JPS61258713A - Surface treatment of metal mold for resin molding - Google Patents

Abstract

PURPOSE:To keep excellent dimensional and shape accuracy for a long time and to obtain excellent abrasion resistance, corrosion resistance and mold- releasing property, by coating the surface of a resin mold, pretreated with necessary treatments such as cavity and runner, with hard carbon. CONSTITUTION:A hard carbon film 2 is either directly formed on the surface of the metal mold 1 or polymerized on the hardened film 3 of another material formed on the surface of the metal mold 1. To form the hard carbon film 2, the high frequency spattering method where pure carbon or high purity graphite as a target is sputtered in hydrogen atmosphere or a vaporized aromatic compound atmosphere represented by benzene or the method of forming hard carbon film on the substrate by using methane (CH4) or acetylene (C2H2) plasma is applied. Plating, melt spraying, ion-plating, high frequency spattering or any other method can be used as the method for forming the hardened film 3 as the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for surface treatment of resin molding molds.

(Prior art and its problems) In recent years, engineering plastics have been widely used in the machinery industry and even household goods.
i02. Composites of fine fibers such as SiC have strength comparable to metal materials, and are therefore becoming important as industrial materials.

No matter which molding method is used, a mold is essential to mold resin, including composite materials, into the desired product shape, but molds generally require a lot of effort and time to manufacture. This is especially true when the molded shape is complex or high dimensional accuracy is required, which increases the cost of the mold.

Therefore, in order to economically mass-produce resin molded products, it is extremely important from an industrial perspective to improve the durability of the mold and the lifespan of the mold.

As a measure to improve mold life, there is a limit to just selecting the mold material, so conventionally, die steel such as 5KD-3 is processed with mold faces, and after being subjected to prescribed heat treatment, A method of applying chrome plating was used.

However, with this surface treatment method, it is difficult to maintain good molded dimensions over a long period of time, and sufficient effects on wear resistance and mold release properties have not been achieved.

In addition, in recent years, the ion plating method, ie.

By melting titanium metal, evaporating it with an electron gun, and discharging it in a nitrogen or methane atmosphere, TiN or Ti can be applied to the object.
A method for coating thin films of C has been developed. However, even with this method, when a composite material as described above is molded under severe molding conditions, the abrasion resistance of the mold tends to be insufficient, and the actual performance is still poor.

(Means for Solving the Problem) The present invention was devised through repeated research in view of the above-mentioned circumstances, and it is possible to apply a hard carbon film on the surface of a resin molding die, especially a diamond-like or carbon film with a Hv of 1,800 to 4,000. When coated with a carbon film similar to the above, it was found that the mold surface accuracy was maintained well, and the mold life was greatly extended by exhibiting an extremely excellent effect on improving wear resistance and mold releasability.

That is, the basic feature of the present invention is that the surface of a resin mold that has undergone necessary processing such as cavities and runners is coated with a hard carbon film.

The carbon film may be applied alone to the mold surface, or a hard film of another material may be applied to the mold surface as a base, and the hard carbon film may be polymerized on top of this hard film. good.

(Example) To explain the present invention in detail below, FIGS. 1 and 2 schematically show a mold for resin molding obtained by the present invention, 1 is a mold for resin molding, The resin to be molded also includes composite materials to which fine fibers and powders of inorganic and metallic materials are added. The molding method used for the mold 1 is arbitrary, such as injection molding, compression molding, transfer molding, extrusion molding, vacuum molding, blow molding, etc., and the mold structure is not limited.

A hard carbon film 2 is formed directly on the surface of the mold 1 in the embodiment shown in FIG. In the embodiment shown in FIG. 2, a hard coating 3 made of another material is formed on the surface of the mold 1, and a hard carbon coating 2 is polymerized on this hard coating 3. The method shown in Figure 1 is.

It is suitable for molds for small products, and the method shown in FIG. 2 is suitable for molds for large products. The hard carbon film 2 is
It may be applied to the entire surface of the mold 1, or it may be applied only to a required area.

Methods for applying the hard carbon film 2 include a solid method and a gas method. An example of the former is a method in which pure carbon or high-purity graphite is used as a target and high-frequency sputtering is performed on the target in a hydrogen atmosphere or an atmosphere in which an aromatic compound such as benzene is vaporized.

As the latter method, there is a method of forming a hard carbon film on a substrate using plasima such as methane (C) (, ), C,82, or the like.

A method for applying the hard coating 3 as a base may be any method such as a plating method, a thermal spraying method, an ion plating method, and a high frequency sputtering method. The substances constituting the hard coating are Cr, Ti
N, TiC, S iC, WC.

Metals, ceramics such as Zro, B a C, Y2O.

Alternatively, it is appropriately selected from one or more of these composite substances.

Next, specific examples of the present invention will be shown.

Example 1 Polycarbonate resin screw mold (material SCM-4
) After performing the necessary mold processing, the entire mold was coated with a diamond-like carbon film by high-frequency sputtering.

The coating conditions were as follows: high-purity graphite with a diameter of 100 mm was used as the target, the substrate temperature was 200°C, the target voltage was IKv, the distance between the substrate and the target was 6 cm, and the hydrogen atmosphere was 1.
．． The pressure was 5×10 Torr.

As a result, the mold surface has a thickness of 1 μm and a hardness of approximately 2000 Hv.
A diamond-like hard carbon film was formed uniformly.

In order to compare the performance of this mold, we compared a mold with the same specifications with 10 μm thick chrome plating (conventional product 1).
Thread molding was performed under the same conditions using molds (comparative products) in which a 1 μm thick TiN film was formed by the ion plating method.

As a result, the conventional product had 1000 shots and the comparative product had 13 shots.
Each mold reached its lifespan after 00 shots, whereas the mold of the present invention could sufficiently withstand even 4000 shots, and the mold life was significantly extended.

Example 2 A segment type mold (material: SKD-3, 50 x 80 x 15
The present invention was applied to

First, a TiN film with a thickness of 2 μm was applied by the ion plating method in a nitrogen atmosphere, 2 × 10 Torr, and 700 V, and then by the DC Plasima method using benzene DC Plasima as the atmosphere and the pressure I × 10 Torr. A diamond-like hard carbon film with a thickness of 1 μm was formed. The hardness of this film was approximately 3000 Hv for both the cavity and the runner, and was uniform.

In order to test the performance of the obtained molds, we tested molds with the same specifications, one with a chrome plating thickness of 5 μm (conventional product), and the other with a 2 μm thick Tj-N film applied using the ion plating method ( A comparative product was made and injection molded using the above resin under the same conditions, and the wear resistance of the cavity and part of the runner was examined.

As a result, in the conventional product, a part of the substrate was exposed in 500 shots of the runner part and in 50,000 shots of the cavity part, and in the comparative product, part of the base material was exposed in 200 shots of the runner part and 3 o, o o o shots of the cavity part.

On the other hand, in the case of the present invention, 1.50
It was able to withstand 0 shots and 70,000 shots in the 5-cavity section, greatly improving wear resistance.

(Effects of the Invention) According to the present invention described above, the surface of the resin mold is directly or indirectly coated with a hard carbon film of Hv 1,800 to 4,000, so that it can maintain good dimensions and shape for a long period of time.
Not only can shape accuracy be maintained, but also excellent wear resistance, corrosion resistance, and mold releasability can be obtained. As a result, the lifespan of resin molds, which used to be unlucky, can be significantly extended.

An excellent effect can be obtained in that molding costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of a resin molding mold obtained according to the present invention, and FIG. 2 is a cross-sectional view schematically showing another example. 1...Mold, 2...Hard carbon film, 3...Hard film

Claims (3)

[Claims] (1) A method for surface treatment of resin molding molds, which comprises applying a hard carbon film to the surface of the resin molding mold. (2) A method for surface treatment of a mold for resin molding according to claim 1, wherein a hard carbon film is directly applied to the surface of the mold. (3) The surface of the resin molding die according to claim 1, which includes coating the mold surface with a hard material film other than a hard carbon film, and then applying a hard carbon film on the hard material film. Processing method.