JP7798505B2 - Resin molded product and its manufacturing method - Google Patents

Description

This disclosure relates to a resin molded product, a manufacturing method thereof, and a manufacturing method of a mold.

Traditionally, ceramics have been used for sanitary ware and tableware used in toilets and washrooms. In recent years, these molded products have also been supplied in synthetic resin, which is lightweight, shatter-resistant, inexpensive, and suitable for mass production.

Patent Document 1 proposes a method for manufacturing synthetic resin tableware using a mold created based on three-dimensional shape data of a ceramic work. Patent Document 1 also discloses that, to achieve an appearance and texture similar to that of ceramics, the inner surface of the mold is embossed by etching or sandblasting, and that different colored particles are added to the synthetic resin material.

JP 2014-180474 A

By applying a texturing process as described in Patent Document 1, it is possible to obtain an appearance and texture that is somewhat closer to ceramic than a resin molded product made of a synthetic resin with a flat surface. However, Patent Document 1 does not consider what type of texturing process should be used, and there are significant differences in appearance and texture between ceramic and resin molded products that can be manufactured using the information in this document.

The purpose of this disclosure is to provide a resin molded product that has little difference in appearance or texture from ceramic, a manufacturing method for the same, and a manufacturing method for a mold.

In order to achieve the above object, a resin molded article according to one embodiment of the present disclosure has a ceramic-like surface that satisfies all of the following formulas 1, 2, and 3 on part or all of its surface.
Wb>Wc...Formula 1
Wb>Wd...Formula 2
21≦Wb≦60...Formula 3
Here, Wb, Wc, and Wd are values obtained by classifying the reflection profile of laser light incident at an angle of 60° into the following wavelength ranges.
Wb: Wavelength 0.3 mm or more and 1 mm or less Wc: Wavelength 1 mm or more and 3 mm or less Wd: Wavelength 3 mm or more and 10 mm or less

[Resin molded products]
A resin molded product according to one embodiment of the present disclosure has a ceramic-like surface. A ceramic-like surface is a surface having an appearance and texture similar to the surface of ceramic. The resin molded product of this embodiment may have a ceramic-like surface on a portion of its surface, or may have a ceramic-like surface on the entire surface. Either a portion of the surface or the entire surface may be a ceramic-like surface.

The reflection profile of a porcelain-look surface, measured at a 60° angle, can be identified by values classified by wavelength range. The reflection profile of a 60° incident laser beam is an optical profile obtained by irradiating the target surface with a laser beam at an angle of 60° from the normal to the surface and measuring the reflected light at the same angle in the opposite direction, while repeatedly moving the point source of the laser beam at specified intervals.

The reflectance profile is classified from short wavelength to long wavelength range using a filter function transformation. The classified values are represented by the symbols Wa, Wb, Wc, and Wd according to the wavelength range, as shown below.

Wa: Wavelength 0.1 mm or more and 0.3 mm or less Wb: Wavelength 0.3 mm or more and 1 mm or less Wc: Wavelength 1 mm or more and 3 mm or less Wd: Wavelength 3 mm or more and 10 mm or less

To measure Wa, Wb, Wc, and Wd, a MICRO-WAVE-SCAN (registered trademark) manufactured by BYK Gardner (Germany) is used. This device is known for its ability to optically measure the light/dark wavelength patterns of the target surface, much like the human eye, and analyze the surface structure.

The ceramic-like surface of the resin molded product satisfies all of the following formulas 1, 2, and 3.
Wb>Wc...Formula 1
Wb>Wd...Formula 2
21≦Wb≦60...Formula 3

By satisfying all of the above formulas 1 to 3, the ceramic-like surface of a resin molded product has an appearance and texture similar to that of ceramic. Resin molded products have the same luxurious feel as ceramic. When used in combination with ceramic products, a sense of unity is achieved.

It is preferable that the ceramic-like surface further satisfies the following formula 4.
12≦Wc≦51...Formula 4

It is preferable that the ceramic-like surface further satisfies the following formula 5.
16≦Wd≦50...Formula 5

It is preferable that the ceramic-like surface further satisfies the following formula 6.
Wb>Wa Equation 6

It is preferable that the ceramic-like surface further satisfies the following formula 7.
32≦Wb≦60...Formula 7

It is preferable that the ceramic-like surface further satisfies the following formula 8.
30≦Wc≦51...Formula 8

It is preferable that the ceramic-like surface further satisfies the following formula 9.
28≦Wd≦50...Formula 9

Resin molded products can be used, for example, as replacements for sanitary ware such as toilet side panels, toilet body covers, toilet lids, and toilet seats, as well as tableware.

[Method of manufacturing mold]
A method for manufacturing a mold according to an embodiment of the present disclosure is a method for manufacturing a mold for obtaining a resin molded product. The method for manufacturing a mold involves laser processing the surface of a metal material and then etching it to form a wavy surface. The wavy surface is a surface that is transferred to a synthetic resin material to form a ceramic-like surface. In other words, the surface of the metal material that forms the wavy surface is the part of the resulting mold that corresponds to the ceramic-like surface of the resin molded product. The surface structure of the wavy surface corresponds to the surface structure of the ceramic-like surface. It is preferable to use a metal material in which the basic shape of the mold is already completed, except that the wavy surface is not formed.

When laser processing, a data pattern is created in advance, and the surface of the metal material on which the undulating surface is to be formed is micro-machined using a laser in accordance with this data pattern. The depth of the micro-indentations formed on the surface of the metal material by laser processing is preferably 6 μm or more and 10 μm or less. By setting the depth of the micro-indentations within this preferred range, it is easy to form a undulating surface with a surface structure corresponding to a ceramic-like surface. There are no particular limitations on the arrangement of the micro-indentations. For example, they can be arranged randomly.

With current laser processing technology, it is difficult to form perfectly smooth micro-recesses using laser processing alone. To form a wavy surface with a surface structure that corresponds to a ceramic-like finish, further etching is required. In addition to etching, a blasting process such as sandblasting may be performed. In this case, there is no particular restriction on the order in which the etching and blasting processes are performed. Etching and blasting may each be performed independently, multiple times. Furthermore, polishing using a brush or buff may also be performed.

[Method of manufacturing resin molded products]
A method for manufacturing a resin molded product according to one embodiment of the present disclosure is a method for forming the ceramic-like surface by obtaining a mold by the above-described mold manufacturing method and transferring the undulated surface of the obtained mold to a synthetic resin material. When manufacturing the mold, if a metal material in which the basic shape of the mold is already completed except for the fact that the undulated surface is not formed is used, the obtained mold can be used to form the ceramic-like surface while also forming the basic shape of the resin molded product.

The present disclosure will be explained in more detail below using examples and comparative examples. The present disclosure is not limited to the following examples. In the following examples, Examples 1 to 5 and Examples 15 to 17 are comparative examples, and Examples 6 to 14 are working examples.

[Examples 1 to 14]
A pre-hardened steel plate measuring 8 cm in length, 12 cm in width, and 20 mm in thickness was used as the metal material. One surface of this plate was laser processed using a 5-axis laser processing machine manufactured by GF Machining Solutions, to create fine recesses with a maximum depth shown in Table 1, randomly arranged at a pitch of 5 to 20 mm in both the length and width directions. After laser processing, the metal material was subjected to etching and sandblasting, and finally polished with a metal brush and buff to obtain the resin molded product of each example.

[Examples 15 to 17]
In Examples 15 and 16, commercially available PP (abbreviation for polypropylene) resin side panels were used as the resin molded articles, and in Example 17, a commercially available ABS (abbreviation for acrylonitrile-butadiene-styrene copolymer) flat plate was used.

[Surface structure measurement]
For Examples 1 to 14, the surfaces subjected to laser processing or the like, and for Examples 15 to 17, the surfaces shown in the tables were measured using a MICRO-WAVE-SCAN (registered trademark) AW-4824 manufactured by BYK Japan Co., Ltd. and BYK Gardner (Germany), to determine Wa, Wb, Wc, and Wd. The results are shown in Table 1.

[Appearance evaluation]
Ten resin molded articles of each example, labeled A to J, were prepared, and the appearance of each was evaluated by 10 panelists according to the following criteria, with the average being calculated. The results are shown in Table 2. A rating of 3.3 or higher can be said to indicate a desirable ceramic-like surface. As shown in Table 2, Examples 6 to 14 received high ratings for appearance.

(Evaluation criteria)
1: The surface is not wavy and looks like resin.
2: The surface is not wavy and looks like resin.
3: Visible undulations on the surface.
4: The undulations on the surface look similar to ceramic.
5: The undulations on the surface look similar to those of ceramic.

Claims (8)

A resin molded article having a ceramic-like surface that satisfies all of the following formulas 1, 2, and 3 on at least a portion of its surface (excluding the surface of the film and the surface of the coating film).
Wb>Wc...Formula 1
Wb>Wd...Formula 2
21≦Wb≦60...Formula 3
Here, Wb, Wc, and Wd are values obtained by classifying the reflection profile of laser light incident at an angle of 60° into the following wavelength ranges.
Wb: Wavelength 0.3 mm or more and 1 mm or less Wc: Wavelength 1 mm or more and 3 mm or less Wd: Wavelength 3 mm or more and 10 mm or less The resin molded product according to claim 1, wherein the ceramic-like surface further satisfies the following formula 4.
12≦Wc≦51...Formula 4
However, Wc is the same as Wc in claim 1. The resin molded product according to claim 1 or 2, wherein the ceramic-like surface further satisfies the following formula 5.
16≦Wd≦50...Formula 5
However, Wd is the same as Wd in claim 1. The resin molded product according to any one of claims 1 to 3, wherein the ceramic-like surface further satisfies the following formula 6.
Wb>Wa Equation 6
Here, Wa is a value obtained by classifying the reflection profile of laser light incident at an angle of 60° into the following wavelength ranges, and Wb is the same as Wb in claim 1.
Wa: Wavelength 0.1 mm or more and 0.3 mm or less The resin molded product according to any one of claims 1 to 4, wherein the ceramic-like surface further satisfies the following formula 7.
32≦Wb≦60...Formula 7
However, Wb is the same as Wb in claim 1. The resin molded product according to any one of claims 1 to 5, wherein the ceramic-like surface further satisfies the following formula 8.
30≦Wc≦51...Formula 8
However, Wc is the same as Wc in claim 1. The resin molded product according to any one of claims 1 to 6, wherein the ceramic-like surface further satisfies the following formula 9.
28≦Wd≦50...Formula 9
However, Wd is the same as Wd in claim 1. A method for manufacturing a resin molded product according to any one of claims 1 to 7, comprising: laser processing the surface of a metal material; and then etching the surface to form a wavy surface, thereby obtaining a mold; and transferring the wavy surface of the mold to a synthetic resin material, thereby forming the ceramic-like surface.