JPH0681687B2 - Lens molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lens molding method.

(Prior Art and Problems) A Fresnel lens is made thin in a stepped manner so as to have the optical properties of a thick lens, and usually has a thickness of about 0.7 mm or more.

Therefore, it is impossible to manufacture by general injection molding method, and it is manufactured by embossing or cutting method, but in embossing, heating and cooling of the mold or material must be repeated, and in the cutting method However, it requires a very precise cutting device, and it takes a long time to cut, and the number that can be cut simultaneously by one cutting device is limited.

In general, when a convex or concave lens is injection-molded, since the lens does not have a uniform thickness, there is a possibility that a shrinkage may occur due to shrinkage due to solidification of the resin.

It is an object of the present invention to provide a method for easily forming a large number of lenses without causing defects and a method for forming an extremely thin lens using an ultraviolet curable resin.

(Means for solving the problem) UV curable resin is injected into a mother die whose bottom surface is in the shape of a lens, and the UV radiation is adjusted while adjusting the UV irradiation amount according to the thick and thin parts of the lens shape. The lens is molded by irradiating it to cure the ultraviolet curable resin and taking it out from the mother die.

By injecting UV-curable resin into the master mold whose bottom surface is in the shape of a lens and irradiating the center of the recess with UV spots, the irradiation is sequentially expanded concentrically to cure the UV-curable resin, and then the master mold is removed. Mold the lens.

UV curable resin is injected into a mother die whose bottom surface is in the shape of a lens, and a rotary shading plate having a fan-shaped notch with the center of the disk as the apex is used, depending on the thickness of the recess While adjusting the irradiation amount, ultraviolet rays are irradiated to cure the ultraviolet curable resin, and the lens is molded by taking it out from the mother die.

UV curable resin is injected into a mold with the bottom of the recess shaped like a lens to irradiate the UV with a rotating spot in a spiral shape, and the irradiation amount is adjusted according to the thick and thin parts of the recess while adjusting the rotation speed. Is adjusted to cure the ultraviolet curable resin, and the lens is molded by taking it out from the mother die.

In any of the above methods, a mother mold made of a transparent resin may be used, and ultraviolet rays may be irradiated from the mother mold side.

(Example) In the first method, as shown in FIG. 1, a liquid or gel-like material is formed on a matrix 1 made of metal, glass, synthetic resin, or the like, in which a stepwise concave portion of a desired Fresnel lens is provided. The ultraviolet curable resin 2 is injected, and the transparent synthetic resin sheet 3 is bonded onto it.

Next, ultraviolet rays are initially spot-irradiated from the side of the synthetic resin sheet 3 to the center of the concave portion, and the irradiation range is sequentially expanded concentrically to cure the ultraviolet-curing resin 2. The irradiation of the ultraviolet rays may be performed in the reverse order to the irradiation of the outer periphery of the concave portion, and subsequently, the irradiation range may be reduced and irradiated concentrically toward the center.

Then, the ultraviolet curable resin 2 adhered to the sheet 3 is peeled off from the mother die 1.

Before injecting the ultraviolet curable resin 2 into the mother die 1, a mold release material may be applied to the concave surface of the mother die 1. Also, the mother mold 1
In this case, concave portions may be provided at a plurality of positions to sequentially move one or a plurality of light sources to irradiate the ultraviolet rays, or conversely, the light sources may be fixed and the mother die may be sequentially moved. A known method such as using a lens or a diaphragm can be adopted for the ultraviolet spot and the enlarged irradiation.

In addition, when there is a possibility that the central portion of the concave portion of the mother die rises when the ultraviolet curable resin cures, the synthetic resin sheet 3
It is preferred to apply a slight pressure from above.

In the second method, as shown in FIG. 2, the ultraviolet curable resin 2 is injected into the mother die 4 having the concave bottom surface in the step shape of a Fresnel lens, and the ultraviolet ray is applied to the ultraviolet curable resin 2 by the first method. Similarly, it is irradiated and cured, and the cured ultraviolet curable resin 2 is removed from the matrix 4.

A mold release material may be applied to the concave portion of the mother die 4 before injecting the ultraviolet curable resin.

In the third method, as shown in FIG. 3, a mother die 5 made of a transparent synthetic resin is used instead of the mother die 1 or the mother die 4, and the ultraviolet curable resin 2 is injected into the mother die 5 to After irradiating with ultraviolet rays from the mold 5 side, the cured ultraviolet curable resin 2 is removed from the matrix 5.

FIG. 4 is an explanatory view of the molding of a general convex lens, and the matrix 6 is provided with a concave portion of the convex lens.

FIG. 5 is an explanatory view of molding a general concave lens, and the mother mold 7 is provided with a concave portion of the concave lens.

In any of the molding methods, it is preferable to inject the resin and irradiate with ultraviolet light in a vacuum or reduced pressure chamber so that air bubbles do not occur in the cured and molded resin.

In either method, a plurality of lens-shaped recesses may be provided in the mother die to form a plurality of lenses at the same time.

In any of the methods, the cured and molded UV curable resin 2 removed from the mother die may be cut into a desired shape, or may be warmed a little to be softened and shaped into a desired shape using a mold or the like. You may.

The above ultraviolet irradiation method is suitable for a convex lens or a Fresnel lens that becomes thinner in the outer circumferential direction from the center portion, but the concave lens and the lens shown in FIGS. In the case of a thick lens, it is necessary to increase the irradiation amount of ultraviolet rays toward the outer circumference. What is shown in FIG. 6 is a rotary light shielding plate therefor. The rotary shading plate 8 is provided with a fan-shaped notch 10 having a center 9 as an apex. The angle Q of the notch 10 is an acute angle, and the angle is adjusted according to the thickness of the lens. Further, the edge portion of the notch 10 is also formed in a linear shape or a curved shape depending on the thickness of the lens.

A plurality of protrusions (not shown) are provided on the back surface of the rotary light-shielding plate 8, and the protrusions are attached to a rotating shaft, and while being rotated, the ultraviolet curable resin is irradiated with ultraviolet rays from the notch 10 to cure the resin.

Instead of using the rotating light-shielding plate 8 described above, the ultraviolet spot irradiation light source may be rotated spirally, and the rotational speed may be adjusted according to the thickness of the lens to irradiate the ultraviolet rays.
The spiral rotation may be any rotation method from the center to the outside or from the outside to the center.

FIG. 7 shows an embodiment of a mother die for molding a convex lens, which includes two gaskets 11 and 11 and two cells 1.
A cavity 13 surrounded by 2 and 12 is formed. The cavity 13 has the shape of a convex lens. One or both of the cells 12 and 12 are made transparent. When using this master mold, an ultraviolet curable resin is injected into the cavity 13, ultraviolet rays are irradiated from the cell 12 side of the transparent body to cure the resin, and the gasket 11 and the cell 12 are removed to take out the lens.

FIG. 8 shows an example of a mother die for molding a concave lens, which includes two gaskets 14 and 14 and two cells.
A cavity 15 is formed by 15 and 15. The cavity 15 has the shape of a concave lens. Either or both of the cells 15 and 15 are made transparent.

(Operation and Effect) According to the method of the present invention, the concave surface of the matrix has a stepped shape of a Fresnel lens, or has a convex lens shape or a concave lens shape, and the ultraviolet curable resin injected into the concave portion is cured by ultraviolet rays. The ultraviolet curable resin removed from the master mold forms a desired lens. Irradiate UV rays in a concentric circular pattern from the center of the recess, or conversely from the outer periphery in a concentric circular pattern, or irradiate through a rotating light-shielding plate, or spiral spot light source of UV rays. Since the irradiation amount is adjusted in accordance with the thickness of the lens by rotating the lens, it is possible to prevent the occurrence of a strain due to the contraction caused by the solidification of the resin.

According to the present invention, the depth of the mold or the concave portion of the mold is set to a desired depth suitable for the Fresnel lens so that the Fresnel lens has a thin sheet shape, that is, the thickness of the stepless base of the Fresnel lens is 0.2. Very thin Fresnel lenses of ~ 0.7 mm can be manufactured.

According to the present invention, it is possible to manufacture a large number of lenses having the same shape and having no defects in a short time and at low cost.

[Brief description of drawings]

1 to 5 are explanatory views of the curing state of an ultraviolet curable resin in an embodiment of the present invention, FIG. 6 is a plan view of a rotary light shielding plate, FIG. 7 is an explanatory view of a convex lens matrix, and FIG. [FIG. 3] is an explanatory diagram of a concave lens master die. 1 ... Master mold 2 ... UV curable resin 3 ... Synthetic resin sheet 4, 5, 6, 7 ... Master mold 8 ... Rotation light-shielding plate 10 ... Notch 11, 14 ... Gasket 12, 15, ... Cell 13 ... cavity

Claims (5)

[Claims] 1. A UV-curing resin is injected into a mother die having a concave bottom surface in the shape of a lens, and the UV-irradiation is performed while adjusting the irradiation amount of the UV according to the thick and thin portions of the lens shape. A method of molding a lens, which comprises curing a cured resin and removing the cured resin from a mother mold. 2. A UV-curable resin is injected into a mother die having a concave bottom surface in the shape of a lens, and the center of the concave portion is spot-irradiated with ultraviolet rays. The irradiation is sequentially expanded concentrically to cure the UV-curable resin. A method for molding a lens, which is characterized by taking out from a mold. 3. A rotary light-shielding plate having a fan-shaped notch having the center of a disc as an apex is used by injecting an ultraviolet curable resin into a mother die whose bottom face has a lens shape. A method of molding a lens, which comprises irradiating an ultraviolet ray while adjusting an irradiation amount according to a thin portion to cure an ultraviolet curable resin, and taking out from a mother die. 4. A thick portion and a thin portion of the concave portion are obtained by injecting an ultraviolet curable resin into a mother die having a lens bottom surface of the concave portion, irradiating ultraviolet rays in a rotating spot in a spiral shape, and adjusting the rotation speed. A method of molding a lens, characterized in that the ultraviolet curable resin is cured by adjusting the irradiation amount in accordance with the above, and is taken out from the mother mold. 5. The ultraviolet ray is irradiated from the side of the mother die using a mother die made of a transparent resin.
Item 5. A method for forming a lens according to any one of items 4 to 4.