Illumination – Light modifier – Reflector
Reexamination Certificate
2001-12-13
2003-10-07
O'Shea, Sandra (Department: 2875)
Illumination
Light modifier
Reflector
C362S296040, C362S516000, C428S458000, C525S444000
Reexamination Certificate
active
06629769
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyester resin compositions used for light-reflecting molded articles. More specifically, the invention relates to a polyester resin composition from which a molded article having a highly glossy surface is produced with a relatively small amount of gas generated in the molding process. The small amount of generated gas allows a light-reflecting metal layer to be formed directly on the molded article without undercoating therebetween. The resultant molded article is excellent in specular reflection properties and luminous brightness and further excellent in maintenance of its surface appearance when used under high temperatures (i.e. thermal resistance) as well as adhesiveness to the metal layer. The light-reflecting metal layer is formed on the molded article by coating and/or vapor deposition.
The polyester resin composition according to the present invention is suitably used for lamp-related parts in the fields of automobile, building equipment and various industries. In particular, this polyester resin composition is suitably used for lamp reflectors, extensions and the like which are lamp-related parts of automobiles required to have high surface luminous brightness, smoothness and light reflectance.
2. Description of the Background Art
A light reflector, particularly for an extension, for example, which is one of lamp-related parts of an automobile is usually required to have high luminous brightness and smoothness, uniform light reflectance, high thermal resistance and the like for the directional and reflective properties of a lamp source. Accordingly, a crystalline thermoplastic polyester resin which is superior in mechanical and electrical properties as well as physical and chemical properties and further excellent in processability has been used as a material from which such a reflector is produced. In particular, a polybutylene terephthalate resin is used solely or used as a mixture thereof with a polyethylene terephthalate resin to which various reinforcing agents are added and blended therewith. A pretreatment such as undercoating is applied to a resultant molded article and thereafter a light-reflecting metal layer is formed thereon by means of vacuum deposition for example and thus a desired light reflector is produced.
The undercoating, however, leads to a considerable increase in cost, and thus a light reflector without undercoating that still exhibits a high luminous brightness and has a highly dense deposited layer is desired. In order for a reflector, which is formed of a molded article having at least one surface provided with a light-reflecting layer without undercoating therebetween, to have a high luminous brightness and a uniform reflectance, it is necessary that the resin molded article itself exhibits a superior surface smoothness as well as high gloss and luminous brightness.
Moreover, in terms of applications of the reflector, the thermal resistance of resin is an important issue. In general, the polybutylene terephthalate resin has a high crystallization speed and thus is solidified relatively quickly in a mold. Therefore, it is difficult to achieve a satisfactory specular transcription. In addition, when inorganic fillers such as talc and mica are added to the resin for providing a thermal resistance thereto, such fillers could be isolated and become visible (appearance on the surface). Then, according to a method employed for producing a molded article excellent in gloss and surface properties, the method being devised in consideration of materials for the molded article, an amorphous polymer is added to the polybutylene terephthalate resin in order to lower the crystallization speed thereof and thus improve the mold transcription and further prevent the filler from being isolated and becoming visible (appearance on the surface).
There are also methods devised in consideration of the molding process. For example, according to one of such methods generally employed, the resin temperature is increased to enhance the flowability. According to another method, the mold temperature is increased to lower the crystallization speed and thus improve the mold transcription. Although those methods improve the appearance of the molded article to some degree, the increased resin temperature and the increased mold temperature result in a noticeable generation of gas in the molding process and accordingly cause any defect in the appearance such as tarnishing (haze) on the surface of the molded article. Therefore, these methods cannot successively produce satisfactory molded articles and require additional polishing, wiping and the like of the mold. Further, the addition of the amorphous polymer deteriorates, if the amorphous polymer itself has a low thermal resistance, the surface and luminous brightness properties of the molded article when used under high temperatures, so that the molded article employed as a light reflector has a deteriorated thermal resistance level. Moreover, an amorphous polymer with a high glass transition temperature generally has a low solublity with respect to the polybutylene terephthalate resin so that superior surface properties are impossible to achieve.
SUMMARY OF THE INVENTION
One object of the present invention is to produce a polyester resin composition used for a light-reflecting molded article having an excellent luminous brightness and a high reflectance as well as a satisfactory adhesiveness to metal even if a light-reflecting metal layer is directly vapor-deposited on a resin molded article without undercoating, and further having a thermal resistance which allows such properties to be maintained when the molded article is used under high temperatures. In order to accomplish this object, the inventors of the present invention have conducted dedicated studies to achieve the present invention.
The present invention is a light-reflecting molded article constituted of a molded article made from a polyester resin composition and a light-reflecting metal layer formed on the molded article. The light-reflecting molded article has an average surface roughness of at most 0.3 &mgr;m and a deflection temperature under load of at least 160° C.
The present invention is a polyester resin composition from which a molded article is made, a light-reflecting metal layer being formed on the molded article to produce a light-reflecting molded article. The polyester resin composition includes 100 parts by weight of polybutylene terephthalate resin (component A) and 1 to 100 parts by weight of polyalkylene naphthalate resin (component B).
According to the present invention, the polybutylene terephthalate resin (component A) has a content of carboxyl group at the end of polymer chain that is at most 70 meq/kg.
Preferably, at least 75% by molar fraction of a 1,4-butanediol unit is contained in the total diol component of the polyalkylene naphthalate resin (component B).
According to the invention, the polyester resin composition includes 100 parts by weight of polybutylene terephthalate resin (component A) and 1 to 50 parts by weight of polyalkylene naphthalate resin (component B).
Preferably, the light-reflecting metal layer is formed by vapor deposition to exhibit specular gloss. Still preferably, metal in the light-reflecting metal layer is aluminum.
Moreover, according to the present invention, the molded article has at least a part thereof on which the light-reflecting metal layer is directly formed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A polyester resin composition according to the present invention has a structure described in detail below.
The present invention is a light-reflecting molded article constituted of a molded article made from a polyester resin composition and a light-reflecting metal layer formed
Kosugi Satoshi
Nakanishi Koji
Yoshihara Nori
Alavi Ali
O'Shea Sandra
Toyo Boseki Kabushiki Kaisha
LandOfFree
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