JPH09141663A - Mold manufacturing method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for producing a molding die, which is capable of obtaining various kinds of lens sheets from one metal die and which can reduce the production cost. SOLUTION: A step of injecting a first thermosetting resin into a female (concave) mold of a metal mold, curing the resin at a first temperature, and then releasing the mold to produce a resin male (convex) mold. , Second to the male (convex) type
Of the first hardening type (female (concave) type) by injecting the first hardening type resin or ceramics at the second temperature, and the second hardening type resin or ceramics from the male (convex) type to the first hardening type. And a step of secondarily hardening the first hardening type of the second hardening resin or ceramics at a third temperature. It is characterized in that the temperature is selected so as to obtain a molding resin mold or a ceramic mold having a size different from that of the metal mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, the production and operation of screens for video projection televisions.
The present invention relates to a method for manufacturing a molding die used for manufacturing a Fresnel lens sheet for a bar head projector.

[0002]

2. Description of the Related Art Generally, in a Fresnel lens sheet, in order to reduce the lens thickness of a convex lens, the lens surface is finely divided in the direction perpendicular to the lens thickness direction, and the divided lens surface is approximated to a straight line. It is a thin-walled optical lens having a shape arranged concentrically for each identical angle component, which is designed by translating the above-described components in parallel on a plane perpendicular to the division direction. For example, in the case of a Fresnel lens sheet used for a screen for video projection television,
It is necessary to manufacture one having a function of collecting the divergent light from the projection lens and therefore having a pattern designed to satisfy the optical condition. Usually, as a manufacturing method of the Fresnel lens sheet, there are a hot press molding method, a casting method, an injection method and the like. Recently, production by the photopolymer method (2P method) is also performed. In these methods, a high precision NC lathe is used to cut a V groove of a shape opposite to the Fresnel lens shape on a metal plate, and the shape is accurately transferred to perform molding. It is common to mold one by one. This molding method requires a large number of cutting dies for mass-producing Fresnel lenses, but the time required for cutting one die is as long as 150 to 200 hours, and the cutting yield is low. Considering the life of the mold, the cost of the mold in the manufacturing cost becomes very large.

[0003]

On the other hand, there is a method of producing a molding resin mold having the same size as a mold from a metal mold through an intermediate mold (see Japanese Patent Laid-Open No. 1-174418). Since a plurality of intermediate molds are manufactured from the metal mold and a plurality of molding resin molds are manufactured through the intermediate molds, the average life of the metal mold seen from the molded product is improved. However, since only one Fresnel lens sheet of one size can be obtained with one metal mold, it is necessary to produce many kinds of metal dies in order to manufacture many kinds of Fresnel lens sheets. , It did not lead to effective cost reduction.

Incidentally, in the case of a projection television, moire is observed due to the combination of the pitches of the lenticular lens sheet and the Fresnel lens sheet. The reason for the occurrence of the moire is not completely theoretically clarified, and it is empirically necessary to select the best combination of pitches that minimizes the moire. If a moire occurs in a molded product manufactured using such a mold and is actually used in combination with a lenticular lens, the metal mold may have to be manufactured again. Also, if the pitch of the optical elements of the lenticular lens sheet changes, the Fresnel lens sheet is often changed, and it is necessary to cut the metal mold each time.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain various kinds of lens sheets from one metal mold.
It is an object of the present invention to provide a method for manufacturing a molding die that can obtain a mold and can reduce the manufacturing cost.

[0006]

A method for manufacturing a mold according to the present invention which solves the above-mentioned problems is to inject a first thermosetting resin into a female (concave) mold of a metal mold, and apply it at a first temperature. A step of producing a resin male (convex) mold by curing and then releasing the mold, and a step of injecting a second curable resin or ceramics into the male (convex) mold and primary curing at a second temperature to perform primary curing The step of producing a curable mold, the step of releasing the first curable mold of the second curable resin or ceramics from the male (convex) mold, and the third step of the first curable mold of the second curable resin or ceramics Secondary curing at a temperature of, and the first, second and third temperatures are selected so as to obtain a molding resin mold or a ceramic mold having dimensions different from those of the metal mold. Characterize. That is, the first temperature of the thermosetting resin transferred from the mold and the second temperature and the third temperature of the second curable resin or ceramics transferred from the male (convex) mold are selected and the target is selected. A resin mold for molding having the following dimensions is prepared. As a result, the selection range of the pitch of the Fresnel lens or the like that can be manufactured from one metal mold is widened, and it becomes possible to easily deal with the moire problem and the like.

Here, the "different size" means, for example, that the ratio of the size of the molding resin mold or the ceramic mold to the size of the metal mold is in the range of 1.01 to 1.05 or 0.
It is in the range of 80 to 0.99.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for producing a molding die suitably used for producing screens for video projection televisions and other Fresnel lens sheets. Especially for the metal mold with concave Fresnel lens shape,
It is preferable to cast a thermosetting type first resin having flexibility (for example, an addition polymerization type silicone resin is preferable) and cure the resin under a suitable temperature condition to prepare an intermediate type. . A second resin or ceramics having rigidity after molding (for example, a casting epoxy resin or a melamine resin is preferable) is cast into the intermediate mold having the convex Fresnel lens shape to form the concave Fresnel lens shape. A molding resin mold having the above is prepared. Table 1 shows examples of materials constituting the resin (convex) mold and the molding resin mold or the ceramic mold according to the present invention, and the temperature range that can be selected as the curing shrinkage rate, the linear expansion coefficient and the curing temperature. In addition, in Table 1, the linear expansion coefficient of 7/3 brass generally used as a metal mold material is also shown.

[0009]

[Table 1]

Here, the length L'of the molding resin mold with respect to the size of the original metal mold is expressed by the following equation. L '= L {1+ (T1-T0) K1} (1-A) {1+ (T2-T1) K2} (1-B' (T2)) {1+ (T0-T2) K3} (1 -B "(T3)) L ': Length of molding resin mold at room temperature L: Length of metal mold at room temperature T0: Room temperature 25 ° C T1: Curing temperature of intermediate mold T2: Primary curing of molding resin mold Temperature K1: Coefficient of linear expansion of metal mold K2: Coefficient of linear expansion of intermediate mold A: Molding shrinkage of intermediate mold from T1 ℃ B '(T2): Molding shrinkage of resin mold for molding from T2 ℃ B " (T3): Molding shrinkage of the molding resin mold from T3 ° C. K3: Linear expansion coefficient of the molding resin mold With this equation, the rate of change with respect to the dimensions of the original metal mold is calculated in advance. By selecting the curing conditions of the resin and the second resin, it becomes possible to manufacture a molding resin die having a target dimension within a range of the dimensional change rate of 5% to -20%.

[0011]

【Example】

Example 1 An example of the present invention will be described below with reference to the drawings.
In addition, the following examples are cases in which the present invention is applied to the manufacture of Fresnel lens sheets. First, the female (concave) Fresnel lens shape of the Fresnel lens sheet 7/3
A metal mold made of brass plate is cut by a high-precision NC lathe at a constant temperature of T ° C, and using this mold, an addition polymerization type silicone with excellent dimensional stability, releasability and transferability. −
A resin mold (intermediate mold) made of resin and having a male (convex) Fresnel lens shape is cured under a temperature condition of T1 ° C. Here, after casting the silicone resin, vacuum defoaming is performed so that no bubbles are generated on the contact surface with the metal mold, and on the opposite surface, the contact surface with the metal mold is approximately horizontal. It is advisable to arrange a plate with smoothness.

The polymerization temperature T1 ° C. can be selected by using a curing catalyst, a polymerization retarder, etc. within a temperature range of 10 to 50 ° C.
After completely curing, the silicone resin mold is removed from the cutting mold to obtain a resin mold (intermediate mold) having a male (convex) Fresnel lens shape. As a second resin, for example, an epoxy resin is injected into this mold under the temperature condition of T2 ° C. to perform primary curing. At this time, it is necessary to control the temperature of the silicone resin mold to T2 ° C. Further, after injecting the epoxy resin, it is sufficiently degassed under vacuum with heating so that no bubbles are generated on the lens surface after curing. Thereafter, the silicone resin mold is released, and only the epoxy resin mold is secondarily cured under the temperature condition of T3 ° C. The values based on the formula of the pitch length Y ′ of the molding resin die and the like and examples thereof are shown in Tables 2 and 3.

[0013]

[Table 2]

[Table 3]

Table 4 shows the results of checking the occurrence of moire by combining the Fresnel lens sheet thus obtained and a lenticular lens sheet of several kinds of pitches.

[0015]

[Table 4]

From Table 2, Table 3 and Table 4, the pitch (P _F ) of the Fresnel lens of epoxy resin type from the same mold
Molded resin molds with a difference of about 2% in size can be manufactured, and it is possible to correspond to lenticular lens sheets in the range of ○ in Table 4, so it is possible to change the mold of one kind of size to the screen of the above pitch. It can be seen that a corresponding Fresnel lens can be manufactured.

That is, if the effective dimensional difference can be obtained only by setting the curing conditions and the optical systems are similar to each other, it is possible to use two molds.
It is possible to manufacture Fresnel lens sheets having more than one type of effective dimensional difference, and it is possible to reduce the cost of the mold.

In the above example, the manufacturing of the mold for the Fresnel lens sheet for the projection television is described, but in addition to this, it is also used for the lenticular lens sheet, the Fresnel lens for the OHP and the like. it can.
Further, the present invention is not limited to the transmission type and reflection type screens, and can be applied as a light receiving Fresnel lens and a molding die for other molded products.

Example 2 As an example of a ceramic type, an example using polysilazane (manufactured by Tonen Corporation) is given. As in Example 1, a metal mold made of a 7/3 brass plate having a female (concave) Fresnel lens shape of a Fresnel lens sheet was cut by a high-precision NC lathe at a constant temperature T ° C. Then, using this mold,
A resin mold (intermediate mold) made of an addition polymerization type silicone resin and having a male (convex) Fresnel lens shape is prepared, and a fluorine-based releasing agent is applied to the surface of the resin mold and dried. 20 of polysilazane was added to the resin mold in a dry nitrogen atmosphere.
% Xylene solution is spray coated, dried and coated several times to make the coating film thickness uniform to about 1 to 3 μm, and then T3
The polysilazane film forming operation of firing at 0 ° C. is repeated five times or more to produce a ceramic mold having a female (concave) Fresnel lens shape. Then, an epoxy resin as a backing material is cast from the back surface of the ceramic mold and cured at T2 ° C. After that step, release the silicone resin,
The temperature of the epoxy resin-backed ceramic mold is raised to T3 ° C. to obtain a molding ceramic mold. The values based on the formula of the pitch length Y ′ of the molding ceramic die and the like and examples thereof are shown in Tables 5 and 6.

[0020]

[Table 5]

[Table 6]

Table 7 shows the results of checking the occurrence of moire by combining the Fresnel lens sheet thus obtained with lenticular lens sheets of several kinds of pitch.

[0022]

[Table 7]

It can be seen from Table 7 that a plurality of types of ceramic molds can be produced from a metal mold having a pitch of 100 μm, and the lenticular lens sheet in the range of ○ can be applied.

[0024]

According to the present invention, a plurality of molding resin molds having different sizes can be manufactured from one metal mold. This makes it possible to support a plurality of types of products, and the number of times of cutting the metal mold can be significantly reduced. Therefore, in the projection television, it is necessary to select a combination in which moiré, which is a problem, is not noticeable due to the combination of the pitches of the optical elements of the lenticular lens and the Fresnel lens, but the fine adjustment of the optimization can be easily performed. . As a result of the above, it will lead to a large reduction in the metal die manufacturing cost.

Claims (2)

[Claims] 1. A step of injecting a first thermosetting resin into a female (concave) mold of a metal mold, curing the resin at a first temperature, and then releasing the mold to produce a resin male (convex) mold. And the second male type (convex)
Of the first hardening type (female (concave) type) by injecting the first hardening type resin or ceramics at the second temperature, and the second hardening type resin or ceramics from the male (convex) type to the first hardening type. And a step of secondarily hardening the first hardening type of the second hardening resin or ceramics at a third temperature. A method for producing a molding die, wherein a temperature is selected so as to obtain a molding resin mold or a ceramic mold having a size different from that of the metal mold. 2. The ratio of the size of the molding resin mold or the ceramic mold to the size of the metal mold is 1.01 to 1.0.
The method for producing a mold according to claim 1, wherein the mold is in a range of 5 or 0.80 to 0.99.