JP2004067708A - Powder coating for visible light reflection and reflector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder coating for visible light reflection which always gives a stable white coating surface with little color difference regardless of the amount of the coating in a gas baking oven and imparts, to the coating surface, a stable higher reflectance with little variation in all the wavelength range of visible light of 430-700 nm; and a reflector formed by using the coating. <P>SOLUTION: This powder coating material for visible light reflection comprises a polyester resin with an acid value of 20-80, a solid epoxy compound with an epoxy equivalent of 99-2,000, and titanium oxide with a refractive index ≥2.7. The titanium oxide has a spherical crystal structure, an alumina/silica coating layer formed by a chlorine method treatment, and an average particle diameter of 0.2-0.3 μm and is contained in a content of 15-25% in terms of PVC (38-54% in terms of PWC). The coating may further contain a curing catalyst and an antioxidant, each being a phosphorus-based additive and contained each in a content of 0.02-1 wt.%. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a powder coating for visible light reflection used on a light reflecting surface such as a reflector of a lighting fixture.
[0002]
[Prior art]
For example, in a lighting device such as a fluorescent discharge lamp, a reflector that reflects visible light is provided on the back of the fluorescent lamp or the like, so that light emitted from the fluorescent lamp is reflected in a desired direction. Such a reflection plate is generally formed by applying a white coating to a surface serving as a light reflection surface of a metal plate processed into a desired shape.
[0003]
This white painted surface is formed by a urethane polyester powder coating material mainly combining a polyester resin having a hydroxyl value of 28 and a titanium oxide having a refractive index of 2.7 or more as a white pigment having a high reflectance over a wide range of visible light. This paint is used, and the paint is electrostatically applied to the surface of the metal plate that is to be the reflection surface, and the coated metal plate is placed in a baking furnace and baked.
[0004]
By the way, such a urethane polyester powder coating material is applied, and a baking furnace using LPG or city gas as a heat source (hereinafter, referred to as a gas baking furnace) has an advantage in baking processing that the temperature rises quickly and the cooling at the time of fire extinguishing is quick. And then baking, the painted surface may turn yellow. The degree of this yellowing varies greatly depending on the amount of the metal plate to be baked in the gas baking furnace, in other words, the amount of paint in the gas baking furnace. In addition, there is a problem that the reflectance at the wavelength of 430 nm to 450 nm (the fluorescent lamp has one high spectral power at this wavelength) is reduced by yellowing.
[0005]
When the cause of this problem is investigated, the urethane polyester powder coating contains a volatile component of ε (epsilon) -caprolactam blocked isocyanate as a curing agent and a volatile component of benzoin as a defoaming agent, It has been found that mainly these volatile components are deposited on the surface of the coating film during the baking treatment and are yellowed in synergy with NOx and moisture in the gas baking furnace. (Japanese Patent Application Laid-Open No. 2001-348526) was developed by combining a polyester resin of the formula (1), a solid epoxy compound having an epoxy equivalent of 99 to 2,000, and titanium oxide having a refractive index of 2.7 or more (JP-A-2001-348526).
[0006]
[Problems to be solved by the invention]
This powder coating has particularly improved reflectance in the wavelength range of 430 nm to 450 nm, but has a relatively large decrease in reflectance as the wavelength becomes longer than 550 nm, and the reflectance varies depending on the product. There was a problem.
[0007]
The present invention has been made in view of such circumstances, and reduces volatile components that cause yellowing in a gas baking furnace, and produces a stable white color with a small color difference regardless of the amount of paint in the gas baking furnace. Provided is a powder coating for visible light reflection, which has a coated surface, has a higher reflectance in the entire range of visible light wavelengths of 430 nm to 700 nm, and has a stable reflectance, and a reflection plate formed from the coating. With the goal.
[0008]
[Means for Solving the Problems]
The present invention according to claim 1 is a powder coating for visible light reflection comprising a polyester resin having an acid value of 20 to 80, a solid epoxy compound having an epoxy equivalent of 99 to 2,000, and titanium oxide having a refractive index of 2.7 or more. The titanium oxide has an inert inorganic oxide-containing coating layer having a spherical crystal structure and an average particle diameter of 0.2 to 0.3 μm. Item 1 The present invention according to Item 1, is characterized in that the curing catalyst and the antioxidant each contain 0.02 to 1% by weight of a phosphorus-based additive.
[0009]
According to a third aspect of the present invention, in the first aspect of the present invention, the inert inorganic oxide-containing coating layer is made of titanium oxide made of alumina and silica. In the present invention according to claims 1 to 3, the content of titanium oxide is 15 to 25% by PVC (38 to 54% by PWC).
[0010]
According to a fifth aspect of the present invention, the reflecting surface of the reflecting plate is formed of the powder coating for visible light reflection according to any one of the first to fourth aspects.
[0011]
In the present invention, any one or more of the polyester resins having an acid value of 20 to 80, any one or a plurality of solid epoxy compounds having an epoxy equivalent of 99 to 2,000, and an oxidation having a refractive index of 2.7 or more are used. Since powder coatings are formed by appropriately combining titanium and titanium, powder coatings with a small amount of volatile components can be obtained, in particular, yellowing that occurs during gas baking treatment can be reduced. Regardless of the amount, a stable white painted surface with a small color difference can always be obtained, and titanium oxide has a spherical crystal structure and an inert inorganic oxide-containing coating layer, and the average particle size is 0.2 to 0.1. Since the thickness is 3 μm, it is possible to enhance the reflectance in a wide range of wavelengths from 430 nm to 700 nm. Further, by adding 0.02 to 1% by weight of a phosphorus-based additive as a curing catalyst and an antioxidant, color burning during baking can be greatly reduced.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. As examples, a polyester resin containing a curing catalyst having an acid value of 36 (manufactured by ucb, krill coat 7401) among polyester resins having an acid value of 20 to 80, and an epoxy resin having an epoxy equivalent of 720 g / eq of an epoxy equivalent of 99 to 2,000 (Epomic R-363 manufactured by Mitsui Chemicals, Inc.) and titanium oxide having an average particle diameter of 0.25 μm having a coating layer of alumina and silica treated by a chlorine method as a coating layer containing an inert inorganic oxide having a spherical crystal structure (manufactured by Ishihara Sangyo Co., Ltd.) 38.5 parts by weight of a polyester resin having an acid value of 36, 16.5 parts by weight of an epoxy resin having an epoxy equivalent of 720 g / eq, 43.5 parts by weight of titanium oxide having an average particle size of 0.25 μm, and phosphorus-based 0.5 parts by weight of an antioxidant (SANDOSTAB P-EPQ POWDER manufactured by Clariant Japan), acrylic acid A powder coating is prepared by blending 0.8 parts by weight of a leveling agent (BYK360 manufactured by BYK) and 0.2 parts by weight of a benzoin anti-foaming agent, and the coating is electrostatically applied to a surface of a metal plate to a thickness of about 60 μm. The coated metal plate was placed in a gas baking furnace and baked under the same conditions as during mass production to form a painted surface. At this time, the temperature in the gas baking furnace was 170 ° C., and the baking time was 20 minutes.
[0013]
As a comparative example, a polyester resin having an acid value of 39 among polyester resins having an acid value of 20 to 80 and a solid epoxy compound having an epoxy equivalent of 640 among epoxy equivalents of 99 to 2,000 were selected. A powder that is a combination of about 16 parts by weight of a solid epoxy compound having an epoxy equivalent of 640, about 44 parts by weight of titanium oxide having a refractive index of 2.7 or more, and about 1 part by weight of additives such as a defoaming agent. A paint was prepared, the paint was electrostatically applied to the surface of a metal plate at a thickness of about 60 μm, and the coated metal plate was placed in a gas baking furnace and baked under the same conditions as in mass production to form a coated surface. At this time, the temperature in the gas baking furnace was 180 ° C., and the baking time was 20 minutes.
[0014]
The painted surface after baking is an even surface without irregularities due to the paint in both the examples and the comparative examples. Then, the reflectance with respect to the wavelength of visible light was measured, and the result is shown in FIG. In FIG. 1, a curve P1 shows the reflectance of the example, and a curve P2 shows the reflectance of the comparative example.
[0015]
As is clear from FIG. 1, in the entire wavelength range of 430 nm to 700 nm, the coated surface formed by the coating material of the example has a reflectance higher by 2 to 3% than the coated surface formed by the coating material of the comparative example. I have. That is, it can be seen that, when the reflecting surface of the reflector of the fluorescent discharge lamp is used, the reflectance is further increased, and the illuminance of the fluorescent discharge lamp is improved.
[0016]
For titanium oxide having a spherical crystal structure, titanium oxide having a coating layer of alumina and silica is 15 to 25% by PVC (38 to 54% by PWC), and the average particle size is 0.2 to 0.3 μm (preferably 0.2 to 0.3 μm). It has been confirmed that high reflectance can be obtained if the enemy is 0.25 to 0.28 μm). In addition, the polyester resin containing a curing catalyst having an acid value of 36 is combined with an epoxy resin having an epoxy equivalent of 720 g / eq, which shows a preferable combination in consideration of the paint and the cost required for the painting operation. As the polyester resin, any one or more of the acid values of 20 to 80, and any one or more of the epoxy equivalents of 99 to 2,000 as the solid epoxy compound, for example, a low-oxidation polyester resin and a high epoxy equivalent, respectively. By appropriately combining the solid epoxy compound or the highly oxidized polyester resin with the low epoxy equivalent solid epoxy compound, yellowing similar to that in the examples can be prevented.
[0017]
【The invention's effect】
As described above, since the paint according to the present invention has a very small amount of volatile components, the gas baking furnace can be effectively used, the production cost required for the coating can be reduced, and reflection can be achieved in almost the entire visible light wavelength range. A stable white paint surface with a high rate and little variation between products can be obtained. In addition, a reflector having the painted surface as a reflective surface can more effectively utilize the light emitted from the light source for illumination, and has a highly reliable reflective surface because the reflector has almost no color difference on the painted surface. You can get a board.
[Brief description of the drawings]
FIG. 1 is a characteristic diagram showing the effect of the reflectance on the wavelength of visible light of a surface coated with a paint according to an embodiment of the present invention.
[Explanation of symbols]
P1 Curve showing reflectance by the paint of the present invention P2 Curve showing reflectance by the conventional paint

Claims (5)

A visible light reflecting powder coating comprising a polyester resin having an acid value of 20 to 80, a solid epoxy compound having an epoxy equivalent of 99 to 2,000, and titanium oxide having a refractive index of 2.7 or more, wherein the titanium oxide has a spherical crystal structure. A powder coating for visible light reflection, characterized in that the coating has an inert inorganic oxide-containing coating layer and has an average particle size of 0.2 to 0.3 μm. 2. The powder coating for visible light reflection according to claim 1, which contains 0.02 to 1% by weight of a phosphorus-based additive as a curing catalyst and an antioxidant, respectively. The powder coating for visible light reflection according to claim 1, wherein the inert inorganic oxide-containing coating layer is a titanium oxide comprising alumina and silica. The powder coating for visible light reflection according to claim 1, wherein the content of titanium oxide is 15 to 25% by PVC. A reflector having a reflecting surface formed by the powder coating for visible light reflection according to any one of claims 1 to 4.

Images