the present invention, one or more selected from the group consisting of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide may be used as a flame-retardant that does not include halogen, but is not limited thereto. The amount of the metal hydroxide is preferably 200-1,500 parts by weight based on 100 parts by weight of the partially polymerized acrylic adhesive resin. If the content is less than 200 it is difficult to obtain the desired flame retardancy, if the content exceeds 1,500 may be poor workability. Most preferably, the composition according to the present invention uses aluminum oxide as the thermally conductive ceramic inorganic material and aluminum hydroxide as the metal hydroxide.

In the present invention, the particle diameter of the thermally conductive ceramic inorganic material is preferably 1-100 μm, and the particle size of the metal hydroxide is preferably 0.1-50 μm. In addition, when the metal hydroxide used as a flame retardant is located in the gap between the thermally conductive ceramic inorganic materials, the thermal conductivity may be further improved, so that the particle diameter of the thermally conductive ceramic inorganic material is preferably larger than that of the metal hydroxide. On the other hand, when only the thermally conductive ceramic inorganic material having a larger particle size than the metal hydroxide which is a flame retardant is used, the thermal conductivity is increased, but if the content is large, there is a possibility that it may settle in the slurry mixture state. In this case, it is possible to solve the sedimentation problem if the filler to be used is pre-treated with a reactive surface treatment agent. Alternatively, another thermally conductive ceramic mineral having a larger or similar particle size than the flame retardant may be added to fill voids between the thermally conductive ceramic inorganic particles having a larger particle diameter, thereby preventing large particles from settling and increasing the thermal conductivity of the thermally conductive adhesive sheet. Can be. Therefore, the thermally conductive ceramic inorganic material according to the present invention includes a first thermally conductive ceramic inorganic material having a particle size larger than that of the metal hydroxide and a second thermally conductive ceramic inorganic material having a particle size smaller than the particle size of the first thermally conductive ceramic inorganic material. It is preferable. The first and second thermally conductive ceramic inorganic materials having different particle diameters may be the same kind or different kinds as long as they are within the range of the thermally conductive ceramic inorganic material.

In the present invention, in order to further increase the dispersing effect of the thermally conductive ceramic inorganic material and the metal hydroxide, it is possible to use a dispersant. Available dispersants may be selected according to the pH of the inorganic material, BYK-Chemie's BYK-168 and the like can be used. The amount used is preferably 0-10 parts by weight based on 100 parts by weight of the inorganic conductive material including the thermally conductive ceramic inorganic material and the flame retardant according to the present invention. If the dispersant is higher than the above content, the dispersant is likely to remain inside the sheet as a residue even after curing of the sheet, causing odor problems or long-term durability problems.

The present invention may also optionally further comprise a crosslinking agent in order to adjust the adhesive properties of the pressure sensitive adhesive. The amount of the crosslinking agent used is preferably about 0.05-5 parts by weight based on 100 parts by weight of the acrylic adhesive resin. Examples of the crosslinking agent that can be used when preparing the pressure-sensitive adhesive of the present invention include polyfunctional acrylates such as 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and 1,2-ethylene Crosslinkable monomers, such as glycol diacrylate or 1,12-dodecanediol acrylate, include, but are not limited to.

In addition, the composition according to the present invention may optionally further use a photoinitiator to control the degree of polymerization of the pressure-sensitive adhesive. The amount of the photoinitiator is preferably used in about 0.01-10 parts by weight based on 100 parts by weight of the acrylic adhesive resin. Photoinitiators that can be used in the preparation of the pressure-sensitive adhesive of the present invention, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, a, a-methoxy-a- Hydroxyacetophenone, 2-benzoyl-2 (dimethylamino) -1- [4- (4-morphonyl) phenyl] -1-butanone, 2,2-dimethoxy-2-phenyl acetophenone, and the like. It is not limited to this.

The thermally conductive adhesives of the present invention are pigments, antioxidants, brighteners, ultraviolet stabilizers, antifoaming agents, thickeners, plasticizers, tackifying resins, phosphorus-nitrogen-containing flame retardants, coupling agents, foaming agents, and polymers so long as they do not affect the effects of the present invention. It may include additives such as micro hollow tools.

The thermally conductive adhesives of the present invention can be prepared using methods in the art using the above-mentioned partially polymerized acrylic adhesive resins, thermally conductive ceramic inorganic and metal hydroxides, and, if necessary, crosslinking agents, photoinitiators and dispersants.

One embodiment of the method for producing a thermally conductive adhesive of the present invention is as follows. A pressure-sensitive adhesive resin having a molecular weight of 10,000-1,000,000 by partial polymerization, preferably thermal partial polymerization, using a (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms alone or a polar monomer copolymerizable with this monomer. It is prepared, and the thermally conductive ceramic inorganic material and metal hydroxide, if necessary, a crosslinking agent and a photoinitiator are added and mixed while stirring so that the thermally conductive ceramic inorganic material and the metal hydroxide are uniformly dispersed in the adhesive resin. In part, a dispersant may be added to uniformly disperse the thermally conductive ceramic inorganic material and the metal hydroxide. Subsequently, the mixture can be photopolymerized by ultraviolet irradiation and crosslinked to produce the thermally conductive adhesive of the present invention.

The present invention also relates to a display device including a backlight unit including the thermally conductive sheet and a light source, and a liquid crystal panel displaying an image using the backlight unit and light.

Hereinafter, with reference to the accompanying drawings will be described in detail preferred embodiments of a backlight unit including a light reflecting foam sheet according to the present invention and a display device having the same.

1 is a cross-sectional view showing a liquid crystal display device using a backlight unit according to an embodiment of the present invention, Figure 2 is a cross-sectional view showing a direct backlight unit according to a preferred embodiment of the present invention, Figure 3 Is a cross-sectional view showing an edge-light type backlight unit according to an embodiment of the present invention.

Referring to FIG. 1, the liquid crystal display device includes a liquid crystal display panel (LCD panel) 200 and a backlight unit 202.

The LCD panel 200 includes a lower polarizing film 204, an upper polarizing film 206, a lower substrate 208, an upper substrate 210, a color filter 212, a black matrix 214, a pixel electrode 216, The common electrode 218, the liquid crystal layer 220, and the TFT array 222 are included.

The color filter 212 includes color filters corresponding to red, green, and blue, and generates an image corresponding to red, green, or blue when light is applied.

The TFT array 222 switches the pixel electrode 216 as a switching element.

The common electrode 218 and the pixel electrode 216 arrange molecules of the liquid crystal layer 220 according to a predetermined voltage applied from the outside.

The liquid crystal layer 220 is composed of predetermined molecules, and the molecules are arranged corresponding to the voltage difference between the pixel electrode 216 and the common electrode 218.

As a result, light provided from the backlight unit 202 below is incident on the color filter 212 corresponding to the molecular arrangement of the liquid crystal layer 220.

The backlight unit 202 is located under the LCD panel 200 and provides light, for example, white light, to the LCD panel 200.

Meanwhile, the BLU 202 is divided into a direct-lighting method in which a light source is positioned below the liquid crystal panel, and an edge-light method in which the light source is located at the side of the light guide plate. Of course, both the direct and edge-right BLU 202 may be used.

First, referring to FIG. 2, the BLU 202a of the direct method includes a light source 302, a transparent acrylic plate 310, a reflective sheet 320, a thermally conductive reflective sheet 350, and an optical film 330. It includes.

The light source 302 may be a plurality of Cold Cathode Fluorescent Lamps (CCFLs), Light Emitting Diodes (LEDs), or External Electrode Flourscent Lamps (EEFLs). Is to use LED. The LED can be composed of red, green and blue or a single color of white light. In the case of the BLU 202a using the LED as a light source, it is possible to maintain the uniformity of light while miniaturizing the BLU 202a and improving the light efficiency.

Unlike the edge-light type, the BLU 202a of the direct type has a plurality of light sources 302 located under the LCD panel 200, so that the bright lines generated from the light source 302 are constant at the top of the LCD panel 200. Will appear as a pattern. At this time, the transparent acrylic plate 310 is formed with a pattern, and serves to pass the light while removing the bright line generated from the light source 302. The transparent acrylic plate 310 preferably uses polymethyl methacrylate (PMMA). However, of course, the BLU 202a according to the present invention may use a transparent acrylic plate on which a pattern is not formed.

The optical film 330 includes a diffusion sheet 332, a prism sheet 334, a protective sheet 336, and a reflective polarizing film 338.

The diffusion sheet 332 diffuses or condenses the incident light to make the luminance uniform and to widen the viewing angle.

The light passing through the diffusion sheet 332 is sharply reduced in brightness, the prism sheet 334 is used to prevent this. The prism sheet 334 collects some of the light diffused or collected by the diffusion sheet 332 toward the protective sheet 336, and reflects the remaining light toward the diffusion sheet 332.

The protective sheet 336 is positioned on the prism sheet 334 to prevent scratches of the prism sheet 334 and to widen the viewing angle narrowed by the prism sheet 334.

The reflective polarizing film 338 reflects a part of the light diffused by the protective sheet 336 toward the light source 302, and provides the remaining light to the LCD panel 200 (FIG. 1). That is, the reflective polarizing film 338 passes specific polarized light and reflects the other polarized light. For example, the reflective polarizing film 338 transmits longitudinal waves (P waves) of light diffused by the protective sheet 336, and transverse waves (S waves) are reflected in the light guide plate direction.

The transverse wave reflected by the reflective polarizing film 338 is reflected back by the reflective sheet 320. In this case, due to the physical properties of the light, the re-reflected light includes longitudinal and transverse waves.

That is, the transverse wave reflected by the reflective polarizing film 338 is changed to light including the transverse wave and the longitudinal wave by being reflected back by the reflective sheet 320.

Subsequently, the changed light passes through the diffusion sheet 332, the prism sheet 334, and the protective sheet 336 and is incident back to the reflective polarizing film 338.

As a result, the longitudinal wave of the changed light is transmitted through the reflective polarizing film 338, and the transverse wave is reflected in the diffusion sheet 332 direction.

Subsequently, the reflected light is reflected back by the reflective sheet 320 to be converted into light including longitudinal waves and transverse waves.

In addition, both the protective sheet 336 and the reflective polarizing film 338 may be used as described above, and any one may be selectively used. The BLU 202a repeats this process to improve the light efficiency.

On the other hand, the reflective sheet 320 is located under the light source 302 serves to reflect the light from the light source 302 to the front surface of the transparent acrylic plate 310. In addition, the light source 302 is mounted by placing a light source reflector (not shown) under the light source 302 instead of the reflective sheet 320, and the light emitted from the light source 302 is incident on the diffusion sheet 332 to provide light efficiency. It can also be configured to improve.

The thermally conductive adhesive sheet 350 according to the present invention may be located below the reflective sheet 320, but is not limited thereto. In this case, heat generated from the light source is transferred to the thermally conductive adhesive sheet 350 according to the present invention through the reflective sheet 320, and the adhesive sheet may effectively release heat due to excellent thermal conductivity.

In the thermally conductive adhesive sheet 350, the thermally conductive adhesive according to the present invention is sheeted on one or both surfaces of the substrate.

It is preferable that especially the thickness of the said thermally conductive adhesive is 50 micrometers-3mm, and thermal conductivity is 2.5 W / mK or more. When the thickness of the pressure-sensitive adhesive is thinner than 50 μm, the heat transfer contact area is small, making it difficult to achieve sufficient heat transfer between the heating element and the heat dissipation sheet.

In addition, the substrate constituting the thermally conductive adhesive sheet is not particularly limited, but may be selected from the group consisting of plastic, paper, nonwoven fabric, glass, and metal, and it is preferable to use a polyethylene terephthalate (PET) film.

The thermally conductive adhesive sheet according to the present invention can be easily produced by a known method. One embodiment of the method is as follows. In the partially polymerized resin prepared from the (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms and a polar monomer copolymerizable with the monomer, the above-mentioned thermally conductive ceramic inorganic material and metal hydroxide, crosslinking agent, photoinitiator and dispersant are added if necessary. Stirring mixing produces a mixture with a viscosity of 1,000-40,000 cP. Subsequently, after apply | coating this mixture to a base material, photopolymerization and bridge | crosslinking by ultraviolet irradiation can be advanced and a thermally conductive adhesive sheet can be manufactured. By applying the mixture on one side or both sides to the substrate, the pressure-sensitive adhesive of the present invention can be used as a single-sided or double-sided tape.

Next, referring to FIG. 3, the edge-light BLU 202b includes a light source unit 300, a light guide plate 340, a reflective sheet 320, a thermally conductive adhesive sheet 350, and an optical film 330. do.

The light source unit 300 includes one or more light sources 302 and a light source reflector 304. The light source 302 generates light having a predetermined wavelength. On the other hand, the light source 302, as described above in the direct BLU 202a, of course, can be used CCFL, LED or EEFL.

The light source reflector 304 reflects the light generated from the light source 302 toward the light guide plate 340 to increase the amount of light incident on the light guide plate 340.

In addition, the optical film 330 includes a diffusion sheet 332, a prism sheet 334, a protective sheet 336, and a reflective polarizing film 338.

Light uniformly diffused in the light guide plate 340 passes through the diffusion sheet 332. The diffusion sheet 332 diffuses or condenses the light passing through the light guide plate 340 to make the luminance uniform and widen the viewing angle.

Hereinafter, since the structures and characteristics of the prism sheet 334, the protective sheet 336, and the reflective polarizing film 338 are the same as described above in the BLU 202a of the direct method, the following description is omitted.

On the other hand, the light generated by the light source 302 is reflected by the light source reflecting plate 304 and the reflecting sheet 320, after which the reflected light is uniformly spread throughout the light guide plate 340.

The reflective sheet 320 is positioned below the light source 300 to reflect light from the light source 302 to the front surface of the light guide plate 340. Heat generated in the light source unit 300 in the light generation process is transferred to the thermally conductive adhesive sheet 350 according to the present invention through the reflective sheet 320 located below, the adhesive sheet is effectively heat due to the excellent thermal conductivity Can emit.

Hereinafter, the light emission operation of the LCD element will be described in detail.

Referring back to FIG. 1, the BLU 202 provides the LCD panel 200 with plane light that is white light. Subsequently, the TFT array 222 switches the pixel electrode 216. Subsequently, a predetermined voltage difference is applied between the pixel electrode 216 and the common electrode 218, so that the liquid crystal layer 220 is arranged corresponding to the red color filter, the green color filter, and the blue color filter, respectively.

In this case, the amount of light is adjusted while the plane light provided from the BLU 202 passes through the liquid crystal layer 220, and the plane light whose light amount is adjusted is provided to the color filter 212. As a result, the color filter 212 implements an image with a predetermined gray scale. In detail, the red color filter, the green color filter, and the blue color filter form one pixel, and the pixels implement a predetermined image by a combination of light passing through the red color filter, the green color filter, and the blue color filter. do.

Hereinafter, the following examples, which present preferred embodiments to aid the understanding of the present invention, are merely illustrative of the present invention and the scope of the present invention is not limited by the following examples.

Example

Example  One

95 parts by weight of 2-ethyl hexyl acrylate (based on 100 parts by weight of acrylic monomer, the same as below) and 5 parts by weight of acrylic acid as a polar monomer are partially polymerized as heat in a 1 liter glass reactor to have a solid content of 15% and a molecular weight of A 100,000-thick adhesive resin was obtained. 0.2 parts by weight of Igacure-651 (a, a-methoxy-a-hydroxyacetophenone) as a photoinitiator and 0.5 parts by weight of 1,6-hexanediol diacrylate (HDDA) as a crosslinking agent were then sufficiently stirred. . 700 parts by weight of aluminum oxide (AS-10, Showa Denko, Japan) having a particle diameter of about 40 μm and aluminum hydroxide (Showa Denko, H-32ST), having a particle size of about 300 μm as a thermally conductive ceramic inorganic material 300 The parts by weight were mixed and stirred until sufficiently uniform. The mixture was degassed under reduced pressure using a vacuum pump, and then coated on a polyester release film with a thickness of 0.3 mm using a knife coating. The polyester film was then covered over the coating layer to block oxygen. After 5 minutes using a metal halide UV lamp to obtain a thermally conductive adhesive sheet.

Example  2

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1, except that an adhesive resin having a solid content of 5% and a molecular weight of 500,000 was used.

Example  3

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1 except that 0.1 part by weight of BYK-168, which is a basic dispersant, was added.

Example  4

90 parts by weight of 2-ethyl hexyl acrylate and 10 parts by weight of acrylic acid as a polar monomer were used to prepare a pressure-sensitive adhesive resin having a solid content of 15% and a molecular weight of 100,000, except that 0.1 part by weight of basic BYK-168 as a dispersant was added to the slurry mixture. A thermally conductive adhesive sheet was obtained in the same manner as in Example 1 above.

Example  5

Using 95 parts by weight of 2-ethylhexyl acrylate and 5 parts by weight of acrylic acid as a polar monomer, a 15% solids and a molecular weight of 100,000 resins were prepared, and 0.1 parts by weight of a basic dispersant BYK-168 was added thereto, followed by thermally conductive ceramic inorganic material. 400 parts by weight of aluminum oxide (Showa Denko, Japan, AS-10) having a particle diameter of about 40 µm and aluminum oxide (Showa Denko, Japan, AL 45-1) having a particle diameter of about 2 µm, 300 parts by weight A thermally conductive adhesive sheet was obtained in the same manner as in Example 1, except that 300 parts by weight of aluminum hydroxide (Showa Denko, H-32ST) of about 4 μm was used as the weight part and the metal hydroxide.

Example  6

After adding 0.1 parts by weight of basic dispersant BYK-168 to the slurry mixture, 500 parts by weight of boron nitride (MBN) having a particle diameter of about 6 μm as a thermally conductive ceramic inorganic material and aluminum hydroxide having a particle size of about 4 μm A thermally conductive adhesive sheet was obtained in the same manner as in Example 1 except that 300 parts by weight of (Showa Denko, Japan, H-32ST) was used.

Comparative example  One

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1, except that 95 parts by weight of 2-ethylhexyl acrylate monomer and 5 parts by weight of acrylic acid as polar monomers were used without partial polymerization.

Comparative example  2

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1, except that an adhesive resin having a solid content of 5% and a molecular weight of 1.5 million was used.

Comparative example  3

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1, except that an adhesive resin having a solid content of 30% and a molecular weight of 100,000 was used.

Comparative example  4

A thermally conductive adhesive sheet was obtained in the same manner as in Example 1 except that an adhesive resin having a solid content of 30% and a molecular weight of 100,000 was used and 0.1 parts by weight of BYK-168 as a basic dispersant was added thereto.

The content and molecular weight of the adhesive resin used in the Examples and Comparative Examples at all times, the types of the thermally conductive ceramic inorganic or metal hydroxides, their particle diameters and the amount used are shown in Table 1 below.

The physical properties of the thermally conductive adhesive sheets prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were measured by the following method.

1. Viscosity Test

Using the Brookfield digital viscometer (DV-1 +, DV-2 + pro), the prepared mixture was placed at an angle to the bubble-free slurry mixture at an angle, the spindle was connected to a viscometer, grooved, and the RPM was selected. Was measured, the viscosity was found to be about 10% or more confidence interval, and then the viscosity was measured after fixing the value.

2. Thermal conductivity test

The prepared sheet was cut into a size of about 10 mm x 10 mm, and the thermal conductivity of this sample was measured by using a thermal conductivity measuring device (laser flash thermal diffusion, specific heat measuring device) LFA 447 and DSC 204F1 manufactured by Nesch, Germany.

3. Flame retardant test

The produced sheet was subjected to a combustion test based on the UV94V standard to determine flame retardancy. Specific test contents are as follows. The items used to determine the flame retardancy rating were the sum of the first and second burning times of each specimen and the fire extinguishing time, the sum of the first and second burning times of the five specimens, and the flammability of the cotton due to the drop of the flame. . Test specimens are 0.5 inch wide and 5 inch long. As a test method, a single methane blue 3/4 inch single flame was used to contact the specimen for 10 seconds, and then the flame was removed. When the specimen was extinguished, the flame was again contacted for 10 seconds and the flame was removed again. . The flame retardant grade is determined based on the table below.

4. Machinability Test

When the prepared slurry mixture is tilted and dropped onto the polyester release film for knife coating, the slurry mixture does not flow due to high viscosity, or after falling, the viscosity does not differ by more than 20% based on the thickness to be coated. Judgment is as follows.

○: flows well and the thickness is uniform.

X: It does not flow well and thickness is nonuniform (more than 20% of target coating thickness

Difference).

5. Double sided adhesiveness

The prepared sheet is cut to a size of about 30 mm × 30 mm, pressed with a force of 800 g with a spherical probe, and then lifted out to measure the maximum force and energy. The front and rear surfaces of the sample were measured by measuring the front and rear surfaces of the sample and the surface of the inorganic filler was settled.

○: less than 20%

X: front and back difference 20% or more

The results of the physical property measurement by the method described above are shown in Table 2 below.

As shown in Table 2, in the case of Example 1 using an acrylic adhesive resin having a solid content of 15%, a molecular weight of 100,000, and no dispersant, the acrylic polymer having a solid content of 5% and a molecular weight of 500,000 Viscosity of the slurry mixture was slightly lower than that of Example 2, but both examples had no problem in preparing a pressure-sensitive adhesive sheet of uniform thickness. In Example 3 using the dispersant as an additive, the thermal conductivity was slightly reduced compared to Example 1, but the viscosity of the slurry mixture was reduced, and the workability was very good. In the case of Example 4 in which the content of acrylic acid was increased by changing the composition of the acrylic monomer, the slurry viscosity slightly increased compared with Example 3, but there was no problem in sheet processing, and thermal conductivity was slightly increased. Example 5 used by changing the composition of the thermally conductive ceramic inorganic material having two kinds of particle diameters, although the slurry viscosity is higher than that of Example 4, the metal oxides having a small particle diameter are filled in the pores between the metal oxides having large particle diameters, thereby increasing the thermal conductivity by increasing the filling rate. A rise was also seen. In the case where boron nitride was used instead of aluminum oxide having a large particle diameter, the workability was not large and thermal conductivity was also excellent. In Comparative Example 1 using only the acrylic monomer, compared to Example 1, the viscosity of the slurry mixture was so low that the filler subsided, so that coating and processing were possible, but the adhesiveness of both sides of the prepared pressure-sensitive adhesive sheet was different. Long-term reliability may be a problem when used to attach parts to components. In addition, the thermal conductivity in the thickness direction becomes nonuniform, making it difficult to achieve uniform heat transfer. In Comparative Example 2 using a partially polymerized acrylic adhesive resin having a solid content of 5% and a molecular weight of 1,500,000, the viscosity of the slurry mixture was sharply increased, so that a sheet could be partially manufactured, but it was uneven and could not be used as a real product. . In Comparative Example 3 using an acrylic resin having a solid content of 30% and a molecular weight of 1,000,000, the viscosity of the slurry mixture was higher than that of Example 1, so that the workability was not so good that it was difficult to prepare a sheet, and the solid content was 30 In Comparative Example 4 in which a resin having a molecular weight of 500,000 and a dispersant was added, the viscosity of the slurry mixture was higher than that of Example 3, making it difficult to process a sheet having a uniform thickness.

The pressure-sensitive adhesive of the present invention controls the solids content and molecular weight of the acrylic adhesive resin in order to increase the filling efficiency to obtain high thermal conductivity, and at the same time, by varying the monomer composition, by controlling the interaction with the inorganic material to reduce the viscosity, processing and molding Increasing the properties, and by including a thermally conductive ceramic inorganic material and a metal hydroxide having a different particle diameter was able to increase the thermal conductivity as well as flame retardancy by filling the pores between the large particles of inorganic particles. Specifically, the pressure-sensitive adhesive of the present invention was excellent in processability and formability in the case of slurry mixture with a viscosity of 1,000-40,000 cP. In addition, when the thermal conductivity of the sheet having a thickness of 0.3mm was measured, it was found to exceed 2.5 W / mK.

As described above, the heat conductive adhesive of the present invention having excellent processability and moldability, heat conductivity, and flame retardancy, generates heat of an electronic component such as a liquid crystal display panel using an organic light emitting diode, which requires a strict standard performance for the above characteristics, as a backlight. The heat generated by the heat transfer to the back can be used without damaging the components.

Claims (19)

a) partially polymerized acrylic adhesive resin having a solid content of 20% or less; b) thermally conductive ceramic minerals; And c) comprises metal hydroxides, The thermally conductive ceramic inorganic material is contained in the 500-1,500 parts by weight based on 100 parts by weight of the acrylic adhesive resin. The heat conductive adhesive composition according to claim 1, wherein the acrylic adhesive resin has a weight average molecular weight of 10,000 to 1,000,000. The heat conductive material according to claim 1, wherein the acrylic adhesive resin comprises 100 parts by weight of a (meth) acrylic acid ester monomer having an alkyl group having 1 to 12 carbon atoms and 0 to 20 parts by weight of a polar monomer copolymerizable with the monomer. Pressure-sensitive adhesive composition. The (meth) acrylic acid ester monomer is ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acryl. A thermally conductive adhesive composition, characterized in that at least one selected from the group consisting of latex, 2-ethylhexyl (meth) acrylate and isononyl (meth) acrylate. The heat conductive adhesive composition according to claim 3, wherein the polar monomer is at least one selected from the group consisting of (meth) acrylic acid, maleic acid, fumaric acid, acrylamide, N-vinyl pyrrolidone, and N-vinyl caprolactam. The thermally conductive adhesive composition according to claim 1, wherein the thermally conductive ceramic inorganic material is at least one selected from the group consisting of aluminum oxide, magnesium oxide, calcium oxide, calcium carbonate, boron nitride, aluminum nitride, and silicon carbide. delete The heat conductive adhesive composition according to claim 1, wherein the metal hydroxide is at least one selected from the group consisting of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide. The heat conductive adhesive composition according to claim 1, wherein the metal hydroxide is included in an amount of 200-1,500 parts by weight based on 100 parts by weight of the acrylic adhesive resin. The thermally conductive adhesive composition according to claim 1, wherein the particle diameter of the thermally conductive ceramic inorganic material is 1-100 m, and the particle size of the metal hydroxide is 0.1-50 m. The heat conductive adhesive composition according to claim 10, wherein the particle diameter of the thermally conductive ceramic inorganic material is larger than that of the metal hydroxide. 12. The thermally conductive ceramic inorganic material of claim 11, wherein the thermally conductive ceramic inorganic material includes a first thermally conductive ceramic inorganic material having a particle size larger than that of a metal hydroxide and a second thermally conductive ceramic inorganic material having a particle size smaller than that of the first thermally conductive ceramic inorganic material. Thermally conductive adhesive composition, characterized in that. The heat conductive adhesive composition according to claim 1, further comprising at least one selected from the group consisting of a dispersant, a crosslinking agent and a photoinitiator. A heat conductive adhesive sheet in which the heat conductive adhesive according to any one of claims 1 to 6 and 8 to 13 is sheeted on one or both surfaces of the substrate. The heat conductive adhesive sheet of Claim 14 whose thickness of a heat conductive adhesive is 50 micrometers-3 mm, and whose thermal conductivity is 2.5 W / mK or more. The heat conductive adhesive sheet according to claim 14, wherein the substrate is selected from the group consisting of plastic, paper, nonwoven fabric, glass, and metal. A thermally conductive adhesive sheet according to claim 14; And A backlight unit comprising a light source. The method of claim 17, The light source is a backlight unit, characterized in that the organic light emitting diode. A backlight unit according to claim 17; And Display device including a liquid crystal panel for displaying an image using light.

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