JPH09262837A - Production of matte mold and molding method using matte mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molded product excellent in scratch resistance in a uniform matte state. SOLUTION: The mold surface constituting the mold cavity of a main mold made of a metal is coated with a heat insulating layer with a thickness of 0.05-2.0mm composed of a heat-resistant polymer and, further, the surface of the heat insulating layer is coated with a metal layer having a thickness of 0.01-0.5mm being 1/3 that of the heat insulating layer. Thereafter, the mold surface coated with the metal layer and the heat insulating layer is made matte by multistage sand blasting treatment and/or multistage etching treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a mold for molding a synthetic resin molded product having an excellent matte surface and a method for molding a synthetic resin using the mold manufactured by the method.

[0002]

2. Description of the Related Art A synthetic resin injection-molded article having a matte surface is generally injection-molded by using a metal mold having a fine uneven surface formed by sandblasting the surface of the metal mold. However, injection-molded products obtained by this method generally have poor mold surface reproducibility, and defects such as unsightly marks such as weld lines and flow marks are conspicuous.

It has been attempted to improve these appearance defects under molding conditions. The mold temperature has the greatest influence among various molding conditions, and the higher the mold temperature is, the more preferable. However, if the mold temperature is set high, the cooling time required for cooling and solidifying the plasticized resin becomes long and the molding efficiency is lowered. Therefore, there is a demand for a method of improving the reproducibility of the mold surface without setting the mold temperature high, or a method of not increasing the required cooling time even if the mold temperature is increased. There is also a method in which heating and cooling holes are attached to the mold respectively and heating and cooling of the mold are repeated by alternately flowing a heat medium and a refrigerant, but this method also consumes a lot of heat. , The cooling time becomes longer.

A method of improving mold surface reproducibility by coating a mold wall forming a mold cavity with a substance having a low thermal conductivity is disclosed in US Pat. No. 3,544,518 for injection molding. US Patent No. 5388
No. 803, a mold surface is coated with a heat insulating layer, the surface is further coated with two metal layers, and the metal layers are etched to a uniform depth to form a textured surface.
rface).

Furthermore, we have molded with a heat-insulating layer coated mold,
A synthetic resin molded article having a matte surface with excellent scratch resistance was reported in WO95 / 35194.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is a metal which has excellent scratch resistance, has a uniform matte surface, has few conspicuous weld lines and the like, and is capable of molding synthetic resin molded products with high productivity. The present invention provides a method for producing a mold and a molding method using the mold. As a method for matting the surface of a mold forming a mold cavity of a metal mold, a method of roughening the mold surface by a sand blast method has been generally used so far. In the heat-insulating-layer-coated mold, the sandblasting method is first considered to roughen the surface of the heat-insulating layer to make it matte. When the surface of the heat-insulating layer of the heat-insulating layer-coated mold or the metal layer on the surface of the heat-insulating layer was matt-shaped and injection-molded with synthetic resin, the surface of the mold was found to be uniform and mat-shaped. Nevertheless, the molded synthetic resin injection-molded product does not have a uniform matte shape, and is very easily scratched by human nails and the like. That is, the unsightly weld line dent is eliminated, but the injection-molded product is easily scratched, and the general part and weld part of the molded product and / or the general part and the resin flow end are non-uniform matte surfaces. The resulting molded product has a prominent defect phenomenon that is prone to occur. The present invention is intended to solve a problem inherent in a molded article molded by using such a heat-insulating layer-coated mold having a matte surface, and provides a mold that solves this problem. That is, the present invention provides a synthetic resin molded article having an excellent appearance, which achieves a reduction in the conspicuousness of the weld line, a uniform matte surface, an improved scratch resistance, etc., without economically increasing the molding cycle time. The present invention provides a method for producing a mold for molding, and a molding method using the mold.

[0007]

Means for Solving the Problems That is, the present invention is as follows. (1) In a method of manufacturing a mold for molding synthetic resin, a mold wall surface forming a mold cavity of a main mold made of metal is set to 0.
A heat insulating layer made of a heat-resistant polymer having a thickness of 05 to 2.0 mm is coated, and the surface of the heat insulating layer is further covered with a metal layer having a thickness of 1/3 or less and a thickness of 0.01 to 0.5 mm. After the coating, the mold surface coated with the heat insulating layer and the metal layer is made into a matte shape by a multi-step sandblasting treatment and / or a multi-step etching treatment, which is a method for producing a matte die. (2) The metal layer is a metal layer having at least two layers such that the surface metal layer on the mold cavity side has a lower hardness and / or a higher etching property than the inner metal layer (1) Manufacturing method of the described mold. (3) The Vickers hardness value of the surface of the metal layer on the mold cavity side is (Vickers hardness −5 of the inner metal layer).
0) value, the matte surface of the metal layer is subjected to a multi-step sandblasting treatment to obtain a matte surface. (4) The etching rate of the metal layer on the mold cavity side surface of the metal layer is twice or more the etching rate of the inner metal layer, and the metal layer is made into a matte surface by a multi-step etching treatment. (2) The method for producing a mold as described. (5) A synthetic resin molding method using a mold manufactured by the mold manufacturing method according to (1), (2), (3) or (4).

Hereinafter, the present invention will be described in detail. The synthetic resin that can be molded with the mold of the present invention is a thermoplastic resin that can be used in general injection molding. For example, polystyrene,
Rubber-reinforced polystyrene, styrene-acrylonitrile copolymer, blend of polyphenylene ether / styrene resin, styrene-methyl methacrylate copolymer, styrene-acrylonitrile-chlorinated polyethylene copolymer, styrene resin such as ABS resin, polyethylene, polypropylene Olefin resin such as vinyl chloride polymer or its copolymer, polycarbonate, polyamide,
It is a thermoplastic resin generally used for injection molding such as polyester. The synthetic resin may contain 1 to 60% by weight of a resin reinforcement. Examples of the resin reinforced product include various rubbers, various fibers such as glass fibers and carbon fibers, and inorganic powders such as talc, calcium carbonate and kaolin.

Among them, the styrene-based resin is preferably used, and the rubber-reinforced styrene-based resin is particularly preferably used. The rubber-reinforced styrene-based resin described here refers to rubber-reinforced polystyrene, ABS resin, AAS resin, MBS resin, etc. in which the rubber phase is distributed in an island shape in the resin phase. Rubber-reinforced polystyrene is a resin in which a rubber phase such as polybutadiene and SBR is dispersed in an island shape in a resin phase of a polymer mainly containing styrene. The ABS resin is a resin in which a rubber phase such as polybutadiene or SBR is dispersed in an island shape in a resin phase of a copolymer mainly composed of styrene and acrylonitrile. The AAS resin is a resin in which the rubber phase of acrylic rubber is dispersed like islands in the resin phase of a copolymer mainly composed of styrene and acrylonitrile, and the MBS resin is mainly composed of styrene and methyl methacrylate. It is a resin in which rubber is dispersed in an island shape in a resin phase composed of a copolymer. Further, blends mainly composed of these resins can be used in the present invention. For example, a rubber-reinforced polystyrene resin containing polyphenylene ether can be favorably used. The injection-molded products of these resins molded by the mold of the present invention have a very good balance of performance and economic efficiency, and are used for weak electric appliances, electronic devices,
It is preferably used as a housing for office equipment, various daily necessities, various industrial parts, and the like.

The manufacturing method of the present invention is preferably applied to a mold for molding a molded product having a so-called weld line portion in which fluid resins are associated and fused during injection molding. Either is fine. Typical molded products are housings for light electrical equipment, electronic equipment, office equipment, etc.
These molded products are generally molded by a multipoint gate, and the present invention is particularly preferably applied to a mold for molding a molded product of the multipoint gate. The multipoint gate described here has two or more gates in one mold cavity, and preferably has 2 to 10 gates. Even a single-point gate is a good target of the present invention when a molded product has many holes and a weld line portion is generated in the molded product.

The welded portion on the surface of the injection-molded article described in the description of the present invention means a region sandwiching the weld line portion. Further, the resin flow end portion means a portion of the mold cavity where the injection resin is finally filled. The general part means a general part excluding the weld part and the resin flow end part from the surface of the molded product. The matte surface according to the present invention is a matte surface having a gloss of 30% or less, preferably 20% or less, on the surface of a molded article molded by the mold. The glossiness is measured according to JIS K710
5. The reflection angle is 60 degrees. The fact that the matte surface has a uniform matte surface means that the matte surface is uniform with the naked eye, and generally, the difference in shade of the matte surface is 0.5 in terms of glossiness.
% Or less, and more preferably 0.3% or less.

The present invention also includes the case where a part of the surface of the molded product becomes a matte surface. For example, when the surface of the molded product is a grain-like surface such as a grain-like surface of a convex portion and a concave portion, and one of the convex portion or the concave portion of the grain-shaped uneven surface is a matte surface and the other is a gloss surface it can. In the present invention, the surface of the injection-molded product has a uniform matte surface with excellent scratch resistance, and by making the weld line inconspicuous, various types of light electrical equipment that have been used by coating the injection-molded product after molding until now are used. The housings of electronic equipment and office equipment can be used without painting.

The matte surface of the synthetic resin injection-molded article molded with the mold of the present invention preferably has a hardness of 2B or less in the pencil scratch test, preferably a hardness of B or less, and has a scratch resistance which does not cause noticeable scratches. It has a good fine uneven surface. More preferably, it has scratch resistance to human nails. The pencil scratch test is measured according to JIS K5401. Conspicuous scratches are scratches that can be easily seen with the naked eye.

The metal of the main mold material described in the present invention is generally iron or various steel materials containing iron as a main component, aluminum or an alloy containing aluminum as a main component, a zinc alloy such as ZAS, and a beryllium-copper alloy. It includes metal molds used for molding synthetic resins. Particularly, steel materials can be used favorably. The heat-resistant polymer used in the heat insulating layer in the present invention is preferably a heat-resistant polymer having a glass transition temperature of 100 ° C or higher, preferably 150 ° C or higher, and / or a melting point of 230 ° C or higher, preferably 250 ° C or higher. Can be used. The toughness of the heat resistant polymer is preferably 5% or more, and more preferably 10% or more. The elongation at break is measured according to ASTM D638, and the tensile speed at the time of measurement is 5 mm / min.

Polymers that can be favorably used as the heat insulating layer in the present invention are heat resistant polymers having an aromatic ring in the main chain, and various amorphous heat resistant polymers soluble in organic solvents, various polyimides, and modified epoxy resins. , And mixtures thereof can be used favorably. Examples of the non-crystalline heat-resistant polymer include polysulfone, polyether sulfone, polyallyl sulfone, polyarylate, and the like, and particularly polysulfone and polyether sulfone can be favorably used.

There are various kinds of polyimides, but linear high molecular weight polyimides and partially crosslinked polyimides can be used.
Thermoplastic polyimide, polyether imide, polyimide which is heated after coating to form an imide ring, and the like can be favorably used. Generally, a straight chain type high molecular weight polyimide has a large breaking elongation and excellent durability, and can be favorably used. Injection molding has economic value in that a molded article having a complicated shape can be obtained by one molding. To coat the surface of this complicated mold with a heat-resistant polymer and firmly adhere it, apply a heat-resistant polymer solution, a heat-resistant polymer precursor solution, a monomer or semi-cured product of the heat-resistant polymer, etc. It is most preferable to form a heat resistant polymer layer by heating and then heating. Therefore, it is preferable that the heat-resistant polymer or the heat-resistant polymer precursor of the present invention can be made into a low-viscosity fluid by being able to be dissolved in a solvent.

Epoxy resins, silicone-based resins, melamine-based resins and the like having flexibility are similarly favorably used. Particularly, the modified epoxy resin having flexibility is preferably used. For example, a polyamide-modified epoxy resin, a polymer alloy made of a mixture of epoxy resin and polyetherimide, a polymer alloy made of a mixture of epoxy resin and polyethersulfone, and the like can be used favorably.

The thickness of the heat insulating layer is appropriately selected within an extremely narrow range of 0.05 to 2.0 mm. Preferably 0.08
˜1.0 mm, more preferably 0.1 to 0.7 mm, most preferably 0.1 to 0.5 mm. When the mold of the present invention is injection-molded, the main mold temperature is 10 ° C. or lower, preferably 8 ° C. lower than the softening temperature of the synthetic resin to be injection-molded.
It is molded at 0 ° C or lower, more preferably at 65 ° C or lower and cooled to 15 ° C or higher.

In injection molding, the mold temperature and the molding cycle time are closely related. That is, in injection molding, the relationship between the mold temperature (Td) and the required cooling time (θ) in the mold is theoretically expressed by the following equation. θ = − (D ² / 2πα) · ln [(π / 4) {(Tx−
Td) / (Tc−Td)｝] θ: Cooling time (sec) D: Maximum thickness of molded article (cm) Tc: Cylinder temperature (° C) Tx: Softening temperature of molded article (° C) α: Heat of resin Diffusivity Td: Mold temperature (° C) Cooling time (θ) is proportional to the square of the molded product thickness (D),
It is a function of the (Tx-Td) value. That is, it is a function of the value obtained by subtracting the mold temperature from the softening temperature of the synthetic resin. When this value is small, a change in this value causes a large change in the cooling time. However, when this value is large, a change in the cooling time becomes small.

Covering the main mold with a heat-insulating layer functions in the same way as increasing the thickness of the molded product and lengthening the cooling time, while decreasing the mold temperature shortens the cooling time. Work towards. It is preferable from the viewpoint of the molding cycle time that the thickness of the heat insulating layer is thin and the appearance can be improved. In the present invention, the thickness of the heat insulation layer is 0.05 to 2.0 mm, preferably 0.08 to 1.0 mm, more preferably 0.1 to 0.7.
mm, most preferably 0.1 to 0.5 mm is good in terms of balance between appearance improvement and molding cycle time.

When the surface of the main mold made of metal is covered with a heat insulating layer and the heated heating resin comes into contact with the surface, the surface of the mold is heated by the heat of the resin. The lower the thermal conductivity of the heat insulating layer and the thicker the heat insulating layer, the higher the mold surface temperature. In the present invention, the mold surface temperature softens the injected synthetic resin during most of at least 0.5 seconds after the injected synthetic resin contacts the mold surface cooled to 80 ° C. or less. It is preferable that injection molding is performed at a temperature or higher.
When there is no heat insulating layer on the mold surface, the mold surface temperature becomes almost the same as the main mold temperature immediately after the synthetic resin comes into contact with the mold surface, that is, within 0.1 seconds. By coating with a heat insulating layer, the mold surface can be kept at the softening temperature or higher for most of 0.5 seconds.

The metal used for the metal layer on the surface of the heat insulating layer is
It is a metal generally used for metal plating and metal spraying,
For example, chromium, nickel, copper, zinc and the like, and alloys mainly containing these metals. The thickness of the metal layer is 1/3 or less of the thickness of the heat insulation layer, and is 0.01 to 0.5 mm,
It is preferably ⅕ or less and 0.02 to 0.3 mm. When the mold surface has a flat surface or a curved surface of a certain kind, a metal plate can be attached to the surface of the heat insulating layer.
In this case, iron, aluminum, or an alloy mainly containing these can be used.

The metal layers of the present invention are best coated by plating. Next, this plating will be described in detail. The plating described here is chemical plating (electroless plating) and electrolytic plating. In the present invention, it is preferable that plating is performed through some of the following steps. That is, first, the surface of the heat insulating layer is made fine and uneven, and then the chemical plating is performed. Pretreatment →
Chemical corrosion (Chemical etching using strong acid solution of strong oxidizer, etc .: Surface is made into fine irregularities) → Neutralization → Sensitization treatment (Activation by adsorbing a reducing metal salt on the synthetic resin surface) The effect is shown.) → Activation treatment (applying precious metal such as palladium having a catalytic action to the resin surface) → Chemical plating (chemical nickel plating, chemical copper plating, etc.) → Electrolytic plating (electrolytic nickel plating, electrolytic copper plating) , Electrolytic chrome plating, etc.).

In order to increase the adhesion between the heat-insulating layer and the plating layer, the heat-insulating material forming the outermost surface of the heat-insulating layer is an inorganic material such as calcium carbonate, silicon oxide, titanium oxide, barium carbonate, barium sulfate, alumina, or various polymers. A fine powdery etching aid such as a fine powder of an organic substance such as the above can be blended, and the powder can be eluted by chemical corrosion to form an appropriate fine uneven surface, which can be used very well.

Next, the chemical nickel plating which can be favorably used in the present invention will be described in detail. In the chemical plating, metal ions are reduced and deposited on a metal by a reducing agent. In general, chemical plating needs to satisfy the following conditions. (1) The reducing agent is stable without self-decomposition while the plating solution is adjusted. (2) The product after the reduction reaction does not precipitate. (3) The deposition rate is p
H, that it can be controlled by the liquid temperature, and the like. In chemical nickel plating, sodium hypophosphite, borohydride, or the like is used as a reducing agent, and sodium hypophosphite is particularly preferably used. In order to satisfy the above conditions, auxiliary components (pH adjusting agent, buffer, accelerator, stabilizer, etc.) are added to the chemical plating solution in addition to the main components (metal salt, reducing agent). When sodium hypophosphite is used as a reducing agent with various auxiliary components, the resulting nickel plating contains phosphorus.

In the present invention, the preferable chemical nickel plating layer which adheres to the heat insulating layer preferably contains phosphorus in an amount of 1% by weight or more and less than 5% by weight. The thickness of this chemical nickel plating layer is generally sufficient to be a thin layer called a primer, preferably about 0.1 to 5 μm. In the heat-insulating layer-coated mold produced in the present invention, it is necessary to firmly adhere the chemical nickel plating layer to the heat-insulating layer,
For this reason, it is extremely preferable to generate plating particles having a small particle size at the initial stage of the chemical nickel plating so that the plating penetrates into the fine irregularities on the surface of the heat insulating layer. After the plating layer having a constant thickness is formed, the plating speed is increased to perform the plating efficiently. As a result, the nickel plating layer in contact with the heat insulating layer becomes a chemical nickel plating layer containing phosphorus in an amount of 1% by weight or more and less than 5% by weight, and the plating layer thereon has an electrolytic nickel plating layer, an electrolytic chromium plating layer, or phosphorus. It becomes a chemical nickel plating layer or the like containing 5 to 14% by weight.

The metal plating on the surface of the polyimide layer most suitable as the heat insulating layer in the present invention will be described in detail. The metal plating on the polyimide surface starts with the polyimide surface treatment. As this method, as shown in U.S. Pat. No. 4,775,449 and U.S. Pat. No. 4,842,946, it is common to treat the polyimide surface with an alkali. That is, polyimide is weak against alkali and the surface is activated. However, since the metal layer on the surface of the heat insulating layer is exposed to severe cooling and heating cycles during molding of the synthetic resin, it is difficult to obtain sufficient adhesion strength to withstand the severe cooling and heating cycle only by treating the polyimide surface with alkali. As a result of various studies, we have covered the polyimide surface layer with polyimide containing a fine powdery etching aid such as calcium carbonate, titanium oxide, and alumina, and etched the surface with a strong acid solution of a strong oxidizer to form a surface layer. Fine powder of existing calcium carbonate, titanium oxide, alumina, etc. and a part of the polyimide are eluted to make the surface of the polyimide layer into fine irregularities, and then neutralized, sensitized and activated to give chemical nickel. It has been discovered that the method of plating can be successfully used in the present invention. As the fine powder, organic substances such as crosslinked rubber fine powder and poorly soluble polymer fine powder can be used.

The thin-layer chemical nickel plating that firmly adheres to the heat insulating layer is a thin layer called a primer, and it is preferable that various plating layers of two or more layers suitable for the present invention are further formed thereon. Therefore, it is preferable to add three or more plating layers in addition to the thin chemical nickel plating layer. Preferred specific examples of the plating further applied on the thin chemical nickel plating are as follows. (1) Chemical nickel plating (containing 5 to 18 wt% phosphorus) (2) Electrolytic chrome plating (hard chrome plating, etc.) (3) Electrolytic nickel plating (bright nickel plating, semi-bright nickel plating, matte nickel plating, etc.) (4) Chemical copper plating (5) Electrolytic copper plating In the present invention, it is preferable that two or more metal layers selected from these platings are coated.

These metal platings which can be preferably used in the present invention are in close contact with the heat insulating layer at the interface of fine irregularities. Therefore,
The interface between the plating layer and the heat insulating layer has a shape in which the plating layer and the heat insulating layer are inserted into each other. In this case, the thickness of the metal layer described in the present invention is the thickness of the portion where the metal occupies 50% by volume or more, and the thickness of the heat insulating layer is the thickness of the portion where the heat insulating material exceeds 50% by volume.

The metal layer is ⅓ or less of the thickness of the heat insulation layer and has a thickness of 0.01 to 0.5 mm. Further, the metal layer of the present invention preferably has two or more metal layers such that the surface metal layer on the mold cavity side has a lower hardness and / or a higher etching property than the inner metal layer.
In the two or more metal layers, the thickness of the surface metal layer on the side of the mold cavity is preferably 1/2 or more, more preferably 2/3 or more of the thickness of all metal layers. The thickness of the inner metal layer is preferably 0.002 to 0.1 mm, more preferably 0.003 to 0.05 mm.
In order to make the metal layer matte by multi-stage sandblasting, the Vickers hardness value of the surface metal layer is preferably smaller than the (Vickers hardness-50) value of the inner metal layer. That is, it is preferable that the surface metal layer is formed of a metal that is easily roughened by sandblasting. It is difficult to directly compare the hardness of an object with a numerical value when the type of material is different, but in the present invention, the Vickers hardness (HV) will be used for comparison. Vickers hardness (HV) is a method of expressing hardness by dividing the surface area of the thick dent dent that has caused a load by using a diamond pyramid having an apex angle of 136 degrees as an indenter, and the unit is kg / mm ² . Show.

The sandblast treatment described in the present invention is
It is a sandblasting process that makes the surface of a general mold matte, and it sprays inorganic particles such as carborundum and glass of various particle sizes and shapes together with a pressurized gas onto the mold surface to make the mold surface matte. Multi-stage sandblasting is a process of removing particles with different particle sizes, shapes, materials, etc.
To be sandblasted more than once. It is preferable to perform sandblasting of angular particles and sandblasting of spherical particles in combination. The multi-stage sandblasting treatment of the present invention is to perform different sandblasting treatments twice or more, preferably 3 to 6 times. In this case, it is not necessary that all of the 3 to 6 degree sandblasting processes are different processes. For example, two types of processing, A processing and B processing, may be repeatedly performed. It is difficult to obtain the matte surface required by the present invention by one-step sandblasting.

The hardness of the chemical nickel plating (electroless nickel plating) varies depending on the phosphorus content contained, but also depends on the heat treatment after plating. The change in hardness due to the heat treatment of nickel plating is described in ISO DIS 4527 and the like. The multi-step etching of the present invention is two or more steps,
It is preferable to perform the etching process repeatedly over 3 to 10 steps, more preferably 4 to 8 steps. It is difficult to obtain the matte surface required by the present invention by a single etching process.

When the surface of the metal layer is made to have a matte shape by a multi-step etching treatment, it is preferable that the etching rate of the surface metal layer on the mold cavity side is twice or more the etching rate of the inner metal layer. If the metal layer is a metal that can be etched with a general etching solution such as electrolytic nickel plating, electrolytic copper plating, or chemical nickel plating, the same etching method as that used for graining general metal molds can be used. . That is, the surface of the metal layer is partially masked with an ultraviolet curable resin and then etched with a ferric chloride solution or an acid solution. This masking and etching are repeated to make the surface metal layer matt.

When the metal layer is nickel-plated, the chemical nickel plating having a phosphorus content of 8% by weight or more is difficult to etch, and the chemical nickel plating having a lower phosphorus content is easily etched. For the phosphorus content and acid resistance of chemical nickel plating, see Plating and Surfac.
e Finishing, 79 (3) P. 29-33
(1992), the higher the phosphorus content, the better the acid resistance. According to the above-mentioned literature, acid resistance has a phosphorus content of 1
0-12% by weight Good, 7-9% by weight Fair,
Poor at 1 to 4% by weight. The phase diagram of the nickel-phosphorus alloy shows that the phosphorus content is 0-4.5% by weight in the β phase, 1
1 to 15 wt% is the γ phase, and 4.5 to 11 wt% is the γ phase.
It is a mixture of phase and β phase. The γ-phase is excellent in corrosion resistance to acids, and when it is 8% by weight or more, which is generally said to have a high phosphorus content, the corrosion resistance is large. The inner metal layer of the metal layer of the present invention is preferably high phosphorus content nickel having excellent corrosion resistance, and the surface metal layer is preferably nickel having a phosphorus content of less than 8% by weight and 3% by weight or more.

Even in the electrolytic nickel plating, the etching property varies depending on the composition, and also varies depending on the sulfur content and the phosphorus content.
The higher the phosphorus content, the better the corrosion resistance. In the present invention, the etching rate of the surface metal layer is preferably twice or more the etching rate of the inner metal layer, and more preferably 3 times.
It is at least twice, and particularly preferably at least five times.

Multi-stage sandblasting as described in the present invention,
And / or performing the multi-stage etching treatment also includes performing the treatment twice or more in total by using the sandblasting treatment and the etching treatment together. Even in this case, it is preferable to perform the treatment three times or more in total. The method of combining the multi-step etching treatment and the single-step or multi-step sandblasting can be used most favorably.

When the heat-plasticized synthetic resin is injected into a cooled metal mold which is generally used for injection molding, as soon as the synthetic resin comes into contact with the mold surface, cooling starts from the contact surface. Immediately thereafter, a solidified layer of the synthetic resin is formed on the mold surface, and the thickness of the solidified layer increases with the passage of time. The thickness of the solidified layer varies depending on the temperature of the synthetic resin, the softening temperature of the synthetic resin, the thermal conductivity of the synthetic resin, the latent heat of crystallization of the synthetic resin, the temperature of the mold, the thermal conductivity of the mold, etc. It is considered that the solidified layer is formed several microseconds to several tens of microseconds after the synthetic resin comes into contact with the mold, and the solidified layer becomes thicker with time. In such general injection molding, it is considered that a thin solidified layer has already been formed on the surface layer of the synthetic resin in contact with the mold surface when the injection pressure required to reproduce the mold surface is applied to the synthetic resin. In order to improve the mold surface reproducibility of the synthetic resin in such a state, it is necessary to press the resin surface of the thin solidified layer against the mold wall surface to reproduce the mold surface, and it is necessary to apply a considerably high pressure. Therefore, in general injection molding, the mold surface reproducibility in the vicinity of the gate where a high injection pressure is applied is improved.

On the other hand, when injection molding is performed using a mold in which the surface of the metal mold is covered with a heat insulating layer, the heat insulating layer is heated by the injected synthetic resin to raise the temperature, and then cooling is started. Synthetic resin that is in contact with the mold surface covered with a heat-insulating layer of appropriate thickness is kept above the softening temperature of the synthetic resin for several hundred microseconds after the contact, and no solidified layer is formed during that time. , Then a solidified layer begins to form.
Therefore, when the heat insulating layer-coated mold is used, it becomes possible to apply the pressure necessary for reproducing the mold surface to the synthetic resin on the mold surface in the state where the solidified layer is not yet formed on the mold surface. If the mold surface of the heat-insulating layer-coated mold has a fine uneven matte shape, the synthetic resin will flow sufficiently into the recesses of the fine unevenness of the mold surface before the solidified layer is formed, and the mold surface will be reproduced sufficiently. To be done. Even if the concave portions of the fine irregularities on the mold surface have an acute angle, they can be sufficiently reproduced. As a result, the matt shaped article molded by the heat-insulating layer-coated mold has sharp convex portions of the fine irregularities on its surface, and when a human nail or the like comes into contact with the molded article, the sharp edges of the surface irregularities are damaged. Easily become scratched.

The change in mold surface temperature during injection molding can be calculated from the temperatures of the synthetic resin, the main mold, the heat insulating layer, specific heat, thermal conductivity, density, latent heat of crystallization and the like. For example, ABAQUS (software of US HKS), ADINA and AD
It can be calculated by transient heat conduction analysis by a nonlinear finite element method using INAT (software developed at the Massachusetts Institute of Technology). In the calculation of the change in the mold surface temperature shown in the drawing of the present invention, the shear heat generation of the synthetic resin during injection molding and the boundary film heat transfer coefficient between the layers are ignored. The mold surface temperature change shown in the drawings of the present invention is a value calculated using ABAQUS under the above conditions. The present invention will be described with reference to the drawings.

1, 2 and 3 show the main mold temperature of 50.
Shown are the calculated values of the change in temperature distribution near the surface of the mold when injection-molded at a temperature of 240 ° C. and a temperature of rubber-reinforced polystyrene of 240 ° C. The numerical value of each curve in the figure indicates the time (second) from when the heated synthetic resin comes into contact with the cooled mold wall. The heated synthetic resin comes into contact with the mold surface and is rapidly cooled, while the mold surface receives heat from the heated synthetic resin to rise in temperature. As shown in the figure, when the mold surface is covered with a heat insulating layer (polyimide) (FIGS. 2 and 3), the temperature of the surface of the heat insulating layer in contact with the synthetic resin increases, and the temperature decreasing rate also decreases.

When the synthetic resin is coated with the heat insulating layer, the mold surface temperature becomes higher as the time after the synthetic resin comes into contact with the mold wall becomes shorter, and the mold temperature is greatly increased by the heat insulating layer coating. The same effect can be obtained. 4, FIG. 5, FIG. 6, FIG. 7, and FIG.
And, FIG. 9 shows the temperature of the main mold using a mold in which the surface of the main mold made of steel is coated with a polyimide layer and the surface thereof is coated with a nickel layer, and a mold in which only the polyimide layer is coated for comparison. Is set to 50 ° C., and the temperature of the resin surface after the resin comes into contact with the outermost surface of the mold when the rubber-reinforced polystyrene resin is injection-molded in the mold at a temperature of 240 ° C. The temperature at the interface of the nickel surface, or the temperature at the interface of the resin surface and the polyimide surface).

FIG. 4 shows the resin surface temperature when the thickness of the polyimide (hereinafter referred to as PI in the figure) layer is 0.30 mm and the thickness of the nickel (hereinafter referred to as Ni in the figure) layer is 0.02 mm. The change over time is shown. In the figure, the solid line is the case where the polyimide layer and the nickel layer are covered, and the broken line is the case where only the polyimide layer is covered. When coated only with polyimide, the resin surface temperature decreases with the passage of time, whereas when coated with a polyimide layer and a nickel layer, the temperature once drops significantly and then gradually rises and then gradually drops . This is because the heat of the resin is absorbed by the nickel layer and decreases because the surface nickel layer has a large heat capacity. Therefore, as the thickness of the nickel layer increases, the temperature range that decreases once becomes wider and the temperature that rises again decreases.

FIG. 5 shows a case in which the thickness of the nickel layer is increased to 0.1 mm. When the thickness of the nickel layer is increased, the temperature range that temporarily decreases is large and the temperature that rises again becomes low. FIG.
And FIG. 7 show the case where the thickness of the polyimide layer is 0.15 mm with the same layer structure as in FIGS. 4 and 5. Even when the thickness of the polyimide layer is 0.15 mm, the same tendency as in FIGS. 4 and 5 is observed.

FIGS. 8 and 9 collectively show the results of FIGS. 4 to 7. From FIG. 8 and FIG. 9, in the case of the mold in which the nickel layer is coated on the heat insulation layer, when the thickness of the nickel layer becomes 0.1 mm, the surface temperature once lowered becomes lower and the temperature rises again. It can be estimated that the mold surface reproducibility at the time of molding deteriorates. Thickness of nickel layer is 0.02
In the case of mm, the resin surface temperature recovers rapidly even if it drops once, and the temperature is also high, so the mold surface reproducibility during injection molding is good. From these facts, there is a limit to the thickness of the metal layer coated on the surface of the heat insulating layer in order to improve the mold surface reproducibility, and if the metal layer thickness exceeds 1/3 of the thickness of the heat insulating layer, the mold surface reproducibility becomes poor. The absolute value of the metal layer thickness is selected from the range of 0.01 to 0.5 mm, preferably 0.02 to 0.3 mm.

FIG. 10 shows a mat-like molded product (1 with excellent scratch resistance, which is molded by the mold manufactured by the mold manufacturing method of the present invention.
0-1) and a cross section of a matte molded product (10-2) which is easily scratched and is molded by a conventional mold. The molded product molded with the mold of the present invention shown in (10-1) is a synthetic resin molded product 1.
Although the tip 3 of the concave portion on the surface of the fine unevenness has an acute angle, the tip 2 of the convex portion is rounded and is less likely to be scratched. On the other hand, in the conventional molded product shown in (10-2), both the convex tip 4 and the concave tip 3 of the unevenness are acute angles, and when the surface of the molded article is rubbed with a human nail or the like, Tip 4 is easily scraped off and easily scratched. The present invention provides a metal mold for molding a molded product shown in FIG. 10-1 in which the ratio of the tip of the convex portion to the acute angle is small, and therefore, the nail is difficult to be scratched. It is an object.

This will be described in more detail with reference to the injection molded article shown in FIGS. 11 and 12. In FIG. 11, the synthetic resin injected from the gate 5 flows around the hole 6 and coalesces at the weld to form the weld line 7. In FIG. 12, when injection molding is performed with a die coated with a heat insulating layer having a fine uneven surface, the fine uneven surface of the heat insulating layer is transferred to the surface of the molded product. However, when injection molding is performed with a heat-insulating layer coating mold having fine irregularities by a sandblasting method generally used for matting, a region from the weld portion to the resin flow end portion of the molded product 8 (hereinafter, in the description using the drawings, (The weld portion 9 is abbreviated.) The degree of fine unevenness becomes large, and when molded with a black colored resin, the weld portion 9 becomes dark and the general portion 10 becomes whitish, and a molded article of uniform glossiness described in the present invention is obtained. Hard to become. The cause is estimated as follows. The cause will be described with reference to FIGS. 13 and 14.

In the injection molding of the molded product shown in FIG. 12, the pressure applied to the mold surface of the weld part 9 and the general part 10 is shown in FIG. 13 as a model. In FIG. 13, the pressure applied to the general part 10 of the molded product is the curve 11, and the pressure applied to the weld part 9 is the curve 12. Curve 13 is the pressure on the gate. That is, the pressure applied to the general portion 10 gradually increases as the injection time elapses, while the weld portion 9
High pressure is applied to the mold at the same time when the synthetic resin comes into contact with the mold surface. As shown in FIG. 2, the heated synthetic resin contacts the mold surface of the heat insulating layer to heat the surface of the heat insulating layer, and immediately cooling starts. In FIG. 2, the mold surface is lowered to 100 ° C. or lower after 0.52 seconds, and the synthetic resin in contact with the mold surface is also lowered. In order to reproduce the mold surface better, the heated synthetic resin comes into contact with the mold surface and high pressure is applied to the resin at the same time, that is, high pressure is applied to the resin while the mold surface and the surface layer of the synthetic resin are at high temperature. This is preferable. FIG.
As shown in (1), the synthetic resin comes into contact with the mold surface at the weld portion, and at the same time, a high pressure is applied to the resin, and the fine irregularities on the mold surface are more accurately reproduced.

This process will be described as a model with reference to FIG.
In 14-1, the mold surface is composed of a heat insulating layer 14 and a metal layer 15 having fine irregularities on the surface thereof. The fine irregularities on the surface have concave portions 16 with an acute angle. When injection molding is performed with this mold, the resin pressure gradually increases in the general part of the molded product after the synthetic resin 17 contacts the mold surface, so the mold surface and the surface layer of the resin cool during the pressure increase, A part 18 that cannot be filled in is generated because it cannot penetrate deep into the fine irregularities on the mold surface (14-
2). On the other hand, in the weld portion of the molded product, the synthetic resin 17 contacts the mold surface and at the same time the resin pressure rises, so that the synthetic resin can penetrate deep into the fine irregularities of the mold (14).
-3). As a result, in the welded portion 9 shown in FIG. 12, the surface irregularity of the molded product becomes larger than in the general portion 10, and the welded portion becomes blackish with the black colored synthetic resin, and a uniform matte state is not obtained.

Such a phenomenon remarkably appears when a matte molded article is injection-molded with a heat insulating layer-coated mold. The present invention provides a mold for molding a molded product in which this defective phenomenon is improved. In order to make the surface unevenness of the welded part and the general part of the molded product uniform, it is necessary to make the fine unevenness of the surface of the heat insulating layer into an appropriate uneven shape. Although the present invention has been described with reference to a molded product having a simple shape shown in FIG. 12, the housing of the light electric device has a complicated shape molded by a multi-point gate, and a molded product having such a complicated shape is generally used. In addition to the difference in the matteness between the welded part and the welded part, there is often a difference in the mattedness between the left and right sides of the weld line. The difference between the left and right sides across the weld line occurs when there is a difference in the flow velocity of the left and right resins. The resin on the side with a high flow velocity is applied with resin pressure quickly after it contacts the mold surface, and the resin on the side with slow flow rate is applied slowly with the resin after contacting the mold surface, which tends to cause a difference in mold surface reproducibility between left and right. . The present invention is particularly effective in such a case.

15, 16 and 17 show preferred examples of the mold manufacturing method of the present invention. In FIG. 15, a heat insulating layer 14 having a thickness of 0.05 to 2.0 mm is provided on the surface of the main mold 20 made of metal, and a thin metal layer for strengthening the adhesion is attached on the heat insulating layer 14. Two metal layers 21, 2 on the surface
2 are coated. The thin metal layer for strengthening the adhesion between the heat insulating layer and the metal layer is much thinner than the metal layers 21 and 22, and is therefore omitted in FIGS. The total thickness of all metal layers including the metal layers 21 and 22 is ⅓ or less of the thickness of the heat insulating layer 14, and 0.01 to 0.
5 mm. The metal layer attached on the thin metal layer for strengthening the adhesion between the heat insulating layer and the metal layer is composed of two layers,
The thickness of the surface metal layer 22 is preferably 1/2 or more, more preferably 2/3 or more of the thickness of all metal layers. The preferable thickness of the inner metal layer 21 is 0.002 to 0.
1 mm, more preferably 0.003 to 0.05 m
m. The etching rate of the surface metal layer 22 is 2 times or more, preferably 3 times or more, more preferably 5 times or more that of the inner metal layer 21. This mold is subjected to an etching treatment, and mainly the surface metal layer 22 is selectively etched to obtain the mold required by the present invention shown in (15-2).

By the etching process shown in FIGS. 16 and 17,
The method for making the surface metal layer of the mold into the matte shape required by the present invention will be described in more detail. In FIG. 16, the mold surface forming the mold cavity of the metal main mold 20 is covered with the heat insulating layer 14 (16-1). Next, a thin metal layer (not shown in the figure) and two metal layers 2 are formed on the surface of the heat insulating layer 14.
3, 24 are coated (16-2). The etching rate of the surface metal layer 24 of the metal layer is preferably twice or more the etching rate of the inner metal layer 23, more preferably 3 times or more, and most preferably 5 times or more. The surface of the metal layer 24 is coated with a photosensitive resin 25 (16-3). Then
Mask with the mask sheet 26. UV irradiation is carried out to cure the photosensitive resin in the irradiated part (16-
4). Next, the uncured portion of the photosensitive resin is washed and removed to leave the patterned cured resin 27 (1
6-5). Then, the metal layer in the portion not covered with the cured resin 27 is dissolved by etching to form a mold surface having the metal layer 24 having an uneven surface (16-6). Further, the steps from the coating (16-3) of the photosensitive resin to the etching (16-6) are repeated.

FIG. 17 shows the etching steps after the second step of the multi-step etching. In FIG. 17, the surface metal layer 24 (17-1) made uneven by the first etching is coated with the photosensitive resin 25 (17-2), and the surface is subjected to pattern masking for exposure, development, After washing (17-
3), etching is performed to make the surface more uneven (17-
4) and then the steps (17-2) to (17-4) are repeated to obtain a mold (17-5) required by the present invention. The etching hits the inner metal layer 23 having excellent etching resistance, the etching rate is slowed there, the bottom of the recess of the metal layer is rounded, and no acute-angled recess is formed. (17-
By injection molding using the mold shown in FIG. 5), a molded article having excellent scratch resistance required by the present invention shown in FIG. 10-1 can be obtained.

FIGS. 16 and 17 show a method in which a photosensitive resin is applied to the entire surface of the mold, covered with a masking film and exposed, and FIG. 18 shows a more excellent method. FIG.
8, the photosensitive resin is finely applied at intervals so as to be sprinkled on the surface of the metal layer, which is irradiated with ultraviolet rays to be cured (18-1), and then the surface metal layer 24 is made uneven by etching. -2). This photosensitive resin sprinkling coating, ultraviolet irradiation (18-3) and etching treatment (18-4) are repeated, and this step is repeated several times to obtain a matte surface mold required by the present invention (18-
5). In the present invention, the steps from the application of the photosensitive resin to the etching are preferably repeated 3 to 10 times, more preferably 4 to 8 times to obtain a fine uneven surface having a preferable shape. The fine uneven matte surface obtained by the multi-step etching treatment of the present invention has a matte surface on the mold surface, and a thin corrosion-resistant metal layer that does not significantly change the fine uneven shape is used for durability during injection molding. It is effective for improvement and is included in the present invention.

The present invention can be successfully used in injection molding, and although injection molding has been described, it can be applied to other molding methods.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following main mold, heat insulating layer, metal layer and synthetic resin are used. Main mold: A steel (S55C) mold for injection molding, which has a mold cavity for the molded product 5 shown in FIGS. 11 and 12. The molded product has a size of 100 mm × 100 mm and a thickness of 2 mm, and has a hole 6 of 30 mm × 30 mm in the center. The gate 5 is a side gate as shown in the figure, and a weld line 7 is generated in the molded product 8. The mold surface is mirror-like. Four inserts forming the mold cavities of this main mold are prepared, and hard chromium plating is performed on the surface forming the mold cavities of the two inserts. Insulating layer A: A polyimide varnish (Treney's # 3000, manufactured by Toray Industries, Inc.) is applied to the insert surface of the chrome-plated main mold and heated at 160 ° C, and then this application and heating are repeated to give a predetermined thickness. Then, it is heated to 290 ° C. and imidized to 100% to form a polyimide layer of a predetermined thickness that is in close contact with the main mold. Heat-insulating layer B: A polyimide varnish (Treney's # 3000, manufactured by Toray Industries, Inc.) is applied to the insert surface of the chrome-plated main mold, heated at 160 ° C., and then this application and heating are repeated to give a predetermined thickness. Finally, a thin layer of polyimide varnish prepared by blending 11% by weight of a fine powder of calcium carbonate having an average particle size of 0.1 μm in a solid content ratio and sufficiently kneading is applied to the outermost surface of the heat insulating layer to cover it. Two
It is heated to 90 ° C. and 100% imidized. 20 on the outermost surface
A polyimide layer having a predetermined thickness having a mixed polyimide layer having a thickness of μm is formed. Metal layer A: The heat insulation layer surface is etched with a strong acid solution containing chromic acid, and then neutralized → sensitized →
It was formed by performing activation treatment in this order, and then performing chemical nickel plating with sodium hypophosphite as a reducing agent.
~ 4 wt% chemical nickel plating. Metal layer B: Chemical nickel plating having a phosphorus content of 8 to 9% by weight, formed using sodium hypophosphite as a reducing agent. Metal layer C: Chemical nickel plating having a phosphorus content of 5 to 6% by weight, formed using sodium hypophosphite as a reducing agent. The acid etching rate of the metal layer C is 5 times or more the metal rate B. Injection-molded synthetic resin: Rubber-reinforced polystyrene (Asahi Kasei Polystyrene 495, manufactured by Asahi Kasei Kogyo Co., Ltd.)
Black colored product. The molding conditions are a resin temperature of 240 ° C and a mold temperature of 40 ° C. Measurement of surface unevenness pattern: Surface roughness measuring instrument (Co., Ltd.)
Measured with Tokyo Seimitsu Surfcom 570A).

[0056]

Example 1 The surface of the heat insulating layer of the main mold coated with the heat insulating layer B of 0.2 mm was coated with the metal layer A having a thickness of 0.0005 mm, and the surface was coated with the metal layer B having a thickness of 0.01 mm. The surface is coated with a metal layer C having a thickness of 0.03 mm. Using this mold, the matte surface mold of the present invention is obtained by the six-step acid etching treatment shown in FIG. In FIG. 18, the metal layer A is omitted because it is a thin layer. Injection molding of a synthetic resin is performed using the obtained mold of the present invention. The weld line of the injection-molded product was not conspicuous, and the general part and the weld part had a uniform matte surface, the glossiness was 20% or less, and no conspicuous scratches were found with a pencil scratch test 2B hardness. The uneven shape of the surface of the injection molded product is shown in FIG. The uneven shape of the surface of the injection-molded product is a surface shape that is less likely to be scratched because there are few acute-angled convex portions protruding to the surface.

[0057]

[Comparative Example 1] The surface of the polyimide-coated mold of the main mold coated with the heat insulating layer A having a thickness of 0.2 mm is subjected to a one-step sandblast treatment to obtain a matte surface. A synthetic resin is injection-molded by using this surface finely textured polyimide-coated mold. The dent of the weld line of the molded product is 1 μm or less, and the weld line is not conspicuous, but there is a difference in the matting degree between the general part 10 and the weld part 9 (the region from the weld part to the resin flow end), and the surface is uniform. Does not become a matt molded product. That is, the weld portion 9 is dark and the general portion 10 is whitish.
FIG. 20 shows a surface uneven pattern. 20-1 shows the surface unevenness pattern of the polyimide-coated mold, 20-2 shows the surface unevenness pattern of the general part of the molded product, and 20-3 shows the surface unevenness pattern of the weld part 5 of the molded product. The surface unevenness pattern is obviously different between the general part and the weld part 5 of the molded product.
The matte surface of the welded part 5 has a noticeable scratch with a 2B hardness of the pencil scratch test.

[0058]

[Comparative Example 2] The surface of the main mold which is not plated with chrome is made into a matte surface by sandblasting. A synthetic resin is injection-molded using this matte mold. When the mold without the heat insulating layer is used, unsightly weld lines are conspicuous in the molded product.

[0059]

[Comparative Example 3] The surface of the main mold not plated with chromium is subjected to the three-layer plating of Example 1 having no heat insulating layer and the multi-step etching treatment to obtain a mold having a fine uneven surface similar to that shown in FIG. Weld lines are conspicuous in the molded product obtained by injection molding synthetic resin with this mold.

[0060]

INDUSTRIAL APPLICABILITY By performing injection molding using the mold of the present invention, excellent matte injection molding with less conspicuous weld lines can be obtained. Until now, such molded products have been produced by matting the molded product. However, in recent years, environmental damage due to evaporation of the paint solvent has become a major social problem, and reduction of production cost is required. With this molded product, it is possible to obtain a molded product that can be put to practical use by omitting the coating after molding, and its economic effect is enormous.

[Brief description of drawings]

FIG. 1 shows a change (calculated value) in temperature distribution near the mold surface when a heated synthetic resin comes into contact with a steel main mold.

[Fig. 2] Changes in temperature distribution (calculated value) near the mold surface when heated synthetic resin comes into contact with a mold in which the mold surface of a steel main mold is coated with 0.1 mm of polyimide Show.

FIG. 3 shows changes in temperature distribution (calculated value) near the mold surface when heated synthetic resin comes into contact with a mold whose surface is a steel main mold covered with 0.5 mm of polyimide. Show.

FIG. 4 is a diagram illustrating a synthesis when a heated synthetic resin is brought into contact with a mold in which 0.3 mm of polyimide is coated on the surface of a steel main die and 0.02 mm of nickel is further coated on the surface of the main die. The temperature change (calculated value) of the resin surface (the interface between the resin surface and the mold surface) is shown.

FIG. 5 is a diagram illustrating a synthesis when a heated synthetic resin is brought into contact with a mold in which 0.3 mm of polyimide is coated on the surface of a steel main die and 0.1 mm of nickel is further coated on the surface of the main die. The temperature change (calculated value) of the resin surface (the interface between the resin surface and the mold surface) is shown.

[FIG. 6] Synthesis when heated synthetic resin comes into contact with a mold in which a mold surface of a steel main mold is coated with 0.15 mm of polyimide, and the surface of the main mold is further coated with 0.02 mm of nickel The temperature change (calculated value) of the resin surface (interface between the resin surface and the mold surface) is shown.

FIG. 7 shows the synthesis when a heated synthetic resin comes into contact with a mold in which a mold surface of a steel main mold is coated with 0.15 mm of polyimide and the surface thereof is further coated with nickel of 0.1 mm. The temperature change (calculated value) of the resin surface (the interface between the resin surface and the mold surface) is shown.

FIG. 8: A mold surface of a steel main mold is coated with 0.3 mm of polyimide, and the surface is further covered with 0.0005 mm, 0,
The temperature change (calculated value) of the synthetic resin surface (interface between the resin surface and the mold surface) when heated synthetic resin comes into contact with the mold coated with nickel of each thickness of 02 mm and 0.1 mm is shown.

FIG. 9: A mold surface of a steel main mold is coated with 0.15 mm of polyimide, and the surface is further coated with 0.0005 mm of polyimide.
The temperature change (calculated value) of the synthetic resin surface (interface between the resin surface and the mold surface) when the heated synthetic resin comes into contact with the mold coated with nickel of each thickness of 0.02 mm and 0.1 mm. Show.

FIG. 10 shows a cross section of a molded product injection-molded by the mold of the present invention and a cross-section of a molded product injection-molded by a conventional mold.

FIG. 11 is a perspective view showing an example of an injection molded product.

12 is an explanatory view of the injection-molded product shown in FIG.

FIG. 13 is a graph showing changes over time in resin pressure applied to the mold surface during injection molding.

FIG. 14 is an explanatory diagram showing, as a model, how the injection-molded synthetic resin fills the fine irregularities on the mold surface.

FIG. 15 shows a sectional view of a mold for molding the molded article of the present invention.

FIG. 16 shows each step of etching the mold surface.

FIG. 17 shows each step of performing a multi-step etching process on the mold surface.

FIG. 18 shows each step of performing a multi-stage etching process on the mold surface.

FIG. 19 is a graph showing a surface unevenness pattern of a molded product in Example 1.

FIG. 20 is a graph showing surface unevenness patterns of a mold and a molded product in Comparative Example 1.

[Explanation of symbols]

 1 Synthetic resin molded product 2 Molded product unevenness convex part 3 Molded product unevenness concave part 4 Molded product unevenness convex part 5 Gate 6 Hole part 7 Weld line 8 Molded product 9 Area from weld part to resin flow end part 10 General part 11 Resin Pressure Curve for General Part 12 Resin Pressure Curve for Weld Part 13 Resin Pressure Curve for Gate Part 14 Heat Insulation Layer 15 Metal Layer 16 Recess on Metal Layer Surface 17 Synthetic Resin 18 Recess Not Filled with Synthetic Resin 19 Inventive Gold A sharp concave portion intended to be removed by the mold 20 Main mold 21 Inner metal layer 22 Surface metal layer 23 Inner metal layer 24 Surface metal layer 25 Photosensitive resin 26 Mask sheet 27 Cured resin

Claims (5)

[Claims] 1. A method for producing a mold for molding synthetic resin, comprising:
The mold wall surface of the mold cavity of the main mold made of metal is covered with a heat-insulating layer made of a heat-resistant polymer having a thickness of 0.05 to 2.0 mm, and the surface of the heat-insulating layer has a thickness of 1 of the thickness of the heat-insulating layer. /
After coating with a metal layer having a thickness of 3 or less and a thickness of 0.01 to 0.5 mm, the mold surface coated with the heat insulating layer and the metal layer is made matte by multistage sandblasting and / or multistage etching. A method for producing a matte mold, which is characterized in that 2. The metal layer is a metal layer having at least two layers such that the surface metal layer on the mold cavity side has a lower hardness and / or a higher etching property than the inner metal layer. Item 1. A method for producing a mold according to item 1. 3. The surface of the metal layer on the side of the mold cavity has a Vickers hardness value smaller than the (Vickers hardness-50) value of the inner metal layer, and the metal layer has a matte surface by a multi-step sandblast treatment. The method for producing a mold according to claim 2, wherein 4. The etching rate of the surface metal layer of the metal layer on the mold cavity side is 2 times the etching rate of the inner metal layer.
It is more than double, and the metal layer is made into a matte surface by a multi-step etching treatment. 5. A synthetic resin molding method using a mold manufactured by the mold manufacturing method according to claim 1.