JP2001147301A - Optical element and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new optical element capable of arbitrarily and easily controlling the refractive index of a material comprising a naturally originated substance, such as silk fibroin and to provide a method for producing the same. SOLUTION: This optical element has a biopolymer as its main component and is irradiated with light and/or heated, in such a way that the refractive index change is induced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical element and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a lens, an optical waveguide, an optical diffraction grating,
Various types of optical elements such as an optical memory and an optical fiber are known. In manufacturing such optical elements, it is extremely important to control the refractive index of an optical material forming the elements.

As a conventional method of controlling the refractive index, a method of irradiating light is well known. In this method, a material containing a photochemically active molecule is irradiated with light to cause a photochemical reaction in the material, thereby obtaining a change in refractive index. This technology can be used to interfere with the irradiating light or to apply lithography techniques.
Since a finer change pattern of the refractive index can be obtained, application to an optical waveguide, an optical diffraction grating, an optical memory and the like has been actively studied. For example, JP-A-7-
No. 92313 discloses an optical diffraction grating in which the refractive index is periodically changed by irradiating a laser beam.

Conventionally, the above-mentioned method has been used exclusively for producing a so-called SI type optical element in which the refractive index changes discontinuously in a material. It has been found that the method can be applied to the production of a gradient index (GRIN) element in which the refractive index changes continuously.
No. 901 (Japanese Patent No. 2914486). This method uses the fact that light applied to a material is gradually weakened by absorption, and gives a continuous refractive index distribution in the depth direction to the irradiation. Thus, G
An I-type optical fiber, a GRIN lens, or the like can be obtained.

On the other hand, in Japanese Patent Application Laid-Open No. 60-73602 (Japanese Patent No. 1665354), a polymer film made of vinylidene cyanide or the like is partially subjected to heat treatment to generate portions having different refractive indexes, thereby forming an optical waveguide. A forming technique is disclosed.

[0006] In recent years, naturally-derived substances such as silk fibroin, collagen, and polysaccharides have been proposed as substances that can be used for optical materials. For example, Tokiko 1-6
No. 0126 discloses a contact lens obtained by adding epoxy to a mixture of acylchitosan and collagen and crosslinking the mixture with gamma rays. Also, Japanese Patent Application Laid-Open No. 5-3872
No. 8 discloses a contact lens in which silk powder and a vinyl monomer are compressed and heated to be solidified. Furthermore, Japanese Patent Publication No. 55-5089 discloses a soft contact lens in which a transparent collagen gel is cross-linked by irradiating it with gamma rays and subjected to dissolution treatment with a protease. In addition, Japanese Patent Application Laid-Open No.
43632, JP-A-9-316143, JP-B-58
-27813 and the like.

[0007]

However, none of the above-mentioned optical materials made of silk fibroin or the like control the refractive index in the material. Therefore, the refractive index can be arbitrarily controlled to various optical elements. Development of applied technology was desired.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems,
An object of the present invention is to provide a novel method for producing an optical element that can arbitrarily and easily control the refractive index of a material composed of a substance of natural origin such as silk fibroin, and an optical element produced thereby. Optical element obtained in the present invention,
It has excellent biocompatibility, does not adversely affect the environment even when discarded, and has excellent stability in the changed refractive index.

[0009]

Means for Solving the Problems In order to solve the above problems, the inventors of the present invention have conducted intensive studies, and as a result, it has been found that light and heat act on biopolymers such as silk fibroin under specific conditions. As a result, the present inventors have found that the refractive index can be controlled, and have completed the present invention. That is, the method for producing an optical element of the present invention is characterized in that a biopolymer is formed as a main component, and light is irradiated and / or heated so as to induce a change in refractive index.

The present inventors have found that, among the above-mentioned biopolymers, peptides or polysaccharides are preferred, and silk fibroin is most preferred as the peptide.

The present invention further provides that the wavelength of the irradiated light is 2
It is characterized in that it has a thickness of 00 to 900 nm, preferably 250 to 400 nm.

In the present invention, the energy of the irradiated light is preferably 1 to 500 J / μm, more preferably 50 to 200 J / μm.
μm.

Further, the present invention comprises an optical element manufactured by the above method.

[0014]

Embodiments of the present invention will be described below in detail.

The present invention uses a biopolymer as a main component. Specific examples of the biopolymer include polysaccharides such as cellulose, starch, and glycogen, or nucleic acids and peptides. The biopolymer is preferably transparent, but may not be transparent when another optical polymer is used as a subcomponent as described later.

Among the above biopolymers, peptides are preferably used. Here, the peptide refers to an oligopeptide having 10 or less amino acids, a polypeptide having 10 or more amino acids,
It includes a so-called protein having a molecular weight of 10,000 or more. Among various peptides, a transparent peptide is preferably used. Specific examples of such peptides include silk fibroin, raw silk, collagen, modified peptides of these, or those obtained by chemically modifying the various peptides described above.

Any of the above-mentioned peptides can be used alone, or two or more peptides can be used in combination. By combining them, the characteristics of each peptide can be balanced to obtain an optical element suitable for use. As a specific example, there is a case where silk fibroin and collagen are used in combination. In this case, each ratio is appropriately determined in consideration of the physical properties required for the target optical element.

Of the above peptides, silk fibroin is particularly preferably used. Silk fibroin can be obtained by subjecting raw silk obtained from Bombyx mori to scouring treatment as described below to remove sericin wrapping fibroin. Silk fibroin is excellent in transparency, has biocompatibility, and is biodegradable, so that disposal thereof does not adversely affect the environment. further,
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.

Polysaccharides are also preferably used as biopolymers. Specific examples of polysaccharides include ramie, flax,
Examples include various celluloses such as hemp, cotton and Indian hemp, starch, chitin, chitosan, konjac (glucomannan), agar and the like. The above polysaccharides can be used alone or in combination of two or more.

Further, it can be formed by combining a peptide and a polysaccharide. As a specific example, a case where chitosan for improving mechanical stability of a molded article and collagen for imparting flexibility are used in combination can be mentioned. In this case, each ratio is appropriately determined in consideration of the physical properties required of the target optical element.

Next, the above-mentioned biopolymer is used as a main component and molded into various shapes. The molding is performed by appropriately selecting a conventionally known method. Here, the molded article may contain various auxiliary components in addition to the biopolymer. Specific examples of the accessory component include other optical polymers, photosensitizers, crosslinking agents,
Examples include a polymerization initiator and a plasticizer. The other optical polymer described above may be blended with a biopolymer or copolymerized with a biopolymer. The photosensitizer is used to change the refractive index more efficiently, and specific examples include a benzophenone derivative, fluorene, phenanthrene, and anthracene.

As a specific example of the molding process, the case of silk fibroin will be described. First, raw silk is scoured with a boiling calcium chloride aqueous solution or a lithium bromide aqueous solution at room temperature to separate sericin, and then the inorganic component is dialyzed. Is removed to obtain a solution of silk fibroin, and the solution is dried to obtain a powder of silk fibroin. Thereafter, the powder can be melted and compressed to form a desired shape. Alternatively, the silk fibroin solution may be formed while drying. In addition, instead of the above-mentioned aqueous solution of a neutral salt such as calcium chloride, it can be dissolved by hydrolysis with an acid such as hydrochloric acid or an alkali.

As another method, the above-mentioned silk fibroin powder may be mixed with a vinyl-based monomer or the like, or may be copolymerized and molded by heating and compression. Furthermore, it can also be obtained by adding a vinyl-based monomer or the like to a silk fibroin solution, copolymerizing the solution, shaping into a desired shape, and then removing the inorganic component from the formed product by dialysis. As the above monomer, any one that is hardly denatured even by irradiating light or heating can be used.Specifically,
Examples include methyl methacrylate, glycidyl methacrylate, polyethylene glycol methacrylate, hydroxymethyl methacrylate, styrene, acrylic acid and the like.

Further, a molded article made of silk fibroin is as follows:
An insolubilization treatment can be performed to improve the water resistance. As a specific method of the insolubilization treatment, a molded product is 70
% By immersion in an alcohol such as ethanol, or by adding chitosan, alginic acid and the like in advance to the silk fibroin solution before molding. The insolubilization was performed by combining the NH group of the peptide bond with alginic acid, chitosan,
And the formation of a hydrogen bond with the OH group of the alcohol.

Furthermore, a plasticizer such as alginic acid may be added to a molded product made of silk fibroin to lower the crystallinity, thereby making the molded product flexible. In addition, since the formation of the β sheet proceeds by adding a plasticizer,
It is also possible to improve mechanical properties such as strength of the molded product. The above softening can also be performed by adding a proteolytic enzyme to a molded article made of silk fibroin.

While the above description has been made with respect to silk fibroin,
Similarly, for other biopolymers, a biopolymer powder or a melt or a solution thereof can be prepared, and an auxiliary component such as an optical polymer can be appropriately added and molded by various methods.

It is possible to obtain various optical elements by irradiating light or heating the molded product containing a biopolymer as a main component formed as described above so as to induce a change in the refractive index. it can.

The wavelength of the light to be applied may be any wavelength at which the biopolymer undergoes a photochemical reaction and the refractive index changes accordingly. Generally, 200-900n
m, among which 250 to 400 nm is preferable. If the thickness is less than 200 nm, the molecular chain of the biopolymer may be cut, or the molecular chain of the optical polymer used as an auxiliary component may be cut to break the element, which is not suitable. When the thickness is 900 nm or more, the organic substance generally does not react and only vibrates the molecule, and the refractive index hardly changes. Further, 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 the obtained refractive index increases.

The energy of the irradiated light varies depending on the type of the biopolymer, the irradiation wavelength, the size of the molded product, etc., but is generally 1 to 500 J / μm, and more preferably 50 to 20 J / μm.
Preferably, it is 0 J / μm. If it is 1 J / μm or less, a sufficient change in the refractive index cannot be obtained, and 500 J / μm
Above is not suitable because the change in the refractive index is saturated, and rather, the optical characteristics are impaired due to yellowing and the like.

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 ultra-high-pressure mercury lamp, a low-pressure mercury lamp, a chemical lamp,
Xenon lamps, various laser beams, and the like can be given. Further, upon irradiation, the wavelength irradiated to the molded product through various filters such as an interference filter can be reduced. As a result, the biopolymer can be made to react more selectively, and the refractive index can be precisely controlled.

The heating temperature may be any temperature at which the refractive index changes due to the reaction of the biopolymer, and is generally 40 to 220 ° C., preferably 80 to 200 ° C. The mechanism by which the refractive index of the biopolymer changes due to heat is not clear, but may be due to oxidation.

As the heating method, a conventional general method can be applied. Specifically, the molded article is heated on a hot plate or a thermostat, or the refractive index is changed by infrared laser, microwave irradiation, or the like. A method of locally heating a part to be made or the like is appropriately selected.

The light irradiation and the heat treatment can be carried out alone or in combination, and the light irradiation can be carried out while heating. In general, when used together, the reaction of the biopolymer is accelerated, and the refractive index can be controlled efficiently. Further, the obtained refractive index difference tends to increase, which is preferable. In addition, the refractive index, the light irradiation time,
Since it continuously changes depending on the wavelength, intensity, heating temperature, heating time, and the like, it is possible to arbitrarily control the refractive index by selecting conditions.

Specific steps for manufacturing individual optical elements can be performed in the same manner as in the prior art. For example, an 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.

As another example, in the case of an optical diffraction grating,
It can be obtained by causing a laser beam that induces a change in the refractive index to interfere with a molded product containing a biopolymer as a main component and irradiating the interference fringes.

As still another example, in the case of an optical memory,
A molded article containing a biopolymer as a main component is used as a recording medium, and light can be focused on the surface and inside to change the refractive index and write information.

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 to improve the aberration of the lens by controlling the Abbe number. can do.

In addition to the above-described SI type optical element in which the refractive index is discontinuously changed, a refractive index distribution type (G
It can be applied to the production of an (I-type) optical element. For example, a GRIN lens can be obtained by gradually increasing (shorting) the light irradiation time from the center to the periphery of the lens, and the thickness of the lens can be reduced.

Further, since the manufactured optical element has excellent biocompatibility, it is suitably used as a biological or medical optical element. Specifically, for example, it can be used as a lens (artificial lens) to be implanted in the eye for cataract treatment. In other words, it is better to make the intraocular lens as thin as possible to reduce the weight of the lens, so that the positional stability of the lens after surgery is better. Particularly suitable for the application. In addition, by softening the lens and making a so-called soft type intraocular lens, it is possible to form an incision smaller than the lens diameter during cataract surgery, and insert the intraocular lens into this incision by rounding it. Since it is possible, the burden on the patient is small, which is preferable. Other uses include, but are not limited to, optical fibers implanted in the body.

[0040]

The present invention will be described more specifically with reference to the following examples. (Example 1) 5 g of a raw silk obtained from a silkworm cocoon was added to 50 ml of a saturated (50 wt%) aqueous solution of calcium chloride, and the mixture was boiled and treated for 1 hour. Subsequently, dialysis was performed for 4 days to remove calcium chloride, followed by air drying and concentration to obtain a 10% by weight aqueous solution of silk fibroin. The obtained aqueous solution was spin-coated to prepare a film of silk fibroin having a thickness of 3 to 4 μm on quartz glass.

The above film was irradiated with an ultrahigh pressure mercury lamp (wavelength range: 250 to 430 nm, spot cure manufactured by USHIO Corporation). The light intensity was 52 mW at 254 nm, 3
140 mW at 65 nm. UV of film due to light irradiation
FIG. 1 shows the absorption spectrum. From FIG. 1, an increase in absorbance was observed with light irradiation, and it was clear that silk fibroin caused a photochemical reaction. Although the mechanism of the reaction is not clear, it is considered to be photooxidation. Then, as shown in FIG. 2, the refractive index of the film is changed from 1.540 to 1.55 with light irradiation.
A rise to 1 was observed. 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.

Example 2 The silk fibroin film used in Example 1 was heated at 130 ° C., and the change in the refractive index 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 obtained refractive index difference was 0.9% at the maximum, and a sufficiently large value was obtained.

Example 3 The silk fibroin film used in Example 1 was heated to 130 ° C. and 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 an increase in heating and irradiation time, and it became clear that the refractive index could be controlled. The obtained refractive index difference was a maximum of 1.8%, which was a large value. In addition, it was clarified that silk fibroin can be made to react more efficiently by using light irradiation and heat treatment together, and the obtained refractive index difference can be increased.

Example 4 As shown in FIG. 5, the silk fibroin film 1 formed 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 radiated into a single wavelength by the interference filter 4. Then, a photomask 3 was disposed on the silk fibroin film 1. The photomask 3 had a pattern in which 25 straight lines were cut in parallel at regular intervals, and the line width was 0.4 μm. After irradiation for 120 min, the silk fibroin membrane
When a He-Ne laser beam of 2.8 nm was guided and observed by the prism coupling method, it was confirmed that the laser beam was reflected when the laser beam was incident on the exposed portion at a constant angle. Was completed.

Example 5 A polybenzyl glutamate film formed on a substrate was provided with a line width of 1 mm and a radius of curvature of 1000 m.
Ultraviolet rays were irradiated through a photomask in which the curve of m was cut in the same manner as in Example 4 to perform patterning. 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 emission portion.

[0046]

As described above, according to the present invention, the refractive index of a material containing a biopolymer such as silk fibroin as a main component can be arbitrarily and easily controlled, and it is excellent in biocompatibility.
Various optical elements that do not adversely affect the environment when discarded were obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in a UV absorption spectrum of a film due to light irradiation in Example 1.

FIG. 2 is a graph showing a change in the refractive index of a film due to light irradiation in Example 1.

FIG. 3 is a graph showing a change in refractive index of a film due to heating in Example 2.

FIG. 4 is a graph showing a change in refractive index of a film due to heating and light irradiation in Example 3.

FIG. 5 is a schematic diagram showing an experimental device in Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silk fibroin film 2 Substrate 3 Photomask 4 Interference filter 5 Mirror 6 Lens 7 Light source 8 Ultraviolet light

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 1/00 C08L 3/00 3/00 5/00 5/00 89/00 89/00 G02B 6/12 N (72) Inventor Takeshi Kada 8154-217 Uenohara-cho, Uenohara-cho, Kitatsuru-gun, Yamanashi Prefecture F-term in Trichemical Research Laboratories Co., Ltd. BB01 BB02 CA45 CA46 4J002 AB001 AB011 AB041 AB051 AD001 FD020 FD200 GB00

Claims (6)

[Claims] 1. A method for manufacturing an optical element, comprising forming a biopolymer as a main component, irradiating light to induce a change in refractive index, and / or heating. 2. The method according to claim 1, wherein the biopolymer is a peptide or a polysaccharide. 3. The method according to claim 2, wherein the peptide is silk fibroin. 4. The wavelength of light for irradiation is 200 to 900 n.
2. The method for manufacturing an optical element according to claim 1, wherein m is preferably 250 to 400 nm. 5. The energy of light for irradiation is 1 to 500.
5. The method for producing an optical element according to claim 1, wherein the optical element has a J / m of 50 to 200 J / m. 6. An optical element manufactured by the manufacturing method according to claim 1.