JP4343659B2 - Infrared radioactive resin-coated aluminum reflector with excellent workability - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a light reflecting material for a display device, and relates to a liquid crystal display device such as a liquid crystal television, a notebook computer, and a monitor, or a reflecting material for a bulletin board, an advertisement light, and a lighting device, and particularly suitable for a display device with a large amount of heat generation. It is.

  A liquid crystal display device is mainly used as the reflecting material, and since it is thin and light, it has been widely used in recent years for large-sized liquid crystal televisions, notebook computers, monitors and the like. A liquid crystal display device places a light source such as a cold cathode tube or a hot cathode tube on the back side of the liquid crystal, diffuses the light from the light source to obtain a uniform contrast, and further reflects on the back side of the light source to increase the reflection efficiency. The backlight unit structure is provided with a plate.

Conventionally, as a reflector for these liquid crystal displays,
(1) An aluminum plate obtained by attaching a white film to an aluminum plate using an adhesive or the like,
(2) Aluminum plate with white coating,
Etc. are used. The opposite surface of the reflecting surface of the reflecting material was a chemical conversion coating alone or a clear protective coating provided on the chemical conversion coating for the purpose of corrosion protection. In addition, the display devices used so far do not require much display brightness because monochrome display is the mainstream, but in recent years, the output of a backlight light source has also been increased in order to increase display brightness as the color and size of liquid crystal displays increase. It's getting higher. As a result, the amount of heat generation also increases, and the variation in the display device, particularly the backlight unit room, increases as the temperature rises partially and as a result, the result is a display device such as color imbalance and non-uniform contrast. Problem has occurred.

  In order to solve this problem, a highly heat radiating reflecting material has been proposed in which the surface opposite to the reflecting surface of the reflecting material is anodized to form a heat radiating surface. (Patent Document 1)

JP-A-5-241148

  However, when an anodizing treatment is applied to the surface opposite to the reflecting surface of the reflecting material to form a heat radiating surface, this anodized film is an inorganic film. Happens. As a result, the quality problem that the corrosion resistance of the processed part is inferior, and in the case of a large crack, there is a problem that the product value is lost and the productivity is lowered and the cost is increased. Further, since an anodizing process is necessary, the cost is originally high, and there is a strong demand for a reflector that is low in cost and good in workability and heat dissipation.

  For this reason, the present inventors have provided a chemical conversion film on the aluminum plate, a specific white resin film on the reflective surface side, and a black resin film on the heat radiation surface side, thereby improving reflectivity and heat dissipation. The inventors have found that the processability can be improved without lowering, and have further researched to complete the present invention.

  That is, the invention according to claim 1 is a white film having a film thickness of 30 to 150 μm, containing 70 to 150 parts by weight of a white pigment with respect to 100 parts by weight of the resin on the chemical film on one side of the aluminum plate having a chemical film on both sides. A coating comprising at least one or two or more selected from a fluororesin, an epoxy resin, a polyester resin, an acrylic resin, and a urethane resin on the other surface of the conversion coating on the reflective surface provided with the resin coating An infrared radiation-resin-coated aluminum reflector excellent in processability, characterized by having a heat radiation surface having a thickness of 1 to 50 μm and a black resin film having an infrared emissivity of 50% or more.

  The invention according to claim 2 is an infrared radiation resin-coated aluminum reflector excellent in workability, wherein the black resin film has a surface roughness (Ra) of 0.5 to 5.0 μm. .

  The resin-coated aluminum reflective material of the present invention has good reflectivity and heat dissipation and is excellent in workability, and is particularly suitably used as a reflector for a backlight of a liquid crystal display.

  In the present invention, the aluminum plate of the substrate is not particularly limited, but has sufficient strength to form and hold the backlight unit, and has sufficient formability during drawing and bending. 1000 series, 3000 series, 4000 series, 5000 series aluminum plates are preferred.

  The chemical conversion film provided on the aluminum material is not particularly limited, but a reactive chemical film having good adhesion is used for both aluminum and the resin film. Rather than providing a heat-dissipating film directly on an aluminum material as in the above-mentioned Patent Document 1, by providing a chemical conversion film between aluminum and the resin film layer, the coating film adhesion is remarkably improved, and as a result, workability is improved. Will improve. The reactive chemical conversion film is specifically a film formed with a treatment liquid such as phosphate chromate, chromate chromate, zirconium phosphate, and titanium phosphate. In particular, a phosphoric acid chromate-treated film is preferable in terms of cost and versatility.

  The white resin film provided on the chemical conversion film contains 70 to 150 parts by mass of a white pigment with respect to 100 parts by mass of the resin. White pigments generally have the property of reflecting visible light and infrared light. The white resin film on the reflecting surface reflects visible light from a reflective point and releases heat from the opposite heat radiating surface from the point of heat dissipation, so it is better to absorb infrared rays. If the content of the white pigment is large, the reflectivity (reflection of visible light) is good, but the heat dissipation (infrared absorption) is deteriorated. In general, the resin has a property of absorbing infrared rays. However, when the content of the white pigment is increased, the ratio of the resin component is relatively decreased and the heat dissipation is deteriorated. Therefore, there is an optimum range for the content of the white pigment. That is, if the content of the white pigment is less than 70 parts by mass with respect to 100 parts by mass of the resin, the total reflectance is reduced, and if the content of the white pigment exceeds 150 parts by mass with respect to 100 parts by mass of the resin, Heat is not absorbed well, and as a result, heat dissipation is reduced.

  The type of white pigment in the white resin film is not particularly limited, and for example, titanium oxide, zinc white, zinc sulfide, barium sulfate, calcium carbonate, and the like are used. In particular, titanium oxide is preferable in terms of cost, versatility, and safety.

  The resin used for the white resin film is not particularly limited. For example, one or two or more kinds such as a fluorine resin and an acrylic resin having good weather resistance, a polyester resin and an epoxy resin having good workability are used. It is done. Moreover, either a single layer or a multilayer structure may be used.

  When the thickness of the white resin film is 30 to 150 μm, the total number of white pigments that reflect visible light in the coating film is small when the thickness is less than 30 μm, and as a result, the total reflectance is reduced. This is because the resin layer having inferior thermal conductivity becomes too thick, a heat insulating effect is generated, and heat transfer to the heat radiating surface is not performed well, resulting in a decrease in heat dissipation.

  On the other hand, a black resin film having an infrared emissivity of 50% or more is formed on the chemical conversion film on the other surface of the surface coated with the white resin film. The infrared emissivity is particularly preferably 60% or more. Radiant heat from the opposite surface of the reflector for liquid crystal display devices has a peak at a wavelength of 8 to 10 μm according to Planck's distribution rule, and improving the heat radiation in the infrared region is effective for improving heat dissipation. Therefore, if the infrared emissivity is less than 50%, the heat dissipation effect is insufficient. This infrared emissivity is achieved by a combination of the type of resin used, the type and amount of pigment to be contained, the film thickness, the surface roughness of the film, and the like.

  Moreover, the thickness of the said black resin film layer shall be 1-50 micrometers. If it is less than 1 μm, the number of black pigments having the property of absorbing infrared rays is insufficient, and a sufficient heat dissipation effect cannot be expected. On the other hand, if it exceeds 50 μm, the thermal conductivity is lowered, resulting in poor heat dissipation.

  As the black resin film, one or more selected from fluorine resin, epoxy resin, polyester resin, acrylic resin, and urethane resin are used. Among these, when a fluorine resin, an epoxy resin, or a polyester resin is used, a high degree of workability can be obtained. Fluorine-based and polyester-based resins have high infrared absorption ability, and heat dissipation is further improved by using these.

  The black pigment in the black resin film is included because it has the property of appearing black because it absorbs visible light and generally also absorbs infrared light. The type is not particularly limited, and for example, carbon black, graphite, and iron oxide-based and copper-chromium-based metal oxides are used. One or more of these pigments are used. In particular, carbon black is preferable in terms of cost, versatility, and safety. The total content of these pigments is preferably 1 to 200 parts by mass with respect to 100 parts by mass of the resin.

  The black resin film preferably has a surface roughness (Ra) of 0.5 to 5.0 μm. When the surface roughness is large, the surface area is increased, so that the heat radiation area is increased and the heat dissipation is improved. If it is less than 0.5 μm, the surface area does not increase sufficiently and the effect of improving heat dissipation is small. On the other hand, when the thickness exceeds 5.0 μm, the surface roughness is generally adjusted by adding fine particles, and the workability such as dropping of fine particles during processing and cracking of the coating film starting from the fine particles is deteriorated. The surface roughness (Ra) can be adjusted by adding an appropriate amount of organic fine particles such as acrylic beads, urethane beads and nylon beads, or inorganic fine particles such as silica.

  In addition, the reflective surface and heat radiating surface paints used in the present invention include solvents, leveling agents, pigment dispersants, anti-waxing agents that are usually used in paints to ensure the paintability and general performance as a precoat material. A lubricant imparting agent or the like may be used as appropriate.

  Hereinafter, the present invention will be described in detail with reference to examples.

  An aluminum plate (material: JIS A1100, plate thickness: 1.0 mm) is degreased with a commercially available aluminum degreasing agent, washed with water, and then treated with a commercially available phosphoric acid chromate treatment solution. The paint was applied with a roll coater under the conditions shown in Table 1 and baked at a PMT (maximum ultimate plate temperature) of 200 ° C. The black resin films of Invention Examples 12 to 14 were made to contain acrylic beads having an appropriate particle diameter to adjust the surface roughness of the coating film. Thus, an infrared radiation resin-coated aluminum reflecting material for a liquid crystal reflecting plate schematically shown in FIG. 1 was produced. In the figure, 1 is a white resin film, 2 is a chemical conversion film, 3 is an aluminum alloy plate, and 4 is a black resin film.

  The obtained infrared radiation resin-coated aluminum reflector for liquid crystal reflector was subjected to a performance test by the following test method.

Total reflectance is a multi-light source spectrocolorimeter MSC-IS-2DH (using an integrating sphere, diffused light illumination 8 ° direction light reception) manufactured by Suga Test Instruments Co., Ltd., and the total reflectance at a wavelength of 550 nm (including a regular reflection component). Was expressed as a percentage when the BaSO ₄ white plate was taken as 100. Since it is used for a liquid crystal reflection plate, it is suitable that the total reflectance is 90% or more, and 90% or more is set to a usable level.

With regard to molding processability, 180 ° 3T bending was performed with the evaluation surface on the outside, and cracks in the resin film layer were observed visually. A: No crack in coating film, B: Very slight crack in coating film was good , Δ: Evaluation was made based on the criteria that a small coating film was cracked but usable, and x: a large coating film cracked and not usable.
Further, after the observation of the crack, the cellophane tape was brought into close contact with the bent portion, the degree of peeling of the coating film was observed when the tape was abruptly peeled, and evaluation was made according to the criteria of ○: no peeling and x: peeling.

For heat dissipation, a case was prepared by the following method, the temperature inside the case was measured, and evaluated according to the following criteria: A: 27 ° C. or lower, ○: 28-29 ° C., Δ: 30-31 ° C., x: 32 ° C. or higher. did. A casing having a bottom surface of 150 mm × 150 mm and a height of 200 mm is produced from the obtained infrared reflecting resin-coated aluminum reflecting material for a liquid crystal reflector, and only the top surface of the casing is made of an acrylic plate in order to obtain the same state as the liquid crystal display device. did. The produced housing is shown in FIG. In the figure, 5 is glass, 6 is liquid crystal, 7 is an acrylic diffusion plate, 8 is a light source (cathode tube), 9 is a reflection plate, 10 is a white resin film, 11 is an aluminum alloy plate, and 12 is a black resin film. A 60 W bulb as a light source was placed inside the case, energized to emit light and generate heat, and the ambient temperature inside the case when the temperature inside the case reached a steady state was measured.
The obtained performance test results are shown in Table 2.

  As is apparent from the results shown in Table 2, Examples 1 to 14 of the present invention are good in all of the reflectance of the reflecting surface, the molding processability, the molding processability of the heat dissipation surface, and the heat dissipation. Among them, Examples 12 to 14 of the present invention that also satisfy the roughness condition of claim 2 have particularly good heat dissipation.

  On the other hand, No. which is a comparative example. 15-No. 19 and the conventional example No. No. 20 is inferior in total reflectance of the reflecting surface, molding processability, molding processability of the heat radiating surface, and heat dissipation, and is not suitable as an infrared radiation resin-coated aluminum reflecting material for a liquid crystal reflector. That is, no. No. 15, the white resin film is thin, the number of white pigments in the coating film reflecting visible light is not sufficient, and the total reflectance is inferior. No. No. 16 has a thick white resin film, which reduces the thermal conductivity of the reflecting surface, resulting in poor heat dissipation. No. No. 17 is inferior in total reflectance because the content of white pigment that reflects visible light in the white resin film is small. No. No. 18 has a high white pigment content in the white resin film and a large number of white pigments that reflect infrared rays, while the resin component that absorbs infrared rays is reduced and heat dissipation is poor. No. No. 19 is an epoxy resin whose infrared absorptivity is worse than that of the polyester resin, and the film thickness is thin and the emissivity of the black resin film is low, so that the infrared radiation is not sufficient and the heat dissipation is inferior. No. No. 20 is inferior in moldability because the anodic oxide film on the heat radiation surface is very hard.

It is sectional drawing which shows typically the infrared radiation resin-coated aluminum reflecting material of this invention. It is sectional drawing which shows typically the liquid crystal display device using the reflecting material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 White resin film 2 Chemical conversion film 3 Aluminum alloy plate 4 Black resin film 5 Glass 6 Liquid crystal 7 Acrylic diffuser plate 8 Light source (cathode tube)
9 Infrared radioactive resin-coated aluminum reflector 10 White resin film 11 Aluminum alloy plate 12 Black resin film

Claims (2)

A reflecting surface on which a white resin film having a film thickness of 30 to 150 μm containing 70 to 150 parts by mass of a white pigment is added to 100 parts by mass of a resin on a chemical film on one side of an aluminum plate having a chemical film on both sides, On the other side of the chemical film, the film has a film thickness of 1 to 50 μm and is infrared with at least one selected from fluorine resin, epoxy resin, polyester resin, acrylic resin, and urethane resin. An infrared radiation resin-coated aluminum reflector excellent in workability, characterized by having a heat radiation surface with a black resin film having an emissivity of 50% or more. The infrared radiation resin-coated aluminum reflector excellent in processability according to claim 1, wherein the black resin film has a surface roughness (Ra) of 0.5 to 5.0 μm.

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