JP4792755B2 - Reflective material - Google Patents

Description

  The present invention relates to a reflector used in a backlight unit of a liquid crystal display device such as a personal computer or a television.

  Reflective materials are used in various fields, and are used in the vicinity of light sources such as fluorescent lamps, and in recent years, are used in backlight units of liquid crystal display devices such as personal computers and televisions. As a reflective material for these liquid crystal display devices, a particularly high-brightness reflectance is required. However, since conventional white polyester films and polyolefin films are mass-produced, surface treatment is performed to improve light resistance. There is a problem that the process becomes complicated and the efficiency becomes poor.

JP-A-4-239540 JP 20000004157409 A

  The present invention has been made to solve such problems, and the object of the present invention is to provide a reflective material that can be easily surface-treated and has excellent reflection performance. .

The present invention is for solving such problems, and the invention according to claim 1 is characterized in that a foam layer composed of an aqueous emulsion and a white pigment is provided on a base sheet , and a coating layer is provided on the foam layer. Thus, the total reflectance at 550 nm is 98% or more, and the base material sheet is a resin layer having a thickness of 10 to 500 μm.

  The invention according to claim 2 is the reflecting material according to claim 1, wherein the surface of the foam layer is embossed.

  The invention described in claim 3 is the reflector according to claim 1, wherein a fluorescent brightening agent is added to the foamed layer.

  According to the first aspect of the invention, the use of the aqueous emulsion increases the degree of freedom in design and enables embossing. As the foaming means, chemical foaming and mechanical foaming can be appropriately selected, and various foaming agents can be selected to control foaming. It is also possible to cure while mechanically foaming with a stirrer. Further, when adding a fluorescent brightening agent, which will be described later, it can be easily spread over the entire emulsion layer.

  According to the second aspect of the present invention, it is possible to design an emboss pattern appropriately changed according to the environment in which the reflector is installed, thereby avoiding problems such as reflection of a cold cathode tube for a backlight, for example. It becomes easy.

  According to the third aspect of the present invention, ultraviolet light can be absorbed by mixing a fluorescent brightening agent, which contributes to an improvement in reflectance.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a cross-sectional structure of an embodiment of the reflector of the present invention. A foamed layer 2 made of an aqueous emulsion and a white pigment is provided on a base sheet 1, and an emboss 3 is applied on the surface thereof. Moreover, you may provide the light-resistant coating layer 4 on the surface suitably.

  The substrate sheet 1 in the present invention is not particularly limited as long as it is a sheet-like material such as a resin film or paper and can be continuously provided with a foamed layer. In the case of paper, if it is considered to be incorporated in an electronic component in a later process, various problems will be caused if the contents are generated by punching, so synthetic paper or impregnated paper, Polypropylene laminated sand paper or the like is preferable. In consideration of the reflection characteristics, those colored white are preferable to those not exposed. In the case of a film, the resin includes polyester, polyolefin, polyimide, polyurethane, etc. in consideration of processability. Also, polyvinyl alcohol, polyamide, polystyrene, etc. can be used depending on the application.

  Examples of the polyester-based resin include polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyacrylonitrile, and the like, and non-crystalline polyester, so-called A-PET. Moreover, what is called PET-G etc. which modified | denatured the ethylene glycol used for a normal polyethylene terephthalate with 1, 4- cyclohexane dimethanol is mentioned. In the film using these polyester-type resins, the foamed polyester film which made it foam at the time of extending | stretching and made the density low is mentioned.

  As the polyolefin resin, polyethylene and polypropylene are often used. In the polyethylene system, the density ranges from a low density to a high density type, and there are films in which the rigidity of the film is changed. In the polypropylene system, there are a stretched film and a foamed film other than a normal cast film.

  Although it does not limit whether the base material which consists of these films is colored, it is desirable to knead a white pigment similarly to the foaming layer mentioned later. As a white pigment, titanium oxide is common, but there are barium sulfate, calcium carbonate, calcium silicate, zinc oxide and the like.

  Although the thickness of the base sheet 1 is not particularly limited, it is better to take into account the light reflection characteristics, but if it is too thick, it becomes difficult to provide a foam layer to be described later continuously with a roll. preferable. In particular, if processing with a roll is not performed, there are plate-like substrates such as plate-like cardboard, plastic cardboard, thermoplastic resin substrates, and other thermoplastic resin structures.

The foam layer 2 in the present invention comprises an aqueous emulsion and a white pigment. An acrylic emulsion is often used as the aqueous emulsion, but is not particularly limited, and an acrylic ester resin, an ethylene-vinyl acetate copolymer, or a mixture thereof is used as a raw material for the acrylic emulsion.
The acrylic ester is composed of a mixture of alkyl acrylate, alkyl methacrylate and the like.
Moreover, as an acrylic emulsion, the method of superposing | polymerizing with a polyfunctional grafting agent can also be used, mix | blending alkyl acrylate, alkyl methacrylate, and a monoethylenic monomer.

As the foaming method of the foamed layer in the present invention, chemical foaming or mechanical foaming is possible.
Although it does not specifically limit in chemical foaming, it is common to use an organic foaming agent. For example, for an ethylene vinyl alcohol-based resin or an acrylic emulsion-based resin, a capsule foaming agent having a core part of hydrocarbon and a shell part of acrylonitrile is suitable. On the other hand, azodicarbonamide is suitable for foaming vinyl chloride resin. The addition amount of the foaming agent is preferably about 0.5 to 25%. Moreover, about 150-200 degreeC is calculated | required as foaming temperature.
In mechanical foaming, a thickener or the like is appropriately added to adjust the viscosity. Moreover, it is calculated | required to make it harden | cure from drying so that a bubble may not lose | disappear.
Thus, the reflectance as a reflecting material improves by making it foam. However, if the foaming is too much, the cohesive force of the foamed resin becomes small and weak against wear, and the weathering resistance of the foaming agent is not good, and discoloration due to light occurs over time. Therefore, the foaming ratio is adjusted as appropriate.

  As the white pigment, titanium oxide is generally used, but barium sulfate, calcium carbonate, calcium silicate, zinc oxide and the like are also possible. Addition of the white pigment improves the reflectance as a reflective material, particularly in the visible light region.

  The thickness of the foamed layer 2 is not particularly limited, but it is desired that the foamed layer 2 has a certain thickness in consideration of the reflectivity. However, if the thickness is too thick, there is a problem in continuous processability and post-processability. ˜2000 μm is preferred.

  Further, the emboss 3 of the foamed layer 2 is preferably applied. In particular, the embossing of satin reduces the proportion of the specular reflection component of the total light reflectance, thereby reducing the phenomenon of cold cathode tube reflection when the reflector of the present invention is used for a backlight. I can do it.

Further, it is preferable to add a fluorescent brightening agent to the foam layer 2. As the optical brightener, stilbene, coumarin, oxador, or a mixture thereof is used. It is desired that the reflectance of the reflective material of the present invention is greatly improved by the fluorescence emission. However, if the addition amount is too large, the surface weather resistance deteriorates, causing yellowing and a decrease in reflectance over time. Therefore, an addition amount of about 0.1 to 5% with respect to the resin is suitable.

  Moreover, you may provide the light-resistant coating layer 4 on the surface of the foaming layer 2 suitably.

  A transparent polyester film (manufactured by Toyobo Co., Ltd .: “E5131” 100 μm) was used as the base sheet 1. To this, 200 μm of resin prepared as the foaming layer 2 with the following blending ratio was coated with a comma coater, coated at a furnace temperature of 120 ° C. and foamed at 160 ° C., and then heat embossed, A reflector was obtained.

Ethylene-vinyl acetate copolymer 75 parts Acrylic ester 25 parts Capsule foaming agent 10 parts White pigment (titanium oxide) 30 parts Fluorescent whitening agent 5 parts

  A reflective material of the present invention was obtained in the same manner as in Example 1 except that a white polyester film (manufactured by Mitsubishi Plastics Co., Ltd .: “Diacle Rail” 200 μm) was used as the base sheet 1.

0.5 parts by weight of triazole UV absorber “TINUVIN328” (manufactured by Nagase Sangyo Co., Ltd.) and hindered amine stabilizer “TINUVIN123” (Nagase Sangyo Co., Ltd.) per 100 parts by weight of acrylic ester on the surface The reflective material of the present invention was obtained in the same manner as in Example 2 except that 0.5 g by weight of the product was added and coating was performed at 5 g / m ² .

  When the reflective material obtained in the example was measured with a spectrophotometer (Shimadzu Corporation “UV-2500PC”), the reflectance at 550 nm was 98% in Example 1, and Example 2 and Example 3. 99%. In the same measurement method, the reflectance of the white foamed polyester film (188 μm), which is a commercially available reflective material, was 96%, and that of the white foamed polypropylene film (180 μm) was 96%.

It is explanatory drawing which shows the structure of the cross section of one Example of the reflecting material in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material sheet 2 ... Foam layer 3 ... Emboss 4 ... Light-resistant coating layer

Claims (3)

A foam layer composed of an aqueous emulsion and a white pigment is provided on a base sheet, and a coating layer is provided on the foam layer . The total reflectance at 550 nm is 98% or more, and the base sheet has a thickness of 10 to 500 μm. Reflective material characterized by being a resin layer. The reflective material according to claim 1, wherein a surface of the foam layer is embossed. The reflective material according to claim 1, wherein a fluorescent whitening agent is added to the foam layer.

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