JPH0264131A - Transparent cylindrical composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, having a distribution of refractive index in the radial direction symmetric with the central axis and utilizable as rod lenses or optical fibers excellent in heat resistance by reacting a metal alkoxide with a terminal silanol group-containing polysiloxane. CONSTITUTION:The objective composition obtained by reacting a metal alkoxide expressed by the formula M(OR)x (M is Si, Ge, Sn, Pb, Se, Te, Sb, Fe, Ti, Zr, Nb, Al, B, Ga, In, Be, Mg, Ca, Ba, Li, Na, K, Cs, etc.; R is alkyl, such as methyl, ethyl, propyl or butyl), etc., with a terminal silnanol group-containing polysiloxane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transparent cylindrical composition having a refractive index distribution in the radial direction. This composition can be used as loft lenses and optical fibers with excellent heat resistance.

[Conventional technology]

As optical materials having a refractive index distribution in the radial direction, loft lenses and optical fibers made of inorganic glass or highly transparent polymer materials are known. In particular, a cylinder that has a refractive index gradient that decreases in the radial direction from the central axis toward the outer circumference in a state close to a quadratic curve has the N ability to transmit images as a loft lens (GRIN lens), and the lens Those arranged in an array are widely used as rod lens arrays in electronic whiteboards, copying machines, telefax transmitters and receivers, and the like.

[Problem to be solved by the invention]

GRIN lenses made of highly transparent polymeric materials such as polymethyl methacrylate have poor heat resistance, and their upper limit temperature is around 80° C. at most, which limits their uses. In addition, although those obtained from inorganic glasses have excellent heat resistance, they take time to manufacture and have poor productivity. That is, glass containing metal ions is spun into a cylindrical shape using a melting method and solidified, and then the glass is immersed in an aqueous solution containing specific ions, and ion exchange is performed using a diffusion method to change the refractive index in the radial direction. It is common to give a gradient of .

With this method, the patent features a diffusion time of nearly one month to obtain a GRIN lens with a diameter of about 1 fl.
It takes a longer time to obtain a GRIN lens with a larger diameter, and one with diameters larger than 2 has not yet been put to practical use. Furthermore, since such a long diffusion time is required, the manufacturing process is a batch process and cannot be a continuous process.

As a result of studies to eliminate the drawbacks of these organic and inorganic materials, the present inventors have developed a new GRIN lens that has excellent heat resistance and short manufacturing time, and a refractive index that can be used for a new GRIN lens or graded index optical fiber. They discovered a transparent cylindrical composition having a distribution, and completed the present invention.

[Means for Solving the Problems] The present invention provides a transparent cylindrical material having a refractive index distribution in the radial direction symmetrical to the central axis, which is obtained by reacting a metal alkoxide with a polydimethylsiloxane containing a terminal silanol group. It is a composition.

That is, the present invention molecularly disperses a metal alkoxide, which is a precursor of an inorganic substance, and a terminal silanol polysiloxane, which is an organic oligomer or polymer, and changes the composition of the metal alkoxide in the radial direction.
It forms a refractive index distribution.

[For production]

The basic idea of the present invention is that if an organic polymer called polysiloxane, which has excellent heat resistance and a low glass transition temperature, is uniformly dispersed in inorganic glass, molecular mobility will be higher than that of inorganic glass. This means that the composition distribution can be easily formed by the diffusion method. The present invention will be explained in detail below.

In the present invention, known metal alkoxides can be used. The metal alkoxide is generally M(
OR) x. It is known that all metal atoms except halogens in group Ⅰ and noble gases in group 0 of the periodic table form alkoxides, but in the present invention, which aims at transparent glass, as the metal component M,
Si, Ge.

Sn, Pb, Se, Te, Sb, Fe, Ti.

Zr, Nb, Ta, AI, B, G
a, In, Be.

Mg, Ca, Ba, Li, Na, Cs, etc. can be used. The alkyl group R may also be methyl, ethyl, propyl, butyl and isomers thereof.

The polysiloxane is required to contain terminal silanol groups capable of reacting with metal alkoxides;
The alkyl substituent of siloxane is generally a methyl group, an ethyl group, a phenyl group, etc., but is not limited to these. The degree of polymerization of the terminal silanol polysiloxane is preferably 1 or more and 5,000 or less, more preferably 1,000 or less. When the degree of polymerization exceeds 1000, the concentration of terminal reactive groups decreases and the viscosity increases, making it difficult to carry out a homogeneous reaction.

The reaction between the metal alkoxide and the polysiloxane containing a terminal silanol group requires water for hydrolysis, and the amount thereof is preferably 4 times or less in mole relative to the metal alkoxide. As the catalyst, various acids can be used, such as inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as formic acid, acetic acid, and oxalic acid. Moreover, basic catalysts such as NaOH, N)+40H can also be used. Although the reaction can be carried out either in the absence of a solvent or in the presence of a solvent, it is preferable to have an appropriate amount of alcohol present as a reaction site that facilitates a homogeneous reaction for dispersing molecules. In this case, after the reaction has progressed to a certain extent, the alcohol can be evaporated and concentrated.

When a liquid mixture with such a composition is mixed and stirred, the metal alkoxide is hydrolyzed by water, and the hydrolyzed comrades or the hydrolyzate and terminal silanol polysiloxane or polysiloxanes undergo a dehydration polycondensation reaction to form a high molecular weight. , and finally becomes a crosslinked gel in which inorganic and organic substances are molecularly dispersed. After the water and solvent have evaporated, the crosslinked gel body is transparent, and its mechanical properties (strength, elongation, elastic modulus, etc.) are determined by the reaction conditions (water amount, catalyst amount, temperature, etc.)
The ratio of metal alkoxide to polysiloxane (abbreviated as PSO) (abbreviated as r.
= P SO / M (OR) x, weight ratio) and P
It depends on the degree of polymerization of SO. The one with r=0 is a known inorganic glass precursor, but as r becomes larger, PSO characteristics appear and a material close to rubber-like can be obtained. As metal alkoxides, S i (OCJs) <
(tetraethoxysilane, abbreviated as TEOS), P
Polydimethylsiloxane (abbreviated as PDMS) as SO
When using PDl'lS with a molecular weight of 100,000 or less, a crosslinked gel body with flexibility at r = 1.0 can be obtained. Therefore, by changing r, it is possible to obtain crosslinked gel bodies with different mechanical properties such as elastic modulus and elongation. It is thought that some unreacted hydroxyl groups remain in the crosslinked gel, and the reaction is thought to be completed by heating to 200° C. or higher.

In order to obtain the cylindrical composition of the present invention, the reaction composition is molded when it has fluidity, or it is spun using an appropriate nozzle when the reaction has progressed to a certain extent and it has spinnability. . In the case of mold molding, if a tube with low surface energy, such as a Teflon tube, is used, it is easy to release the mold after gelation.

The diameter of the cylinder can be appropriately selected depending on the purpose of use. In the case of GRIN lenses, those with a diameter of 0.5 mm to 2 mm are used in the prior art, but in the case of the present invention, as described later, it is possible to increase the diffusion rate, so the IO It is also possible to manufacture something more than a phoenix. A GRIN lens with a large diameter can take in a large amount of light, resulting in a bright lens, which is advantageous. In the case of GRIN type optical fibers as well, if there are no problems with handling such as flexibility, thicker fibers are more advantageous in terms of light intensity, but fibers with a thickness of several tens of microns to several cranes can be manufactured.

Next, a method of forming a refractive index distribution will be explained using a specific example. Although various methods can be considered, a case will be described in which two types of metal alkoxides, for example, TEOS and tetra-h-butoxytitanium, Ti(OCaHq)4, are used. In this case, in the structure formed after the crosslinking reaction, the -Ti- structure has a higher refractive index than the -3i- structure, so by changing the composition of both in the radial direction, the refractive index distribution can be changed. is formed. Si
(OCzHs)s and Ti(OC4tl,)4 have different reaction rates of hydrolysis and subsequent polycondensation, so even if the S1(OCztls)s component completely reacts to form a crosslinked structure, Part of the Ti(OCJq)n component or its hydrolyzate remains in the monomer state. If this residual component is removed from the outer periphery of the cylinder by a diffusion method, a compositional distribution will be formed within a certain diffusion time. In the present invention, as mentioned earlier,
Since the polysiloxane is uniformly dispersed in the crosslinked gel body, unreacted T i C0CaHq) 4 is easily diffused, and a composition distribution, that is, a refractive index distribution can be formed in a short time.

The basic idea for forming the transparent cylindrical composition having a refractive index distribution according to the present invention is as described above, and various methods are possible based on this idea. For example, even when using two types of metal alkoxides, once the reaction of the first component has progressed to a certain extent, the metal alkoxide of the second component, which is a diffusion component, is added and reacted to form a cylindrical cross-linked gel body. , it is also possible to diffuse it. The diffusion method can be easily carried out by immersing a cylindrical cross-linked gel body in a solvent for the diffusion component, such as alcohol, but if an acid or base catalyst is added to the alcohol, the diffusion rate increases depending on the amount added. was found to change. Therefore, by changing the amount of catalyst, it is possible to obtain a material with a changed refractive index distribution. In order to completely fix the structure of a material in which a refractive index distribution is formed by the diffusion method, it is desirable to subject it to heat treatment at 200° C. or higher.

〔Effect of the invention〕

The transparent cylindrical composition having a refractive index distribution of the present invention has superior productivity compared to inorganic glasses, and can provide a Rondo lens with an unprecedented large diameter. It also has superior heat resistance compared to organic types. Further, by changing the amount of polysiloxane, it is possible to obtain a lens with flexibility.

〔Example〕

The present invention will be further explained below with reference to Examples.

Example 1 TEOS/PDMS/water/hydrochloric acid (35% concentration)/ethanol = 13/13/1.1310.13/11.5 (
parts by weight) in a flask equipped with a reflux tube.
The mixture was heated at 60° C. for 30 minutes to cause a reaction. PDMS was a polymethylsiloxane with a molecular weight of 1700 having a hydroxyl group at the end. After cooling the reaction to room temperature, T i (O
C4flJ 4 / ammonia water (25% concentration) / water /
Ethanol/formamide = 1310.63/3.6
A mixture of 15.75/2.4 (parts by weight) was added to the reaction mixture and further heated at 60° C. for 30 minutes to react.

After cooling the reaction mixture to room temperature, the inner diameter was 2 mm and the length was 20 mm.
The reaction mixture was filled into a Teflon tube of 100 mL, and allowed to stand at room temperature for 1 day to form a gel. The gelled transparent cylindrical composition was taken out from the Teflon tube and immersed in an ethanol solution containing hydrochloric acid for 1 hour (5 samples were obtained by varying the hydrochloric acid content).The gel rod was taken out, dried at room temperature, and then heated at 250°C. Heat treatment was performed for 1 hour. The rod thus obtained was transparent and hard like inorganic glass, and had a diameter of about 1.5 barrels.

The radial refractive index distribution of these rods was observed using an interference microscope (
Figure 1 shows the results of measurement using an Interfaco interference microscope (manufactured by Carl Zeiss).

In FIG. 1, the horizontal axis is the radial distance from the center of the rod, and the vertical axis is the refractive index (wavelength 589 nm).

The numbers in FIG. 1 indicate different hydrochloric acid contents in the immersion liquid, and the respective contents are shown in Table 1 below.

Composition of soil immersion liquid Sample magnet 5 has a refractive index distribution curve close to a quadratic curve, and has a g value Cn (rl-n
o (1--g 2r 2), no: center refractive index, n
(r): refractive index at radius r], g=0
．． It was 114.

Example 2 A gel rod was obtained in the same manner as in Example 1 using a Teflon tube with an inner diameter of 4 wm. The gel rod was immersed in an immersion liquid having the same composition as Sample Magnet 5 of Example 1 for different times to form a refractive index distribution. As in Example 1, after drying at room temperature and heat treatment at 250° C. for 1 hour, the refractive index distribution was measured using an interfaco. The results are shown in Table 2 and FIG. By this method, it was possible to obtain a GjlIN lens with a diameter of 3 or more.

, table-”-

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are graphs showing the results of measuring the refractive index distribution of the transparent cylindrical compositions of the present invention produced by the methods of Examples 1 and 2, respectively. Figure 3. Singh

Claims (1)

[Claims] 1. A transparent cylindrical composition obtained by reacting a metal alkoxide with a polysiloxane containing terminal silanol groups and having a refractive index distribution in the radial direction symmetrically with respect to the central axis.