JPH02111516A - Injection mold - Google Patents

Abstract

PURPOSE:To make it possible to stably mold a product having a high quality required for an optical disc and the like and to lengthen the service life of a mold by a method wherein a thin dense ceramic film is produced by chemical vapor deposition(CVD) on at least one cavity constitutional surface of the fixed mold part and movable mold part of an injection mold. CONSTITUTION:Thin SiC films 13 and 23 are respectively produced by CVD on the surfaces of cavity constitutional parts 12 and 22, which are respectively made of reaction-sintered SiC and then respectively fixed with adhesive to a fixed mold main body 11 and a movable mold main body 21, both of which are made of special stainless steel. The surfaces of the thin films 13 and 23 are polished and, after that, lapped so as to produce a fixed mold part 10 and a movable mold part 20. A compact disc molded by said mold has very smooth surfaces. Further, no development of wear mark, scratch, haze and the like occurs on the cavity constitutional surfaces even after 4,000,000 molding shots.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an injection mold particularly suitable for molding optical discs for music equipment, office automation equipment, and the like.

(Prior Art) In recent years, one of the things that has been greatly changing the aspect of packaged information media such as various data files is the storage disc. This optical disc records information based on the presence or absence of minute pits and optically reproduces it using a single minute spot of laser light.Since it is non-contact, it has excellent durability and is capable of high-density recording. be. This optical disc is
It is popular for audio and video recording on compact discs, laser discs, etc., and enables high-precision reproduction of the original sound by recording digital signals.

Such a reproducing optical disc is manufactured as follows.

That is, first, a stamper in which microprotrusions corresponding to the recording pits are formed is manufactured, and this stamper is placed in an injection mold in which a cavity corresponding to the shape of the optical disc is formed by a fixed side mold part and a movable side mold part. Optical disks are manufactured by attaching it to the cavity forming surface and injecting and filling polymethyl methacrylate resin, polycarbonate resin, etc.

Conventionally, special stainless steel with high hardness and high thermal conductivity, such as Starbucks (trade name), has been used as a material for the mold for molding optical disks. However, for example, in the mold where the standber is attached, there is a risk that scratches may occur on the mirror-finished cavity component surface when replacing the standby, and if molding is continued in this state, the scratches will be transferred to the optical disc through the standby. This may cause problems such as. Furthermore, the mold usually wears out or becomes cloudy after 1.5 million to 2 million shots, so the mold must be re-polished before use.

As described above, re-polishing due to scratches, wear, etc. not only reduces the production efficiency of optical discs, but also increases the cost of polishing itself, contributing to an increase in manufacturing costs.

Recently, as a means to solve such problems,
It has been proposed to use a ceramic member such as a silicon carbide sintered body for at least a portion forming a cavity forming surface of an injection mold (see Japanese Patent Application Laid-Open No. 181118/1983).

For example, silicon carbide sintered bodies are about five times as hard as conventional special stainless steels, so they are less likely to get scratched, have less wear, and have a much longer lifespan, as well as excellent thermal conductivity. Therefore, it has the advantage that it is also possible to shorten the molding time per cycle.

(Problem to be Solved by the Invention) However, in ceramic members such as the silicon carbide sintered body mentioned above, minute bores are inevitably present, especially concentrated on the surface area, so such If the cavity constituting surface of an injection mold is formed using a ceramic member of the same condition, the bores etc. on the surface will be transferred to the surface of the molded optical disk, making it difficult to obtain a good product and furthermore, making it unusable as a product. Sometimes it happened.

This invention was made in order to address the problems of the conventional technology, and in particular, to achieve good quality in molding resin products that require high quality such as optical disks, and to improve the longevity of the mold itself. The purpose is to provide an injection mold that makes it possible to

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention includes a fixed side mold part and a movable side mold part disposed so as to be movable forward and backward with respect to the fixed side mold part. In an injection mold in which a cavity of a desired shape is formed when a side mold part and a movable side mold part are brought into contact with each other on a predetermined surface, the cavity forming surfaces of the fixed side mold part and the movable side mold part are It is characterized in that a ceramic thin film is formed on at least one side by chemical vapor deposition.

(Function) Ceramic thin films formed by chemical vapor deposition (hereinafter referred to as CVD) are extremely dense and have excellent adhesion to the base material. Furthermore, the CVD method allows the formation of various ceramic thin films, and the dense ceramic thin film makes it possible to extend the life of the mold and improve product quality. For example, if a highly hard SIC thin film is formed on the cavity forming surface, a good product can be obtained and the life of the mold can be extended.Also, if an A-FN thin film with excellent thermal conductivity is used, molding can be performed at high speed. By using various ceramics according to the required characteristics of the mold, various characteristics can be imparted, such as the ability to achieve .

(Example) Hereinafter, an example in which the injection mold of the present invention is applied to an optical disk mold will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of an optical disc molding mold, and this optical disc molding mold includes an injection device 1
a fixed side mold part 10 that comes into contact with the nozzle; a movable mold part 20 that is movable between the contact position with the fixed side mold part 10 and the product removal position by a drive mechanism (not shown); A cavity 40 corresponding to a predetermined optical disc shape is formed by a mold adjustment part 30 fixed to the outer periphery of the movable mold part 20.

In the stationary side mold part 10, a cavity forming part 12 is fitted into a recess 11a of a stationary side mold body 11 formed of a metal member such as special stainless steel, and a cavity is formed on the surface of this cavity forming part 12. A ceramic thin film 13 serving as a constituent surface is formed. The cavity forming portion 12 also has a through hole 12a connected to the sprue portion 14.
is formed.

Similarly, in the movable side mold part 20, a cavity forming part 22 is fitted into the four parts 21a of the movable side mold main body 21 formed of a metal member.
Ceramic thin film 2 that becomes the cavity forming surface on the surface of 2
3 is formed.

A stamper 41 is attached to the movable mold part 20 through a through hole 22a formed near the center of the cavity forming part 22.

In addition, inside the fixed side mold body 11 and the movable side mold body 21, there are refrigerant flow parts 15 and 24 for cooling after molding, respectively.
is provided.

The cavity forming portion 12.22 is formed of various materials depending on required mold characteristics.

For example, if the cavity is formed using a ceramic member, the hardness improvement effect of the ceramic thin film 13.23 can be further improved, and even if the cavity is formed using a metal member, the hardness improvement effect of the ceramic thin film 13.23 will make it possible to construct a cavity using a conventional metal member. Compared to those with a surface, the hardness is significantly improved, the service life can be extended, and the cost can be reduced.

Ceramic members used for the cavity forming portion 12.22 include SICs 813 N 4 and TIN.
It is possible to apply various ceramic sintered bodies such as 5Zr02, AβN1 AJ22N3, etc. For example, if the main purpose is to extend the life of the mold, SiC sintered bodies are suitable.
Further, if the main objective is to increase the molding speed, an AβN sintered body is suitable, and the material is selected as appropriate depending on the required characteristics. In addition, among the SiC sintered bodies mentioned above, reaction sintered SIC by injecting metal Si can be dense and almost porous, making it possible to further improve the surface quality of the ceramic thin film formed on the surface. It is. Incidentally, reaction sintered SIC generally has low strength and is not very suitable as a structural member, but its strength as an injection mold is sufficiently satisfactory.

In addition, various molding methods such as general press molding can be used to mold ceramic members. For example, slip casting is used when manufacturing large objects such as molds for laser discs. Application of law is appropriate. The use of slip casting reduces manufacturing costs and improves yield.

In addition, a ceramic thin film 13 serving as a cavity forming surface.
23 is formed by a CVD method, and various CVD methods such as normal pressure CVD, low pressure CVD, and plasma CVD can be used. Moreover, the material used is SiC.

Si3N4, TiN, ZrO2, AJ2N
Various materials such as S Anz03 can be used and are selected appropriately according to the required characteristics. For example, if the material of the cavity forming part 12.22 is a ceramic member, it may be the same material as this, or a different material may be used. It is also possible to use

For example, SIC is suitable for achieving a long life of the mold, AJ2N is suitable for achieving a high molding speed, and 813N4 is suitable for further improving surface smoothness, that is, product quality.

The thickness of this ceramic thin film is suitably from several .mu.l to several 100 .mu.l, preferably 50 .mu.m or more.

For example, when a ceramic member is used as the cavity component 12.22, a bore is often present on the surface of the ceramic member, and in this state, the ceramic thin film 13
．． This is because if the thickness of the ceramic thin film 13.23 is too thin, there is a high risk that the unevenness on the surface of the cavity forming portion 12.22 will be transferred to the surface of the ceramic thin film 13.23. Note that this is not the case when using the Si-impregnated SIC sintered body as described above.

In addition, when the thickness of the ceramic thin film 13.23 is increased to, for example, 50 μm or more, ・2
A layered structure is preferred. In other words, the thin film lower layer from the surface of the cavity forming part 12.22 to a thickness of about 30 μm serves as a layer for absorbing the unevenness of the surface of the cavity forming part 12.22, and in order to sufficiently have this effect, the thin film lower layer has a theoretical density, for example. It is preferable to set it as a layer of 95% or less.

If the density of this thin film lower layer is brought too close to the theoretical density, the effect of absorbing the unevenness on the surface of the cavity forming portion 12.22 will be reduced. Specifically, this can be achieved by increasing the formation rate of the thin film, for example by increasing the amount of raw material gas introduced from several β/min to several tens of degrees C/min, although this varies depending on the material of the ceramic thin film to be formed.

In addition, by increasing the formation rate of the thin film lower layer in this way, the overall formation rate can be increased, leading to cost reduction.

Then, on the top of this thin film lower layer, a thickness of 5 μl to 30 μm is applied.
Form a thin upper layer of approximately Since this thin film upper layer actually becomes the cavity constituting surface, it needs to be sufficiently dense, and the conditions during formation are controlled so that it has approximately the theoretical density. For example, the purity of the raw material gas may be increased, the amount of raw material gas introduced may be set to about several liters/min to several 12/min, or the reaction temperature may be optimized. This thin film upper layer is finally given a mirror finish such as lapping to become the cavity forming surface.

The lower thin film layer and the upper thin film layer may be formed of the same material, or may be formed of different materials.

Next, a mold for molding a compact disc was fabricated based on the configuration specifically shown in FIG. 1, and the results of evaluating various characteristics will be described.

Example 1 First, a binder was added to a mixed powder of SiC powder and carbon black (3 parts of Sac powder, 20% by weight of black,
6% by weight of phenolic resin, 18% by weight of furan resin, and 17% by weight of furfural), and after thorough mixing, a molded body is formed by press molding to correspond to the shapes of the cavity components 12 and 22 on the fixed side and the movable side. Created.

Next, these molded bodies were housed in a graphite holder, metal 81 was placed nearby, and the molded bodies were heated to 1450'c x
Silicification treatment was performed by heat treatment under the conditions of ao.

Next, these were immersed in molten Si to impregnate Si to obtain reactive sintered SiC.

Thereafter, rough machining was performed to give shapes, resulting in the cavity forming parts 12 and 22 having predetermined shapes, respectively. When the surface portions of these cavity components 12 and 22 were observed using a TEM, they were found to be dense with no visible bores.

Next, a SIC thin film was formed on the surfaces of the cavity components 12 and 22 made of these reaction-sintered SICs by CVD according to the following procedure.

First, the surfaces of these cavity constituent parts 12 and 22 are HC-treated.
After purification treatment with n gas, set it in a reaction container and SiC
Using β4 gas and CH4 gas as raw material gas, 5ic
J24 + CH4 → SIC + 4) A SIC thin film was formed according to the reaction of 1cJ2. The conditions at the time of formation were a container internal pressure of 0. Iatm, raw material gas introduction rate 5β/min,
Assuming a base material temperature of 400°C and a film formation rate of 0.1 μm/sec,
The film thickness was ioμl.

The obtained ceramic thin films 13 and 23 made of SjC have a density of 94% of the theoretical density, are uniformly grown crystals, and are extremely thin with only a few μl of pores scattered on the surface. It was a good thin film.

Next, the cavity components 12 and 22 with the ceramic thin films 13 and 23 formed thereon are placed between the fixed mold body 11 and the movable mold body made of special stainless steel with recesses into which they can fit. The ceramic thin films 13 and 2 are fixed to the mold body 21 with adhesive, respectively.
After polishing the surface of No. 3, a lapping process was performed to produce a fixed side mold section 10 and a movable side mold section 20.

Then, the body mold part 30, which was also made of special stainless steel, was fixed at a predetermined position of the movable side mold part 20, thereby obtaining a mold for injection molding.

Comparative Example 1 An injection mold having the same structure as that of Example 1 was manufactured using only special stainless steel.

Comparative Example 2 In Example 1, the cavity structure parts 12 and 22 were formed by normal press molding and pressureless sintering.
The fixed side mold part 10 and the movable side mold part 2 are formed by C sintered body and without forming a ceramic thin film on the surface.
A mold for injection molding was similarly obtained.

Using the injection molds of Example 1 and Comparative Example 1.2, each was installed in an injection molding machine with a mold clamping pressure of 60 tonf', and polycarbonate resin (grade for compact discs) was used, the resin temperature was 300°C, and injection molding was performed. pressure 1
A compact disc was molded under the conditions of 00100O/c7.

The mold of Comparative Example 1 showed wear on the cavity forming surface after about 1.5 million shots, and also had small scratches. On the other hand, the molds of Example 1 and Comparative Example 2 had a
Although no wear marks, scratches, cloudiness, etc. were observed on the cavity structure surface even after several shots, the surface of the compact disc molded with the mold of Comparative Example 2 had minute irregularities. Ta. In contrast, the surface of the compact disc molded using the mold of Example 1 was extremely smooth and excellent. In addition, the mold of Example 1 is the same as that of Comparative Example 1.
The molding cycle was able to be shortened by about 10% compared to the previous mold.

Example 2 First, 2% by weight of B and C as sintering aids and 5% by weight of phenol resin as a binder were added to SiC powder and mixed in a jar, and then granulated with a spray dryer to form the granulated powder. A molded body corresponding to the shapes of the cavity constituent parts 12 and 22 on the fixed side and the movable side was produced by press molding.

Next, these molded bodies were degreased in a nitrogen gas atmosphere and then fired at 2100°C to 2200°C to produce a SiC sintered body.

Next, these SIC sintered bodies were rough-processed to give them a shape to form the cavity forming part 12.22, and 5ick 4 gas and C114 gas were used as raw material gases on these surfaces as in Example 1. A two-layer fM SIG thin film was formed according to the following procedure.

First, the pressure inside the container is 0.1 atm, and the amount of raw material gas introduced is 5.
0f/min, base material temperature 400”C2 film formation rate 0.1μ
m/sec, a thin film lower layer having a film thickness of 50 μm was formed.

The density of this thin film lower layer was 94% of the theoretical density.

Next, the conditions were changed to raw material gas introduction m5J2/min, base material temperature 400 DEG C., and film formation rate 0.01 .mu.-7 seconds to form a thin upper layer of 20 .mu.l of film J. The density of this thin film upper layer was 99% or more of the theoretical density.

The resulting two-layer ceramic thin films 13 and 23 made of SiC had uniform crystal growth, and were extremely good thin films with only a few micrometer-sized bores scattered on the surface.

Thereafter, in the same manner as in Example 1, the ceramic thin film 13, 23 is applied to the fixed mold body 11 and the movable mold body 21.
The cavity forming part 12.22 in which was formed was fixed, and the surface of the ceramic thin film 13.23 was polished and lapped to prepare an injection mold.

Example 3 First, 3% by weight of Y2O3 as a sintering aid and 7% by weight of paraffin as a binder were added and mixed to AJ2N powder, and then press molding was performed to form the fixed side and movable side cavity components 12. No. 22 molded bodies corresponding to each shape were produced.

Next, these molded bodies were degreased in a nitrogen gas atmosphere, and then fired at 1700'c to 11150'c to produce AβN sintered bodies.

Next, these AJ2N sintered bodies were rough-processed to give them a shape to form a cavity forming part 12.22, and a two-layer ceramic thin film 13.23 made of SiC was applied to the surface of these under the same conditions as in Example 2. was formed, and then an injection mold was produced in the same manner.

Example 4 A1C was applied as a raw material gas to the surface of the cavity component 12.22 made of an AβN sintered body obtained in the same manner as in Example 3.
Using f23 gas, N2 gas and 112 gas, AJ! C13+1/2N2 +3/2)+2 →A
Using the reaction of nN +3HCJ2, a two-layered AJ2N thin film was formed according to the following procedure.

First, the inside of the container was set to 0.1ate with a mixed gas of nitrogen + hydrogen, the raw material gas was introduced at 140f2/min, and the base material temperature was 400f2/min.
℃, film formation rate 0.1 μII/sec, film thickness 40μ
A thin lower layer of Maro was formed. The density of this thin film lower layer was 94% of the theoretical density. Next, the conditions were as follows: raw material gas introduction amount: 4 (7 minutes, base material temperature: 400°C, film formation rate: 0.01 μm)
/second, and a thin upper layer with a thickness of 20 μl was formed. The density of this thin film upper layer was higher than the theoretical density of 9926.

Thereafter, an injection mold was produced in the same manner as in Example 2.

Example 5 First, 5% by weight of 84C as a sintering aid was added and mixed with SiC powder, and 1 part by weight of polycarboxylic acid as a dispersant and 2 parts by weight of polyacrylic resin as a binder were added to 100 parts by weight of this mixed powder. After adding parts by weight and 50 parts by weight of water, pulverizing and mixing in an alumina pot for 24 hours, defoaming treatment was performed in a vacuum to prepare a slurry.

Next, this slurry is poured into a plaster mold having recesses corresponding to the shapes of the cavity components 12 and 22, and after a predetermined period of time, it is taken out from the right mold and left at room temperature for 2 hours.
Each molded article was produced by drying for 4 hours.

Next, these molded bodies were degreased in a nitrogen gas atmosphere, and then fired at 1700° C. to 1950° C. to produce an SIC sintered body, and rough processing was performed to give dimensions to form the cavity component part 12.22. .

Next, a cavity component 1 made of these SIC sintered bodies is prepared.
A two-layered ceramic thin film 13.23 made of 910 was formed on the surface of the sample 2.22 under the same conditions as in Example 2, and then an injection mold was produced in the same manner as in Example 2.

Using this slip casting method, the cavity forming part 1 is
The injection mold manufactured by No. 2.22 has a very high yield compared to the mold in which the cavity structure portion 12.22 was formed by press molding, and the yield was about 100% compared to the mold of Comparative Example 1. It could be formed at a cost of 70% to 85%.

Example 6 The fixed side mold body 11 and the cavity structure part 12 in Example 1 were integrally molded with special stainless steel to form the fixed side mold part 10, and the movable side mold body 21 and the cavity structure part 22 were similarly molded. The movable side mold part 20 was formed by integral molding.

Next, SiC was applied to the cavity forming surfaces of the fixed side mold part 10 and the movable side mold part 20, respectively, in the same manner as in Example 2.
A ceramic thin film 13.23 having a two-layer structure was formed, and the surface of the ceramic thin film 13.23 was polished and lapped to prepare an injection mold.

Example 7 A two-layer ceramic thin film 13, 23 made of AJ2N was applied to the cavity forming surfaces of the stationary side mold part 10 and the movable side mold part 20, which were produced in the same manner as in Example 6, respectively, in the same manner as in Example 4. A mold for injection molding was produced in the same manner as in Example 6.

Example 8 51(
Using Nl12) 4 gas, 331(NO3) 4→
A 513N4 thin film having a two-layer structure was formed using the reaction of 3Si3N 4 + 8NHt according to the following procedure.

First, the inside of the container was set to o, tac+++ with nitrogen gas, and a thin film bottom layer with a film thickness of 50 μm was formed under the following conditions: raw material gas was introduced at 14 OA/min, base material temperature was 400° C., and film formation rate was 0.1 μl/sec. The density of the lower layer of this thin film was 95% of the theoretical density.Next, the conditions were changed to raw material ° gas introduction amount 4
J2/min, base material temperature 400℃, film formation rate 0,0181
The heating time was changed to 17 seconds, and a thin upper layer having a thickness of 20 μm was formed. The density of this thin film upper layer was 99% or more of the theoretical density.

Thereafter, an injection mold was produced in the same manner as in Example 6.

The injection molds of Examples 2 to 8 were each installed in an injection molding machine with a mold clamping pressure of 80 tons, and polycarbonate resin (blades for compact discs) was used at a resin temperature of 300°C and an injection pressure of 10,010 tons.
A compact disc was molded under conditions of 0O/cd.

Each injection mold and the obtained compact disc were evaluated according to the following items.

The results are shown in Table 1.

■ Continuous moldability.

■ Quality of the resulting compact disc.

■ Molding time per batch.

(Left below) As is clear from the results in Table 1, each material can withstand more than 4 million shots, has a long service life, and has good product quality. The characteristics can be further improved depending on the characteristics of each material and the material of the cavity constituent parts. In other words, it can be seen that injection molds having various properties can be obtained by using materials that meet the required properties.

In the above embodiment, a ceramic thin film is formed on the cavity forming surface of each of the fixed side mold part and the movable side mold part, but even if only one of them is formed, effects corresponding to each can be obtained.

[Effects of the Invention] As explained above, according to the injection mold of the present invention, products with high required quality such as optical disks can be stably molded, and the mold itself has excellent durability and has a long life. This makes it possible to reduce manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of an injection mold according to an embodiment of the present invention. 10...Fixed side mold part 11...Fixed side mold body 12.22...
・Cavity forming part 13.23...Ceramic thin film 20...Movable side mold part 21...Movable side mold body 30...
...Body side mold part 40...Cavity Applicant: Toshiba Corporation

Claims (1)

[Claims] (1) Comprising a fixed side mold part and a movable side mold part arranged to be able to move forward and backward with respect to the fixed side mold part, and the fixed side mold part and the movable side mold part are brought into contact on a predetermined surface. In an injection mold that forms a cavity of a desired shape when the mold is pressed, a ceramic thin film is formed by chemical vapor deposition on at least one of the cavity forming surfaces of the fixed side mold part and the movable side mold part. An injection mold featuring: