JPH05220751A - Manufacture of mold for molding plastic - Google Patents

Abstract

PURPOSE:To manufacture a mold for molding plastics which can reduce manufacturing processes, and has good mechanical strength and durability, and also has an enhanced configurational accuracy. CONSTITUTION:In a manufacture of a mold for molding plastics in which a fine pattern of 5mum or less in its wire breadth and 10-800nm in its depth is formed by forming a desired resist patterns on a base material having an optical face accuracy, and thereafter effecting etching of the parent material 21, and next removing the resist 22 therefrom, crystal or amorphous silicon or quartz is used as a base material 21, and dry etching is employed as etching herein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mass-produces optical information recording bodies (video discs, optical memory discs, digital audio discs) and plastic optical products having fine patterns such as phase type Fresnel zone plate lenses. The present invention relates to a method of manufacturing a molding mold for molding.

[0002]

2. Description of the Related Art Optical products such as optical video discs, optical memory discs, digital audio discs, phase-type Fresnel zone plate lenses, etc.
m or less, for example, 0.4 to 5 μm and a depth of 10 nm to 800 nm) are engraved. Therefore, in order to mass-produce optical products having such a fine pattern with plastics, it is necessary to prepare a mold or a mold having the same level of the fine pattern.

Conventionally, a mold or a mold having such a fine pattern has been manufactured by the process shown in FIG. That is, first, in order to obtain a reference surface having optical surface accuracy, the glass substrate 1 is ground and polished until optical surface accuracy is obtained, and then a photoresist is applied to expose and develop a desired pattern to obtain a desired register. Pattern 2 is formed. Nickel plating is applied thereon by a method called electroforming, the obtained plated layer 3 (called a metal master) is peeled from the glass base material, and the metal master 3 is fixed to a metal pedestal B to form a mold. Although it is good, the metal master 3 is not durable, so in general, using the metal master 3 as a master, an inversion type nickel mother 4 is made by an electroforming method, and based on this mother 4, an electroforming method is again used as an inversion type nickel mother. A large number of nickel stampers 5 (same type as the metal master) are made, and these stampers 5 are fixed to the metal pedestal B to form a molding die.

[0004]

Therefore, in the conventional mold, (a) the master is changed to the mother and the mother is changed to the stamper, so that the fine pattern collapses each time the transfer is performed. The average number of masters that can be made from a mother and one mother to make a stamper is several, and among these several, there are variations in pattern accuracy. (B) There are many manufacturing processes and it takes a long time to manufacture. In short, (c) dust adhesion is a problem for fine patterns, so an electroforming device with less contamination of the bath is required, and advanced bath management is also required. (D) Metal master, mother Both stampers and stampers are at most a few mm
Because it is thin, it deforms when peeled after electroforming,
(E) After peeling, it is necessary to correct the uneven thickness when fixing it to the pedestal. (F) When fixing it to the pedestal, the stamper is thin, so considerable work is required and dust is not inserted. You have to be careful,
(G) The nickel stamper has a drawback that it is not durable and that when several thousand sheets are molded, the precision is lowered and it cannot be used.

The object of the present invention is to eliminate these drawbacks,
In particular, it is to provide a method for manufacturing a plastic molding mold that has excellent durability and has few manufacturing steps.

[0006]

Therefore, the inventors of the present invention aimed to directly manufacture a mold, and first studied the necessary mold material. As a result, three types of glass, silicon and quartz were selected as materials having durability and capable of finishing the surface into a flat or curved surface having optical surface accuracy. Next, a photo-etching technique was selected as a method for marking a fine pattern on these base materials. There are two types of etching, wet type and dry type, but since wet type is isotropic etching, there is a dimensional shift from the resist pattern, and dimensional accuracy in the reference plane direction cannot be obtained. The shape of the groove should not be rectangular,
Therefore, it was found that the directional dry method had to be adopted to etch a desired fine pattern.

However, among the above-mentioned three kinds of materials selected, glass (a) has a low dry etching rate,
Know that it is not suitable because the resist pattern is etched and disappears before it is etched to the desired depth, so deep etching cannot be performed, and (b) the mechanical strength is not sufficient as a mold. It was Therefore,
According to the present invention, "a desired resist pattern is formed on the surface of a base material having optical surface accuracy, the base material is etched, and then the resist is removed to obtain a line width of 5 μm or less and a depth of 10 nm to In the method for manufacturing a plastic molding mold in which a fine pattern of 800 nm is formed, crystalline or amorphous silicon or quartz is used as the base material, and dry etching is adopted as the etching. "How to do".

The manufacturing process of the mold of the present invention will be described below with reference to FIG. The base material 21 is selected from four types of silicon single crystal, amorphous silicon, quartz and fused silica. Silicon has a higher etching rate than quartz, and as a result,
There is a feature that a deep groove can be dug. Then, at least one surface of the base material 21 is finished into a flat surface or a curved surface (spherical surface, aspherical surface) having optical surface accuracy. The optical surface accuracy can be obtained relatively easily by the precision grinding and polishing techniques used in the technical field of optical products, particularly lenses and prisms.

Photoresist is uniformly applied to the high precision surface thus obtained. As the photoresist, for example, a negative type such as OMR manufactured by Tokyo Ohka Kogyo Co., Ltd. or a positive type such as AZ1350 and AZ1350J manufactured by Shipley Co. or OFPR manufactured by Tokyo Ohka Kogyo Co., Ltd. is used. Then, depending on the type of photoresist used, exposure is performed using a mask having a desired pattern or a mask having a reverse pattern to the desired pattern. In addition, pattern exposure can be performed in the same manner by drawing a diagram while irradiating a thin laser beam without using a mask. This method is used for video discs.

After exposure and development, depending on the type of resist, the exposed portion is cured and remains, or is dissolved in a developing solution and flows out to form a resist pattern 22. Next, the base material on which the resist pattern 22 is formed is dry-etched. Examples of the dry etching method include a cylindrical dry etching method, a parallel plate dry etching method, and an ion beam etching method.

After the dry etching is completed, the resist pattern 22 is dissolved in a solvent and removed, or burned in O ₂ plasma. Finally, washing and drying are performed to obtain the mold of the present invention. The mold thus obtained is used for optical products such as optical video discs, optical memory discs, digital audio discs, phase-type Fresnel zone plate lenses, PMMA, PVC, polycarbonate,
It is used for injection molding and press molding of plastics such as polystyrene and CR-39 polymer, and for molding by casting polymerization molding, ultraviolet curing molding and the like from monomers or oligomers that give these plastics.

The present invention will be specifically described below with reference to examples.

[0013]

EXAMPLE In this example, a mold for injection molding a concentric phase-type Fresnel zone plate lens as shown in FIGS. 3 and 4 with an acrylic resin is manufactured. The specifications and dimensions of this lens are as follows. Outer dimension (1) is 20 mm, thickness (t ₀ ) is 1 mm, effective aperture (2rω) is 4 mm, focal length (f) is 30 mm, and the diameter of the central zone (Z) (2r ₁ ) is
0.3 mm, the outermost zone (Z) width is 5 μm, the total number of zones (Z) is 125, and the depth (t ₁ ) of the zone (Z) is
The aperture ratio (2r _n : r _{n + 1} ) of the 8000Å (800 nm), nth and n + 1th zones is √n: √ (n + 1).

Next, the mold manufacturing process will be described. (1) First, prepare a silicon single crystal plate with a side of 2 cm and a thickness of 2 mm, and polish the upper surface with an abrasive material Granzox manufactured by Fujimi Abrasives Co., Ltd. It was (2) A negative resist: AZ1350J manufactured by Shipley Co. was applied on the finished surface so that the dry film thickness was 1.5 μm, and dried.

(3) Next, a mask having a pattern of concentric Fresnel zones with a size of 5 times was prepared, and 1/5 reduction projection exposure was carried out by a high pressure mercury lamp through this mask. (4) When the resist layer was washed with a developer made by Shipley Co., Ltd .: AZ developer, the resist in the exposed portion was eluted, and the resist having a concentric Fresnel zone pattern was left behind.

(5) A silicon plate having a resist pattern is placed in a high frequency sputter etching device DEM451 manufactured by Nichiden Anelva Co., Ltd., and etching is performed for about 10 minutes under the condition of CF ₄ : 0.3 Torr and high frequency current input 150W. , The exposed silicon plate was scraped off to a depth of 8000Å (800 nm). (6) Finally, the resist remaining on the silicon plate was dissolved and removed with acetone and dried to obtain the template of the present invention.

The obtained mold was attached to a pedestal of an injection molding die, and the lens shown in FIG. 3 was injection-molded using an acrylic resin, whereby a molded product faithful to the mold was obtained. 5 molds
Even after molding ten thousand sheets, it was still durable enough to use.

[0018]

As described above, according to the present invention, since the master plate can be directly used as a molding mold, the manufacturing process is shortened, the troublesome electroforming process is unnecessary, and the transfer is not repeated, so that the precision is high. The mold of
Durability is significantly improved compared to stampers. as a result,
The cost of manufacturing the mold is significantly reduced.

Besides, since the thermal expansion is smaller than that of the metal mold, the molded product can be easily released from the mold, the molding precision is high, and the thermal conductivity is low, so that there is no rapid cooling, and therefore a high-quality molded product without internal distortion. Is obtained. Further, by adopting dry etching, a mold having high pattern shape accuracy, particularly in the depth direction, can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a mold manufacturing process of the present invention.

FIG. 2 is an explanatory view of a conventional mold manufacturing process.

FIG. 3 is a perspective view of a plastic phase-type Fresnel zone plate lens molded by a mold according to an embodiment of the present invention.

4 is a partially enlarged cross-sectional view of a cross section obtained by cutting along a plane taken along the line XY in FIG.

[Explanation of symbols]

 21 Base material 22 Resist B base

Claims (1)

[Claims] 1. A line width of 5 μm or less and a depth of 10 nm to 800 by forming a desired resist pattern on the surface of a base material having optical surface accuracy, etching the base material, and then removing the resist. In the method for producing a plastic molding mold in which a fine pattern of nm is formed, crystalline or amorphous silicon or quartz is used as the base material, and dry etching is adopted as the etching. Method.