JPH11277543A - Production of mold for molding micro-lens array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a mold for molding which can stably mold a high precision micro-lens array. SOLUTION: A mold substrate 3 for forming a mold for molding is prepared, and first, the substrate 3 is subjected to force processing by using the first punch 1 having a ruby ball with a radius of curvature of, for example, 100 μm to form a spherical recessed part 4a. The recessed part 4a is formed in the shape of an array by applying the process in the X direction of the substrate 3 in the same pitch. A substrate upheaval part 5 formed by the force processing by the first punch 1 is removed by CMP(chemical polishing). With the use of the second punch 2 having a ruby ball with a radius of curvature of, for example, 125 μm, the force processing is applied on the spherical recessed part 4a to prepare a lens mold 4b to obtain the mold for molding a micro-lens array.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a molding die for molding a microlens array used for, for example, an optical connection means between an image sensor, a liquid crystal panel, or a computer.

[0002]

2. Description of the Related Art A microlens array has a purpose of condensing light reflected from a document in an image sensor to improve transmission efficiency, and condensing incident light into an opening of a liquid crystal panel to transmit light. And a method for increasing the coupling efficiency between an LD array or PD array and a single mode fiber in a parallel optical interconnection for connecting computers. The present invention relates to a method for producing a molding die used for producing these microlens arrays by a molding method such as injection molding, press molding, and 2P method.

FIG. 8 is a view for explaining an example of a conventional mold manufacturing method, and shows a state in which a mold for forming a microlens array is manufactured by pushing a punch having a spherical tip. . In FIG. 8, reference numeral 42 denotes a punch,
43 is a mold substrate, and 44 is a lens type. This method
This is a technique disclosed in Japanese Patent Application Laid-Open No. 3-288802, in which each lens mold is formed by vertically pushing a punch into a metal substrate that moves intermittently at a desired pitch. By using this mold for injection molding, press molding, and 2P method, it is possible to form a microlens array. According to this method, the NA of the molded product can be controlled by changing the radius of curvature of the spherical surface of the punch to be pressed or the lens diameter by changing the pressing amount (depth).

[0004]

However, when fabricating a microlens array by the above method, it has been found that the metal displaced by the punch adversely affects adjacent lenses. That is, a one-dimensional microlens array having 20 lenses and a lens pitch of 125 μm was manufactured by the above method so that each lens was in contact with the lens. As a result, the lens diameter in the array direction was 120 μm (± 2 μm).
m), and the lens diameter in the direction perpendicular to the array is 115 μm (± 1
μm), and the lens shape became elliptical. this is,
When making a molding die, the pushed-in spherical material pushes the displaced substrate material to the edge of the lens mold (thus deepening as a molded lens), and in the array direction, it is affected by both adjacent lens molds. It is considered that the swell was further increased, and the molded lens ends came into immediate contact.

[0005] Such a horizontally long elliptical lens causes a decrease in the incident area of the light source. Also, the lens N
A differs depending on the angle, and the image is blurred. Furthermore, when the punch is pushed in, pressure is applied in the direction of the lens array, thereby increasing the distortion and causing the radius of curvature to vary greatly in the vertical and horizontal directions. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to solve the above-mentioned problems and to provide a molding die capable of stably molding a high-precision microlens array.

[0006]

According to a first aspect of the present invention, there is provided a mold for forming a microlens array, wherein a mold used for forming a microlens array in which a plurality of lenses are arranged is formed using a metal substrate. The method of manufacturing a microlens array molding die, comprising a lens mold forming step of forming a lens mold on the metal substrate by pushing a punch having a spherical tip into the metal substrate. Before the mold forming step, a concave part forming step of forming a concave part in the mold substrate is added, and in the lens mold forming step, the punch is pressed into the concave part provided in the concave part forming step. The feature is that, when forming a lens mold using a punch, the metal protrusion formed by being pushed away by the punch is reduced to such an extent that the lens is not affected. Can be, thereby, in which mold can be manufactured lens array of high precision stable is to be obtained.

According to a second aspect of the present invention, in the first aspect of the present invention, the step of forming the concave portion is characterized in that the concave portion is formed as a linear groove. It is made possible.

According to a third aspect of the present invention, in the second aspect of the present invention, the concave portion forming step includes forming the grooves in a lattice pattern, and the step of forming a concave portion for forming a two-dimensional lens array is performed. It is designed to be implemented rationally.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the concave portion forming step includes forming the concave portion by pressing a predetermined mold, and further comprising the concave portion forming step and the lens mold. Between the forming step, characterized by adding a polishing step of removing the raised portion of the mold substrate around the concave portion formed in the concave portion forming step by polishing,
A specific method for forming the concave portion is provided.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the concave portion forming step includes forming the concave portion by photolithography.
A specific method for forming the concave portion is provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method of manufacturing a microlens array in which a plurality of lenses are arranged by pressing a punch having a spherical tip into a mold. A concave portion is provided at the position where the mold is formed, and a spherical punch is pressed into the concave portion to produce a mold for forming a microlens, thereby preventing an extra mold substrate bulge due to punching. is there. At this time, in the case of a mold for a one-dimensional microlens array, a linear groove is previously provided in the mold substrate as the concave portion, and a sphere is pressed into the groove to obtain a lens mold. In the case of a mold for a microlens array in which a plurality of lenses are two-dimensionally arranged, a lattice-shaped groove is provided in advance on the mold substrate as the concave portion, and a sphere is pressed into an intersection of the lattice. Obtain a lens mold. In addition, the above-mentioned groove may be formed by pushing in a mold and then processing an excessively raised portion by polishing, or may be formed by photolithography. According to each of the above-described methods, it is possible to prevent extra mold substrate protrusion due to punching, so that the influence of adjacent lens molds can be reduced and a high-precision microlens array can be stably obtained.

Hereinafter, embodiments of the present invention will be described more specifically with reference to the accompanying drawings. The present invention is not limited to these embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIGS. 1 (A) to 1 (C) illustrate a process of manufacturing a microlens array molding die in order.
This is shown conceptually in FIG. In FIG. 1, reference numeral 1 denotes a first punch, 2 denotes a second punch, 3 denotes a mold substrate, 4a denotes a spherical concave portion, 4b denotes a lens type, and 5 denotes a substrate raised portion. FIG.
FIG. 1 is a perspective view conceptually showing a microlens array molding die obtained by a die manufacturing method of the present invention. This embodiment uses a first punch 1 having a ruby sphere having a radius of curvature of 100 μm at the tip and a mold substrate 3 and a spherical concave portion 4a.
Is formed, and then the lens mold 4b is formed.

First, as shown in FIG. 1 (A), the first punch 1 is pressed into
A spherical recess 4a of about μm is formed. And mold substrate 3
Is moved in the X direction at a pitch of 125 μm, and similar processing is performed several times. Then, the raised portion 5 of the substrate formed by pressing the first punch 1 is scraped off by CMP (Chemical Mechanical Polishing) to obtain the form shown in FIG. 1B. At this time, for example, fumed silica (particle diameter: 0.04 nm) is used as the slurry.

Thereafter, as shown in FIG. 1C, the second punch 2 converted into a ruby sphere having a radius of curvature of 125 μm is pushed into the spherical concave portion 4 a of the mold substrate 3 by about 16 μm, and the diameter is about 125 μm. Is formed. Then, the same process is performed several times at a pitch of 125 μm by moving the mold substrate in the X direction. When manufacturing a two-dimensional microlens array molding die, the first punch and the second punch are used.
Are performed in several rows in the XY directions.
FIG. 2 shows a two-dimensional microlens array molding die.

Using this mold for molding a microlens array, PMMA was injection-molded and the microlens array produced was measured for wavefront aberration. As a result, an average RMS of about 0.04λ was obtained. It was found that fewer lenses were made.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 4 is a view for explaining the embodiment, and conceptually shows a means for forming a groove in a mold substrate. In FIG. 3, 1
1 is a mold, 13 is a mold substrate r is a radius of curvature at the tip of the mold.
FIG. 4 conceptually shows a state in which a groove is formed in a mold substrate using the groove forming means shown in FIG. 3. In FIG. 4, reference numeral 14a denotes a groove, 15 denotes a substrate raised portion, and The same elements as those shown in FIG. 3 are denoted by the same reference numerals as those in FIG.
FIG. 5 is a view conceptually showing a state where a groove obtained by the process shown in FIG. 4 is further processed to form a lens mold. In the figure, reference numeral 12 denotes a punch, 14b denotes a lens form, and other figures. 4 are given the same reference numerals as in FIG.

The mold 11 is made of a cemented carbide mainly composed of WC, and has a radius of curvature r of 100 μm at the tip of the mold. The mold substrate 13 is made of Al, and its surface is mirror-finished with Ra of about 3 nm. When forming the groove 14a in the mold substrate 13, first, FIG.
As shown in FIG. 4, the mold 11 is pressed into the mold substrate 13 by about 3 nm to form a groove 14a having a width of about 50 nm.
As shown in (B), the raised substrate 15 raised by pressing the mold 11 is scraped off by CMP.

Next, as shown in FIG.
The punch 12 on which a 25 μm ruby ball is placed is placed on the mold substrate 1.
3 into a lens mold 14b having a diameter of about 125 μm. Then, the mold substrate 13 is set to 125 μm.
By moving in the X direction at m pitches, a mold for forming a one-dimensional microlens array having 20 lenses is manufactured. In the microlens array manufactured by injection-molding PMMA using the microlens array molding die, the lens diameter is calculated in the array direction / array vertical direction =
It was improved to 121 (± 1) / 120 (± 1) μm, and the wavefront aberration was also reduced to about 0.04λ on average.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
FIG. 10 is a perspective view conceptually showing a mold substrate in which grooves having a width of about 10 μm are formed in a grid pattern using the mold 11 of the second embodiment. FIG.
In the figure, 23 is a mold substrate, 24a is a groove, and the pitch of the lattice formed by the groove 24a is 40 μm. Since such a groove 24a is formed, the substrate protrusion of each of the above-described embodiments is not formed when the mold 11 is pressed. At this time, the substrate material is made of, for example, pre-hardened steel, and the surface is mirror-finished with Ra of about 3 nm.

Then, using the second punch 2 with the ruby sphere described in the first embodiment, a pressing process is performed at the intersection of the lattices to form a two-dimensional microlens array as shown in FIG. Was manufactured. Using this mold for forming a microlens, press molding of a microlens array was performed using a SF-based flat glass material having a transition point of 430 ° C. The formed microlens array had little distortion, and when the wavefront aberration was measured by an interferometer, an average value of about 0.05λ was easily obtained by RMS.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
FIGS. 7A to 7D illustrate a process of forming a groove in a mold substrate by photolithography in order.
This is conceptually shown in FIG. In FIG.
33 is a mold substrate, 34a is a groove, and 36 is a photoresist. The mold substrate 33 is made of Al. In forming the groove, first, as shown in FIG. 7A, a photoresist 36 applied to the entire surface of the mold substrate 33 is exposed to a mask having the same length as the microlens array and a width of 50 μm, and then developed. After that, the resist in the exposed portion is removed to obtain a state shown in FIG. Thereafter, the mold substrate 33 is wet-etched by about 3 μm with a mixed acid aluminum solution to form a groove 34 a to be in a state shown in FIG.
Further, the remaining resist is removed to obtain a state shown in FIG.

Thereafter, the second embodiment described in the first embodiment
Lens mold 1 as shown in FIG.
4b is formed. When a microlens array of PMMA was produced by injection molding using the obtained mold for microlens array molding, the same effects as in the second embodiment were obtained.

[0024]

According to the first aspect of the present invention, when a mold for molding a microlens array in which a plurality of lenses are arranged is manufactured by pressing a punch having a spherical tip, a lens on a mold substrate is previously prepared. By providing the concave portion at the position where the mold is formed, it is possible to reduce the metal raised portion formed by being pushed away by the punch to the extent that it does not affect the lens when forming the lens mold with the punch. Thus, a molding die capable of stably producing a high-precision lens array is obtained.

Effect of Claim 2 In addition to the effect of Claim 1, by forming the concave portion as a groove, the step of forming the concave portion can be rationally performed.

According to the third aspect of the present invention, in addition to the effect of the second aspect, a step of forming a concave portion for forming a two-dimensional lens array can be rationally performed.

Effects of Claims 4 and 5: Claims 1 to 3
In addition to any one of the effects, a specific method for forming the concave portion is provided.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 is a perspective view conceptually showing a mold for forming a microlens array obtained by the mold manufacturing method of the present invention.

FIG. 3 is a view for explaining a second embodiment of the present invention, and is a view conceptually showing a means for forming a groove in a mold substrate.

FIG. 4 is a diagram conceptually showing a state in which a groove is formed in a mold substrate using the groove forming means shown in FIG.

FIG. 5 is a diagram conceptually showing a state in which a groove obtained by the process shown in FIG. 4 is further processed to form a lens mold.

FIG. 6 is a diagram for explaining a third embodiment of the present invention.

FIG. 7 is a diagram for explaining a fourth embodiment of the present invention.

FIG. 8 is a view for explaining an example of a conventional mold manufacturing method.

[Explanation of symbols]

1 ... first punch, 2 ... second punch, 3, 13, 2
3, 33, 43: mold substrate, 4a: spherical concave portion, 4b, 1
4b, 44: lens type, 5, 15: substrate bulging portion,
11 ... type, 12, 42 ... punch, 14a, 24a, 34
a: groove, 36: photoresist, r: radius of curvature at the tip of the mold.

Claims (5)

[Claims] 1. A method for manufacturing a mold for forming a microlens array, wherein a mold used for forming a microlens array in which a plurality of lenses are arranged is manufactured using a metal substrate. On the other hand, in the method for manufacturing a microlens array molding die having a lens mold forming step of forming a lens mold on the metal substrate by pushing a spherical punch at the tip, before the lens mold forming step,
Adding a recess forming step of forming a recess in the mold substrate,
The method for manufacturing a microlens array molding die, wherein the punch is pressed into the concave portion provided in the concave portion forming step in the lens die forming step. 2. The method according to claim 1, wherein in the recess forming step, the recess is formed as a linear groove. 3. The method according to claim 2, wherein in the recess forming step, the grooves are formed in a lattice shape. 4. The recess forming step includes forming the recess by pressing a predetermined mold, and further forming the recess in the recess forming step between the recess forming step and the lens mold forming step. 2. A polishing step for removing a raised portion of the surrounding mold substrate by polishing.
4. The method for producing a microlens array molding die according to any one of items 3 to 3. 5. The method according to claim 1, wherein in the recess forming step, the recess is formed by photolithography.
4. The method for producing a microlens array molding die according to any one of items 3 to 3.