JPH06154934A - Working method for metallic die for microlens - Google Patents

Abstract

PURPOSE:To form a microlens die after correcting a shape of a punch so that an interference of adjacent lens die elements can be obviated. CONSTITUTION:A relation of a radius of curvature R1 of a punch 10 and an approximate radius of curvature R2 of a lens die element 16 is derived experientally in advance. The punch 10 is constituted of a sintered hard alloy, and in the tip of this punch 10, the convex face of the radius of curvature R1 corresponding to the radius of curvature R2 is formed, based on this relation. By cutting experientally this punch 10 into the surface of a metallic die base metal 14, plural lens die elements 16 are formed adjacently in a lattice-like array. Subsequently, a face height deviation in a measuring line running along the radial direction of an arbitrary lens die element 16 whose periphery is surrounded by the lens die element 16 is measured, and by replacing this deviation with a correction amount, the punch 10 is subjected to correction working, and by using the punch 10 subjected to correction working, a metallic die of a microlens is worked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlens mold working method.

[0002]

2. Description of the Related Art In CCD (Electronic Coupling Device) and active matrix type liquid crystal displays, how to avoid a decrease in pixel aperture ratio has become a major issue as the resolution becomes higher. As a means for solving this, a method of condensing light from a light source in the opening of a pixel has been proposed. According to this method, a transparent plate having a large number of microlenses formed in a grid arrangement is arranged on the light source side of a liquid crystal display, but it is extremely difficult to form a very large number of microlenses regularly on the surface of the transparent plate.

However, in the latest technology, for example, Japanese Patent Laid-Open No. Hei 3
JP-A-288802 discloses a glass substrate that has been optically polished and is made of fine low melting point glass spheres as a lens material, and the glass spheres are hot-molded by a press molding die having a large number of concave spherical microlens-type elements. However, there has been proposed a method of forming a regular lattice-shaped convex lens array.

The press-molding die uses a cemented carbide as a base material, the surface of which is lapped and polished with ultrafine diamond powder to form a mirror surface, and a hemispherical tip of a diamond punch is attached to the mirror surface. Are stroked and brought into contact (cut) by a pushing device which is numerically controlled with high precision, and concave spherical microlens-type elements are formed adjacent to each other in a grid-like arrangement.

[0005]

The inventor of the present invention has found a problem in the prior art that the tip shape of the diamond punch is not accurately transferred to the die base material as it is. This is due in part to the transfer rate of the punch and the other is due to the interference of adjacent lens-type elements.

That is, in the case of Japanese Patent Laid-Open No. 3-288802, a cemented carbide (WC-5T) is used as the base material of the press-molding die.
iC-8Co) or austenitic steel (SUS316)
These are the transfer rates by the diamond punch, that is, the approximate radius of curvature (R2) of the concave spherical microlens type element 4 transferred to the mold base material 2 as shown in FIG.
And the radius of curvature of the convex spherical surface 6a of the diamond punch 6 (R
The ratio (R2) / (R1) to 1) is larger than 100% as shown in FIG. 6A because of the elasticity of the die base material 2.

That is, even when the punch 6 is stroked toward the die base material 2 and the tip of the punch 6 is cut into the base material 2 to form the microlens type element 4 having the concave spherical surface, the punch 6 is formed.
When is pulled, the bottom portion 4a of the lens-type element 4 is raised by the restoring action by elasticity, and the radius of curvature is increased accordingly. It should be noted that this radius of curvature is not constant in the radial direction of the lens-type element 4, and is accurately called an approximate radius of curvature.

FIG. 6 (A) shows the result of measurement of the transfer rate of a single lens-type element 4 having no lens-type elements adjacent to the periphery thereof, which is almost 100% when the punch 6 is cut to a depth of about 20 μm. Transfer rate. Since the transfer rate represents the fidelity of transfer of the punch 6 shape to the die base material 2, the transfer rate is preferably closer to 100%. However, in actuality, as will be described later, since the influence on the adjacent lens-type element is slightly stopped, the cut amount cannot be increased up to 20 μm. Therefore, the cutting depth is 10μ
The radius of curvature (R1) and (R
It is proposed that the relationship 2) is obtained experimentally in advance and the die base material 2 is processed using the punch 6 of (R1) corresponding to the desired radius of curvature (R2). According to this, a lens type element having a desired radius of curvature can be obtained even when the transfer rate is 100% or more.

As shown in FIG. 7, the radii of curvature (R1) and (R2)
If the relationship of (1) is sought, the problem of transfer rate can be overcome, but the problem of interference between adjacent lens-type elements remains. That is, since the lens type elements are actually formed adjacent to each other in a grid-like arrangement, for example, when the lens type elements 4 are sequentially formed from left to right in FIG. 8, when the lens type elements 4 on the right side are formed, the punch 6 is formed. The bottom portion 4a of the lens-shaped element 4 formed in the center is pushed up by the influence of the notch and the radius of curvature of the lens-shaped element 4 (because it becomes an aspherical surface, to be exact, the approximate radius of curvature) (R2) is increased conversely. I will let you. This is one type of interference of lens-type elements.

FIG. 6B shows the relationship between the cut amount and the transfer rate when the lens elements 4 are adjacent to each other.
It can be seen that the transfer rate is generally larger than that in (A) due to the interference of the lens-type element 4. Also in FIG.
Shows the surface height error at the measurement line along the radial direction of the lens type element 4 at the distance (R2 ′) from the center of curvature P to the surface of the lens type element 4 in FIG. The radius is (R2), and the broken line H is drawn horizontally at the height position of (R2) from the horizontal axis. From the figure, in the central part and the peripheral part of the lens type element 4, the distance (R2 ′) is the radius of curvature (R2).
You can see that it is slightly longer than 2). Due to the interference, the radius of curvature at the center of the lens-shaped element 4 becomes large, but the shape is extremely V-shaped.

Another type of interference of lenticular elements 4 is the distortion of the ridges formed between lenticular elements 4. That is, if the cut amount is increased, the already formed lens-type element 4 is adversely affected as described above, so the cut amount is set as shallow as possible. However, with such a shallow cut amount, the ridge line between the adjacent lens-type elements 4 which should originally be a straight line is likely to be distorted when the punch 6 is cut, so that the condensing performance may vary among the lens elements of the microlens. There is.

As described above, the cut amount may not be too shallow or too deep, but the problem of interference of the lens-type element 4 occurs even with an intermediate cut amount. In FIG. 6B, when the cut amount is 5 to 10 μm, the transfer rate is about 150%, and the problem of this transfer rate is that the desired curvature is obtained by obtaining the relationship between the curvature radii (R1) and (R2) as shown in FIG. Corresponds to the radius (R2) (R
This can be overcome by selecting the punch 6 of 1), but it is necessary to process the punch 6 into an aspherical surface in order to make the surface of R2 a perfect spherical surface. As described above, there is no solution to the problem of interference of the lens-type element 4 except for correcting the tip shape of the punch 6, that is, processing it into a predetermined aspherical surface. However, the conventional punch 6
Is made of diamond and is punch 6 for the following reasons.
It was extremely difficult to process the aspherical surface.

(1) Since diamond has high hardness and abrasion resistance, it is difficult to process it freely.

(2) In the characteristics of diamond, the hardness differs depending on the crystal direction (anisotropic), so that it is difficult to make the shape uniform over the entire surface of the punch.

(3) It takes much time and cost to improve accuracy even in spherical surface processing, but if it is an aspherical surface, it takes more time and cost than a spherical surface.

An object of the present invention is to provide a punch capable of shape correction and a novel microlens die machining method using a punch shape correction method capable of eliminating interference of lens-type elements. It is in.

[0017]

SUMMARY OF THE INVENTION The present invention is directed to a radius of curvature (R1) of the convex surface of the punch and an approximate radius of curvature (R) of the concave surface of the lens-shaped element formed by the radius of curvature (R1).
2) was obtained experimentally, the punch was made of cemented carbide, and the radius of curvature (R1) and (R2)
Based on the above relationship, a convex surface for forming a lens mold element having a desired radius of curvature (R2) is formed, and the punch is experimentally cut into the surface of the mold base material to form a plurality of lens molds. Elements are formed adjacent to each other in a grid-like arrangement, and the surface height error of a concave surface of an arbitrary lens-shaped element surrounded by lens-shaped elements at a measurement line along the radial direction is measured. It is characterized in that an error is replaced with a correction amount, the convex surface of the punch is subjected to correction processing, and the die of the microlens is processed using the punch subjected to the correction processing.

[0018]

The punch made of cemented carbide is inferior in hardness and abrasion resistance to the punch made of diamond, but the punch can be easily corrected by a polishing machine. In the die machining method of the present invention, the radius of curvature (R1) of the punch corresponding to the desired radius of curvature (R2) of the lens type element is determined based on the relationship between the radiuses of curvature (R1) and (R2), and the punch is used for testing. The lens-shaped elements are formed adjacent to each other in a grid-like arrangement, and the surface height error at the radial measurement line of any lens-shaped element surrounded by the lens-shaped elements is measured, and this error is corrected. The radius of curvature (R1) of the punch is corrected by a numerical control (NC) polishing machine or the like, and the microlens mold is processed using the corrected punch. Therefore, a microlens mold having a desired spherical or aspherical shape is accurately formed regardless of the interference of the lens mold elements.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, numeral 8 is a numerical control of the punch 10 (N
Pushing device to make a vertical stroke in C), 1
2 is an XY table horizontally arranged below the punch 10 and movable in the X and Y directions, and 14 is a mold base material fixed horizontally at a fixed position on the XY table 12. The material 14 is obtained by cutting out, for example, 13% chrome steel into a rectangular shape, plating the surface with nickel phosphorus, and processing the surface into a mirror surface by a conventional method. Punch 10 is cemented carbide,
For example, it is made of cemented carbide (WC), and is shown in FIG.
The tip convex surface 10a of the punch 10 shown in (B) is shape-corrected to form a desired microlens type element 16 as described later.

The lens-type element 16 is formed by continuously punching the punch 10 in the vertical (Z) direction while the die base material 14 is pressed.
Are formed so as to be adjacent to each other in a lattice-like arrangement by moving the X in the X or Y direction at a predetermined pitch or continuously.
The mold base material 12 on which the lens mold element 16 is formed is mounted on an injection molding machine, and a resin for a lens is injected to obtain a microlens 18 as shown in FIG. 2C.

Since the stroke of the punch 10 can be increased or decreased by NC control, the lens type element 16 can be formed even if the surface of the die base material 14 is a spherical surface or an aspherical surface other than a flat surface. However, when the surface of the die base material 14 is a flat surface, the lower limit of the downward stroke of the punch 14 can be restricted by an appropriate stopper, so that the expensive NC control type pushing device 8 is not necessarily required, and only the vertical movement is required. A simple machine that only exercises is sufficient.

Next, the shape correction of the punch 10 will be described. The lower end surface of the punch 10 is initially (R) in FIG.
Based on the relationship between 1) and (R2), the desired radius of curvature (R
The spherical (or aspherical) convex surface 10b having the radius of curvature (R1) forming the lens type element 16 of 2) is processed. And before the full-scale processing of the lens mold element 16, the mold base material 14
4A and 4B having the same configuration as that of the test die base material 2
A punch 10 is used to test-cut into the 0 using a punching device 8 to form a plurality of adjacent lens-shaped elements L in a grid-like arrangement. The number 1-25 in the drawing indicates the order of forming the lens-type element L.

Next, an arbitrary lens type element L surrounded by the lens type element L (which is a lens type element L such as 7-9 in the order of formation order) is selected as a measurement target, and the lens concerned is selected. The surface height at the measurement line along the radial direction of the mold element L, that is, the distance (R2 ′) from the center of curvature of the lens mold element L to the surface of the lens mold element L is measured. When plotting how much the distance (R2 ') increases or decreases from (R2) based on the radius of curvature (R2),
A graph similar to that of FIG. 9 is obtained. By inverting this graph positively and negatively (up and down) about the broken line H, the graph of FIG. 3B is obtained. This graph shows the portion of the convex surface 10a having the radius of curvature (R1) of the punch 10 to be corrected and the correction amount.

Next, the punch 10 is once removed from the pushing device 8, and the correction data of FIG. 3 (B) is input to this automatic polishing machine using an NC control type automatic polishing machine or the like. The convex surfaces 10a1 and 10a2 of the punch 10 corresponding to the upper graph indicate the distance (R from the center of curvature Q to the convex surfaces 10a1 and 10a2 corresponding to the vertical line length).
1 ′) is decreased, and conversely, the convex surface 10a3 of the punch 10 corresponding to the lower graph increases the distance (R1 ′) from the center of curvature Q to the convex surface 10a3 corresponding to the vertical line length. Perform correction processing. Punch 10 corrected in this way
Is attached to the pushing device 8 again, and full-scale processing of the lens type element 16 is started.

By correcting the convex surface 10a of the punch 10 as described above, the portions E and F larger than the radius of curvature (R2) at the distance (R2 ') from the center P of the lens type element of FIG. The corresponding convex surfaces 10a1 and 10a of the punch 10
Since the distance (R1 ′) of a2 is reduced and corrected, the radius G matches the radius of curvature (R2), and the portion G smaller than the radius of curvature (R2) has the distance (R1 ′) of the corresponding convex surface 10a3 of the punch 10 of Since the correction is increased, it matches the radius of curvature (R2). Therefore, the lens-shaped element 16 having a desired radius of curvature (R2) is formed without any change in the radius of curvature in the radial direction.
When forming an aspherical lens type element, the radius of curvature (R2) is represented by an aspherical expression. At this time, the broken line J in FIG. 3B and the broken line H in FIG. 9 are curves according to the aspherical expression.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, the material of the punch 10 may be an alloy other than cemented carbide (WC), and the material of the die base material is 1
Alloys other than 3% chrome steel may be used. Alternatively, the die base material may be fixed, the pushing device 8 may be placed on the XY table 12 or a similar moving device, and the punch 10 may be stroked while being scanned and moved at a right angle to the stroke direction.

[0027]

As described above, the present invention has found that the punch shape correction is indispensable in order to eliminate the interference of the lens-type elements and process a precise microlens shape, and the shape correction is polished. The conventional diamond punch was changed to cemented carbide so that it could be done easily and at low cost with a machine, etc., and based on the error of the lens type element experimentally formed on the die base material, the punch was made to eliminate this error. Since the microlens mold is processed after shape correction, the lens mold having a desired shape can be accurately formed regardless of the interference of the adjacent lens mold elements.

[Brief description of drawings]

FIG. 1 is a side view of a pushing device and an XY table.

2A is a perspective view of a die base material and a punch before processing, FIG. 2B is a perspective view of a die base material and a punch during processing, FIG.
(C) is a perspective view of a microlens.

FIG. 3A is a side view of a convex surface of a punch, and FIG. 3B is a diagram showing a shape correction amount of the convex surface of the punch.

FIG. 4A is a plan view of a test die base material, and FIG.
Is a cross-sectional view of the mold base material.

FIG. 5 is a side view of a conventional diamond punch and lens-type element.

FIG. 6A is a graph showing the relationship between the cut amount and the transfer rate of a single lens-type element, and FIG. 6B is the cut amount and the transfer rate of a plurality of lens-type elements adjacent to each other in a grid array. The graph figure which shows the relationship with.

FIG. 7 is a graph showing the relationship between the radius of curvature of the punch (R1) and the radius of curvature of the lens-type element (R2).

FIG. 8 is a side view of the punch and lens-type element.

FIG. 9 is a graph showing the surface height error at the measurement line along the radial direction of the lens-type element.

[Explanation of symbols]

 2 Mold base material 4 Micro lens type 6 Diamond punch 8 Pushing device 10 Cemented carbide punch 12 XY table 14 Mold base material 16 Micro lens type element 18 Micro lens 20 Mold base material for test

Claims (1)

[Claims] 1. A surface of a die base material is mirror-finished, and a punch having a fine convex tip is continuously stroked vertically with respect to the mirror surface by a pushing device, and the die base material is aforesaid. In the microlens mold working method, in which a plurality of concave microlens elements are formed adjacent to each other in a lattice-like array on the surface of the mold base material by scanning and moving a plurality of times in the direction perpendicular to the stroke direction, the convex of the punch The relationship between the radius of curvature (R1) of the curved surface and the approximate radius of curvature (R2) of the concave surface of the lens type element formed by the radius of curvature (R1) is experimentally determined, and the punch is made of cemented carbide. At the same time, a convex surface for forming a lens-shaped element having a desired radius of curvature (R2) is formed at the tip of the punch based on the relationship between the radiuses of curvature (R1) and (R2). Cut into the surface of the die base material Then, a plurality of lens-shaped elements are formed adjacent to each other in a grid-like array, and the surface height error of the concave surface of any lens-shaped element surrounded by lens-shaped elements is measured at the measurement line along the radial direction. A microlens mold characterized by measuring, correcting the convex surface of the punch by replacing the surface height error with a correction amount, and processing the microlens mold using the corrected punch. Mold processing method.