JP2007277065A - Mold, optical lens, optical apparatus and mold manufacturing method - Google Patents

Abstract

To provide a mold, an optical lens, an optical apparatus, and a mold manufacturing method capable of forming an optical surface for suppressing light reflection at low cost.
A mold for forming an optical surface having a fine concavo-convex surface, which is formed by applying a slurry containing two or more kinds of particles having different melting points to a mold base material and firing the slurry. It has an optical surface formation part, and the said optical surface formation part has the unevenness | corrugation corresponding in order to transfer finely the fine unevenness | corrugation to the said optical surface at random.
[Selection figure] None

Description

  The present invention relates to a mold for forming an optical surface having a fine uneven surface. The present invention relates to a mold suitable for forming an optical surface of an optical element used in a still camera, a video camera, binoculars, and the like, an optical lens molded using the mold, an optical apparatus, and a mold manufacturing method.

  An optical lens has a problem that a ghost due to surface reflection occurs. Particularly, in recent years, since miniaturization has progressed and lenses are arranged close to each other, it is an urgent task to solve such a problem.

  As measures for preventing ghosts, there are known methods such as providing fine irregularities on the surface of an optical lens to suppress light reflection, or performing lens combination and interval adjustment. Regarding the provision of fine irregularities on the surface of the optical lens, there are technologies for creating irregularities with intervals of several hundred nm or more and technologies for producing irregularities with several tens of nm or less, but create irregularities with intermediate intervals. It was difficult.

For example, an optical lens having an antireflection film such as MgF ₂ or SiO ₂ on the optical surface is known (see, for example, Patent Document 1).
JP 7-77730 A (paragraph [0007])

Further, an optical member is known in which a fine periodic structure having a certain period on the optical surface is formed by direct electron beam drawing or reactive ion etching (see, for example, Patent Document 2).
JP 2003-322711 A (paragraph [0028])

Further, a mold having an optical molding surface formed by press molding an amorphous alloy having a supercooled liquid region with a master mold is known (for example, see Patent Document 3).
JP 2002-326232 A (paragraph [0050])

  However, when the antireflection film is applied as described above, it is necessary to apply the antireflection film after molding the optical lens or to attach the antireflection film to a mold, resulting in an increase in manufacturing process and cost. In addition, there are problems such as deformation of the optical member due to heating and poor durability.

  In addition, when the fine periodic structure is directly drawn as described above, it is necessary to process the lens after molding, which increases the manufacturing process and costs.

  Further, when the master mold is used as described above, there is a problem that it is necessary to create a master mold to obtain a mold, which is expensive.

  Accordingly, an object of the present invention is to provide a mold capable of forming an optical surface that suppresses reflection of light at a low cost, an optical lens molded using the mold, an optical apparatus, and a mold manufacture. It is to provide a method.

  The inventors of the present invention have completed the present invention based on a completely different idea.

  In order to achieve the above object, a first aspect of the present invention is a mold for forming an optical surface having a fine uneven surface, and a slurry containing two or more kinds of particles having different melting points is used as a mold mother. It has an optical surface forming part formed by applying to a material and baking, and the optical surface forming part has corresponding irregularities for randomly transferring and forming fine irregularities on the optical surface. Provide the mold. According to the present invention, by firing, the optical surface has corresponding irregularities for randomly transferring and forming fine irregularities, so that an optical surface that suppresses reflection of light can be formed. In addition, a master mold is not required, and it is not necessary to coat or etch the optical surface, so that the cost is low.

  In the present invention, the “optical surface” includes a light transmitting surface such as an optical lens such as glass or plastic, or a diffusion sheet of a personal computer display.

  It is preferable that the optical surface forming part is formed by firing at a temperature at which particles having a lower melting point among the particles are settled or removed. Since the particles having the higher melting point remain on the surface and the portions where the particles having the lower melting point existed become grooves, fine and random irregularities can be formed more accurately.

  Moreover, it is preferable that the said unevenness | corrugation is a random unevenness whose space | interval is 150 ± 80 nm and whose depth is 2.0 ± 1.5 times the space | interval. Since the interval between the protrusions transferred and formed by such irregularities is sufficiently smaller than the wavelength of visible light, it is possible to prevent ghosts more effectively. Further, since the height of the protrusion formed by transfer is 2.0 ± 1.5 times the interval and smaller than the wavelength of visible light, it is possible to prevent ghosts more effectively.

  The cross-sectional shape of the irregularities may be a substantially rectangular shape or a triangular lattice shape. If it is uneven, the shape is not limited to these.

  Further, the particles may be a combination of one or two or more kinds of metal particles and one or two or more kinds of organic particles, or two or more kinds of metal particles.

  According to a second aspect of the present invention, there is provided an optical lens formed by using any one of the above molds. Since light reflection can be suppressed, the light transmittance can be further increased. Further, it is not necessary to perform coating or the like, and can be provided at a low cost. The optical lens may be made of a plastic material or a glass material. With the glass material, the unevenness can be transferred and formed with higher accuracy.

  According to a third aspect of the present invention, there is provided an optical lens characterized in that an optical surface having random unevenness is provided at intervals smaller than the wavelength of incident light and having a height smaller than the wavelength of incident light. Since the interval between the projections and depressions of the unevenness is sufficiently smaller than the wavelength of visible light, it is possible to prevent ghosts more effectively. Further, since the height of the protrusion is about twice the interval and smaller than the wavelength of visible light, it is possible to prevent ghosts more effectively. Random irregularities have less wavelength dependency in light reflection than periodic irregularities, prevent the generation of stray light, and can more effectively prevent ghosts.

  According to a fourth aspect of the present invention, there is provided an optical apparatus comprising the above-described optical lens. Since light reflection can be suppressed, the light transmittance can be further increased.

  According to a fifth aspect of the present invention, there is provided a mold manufacturing method for forming an optical surface having a fine concavo-convex surface in order to achieve the above object, and a slurry containing two or more kinds of particles having different melting points. An optical surface forming portion forming step of forming an optical surface forming portion by applying and baking to a mold base material, and in the optical surface forming portion forming step, particles having a lower melting point among the particles are included. A mold manufacturing method comprising a step of forming an irregularity by firing at a temperature at which the optical surface is settled or removed, and forming an optical surface forming portion having irregularities corresponding to randomly transferring fine irregularities on the optical surface. Provide a method. Low cost can be realized without the need for a master mold.

  According to the present invention, it is possible to form an optical surface that suppresses reflection of light at a low cost.

[First Embodiment]
The metal mold | die which concerns on the 1st Embodiment of this invention is a metal mold | die for forming the optical surface which has a fine uneven surface, Comprising: Slurry containing two types of metal particles from which melting | fusing point differs is a metal mold | die base material The optical surface forming portion is formed by applying and baking on the optical surface, and the optical surface forming portion has corresponding irregularities for randomly transferring and forming fine irregularities on the optical surface.

  The metal mold | die which concerns on the 1st Embodiment of this invention is produced as follows.

  In both cases, two types of metals having a particle size of 150 ± 50 nm and different melting points are dispersed in the same amount in a dispersion medium and mixed to obtain a slurry. Such slurry is applied to a mold base material. The coating thickness is 1 μm in this embodiment. As the dispersion medium, known dispersion media such as mineral oil, synthetic oil, and water can be used. A binder or the like may be added.

  The mold is fired at a temperature that is sufficient for one type of metal to melt and settle to the mold base or to be removed, and for the other type of metal to remain undissolved.

  At the time of coating, two kinds of metals are present on the surface. By firing, metal particles having a lower melting point are settled or removed, and a void of about one particle is formed where the particles are present. Polishing is performed so that the depth of the voids is about 2 particles. Irregularities are randomly formed on the surface of the mold by the voids.

  In this embodiment, a disk-shaped stainless steel-based mold base material having a diameter of 50 mm and a thickness of 3 mm is used as the mold base material, but any kind of metal can be used for the mold base material. . For example, known metals such as stainless steel, iron, magnesium, titanium, palladium, and alloys thereof can be used.

  The metal particles used in the present invention include two types of metal particles having a melting point of about 300 ° C. and a metal particle having a melting point of about 600 ° C. However, the combination of the melting points is not limited to this. Metal particles having a temperature of about 1000 ° C. and metal particles having a temperature of about 1000 ° C. may be used. Unevenness may be randomly formed on the surface of the mold by voids obtained by applying and baking a slurry in which three or more kinds of metal particles are combined. Examples include, but are not limited to, a combination of an antifriction alloy and magnesium, a combination of silver-tin-zinc-indium and copper. Magnesium, nickel, yttrium, cobalt, tungsten, vanadium, iron, zinc, tin, silver, indium, gold, aluminum, platinum, titanium, zirconium, rubidium, steel stainless steel, iridium and their compounds and combinations Appropriate combinations can be used.

  The mold of the present embodiment has substantially rectangular irregularities corresponding to randomly transferring fine irregularities on the optical surface by firing at a temperature at which only one metal is settled or removed.

  Since the metal particles with the higher melting point remain on the surface and the portions where the metal particles with the lower melting point existed become grooves, fine and random irregularities are accurately formed. In this embodiment, the unevenness interval is 150 ± 80 nm, and the depth is 2.0 ± 1.5 times the interval.

  Using this mold, a plastic lens is injection-molded with a polyolefin resin for optics. On the optical surface of the lens, protrusions whose height is 2.0 ± 1.5 times the interval are randomly transferred at intervals of 150 ± 80 nm. The interval between the protrusions to be transferred is sufficiently smaller than the wavelength of visible light. The height of the protrusion to be transferred is 2.0 ± 1.5 times the interval and is smaller than the wavelength of visible light. With respect to the reflectance of such an optical surface, the reflection of light is suppressed in the visible light region as compared with the reflectance of an optical surface that is not provided with unevenness.

  Further, the optical surface is finely polished.

(Effects of the first embodiment)
According to the first embodiment, it is possible to form an optical surface that suppresses reflection of light at a low cost by firing at a temperature at which only one metal particle is settled or removed. Further, a master mold or the like is not required, and the manufacturing cost can be reduced.

  When the firing temperature is higher than any melting point of the mixed metal particles, the firing may be performed in a short time so that only one of the metal particles is precipitated or removed.

  Moreover, although multiple types of metal particles were used for the particles, metal particles and organic particles may be used. For example, aluminum particles having a particle size of 150 ± 50 nm can be used as the metal particles, and acrylic particles having a particle size of 150 ± 50 nm can be used as the organic particles. In addition to acrylic particles, various organic fine particles such as polyethylene terephthalate polymer beads can be used. Unevenness can be formed on the surface by precipitating or removing the organic fine particles by firing.

[Second Embodiment]
The second embodiment of the present invention is an optical lens molded using the mold of the first embodiment.

  The molten glass is poured into the mold, and after cooling, the optical lens that is a molded product is taken out from the mold. On the optical lens, protrusions having a height of 2.0 ± 1.5 times the interval were randomly transferred at intervals of 150 ± 80 nm. The reflectance of such an optical surface is very low in the visible light region. The height of the projection on the optical surface is smaller than the wavelength of the incident light, and the interval between the projections is smaller than the wavelength of the incident light.

  Since the optical lens of the second embodiment has such an optical surface, surface reflection can be reduced, thereby preventing the occurrence of ghosts. Therefore, the light transmittance is increased. Since such an optical lens is not individually coated, the manufacturing process is reduced and the optical lens can be manufactured at a low cost. Since the unevenness is random, the wavelength dependency in light reflection is less than that of periodic unevenness, and stray light can be prevented from being generated and ghosts can be prevented more effectively.

[Third Embodiment]
The third embodiment of the present invention is an optical apparatus using the optical lens of the second embodiment.

  This is a camera finder in which optical lenses having optical surfaces having fine irregularities on opposite surfaces are arranged. From the object side to the pupil side, a first lens having a positive refractive index, a second lens having a negative refractive index, and a third mirror having a negative refractive index and having a half mirror on the pupil side surface An objective lens composed of three lenses, a frame plate with aluminum deposited on the object side surface, and an eyepiece with a positive refractive index are arranged in this order. On the pupil-side surface of the first lens, the object-side surface of the second lens, and the object-side surface of the eyepiece lens, fine irregularities are provided in a region where light is transmitted. The first lens is the optical lens of the second embodiment, and the second lens and the eyepiece lens are different in the overall shape of the lens, but are provided with fine irregularities in the same manner as the first lens. It is a created optical lens.

  With such a configuration, surface reflection can be reduced, and thus ghosting can be prevented.

  In the optical device according to the third embodiment, since light reflection on the optical surface of the lens is suppressed, the optical transmittance of the optical device is increased as an optical device. Such an optical device requires less manufacturing process of the optical lens to be used, and can be produced at a low cost, so that the entire device can be produced at a low cost. It is easy to see because it can prevent ghosts caused by back light from the pupil side.

[Fourth Embodiment]
The fourth embodiment of the present invention is an optical molded using a mold produced in the same manner as the mold of the first embodiment except that the surface of the optical surface forming portion is not a curved surface but a flat surface. Equipment. The fourth embodiment of the present invention is a diffusion sheet for a personal computer display.

  The optical device according to the fourth embodiment has high light transmittance because reflection of light is suppressed on the surface of the diffusion sheet. Moreover, there is no need for coating and it can be produced at low cost.

  In the present embodiment, a diffusion sheet for a personal computer display is used as an optical device. However, an anti-reflection sheet such as an AR (anti-reflection) film used for a plasma display or the like, and an anti-glare film used for a liquid crystal television or the like. A CRT display may be used. Since molding is performed using a mold produced in the same manner as the mold of the first embodiment, light is reflected on the sheet or display surface without coating or without non-glare processing with silica. It is suppressed and the light transmittance is increased.

[Other embodiments]
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. In addition, the constituent elements of the above embodiments can be arbitrarily combined without departing from the spirit of the invention.

For example, in the above embodiment, the optical device such as an optical lens or a diffusion sheet of a personal computer display has been exemplified as the one molded from the mold, but other solid products may be used.

Claims (8)

An optical surface forming part for forming an optical surface having a fine uneven surface, which is formed by applying a slurry containing two or more kinds of particles having different melting points to a die base material and firing the slurry. And the optical surface forming part has irregularities corresponding to randomly transferring and forming fine irregularities on the optical surface. 2. The mold according to claim 1, wherein the optical surface forming portion is formed by firing at a temperature at which a particle having a lower melting point among the particles is settled or removed. 3. The mold according to claim 1, wherein the unevenness is a random unevenness having an interval of 150 ± 80 nm and a depth of 2.0 ± 1.5 times the interval. The said particle | grain is a combination of 1 or 2 or more types of metal particles and 1 or 2 or more types of organic substance particles, or 2 or more types of metal particles, The any one of Claims 1-3 characterized by the above-mentioned. The mold described. An optical lens, which is molded using the mold according to any one of claims 1 to 4. An optical lens having an optical surface having random irregularities at intervals smaller than the wavelength of incident light and having a height smaller than the wavelength of incident light. An optical apparatus comprising the optical lens according to claim 5. A method of manufacturing a mold for forming an optical surface having a fine uneven surface, wherein a slurry containing two or more kinds of particles having different melting points is applied to a mold base material and baked to form an optical surface forming unit An optical surface forming portion forming step for forming the optical surface, and in the optical surface forming portion forming step, fine particles are formed on the optical surface by firing at a temperature at which the particles having a lower melting point among the particles are settled or removed. A method for manufacturing a mold, comprising a step of forming an optical surface forming unit having an optical surface forming portion corresponding to unevenness so as to randomly transfer and form the unevenness.