Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-12-26
2004-02-03
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S644000, C428S647000, C428S648000, C428S407000
Reexamination Certificate
active
06686041
ABSTRACT:
TECHNICAL FIELD
The present invention relates to coloring master pellets for obtaining a colored optical molded article. More specifically, it relates to coloring master pellets for obtaining a colored optical molded article which has an excellent design and whose kind and application can be recognized instantaneously. That is, the present invention relates to coloring master pellets which can provide a colored optical molded article having little fading phenomenon, color non-uniformity and color streaks as well as excellent electric properties (such as writability and readability of information).
In the present specification, “coloring master pellets” indicate colorant-containing pellets which are mixed with transparent (colorant-free) pellets and melt-molded to give a colored optical molded article. Therefore, the coloring master pellets are not used for obtaining a colored optical molded article by melt-molding the coloring master pellets alone. Further, “coloring master composition” refers to a colorant-containing resin composition used for forming the coloring master pellets.
In addition, “full coloring pellets” refer to colorant-containing pellets used for obtaining a colored optical molded article by melt-molding the pellets themselves (or melt-molding the pellets without transparent pellets).
BACKGROUND ART
Heretofore, as a method for coloring an optical recording medium by use of the full coloring pellets, an orange optical recording medium comprising a specific dye has been proposed in Japanese Patent Laid-Open Publication No. 1-102505 and black optical recording media have been proposed in Japanese Patent Laid-Open Publication Nos. 2-33742 and 8-124212. Further, an optical disk colored by use of an extremely low concentration of coloring master pellets has been proposed in Japanese Patent Laid-Open Publication No. 7-262606. The terms “extremely low concentration” as used herein mean that the content of a colorant is extremely low.
Meanwhile, a method for inhibiting the generation of silver streaks at the time of producing an optical disk by controlling the amount of fine powders in pellets is disclosed in Japanese Patent Publication No. 6-18890. Further, it is disclosed in Japanese Patent Laid-Open Publication No. 11-342510 that an optical disk using pellets having a low content of fine powders has good electric properties.
However, coloring master pellets for obtaining an optical molded article which have relatively high coloring concentration are subjected to larger influences of the separation of the coloring pellets and the fine powders than the transparent pellets, the full coloring pellets and the extremely low concentration of coloring master pellets and have caused the new problem that when the coloring master pellets are mixed with the transparent pellets to mold an optical molded article such as an optical disk, the optical molded article undergoes a fading phenomenon, has color non-uniformity and color streaks and undergoes a deterioration in its electric properties.
Meanwhile, the transparent pellets, full coloring pellets and extremely low concentration of coloring master pellets disclosed in the above publications are not satisfactory for solving the above problem pertaining to the coloring master pellets.
PROBLEM TO BE SOLVED BY THE INVENTION
The present invention relates to coloring master pellets capable of providing a colored optical molded article such as a colored optical disk substrate which has an excellent design, whose kind and application can be recognized instantaneously and which has little fading phenomenon, color non-uniformity and color streaks as well as good electric properties. It is particularly an object of the present invention to provide coloring master pellets suitable for obtaining an optical disk from which information signals are optically read by means of a laser beam. The present inventors have made intensive studies to achieve the object. As a result, they have found that coloring master pellets which satisfy particular requirements can achieve the object of the present invention and have completed the present invention based on the finding.
That is, the present inventors have studied what causes color non-uniformity and color streaks and what causes a decrease in the reliability of reading and writing information signals when the coloring master pellets are mixed with the transparent pellets and melt-molded into an optical molded article. As a result, they have found that variations among the concentrations of colorant of each pellet in the coloring master pellets are one of the causes and that a colored optical molded article having the occurrence of the color non-uniformity and the color streaks extremely suppressed and the reliability of reading and writing the information signals maintained at a high level can be obtained by reducing the variations among the concentrations to a certain level or lower.
Further, according to the studies of the present inventors, it has been found that when the obtained coloring master pellets having the variations among the concentrations of the colorants in the pellets reduced to a certain level or lower satisfy either of the following requirements (1) and (2), the pellets have extremely excellent properties for obtaining a colored optical molded article, particularly a colored optical disk substrate.
(1) The content of powders whose particle diameters are smaller than the desired shapes of the pellets by at most 2.0 mm, particularly at most 1.0 mm is equal to or lower than a certain content.
(2) The number of foreign materials contained in the pellets is small.
MEANS FOR SOLVING THE PROBLEMS
The present invention has been completed by the above finding. According to the present invention, there are provided coloring master pellets for an optical molded article which are formed from a coloring composition comprising a transparent thermoplastic resin (component A) containing a colorant (component B), wherein the proportion of pellets having colorant concentrations which satisfy a range of 0.5X to 1.5X when the concentrations of the colorants in the pellets are indicated in terms of absorbance and the average concentration is expressed as X is at least 90%.
The optical molded articles in the present invention include a lens, an optical card, an optical fiber and an optical disk, and the optical disk is particularly suitable. The optical disk is a so-called optical disk which information is written on and read from by irradiation of a laser beam. Specific examples thereof include a variety of read-only disks, recordable disks, magneto-optical disks and phase change disks such as a digital audio disk (so-called compact disk: CD), CD-ROM, optical video disk (so-called laser disk), DVD-ROM, digital video disk (DVD-video), DVD-R, CD-R, MO, MD-MO, PD and DVD-RAM. The coloring master pellets of the present invention are useful and suitable particularly for the production of a digital versatile disk which is a high-density optical disk typified by the DVD-ROM, DVD-video, DVD-R, DVD-RAM or the like. Further, the coloring master pellets of the present invention are the most suitable for use in the CD-R and DVD-R.
As the thermoplastic resin which is the component A in the present invention, a thermoplastic resin selected from an aromatic polycarbonate resin, an amorphous polyolefin resin, an acrylic resin, a hydrogenated polystyrene resin, an amorphous polyester resin, an amorphous polyarylate resin and the like is preferably used. The aromatic polycarbonate resin or the amorphous polyolefin resin is more preferable. Illustrative examples of the amorphous polyolefin resin include the APO resin manufactured by Mitsui Chemicals, Inc.; ARTON manufactured by JSR Corporation; Zeonex and Zeonor manufactured by ZEON CORPORATION; and the HPS resin manufactured by Dow Chemical Company. The aromatic polycarbonate resin is particularly preferred.
The details of the aromatic polycarbonate resin suitable as the component A of the present invention will be described hereinafter. The aromatic polycarbonate resin
Ninomiya Hideo
Sakamoto Akihiro
Shimizu Hisayoshi
Le H. Thi
Sherman & Shalloway
Teijin Chemicals Ltd
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