JPH0280212A - Plastic molding mold - Google Patents

Abstract

PURPOSE:To manufacture a molding mold with an excellent mold releasing property and defoamability in less expensive by giving an emboss configuration to anti-soluble plastics having specific value or less in its soluble parameter and specific value or more in its elongation in the breaking point. CONSTITUTION:Olefin or fluoro resin such as polymethylpentene, polyethylene, polypropylene or the like can be used as anti-soluble plastics. Since the solubility parameter delta of high polymer to be a lens sheet material is in the region of 9.0-10.0, should the high polymer having solubility parameter delta of 8.0 or less be employed as high polymer to be a molding mold material, it may be preferable in its mold release. A flexible material is not susceptible to be damaged in its sheet upon releasing the molded sheet from the molding mold, therefore, the flexibility is provided. In consideration of the breakage of ionizing radiation curing resin or mold releasing failure, it is desirable that the elongation of a breaking point is 70% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a plastic mold suitable for molding a lens sheet or the like using an ionizing radiation-cured resin.

[Prior art] In order to mold plastic lens sheets used for rear projection screens, etc., ultraviolet (UV)
Ionizing radiation polymerization methods are known in which resins are cured by irradiating them with ionizing radiation such as electron beams (EB) or electron beams (EB).

First, molding of a lens sheet using the ionizing radiation polymerization method will be briefly explained.

FIGS. 1 and 2 are diagrams for explaining the process of molding a lens sheet, the molds used therein, and the problems involved.

In FIG. 1, 1 is a mold, and 2 is a UV curing resin.

Mold 1 is made of copper that can be mirror-finished with natural diamonds.
Embossed shapes were used in metals such as copper alloys, aluminum, or nickel. In this mold 1, a minute reverse taper portion 1a is formed at the tip of the embossing (FIG. 1(a)).

The reason for this is considering the machinability of the mold 1, the chipping of the cutting tool 4, etc., and especially when using metals such as copper or aluminum as mentioned above as the material of the mold 1, the material itself Because the material is soft, when cutting with the hide 4, the material is pushed by the cutting tool 4, and force F is applied to the tip of the embossing, causing shape deformation (Figure 2).This deformation occurs at the tip of the mold 1, which has a fine shape. It occurs noticeably in

After coating the mold 1 with a UV curing resin 2 and curing the UV curing resin 2 using a U light source (Fig. 1 (b)
) A lens sheet 3 is obtained by releasing the mold (FIG. 1(C)).

[Problem to be solved by the invention]

In the conventional metal molding die 1 described above, upon demolding,
There was a problem in that the tip 3a of the lens sheet 3 broke and remained inside the embossing, making the mold 1 unusable (
Figure 1 (C)).

Furthermore, if the mold 1 is made of metal, curing will be inhibited on the metal surface, and usable UV-curable resins will be limited.

Furthermore, the wettability between the metal surface of the mold 1 and the UV-cured resin 2 is poor, and bubbles remain after curing, which is unfavorable both in appearance and optically.

Furthermore, when the UV cured resin 2 contracts during curing, the mold 1 does not bend to follow the contraction, so the molded lens sheet 3 bites into the mold 1. As a result, it becomes difficult to release the lens sheet 3 from the mold, resulting in defective mold release in which the lens sheet 3 partially becomes white.

On the other hand, the metal mold 1 is expensive and has the problem of increasing the manufacturing cost of the lens sheet 3.

Some plastic molding molds have been proposed (Japanese Unexamined Patent Publication No. 61-114232), but these molds cannot solve the above-mentioned problems simply because they are flexible.

The purpose of the present invention is not to limit the usable ionizing radiation-cured resin, but also to improve its mold releasability with the ionizing radiation-cured resin.
To provide a plastic mold that has good defoaming properties and can be manufactured at low cost.

[Means to solve the problem]

In order to solve the above problems, a plastic mold according to the present invention is a plastic mold for molding a sheet having a fine embossed shape using an ionizing radiation-cured resin, and has a solubility parameter of 8.0 or less and a The structure is made of a solvent-resistant plastic with an elongation of 70% or more and an embossed shape.

The ionizing radiation curing resin includes UV curing resin, EB
Cured resins and the like can be used, and specifically, resins such as urethane acrylate, epoxy acrylate, polyester acrylate, aliphatic acrylate, aromatic acrylate, etc. can be used. Most of these solubility parameters are in the range δ=9.0 to 10.0.

As the solvent-resistant plastic, olefins such as polymethylpentene, polyethylene, polypropylene, or fluorine resins can be used.

Solubility Paran
+eter: expressed as δ) means - In boat fishing, it is a value that is an indicator of the solubility of a certain polymer in a solvent, the ease with which it mixes with other polymers, and the ease with which it adheres, that is, the strength of the bond between molecules. means.

In this invention, the value is particularly used as an index of the degree of releasability between the polymer used as the material for the mold and the polymer used as the material for the lens sheet.

Specifically, as mentioned above, the solubility parameter δ of the polymer used as the material of the lens sheet is about 9.0 to 10.0, so the solubility parameter δ of the polymer used as the material of the mold is 8.0. It was concluded that mold releasability is good if the following materials are used.

Next, the elongation of plastic at the breaking point will be explained. When a tensile load is applied to a polymeric material, slippage occurs between the molecules, causing a phenomenon called flow, causing the polymer to stretch and eventually break. At this time, the ratio of the original length to the stretched length is called the elongation at the break point.

In this invention, since a flexible material is less likely to cause damage to the sheet when it is released from a mold, this flexibility is used as an index to define the flexibility.

Specifically, we concluded that it is desirable for the elongation at the break point to be 70% or more, taking into account folding of the ionizing radiation-cured resin at the tip of the embossing on the mold, poor mold release, etc. Ta.

〔Example〕

Next, the present invention will be described in detail with reference to Examples.

A Fresnel lens-shaped emboss was cut into a copper plate 1 m wide and 2 mm thick, and this was used as a matrix to make polymethylpentene (δζ 7.5. Elongation at break point - 85%).
was hot pressed to produce a polymethylpentene mold.

An embossed Fresnel lens matrix was cut into a board of ultra-high molecular weight polyethylene (δ# 7.9, elongation at break -90%) that was 1 m wide and 1 m wide with a thickness of 5 mm. A polymer polyethylene mold was made.

Using each of the above molds, urethane acrylate UV
A hardening resin was applied and cured by irradiation with ultraviolet light.

When releasing the molded lens sheet from each mold, the mold release properties were extremely good. Furthermore, the embossments on the lens sheet were not folded and did not contain air bubbles, and a good lens sheet was obtained.

[Effects of the Invention] As described in detail above, the present invention has the effect that a mold that has good preformability and defoaming properties with respect to a molded sheet can be manufactured at a low cost.

[Brief explanation of the drawing]

FIG. 1, FIG. 5, and FIG. 2 are diagrams for explaining the process of molding a lens sheet, the molds used therein, and the problems thereof. 1... Molding mold 2... UV curing resin 3... Lens sheet 4... Part-time job Patent applicant Dai Nippon Printing Co., Ltd. Agent Patent attorney Sickle 1) Second son Yoshizu (Q) Figure 2 (b) ) (b) (d)

Claims (1)

[Claims] In plastic molds that mold sheets with fine embossed shapes using ionizing radiation-cured resin, the solubility parameter is 8.0 or less and the elongation at the break point is 70%.
A plastic molding die characterized by having an embossed shape formed on the above solvent-resistant plastic.