JPH0525659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold for injection molding, and particularly to a mold heated by a high-frequency induction heating method.

[Conventional technology]

Conventionally, injection molding is performed by heating a mold using a high-frequency induction heating method, as described in Japanese Patent Laid-Open No. 50-45039. Equipped with an oscillator and a cooling water pump, the mold is instantaneously heated by an oscillating electrode installed inside the mold when filling with resin, the oscillation is stopped after resin filling is completed, and cooling water is pumped into the mold by the cooling water pump. A method has been proposed in which the resin is poured into a cooling channel inside the mold to cool the mold and solidify the resin.

Furthermore, Japanese Patent Application Laid-open No. 58-40504 discloses that when injection molding a thermoplastic resin, the surface of the mold in contact with the injection molded product is heated in advance to a temperature higher than the thermal deformation temperature of the thermoplastic resin using a high-frequency induction heating method. A method of injection molding has been proposed.

Molds for injection molding using this high-frequency induction heating method include rolled steel (SS), carbon steel for mechanical structures (SS, SCK), tool steel (SK, SKS), high-speed steel (SNC), and chrome steel. Steel materials such as molybdenum steel are cast, rolled, or heat treated, and then
Those formed by cutting and finishing assembly are used.

In particular, the above-mentioned iron-based mold material is suitable for the above-mentioned high-frequency induction heating mold.

[Problem to be solved by the invention]

Optical components, such as lenses and Fresnel lenses, are required to have extremely high precision in surface finishing and shape precision in lens curvature. In the case of lenses, the molten resin injected into the mold cavity is
After injection, the mold cools and solidifies.
This forms the lens shape, but if the cooling temperature of the mold is not properly controlled at this time, sink marks will occur on the lens surface and the main lens curvature shape of the lens will not be as desired.

In the case of the Fresnel lens shown in Figure 2, if the temperature of the mold is not properly controlled, the apex
The sharp corner of the 100 Å tip cannot be formed as desired.

When the mold is heated by high-frequency induction heating, the mold can be heated to a high temperature in a short time. Heating can be performed efficiently if the above-mentioned iron-based metal material is used as the mold material.

However, iron-based metal materials, especially steel-based materials that are frequently used these days, have difficulty in machinability. In other words, since it is a super hard material, it is necessary to create a curved surface by cutting the cavity surface while maintaining a high-precision surface roughness, or to process a Fresnel shape on the cavity surface, especially in the case of a Fresnel lens. It is difficult to form uneven parts.

In order to form fine irregularities on the cavity surface, a mold material with good workability is preferable, and copper-based or aluminum-based materials are suitable, but since these materials are non-magnetic and have low electrical resistance, gold is preferred. The aforementioned high-frequency induction heating method cannot be used for mold heating. Furthermore, defects such as pinholes are likely to occur during mirror finishing, making it unsuitable as a mold material.

The present invention is capable of cutting a finely uneven shape on the cavity surface, and also enables heating operation using a high-frequency induction heating method that allows the molten resin injected into the cavity to be easily injected into the finely uneven parts of the cavity. The purpose is to provide molds.

In addition, in order to mold optical components such as lenses and Fresnel lenses that require extremely high precision in surface roughness, we improve the mirror finishing precision of the mold surface and provide molds with almost no defects such as pinholes. The purpose is to

[Means to solve the problem]

As a result of intensive studies to solve the above problems, the present inventors found that an electroformed nickel layer and an electroformed copper layer are formed on a ferrous metal base material in an injection mold heated by a high-frequency induction heating method. It has been found that the above object can be achieved by sequentially laminating the electroformed copper layers, cutting the electroformed copper layers, and then laminating a chrome plating layer or a titanium compound layer on the processed surface.

In other words, by using iron-based mold material as the base material of the mold, it can be heated efficiently by high-frequency heating, and since the copper layer is formed by electroforming, there are almost no defects such as pinholes, and cutting processing is possible. Due to its excellent properties, it is possible to achieve a high degree of mirror finishing. Furthermore,
By providing a nickel layer between the base iron metal material and the copper layer by electroforming, the adhesion between the iron metal and the copper layer is improved, making it difficult to peel off during machining or thermal shock. is completely prevented.

In addition, since the copper layer has low surface hardness and modulus of elasticity and is easily scratched and deformed, by laminating a chrome plating layer or a titanium compound layer such as titanium nitride on the surface of the cut copper layer, fine particles can be created. It becomes possible to obtain a mold surface that is resistant to scratches and deformation while maintaining unevenness or specularity.

The electroformed nickel layer formed on the surface of the base material has a thickness of 5 to
The copper layers may be laminated to a thickness of about 100 μm, and the copper layer is preferably formed to have a thickness of about 50 to 200 μm. At this time, when the nickel layer or copper layer is thickly formed, it is preferable to perform thermal annealing at 200 to 350°C to relieve stress during film formation.

Further, the chrome plating layer laminated after the copper layer is cut is preferably formed to have a thickness of 1 to 20 μm. The titanium compound layer is 0.1~3μ by vapor deposition method.
Preferably, the layers are laminated to a thickness of m.

As the titanium compound, those having extremely high hardness such as titanium nitride and titanium carbide can be used.

〔Example〕

The present invention will be specifically explained below using Examples.

Example 1 As shown in FIG. 3, SKD61 steel is used as the base material 11, and machined by cutting, grinding, etc. Next, as shown in FIG. 4, a nickel layer with a thickness of 20 μm is applied on the base material 11 by electroforming.
Furthermore, a copper layer 21 with a thickness of 100 μm is formed on the nickel layer 51 by electroforming. After this, thermal annealing is performed at 250°C.

Next, as shown in FIG. 5, the outer diameter of the three-layer mold was finished, a hole for a mirror lens core was drilled in the center of the mold, and a dummy core 61 was inserted into the hole.

In the step shown in FIG. 6, the copper layer 21 is cut into a mirror surface for a Fresnel lens using a diamond cutting tool. By cutting the dummy core at the same time, the clearance will be improved when the mirror core 62 is finally fitted.

Next, as shown in FIG. 7, the dummy core 61 is removed, and the mirror-polished core 6 made of nickel emerging steel is
2 was inserted and fitted, and the whole was plated with 1 μm thick chrome plating.

The specularity (surface roughness) of the mold thus obtained was 0.01 μm, and the heating rate by high frequency induction heating was 20° C./sec.

Example 2 Using S55C steel as the base material, the nickel layer and copper layer were respectively 10 μm and 200 μm in the same manner as in Example 1.
It was formed to have a thickness of m. After mirror-finishing this as shown in FIG. 8, a titanium nitride film was formed to a thickness of 0.5 μm by vacuum evaporation.

The specularity of the mold thus obtained is 0.01μ
m, and the heating rate was 20°C/sec.

Comparative Example 1 A mold was manufactured using S45C (carbon steel). Although the mold showed a heating rate of 22°C/sec, mirror finishing could not be performed.

Comparative Example 2 A mold was produced using phosphor bronze. When mirror finishing was performed in the same manner as in the example, a mirror finish of 0.01 μm was obtained, but the heating rate by the high frequency induction heating method was 3°C/sec, and when a Fresnel lens was injection molded using this mold, there was no shrinkage. There has occurred.

[Effects of the Invention] As explained above, after laminating an electroformed nickel layer and an electroformed copper layer on a ferrous metal base material and cutting them,
By laminating a chrome plating or titanium compound layer on the surface, it is possible to provide a mold with excellent heating characteristics during high-frequency induction heating, as well as excellent specularity and mechanical and thermal strength. Summer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold showing an example of the present invention, FIG. 2 is a perspective view thereof, and FIGS. 3 to 7 are schematic sectional views showing an example of the manufacturing process of the mold of the present invention. FIG. 8 is a sectional view of a mold according to another embodiment of the present invention. 1...Base material, 2...Copper layer, 3...Hard film layer, 4
... Fresnel lens surface, 5 ... Nickel layer, 6 ...
...Mirror core, 7...Aspherical lens surface.

Claims (1)

[Claims] 1. In an injection mold heated by a high-frequency induction heating method, an electroformed nickel layer and an electroformed copper layer are sequentially laminated on a ferrous metal base material, and then the electroformed copper layer is subjected to a cutting process, A high-frequency heating mold characterized in that a chrome plating layer or a titanium compound layer is then laminated on the processed surface.