JPH08136708A - Fresnel lens manufacturing method - Google Patents

Abstract

(57) [Summary] [Objective] To manufacture a Fresnel lens having different optical characteristics from the same master mold of the Fresnel lens. [Structure] The refractive index of a Fresnel lens having a predetermined shape and having a desired focal length f is calculated, and a monomer and an oligomer having such a ratio of the refractive index and a polymerization initiator are mixed to form an ultraviolet curable resin. Generated, apply the generated UV curable resin to the Fresnel lens master mold and transfer the master mold,
Defoam, put backing material, irradiate with ultraviolet rays to cure,
Finally, take out the completed Fresnel lens from the master mold.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a Fresnel lens.

[0002]

2. Description of the Related Art In order to design and manufacture a Fresnel lens, the Fresnel lens shape is determined by solving an equation for obtaining the lens shape based on the refractive index of the resin formed and the required optical characteristics (mainly focal length). Find, make a mold of the desired shape,
Conventionally, a method of transferring this mother die to the forming resin has been adopted.

[0003]

However, according to the method shown as the prior art, only one type of Fresnel lens can be manufactured from one type of master mold. Therefore, it is necessary to manufacture the master block every time the optical characteristics of the Fresnel lens are changed. Further, in order to manufacture a plurality of types of Fresnel lenses having different optical characteristics, as many molds as the number of types of Fresnel lenses are required.
Manufacturing the master mold of the Fresnel lens requires a lot of cost and time, which means that the Fresnel lens itself and
Increasing the cost of products using Fresnel lenses,
This has been a cause of prolonging the design period.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a Fresnel lens manufacturing method capable of manufacturing Fresnel lenses having different optical characteristics from the same Fresnel lens matrix. The purpose is to provide. Another object of the present invention is to provide a Fresnel lens manufacturing method capable of shortening the design period of the Fresnel lens and reducing the costs of the Fresnel lens and Fresnel lens applied products.

[0005]

In order to achieve the above object, a method of manufacturing a Fresnel lens of the present invention is to obtain a refractive index of a Fresnel lens having a predetermined shape and a desired focal length, Generate and transfer the Fresnel lens master to the forming resin, cure the forming resin to which the master is transferred, remove the cured forming resin from the master, and remove the Fresnel lens having the desired focal length. To manufacture. Preferably, the forming resin is a photocurable resin that causes photopolymerization, and a photocurable resin having the refractive index obtained by mixing a monomer and an oligomer in a predetermined ratio used in the photocurable resin with a polymerization initiator. To apply the photo-curable resin to the Fresnel lens matrix, transfer the shape of the master to the photo-curable resin, and apply a predetermined amount to the photo-curable resin applied to the Fresnel lens master. Light is applied to cure. Preferably,
A backing material is placed on the photo-curable resin applied to the Fresnel lens matrix, and then predetermined light is irradiated to cure the photo-curable resin.

The forming resin is a thermosoftening resin, and a plurality of types of thermosoftening resin raw materials having different refractive indexes are mixed at a predetermined ratio to produce the thermosoftening resin having the refractive index. The thermosoftening resin is heated and softened and injected into the mother mold of the Fresnel lens, and the thermosoftening resin injected into the mother mold of the Fresnel lens is pressed to change the shape of the mother mold to the thermosoftening resin. And the thermosoftening resin is cooled and cured.

The forming resin is a room temperature curable resin,
A plurality of different types of room temperature curable resin raw materials having different refractive indexes are mixed at a predetermined ratio to produce a room temperature curable resin having the above refractive index, and the room temperature curable resin is injected into a Fresnel lens matrix, The shape of the master mold is transferred to the room temperature curable resin injected into the master mold of the Fresnel lens, and the room temperature curable resin is cured.

[0008]

Function: A plurality of thermosoftening resins or room temperature curable resins are mixed, or a monomer and an oligomer constituting an ultraviolet curable resin are mixed with a polymerization initiator in a predetermined ratio to change the refractive index of the formed resin. . The mother die of the Fresnel lens is transferred to the forming resin whose refractive index is changed, the forming resin on which the mother die is transferred is removed from the mother die, and only the refractive index of the Fresnel lens having the same shape is changed. By changing only the refractive index of the forming resin, a Fresnel lens having the same shape and different optical characteristics (focal length) corresponding to the change of the refractive index of the forming resin is generated from the same matrix.

[0009]

[Embodiment 1] Hereinafter, a method of manufacturing a Fresnel lens according to the present invention using an ultraviolet curable resin as a forming resin will be described with reference to the drawings. 1A and 1B are views showing a configuration of a Fresnel lens 1 manufactured by a Fresnel lens manufacturing method according to the present invention, wherein FIG. 1A is a sectional view of the Fresnel lens 1, and FIG. It is the figure seen from the direction.

As shown in FIG. 1, the Fresnel lens 1 is
It is composed of a forming resin 10 and a backing material 12. The backing material 12 may be omitted. The forming resin 10 in the first embodiment is, for example, an acrylate-based ultraviolet curable resin. Such an ultraviolet curable resin is a mixture of a predetermined resin monomer (monomer), a low polymer (oligomer), and a polymerization initiator, and the refractive index thereof can be changed by changing the ratio of the monomer and the oligomer. Has the property that it can be changed to any value.

The Fresnel lens manufacturing method according to the present invention will be described below with reference to FIGS. FIG. 2 is a cross-sectional view of a matrix 2 used for manufacturing the Fresnel lens 1 shown in FIG. 1 in the Fresnel lens manufacturing method according to the present invention. FIG. 3 shows the Fresnel lens 1 shown in FIG.
FIG. 5 is a diagram illustrating a Fresnel tooth angle θ by enlarging a portion a of FIG. FIG. 4 is a diagram illustrating the focal length f of the Fresnel lens 1 and the distance R from the center.

FIG. 5 is a graph showing the relationship between the distance R from the center of the Fresnel lens 1 and the Fresnel tooth angle θ. In FIG. 6, the distance R from the center and the Fresnel tooth angle are
Resin 1 for forming the Fresnel lens 1 having the relationship shown in FIG.
FIG. 6 is a diagram showing the relationship between the refractive index of 0, the distance R from the center, and the focal length f in the form of a graph.
b and c indicate the cases where the forming resin 10 (FIG. 1) has a refractive index of 1.50, 1.55, and 1.60, respectively.
FIG. 7 is a process diagram showing a Fresnel lens manufacturing method according to the present invention when an ultraviolet curable resin is used as the forming resin 10 shown in FIG.

First, for example, when an ultraviolet curable resin having a refractive index of the central value of the variable range of the refractive index of the ultraviolet curable resin is used, its focal length f becomes the desired central value of the variable range of the focal length. Find the shape of Fresnel lens 1
A master block 2 used for manufacturing the Fresnel lens 1 is manufactured. The teeth 102 of the Fresnel lens shown in FIG.
The Fresnel tooth angle θ of _i (i is an integer) can be obtained from the graph shown in FIG. 5, for example, corresponding to the distance R from the center shown in FIG.

The focal length f of the Fresnel lens shown in FIG. 4 is a function of the distance R from the center. The focal length f of the Fresnel lens 1 whose Fresnel tooth angle θ is designed based on the graph shown in FIG.
In the case of 0, 1.55, and 1.60, respectively, as shown in FIG.
The curves a, b, and c are shown in the inside. As the mother die 2, a metal die, a resin die (child) obtained by transferring the die to a predetermined resin, a resin die (grandchild) obtained by further transferring the resin die to another resin, etc. Can be used.

As shown in FIG. 7, in step 01 (S01), the refractive index of a Fresnel lens having the same shape as the Fresnel lens 1 and having a desired focal length f is calculated,
Alternatively, a UV-curable resin is produced by mixing a monomer and an oligomer having a ratio that gives a calculated refractive index of the UV-curable resin, obtained from a graph, with a polymerization initiator. Process 02
In (S02), the mother die 2 is prepared for injecting the ultraviolet curable resin. In step 03 (S03), the UV-curable resin mixed as described above is applied to the Z side of the master mold 2 shown in FIG. 2, the master mold 2 is transferred to the UV-curable resin, and further, a predetermined amount is applied. A quantity of the UV curable resin is injected into the mother mold 2. The ultraviolet curable resin injected into the matrix 2 becomes the forming resin 10 shown in FIG.

In step 04 (S04), the bubbles generated in the ultraviolet curable resin injected into the matrix 2 are removed (defoamed). In step 05 (S05), the backing material 12 is placed on the defoamed ultraviolet curable resin. In step 06 (S06), the ultraviolet curable resin on which the backing material 12 is placed is irradiated with ultraviolet rays and cured to form the Fresnel lens 1. Process 0
7 (S07), the Fresnel lens 1 is taken out of the matrix 2.

As shown in FIG. 6, the ultraviolet curable resin used as the forming resin 10 has a refractive index of 1.50 to 1.6.
By changing to 0, the focal length f at the position of 40 cm (R = 40 mm) from the center of the Fresnel lens 1 can be set to any value within the range of about 600 mm to about 850 mm. In other words, by changing the refractive index of the forming resin 10 by 0.1, the focal length of the Fresnel lens 1 can be changed by about 15%. In addition, the refractive index of the acrylate-based ultraviolet curable resin is 1.50 to 1.6.
It is relatively easy to change in the range of 0.

The Fresnel lens 1 is, for example, 40 inches to
When used as a screen of a 60-inch rear projection television, 4 to 5 types are required.
Therefore, when the Fresnel lens 1 is manufactured by the Fresnel lens manufacturing method shown as the conventional technique, the same number of matrixes 2 is required. On the other hand, according to the Fresnel lens manufacturing method according to the present invention shown in the first embodiment, it is sufficient to prepare at least two matrixes 2 (for 40 inches to 50 inches and for 50 inches to 60 inches). Become. Therefore, according to the Fresnel lens manufacturing method of the present invention, the design period of the rear projection television and its screen can be shortened, and the cost can be reduced.

In the first embodiment, the case where the ultraviolet curable resin is used as the material of the forming resin 10 is shown. However, if the resin is a resin which is cured by receiving a predetermined light (electromagnetic wave), the forming resin is formed. Any material may be used as the material of 10.
Further, as shown in FIGS. 1 and 7, the Fresnel lens 1 is configured by using the back material 12, but the Fresnel lens 1 may be configured without using the back material 12 as described above. Further, other steps such as a step of writing the manufacturer's name on the Fresnel lens 1 may be added to the step shown in FIG.

[0020]

Second Embodiment A second embodiment of the Fresnel lens manufacturing method according to the present invention will be described below with reference to FIG. FIG.
FIG. 4 is a process diagram showing a Fresnel lens manufacturing method according to the present invention when a thermosetting resin is used as the forming resin 10 shown in FIG. 1. As shown in FIG. 8, step 10 (S10)
In the same manner as in the case of using an ultraviolet curable resin as the forming resin 10 shown in the first embodiment, the Fresnel lens 1
Then, the refractive index of the Fresnel lens having the same shape as and having the desired focal length f is calculated. Further, a plurality of types of thermosoftening resins, for example, a polycarbonate resin (PC) and an acrylic resin (PMMA) are mixed at a ratio that provides the calculated refractive index.

In step 11 (S11), the thermosoftening resin mixed as described above is heated to be softened, and is injected into the Z side of the mother die 2 shown in FIG. 2 to remove bubbles. Step 12 (S
In 12), the defoamed thermosoftening resin is pressed to transfer the mother die 2 to the thermosoftening resin. In step 13 (S13), the pressed thermosoftening resin is cooled and cured,
The Fresnel lens 1 is used. In step 14 (S14), the Fresnel lens 1 is taken out from the matrix 2.

The above-mentioned polycarbonate has a refractive index of 1.
59, and the refractive index of acrylic is 1.49. Therefore, when these thermosoftening resins are mixed, the refractive index of the formed resin can be set to an arbitrary value within the range of the refractive index of 1.49 to 1.59. Therefore, the focal length f can be changed in the same range as in the case of using the ultraviolet curable resin shown as the first embodiment. Further, the Fresnel lens 1 manufactured by the Fresnel lens manufacturing method shown in the second embodiment is similar to the Fresnel lens 1 manufactured by the Fresnel lens manufacturing method shown in the first embodiment, for example, a rear projection television. It goes without saying that it can be used as John's screen.

In the second embodiment, the thermosoftening resin is used as the forming resin, but a room temperature curable resin may be used instead of the thermosoftening resin. Moreover, in FIG.
Although the case where the Fresnel lens 1 is configured without using 2 (FIG. 1) is shown, other steps such as adding the backing material 12 to the Fresnel lens 1 may be added. Further, although the case where polycarbonate and acrylic are used as the material of the forming resin 10 has been shown, any resin may be used as long as it is a resin having thermal softening property and capable of obtaining a desired refractive index. The Fresnel lens manufacturing method shown in each of the embodiments can have various configurations, as shown as a modification of each of the embodiments.

[0024]

As described above, according to the Fresnel lens manufacturing method of the present invention, it is possible to manufacture Fresnel lenses having different optical characteristics from the same master mold of Fresnel lenses. According to the Fresnel lens manufacturing method of the present invention, the design period of the Fresnel lens is shortened,
The cost of the Fresnel lens and the Fresnel lens application product can be reduced.

[Brief description of drawings]

FIG. 1 is a view showing a shape of a Fresnel lens manufactured by a Fresnel lens manufacturing method according to the present invention,
(A) is a cross-sectional view of the Fresnel lens, and (B) is a view of the Fresnel lens as viewed from the Z direction.

FIG. 2 is a cross-sectional view of a master die used for manufacturing the Fresnel lens shown in FIG. 1 in the Fresnel lens manufacturing method according to the present invention.

FIG. 3 is an enlarged view of a portion a of the Fresnel lens shown in FIG.

4 is a diagram illustrating a focal length f and a distance R from the center of the Fresnel lens shown in FIG.

5 is a graph showing the relationship between the distance R from the center of the Fresnel lens shown in FIG. 1 and the Fresnel tooth angle θ.

6 shows a relationship between the distance R from the center of the Fresnel lens shown in FIG. 4 and the Fresnel tooth angle, the refractive index of the resin forming the Fresnel lens, the distance R from the center, and the focal length f. It is a figure which shows the relationship with and in a graph format.

FIG. 7 is a process diagram showing a Fresnel lens manufacturing method according to the present invention when an ultraviolet curable resin is used as the forming resin shown in FIG.

8A to 8C are process diagrams showing a Fresnel lens manufacturing method according to the present invention when a thermosetting resin is used as the forming resin shown in FIG.

[Explanation of symbols]

1 ... Fresnel lens, 2 ... Back material, 10 ... Forming resin,
12 ... Back material

Claims (5)

[Claims] 1. A refractive index for a Fresnel lens having a predetermined shape and a desired focal length is obtained, a forming resin having the refractive index is generated, and a mother die of the Fresnel lens is transferred to the forming resin. A Fresnel lens manufacturing method of curing a transferred forming resin, removing the cured forming resin from the master mold, and manufacturing a Fresnel lens having the desired focal length. 2. The forming resin is a photocurable resin that causes photopolymerization, and a monomer and an oligomer having a predetermined ratio used for the photocurable resin and a polymerization initiator are mixed to photocur the resin having the refractive index. A resin is generated, the photo-curing resin is applied to the Fresnel lens master, the shape of the master is transferred to the photo-curing resin, and the photo-curing resin applied to the Fresnel lens master is predetermined. The Fresnel lens manufacturing method according to claim 1, wherein the Fresnel lens is cured by irradiating the light. 3. The Fresnel lens manufacturing method according to claim 2, wherein a backing material is placed on the photo-curable resin applied to the Fresnel lens matrix, and then the photo-curable resin is cured by irradiating with predetermined light. 4. The forming resin is a thermosoftening resin, and a plurality of types of thermosoftening resin raw materials each having a different refractive index are mixed at a predetermined ratio to produce the thermosoftening resin having the refractive index. Then, the thermosoftening resin is heated and softened to be injected into the Fresnel lens master mold, and the thermosoftening resin injected into the Fresnel lens master mold is pressed to change the shape of the master mold to the heat softening resin. A method for producing a Fresnel lens according to claim 1, wherein the Fresnel lens is transferred to a heat-resistant resin and the heat-softening resin is cooled and cured. 5. The forming resin is a room temperature curable resin, and a plurality of kinds of room temperature curable resin raw materials each having a different refractive index are mixed at a predetermined ratio to produce the room temperature curable resin having the refractive index. Then, the room temperature curable resin is injected into a Fresnel lens matrix, the shape of the matrix is transferred to the room temperature curable resin injected into the Fresnel lens matrix, and the room temperature curable resin is cured. Item 2. The Fresnel lens manufacturing method according to Item 1.