JP2001179824A - Method for manufacturing mold for microlens array and manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive a molding process method so that the variability of process precision is diminished as much as possible without depending upon a special processing step such as a finishing process with regard to the formation of the recessed part of a mold for molding a microlens array with the help of a punch. SOLUTION: The method for manufacturing a mold for molding the microlens array is to form a plurality of dents by pressing the lower end spherical face of a punch to the surface of the mold for molding the microlens array and transfer the dents formed in the mold to an optical element material. In this method. the punch is pressed while a high frequency oscillation is imparted to the punch in the axial direction when the punch is pressed to the surface of the mold. In addition, when the punch is pressed to the surface of the mold, the punch is pressed while it is rotated. The other choice is that when the punch is pressed to the surface of the mold, the high frequency oscillation is imparted to the punch and at the same time, the punch is pressed while it is rotated.

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 mold for forming a microlens array, and relates to a method for forming a large number of concave portions in a mold for forming a microlens array by pressing the surface of the mold with a punch. The accuracy of each lens forming surface (the inner surface of the concave portion) in the microlens array can be improved, and variations in the accuracy can be suppressed as much as possible.

[0002]

2. Description of the Related Art A microlens array is formed by injection molding, compression molding, casting, or the like, and is used to mold a microlens array having a large number of minute concave portions 61a on its surface (see FIG. 6). There are various production techniques, and one example is described in JP-A-9-323353.

[0003] The above-described mold manufacturing apparatus is as shown in FIG. 7. A punch 72 for sequentially forming a concave portion 61 a in a mold 61 on a stage 71 is movable with permanent magnets 73 and 74 and a coil 75 wound thereon. It is reciprocally driven in the axial direction by a linear motion motor composed of a cylinder 76 and a leaf spring 77. The punch 72 is pressed against the surface of the mold 61 to form an indentation, and the indentations are used to form the above-mentioned many concave portions.
The shape of the concave portion is such that the spherical surface at the lower end of the punch 72 (one form of the transfer surface) is not microscopically an ideal true spherical surface but has a slight distortion. It is not a true spherical surface, but has a slightly distorted shape microscopically. If the direction of this distortion is regular, light transmitted through the microlens array formed by this will have directionality. For this reason, when this micro lens is used for a reticle, it becomes difficult to see the reticle. In this prior art, the motor 78 is used to rotate the spindle 79 of the punch 72 slightly by a predetermined angle before pressing the punch 72 against the mold surface to form individual concave surfaces, thereby sequentially changing the direction of distortion of the concave portion. Things. Further, there is a similar mold forming technique described in Japanese Patent Application Laid-Open No. 9-327860. Although the mold manufacturing apparatus of this is not fundamentally different from the above-mentioned prior art, when the above-mentioned indentation is formed on the mold surface by the punch, the pressing depth of the punch is changed irregularly by a small amount, whereby the micro lens is formed. This is to prevent the generation of moire fringes due to the transmitted light.

The above-mentioned mold forming apparatus has an XY table, and in some cases, further has a turning table thereon, and a stage 71 at the top of the XY table. Is controlled by a computer to control the position of the punch 7 with respect to the mold on the stage 71.
2 is automatically determined, and the punch lowering operation is computer-controlled. Therefore, only by inputting the control data to the computer, the XY table (or the swivel table in some cases) is controlled, and the punch 72 automatically forms the concave portion by the indentation at a predetermined accurate XY position. You. JP-A-9-3
No. 23353 and Japanese Patent Application Laid-Open No. 9-327860 discloses that the microlens is transmitted through the microlens by slightly rotating it by a predetermined angle before pressing with a punch or by slightly changing the pressing depth. The light has no directivity. However, the solution to the above-mentioned problem is based on the premise that the forming accuracy by the punch tip is extremely high and is accurately transferred to the concave surface of the punch tip surface. The technical problem of how to increase the processing accuracy remains unsolved.

[0005]

By the way, in order to improve the processing accuracy of the inner surface of the indentation of the punch of the microlens array molding die using the punch, the processing efficiency for that purpose should not be reduced, and the processing accuracy of the inner surface of each recess must be varied. It is necessary that there is no. Accordingly, the present invention provides a method for forming a concave portion of a microlens array molding die with a punch with high precision without using special processing steps such as finishing processing, so that variations in processing accuracy are minimized. It is an object of the present invention to devise a molding method.

[0006]

[Measures taken to solve the problem]

[MEANS FOR SOLVING PROBLEMS] Means taken for solving the above-mentioned problem is:
A method of manufacturing a microlens array molding die for pressing a transfer surface of a punch against a surface of a microlens array molding die to form a large number of indentations and transferring the indentations formed in the die to an optical element material When pressing the punch against the surface of the mold, the punch is pressed while applying high-frequency vibration to the punch in the axial direction.

[0007]

When the punch is pressed against the surface of the mold, the punch is pressed against the surface of the mold while being ultrasonically vibrated. The concave portion is formed while pressing the punch in multiple stages. Therefore, since the inner surface of the concave portion is machined by repeating the minute machining, the machining accuracy is high. Further, since the application of the high frequency vibration for improving the processing accuracy is performed under the same condition for all the concave portions, the processing accuracy of each concave portion becomes substantially uniform. Since the frequency of the high-frequency vibration depends on the lowering speed of the punch, the processing depth of the concave portion, and the material of the mold, it cannot be specified unconditionally.
For example, 1000 is a rough guideline for a processing depth of 1 mm (processing by one vibration, for example, 1 μm), and 500
The effect of giving high-frequency vibration can be expected even in the range of ~ 600. Note that the above axial vibration is applied to the transfer surface (lower end surface) of the punch.
This is a relative vibration in the punch axial direction between the punch and the surface of the die (working surface), so that it is not always necessary to vibrate the punch. If the stage is vibrated, there is no problem because the mass of the vibrated body is large, but there are advantages such as easy installation of the high-frequency vibration device,
It is also possible to vibrate the stage instead of vibrating the punch.

[0008]

[MEANS FOR SOLVING PROBLEMS] Means 2 taken for solving the above-mentioned problem are:
A method of manufacturing a microlens array molding die for pressing a transfer surface of a punch against a surface of a microlens array molding die to form a large number of indentations and transferring the indentations formed in the die to an optical element material When pressing the punch against the surface of the mold, the punch is rotated and pressed.

[0009]

When the punch is pressed against the surface of the mold, the transfer surface of the punch is pressed into the surface of the mold while rotating about the axis thereof to form a concave portion. Is processed on the entire inner surface of the concave portion. Therefore, even if the shape of the tip surface of the punch is not an ideal shape and is slightly distorted, the distortion is averaged over the entire inner surface of the recess by rotation of the punch, and transfer without bias is performed. The processing accuracy of the inner surface is also improved. Since the rotation speed of the punch depends on the descent speed of the punch, the processing depth of the concave portion, and the material of the mold, it cannot be specified unconditionally, but the processing depth is 1 m.
A rough rule of thumb is 100 times per second per m (processing 10 μm during one rotation), and the effect of applying rotation even at 50 to 60 can be expected.

[0010]

[MEANS FOR SOLVING PROBLEMS] Means 3 taken for solving the above-mentioned problem are:
A method of manufacturing a microlens array molding die for pressing a transfer surface of a punch against a surface of a microlens array molding die to form a large number of indentations and transferring the indentations formed in the die to an optical element material When the punch is pressed against the surface of the mold, high frequency vibration is applied to the punch and the punch is pressed while rotating.

[0011]

Since the solution 3 is a combination of the solution 1 and the solution 2, these functions are simultaneously performed, and the synergistic action of these actions further improves the processing accuracy and makes the processing accuracy uniform. Is achieved.

[0012]

[Embodiment 1] Embodiment 1 is a solution 1 and a solution 2.
Alternatively, in the method for manufacturing a microlens array molding die according to Solution 3, a lubricant is interposed between the transfer surface of the punch and the surface of the die, and the surface to be processed of the die by the transfer surface of the punch is changed. It is to lubricate.

[Action] Regardless of whether high frequency vibration is applied to the punch at the time of press working or rotation is applied, relatively high-speed friction occurs between the transfer surface of the punch and the work surface of the mold. However, since this rubbing is performed through the lubricating film made of the lubricant, the transfer surface of the punch and the surface to be processed of the mold do not rub together, so that the processing resistance is reduced and high-precision transfer is achieved. Done.

[0013]

[Embodiment 2] In the embodiment 2, in the solution 1 to the solution 3, an abrasive having no polishing action on the transfer surface of the punch but having a polishing action on the mold is used. That is, when pressed against the surface of the mold, it was interposed between the transfer surface of the punch and the surface of the mold.

[Action] Even if high frequency vibration in the axial direction is applied to the punch at the time of press working or rotation is applied, the transfer surface of the punch relatively rubs against the work surface of the mold. However, a polishing process using an abrasive is added to the transfer process performed by pressing the punch, whereby fine processing is performed, and the inner surface of the concave portion formed on the mold surface is finished with higher precision.

[0014]

Embodiment 3 In Embodiment 3, at least the lower transfer surface of the punch in Solution 1 to Solution 3 is formed of any material of ceramics, cemented carbide and cermet.

Since the above material has high hardness, there is no plastic deformation of the lower transfer surface of the punch when the punch is pressed against the mold.
Abrasion of the lower transfer surface of the punch can also be suppressed, and the durability of the lower transfer surface of the punch is high, so high-precision transfer can be repeatedly performed. .

[0015]

[Fourth Embodiment] A fourth embodiment is that at least the surface of the lower transfer surface of the punch of the third embodiment is coated with diamond.

With the diamond coating applied to at least the lower transfer surface of the punch, there is no plastic deformation of the lower transfer surface of the punch when the punch is pressed against the mold, and the lower transfer surface of the punch is worn. , The selection range of the mold material and the abrasive to be used is widened, and since the lower end transfer surface of the punch has high durability, high-accuracy transfer can be repeatedly performed.

[0016]

Fifth Embodiment A fifth embodiment relates to a mold manufacturing apparatus for performing the method of manufacturing a microlens array forming mold according to the first to third aspects of the present invention. The punch is provided at the lower end via a high-frequency vibration device that generates axial vibration.

The punch is provided via a high-frequency vibrator which generates axial vibration at the lower end of a spindle which is driven in the rotational direction by a drive motor and is driven in the axial direction by an axial drive device. The force and the axial driving force are transmitted to the punch via the high-frequency vibration device, while the high-frequency vibration device is capable of transmitting the driving force in the rotational direction and the axial direction to the punch without any trouble. is there. Therefore, the driving force in the rotational direction and the axial direction,
The axial driving force can be transmitted to the punch by a simple mechanism.

[0017]

Embodiment 1 Embodiment 1 shown in FIG. 1 is an example in which the invention according to claim 1 is applied to the processing of a stainless steel mold. The stage positioning drive mechanism of the first embodiment is based on an XY table. The axial drive mechanism of the punch 1 may be a direct-acting electromagnetic drive similar to the above-described conventional example.
The entire mold processing apparatus according to the embodiment of the present invention is conceptually shown in FIG. 5 without being limited to the first embodiment, and has X and Y positioning drive motors 52 and 53 on a machine base.
There is a Y table 54 on which a die 5 as a workpiece is placed.
5 is placed and fixed. Above the XY table 54, the spindle 2 of the punch 1 is vertically and slidably and rotatably supported by a bearing B, and is driven by a driving device 56 (the linear driving device 3, the rotary driving device 22). I have to. The material of the punch 1 in which the lower end surface (transfer surface) of the punch 1 is processed into an appropriate shape (spherical shape in the illustrated example) is made of a cemented carbide, and the spindle 2 is slidably guided in a vertical direction by a bearing. And is driven downward by an electromagnetic linear drive device 3. Further, at the lower end of the spindle, a conventionally known high-frequency vibration device 4 for generating an axial vibration is provided.
Is connected to the upper end of the punch 1. The high-frequency vibration device 4 does not need to be special, but may be any device that can adjust the vibration amplitude, vibration frequency, and vibration force. The vibration frequency may be appropriately adjusted in consideration of the workability of the mold, the depth of the indentation by the punch, and the like so that the desired processing accuracy is obtained. However, the vibration force must be adjusted to a driving force that can overcome the driving force of the linear drive device 3. In the first embodiment, when a lubricant is applied to the surface of the mold 55 and pressing is performed by the punch, the lower end surface (spherical transfer surface) of the punch 1 and the mold 5 are pressed.
The lubricant is interposed between the surface 5 and the work surface. This lubricant is not particularly problematic as long as it has a low viscosity and is easy to clean and remove from the surface to be processed of the mold 55, but in this embodiment, the mold 55 is made of stainless steel and a punch is used. Considering that it is a cemented carbide, a water-soluble rolling oil is used as the lubricant. According to the first embodiment, the punch descending speed is 1 mm / sec, and the excitation frequency is 950H.
z, excitation amplitude 0.1 μm, diameter 2 mm, depth 0.
Impressions of 1 mm were formed in the mold at a pitch of 2 mm vertically and horizontally. Using this mold, a microlens array was prepared by injection molding. The accuracy of each lens in the microlens array was significantly higher than that of the prior art, and it was confirmed that the variation in the accuracy was extremely small.

[0018]

Embodiment 2 Embodiment 2 shown in FIG. 2 is an embodiment to which the invention according to Solution 2 is applied. In the second embodiment, the punch 21 formed into an appropriate shape is made of SiC ceramics, and the spindle 2 is guided slidably in the vertical direction by a bearing, similarly to the first embodiment, and the upper end of the spindle is Is provided with a rotary drive motor 22, and a punch 2
1 are directly connected. In the second embodiment, a lubricant is applied to the surface of the mold 55 so that the lubricant is interposed between the lower end surface of the punch 1 and the surface to be processed of the mold 55 during pressing by the punch. ing. This lubricant is not particularly problematic as long as it has a low viscosity and is easy to clean and remove from the work surface of the mold 55, but in this embodiment, the mold 55 is made of stainless steel and Transfer surface is SiC
Considering that it is made of ceramics, a water-soluble rolling oil is used as the lubricant. When the punch 21 is lowered and the die surface is pressed, the spindle 2 is rotated by the rotary drive motor 22 of the driving device 56 (see FIG. 5).
In consideration of the depth of the indentation by the punch and the like, it may be appropriately adjusted so as to obtain a desired processing accuracy. According to Example 2, indentations having a diameter of 1 mm and a depth of 0.5 mm were formed in the mold at a pitch of 1.2 mm vertically and horizontally at a punch descending speed of 0.5 mm / sec and a rotation speed of 60 times / sec. This mold 5
Using No. 5, a microlens array was prepared by injection molding. In this microlens array, the accuracy of each lens in the microlens array was significantly higher than that of the prior art, and it was confirmed that the variation in the accuracy was extremely small.

[0019]

Third Embodiment A third embodiment shown in FIG. 3 is an example in which the invention according to the solution means 3 is applied. The third embodiment includes an electromagnetic linear drive 3 for driving the spindle 2 in the axial direction and a rotary drive 22 for driving the spindle 2 in the rotation direction. Punch 31
Is connected to the upper end. When the spindle 2 is lowered by the linear drive device 3 and the lower spherical surface (transfer surface) of the punch 31 is pressed against the surface (work surface) of the mold 55 to form an indentation, the rotary drive device 22 rotates the spindle 2. 2 is rotated to rotate the punch 31, and the high-frequency vibration device 4 applies high-frequency axial vibration to the punch 31. When the punch 31 is lowered to press the surface of the mold 55, the spindle 2 is rotated by the rotary drive motor 22 of the drive device 56 (see FIG. 5), and the punch 31 is further axially moved by the high-frequency vibration device 4. Vibration is performed, and the rotational speed, the vibration amplitude, and the vibration frequency are appropriately adjusted in consideration of the workability of the mold 55, the depth of the indentation by the punch, and the like, so that the desired processing accuracy is obtained. do it. Punch down speed 0.1mm / sec, excitation frequency 3K
Indentations having a diameter of 3 mm and a depth of 2 mm were formed in the above-mentioned mold at a pitch of 2.8 mm vertically and horizontally at a frequency of 1 Hz, a vibration amplitude of 1 μm, and a rotation speed of 10 times / second. Using this mold 55, a microlens array was formed by injection molding. In this microlens array, the accuracy of each lens in the microlens array was significantly higher than that of the prior art, and it was confirmed that the variation in the accuracy was extremely small. In addition, the accuracy is slightly higher than those according to the first and second embodiments,
It was confirmed that the variation in accuracy was slightly small. In addition,
FIG. 4 is a schematic enlarged view of the punch used in the third embodiment. The punch 31 has a lower end surface formed of Si by CVD.
The C coating layer 31a is formed, the lower surface of the SiC coating layer 31a is processed into a predetermined shape, the transfer surface of which is coated with diamond SiC, and polished (finished) to finish to a required accuracy. . The thickness of the SiC coating layer 31a may if about minimum 0.1mm, but in this example is 0.15 mm. This punch can also be used as the punch in the first and second embodiments. In the third embodiment, when the punch 31 is pressed against the surface of the mold 55, an abrasive is interposed between the punch 31 and the surface of the mold 55. The abrasive has no abrasive action on the punch but has an abrasive action on the mold, and specifically, is an abrasive obtained by mixing alumina abrasive grains and a water-soluble solution. In addition, silica or the like can be used as the abrasive.

[0020]

[Others] Although the high-frequency vibrating device 4 in the first and third embodiments is interposed between the spindle and the punch, the high-frequency vibrating device 4 only needs to vibrate the punch in the axial direction. Therefore, the linear drive device 3 and the rotation drive device 22 can be included in the drive device 56. In this case, it is necessary to devise a special transmission mechanism on the upper part of the spindle that can simultaneously apply an axial vibration force stronger than the axial drive force in addition to the axial drive force and the rotational force. is there.

[0021]

[Effects] The effects of the present invention can be summarized as follows, by arranging the main points of the effects for each invention according to the main claims. 1. When the punch is pressed against the surface of the microlens array molding die while pressing the punch while applying high-frequency vibration in the axial direction, the punch shape is not transferred at a time. In addition, since the pressing process is performed in multiple stages by minute amounts, high transfer accuracy can be obtained.

2. The invention according to claim 2 When the punch is pressed against the surface of the microlens array molding die, by pressing while rotating the punch, the tip shape of the punch is not an ideal shape and is very small. Even if it is distorted, the distortion is averaged over the entire transfer surface of the mold by the rotation of the punch, and transfer without bias is realized.

3. When the punch is pressed against the surface of the microlens array molding die, the punch is applied with ultrasonic vibration and pressed while rotating, so that the punch shape is not transferred at a time, but is fine. High-accuracy transfer is obtained because the pressing process is performed in multiple steps by volume.Also, even if the tip of the punch is not ideally spherical and slightly distorted, the Is averaged over the entire inner surface of the concave portion of the mold by the rotation of the punch, and transfer without deviation is realized, and a synergistic effect of the two effects provides higher transfer accuracy.

4. When the punch is pressed against the surface of the microlens array molding die, a lubricant is interposed between the punch and the surface of the die to lubricate the work surface of the die by the punch. As a result, the transfer surface of the punch and the surface to be processed of the mold do not gallate, and therefore, the processing resistance is reduced, and high-accuracy transfer is performed.

[5] In the invention according to claim 5, when the punch is pressed against the surface of the microlens array molding die, there is no polishing action on the transfer surface of the punch between the punch and the die surface, but the die has By interposing a polishing agent with a polishing action on the work surface of the mold,
Since a polishing process using an abrasive is added to the transfer process by pressing the punch, fine processing is performed by this,
The inner surface of the concave portion on the mold surface is finished with higher precision.

6. In the invention according to claim 6, since at least the lower transfer surface of the punch is formed of any one of ceramics, cemented carbide, and cermet, the punch is pressed against the mold because these materials have high hardness. Sometimes there is no plastic deformation of the punch, the wear of the lower transfer surface of the punch can be suppressed, and the durability of the lower transfer surface of the punch is high, so it is possible to repeat high-precision transfer. The choice of materials and abrasives is expanded.

7. Regarding the invention according to claim 7, by applying diamond coating to at least the lower end surface of the punch, there is no plastic deformation of the lower end transfer surface of the punch when pressing the lower end transfer surface of the punch against the surface of the mold, and Abrasion can also be suppressed, so that a wider range of choices can be made regarding the material of the mold and the abrasive, and since the punch has high durability, high-accuracy transfer can be performed repeatedly.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a main part of a first embodiment.

FIG. 2 is a schematic front view of a main part of a second embodiment.

FIG. 3 is a schematic front view of a main part of a third embodiment.

FIG. 4 is a schematic enlarged view of a punch in a third embodiment.

FIG. 5 is a schematic front view of an apparatus for manufacturing a microlens array molding die according to an embodiment.

FIG. 6 is a perspective view of a microlens array molding die on which indentations are formed.

FIG. 7 is a sectional view of a main part of a conventional example of a microlens array molding die manufacturing apparatus.

[Explanation of symbols]

1, 21, 31: punch 2: spindle 3: linear drive 4: high frequency vibrator 22: rotary drive 31a: SiC coating layer 55, 61: microlens array forming die 61a: microlens array forming die Many recesses formed on the top of the mold

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Kai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Zhang Army 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 4F202 AH74 CA01 CA09 CA11 CB01 CD02 CD25 CD30 4F209 AH74 PB01 PC05 PQ11

Claims (13)

[Claims] 1. A microlens array molding method in which a transfer surface of a punch is pressed against a surface of a microlens array molding die to form a large number of indentations, and the indentations formed in the die are transferred to an optical element material. In the method for manufacturing a mold, a method for manufacturing a microlens array forming mold, wherein the punch is pressed while applying high-frequency vibration in the axial direction to the punch when the punch is pressed against the surface of the mold. 2. A microlens array molding method in which a transfer surface of a punch is pressed against a surface of a microlens array molding die to form a large number of indentations, and the indentations formed in the die are transferred to an optical element material. In the method for manufacturing a mold, a method for manufacturing a mold for forming a microlens array in which the punch is pressed while rotating the punch when the punch is pressed against the surface of the mold. 3. A microlens array molding method in which a transfer surface of a punch is pressed against a surface of a microlens array molding die to form a large number of indentations, and the indentations formed in the die are transferred to an optical element material. In the method for manufacturing a mold, a method for manufacturing a microlens array molding die, in which when the punch is pressed against the surface of the die, high-frequency vibration is applied to the punch and the punch is rotated and pressed. 4. The mold according to claim 1, wherein a lubricant is interposed between the punch and the surface of the mold to lubricate the work surface of the mold by the transfer surface of the punch. 3. The method for producing a microlens array molding die according to 3. 5. A punch and a mold which are not polished to the transfer surface of the punch but have an abrasive action to the die when the punch is pressed against the surface of the die. 4. The method of manufacturing a microlens array molding die according to claim 1, wherein said mold is interposed between said mold and said surface. 6. The method for manufacturing a microlens array molding die according to claim 1, wherein at least the lower transfer surface of the punch is formed of any one of ceramic, cemented carbide and cermet. . 7. The method for manufacturing a microlens array molding die according to claim 6, wherein a diamond coating is applied to at least a surface of a lower transfer surface of said punch. 8. A mold manufacturing apparatus for carrying out the method for manufacturing a mold for forming a microlens array according to any one of claims 1 to 3, further comprising a mold positioning mechanism using an XY table. A mold manufacturing apparatus provided with a high-frequency vibrating device that applies axial vibration to a spindle driven in the axial and axial directions. 9. The mold manufacturing apparatus according to claim 8, wherein said punch is provided at a lower end of said spindle via said high-frequency vibration device. 10. A ceramic material comprising at least a lower transfer surface.
4. A punch used in the mold manufacturing apparatus for forming a microlens array according to claim 1, wherein the punch is formed of a material selected from a cemented carbide and a cermet. 11. A punch used in an apparatus for manufacturing a mold for forming a microlens array, wherein at least a surface of a lower transfer surface is coated with diamond. 12. A microlens array molding die manufactured by the die manufacturing method according to claim 1. 13. A microlens array manufactured by using the mold according to claim 12.