JP4326646B2 - Optical element and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical element and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, various optical elements such as a lens, an optical waveguide, an optical diffraction grating, an optical memory, and an optical fiber are known. In manufacturing these optical elements, the refractive index of the optical material constituting the element is controlled. It is extremely important to do.
[0003]
As a conventional method for controlling the refractive index, a method of irradiating light is well known. This is to irradiate a material containing photochemically active molecules with light to cause a photochemical reaction in the material and to obtain a change in refractive index associated therewith. This technology can obtain a finer change pattern of the refractive index by interfering with the light to be irradiated or by applying a lithography technique. In particular, this technology can be applied to optical waveguides, optical diffraction gratings, optical memories, etc. Applications are actively researched. For example, Japanese Patent Application Laid-Open No. 7-92313 discloses an optical diffraction grating in which the refractive index is periodically changed by irradiating laser light.
[0004]
The method described above has heretofore been exclusively used to produce so-called SI-type optical elements in which the refractive index changes discontinuously in the material. Have been found to be applicable to the manufacture of a gradient index gradient type (GRIN) element, and proposed in JP-A-9-178901 (Japanese Patent No. 2914486). This method utilizes the fact that light irradiated to a material is gradually weakened by absorption, and gives a continuous refractive index distribution in the depth direction with respect to irradiation. Thereby, a GI type optical fiber, a GRIN lens, etc. can be obtained.
[0005]
On the other hand, in Japanese Patent Laid-Open No. 60-73602 (Japanese Patent No. 1665354), a polymer film made of vinylidene cyanide or the like is partially heat-treated to generate portions having different refractive indexes, thereby forming an optical waveguide. Is disclosed.
[0006]
In recent years, naturally-occurring substances such as silk fibroin, collagen, and polysaccharides have been proposed as substances that can be used in optical materials. For example, Japanese Patent Publication No. 1-60126 discloses a contact lens in which an epoxy is added to a mixture of acylchitosan and collagen and crosslinked with gamma rays. Japanese Patent Laid-Open No. 5-38728 discloses a contact lens in which silk powder and a vinyl monomer are solidified by compression and heating. Further, Japanese Patent Publication No. 55-5089 discloses a soft contact lens in which a transparent collagen gel is irradiated with gamma rays to be crosslinked and subjected to a dissolution treatment with a proteolytic enzyme. Other conventional examples include JP-A-8-143632, JP-A-9-316143, and JP-B-58-27813.
[0007]
[Problems to be solved by the invention]
However, none of the optical materials composed of the above-mentioned silk fibroin or the like is a material in which the refractive index in the material is controlled, and therefore, development of a technique to be applied to various optical elements by arbitrarily controlling the refractive index is desired. It was.
[0008]
Therefore, in view of the above-described conventional problems, the present invention provides a novel optical element manufacturing method capable of arbitrarily and easily controlling the refractive index of a material composed of a naturally derived substance such as silk fibroin, and the manufacturing thereof. An optical element is provided. The optical element obtained by the present invention is excellent in biocompatibility, does not adversely affect the environment even when discarded, and the changed refractive index is excellent in stability.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors conducted extensive research and found that the refractive index can be controlled by applying light or heat to biopolymers such as silk fibroin under specific conditions. The present invention has been completed. That is, the method for producing an optical element of the present invention is characterized in that silk fibroin or polybenzyl glutamate is formed as a main component, and light is irradiated and / or heated so as to induce a change in refractive index.
[0011]
Further, the present invention is characterized in that the wavelength of light to be irradiated is 200 to 900 nm, preferably 250 to 400 nm.
[0012]
Further, the present invention is characterized in that the energy of the irradiated light is 1 to 500 J / μm, preferably 50 to 200 J / μm.
[0013]
Furthermore, this invention consists of an optical element manufactured by said method.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0015]
In the present invention, a peptide is used as a main component. Moreover, although it is preferable that a peptide is transparent, as mentioned later, when using another optical polymer as a subcomponent, it does not need to be transparent.
[0016]
Here, the peptide includes a so-called protein having a molecular weight of 10,000 or more in addition to an oligopeptide having 10 or less amino acids and a polypeptide of 10 or more. Specific examples of the peptide of the present invention include silk fibroin shown in Examples 1 to 4 described later, polybenzylglutamate shown in Example 5 , or modified peptides thereof , or those chemically modified. Can do.
[0017]
Any of the above peptides can be used alone, or two or more peptides can be used in combination. By combining them, it is possible to obtain an optical element suitable for the application by balancing the characteristics of each peptide. As a specific example, a case where silk fibroin and collagen are used in combination can be mentioned. In this case, each ratio is appropriately determined in consideration of physical properties required for the target optical element.
[0018]
Silk fibroin that is particularly preferably used can be obtained by subjecting raw silk obtained from silkworm to a scouring treatment as described later to remove sericin enveloping fibroin. Silk fibroin is excellent in transparency, biocompatibility, and biodegradable, so it does not adversely affect the environment even when discarded. Furthermore, when the refractive index is controlled according to the present invention, the obtained refractive index difference is large and the refractive index after the change is stable, so that it is suitable as a material for an optical element.
[0021]
Next, the above-described biopolymer (here, silk fibroin or polybenzyl glutamate, which is the same for all the following biopolymers) is molded into various shapes. Molding is performed by appropriately selecting a conventionally known method. Here, in addition to biopolymers, the molded product can contain various subcomponents. Specific examples of the auxiliary component include other optical polymers, photosensitizers, crosslinking agents, polymerization initiators, plasticizers, and the like. The other optical polymers described above may be blended with biopolymers or copolymerized with biopolymers. The photosensitizer is used for more efficiently changing the refractive index, and specific examples include benzophenone derivatives, fluorene, phenanthrene, anthracene and the like.
[0022]
As a specific example of the molding process, silk fibroin is described. First, raw silk is scoured with boiling calcium chloride aqueous solution or room temperature lithium bromide aqueous solution to separate sericin, and then inorganic components are removed by dialysis. A silk fibroin solution is obtained and dried to obtain a silk fibroin powder. Thereafter, the powder can be melted and compressed to be formed into a desired shape. Or you may shape | mold, drying the solution of said silk fibroin. In addition, it can also be made to hydrolyze and dissolve with acids and alkalis, such as hydrochloric acid, instead of neutral salt aqueous solution, such as said calcium chloride.
[0023]
As another method, the above-mentioned silk fibroin powder may be mixed with a vinyl monomer or the like, or copolymerized and heat-compressed for molding. Furthermore, it can also be obtained by adding a vinyl monomer or the like to a silk fibroin solution and copolymerizing it to form a desired shape, and then removing the inorganic component from the molded product by dialysis. As the above-mentioned monomer, any monomer that is difficult to modify even when irradiated with light or heated can be applied. Specific examples include methyl methacrylate, glycidyl methacrylate, polyethylene glycol methacrylate, hydroxymethyl methacrylate, styrene, acrylic acid, and the like. It is done.
[0024]
In addition, a molded product made of silk fibroin can be insolubilized to improve water resistance. A specific insolubilization method can be achieved by immersing the molded article in an alcohol such as 70% ethanol or adding chitosan, alginic acid or the like in advance to the silk fibroin solution before molding. The insolubilization is considered to be due to the formation of a hydrogen bond between the NH group of the peptide bond and the OH groups of alginic acid, chitosan, and alcohol.
[0025]
Further, a plasticizer such as alginic acid is added to the molded product made of silk fibroin to reduce the crystallinity, thereby softening the molded product. Moreover, since the formation of the β sheet proceeds by adding a plasticizer, mechanical properties such as strength of the molded product can be improved. Moreover, said softening can also be performed by adding a proteolytic enzyme to a molding made of silk fibroin.
[0026]
Above has been described silk fibroin, as well a poly benzyl glutamate, powders poly benzyl glutamate, or to prepare the melt or solution, by a variety of methods by adding auxiliary components such as an optical polymer as appropriate Can be molded.
[0027]
Various optical elements can be obtained by irradiating or heating the molded article mainly composed of the biopolymer as described above so as to induce a change in refractive index.
[0028]
The wavelength of the irradiated light can be used as long as the biopolymer causes a photochemical reaction and the refractive index changes accordingly. In general, the thickness is preferably 200 to 900 nm, and more preferably 250 to 400 nm. If it is 200 nm or less, the molecular chain of the biopolymer may be cleaved, or the molecular chain of the optical polymer used as an accessory component may be cleaved to break the device, which is not suitable. In the case of 900 nm or more, generally, an organic substance does not react, only a molecule is vibrated, and the refractive index hardly changes. Moreover, it is preferable to select a wavelength that matches the absorption wavelength of the biopolymer to be used because the refractive index can be controlled more efficiently and the difference in refractive index obtained is increased.
[0029]
The energy of light to be irradiated varies depending on the type of biopolymer, the irradiation wavelength, the size of the molded product, and the like, but is generally 1 to 500 J / μm, more preferably 50 to 200 J / μm. If it is 1 J / μm or less, a sufficient change in the refractive index cannot be obtained, and if it is 500 J / μm or more, the change in the refractive index is saturated.
[0030]
As the light source, any light source having the above-mentioned wavelength can be used. Specific examples include a carbon arc lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a low-pressure mercury lamp, a chemical lamp, a xenon lamp, and various laser lights. . In irradiation, the wavelength irradiated to the molded product through various filters such as an interference filter can be reduced. Thereby, the biopolymer can be reacted more selectively, and the refractive index can be precisely controlled.
[0031]
Furthermore, the heating temperature can be applied as long as the biopolymer reacts and the refractive index changes, and is generally 40 to 220 ° C, and preferably 80 to 200 ° C. Although the mechanism by which the refractive index of the biopolymer changes due to heat is not clear, the possibility of oxidation is considered.
[0032]
Moreover, the conventional general method can be applied to the heating method. Specifically, the molded product is heated on a hot plate or in a thermostatic bath, or the refractive index is changed by infrared laser, microwave irradiation or the like. The method etc. which heat locally are selected suitably.
[0033]
The light irradiation and the heat treatment can be performed alone or in combination, and the light irradiation can be performed while heating. Generally, the combined use accelerates the reaction of the biopolymer, and the refractive index can be controlled efficiently. Moreover, since the refractive index difference obtained tends to become large, it is preferable. Further, since the refractive index continuously changes depending on the light irradiation time, wavelength, intensity, heating temperature, heating time, etc., the refractive index can be arbitrarily controlled by selecting conditions.
[0034]
About the process of manufacturing a specific individual optical element, it can carry out similarly to the prior art. For example, the optical waveguide can be obtained by irradiating a molded product containing a biopolymer as a main component with light through a mask so as to induce a change in refractive index. Heating may be used instead of light irradiation.
[0035]
As another example, in the case of an optical diffraction grating, it can be obtained by causing a laser beam that induces a refractive index change to interfere with a molded product mainly composed of a biopolymer and irradiating the interference fringes. .
[0036]
As yet another example, in the case of an optical memory, information can be written by changing the refractive index by focusing light on the surface and the inside of a molded article mainly composed of a biopolymer.
[0037]
Furthermore, a lens such as a contact lens is manufactured from a biopolymer, and the wavelength dispersion of the refractive index is changed by irradiating or heating the lens, and the aberration of the lens can be improved by controlling the Abbe number. it can.
[0038]
Further, it can be applied not only to the SI type optical element in which the refractive index is changed discontinuously as described above but also to the production of a graded index type (GI type) optical element. For example, by gradually increasing (shortening) the light irradiation time from the center to the periphery of the lens, a GRIN lens can be obtained, and the thickness of the lens can be reduced.
[0039]
Furthermore, since the produced optical element is excellent in biocompatibility, it is suitably used as an optical element for living organisms and medical use. Specifically, for example, it can be used as a lens (artificial lens) that is implanted in the eye for the treatment of cataract. In other words, the intraocular lens is as thin as possible and the weight of the lens is reduced so that the positional stability of the lens after surgery is better. Therefore, the refractive index of the lens is controlled according to the present invention. Particularly suitable for applications. In addition, by softening the lens and producing a so-called soft type intraocular lens, an incision can be formed smaller than the lens diameter during cataract surgery, and the intraocular lens can be inserted into the incision in a rounded manner. This is preferable because it can reduce the burden on the patient. Other applications include, but are not limited to, optical fibers embedded in the body.
[0040]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
5 g of the raw silk obtained from the silkworm cocoon was added to 50 ml of a saturated (50 wt%) aqueous solution of calcium chloride and boiled for 1 hour. Subsequently, dialysis was carried out for 4 days to remove calcium chloride, followed by air drying and concentration to obtain a 10 wt% aqueous solution of silk fibroin. The obtained aqueous solution was spin-coated to produce a film made of silk fibroin having a thickness of 3 to 4 μm on quartz glass.
[0041]
The film was irradiated with an ultra high pressure mercury lamp (wavelength range 250 to 430 nm, spot cure manufactured by USHIO Co., Ltd.). The light intensity was 52 mW at 254 nm and 140 mW at 365 nm.
The UV absorption spectrum of the film accompanying light irradiation is shown in FIG. From FIG. 1, an increase in absorbance was observed with light irradiation, and it became clear that silk fibroin caused a photochemical reaction. Although the reaction mechanism is not clear, it is considered photooxidation. And as shown in FIG. 2, it was observed that the refractive index of a film | membrane rose from 1.540 to 1.551 with light irradiation. The refractive index of the film was measured by a prism coupling method. From this result, it became clear that the refractive index can be controlled by light irradiation. The obtained refractive index difference was 0.011 at the maximum, and a value sufficient for application to an optical element such as an optical waveguide was obtained.
[0042]
(Example 2)
The silk fibroin film used in Example 1 was heated at 130 ° C., and the refractive index change accompanying the heating was measured by the prism coupling method.
As a result, as shown in FIG. 3, it was observed that the refractive index increased as the heating time increased. This revealed that the refractive index can be controlled by heating. The refractive index difference obtained was 0.9% at maximum, and a sufficiently large value was obtained.
[0043]
(Example 3)
The silk fibroin film used in Example 1 was heated to 130 ° C. and simultaneously irradiated with light under the same conditions as in Example 1.
As a result, as shown in FIG. 4, it was observed that the refractive index increased with increasing heating and irradiation time, and it became clear that the refractive index could be controlled. The obtained refractive index difference was 1.8% at maximum, which was a large value. Moreover, it became clear that silk fibroin can be made to react more efficiently by combining light irradiation and heat treatment, and the resulting refractive index difference can be increased.
[0044]
(Example 4)
As shown in FIG. 5, the silk fibroin film 1 produced on the substrate 2 was irradiated with ultraviolet rays 8 using the same light source 7 as in Example 1. The ultraviolet rays 8 were reflected by the mirror 5, converted into parallel rays by the lens 6, and irradiated with a single wavelength by the interference filter 4. A photomask 3 was disposed on the silk fibroin film 1. The photomask 3 had a pattern in which 25 straight lines were engraved in parallel at regular intervals, and the line width was 0.4 μm. After irradiation for 120 min, a 632.8 nm He—Ne laser beam is guided through the silk fibroin film and observed by the prism coupling method, and it is confirmed that the laser beam is reflected when it is incident on the exposed portion at a constant angle. As a result, a grating element could be fabricated.
[0045]
(Example 5)
The polybenzyl glutamate film produced on the substrate was subjected to patterning treatment by irradiating ultraviolet rays in the same manner as in Example 4 through a photomask in which a curve having a line width of 1 mm and a curvature radius of 1000 mm was engraved. However, the irradiation time was 24 hours.
When laser light was introduced into the benzyl glutamate film after irradiation, the light was bent along the exposed portion, and light was observed from the exit portion.
[0046]
【The invention's effect】
As described above, according to the present invention, the refractive index of a material mainly composed of a biopolymer such as silk fibroin can be controlled arbitrarily and easily, and it is excellent in biocompatibility and has an adverse effect on the environment even when discarded. Various optical elements that could not be provided could be obtained.
[Brief description of the drawings]
1 is a graph showing changes in UV absorption spectrum of a film accompanying light irradiation in Example 1. FIG.
2 is a graph showing changes in the refractive index of a film accompanying light irradiation in Example 1. FIG.
3 is a graph showing a change in refractive index of a film accompanying heating in Example 2. FIG.
4 is a graph showing changes in the refractive index of a film accompanying heating and light irradiation in Example 3. FIG.
5 is a schematic diagram showing an experimental apparatus in Example 4. FIG.
[Explanation of symbols]
1 Silk Fibroin Film 2 Substrate 3 Photomask 4 Interference Filter 5 Mirror 6 Lens 7 Light Source 8 Ultraviolet

Claims (4)

A method for producing an optical element, comprising forming silk fibroin or polybenzylglutamate as a main component, irradiating light so as to induce a change in refractive index, and / or heating. 2. The method of manufacturing an optical element according to claim 1, wherein the wavelength of the irradiated light is 200 to 900 nm, preferably 250 to 400 nm. The method of manufacturing an optical element according to claim 1 or 2 , wherein the energy of the irradiated light is 1 to 500 J / µm, preferably 50 to 200 J / µm. Optical elements more prepared to any of the method according to claim 1-3.

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