KR101233678B1 - Reflective foamed sheet for lcd - Google Patents

Abstract

PURPOSE: A reflective foamed sheet for an LCD is provided to remarkably improve reflectivity, to have excellent thermal conductivity, and to effectively solve a heating problem in a back light unit. CONSTITUTION: A reflective foamed sheet(20) for an LCD comprises a core layer(21) with a plurality of bubbles(24), and skin layers(22,23) formed on both sides of the core layer. The core layer comprises 10-25 parts by weight of titanium dioxide, and 3-10 parts by weight of talc based on 100.0 parts by weight of thermoplastic resin. The core layer and the skin layers additionally comprise carbon black powder or acetylene black powder on at least one layer. The BET specific surface area of the acetylene black powder is 100 m^2/g or more.

Description

Reflective foamed sheet for liquid crystal display {Reflective foamed sheet for LCD}

The present invention relates to a reflective foam sheet for a liquid crystal display, and more particularly, to a reflective foam sheet for a liquid crystal display capable of maximizing reflection efficiency while being excellent in heat generation.

In the information display technology, display devices have occupied a position that CRT has been unique for more than half a century. However, in response to the rapidly evolving information age, various types of displays have been developed for technology, and existing CRT methods have been replaced by flat panel displays not only for small measuring instruments but also for various monitors and TVs.

The flat panel display technology has already secured the TV market with liquid crystal display (LCD), projection display and plasma display (PDP), and related technologies such as field emission display (FED) and electroluminescent display (ELD) have been improved. The scope of application will be expanded.

Among them, LCD injects liquid crystal between two sheets of glass and applies power to the electrodes installed on the upper and lower glass plates, and the liquid crystal molecular array is changed at each pixel to display an image. Currently, LCD, personal computer monitor, liquid crystal TV, automobile It is used in aircraft and occupies about 80% of the reputation market.

The LCD display device is usually composed of an LCD panel unit, a driver, and a backlight unit. Unlike other flat panel display methods, the LCD panel is a non-light emitting material, and thus, an additional light emitting device is required to improve the brightness of the display screen.

The additional light emitting device includes a front light type and a back light type light emitting device. The front light method is a method of dimming the display surface by attaching a light source to the front or front side of the display, but as the size of the display increases, there is a technical problem that it is extremely difficult to evenly distribute the light on the front of the display.

Therefore, this method is used for small display devices of 19 inches or less. For example, small 14-inch or smaller devices such as vehicles and laptops have one cold cathode fluorescent tube installed outside the light guide plate and used for monitors and TVs. The 18-inch backlight unit is provided with two or three lamps each outside the light guide plate to increase brightness.

On the other hand, since the light guide plate method cannot display sufficient brightness over 19 inches, a direct method in which a plurality of lamps are arranged at regular intervals under the diffuser plate is used. This method is called a backlight method in such a way that several fluorescent lamps are arranged in a row on the rear surface of the diffusion sheet to improve luminance and improve uniformity than the photometric type.

That is, in the backlight method, the light generated from the light source of the backlight unit attached to the rear side of the display element is led to the opposite side through the light guide plate, and is reflected to a reflector such as a metal deposition plate or an opaque white plate so that the light is emitted to the front surface. As an indirect lighting method for improving the brightness of the screen, it is a light emitting method that can solve the problems of the front light method. Accordingly, the backlight unit refers to a system for implementing the backlight of the LCD, and is largely composed of a lamp, sheets, a mechanism part, and a driving circuit. That is, since only a lamp cannot produce uniform light over the whole area, sheet | seats and mechanism parts, such as a light guide plate, a diffusion plate, a reflecting plate, a prism, and a frame, are provided. In this backlight method, the backlight light source must go through several steps before reaching the LCD, in which it loses its original brightness and loses uniformity of light throughout the screen due to the dispersion effect, so it must be very bright. . As a method for overcoming this problem, the size of the light source can be increased, but there is a problem in that the installation cost is high, the power consumption is high, and the weight is increased a lot. Thus, as far as possible during the transmission process, an attempt to improve the light source brightness without light loss is required.

Accordingly, flat panel display devices such as LCDs or projection TVs have reflective films that play an important role in reaching light from the light source to the viewer's eyes. Reflective film is an optical element that emits light from the horizontal light source lamp on one side or the back of the LCD display to the front of the screen as uniform light and reflects the light from the back toward the panel to improve the efficiency of the light. . In other words, the reflective film is located at the rear to conceal the frame supporting the backlight unit and at the same time prevents light leakage from the backlight and reflects to the front as much as possible to increase the brightness. Therefore, the reflective film needs to have excellent reflectance in order to improve luminance, and low transmittance must be preceded in order to realize sufficient concealment for the frame.

In addition, in recent years, as the flat panel display device becomes more large in size, the light amount of the light source increases, but when the light amount increases, the temperature during use reaches an excessively high temperature. Therefore, the reflective film mounted adjacent to the backlight should satisfy heat resistance and excellent mechanical strength such that thermal deformation of the lamp does not occur.

Meanwhile, referring to FIG. 1, the function of the reflective sheet in the edge type backlight unit is a rod-shaped lamp 11 as a light source, and a rectangular light guide plate 13 disposed so that an end thereof follows the lamp 11. And a plurality of optical sheets 12 stacked on the surface side of the light guide plate 13 and a reflective sheet 16 stacked on the back surface side of the light guide plate 13. Each of the optical sheets 12 has specific optical properties such as refraction and light diffusion, and specifically, the light diffusion sheet 14 and the light diffusion sheet 14 arranged on the surface side of the light guide plate 13. The prism sheet 15 etc. which are arrange | positioned at the surface side of this correspond.

Referring to the function of the backlight unit 10, first, light rays incident on the light guide plate 23 from the lamp 11 are reflected by the reflection dots (not shown) on the rear surface of the light guide plate 13, and thus the light guide plate ( 23) Emitted to the surface. Part of the light beam is behind the light guide plate 13

The light emitted from the back surface is reflected by the reflective sheet 16 and is incident on the light guide plate 13 again. Light rays emitted to the surface of the light guide plate 13 enter the light diffusion sheet 14, are diffused, and are directed to the light diffusion sheet 14 surface.

It is released from the site. Thereafter, the light rays emitted from the light diffusion sheet 14 are incident on the prism sheet 15, and are emitted as light rays of a distribution showing peaks in a substantially normal direction by a prism portion formed on the surface of the prism sheet 15. . In this way, the light rays emitted from the lamp 11 are diffused by the light diffusion sheet 14 and refracted by the prism sheet 15 so as to show a peak in a substantially normal direction, and the upper liquid crystal panel (not shown). Not to illuminate the entire surface.

However, in the case of the conventional foamed reflective sheet, a technique of adding an inorganic filler to improve the reflectance therein has been disclosed, but due to the number of bubbles contained in the foamed reflective sheet, there is a limit in improving the reflectance. In order to overcome this, the content of the inorganic filler added was increased, but in this case, other physical properties such as a decrease in tensile strength were caused.

Furthermore, a cold cathode fluorescent lamp (CCFL) or the like has been mainly used as a light source of the backlight unit. However, as the backlight unit is mounted on a liquid crystal panel and the LCD device emits light, an internal temperature of the LCD device increases and a temperature of the CCFL increases from 80 ° C to 90 ° C. As a result, the efficiency of the backlight unit is lowered, which is a cause of lowering the brightness of the LCD element.

In addition, the LCD using the direct backlight unit is applied to a large LCD TV and a monitor because the light source directly illuminates the substrate and has a high light utilization rate and no limitation in size, and a reflective sheet is positioned below the light source. In this structure, most of the heat generated by the light source is transferred to the reflective sheet. When the reflective sheet is overheated by the transferred heat, there is a concern that deformation of the reflective sheet may occur. In addition, although there is a difference depending on the structure of the backlight unit, heat generated in the CCFL is unevenly transmitted to the liquid crystal panel disposed in front of the backlight unit to generate a temperature deviation between the liquid crystal cells. The temperature deviation between the liquid crystal cells causes a difference in the response speed between the liquid crystal cells, causing the luminance deviation of the LCD element, and may be a major cause of shortening the lifetime of the LCD panel. In particular, as the size and thickness of LCDs progress in recent years, the heat generation of the backlight unit has emerged as a problem that must be solved.

The present invention has been made to solve the above problems, the first problem to be solved of the present invention is to provide a reflective foam sheet for a liquid crystal display and a method of manufacturing the same that can maximize the reflection efficiency.

The second problem to be solved of the present invention is to provide a reflective foam sheet for a liquid crystal display and a method of manufacturing the markedly improved heat generation.

In order to achieve the first object of the present invention, in the reflective foam sheet for a liquid crystal display comprising a core layer including a plurality of bubbles and a skin layer formed on both sides of the core layer, the core layer is a thermoplastic resin 100 It provides a reflective foam sheet for a liquid crystal display comprising 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on parts by weight.

According to a preferred embodiment of the present invention, the thermoplastic resin is polybutylene terephthalate, polyethylene terephthalate, aromatic polyamide, polyamide, polycarbonate, polystyrene, polyphenylene sulfide, thermotropic liquid crystal polymer, polysulfone, poly Ether sulfone, polyetherimide, polyetheretherketone, polyarylate, polymethylmethacrylate, polyvinyl alcohol, polypropylene, polyethylene, polyacrylonitrile butadiene styrene copolymer, polytetramethylene oxide-1,4- Butanediol copolymer, a copolymer containing styrene, fluorine resin, polyvinyl chloride, and polyacrylonitrile may be any one or more selected from the group consisting of.

According to another preferred embodiment of the present invention, the reflective sheet may have a light transmittance of 0 to 3% and a light reflectance of 95 to 99%.

In order to achieve the second object of the present invention, carbon black powder may be further included in at least one of the core layer and the skin layer.

According to a preferred embodiment of the present invention, acetylene black powder may be further included in at least one layer of the core layer and the skin layer.

According to another preferred embodiment of the present invention, the acetylene black powder may have a BET specific surface area of 100 m 2 / g or more.

According to another preferred embodiment of the present invention, the thickness of the core layer may be 400 ~ 600 ㎛ and the thickness of the skin layer may be 10 ~ 30 ㎛.

According to another preferred embodiment of the present invention, (1) preparing a non-foaming sheet comprising 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin; (2) impregnating the non-foamed sheet with 0.01 to 10 parts by weight of a chemical blowing agent, a physical blowing agent or a mixture thereof based on 100 parts by weight of the thermoplastic resin composition; And (3) degassing and foaming the blowing agent impregnated in the sheet. Provides a method of manufacturing a reflective foam sheet for a liquid crystal display comprising a.

According to another preferred embodiment of the present invention, the chemical blowing agent is azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide, 4,4-oxybenzenesulfonyl semicarbazide, p At least one selected from the group consisting of toluenesulfonyl semicarbazide, barium azodicarboxylate, N, N'-dimethyl-N, N'-dynitrosoterephthalamide, and trihydrazino triazine have.

According to another preferred embodiment of the present invention, the physical blowing agent may be an inorganic foaming agent selected from the group consisting of carbon dioxide, nitrogen, argon, water, air, and helium.

According to another preferred embodiment of the present invention, the physical blowing agent is an aliphatic hydrocarbon compound containing 1 to 9 carbon atoms, an aliphatic alcohol containing 1 to 3 carbon atoms, and a halogenated aliphatic containing 1 to 4 carbon atoms. It may be an organic foaming agent selected from the group consisting of hydrocarbon compounds.

According to another preferred embodiment of the present invention, the non-foamed sheet may further include carbon black powder.

According to another preferred embodiment of the present invention, the non-foamed sheet may further include acetylene black powder, more preferably the acetylene black powder may have a BET specific surface area of 100 m 2 / g or more.

The reflective foam sheet for a liquid crystal display including the specific inorganic filler of the present invention can significantly improve the light reflectance as compared to the reflective foam sheet containing the conventional inorganic filler. At the same time, the reflective foam sheet of the present invention has excellent thermal conductivity and can effectively solve the heat generation problem generated in the backlight unit.

While the invention has been described in detail with reference to the described embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the invention, and such variations and modifications fall within the scope of the appended claims. It is also natural.

1 is a cross-sectional view showing a conventional backlight unit.
2 is a cross-sectional view of a reflective sheet according to a preferred embodiment of the present invention.
3 is a cross-sectional view illustrating a liquid crystal display device using a backlight unit according to an exemplary embodiment of the present invention.
4 is a cross-sectional view illustrating a direct type backlight unit according to an exemplary embodiment of the present invention.
5 is a cross-sectional view illustrating a side light type backlight unit according to an exemplary embodiment of the present invention.

As described above, in the case of the conventional foamed reflective sheet, a technique of adding an inorganic filler to improve the reflectance therein has been disclosed, but due to the number of bubbles contained in the foamed reflective sheet, there is a limit in improving the reflectance. In order to overcome this, the content of the inorganic filler added was increased, but in this case, other physical properties such as a decrease in tensile strength were caused.

Accordingly, in the present invention, in the reflective foam sheet for a liquid crystal display comprising a core layer including a plurality of bubbles and a skin layer formed on both sides of the core layer, the core layer is 10 to 10 parts by weight of titanium dioxide based on 100 parts by weight of the thermoplastic resin. By providing a reflective foam sheet for a liquid crystal display comprising 25 parts by weight and 3 to 10 parts by weight of talc, the above-mentioned problem was sought.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings. 2 is a cross-sectional view of a reflective sheet according to a preferred embodiment of the present invention, wherein the reflective sheet 20 has skin layers 22 and 23 formed on both surfaces of the core layer 21.

Specifically, the core layer 21 may be used a thermoplastic resin that is typically used in a reflective sheet, more specifically, the thermoplastic resin is polybutylene terephthalate, polyethylene terephthalate, aromatic polyamide, polyamide, poly Carbonate, polystyrene, polyphenylene sulfide, thermotropic liquid crystal polymer, polysulfone, polyether sulfone, polyetherimide, polyether ether ketone, polyarylate, polymethyl methacrylate, polyvinyl alcohol, polypropylene, polyethylene, poly Acrylonitrile butadiene styrene copolymer, polytetramethylene oxide-1,4-butanediol copolymer, copolymer containing styrene, fluororesin, polyvinyl chloride, and polyacrylonitrile and copolymers thereof Any one or more resins selected from Can be.

On the other hand, according to a preferred embodiment of the present invention, the core layer includes 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin. Specifically, in the case of the conventional reflective foam sheet, an inorganic filler such as titanium dioxide was added in order to improve the reflectance. However, since the reflective foam sheet occupies a substantial portion of the inside, there is a limit to the amount of inorganic fillers that can be added, thereby limiting the improvement of reflectance.

Accordingly, the present invention has found that the reflectance is maximized when 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc are added to 100 parts by weight of the thermoplastic resin. If only one of titanium dioxide and talc is added or one of them is mixed with another inorganic filler, there is a limit to the increase in reflectance (see Table 1). In addition, when the content of titanium dioxide and talc added is outside the above range, it is difficult to expect effective improvement of reflectivity (see Table 1).

On the other hand, the conventional reflective foam sheet has a problem that it is difficult to improve the heat generation. Accordingly, according to a preferred embodiment of the present invention, the reflective foam sheet further includes carbon black powder or acetylene powder in at least one layer of the core layer and the skin layer to significantly improve the exothermic properties. 10 to 50 parts by weight of carbon black powder or acetylene powder may be further added to 100 parts by weight. In this case, it is preferable to include the acetylene powder as compared to the carbon black powder is more advantageous for the improvement of the pyrogenicity, and more preferably, the acetylene black powder is more effective in improving the pyrogenicity of the BET specific surface area of 100 m 2 / g or more. (See Table 1).

The core layer 21 of the reflective foam sheet of the present invention includes a plurality of bubbles 24, and these bubbles may be formed by a physical blowing agent or a chemical blowing agent described later. The volume occupied by the bubble 24 in the core layer 21 is the same as that of a conventional reflective foam sheet, and may preferably occupy 10 to 80% by volume of the entire core layer.

On the other hand, the thickness of the core layer of the present invention may be 400 ~ 600㎛.

On the other hand, preferably, the core layer 21 may include, for example, a curing agent, a plasticizer, a dispersant, various leveling agents, ultraviolet absorbers, antioxidants, viscous modifiers, light stabilizers, lubricants, fluorescent materials, and the like.

Next, the skin layer 22 formed on both surfaces of the core layer 21 will be described. The skin layers 22 and 23 used in the present invention may use the same or different resins as the core layer 21, and include carbon black powder or acetylene black powder in the same manner as the core layer 21 to improve heat generation. can do.

Next, a method of manufacturing the reflective foam sheet of the present invention will be described. The method for producing a reflective foam sheet of the present invention relates to a method for manufacturing a reflective foam sheet using a chemical blowing agent, a physical blowing agent or a mixture thereof in the thermoplastic resin composition. The method is not particularly limited as long as the thermoplastic resin composition penetrates the chemical blowing agent or the physical blowing agent alone or a mixture thereof into the resin and then undergoes a degassing step such as cooling or reduced pressure.

The foam of the thermoplastic resin of the present invention is a continuous foaming process in which the impregnation process of infiltrating a gas known in the art into the resin and the foaming process of degassing and foaming proceed as separate processes, or the continuous impregnation process and the foaming process. It may be prepared by a continuous foaming method performed by, but is not limited thereto.

The said batch foaming method and the continuous foaming method are respectively embodied by the following.

Specifically, (1) preparing a non-foaming sheet comprising 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin; (2) impregnating the non-foamed sheet with 0.01 to 10 parts by weight of a chemical blowing agent, a physical blowing agent or a mixture thereof based on 100 parts by weight of the thermoplastic resin composition; And (3) degassing the foaming agent impregnated in the sheet to foam.

The manufacturing method is a batch type foaming method in which the impregnation step of penetrating the gas known in the art into the resin and the foaming step of degassing and foaming is carried out as a separate process, or the continuous process of continuously performing the impregnation process and the foaming process It can manufacture by a foaming method.

Specifically, the thermoplastic resin composition to which the chemical blowing agent, the physical blowing agent, or a mixture thereof is added may be prepared by a continuous foaming method including the step of simultaneously foaming the thermoplastic resin composition by extrusion or injection.

In the batch foaming method, a non-foaming resin in the form of a sheet made of a resin composition is placed in a high pressure container, and then a foaming agent is penetrated into the container to dissolve the gas in the non-foaming resin. Thereafter, the high pressure vessel is depressurized and the foamless sheet is heated to form a fine foam of resin. Such a batch foaming method can use the molding method and manufacturing apparatus described in US Pat. No. 4,473,665.

In addition, in the continuous foaming method, a foaming agent is added together with the resin during the extrusion or injection process to melt blend, and then a fine foam is formed through rapid pressure drop in the extrusion or injection mold.

The chemical blowing agent is not particularly limited as long as it is a compound that decomposes above a specific temperature to generate a gas, and may be azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide, or 4,4-oxybenzenesulfur. From a group consisting of ponyl semicarbazide, p-toluenesulfonyl semicarbazide, barium azodicarboxylate, N, N'-dimethyl-N, N'-dytrotroterephthalamide, and trihydrazino triazine It is preferred that it is at least one selected.

In addition, the physical blowing agent may be an inorganic foaming agent selected from the group consisting of carbon dioxide, nitrogen, argon, water, air, and helium, preferably supercritical gas, but is not limited thereto.

It may also be an organic foaming agent selected from the group consisting of aliphatic hydrocarbon compounds containing 1 to 9 carbon atoms, aliphatic alcohols containing 1 to 3 carbon atoms, and halogenated aliphatic hydrocarbon compounds containing 1 to 4 carbon atoms.

Specific examples of the above compounds include methane, ethane propane, normal butane, isobutane, normalpentane, isopentane or neopentane as aliphatic hydrocarbon compounds, and methanol, ethanol, normal propanol, or acne as aliphatic alcohols. Isopropanol and the like, and halogenated aliphatic hydrocarbon compounds include methyl fluoride, perfluoromethane, ethyl fluoride, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2 Tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane, penta Fluoroethane, difluoromethane, perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluoro Robutane, Perfluorocyclobutane, Methyl Chloride, Methylene Chloro Ride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane, chlorodifluoromethane, 1,1 -Dichloro-2,2,2-trifluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, trichloromonofluoromethane, dichlorodifluoromethane, trichlorotrifluoro Ethane, 1,1,1-trifluoroethane, pentafluoroethane, dichlorotetrafluoroethane, chloroheptafluoropropane, or dichlorohexafluoropropane.

The amount of the blowing agent is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the thermoplastic resin, but when the content of the blowing agent is less than 0.01 parts by weight, the amount of gas for foaming is too small, so that the foaming effect is insignificant or not expected at all. If the amount exceeds 10 parts by weight, the amount of gas generated is large, resulting in an uneven cell structure or excessively large cell size.

The present invention also relates to a display unit including a backlight unit including the reflective foam sheet for the liquid crystal display 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.

3 is a cross-sectional view showing a liquid crystal display device using a backlight unit according to an embodiment of the present invention, Figure 4 is a cross-sectional view showing a direct type backlight unit according to a preferred embodiment of the present invention, Figure 5 Is a cross-sectional view showing an edge-light backlight unit according to an embodiment of the present invention.

Referring to FIG. 3, 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, the light provided from the backlight unit 202 below corresponds to the molecular arrangement of the liquid crystal layer 220.

Is incident on 212.

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. 4, a direct BLU 202a includes a light source 302, a transparent acrylic plate 310, a reflective sheet 320, a thermal diffusion layer 322, and an optical film 330. do.

The light source 302 is formed of a plurality of cold cathode fluorescent lamps (CCFLs) as an aggregate. The CCFL is a lamp that provides very bright white light. In addition to the CCFL, the light source 302 may include a light emitting diode (LED) or an external electrode fluorescent lamp (EEFL).

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.

The EEFL has a higher luminance than the CCFL and is advantageous in that the electrode is external to operate in parallel. In particular, the EEFL can reduce the number of inverters required by the conventional light source, thereby reducing the cost of components and the weight of the LCD module.

The reflective sheet 320 is positioned under the light source 302 to reflect light from the light source 302 to the front surface of the transparent acrylic plate 310. In this case, due to the combination of the fine foam and the specific additive of the reflective foam sheet 320 for the liquid crystal display according to the present invention provides excellent light reflecting ability, it is possible to effectively release the heat generated from the light source due to excellent thermal conductivity.

Meanwhile, 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.

In addition, since the direct light type BLU 202a has a plurality of light sources 302 located below the LCD panel 200, unlike the edge-light type, a bright line generated from the light source 302 is located at the top of the LCD panel 200. It appears in 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 some of the light diffused by the protective sheet 336 toward the light source 302, and provides the remaining light to the LCD panel. That is, the reflective polarizing film 338 passes a specific polarized light (P) and serves to reflect the other polarized light (S wave). 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.

On the other hand, both the protective sheet 336 and the reflective polarizing film 338 can be used as described above, as well as any one can be selectively used. The BLU 202a repeats this process to improve the light efficiency.

Next, referring to FIG. 5, the edge-light BLU 202b includes a light source unit 300, a light guide plate 340, a reflective sheet 320, a thermal diffusion layer 322, and an optical film 330.

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.

The light generated by the light source 302 is reflected by the light source reflecting plate 304 and the reflecting sheet 320, and then 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 reflective sheet 320 located below. In this case, due to the combination of the fine foam and the specific additive of the reflective foam sheet 320 for the liquid crystal display according to the present invention provides excellent light reflecting ability, it is possible to effectively release the heat generated from the light source due to excellent thermal conductivity.

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 to 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.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

≪ Example 1 >

20 parts by weight of titanium dioxide having an average particle diameter of 290 nm and 7 parts by weight of talc having an average particle diameter of 1 μm were prepared in a masterbatch form with respect to 100 parts by weight of a thermoplastic resin (Polypropylene, MFR = 7 g / 10 min (2.16 kg / 230 ° C.). The resin composition was put into a hopper and nitrogen gas was supplied through a supercritical gas supply line installed at the barrel end of the extruder, the nitrogen supply pressure was fixed at 900 psi and the extruder temperature was set to 170 ° C. The resin temperature was adjusted to about 155 ° C. The screw rotation speed was adjusted to 70 rpm, the discharge amount was about 45 kg / hr, and the nitrogen gas amount was adjusted to 23 g / hr to prepare a 500 µm core layer, and a skin layer having a thickness of 20 µm on both sides of the core layer. It was laminated by the laminating method to prepare a reflective foam sheet.

<Example 2>

A reflective foam sheet was prepared in the same manner as in Example 1 except that 15 parts by weight of titanium dioxide was added.

<Example 3>

A reflective foam sheet was prepared in the same manner as in Example 1 except that 5 parts by weight of talc was added.

&Lt; Comparative Example 1 &

A reflective foam sheet was prepared in the same manner as in Example 1 except that no titanium dioxide was added.

Comparative Example 2

A reflective foam sheet was prepared in the same manner as in Example 1 except that talc was not added.

&Lt; Comparative Example 3 &

Except for adding 7 parts by weight of zirconium oxide instead of talc was carried out in the same manner as in Example 1 to prepare a reflective foam sheet.

&Lt; Comparative Example 4 &

A reflective foam sheet was prepared in the same manner as in Example 1 except that 20 parts by weight of calcium carbonate was added in place of titanium dioxide.

importance reflectivity(%) Thermal Conductivity (W / mK) Example 1 0.75 97.5 0.18 Example 2 0.78 96.8 0.16 Example 3 0.70 95.2 0.19 Comparative Example 1 0.65 48.4 0.15 Comparative Example 2 0.60 79.2 0.16 Comparative Example 3 0.72 80.5 0.19 Comparative Example 4 0.77 93.6 0.19 Example 4 0.75 97.1 0.41 Example 5 0.73 96.8 0.53 Example 6 0.72 96.6 0.37

As can be seen from Table 1 it can be seen that the reflective foam sheet of Examples 1 to 3 satisfying the content range of the titanium dioxide and talc of the present invention has excellent physical properties compared to Comparative Examples 1 to 4 that do not satisfy this.

In addition, it can be confirmed that adding carbon black powder or acetylene powder is very advantageous for improving the thermal conductivity.

Reflective foam sheet for a liquid crystal display of the present invention is significantly improved light reflectance and heat generation can be very useful in the field of optical sheet.

20: reflective sheet 21: core layer
22, 23: skin layer 24: bubble

Claims (14)

delete delete delete As a reflective foam sheet for a liquid crystal display comprising a core layer comprising a plurality of bubbles and a skin layer formed on both sides of the core layer;
The core layer comprises 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin;
Reflective foam sheet for a liquid crystal display, characterized in that it further comprises carbon black powder in at least one of the core layer and the skin layer. As a reflective foam sheet for a liquid crystal display comprising a core layer comprising a plurality of bubbles and a skin layer formed on both sides of the core layer;
The core layer comprises 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin;
Reflective foam sheet for a liquid crystal display, characterized in that it further comprises acetylene black powder in at least one of the core layer and the skin layer. The method of claim 5,
The acetylene black powder is a reflective foam sheet for a liquid crystal display, characterized in that the BET specific surface area of 100 m 2 / g or more. As a reflective foam sheet for a liquid crystal display comprising a core layer comprising a plurality of bubbles and a skin layer formed on both sides of the core layer;
The core layer comprises 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin;
The thickness of the core layer is 400 ~ 600 ㎛ and the thickness of the skin layer is a reflection foam sheet for a liquid crystal display, characterized in that 10 ~ 30 ㎛. A backlight unit comprising the reflective foam sheet according to any one of claims 4 to 7. (1) preparing a non-foaming sheet comprising 10 to 25 parts by weight of titanium dioxide and 3 to 10 parts by weight of talc based on 100 parts by weight of the thermoplastic resin;
(2) impregnating the non-foamed sheet with 0.01 to 10 parts by weight of a chemical blowing agent, a physical blowing agent or a mixture thereof based on 100 parts by weight of the thermoplastic resin composition; And
(3) degassing and foaming the blowing agent impregnated in the sheet; manufacturing method of a reflective foam sheet for a liquid crystal display comprising a. 10. The method of claim 9,
The chemical blowing agents are azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide, 4,4-oxybenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, barium azodicarboxyl Method of producing a reflective foam sheet for a liquid crystal display, characterized in that at least one selected from the group consisting of latex, N, N'-dimethyl-N, N'- dynitrosoterephthalamide, and trihydrazino triazine. . 10. The method of claim 9,
The physical blowing agent is carbon foam, nitrogen, argon, water, air, and a method of manufacturing a reflective foam sheet for a liquid crystal display, characterized in that the inorganic foaming agent selected from the group consisting of helium. 10. The method of claim 9,
The physical blowing agent is an organic foaming agent selected from the group consisting of aliphatic hydrocarbon compounds containing 1 to 9 carbon atoms, aliphatic alcohols containing 1 to 3 carbon atoms, and halogenated aliphatic hydrocarbon compounds containing 1 to 4 carbon atoms. A method of manufacturing a reflective foam sheet for liquid crystal display, characterized in that. The method of claim 4, wherein the thermoplastic resin is polybutylene terephthalate, polyethylene terephthalate, aromatic polyamide, polyamide, polycarbonate, polystyrene, polyphenylene sulfide, thermotropic liquid crystal polymer, Polysulfone, polyether sulfone, polyetherimide, polyether ether ketone, polyarylate, polymethyl methacrylate, polyvinyl alcohol, polypropylene, polyethylene, polyacrylonitrile butadiene styrene copolymer, polytetramethylene oxide- A 1,4-butanediol copolymer, a copolymer containing styrene, a fluorine resin, polyvinyl chloride, and polyacrylonitrile, any one or more selected from the group consisting of a reflective foam sheet for liquid crystal display. The reflective foam sheet for liquid crystal display according to any one of claims 4 to 7, wherein the reflective sheet has a light transmittance of 0 to 3% and a light reflectance of 95 to 99%.

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