JP2005205860A - Method for production of optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance heating efficiency, lessen energy consumption and reduce the occurrence of residual stress or strain in a molded article in a method for production of an optical element. <P>SOLUTION: The optical element production method of this invention comprises the steps of: arranging a thermoplastic resin 2 in the separation molds (5, 6) one of which is formed of a translucent material; irradiating the resin 2 with an energy beam 10 such as a visible or near infrared radiation from the side of the translucent mold 6 while controlling a mold temperature at a predetermined one ranging from the glass transition point of the resin 2 to (that point-20°C); compressing the resin by the molds in such a state that the temperature of the fine uneven surface (projection 5a) of a transfer mold 5 is the glass transition point or higher to transfer the uneven shape to the surface of the resin 2; curing the resin 2 while controlling the mold temperature in a predetermined level to release from the mold. According to the method, the portion to be heated by the energy beam can extremely be lessened, and the molding with good heating efficiency and high accuracy can be attained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical element having a fine uneven surface using a thermoplastic resin as a base material.

  Conventionally, in this type of optical element manufacturing method, a material that transmits infrared light is inserted between a mold that absorbs infrared light and a pressure mold that transmits infrared light, and infrared light is directed from the pressure mold side toward the mold side. A method of forming an optical element by irradiating and pressurizing is known (see Patent Document 1). In this method, energy loss is small to some extent, and the molding cycle can be shortened.

However, in the method described in Patent Document 1, the entire mold is heated, the base material is melted by the heat conduction, and the shape is transferred. Therefore, the heating efficiency is not good, and the amount of energy increases. The apparatus becomes large, or it takes a long time for heating and cooling. Further, since the entire molded product is solidified and contracted during cooling and solidification, there is a problem that residual stress and distortion are likely to occur in the molded product.
JP-A-57-70608

  The present invention has been made in order to solve the above-described problems, and is an optical element that has good heating efficiency, requires a small amount of energy, and reduces the occurrence of residual stress and distortion in a molded product. An object is to provide a manufacturing method.

  In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a thermoplastic resin as a base material is placed in a separation mold that is opened and closed, and a fine irregular surface formed on one mold surface is formed by the thermoplastic resin. A method of manufacturing an optical element formed by transferring to a resin, wherein a resin supply step of disposing a thermoplastic resin in a separation mold in which at least one mold is made of a translucent material, and a separation mold While controlling the mold temperature to the glass transition temperature of the thermoplastic resin to a predetermined temperature in the range of −20 degrees of the temperature, energy rays such as visible or near-infrared light from the mold side made of a translucent material The resin transfer process of transferring the uneven surface to the surface of the thermoplastic resin by compressing with a separation mold in a state where the fine uneven surface is set to a temperature equal to or higher than the glass transition temperature by irradiating, and the mold temperature of the separation mold The thermoplastic resin is hardened while being controlled at a predetermined temperature. It is allowed, and is obtained by a resin mold releasing step of releasing the separation type.

  According to a second aspect of the present invention, in the method for manufacturing an optical element according to the first aspect, in the resin transfer step, a laser is used as an energy beam, and the focal point of the laser is close to the concave / convex surface in the transfer mold having the concave / convex surface. This is the depth position.

  According to a third aspect of the present invention, in the method of manufacturing an optical element according to the first aspect, the separation mold is composed of a translucent mold provided with a translucent material and a transfer mold provided with fine uneven surfaces, and a resin. In the transfer process, the temperature of the translucent mold is controlled to be lower than the temperature of the transfer mold, and a temperature gradient is provided in the mold thickness direction.

  According to a fourth aspect of the present invention, in the method for manufacturing an optical element according to the first aspect, the transfer mold having a fine uneven surface is provided with a translucent material, and an energy beam is applied from the transfer mold side in the resin transfer step. Irradiation.

  According to the first aspect of the present invention, since the fine uneven surface of the mold is set to a temperature equal to or higher than the glass transition temperature by irradiation with energy rays in a state where the separation mold is at a temperature near the glass transition point, only a small amount of energy rays are irradiated. Since the resin can be shaped with no solidification shrinkage of the entire molded product, it becomes difficult to cause cracks in the molded product at the time of mold release and can be molded with high accuracy.

  According to the second aspect of the present invention, the heating portion by the laser can be suppressed to be minute, so that the heating efficiency is good.

  According to the invention of claim 3, by providing the temperature difference in the thickness direction of the separation mold, it is possible to locally heat only the transfer side surface layer, and the heating efficiency is improved.

  According to invention of Claim 4, only the transfer surface layer of a thermoplastic resin can be heated more than a glass transition temperature with an energy ray, and heating efficiency is good.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of an optical element manufactured by the method of the present invention. The optical element 1 is an optical waveguide substrate (cladding) formed by transferring a fine uneven surface to a light-transmitting thermoplastic resin 2 as a base material. Here, the optical waveguide 3 is an optical branch. Has a splitter structure. The width of the recess forming the optical waveguide 3 is about 10 μm or less, and a core material (not shown) having a higher refractive index than that of the cladding is inserted into the recess, and the substrate is covered with a cover cladding.

  2A shows a schematic configuration of a mold apparatus to which the optical element manufacturing method according to the first embodiment is applied, FIG. 2B shows an energy beam irradiation state on the transfer mold, and FIG. 2C and FIG. The structure of a plane and a side is shown. The mold apparatus is mainly composed of a separation mold composed of a transfer mold 5 and a transmission mold 6 which can be freely opened and closed, in which a thermoplastic resin 2 as a base material is inserted. The transfer mold 5 has a fine concavo-convex shape to be transferred to the thermoplastic resin on the surface of the mold, and in the drawing, this fine concavo-convex shape is schematically represented by a convex portion 5a for easy understanding of the inventive concept. Represents. The convex portion 5a is used to transfer and form the concave portion forming the optical waveguide 3 of the optical element 1 shown in FIG. The transmissive mold 6 is made of a light transmissive material for irradiating an arbitrary energy ray 10 to the transfer portion. Each type includes heaters 7 and 8, a cooling water passage (not shown), and a temperature sensor 9 inside, and the temperature is controlled according to each stage of the manufacturing process (details will be described later). Further, the transfer mold 5 and the transmission mold 6 have a configuration for applying a pressing force from above and below in order to position, fix and compress the inserted thermoplastic resin.

  Examples of the thermoplastic resin 2 include PMMA, PC, and COC. The material of the transmission type 6 varies depending on the wavelength of the energy beam 10, and examples include calcium fluoride and sapphire in the ultraviolet region, glass in the visible / near infrared region, and silicon in the far infrared region. The temperature of the separation type is set within the range of the glass transition temperature of the thermoplastic resin 2 to the glass transition temperature of −20 ° C. The temperature control of the separation mold is particularly important because it is related to the mold release failure at the time of mold release, and when the temperature of the mold is higher than the glass transition temperature, the deformation of the thermoplastic resin is not good at the time of mold release. When the temperature of the separation mold is set to a temperature lower than the glass transition temperature −20 ° C., the thermoplastic resin breaks at the time of mold release. The temperature control of the separation mold is performed using the cooling water passing through the mold, the heaters 7 and 8, and the temperature sensor 9.

  The energy beam 10 is irradiated to a region having a fine shape (convex portion 5a) at the time of transfer, the temperature of the thermoplastic resin 2 of the energy beam irradiation unit 10a is increased to the glass transition temperature or more, and the energy beam 10 is separated by compression of the separation type. The fine shape is transferred to the portion of the thermoplastic resin 2 irradiated with. In this way, by irradiating only the region having a fine shape with the energy beam 10, it is possible to suppress a dimensional change due to shrinkage of the entire molded product. After being compressed by the separation mold for a time sufficient for transfer, the irradiation with the energy beam 10 is stopped, and the temperature of the fine shape is cooled to the range of the glass transition temperature to −20 ° C. to release the mold. Thereby, a molded product with few mold release defects is obtained.

  FIG. 3 shows the procedure of the entire manufacturing process in the present embodiment. In this embodiment, in a state where the predetermined mold temperature control (# 4) is performed, energy beam irradiation (# 5) is performed to locally increase the temperature of the transfer region, and transfer by mold compression (# 6) is performed. Then, energy beam irradiation is stopped (# 7), and mold release (# 9) is performed in a state where predetermined mold temperature control (# 8) is performed. By passing through such a process, only a small amount of energy rays are irradiated, so that there is no solidification shrinkage of the entire molded product, cracking or the like hardly occurs in the molded product at the time of mold release, and the resin can be molded with high accuracy.

  4A shows a schematic configuration of a mold apparatus to which the optical element manufacturing method according to the second embodiment is applied, FIG. 4B shows an energy beam irradiation state on a transfer mold in the case of a scanning method, and FIG. 4C shows a masking method. The mask in the case of. The same description as above will be omitted (the same applies hereinafter). In this embodiment, the laser beam 11 is used as the energy beam. As the laser, a YAG laser capable of irradiating near infrared light, a semiconductor laser capable of irradiating visible light, or the like is used. The transmission type 6 is made of glass that transmits near-infrared light or visible light, and the thermoplastic resin 2 is made of a material that easily transmits near-infrared light and visible light. The transfer mold 5 is made of a material that absorbs laser light and generates heat, and can be processed in a fine shape. For example, steel materials, copper, nickel, silicon and the like can be mentioned.

  As a laser irradiation method, the spot diameter 11a is adjusted to the fine-shaped convex part 5a, and the laser light or the base material is moved by scanning to irradiate only the fine-shaped part, or the spot diameter of the laser light has a fine shape. The area is expanded to cover the entire area, and only the fine shape is irradiated with the laser beam by masking with the mask 12 having the opening 12a attached to the transmission mold 6. In this way, by preventing the laser from being irradiated to the non-transfer area, it is possible to suppress the area heated by the laser to be small, so that the shrinkage that occurs in the non-transfer area can be prevented, and the fine shape of the molded product can be prevented. It is possible to eliminate the thermal stress due to the in-mold constraint of the part. Further, by setting the focal position of the laser to a depth of 0.5 to 3.0 times the fine shape height in the transfer mold 5, the mold surface portion to be heated most efficiently can be efficiently heated.

  FIG. 5 shows a schematic configuration of a mold apparatus to which an optical element manufacturing method according to a modification of the second embodiment is applied. In this modification, a thermoplastic resin 2 that easily absorbs laser light is used. The type of laser light can be selected from far infrared light and ultraviolet light. For the transmission type 6, silicon that transmits far-infrared light, calcium fluoride that transmits ultraviolet light, sapphire, or the like is used. The transfer mold 5 is made of a fine material that can be processed. For example, glass, steel, copper, nickel, silicon, etc. are mentioned. The laser irradiation method is the same as in the second embodiment. Even in this case, the most heated portion can be efficiently heated.

  FIG. 6 shows a schematic configuration of a mold apparatus to which the optical element manufacturing method according to the third embodiment is applied. In this embodiment, the temperature of the separation mold is controlled in the range from the glass transition temperature of the thermoplastic resin 2 to the glass transition temperature of −20 ° C., and the temperature of the transmission mold 6 is controlled to be lower than the temperature of the transfer mold 5. . For example, when PMMA is used for the thermoplastic resin 2, the glass transition temperature is 110 ° C., the temperature of the transmission mold 6 is controlled to 95 ° C., and the temperature of the transfer mold 5 is controlled to 105 ° C. Thus, the surface temperature of the thermoplastic resin 2 is 105 ° C. on the transfer mold 5 side and 95 ° C. on the transmission mold 6 side, and has a temperature gradient in the thickness direction. In this state, when the near-infrared light is irradiated to the thermoplastic resin 2 using the energy beam 10, the transfer surface side region A of the thermoplastic resin 2 is equal to or higher than the glass transition temperature, whereas the transmission type 6 side is It becomes below a glass transition temperature, and suppression of the thermal stress in the permeation | transmission side of the thermoplastic resin 2 etc. is attained.

  FIG. 7 shows a schematic configuration of a mold apparatus to which the optical element manufacturing method according to the fourth embodiment is applied. In this embodiment, a normal mold 15 and a transmission / transfer mold 16 for transmission and transfer on the irradiation side of the energy beam 10 are used as the separation mold. A far-infrared region is used for the wavelength of the energy beam 10, and the transmission / transfer mold 16 is made of silicon that transmits light in the far-infrared region well. The thermoplastic resin 2 is made of a material that easily absorbs far infrared wavelengths. The temperature of the separation mold is controlled between a temperature lower than the glass transition temperature and a temperature 20 ° C. lower than the glass transition temperature. For example, when PMMA is used for the thermoplastic resin 2, the glass transition temperature is 110 ° C., and the temperature of the separation mold is controlled to 100 ° C. By irradiating the energy ray 10 to the thermoplastic resin 2 through the transmission / transfer mold 16, only the region A of the transfer surface layer of the thermoplastic resin 2 is heated above the glass transition temperature, and heat is generated by compressing the separation mold. A fine shape can be transferred to the plastic resin 2. Thus, by locally heating only the transfer surface side of the resin to the glass transition temperature or higher, the thermal stress due to the shrinkage of the non-transfer portion can be eliminated.

  FIG. 8A shows a schematic configuration of a mold apparatus to which the optical element manufacturing method according to the fifth embodiment is applied, and FIGS. 8B and 8C show a plane and side surfaces of the transfer mold. In the present embodiment, a mold in which Ni and Cr are coated on the fine uneven surface of the transfer mold 5 is used. Examples of the energy ray include near infrared light, far infrared light, visible light, and ultraviolet light. Examples of the material of the transmission type 6 include glass for near infrared light and visible light, silicon for far infrared light, and calcium fluoride and sapphire for ultraviolet light. The transfer mold 5 is made of steel, copper, nickel, silicon, or the like, which can easily process a fine shape, and Ni, Cr, etc. are coated on the surface of the fine shape. When the energy line 10 is irradiated to the fine shape portion of the transfer mold 5 through the transmission mold 6 and the thermoplastic resin 2, it is absorbed by the coating material and generates heat, and the transfer surface side of the thermoplastic resin 2 is concentrated on the glass transition. It can be heated to a temperature higher than that, and a fine shape can be transferred by compressing the separation mold.

  FIG. 9A shows a schematic configuration of a mold apparatus to which an optical element manufacturing method according to a modification of the fifth embodiment is applied, and FIGS. 9B and 9C show a plane and side configuration of a transmission / transfer mold. Similar to the fourth embodiment, this modification uses a normal mold 15 as a separation mold and a transmission / transfer mold 16 for transmission and transfer on the irradiation side of the energy beam 10, and the fine uneven surface of the transmission / transfer mold 16 is used. A die coated with Ni and Cr was used. Examples of the wavelength of the energy beam 10 include near infrared light, far infrared light, visible light, and ultraviolet light. Examples of the material of the transmission / transfer mold 16 include glass for near infrared light and visible light, silicon for far infrared light, and calcium fluoride and sapphire for ultraviolet light. By irradiating the energy beam 10 through the transmission / transfer mold 16, the coating layer on the surface of the transmission / transfer mold 16 absorbs the energy beam 10, generates heat, and compresses the separation mold to form a fine shape on the thermoplastic resin 2. Can be transferred. In this way, since only the finely shaped portion can be heated, shrinkage of the entire molded product can be suppressed.

  In addition, this invention is not restricted to the said embodiment, Various deformation | transformation are possible. For example, in the present embodiment, the example in which the thermoplastic resin 2 is charged and arranged in the separation mold is shown, but the molten resin may be injected into the mold.

The perspective view which shows an example of the optical element manufactured by the method of this invention. (A) is a schematic block diagram of the type | mold apparatus with which the manufacturing method of the optical element by Example 1 is applied, (b) is a top view which shows the irradiation state of the energy beam to a transfer type | mold, (c) is a plane of a transfer type | mold. FIG. 4D is a side view of the transfer mold. The figure which shows the procedure of the whole manufacturing process in a present Example. (A) is a schematic block diagram of the type | mold apparatus with which the manufacturing method of the optical element by Example 2 is applied, (b) is a top view which shows the irradiation state of the energy beam | light to a transfer type | mold in the case of a scanning system, (c). Is a plan view of a mask in the case of a masking method. FIG. 10 is a schematic configuration diagram of a mold apparatus to which the method for manufacturing an optical element according to Example 3 is applied. FIG. 10 is a schematic configuration diagram of a mold apparatus to which the method for manufacturing an optical element according to Example 3 is applied. FIG. 10 is a schematic configuration diagram of a mold apparatus to which the method for manufacturing an optical element according to Example 4 is applied. (A) is a schematic block diagram of the type | mold apparatus with which the manufacturing method of the optical element by Example 5 is applied, (b) is a top view which shows the irradiation state of the energy beam to a transfer type | mold, (c) is a side surface of a transfer type | mold. Figure. (A) is a schematic block diagram of the type | mold apparatus with which the manufacturing method of the optical element by the modification of Example 5 is applied, (b) is a top view which shows the irradiation state of the energy beam to a transmission and transfer type | mold, (c). Is a side view of a transmission / transfer mold.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical element 2 Thermoplastic resin 5 Transfer type (separation type)
5a Convex part 6 Transmission type (separate type)
10 energy beam 11 laser beam 15 type 16 transmission / transfer type

Claims (4)

A method of manufacturing an optical element formed by inserting a thermoplastic resin as a base material into a separation mold that is opened and closed, and transferring a fine uneven surface formed on one mold surface to the thermoplastic resin Because
A resin supply step of disposing a thermoplastic resin in a separation mold in which at least one mold is made of a translucent material;
While controlling the mold temperature of the separation mold to a predetermined temperature in the range of the glass transition temperature of the thermoplastic resin to −20 degrees of the temperature, visible or near infrared light or the like from the mold side made of a translucent material A resin transfer step of transferring the uneven surface to the surface of the thermoplastic resin by compressing with a separation mold in a state where the fine uneven surface is set to a temperature equal to or higher than the glass transition temperature by irradiating
A method for producing an optical element, comprising: a resin mold release step of curing the thermoplastic resin in a state in which a mold temperature of a separation mold is controlled to a predetermined temperature and releasing the mold from the separation mold.   2. The optical element according to claim 1, wherein, in the resin transfer step, a laser is used as an energy ray, and a laser irradiation focus is set to a depth position close to the uneven surface in the transfer mold having the uneven surface. Manufacturing method. The separation mold is composed of a translucent mold provided with a translucent material and a transfer mold provided with a fine uneven surface,
2. The method of manufacturing an optical element according to claim 1, wherein the temperature of the translucent mold is controlled to be lower than the temperature of the transfer mold in the resin transfer step so as to have a temperature gradient in the thickness direction of the mold. The transfer mold with fine uneven surface has a translucent material,
2. The method of manufacturing an optical element according to claim 1, wherein energy rays are irradiated from the transfer mold side in the resin transfer step.

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