JPS61206628A - Resin disk - Google Patents

Abstract

PURPOSE:To obtain a resin disk, the dimensional change due to temperature of which is small and consequently is applicable to precision machinery field such as high density magnetic disk, optical disk and the like by a structure wherein the titled resin disk consists of polymer enabling to form anisotropic melt and the linear expansion coefficient of the diameter of which is 10<-5>( deg.C<-1>) or less. CONSTITUTION:The titled resin disc consists of polymer enabling to form anisotropic melt with the linear expansion coefficient of the diameter of 10<-5>( deg.C<-1>) or less. The resin disc is obtained by injection-molding polymer, which enables to form anisotropic melt, by using a circular molding tool with a gate at the center. The reason why the linear expansion coefficient of the diameter of the disc is small is that the orientated liquid crystal polymer resin has not only small linear expansion coefficient in the direction of orientation but also small cubical expansion coefficient. Concretely, the linear expansion coefficient in the direction of orientation is as small as of the order of 10<-6>( deg.C<-1>) and there is a possibility that the cubical expansion coefficient is of negative value. The resin disk with extremely small linear expansion in diameter is considered to be obtained by the result of the sum of said small expansion coefficients.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a circular resin plate having an extremely small coefficient of linear expansion in diameter, and more specifically relates to a circular resin plate that is formed into an anisotropic melt by melt injection molding. This invention relates to a circular resin plate with an extremely small coefficient of linear expansion obtained by orienting a liquid polymer radially from its center.

(Prior art) With the development of polymer chemistry, molded products using thermoplastic resins such as polystyrene, polyethylene, polypropylene, vinyl chloride, and nylon have become deeply embedded in our daily lives and have become indispensable to us. And recently, aviation, space, nuclear power, acoustics, electronics,
With technological innovations in automobiles and the like, there has been a demand for molded products with excellent characteristics commensurate with each technology.

One of them is a circular resin plate with a small linear expansion in diameter.

In a circular resin plate obtained by molding a general resin, the coefficient of linear expansion in diameter is at most 2 Xl0-5 ('C-1) no matter what molding method is used.

However, in precision fields such as high-density magnetic disks and optical disks, which have recently been attracting attention, 1O-5 (℃-I
) A circular resin plate having a smaller coefficient of linear expansion is desired.

On the other hand, polymers capable of forming anisotropic melts (hereinafter referred to as liquid crystal polymers) are described in US Pat. No. 3,778,410, US Pat. No. 3,804,805, J.

Polym, Sci, Polym, Chem, E
H, J, Jack in d, p 2043 (1976)
Since it was first reported by John et al., it has attracted attention, and since then many researchers have reported numerous studies on new compositions and physical properties.

A liquid crystal polymer has a rigid unit in one molecule, forms an anisotropic melt in a molten state, and is oriented by shearing force. l+1. J. Jackson et al. measured the linear expansion coefficient of a filament obtained by extruding a liquid crystal polymer from a nozzle and molding it, and reported that it showed a very small value of 1O-5 ('C-1). but.

This was a result of orientation in the -axis direction.

(Problem to be solved by the present invention) Then, by making a flat plate of liquid crystal polyester that is evenly oriented two-dimensionally on a plane and cutting it out into two disks, a circular resin plate with a small linear expansion in diameter can be obtained. However, it is difficult to achieve uniform orientation in two dimensions.

The inventors can apply it to the precision field. Since there is no circular resin plate that undergoes little dimensional change due to temperature, an attempt was made to obtain a circular resin plate with a linear expansion coefficient of 1O-5 ("c-1") in diameter.

(Another Means to Solve the Problem) The inventors of the present invention used a three-disk mold and injection-molded the liquid crystal polymer using the center of the mold as a gate.

The polymer molecules are oriented radially from the center of the gel.

The present invention was achieved based on the discovery that the linear expansion coefficient of the diameter is less than 1O-5 ("c-1").

That is, the present invention is a circular resin plate made of a polymer capable of forming an anisotropic melt and having a coefficient of linear expansion in diameter of less than 1O-5 ('C-1).

The circular resin plate of the present invention is obtained by injection molding a polymer capable of forming an anisotropic melt by using a circular mold and closing the center of the mold with a gate. The shape of the gate 1 is preferably circular so that the resin flows radially and uniformly. If the mold used is too thick, it will be difficult for the molecules to orient; on the other hand, if the mold is too thin, the resin will not flow easily.
to do.

Generally, a thickness of 0.2 to 8 nm is preferred. moreover.

The preferred thickness is 0.3 to 5 mm. If a resin with good fluidity is used, disks with a diameter of 30 cm or more can be obtained.

However, from the viewpoint of ease of molding, the diameter of the disc is preferably 2 to 30 cm. The temperature of the mold varies depending on the melting temperature and fluidity of the liquid crystal polymer used, but it is necessary to choose a temperature at which the resin quickly cools and solidifies so that the orientation obtained by shearing does not relax after injection. be. The shear rate applied to the resin is preferably 10'' (sec-1) or more to ensure sufficient orientation.

Any liquid crystal polymer can be used as long as it exhibits anisotropy in a molten state and can be injection molded. Specific examples of such liquid crystal polymers include 1, for example, p disclosed in Japanese Patent Publication No. 56-18016.
- A copolymer of hydroxybenzoic acid and polyethylene terephthalate, a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid disclosed in JP-A-54-77691.

Special Publication No. 59-30727 and Special Publication No. 59-307
Polyester carbonate disclosed in JP-A-54-30290 Terephthalic acid, 2,6-naphthalene dicarboxylic acid, hydroquinone and p disclosed in JP-A-54-30290
- Copolymer of hydroxybenzoic acid, JP-A-56-105
A copolymer of 6-hydroquine-2-naphthoic acid, hydroquinone and terephthalic acid disclosed in JP-A No. 26, a copolymer of phenylhydroquinone and terephthalic acid disclosed in JP-A-53-65421, and JP-A-Sho 53-65421. 57-874
Examples include a copolymer of p-hydroxybenzoic acid, terephthalic acid, resorcinol, and 6-hydroxy-2-naphthoic acid disclosed in Japanese Patent No. 23.

Among these liquid crystal polymers, because they have excellent moldability,
Japanese Patent Publication No. 56-1.8016, Japanese Patent Publication No. 54-776
Particularly preferred are the liquid crystal polymers disclosed in Japanese Patent Publication No. 91, Japanese Patent Publication No. 59-30727, and Japanese Patent Publication No. 59-3072.

Fillers such as titanium oxide, talc, alumina, and glass powder may be added to the resin plate of the present invention within a range (specifically, less than 50%) that does not reduce the coefficient of linear expansion.

The cross section of the circular resin plate of the present invention has a nine-layer structure.

From the strongly oriented layer on the surface to the weld line at the center, a strongly oriented layer 9 and a weakly oriented layer exist reinforcing each other. The relaxed orientation layer provides flexibility, and the orientation layer contributes to extremely small linear expansion. The strongly oriented layer on the surface is smooth.

(Function) The reason why the coefficient of linear expansion of the diameter of the disc of the present invention is small is as follows.
The oriented liquid crystal polymer resin has a small linear expansion coefficient in the orientation direction as well as a small nine-body expansion coefficient, and the linear expansion coefficient in the orientation direction is 1.
Although it is a small value on the order of 0-'('C-1),
It can be mentioned that it has a negative value. It is considered that the sum of i and e yields a circular resin plate with extremely small linear expansion in diameter.

(Example) The present invention will be described in more detail with reference to Examples below.

Example 1 and Comparative Example 1 A copolymer of 60 mol% p-hydroxybenzoic acid and 1.40 mol% polyethylene terephthalate with an intrinsic viscosity of 0.
65 (Measured at 30°C using a mixed solvent of tetrachloroethane and phenol in a weight ratio of 5:5 as the medium)
A liquid crystal polyester film with a diameter of 170 mm and a thickness of 1.5 mm has a circular gate with a diameter of 15 mm in the center. Injection molding was performed using a mm mold. The molding temperature was 270°C, the discharge pressure was 600 kg/ct, and the mold temperature was 35°C.

The circular resin plate obtained here is referred to as Example 1.

For comparison, glass-filled polyethylene terephthalate resin (not liquid crystal polyester) was used at a mold temperature of 130°C.
Injection molding was carried out under the same conditions as in Example 1 except that the temperature was 0.degree. C. to obtain a circular resin plate of Comparative Example 1.

Table 1 shows the molding shrinkage and linear expansion coefficient of the disc diameter of Example 1 and Comparative Example 1, and these were compared.

The coefficient of linear expansion in the diametrical direction of the disk in Example 1 is extremely small, and therefore the molding shrinkage is also small, which is far superior to the glass-filled polyester disk of Comparative Example 1, which is generally said to have a small linear expansion. I know that there is.

Table 1 Example 2 72 mol% p-hydroxybenzoic acid and 6-hydroxy-
A copolymer of 28 mol% of 2-naphthoic acid with an intrinsic viscosity of 2
．． 8 (measured in pentafluorophenol at 60°C)
A liquid crystal polyester having the following properties was injection molded using a mold having a diameter of 1.20 mm and a thickness of 1.5 mm and having a 15 mm circular gate in the center. The molding temperature was 310°C, the discharge pressure was 600 kg/cJ, and the mold temperature was 65°C. The molding shrinkage of the circular resin plate obtained here is 0/100
0. The coefficient of linear expansion showed an extremely small value of 0.5X10-5 ('C-1). In addition, the surface was smooth and glossy, and had appropriate hardness and flexibility.

Example 3 Copolymer of 33.1 mol% p-hydroxybenzoic acid, 33.5 mol% hydroquinone, 12.7 mol% isophthalic acid and 20.7 mol% carbonic acid, intrinsic viscosity 0.70
(measured at 30 °C using a mixed solvent of tetrachloroethane and phenol in a weight ratio of 5:5 as the solvent). 80mm,
Injection molding was performed using a mold with a thickness of 0.81. Molding temperature is 2
The temperature was 75°C, the discharge pressure was 400 kg/cat, and the mold temperature was 30°C. The molding shrinkage of the diameter of the circular resin plate obtained here was 1/1000. Linear expansion coefficient is approximately 0.8X
It showed an extremely small value of IO-5 ("C-1).

(Effect of the invention) By radially orienting a polymer capable of forming an anisotropic melt, the coefficient of linear expansion in diameter can be increased to 1O-5 ('C-
1) An extremely small circular resin plate was obtained. Such a low coefficient of linear expansion is a value that could not be achieved with conventional general-purpose resins.

The appearance of the circular resin plate of the present invention having extremely small linear expansion is expected to further aid the development of precision fields such as high-density magnetic disks and optical disks.

Claims (1)

[Claims] (1) A circular resin plate made of a polymer capable of forming an anisotropic melt and having a linear expansion coefficient of less than 10^-^5 (°C^-^1).