JP2559934C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reflector having a highly reflective metal thin film laminated on a flexible base material. The application of the reflector according to the invention is a reflector such as a mirror which is easily manufactured. The reflector of the present invention can be easily attached to a glass plate such as a window, a door or a windshield, or a plastic plate or a metal plate by using an adhesive, an adhesive or a double-sided tape. The present invention relates to a reflector having significantly improved durability, and to a reflector (a lamp house or the like) of a fluorescent lamp as a backlight of a liquid crystal display panel of a word processor or a computer having high reflectance and high reliability. Can be used. Further, it is useful as a reflector of a fluorescent lamp utilizing high reflectance for energy saving of office lighting. [0003] A light-reflective film based on a plastic film is lighter, more excellent in impact resistance and more excellent in flexibility than a mirror based on glass. It is used for processing copiers, solar heat collectors, light reflectors in plant factories, high light reflectors for fluorescent lamps, and reflectors for backlights in liquid crystal display devices by processing those bonded to an aluminum plate. I have. Conventionally, these reflectors are polished aluminum plates and stainless plates,
What laminated | stacked the thin film of metals, such as aluminum and silver, on a plastic film is used. However, coatings made of aluminum vapor-deposited products, stainless steel plates, resins, and the like have low reflectance and are completely inadequate. In addition, a light reflector with a silver thin film layer formed on a general-purpose plastic film has high reflectivity when manufactured, but due to environmental factors such as heat and light, the reflectivity of the reflector is remarkably reduced due to ultraviolet rays, especially. However, there is a technical problem that the function as a reflector of the backlight is not satisfied. SUMMARY OF THE INVENTION An object of the present invention is to provide a reflector having excellent durability and high reflectance. Means for Solving the Problems The present inventors laminate a thin film of a metal containing silver on a flexible substrate having a transmittance of light having a wavelength of 380 to 300 nm of 10% or less. As a result, it was found that the durability was improved without lowering the reflectance of the reflector, and the present invention was completed. That is, in the present invention, a flexible substrate serving as a base material of a reflector has a transmittance of 10% or less of light having a wavelength of 380 to 300 nm, and one side of the flexible substrate is used. And a metal thin film containing silver. The flexible substrate used in the present invention has a light transmittance of a wavelength of 550 nm of 7 nm.
The transmittance is preferably 0% or more, preferably 80% or more, and the transmittance of light having a wavelength of 380 to 300 nm is 10% or less, preferably 1% or less. As a preferred flexible substrate used in the present invention, a film or sheet made of a homopolymer or copolymer having a transmittance of 10% or less of light having a wavelength of 380 to 300 nm or an ultraviolet absorber is mixed. A certain plastic film or sheet, such as a plastic film or sheet on which a layer for cutting ultraviolet rays such as an ultraviolet absorber or zinc oxide is formed. Preferred examples of the flexible substrate include biaxially stretched polypropylene containing an ultraviolet absorbent, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and acrylic resin. , Methacrylic resin, polyetheretherketone, polyarylate, polyetherimide and the like. In particular, PET containing an ultraviolet absorber is preferably used. The thickness of the plastic film is preferably thinner from the viewpoint of the cost reduction of the reflector or the productivity at the time of imparting the functionality, and the thickness is preferably reduced from the winding property (handling property) at the time of imparting the functionality. Thick ones are easy to handle. The preferred range of the film thickness is 5 μm or more, more preferably 25 μm or more, and preferably 250 μm or less. In a preferred embodiment of the present invention, a silver thin film layer is laminated on PET containing an ultraviolet absorbent, and the method for forming the thin film includes plating, vacuum deposition, sputtering, ion plating, and the like. Ionization evaporation, ion cluster beam evaporation, or the like can be used. The thickness of the silver-containing metal thin film layer is preferably from 200 to 5000 °, more preferably from 500 to 2000 °. More preferably, it is 800 to 1500 °. The fact that the metal thin film layer containing silver contains trace amounts of metals and metal compounds other than silver does not impair the object of the present invention. Further, a metal layer having anticorrosion properties can be formed as the outermost layer of the metal thin film layer. In the reflector of the present invention, a transparent protective layer may be provided on the plastic film opposite to the metal layer. With such a protective layer, the influence of external environmental factors such as surface hardness, light resistance, gas resistance, and water resistance of the reflector can be further suppressed. Examples of the substance that can be used for forming such a protective layer include, for example, an acrylic resin such as polymethyl methacrylate, a polyacrylonitrile resin, a polymethacrylonitrile resin, and a silicon resin such as a polymer obtained from ethyl silicate. In addition to organic substances such as polyester resin and fluororesin, inorganic substances such as silicon oxide, zinc oxide, and titanium oxide are useful. In particular, the transmittance of light having a wavelength of 400 nm or less, preferably 380 nm or less, is reduced to 10% or less. It is preferable to stack those having the ability to cut. The method for forming the transparent protective layer includes coating, lamination of a film, and the like. Further, these film thicknesses need to be within a range in which a protective effect is exhibited without deteriorating the light reflecting ability, which is the object of the present invention, and may be appropriately changed depending on the material and use. Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 A silver (1000 °) thin film layer was formed by DC magnetron sputtering on a 50 μm-thick biaxially stretched polyethylene terephthalate film provided with a layer (5 μm) containing a benzotriazole-based ultraviolet absorber. Then, a reflector was obtained. Table 1 shows the transmittance of light with wavelengths of 380, 350 and 300 nm before forming the silver thin film layer.
And FIG. 1-1. This reflector was subjected to an ultraviolet light degradation promotion test (specifically, the reflector was irradiated with ultraviolet light having a wavelength of 400 to 315 nm), and the reflectance of incident light having a wavelength of 600 nm was reduced to the initial value.
The time required to reach 80% was measured as the deterioration time. Table 2 shows the results and the reflectance before the test for accelerating UV degradation. As can be seen, the degradation time was reduced to 50 with little decrease in reflectivity.
It had excellent durability of at least 00 hr. Comparative Example 1 A thin silver film having a thickness of 1000 mm was formed on a normal biaxially stretched polyethylene terephthalate film having a thickness of 50 μm in the same manner as in Example 1. 380 before forming silver thin film layer
, 350 and 300 nm are shown in Table 1 and FIGS. The reflector turned red-purple after 100 hours of irradiation with ultraviolet light, and the reflectance was reduced to 80% of the initial value by irradiation with 400 hours of ultraviolet light, indicating that the durability to ultraviolet light was extremely poor. Example 2 A silver (1200 °) thin film layer was formed on a 50 μm thick acrylene film (manufactured by Mitsubishi Rayon) by vacuum evaporation to obtain a reflector. The transmittances of light having wavelengths of 380, 350, and 300 nm before forming the silver thin film layer are shown in Table 1 and FIG. Table 2 shows the results of the ultraviolet degradation promotion test performed in the same manner as in Example 1. As in Example 1, it had excellent light reflectance and durability. Example 3 On a 50 μm thick Tetron HB film (manufactured by Teijin), in the same manner as in Example 1,
A 1000 mm thick silver thin film was formed to obtain a reflector. The transmittances of light having wavelengths of 380, 350 and 300 nm before forming the silver thin film layer are shown in Table 1 and FIG. An evaluation test was performed in the same manner as in Example 1, and Table 2 shows the results. As in Example 1, it had excellent light reflectance and durability. Example 4 The film used in Example 2 was attached to the opposite surface of the light reflector produced in Comparative Example 1 with a silicone adhesive. Table 1 shows the transmittance of light having wavelengths of 380, 350 and 300 nm. An evaluation test was performed in the same manner as in Example 1, and Table 2 shows the results. As in Example 1, it had excellent light reflectance and durability. [Table 1] [Table 2] As shown in the examples, the present invention has remarkably improved the reliability as a reflector by improving the durability against light, heat and the like. The reflector of the present invention is lightweight, has excellent impact resistance, is flexible, is used as a mirror, is a reflector for saving power in a plant factory, and is a high-reflection fluorescent lamp of an energy-saving type. ,
It is also used effectively as a high-brightness reflector for a backlight for a liquid crystal display panel.

[Brief description of the drawings]     FIG.   3 shows the light transmittance of a flexible substrate used in the present invention.     [Explanation of symbols]   1 Light transmittance of films of Example 1 and Example 3   2 Light transmittance of the film of Example 2   3. Light transmittance of film of comparative example

Claims (1)

Claims: 1. A benzotriazole-based ultraviolet absorber, which has a wavelength of 380 to 300.
A liquid crystal display in which an initial reflectance at 600 nm of 90% or more is obtained by laminating a metal thin film containing silver on one surface of a flexible substrate having a light transmittance of 10% or less at 10 nm.
Reflector for reflecting the light source of the panel .