Patent Description:
A conventional interior component such as a door trim for lining the cabin of an automobile is generally an injection-molded synthetic resin product, in consideration of manufacturability and moldability. A known interior component is made up of the mold product as a base member and a natural-leather or artificial-leather surface member, which is bonded to the surface of the base member for the purpose of implementing upscale material texture or a sophisticated motif.

A recent known interior component has its base member's motif surface (front surface) provided with a grain pattern formed of minor uneven shapes, so as to resemble natural leather in appearance. Thus, without the surface member, the interior component successfully resembles the texture of natural leather by the base member alone. That is, the interior component with upscale material texture or a sophisticated motif is provided cost-effectively and productively. The forming the grain pattern on the surface of the base member is performed simultaneously with injection molding, using a die body which includes a leather-grain transfer surface with uneven shapes corresponding to the grain pattern.

For example, Patent Literature <NUM> discloses a mold die including a mold cavity whose surface is provided with a grain pattern. On the surface of the grain pattern, a plating layer which contains a luster agent is provided. Patent Literature <NUM> also discloses that the thickness of the plating layer falls within a range of <NUM> to <NUM>.

Patent Literature <NUM> discloses an injection mold with an etched leather grain surface texture, a method of manufacturing the mold and molding method using the mold. Patent Literature <NUM> discloses a fine drawing pattern having a depth of <NUM> to <NUM> and a size of <NUM> to <NUM> in diameter. The skin drawing pattern is applied to the molding surface of the mold by etching, and a finer drawing pattern than the skin drawing pattern is provided by etching.

Here, in the conventional mold die, minor defects disadvantageously exist at the surface (the mold surface) of the die body. As a result of being filled with resin, the defects create minor burrs on the surface of the mold product, which impair the surface quality. Since the defects each have an undercut shape, the resin at the surface of the mold product is pulled when being released from the mold die. This invites generation of the burrs.

Meanwhile, as disclosed in Patent Literature <NUM>, the plating layer at the surface of the mold die coats such defects. This alleviates the defects at the surface of the mold product associated with the defects. On the other hand, there are increasing demands for a grain pattern which is formed of finer uneven shapes than the conventional ones, so as to implement the natural authentic texture of natural leather. Here, the plating layer disclosed in Patent Literature <NUM> disadvantageously covers not only the defects but also a fine grain pattern, and fails to provide the surface quality that a mold product is desired to possess.

The present invention has been made in view of the circumstances, and an object thereof is to provide a mold die capable of implementing a fine grain pattern on a mold product with excellent surface quality, a method of manufacturing the mold die, an injection molding apparatus, and a method of manufacturing the mold product.

In order to solve the problem, a first inventive aspect provides a mold die according to claim <NUM>.

A second inventive aspect provides a method of manufacturing a mold according to claim <NUM>.

A third inventive aspect provides an injection molding apparatus according to claim <NUM> including the mold die according to the first inventive aspect.

A fourth inventive aspect provides a method of manufacturing a mold product according to claim <NUM> including applying the mold die according to the first inventive aspect to at least one of a mold cavity and a mold core, to manufacture a mold product.

The present invention implements a fine grain pattern to a mold product with excellent surface quality.

In the following, with reference to the drawings, a description will be given of a mold die, a method of manufacturing the same, an injection molding apparatus, and a method of manufacturing a mold product according to the present embodiment. <FIG> is a front view of a door trim <NUM> which is a mold product. <FIG> is an explanatory illustration of an injection molding apparatus <NUM> which is mainly formed of a mold die <NUM> for the door trim <NUM>.

Firstly, prior to the description of the mold die <NUM> and the method of manufacturing the same, a description will be exemplary given of the door trim <NUM> as an automobile interior component which is a mold product.

The door trim <NUM> covers most of the cabin-side surface of a door trim panel (not shown) for providing decorativeness or any other function. The door trim <NUM> is a mold product obtained by injection molding using general synthetic resin such as polypropylene (PP) resin or ABS resin, and formed to have a predetermined shape.

The door trim <NUM> is provided with a door armrest <NUM> which bulges into the cabin at its intermediate portion in the top-bottom direction. The door armrest <NUM> extends in the front-rear direction so as to allow the passenger to put his/her arm. The door trim <NUM> is further provided with a door pocket <NUM> at a lower position than the door armrest <NUM>. In front of the door pocket <NUM>, a speaker grille <NUM> is provided.

On the surface of the door trim <NUM>, that is, on the motif surface appearing in the cabin, a grain pattern is formed. The grain pattern is transferred by the mold die <NUM> in molding with the mold die <NUM>. The grain pattern forms minor uneven shapes on the motif surface of the door trim <NUM>. Thus, a three-dimensional motif which resembles natural leather is implemented. In this manner, the door trim <NUM> which is a base member being a mold product alone can implement upscale material texture or a sophisticated motif which may be obtained by bonding natural leather as the surface member to the surface of the base member.

Next, a description will be given of the mold die <NUM> and the injection molding apparatus <NUM>. The injection molding apparatus <NUM> is an apparatus that includes the mold die <NUM>, and manufactures a mold product using the mold die <NUM>. The mold die <NUM> is a mold die used in molding a mold product through the injection molding technique, and mainly formed of a mold cavity <NUM> and a mold core <NUM>. By being closed, the mold cavity <NUM> and the mold core <NUM> create a cavity C serving as mold space between them.

In the manufacturing process of the mold product, a mold product is manufactured using the injection molding apparatus <NUM>, that is, the mold die <NUM>. Specifically, after the mold cavity <NUM> and the mold core <NUM> are closed, the cavity C is filled with melted resin through the resin passage formed by a spur <NUM>, a runner <NUM>, a gate <NUM> and the like. When the resin in the cavity C is cooled and solidifies, the mold cavity <NUM> and the mold core <NUM> are open, to deliver the solidified resin mold product from the mold die <NUM>. Thus, the mold product formed to have a predetermined shape is provided.

<FIG> are explanatory illustrations schematically showing the main part of the mold cavity <NUM>. <FIG> is an explanatory illustration schematically showing the main part of the mold cavity <NUM>. <FIG> are each an explanatory illustration showing, in an enlarged manner, the region encircled by an alternate long and short dashed line in <FIG>. Note that, <FIG> does not illustrate a plating layer <NUM> in order to clearly show the shape of the die body <NUM>.

The mold cavity <NUM> is a die in the mold die <NUM> for molding the motif surface of the door trim <NUM>. The mold cavity <NUM> is mainly formed of the die body <NUM>.

The die body <NUM> is formed of metal such as aluminum or any general steel for a mold die. The die body <NUM> has a mold surface <NUM> corresponding to the sculpturing of a mold product. The mold surface <NUM> creates the cavity C with the mold core <NUM> (specifically, the mold surface of the die body <NUM>) when closed (see <FIG>).

The mold surface <NUM> has a leather-grain transfer surface <NUM> for forming a grain pattern formed of a plurality of uneven shapes on the surface of a mold product. The leather-grain transfer surface <NUM> includes a first uneven-shape part <NUM> and a second uneven-shape part <NUM> each having an uneven shape. In the leather-grain transfer surface <NUM>, the width of an uneven shape in the first uneven-shape part <NUM> and that in the second uneven-shape part <NUM> (the distance between the crests in the cross section of the die body <NUM>) fall within a range of <NUM> or more and less than <NUM>.

The first uneven-shape part <NUM> is an uneven shape where an uneven shape width d1 falls within a range of greater than <NUM> and less than <NUM> (as an example in the present embodiment, <NUM> or more and less than <NUM>). The first uneven-shape part <NUM> has a function of transferring a relatively great uneven shape on the surface of the mold product. On the other hand, the second uneven-shape part <NUM> is an uneven shape where an uneven shape width d2 falls within a range of <NUM> or more and smaller than the width d1 of the uneven shape of the first uneven-shape part <NUM> (as an example in the present embodiment, <NUM> or more and less than <NUM>). The second uneven-shape part <NUM> has a function of transferring a smaller uneven shape than the first uneven-shape part <NUM> on the surface of the mold product. The second uneven-shape part <NUM> is formed in every region in the leather-grain transfer surface <NUM> including the surface of one first uneven-shape part <NUM>. By virtue of both the first uneven-shape part <NUM> of a greater uneven shape and the second uneven-shape part <NUM> of a smaller uneven shape existing, the grain pattern transferred onto the surface of a mold product attains a complicated three-dimensional shape. This implements natural authentic texture of natural leather on the surface of the mold product.

As one characteristic of the present embodiment, the mold cavity <NUM> includes the plating layer <NUM> provided at the surface of the die body <NUM> including the mold surface <NUM>. The plating layer <NUM> is an electroless-plating layer formed by electroless plating, and is mainly composed of Ni. The plating layer <NUM> is provided on the surface of the die body <NUM> by a substantially constant thickness. The thickness of the plating layer <NUM> falls within a range of <NUM> or more and less than <NUM>, preferably <NUM> or more and less than <NUM>, and further preferably <NUM> or more and less than <NUM>.

The plating layer <NUM> is smaller in thickness than the uneven shape width d2 of the second uneven-shape part <NUM> which transfers a minor uneven shape. Thus, the plating layer <NUM> is formed on the surface of the uneven shape of the second uneven-shape part <NUM> without burying the uneven shape. Thus, provision of the plating layer <NUM> will not hinder implementing the uneven shape of the second uneven-shape part <NUM>. On the other hand, out of the uneven shapes in the mold surface <NUM>, any uneven shape smaller than the thickness of the plating layer <NUM>, that is, any uneven shape smaller than the second uneven-shape part <NUM> is covered with the plating layer <NUM>. The uneven shape smaller than the second uneven-shape part <NUM> is not the intended uneven shape that contributes to the grain pattern, but corresponds to a defect D that occurs during manufacturing the mold cavity <NUM>. Accordingly, the uneven shape attributed to the first uneven-shape part <NUM> and also the minor uneven shape attributed to the second uneven-shape part <NUM> are implemented and, additionally, the plating layer <NUM> is capable of selectively burying just the defects D at the surface of the mold surface <NUM>, that is, the uneven shapes smaller than the second uneven-shape part <NUM>.

The mold core <NUM> is a die in the mold die <NUM> for molding the back surface of the door trim <NUM> (the surface that faces the door trim panel). The mold core <NUM> is mainly formed of the die body <NUM> which includes the mold surface. Since the mold core <NUM> is for molding the back surface of the door trim <NUM>, its mold surface is not provided with the leather-grain transfer surface. Accordingly, contrary to the mold cavity <NUM>, the mold core <NUM> is not provided with a plating layer. Note that, in view of improved mold product releasability and rust resistance of the mold core <NUM>, the mold core <NUM> may be provided with a predetermined plating layer, for example, a plating layer similar to the plating layer <NUM> of the mold cavity <NUM>.

In the following, a description will be given of a method of manufacturing the mold die <NUM> which is one characteristic of the present embodiment. Specifically, the description will be exemplarily given of a method of manufacturing the mold cavity <NUM> including the leather-grain transfer surface <NUM>. <FIG> is a flowchart of the method of manufacturing the mold die <NUM>.

Firstly, the die body <NUM> that has the mold surface <NUM> corresponding to sculpturing of a mold product is fabricated (S1). The die body <NUM> is fabricated by, for example, subjecting a steel block for a mold die to removing work with a machine tool. The steel block for a mold die may be aluminum or general steel for a mold die.

Next, the leather-grain transfer surface <NUM> is formed at the mold surface <NUM> of the die body <NUM> (S2). The leather-grain transfer surface <NUM> is for forming a grain pattern formed of a plurality of uneven shapes on the surface of the mold product. The forming the leather-grain transfer surface <NUM> is carried out by etching using a chemical agent. The etching mainly includes: a step of masking, with paint or the like, the side surfaces and the bottom surface of the die body <NUM> and any regions in the mold surface <NUM> excluding the leather-grain transfer surface <NUM>; a step of drawing, with acid-resistant ink, a pattern corresponding to the grain pattern in the region of the mold surface <NUM> to be the leather-grain transfer surface <NUM> (hereinafter referred to as "the etching region"); and a step of immersing the die body <NUM> in an acidic solution to corrode the etching region.

In the present embodiment, in the step of forming the leather-grain transfer surface <NUM>, a plurality of etching steps are performed. Specifically, in the first etching step, etching is performed on the surface of the mold surface <NUM>, to form the first uneven-shape part <NUM> of the uneven shape width d1 (for example, in a range of <NUM> or more and less than <NUM>) (S21). Next, in the second etching step, etching is performed on the surface of the mold surface <NUM> having undergone the first etching step, to form the second uneven-shape part <NUM> of the uneven shape width d2 (for example, in a range of <NUM> or more and less than <NUM>) (S22).

The leather-grain transfer surface <NUM> according to the present embodiment includes the first uneven-shape part <NUM> which has a relatively great uneven shape and the second uneven-shape part <NUM> which has a minor uneven shape in a range including the surface of the first uneven-shape part <NUM>. Accordingly, the etching is performed twice respectively for the uneven-shape parts <NUM>, <NUM>. Here, when a plurality of (three or more) uneven-shape parts differing in the width of the uneven shape are designed, the number of etching steps are set according to the number of the designed uneven-shape parts. Therefore, the etching is performed not necessarily twice. In forming the two uneven-shape parts <NUM>, <NUM> according to the present embodiment, the etching may be performed twice or more for each of the uneven-shape parts <NUM>, <NUM>.

When the leather-grain transfer surface <NUM> is formed, next, the plating layer <NUM> is formed on the die body <NUM> including the mold surface <NUM> (S3). The forming the plating layer <NUM> is carried out by electroless plating. The electroless plating may be electroless Ni-P plating, electroless Ni-B plating, electroless Ni-P-PTFE composite plating, electroless Ni-P-B plating or the like.

Specifically, the die body <NUM> is immersed in a plating bath filled with electroless plating liquid. On the surface of the die body <NUM>, the plating layer <NUM> mainly composed of Ni (nickel) is deposited by the electroless plating. The thickness of the plating layer <NUM> can be controlled by changing the immersion time in the plating bath. Through the immersion time, the plating layer <NUM> is formed to have a thickness falling within a range of <NUM> or more and less than <NUM> (preferably a range of <NUM> or more and less than <NUM>, further preferably a range of <NUM> or more and less than <NUM>). The die body <NUM> having immersed for a predetermined immersion time is taken out from the plating bath.

Through the foregoing steps, the mold cavity <NUM> which includes the die body <NUM> with the leather-grain transfer surface <NUM> and provided with the plating layer <NUM> is manufactured.

The plating layer <NUM> is formed on the surface of the second uneven-shape part <NUM> without burying the uneven shape. Thus, provision of the plating layer <NUM> will not hinder implementing the uneven shape of the second uneven-shape part <NUM> in the leather-grain transfer surface <NUM>.

Meanwhile, in order to implement a grain pattern on the surface of the mold product, the etching is performed on the die body <NUM>. Here, on the mold surface <NUM>, uneven shapes smaller than the second uneven-shape part <NUM>, that is, defects D associated with the etching occur. Particularly, in the case where the second uneven-shape part <NUM> smaller than the first uneven-shape part <NUM> is formed for implementing the grain pattern of the natural texture, a plurality of steps of etching must be performed. This increases the total etching time during which the die body <NUM> is exposed to the etching solution, contributing to occurrence of the defects D at the mold surface <NUM>.

In this regard, since the thickness of the plating layer <NUM> is designed to fall within a range of <NUM> or more and less than <NUM>, any uneven shape smaller than the second uneven-shape part <NUM> is covered with the plating layer <NUM>. Accordingly, the uneven shape attributed to the first uneven-shape part <NUM> and also the minor uneven shape attributed to the second uneven-shape part <NUM> are implemented and, additionally, just the uneven shapes (defects D) on the mold surface <NUM> smaller than the second uneven-shape part <NUM> are selectively buried.

In the following, a description will be given of a scheme as a comparative example against the scheme of the plating layer <NUM> obtained by the electroless plating according to the present embodiment. The scheme of removing minor defects D occurring at the mold surface <NUM> may be: (<NUM>) forming an electrolytic-plating layer on the mold surface <NUM> by electroplating; (<NUM>) forming a synthetic resin layer on the mold surface <NUM> by blasting synthetic resin; or (<NUM>) smoothing the mold surface <NUM> by shot blasting.

Firstly, the scheme of electroplating has an aspect not applicable to a mold product such as an automobile interior component like the door trim <NUM>. With a mold die for molding a mold product with complicated sculpturing such as an automobile interior component, charges are locally set at a particular site attributed to the shape, adversely resulting in variations in the amount of metal deposition. Thus, the thickness is not properly controlled and the minor uneven shape of the second uneven-shape part <NUM> is not implemented.

The scheme of forming a synthetic resin layer is not suitable for a mold die for mass production of an automobile interior component for its being low in wear resistance and scratch resistance. The scheme of blasting synthetic resin is unlikely to attain thickness control and fails to implement the minor uneven shape of the second uneven-shape part <NUM>. Furthermore, its being low in chemical resistance limits the type of chemicals for maintaining the mold die, which means, the scheme is disadvantageous in terms of maintainability.

The scheme of shot blasting is incapable of completely removing unwanted defects D. Accordingly, burrs may occur at the surface of the mold product. Furthermore, particles may disadvantageously crush not only the defects D but also the second uneven-shape part <NUM>, and the desired fine grain pattern may not be implemented.

In this regard, in the mold cavity <NUM> according to the present embodiment, the plating layer <NUM> selectively buries just the uneven shapes (defects D) smaller than the second uneven-shape part <NUM> in the surface of the mold surface <NUM>. Thus, the uneven shape attributed to the first uneven-shape part <NUM> and also the minor uneven shape attributed to the second uneven-shape part <NUM> remain in the mold surface <NUM>.

In particular, the plating layer <NUM> obtained by electroless plating is free from thickness variations due to the shape of the mold die, contrary to a plating layer obtained by electroplating. As a result, provision of the plating layer <NUM> will not hinder properly implementing the uneven shape of the second uneven-shape part <NUM> in the leather-grain transfer surface <NUM>.

By virtue of containing Ni as a main component, the plating layer <NUM> is excellent in wear resistance and scratch resistance. Accordingly, the present embodiment is suitable for a mold die for mass production of an automobile interior component.

By virtue of the plating layer <NUM> being formed over the entire mold surface <NUM>, no defects D will remain. Since the electroless plating is not the scheme of crushing the uneven shape, the uneven shape of the second uneven-shape part <NUM> will not be crushed.

Thus, in the mold cavity <NUM> according to the present embodiment, since minor defects D are not exposed at the surface of the mold surface <NUM>, the mold cavity <NUM> is free from any defects D filled with resin. As a result, the present embodiment minimizes the occurrence of the phenomenon that the surface of the mold product is minutely torn (occurrence of burrs). Thus, the fine grain pattern is implemented on the mold product with excellent surface quality.

When the thickness of the plating layer <NUM> is <NUM> or more, the uneven shape of the leather-grain transfer surface <NUM> is also smoothed. This tends to increase gloss (shine) on the surface of the mold product. The increased gloss disadvantageously lets the resin material texture to become apparent against the natural leather texture. In this regard, the present embodiment sets the thickness of the plating layer <NUM> to fall within a range of <NUM> or more and less than <NUM>. Accordingly, the uneven shape attributed to the first uneven-shape part <NUM> and the minor uneven shape attributed to the second uneven-shape part <NUM> remain on the mold surface <NUM>. This minimizes gloss on the surface of the mold product. As a result, the natural authentic texture of natural leather is implemented on the mold product.

In the present embodiment, just the minor defects D at the surface of the mold surface <NUM> are selectively buried. This implements the desired grain pattern on the mold product with excellent surface quality.

In the present embodiment, the electroless plating is provided over the entire mold cavity <NUM>. This improves rust resistance and soil resistance of the mold cavity <NUM>. Additionally, the high hardness of the electroless plating improves wear resistance. This contributes to increasing the life of the mold cavity <NUM>.

In the following, a specific description will be given of the effect of the mold cavity <NUM> according to the present embodiment. A mold product molded using the mold cavity <NUM> must present a fine grain pattern and also be excellent in surface quality. One factor of poor surface quality of the mold product is the state called "whitening" in which the surface of the mold product appears whitish and cloudy. As a result of an extensive study on the whitening, it has been found that the factor of the whitening includes two totally different phenomena, namely, "scuffs" and "burrs".

<FIG> are explanatory illustrations of scuffs. <FIG> is a photograph showing a surface S1 of a mold product in an enlarged manner. <FIG> is an explanatory illustration schematically showing the surface S1 of the mold product. The scuffs refer to traces with directivity which appear on the surface S1 of the mold surface. The scuffs diffusing light makes whitening visible. Since the scuffs are traces with directivity, the whitening is clearly visible when the surface S1 of the mold product is observed from a specific direction.

As a result of a study on the occurrence mechanism of scuffs, it was concluded that the scuffs are attributed to rubbing between the surface S1 of the mold product and the uneven shape parts <NUM>, <NUM> of the leather-grain transfer surface <NUM>. That is, when being released from the mold die, the surface S1 of the mold product and the surfaces of the uneven shape parts <NUM>, <NUM> of the leather-grain transfer surface <NUM> may be rubbed against each other. Furthermore, the resin in the cavity C contracts when cooled. This may also cause the surface S1 of the mold product and the surfaces of the uneven shape parts <NUM>, <NUM> of the leather-grain transfer surface <NUM> of the mold cavity <NUM> to rub against each other. Because of the rubbing, the traces with directivity occur.

<FIG> are explanatory illustrations of burrs. <FIG> is a photograph of a surface S2 of the mold product in an enlarged manner. <FIG> is an explanatory illustration schematically showing the surface S2 of the mold product. The burrs refer to clusters of burred surface of S2 of the mold product. The burrs diffusing light makes whitening visible.

<FIG> are explanatory illustrations of occurrence mechanism of burrs. As a result of a study on the occurrence mechanism of burrs, it has been concluded that the burrs are caused by corrosion of etching. That is, corrosion of etching forms minor uneven shapes not as great as the second uneven-shape part <NUM>. That is, the defects D occur at the surface of the mold cavity <NUM> (<FIG>). When the defects D are filled with resin in injection molding (<FIG>), when being released from the mold die, the resin in the defects D is not smoothly released depending on the removing direction of the mold die (<FIG>). As a result, the resin is pulled and the surface of the mold product is minutely torn, that is, burrs occur.

In support of the mechanism, it has also been found that a longer etching time increases burrs. As described above, in order to implement a fine grain pattern, a plurality of steps of etching must be performed in manufacturing the mold cavity <NUM>. This increases the total etching time during which the die body <NUM> is exposed to the chemical solution, contributing to occurrence of the defects D at the mold surface <NUM>. Thus, as a finer grain pattern is implemented on the mold product, whitening because of burrs becomes increasingly apparent.

There is a conventionally known method of providing a plating layer on the surface of the mold die in order to prevent scuffs. The plating layer for preventing scuffs functions to improve releasability and minimize rubbing against the mold die. From this viewpoint, the plating layer with a greater thickness exhibits the effect against scuffs.

On the other hand, the plating layer <NUM> according to the present embodiment functions to bury the defects D which cause burrs. In the mold cavity <NUM> having undergone etching, the second uneven-shape part <NUM> for transferring a fine grain pattern and the defects D smaller than the second uneven-shape part <NUM> both exist. Here, setting the thickness of the plating layer <NUM> to fall within a range of <NUM> or more and less than <NUM>, just the defects D are selectively covered. That is, just the defects D at the surface of the mold surface <NUM> are selectively buried and the uneven shape attributed to the first uneven-shape part <NUM> and also the minor uneven shape attributed to the second uneven-shape part <NUM> are implemented. As a result, a fine grain pattern is implemented, and excellent surface quality free from the whitening due to burrs is provided. The provision of the plating layer <NUM> improves the releasability and, as a matter of course, also prevents whitening due to scuffs.

As a result of a further study on the thickness of the plating layer <NUM>, it has been found that the further suitable condition is, as shown in <FIG>, a thickness <NUM>% as great as a width d3 of a defect D (d3/<NUM>). With this thickness of about <NUM>%, in the surface where the second uneven-shape part <NUM> and the defects D smaller than the second uneven-shape part <NUM> both exist, the defects D are properly buried while the uneven shape of the second uneven-shape part <NUM> is kept.

In the present embodiment which is predicated on a fine leather grain, the minimum value of the width d2 of the second uneven-shape part <NUM> is <NUM>. Accordingly, the width d3 of the defect D is less than <NUM>. Therefore, the thickness of the plating layer <NUM> is preferably less than <NUM>. On the other hand, when a plating layer having a thickness falling within a range of <NUM> or more and less than <NUM> was provided, no whitening was visible while burrs occurred. In view of the foregoing, while it has been noted that the thickness of the plating layer <NUM> should fall within a range of <NUM> or more and less than <NUM>, the thickness preferably falls within a range of <NUM> or more and less than <NUM>, and further preferably falls within a range of <NUM> or more and less than <NUM>.

In the following, a description will be given of a specific example of the mold cavity <NUM> according to the present embodiment. <FIG> is an explanatory illustration showing the correlation between the gloss value of the mold cavity and the gloss value of the mold product. The gloss value is a numerical value representing gloss (shine). As the value is greater, gloss is great.

In <FIG>, data represented by squares is a plot of correlation between the gloss value of the mold cavity <NUM> according to the present example and the gloss value of the mold product molded using the mold cavity <NUM>. Specifically, a plurality of mold cavities <NUM> of different gloss values were fabricated, with the plating layer <NUM> having a thickness selected from a range of <NUM> or more and less than <NUM> (for example, <NUM>). The correlation was obtained using a glossmeter configured to measure the gloss value of the mold cavity <NUM> and that of the mold product under the condition of an identical incident or exit angle of <NUM>°. Line L1 is a line approximating the plot data. Note that, the measuring method is not limited to the foregoing.

On the other hand, data represented by rhombuses is a plot of correlation between the gloss value of the mold cavity and the gloss value of the mold product molded using the mold cavity. Specifically, a plurality of mold cavities <NUM> of different gloss values were fabricated, with no plating layer and without having their surfaces treated by sand blasting. The correlation was obtained using a glossmeter configured to measure the gloss value of the mold cavity and that of the mold product under the condition of an identical incident or exit angle of <NUM>°. Line L2 is a line approximating the plot data. Note that, the measuring method is not limited to the foregoing.

As shown in <FIG>, line L1 representing the correlation between the gloss value of the mold cavity <NUM> according to the present example and the gloss value of the mold product is inclined milder than line L2 representing the correlation between the gloss value of the mold cavity having undergone sand blasting and the gloss value of the mold product.

Here, for example, it is assumed that the target gloss value demanded of the mold product in view of the specification as a final product falls within a range of <NUM> to <NUM>. The mold cavity <NUM> according to the present example is capable of providing a mold product of a target gloss value range, when the gloss value of the mold cavity <NUM> falls within a range of about <NUM> to <NUM>. On the other hand, the mold cavity having undergone sand blasting is capable of providing a mold product of a target gloss value range, when the gloss value of the mold cavity falls within a range of about <NUM> to <NUM>. Thus, the mold cavity <NUM> according to the present example allows a wider gloss value range for the target gloss value of the mold product as compared to the mold cavity having undergone sand blasting. The characteristic shown in <FIG> is obtained with the plating layer <NUM> of other thickness selected from a range of <NUM> or more and less than <NUM>.

This difference from the comparison example is achieved by the provision of the plating layer <NUM> of a predetermined thickness selected from a range of <NUM> or more and less than <NUM> to the mold cavity <NUM>, which plating layer <NUM> selectively buries the defects D (the uneven shapes smaller than the second uneven-shape part <NUM>) at the surface of the mold surface <NUM> while leaving the uneven shape of the first uneven-shape part <NUM> and that of the second uneven-shape part <NUM>. That is, by virtue of the plating layer <NUM> burying the minor defects D at the surface of the mold surface <NUM>, the gloss value of the mold product corresponding to the mold cavity <NUM> with a low gloss value improves (increases). On the other hand, since the first uneven-shape part <NUM> and the second uneven-shape part <NUM> are not buried by the plating layer <NUM>, the gloss value of the mold product corresponding to the mold cavity <NUM> with a high gloss value is maintained. Accordingly, as described above, line L1 representing the correlation between the gloss value of the mold cavity <NUM> according to the present example and the gloss value of the mold product tends to be inclined milder than line L2 representing the correlation between the gloss value of the mold cavity having undergone sand blasting and the gloss value of the mold product.

It is demonstrated that the mold cavity <NUM> according to the present example, the plating layer <NUM> falling within a range of <NUM> or more and less than <NUM> provides the desired gloss value and that whitening due to burrs is minimized.

Additionally, the mold cavity <NUM> according to the present example is capable of attaining the target gloss value for the mold product with the mold cavity <NUM> of gloss values managed in a wider range. While the mold cavity <NUM> is manufactured to attain a target gloss value corresponding to the target gloss value of the mold product, the gloss value of the manufactured mold cavity <NUM> may vary to some extent. However, since provision of the plating layer <NUM> permits a wider management range for the mold cavity <NUM>, the gloss value of the mold product can be easily adjusted.

Note that, the description has been given of the example of <FIG> in which the thickness of the plating layer <NUM> falls within a range of <NUM> or more and less than <NUM>. Here, the characteristic similar to the correlation between the gloss value of the mold cavity <NUM> according to the example and the gloss value of the mold product is provided also with the plating layer <NUM> having a thickness falling within a range of <NUM> or more and less than <NUM> and a range of <NUM> or more and less than <NUM>. That is, the mold cavity <NUM> provided with plating layer <NUM> by a thickness falling within a range of <NUM> or more and less than <NUM> provides a mildly inclined line of correlation between the gloss value of the mold cavity <NUM> and the gloss value of the mold product. Thus, the mold cavity <NUM> provided with the plating layer <NUM> by a thickness falling within a range of <NUM> or more and less than <NUM>, which is a wider gloss value management range for the mold cavity <NUM>, is capable of attaining the target gloss value for the mold product. The widened management range for the mold cavity <NUM> facilitates adjusting the gloss value of the mold cavity <NUM>.

Note that, when the thickness of the plating layer <NUM> is <NUM> or more, not only the minor defects D at the surface of the mold surface <NUM> but also the first uneven-shape part <NUM> and the second uneven-shape part <NUM> at the leather-grain transfer surface <NUM> are buried according to the thickness of the plating layer <NUM>, and smoothed. Therefore, it is considered that the surface of the mold surface <NUM> of the mold cavity <NUM> approximates the mirror surface (the gloss value thereof increases) and the gloss value of the mold product less varies. That is, the correlation (line) between the gloss value of the mold cavity <NUM> and the gloss value of the mold product becomes further mildly inclined to approximate a substantially horizontal line, and shifts upward (toward higher gloss values). As a result, while the line shows mild inclination, the range of the target gloss value as a final products is exceeded.

The foregoing is the description of the mold die and the method of manufacturing the mold die according to the present embodiment. The present invention is not limited to the embodiment, and various changes may be made within the scope of the invention.

For example, in the above-described embodiment, on the premise that a grain pattern is formed on one side surface of a mold product, the description has been given of the mold die as to an exemplary mold cavity. On the other hand, in the case where the grain pattern is to be formed by a mold core, the scheme of the present embodiment may be applied to the mold core or both of the mold cavity and the mold core.

While the door trim has been exemplary described as the mold product molded by the mold die, the present invention is applicable to a mold die for molding various types of automobile interior components such as a rear side trim, a roof trim, a pillar garnish, or a roof rail garnish.

In the present embodiment, the texture of natural leather is implemented by a grain pattern. Here, various types of appearance besides natural leather can be implemented by the grain pattern formed of minor uneven shapes.

An injection molding apparatus including the mold die, and a method of manufacturing a mold product in which the mold die is at least one of a mold cavity and a mold core also hold as part of the present invention.

In the present embodiment, the thickness of the whole plating layer falls within a range of <NUM> or more and less than <NUM>. On the other hand, the thickness of at least part of the plating layer falling within a range of <NUM> or more and less than <NUM> will suffice. That is, in the plating layer, a region having a thickness falling within a range of <NUM> or more and less than <NUM> may be selectively provided. "The thickness of the whole plating layer falling within a range of <NUM> or more and less than <NUM>" does not intend to exclude partially including a region where the thickness is <NUM> or more due to manufacture variations in forming the plating layer (the recitation means that at least part of the plating layer has a thickness falling within a range of <NUM> or more and less than <NUM>).

Claim 1:
A mold die (<NUM>) comprising:
a die body (<NUM>, <NUM>) including a mold surface (<NUM>) having a shape corresponding to sculpturing of a mold product; and
a plating layer (<NUM>) provided on a surface of the mold surface (<NUM>), wherein
the mold surface (<NUM>) has a leather-grain transfer surface (<NUM>) for forming, at a surface of the mold product, a grain pattern formed of a plurality of uneven shapes,
the leather-grain transfer (<NUM>) surface includes at least a first uneven-shape part (<NUM>) and a second uneven-shape part (<NUM>) formed at a surface of the first uneven-shape part (<NUM>) and smaller in an uneven-shape width than the first uneven-shape part (<NUM>), the uneven-shape width in the first uneven-shape part (<NUM>) and the uneven-shape width in the second uneven-shape part (<NUM>) each falling within a range of <NUM> or more and less than <NUM>,
the plating layer (<NUM>) is an electroless-plating layer, and
a thickness of at least part of the plating layer (<NUM>) falls within a range of <NUM> or more and less than <NUM>,
the first uneven-shape part (<NUM>) has a first uneven-shape width d1 falling within a range of <NUM> or more and less than <NUM>, and
the second uneven-shape (<NUM>) part has a second uneven-shape width d2 falling within a range of <NUM> or more and less than <NUM>.