JP2009059409A - Structural birefringent wavelength plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structural birefringent wavelength plate having excellent mechanical properties, heat resistance and chemical resistance and high manufacturing yield. <P>SOLUTION: The structural birefringent wavelength plate has a substrate and a birefringent part formed by using a composition containing a polysilane, a silicone compound and a polygermane and having a recessed and projecting periodic structure wherein wall parts and groove parts are periodically repeated. Preferably, the structural birefringent wavelength plate can exhibit a prescribed phase difference to light having a prescribed wavelength by optimizing the refractive index of the birefringent part and a pitch, a height and a packing density of the wall part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structural birefringent wave plate. More specifically, the present invention relates to a structural birefringent wave plate that has excellent mechanical properties, heat resistance and chemical resistance, and can be expected to have a high yield during production.

  Information equipment such as a player, a recorder, and a drive that reads, records, and reproduces information from and on an optical information recording medium such as a CD and a DVD includes an optical pickup device. The optical system of the optical pickup device includes a recording / reproducing optical system for recording and reproducing information signals by irradiating a minute spot on the recording medium surface, and a focusing optical for accurately imaging the minute spot on an information track on the recording medium surface. System and tracking optical system. Various optical elements are used in such an optical pickup optical system.

  For example, in the recording / reproducing optical system, a light separation device is used to separate laser light incident on an optical information recording medium and reflected laser light. Specifically, this device is used to completely guide the reflected light from the optical disk to a light detector (photodiode) without returning it to a light source such as a semiconductor laser. A typical example of the light separation device is a retardation plate (typically a quarter wave plate) for converting linearly polarized light into circularly polarized light.

  Conventionally, such a retardation plate is typically produced by accurately cutting a birefringent material such as quartz. Such a retardation plate is very difficult to manufacture and has a problem in cost. In order to solve such a problem, a structural birefringent wave plate using an uneven periodic structure having a wavelength equal to or less than the wavelength of light of interest has been proposed (see Patent Document 1).

However, the structural birefringent wave plate is made of a resin (for example, PMMA) and has extremely insufficient mechanical properties (for example, hardness), heat resistance, and chemical resistance. Further, although the refractive index of PMMA varies depending on the wavelength, it is about 1.5 at most. In order to provide a practically sufficient phase difference as a wave plate (typically a quarter wave plate), a periodic structure is used. In this case, the aspect ratio must be very large (for example, up to about 8), resulting in a problem that the yield is very low.
JP 2006-323059 A

  The present invention has been made to solve the above-described conventional problems, and its object is to have excellent mechanical properties, heat resistance and chemical resistance, and to expect a high yield during production. An object of the present invention is to provide a structural birefringent wave plate that can be formed.

  The structural birefringent wave plate of the present invention is formed from a composition comprising a substrate; polysilane, a silicone compound, and polygermane, and has a concavo-convex periodic structure in which walls and grooves are periodically repeated. A birefringent portion;

  In a preferred embodiment, the birefringent part is formed by imprinting the composition with a mold.

  In a preferred embodiment, the structural birefringent wave plate of the present invention optimizes the refractive index of the birefringent portion and the pitch, height, and filling factor of the wall portion, thereby allowing light having a predetermined wavelength. Expresses a predetermined phase difference.

  According to the present invention, a composition containing polysilane, a silicone compound, and polygermane is imprint-molded to have excellent mechanical properties, heat resistance and chemical resistance, and extremely high production yield. A high structural birefringent waveplate is provided.

  In addition, according to the present invention, a wave plate that expresses a desired phase difference with respect to light of various wavelengths can be provided. That is, it is necessary to optimize the refractive index of the birefringent portion, the pitch of the wall portion, the height, the filling rate, and the like in order to develop a desired phase difference with respect to light having a predetermined wavelength. With conventional materials and imprinting methods, it was extremely difficult to form patterns with significantly different sizes at the same time, so only a wave plate having a monotonous periodic structure could be produced, and design freedom Due to the narrowing of the degree, such a wave plate can only exhibit a predetermined phase difference with respect to light of a single wavelength. On the other hand, according to the birefringent portion material and the method for forming a birefringent portion used in the present invention, high wall portions having an aspect ratio of 5 or more are collectively collected in a wide range of pitches on the order of 10 nm to 10 μm. Can be formed. In addition, since the method for forming a birefringent portion in the present invention has extremely high mold pattern transfer accuracy, a pattern as designed can be formed accurately. Therefore, the structural birefringent wave plate of the present invention can optimize the pitch, height, filling rate, and the like of the wall so as to express a desired phase difference with respect to light of a predetermined wavelength. As a result, a desired phase difference can be expressed with respect to light of various wavelengths (for example, a flat chromatic dispersion characteristic that exhibits a substantially constant phase difference with respect to light of various wavelengths can be provided). It becomes possible.

A. Structural Birefringent Waveplate FIG. 1 is a schematic perspective view of a structural birefringent waveplate according to a preferred embodiment of the present invention. The structural birefringent wave plate 100 includes a substrate 10 and a birefringent portion 20. The birefringent portion 20 has an uneven periodic structure in which the wall portion 21 and the groove portion 22 are periodically repeated. The birefringent portion 20 is formed of a composition containing polysilane, a silicone compound, and polygermane (hereinafter also referred to as a birefringent portion material, which will be described in detail in section B below).

  Any appropriate substrate can be adopted as the substrate 10 as long as it can be used for an optical element of an optical pickup optical system. A typical example is a quartz substrate. The quartz substrate is advantageous in that it has an extremely small influence on the birefringence of the birefringent portion, has excellent light transmittance, and has excellent mechanical properties, heat resistance, and chemical resistance. The thickness of the substrate 10 can be appropriately selected according to the purpose. In one embodiment, the thickness of the substrate 10 is about 1 mm.

  As described above, the birefringent portion 20 has an uneven periodic structure in which the wall portion 21 and the groove portion 22 are periodically repeated. The height H, the pitch P, the width L, the aspect ratio (H / L), and the filling rate f (= L / P) of the wall portion 21 seem to exhibit a predetermined phase difference with respect to light having a predetermined wavelength. Can be optimized. Since these are optimized in relation to each other, these preferred values and ranges can vary depending on the purpose. For example, if the pitch, width, and filling factor of the wall portion are fixed, a wave plate that expresses a desired phase difference can be obtained by changing the refractive index of the birefringent portion and the height and aspect ratio of the wall portion. Can do. For example, when the wall pitch P is 500 nm, the width L is 250 nm, the filling factor f (= L / P) is 0.5, and a quarter-wave plate for 700 nm light is intended, The refractive index of the refractive part is preferably 1.56-1.83, the height H of the wall part is preferably 1500-3000 nm, and the aspect ratio is preferably 6-12. When a half-wave plate for 700 nm light is intended, the refractive index of the birefringent part is preferably 1.56-1.83, and the height H of the wall part is preferably 750-1500 nm. The aspect ratio is preferably 3-6. A specific structure is shown below: In one embodiment, when the refractive index of the birefringent portion is 1.830 at a wavelength of 632 nm and a quarter wavelength plate for 700 nm light is intended, The height H can be about 750 nm, the pitch P can be about 500 nm, the width L can be about 250 nm, the aspect ratio can be about 3, and the filling factor can be about 0.5. In another embodiment, when the refractive index of the birefringent part is 1.695 at a wavelength of 632 nm and a quarter wave plate for 700 nm light is intended, the height H is about 1000 nm; The pitch P can be about 500 nm, the width L can be about 250 nm, the aspect ratio can be about 4, and the filling factor can be about 0.5. According to these embodiments, since the aspect ratio can be reduced, an advantage that the yield in manufacturing is excellent can be obtained. In yet another embodiment, when the refractive index of the birefringent portion is 1.614 at a wavelength of 632 nm and a quarter wave plate for 700 nm light is intended, the height H is about 1250 nm. The pitch P can be about 500 nm, the width L can be about 250 nm, the aspect ratio can be about 5, and the filling factor can be about 0.5. In still another embodiment, when the refractive index of the birefringent portion is 1.560 at a wavelength of 632 nm and a quarter-wave plate for 700 nm light is intended, the height H is about 1500 nm. The pitch P can be about 500 nm, the width L can be about 250 nm, the aspect ratio can be about 6, and the filling factor can be about 0.5. In still another embodiment, when the refractive index of the birefringent portion is 1.695 at a wavelength of 632 nm and a half-wave plate for 700 nm light is intended, the height H is about 2000 nm. The pitch P can be about 500 nm, the width L can be about 250 nm, the aspect ratio can be about 8, and the filling factor can be about 0.5. In the present invention, the formability of the material for the birefringent portion is extremely excellent, so that even a wall portion having a large aspect ratio (for example, 8) can be formed satisfactorily.

  In one embodiment, a plurality of birefringent portions 20 having different pitches of the wall portions 21 may be provided on the substrate 10 (not shown). The birefringent portion material used in the present invention is extremely excellent in moldability, and for example, a plurality of patterns (thus, pitch) having different sizes from the order of 10 nm to the order of 10 μm can be formed by imprinting. Therefore, such a configuration can be easily realized.

  The refractive index of the birefringent portion 20 is preferably 1.56 or more, more preferably 1.63 or more, further preferably 1.65 or more, particularly preferably 1.67 or more, and most preferably. Is 1.69 or more. By having such a refractive index, the aspect ratio necessary for obtaining a desired phase difference can be made very small. As a result, the yield at the time of manufacturing the wave plate can be made extremely high. The refractive index can be measured by any appropriate method (for example, reflection spectroscopy, ellipsometry, prism coupler method). Furthermore, the hardness of the birefringent portion 20 is preferably 120 HV or more, more preferably 140 HV or more, and further preferably 200 HV or more. In addition, the light transmittance of the birefringent portion 20 is preferably 90% or more, more preferably 95% or more in the visible region. According to the present invention, such a high refractive index and high hardness birefringent portion can be easily produced with a very high yield.

The expression mechanism of the phase difference δ of the structural birefringent wave plate of the present invention can be expressed by the following formula:
δ = (n _TE −n _TM ) × (H / λ)
n _TE = {f × n ₁ ² + (1−f) × n ₂ ² } ^1/2
n _TM = {f / n ₁ ² + (1−f) / n ₂ ² } ^−1/2
n _TE is an effective refractive index of light having a polarization parallel to a direction having a period (a direction parallel to the wall), and n _TM is an effective refraction of light having a period (a direction perpendicular to the wall). Rate. Here, as described above, H is the height of the wall 21, P is the pitch of the wall 21, f is the filling rate (L / P) of the wall 21, and L is the wall 21. Width. Furthermore, λ is the wavelength of light, n ₁ is the refractive index of air (= 1), and n ₂ is the refractive index of the birefringent portion. As is clear from such a mechanism, according to the present invention, the refractive index of the birefringent portion can be made extremely high, so that the wall portion height H does not have to be so high (that is, the aspect ratio). A desired phase difference can be obtained. One of the major achievements of the present invention is that such a birefringent portion is actually formed.

B. Birefringent Material As described above, the birefringent material used in the present invention includes polysilane, a silicone compound, and polygermane.

B-1. Polysilane As used herein, “polysilane” refers to a polymer whose main chain is composed solely of silicon atoms. The polysilane used in the present invention may be a linear type or a branched type. A branched type is preferred. This is because it has excellent solubility in a solvent, compatibility with polygermane and a silicone compound, and excellent film forming properties. The branched type and the straight type are distinguished by the bonding state of Si atoms contained in the polysilane. The branched polysilane is a polysilane containing Si atoms having 3 or 4 bonds to adjacent Si atoms (number of bonds). On the other hand, in the linear polysilane, the number of bonds between Si atoms and adjacent Si atoms is two. Usually, since the valence of Si atom is 4, among Si atoms existing in polysilane, those having 3 or less bonds are replaced by organic substitution such as hydrogen atom, hydrocarbon group, alkoxy group, etc. in addition to Si atom. Bonded to a group. Specific examples of the preferable hydrocarbon group include an aliphatic hydrocarbon group having 1 to 10 carbon atoms and an aromatic hydrocarbon group having 6 to 14 carbon atoms which may be substituted with halogen. Specific examples of the aliphatic hydrocarbon group include a chain hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, and a nonafluorohexyl group, and , An alicyclic hydrocarbon group such as a cyclohexyl group and a methylcyclohexyl group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group. Examples of the alkoxy group include those having 1 to 8 carbon atoms. Specific examples include a methoxy group, an ethoxy group, a phenoxy group, and an octyloxy group. Among these, a methyl group and a phenyl group are particularly preferable in consideration of ease of synthesis. For example, polymethylphenylsilane, polydimethylsilane, polydiphenylsilane and copolymers thereof can be suitably used. For example, the refractive index of the birefringent part can be adjusted by changing the structure of polysilane. For example, a birefringent part having a higher refractive index can be obtained by introducing many diphenyl groups by copolymerization.

  The branched polysilane preferably has a degree of branching of 2% or more, more preferably 5% to 40%, and particularly preferably 10% to 30%. When the degree of branching is less than 2%, the solubility is low, and microcrystals are likely to be formed in the resulting film, and the microcrystals cause scattering, which may result in insufficient transparency. is there. If the degree of branching is too large, polymerization of the high molecular weight substance may be difficult, and absorption in the visible region may increase due to branching. In the preferable range, the higher the degree of branching, the higher the light transmittance. In the present specification, “the degree of branching of polysilane” refers to the ratio of Si atoms having 3 or 4 bonds with adjacent Si atoms to the total number of Si atoms in the branched polysilane. Here, for example, “the number of bonds with adjacent Si atoms is three” means that three of the bonds of Si atoms are bonded to Si atoms.

  The polysilane used in the present invention is produced by a polycondensation reaction by heating a halogenated silane compound to 80 ° C. or higher in an organic solvent such as n-decane or toluene in the presence of an alkali metal such as sodium. be able to. Further, it can also be synthesized by an electrolytic polymerization method or a method using metal magnesium and metal chloride.

  The branched polysilane can be obtained, for example, by heating and polycondensing a halosilane mixture containing an organotrihalosilane compound, a tetrahalosilane compound, and a diorganodihalosilane compound. The degree of branching of the branched polysilane can be adjusted by adjusting the amounts of the organotrihalosilane compound and the tetrahalosilane compound in the halosilane mixture. For example, a branched polysilane having a degree of branching of 2% or more can be obtained by using a halosilane mixture in which the organotrihalosilane compound and the tetrahalosilane compound are 2 mol% or more of the total amount. Here, the organotrihalosilane compound is a Si atom source having 3 bonds with adjacent Si atoms, and the tetrahalosilane compound is a Si atom source having 4 bonds with adjacent Si atoms. The branched structure of the branched polysilane can be confirmed by measuring an ultraviolet absorption spectrum or a nuclear magnetic resonance spectrum of silicon.

  The halogen atom that each of the organotrihalosilane compound, tetrahalosilane compound, and diorganodihalosilane compound has is preferably a chlorine atom. Examples of the substituent other than the halogen atom that the organotrihalosilane compound and the diorganodihalosilane compound have include the above-described hydrogen atom, hydrocarbon group, alkoxy group, or functional group.

  The branched polysilane is not particularly limited as long as it is soluble in an organic solvent, is compatible with a silicone compound and polygermane, and can form a transparent film by coating.

  The weight average molecular weight of the polysilane is preferably 5,000 to 50,000, and more preferably 10,000 to 20,000.

  The polysilane may contain a silane oligomer as necessary. The silane oligomer content in the polysilane is preferably 5% by weight to 25% by weight. By containing the silane oligomer in such an amount, molding at a lower temperature becomes possible. When the amount of the oligomer exceeds 25% by weight, flow or the like may occur in the heating step during processing.

  The weight average molecular weight of the silane oligomer is preferably 200 to 3000, and more preferably 500 to 1500.

B-2. Silicone Compound As the silicone compound, any suitable silicone compound that is compatible with polysilane, polygermane, and an organic solvent and can form a transparent film can be adopted. In one embodiment, the silicone compound is a compound represented by the following general formula:

[Wherein, R ₁ to R ₁₂ each independently represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms and an aromatic hydrocarbon having 6 to 12 carbon atoms which may be substituted with a halogen or a glycidyloxy group. A group selected from the group consisting of a group and an alkoxy group having 1 to 8 carbon atoms. a, b, c and d are integers each including 0 and satisfy a + b + c + d ≧ 1. ]

  Specific examples include those obtained by hydrolytic condensation of two or more types of dichlorosilane called D-form having two organic substituents and trichlororosilane called T-form having one organic substituent.

  Specific examples of the aliphatic hydrocarbon group include a chain hydrocarbon group such as a methyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, a glycidyloxypropyl group, and a cyclohexyl group. And alicyclic hydrocarbon groups such as methylcyclohexyl group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, and a biphenyl group. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, a phenoxy group, an octyloxy group, and a ter-butoxy group.

The types of R ₁ to R ₁₂ and the values of a, b, c, and d can be appropriately selected according to the purpose. For example, compatibility can be improved by introducing the same group as the hydrocarbon group of polysilane into the silicone compound. Therefore, for example, when a phenylmethyl polysilane is used as the polysilane, it is preferable to use a phenylmethyl or diphenyl silicone compound. In addition, for example, a silicone compound having two or more alkoxy groups in one molecule (specifically, a silicone compound in which at least two of R ₁ to R ₁₂ are alkoxy groups having 1 to 8 carbon atoms) is used as a crosslinking agent. Is available. Specific examples of such silicone compounds include methylphenylmethoxysilicone and phenylmethoxysilicone containing 15% to 35% by weight of alkoxy groups. In this case, the content of the alkoxy group can be calculated from the average molecular weight of the silicone compound and the molecular weight of the alkoxy unit.

  The weight average molecular weight of the silicone compound is preferably 100 to 10,000, and more preferably 100 to 3000.

  In one embodiment, the silicone compound optionally includes a double bond-containing silicone compound. The content of the double bond-containing silicone compound in the silicone compound is preferably 20% by weight to 100% by weight, and more preferably 50% by weight to 100% by weight. By using the double bond-containing silicone compound in such a range, the reactivity at the time of energy ray irradiation is increased, and processing at a lower temperature or lower illuminance becomes possible. In addition, in the case of a composition in which the silicone compound is increased with respect to the polysilane, it is possible to prevent fluidization and disappearance during heat treatment due to a decrease in solidity.

  The weight average molecular weight of the double bond-containing silicone compound is preferably 100 to 10,000, and more preferably 100 to 5000.

  The chemical group providing a double bond in the double bond-containing silicone compound is preferably a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group. For example, a silicone compound generally called a silane coupling agent and having a double bond can be used. In this case, the iodine value is preferably 10 to 254. The number of double bonds in one molecule of the silicone compound may be two or more. Such a silicone compound can be used as a crosslinking agent. Specific examples of such silicone compounds include vinyl group-containing methylphenyl silicone resins containing 1% to 30% by weight of double bonds.

  A commercially available product can be used as the double bond-containing silicone compound. For example, the compounds shown in Table 1 below can be used.

  The above-mentioned silicone compound is contained in the birefringent part material in a weight ratio of polysilane / silicone compound of preferably 80:20 to 5:95, more preferably 70:30 to 40:60. By including the silicone compound in such a range, a film that is sufficiently cured, has very few cracks, and has high transparency can be obtained.

B-3. Polygerman In this specification, “polygerman” refers to a polymer whose main chain is composed only of germanium atoms. The polygermane used in the present invention may be linear or branched. A branched type is preferred. This is because it has excellent solubility in a solvent, compatibility with polysilane and silicone compound, and excellent film forming properties. A branched type and a linear type are distinguished by the bonding state of Ge atoms contained in polygermane. The branched polygermane is a polygermane containing Ge atoms having 3 or 4 bonds to adjacent Ge atoms (number of bonds). On the other hand, in the linear polygermane, the number of bonds between Ge atoms and adjacent Ge atoms is two. Usually, the Ge atom has a valence of 4. Among the Ge atoms present in polygermane, those having a bond number of 3 or less are organic atoms such as hydrogen atoms, hydrocarbon groups, and alkoxy groups in addition to Ge atoms. It is bonded to a substituent. Specific examples of the preferable hydrocarbon group include an aliphatic hydrocarbon group having 1 to 10 carbon atoms and an aromatic hydrocarbon group having 6 to 14 carbon atoms which may be substituted with halogen. Specific examples of the aliphatic hydrocarbon group include a chain hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, and a nonafluorohexyl group, and , An alicyclic hydrocarbon group such as a cyclohexyl group and a methylcyclohexyl group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group. Examples of the alkoxy group include those having 1 to 8 carbon atoms. Specific examples include a methoxy group, an ethoxy group, a phenoxy group, and an octyloxy group. Among these, a methyl group and a phenyl group are particularly preferable in consideration of ease of synthesis. For example, polymethylphenyl germane, polydimethylgermane, polydiphenylgermane and copolymers thereof can be suitably used. For example, the refractive index of the birefringent part can be adjusted by changing the structure of polygermane.

  The branched polygermane has a degree of branching of preferably 2% or more, more preferably 5% to 70%, and particularly preferably 10% to 30%. When the degree of branching is less than 2%, the solubility is low, and microcrystals are likely to be formed in the resulting film, and the microcrystals cause scattering, which may result in insufficient transparency. is there. If the degree of branching is too large, polymerization of the high molecular weight substance may be difficult, and absorption in the visible region may increase due to branching. In the preferable range, the higher the degree of branching, the higher the light transmittance. In the present specification, the “degree of branching of polygermane” refers to the ratio of Ge atoms having 3 or 4 bonds to adjacent Ge atoms to the total number of Ge atoms in the branched polygermane. . Here, for example, “the number of bonds with adjacent Ge atoms is 3” means that three of the bonds of Ge atoms are bonded to Ge atoms.

  The polygermane used in the present invention is produced by a polycondensation reaction by heating a halogenated germane compound in an organic solvent such as n-decane or toluene in the presence of an alkali metal such as sodium. can do. Basically, a synthesis method similar to that of the polysilane can be used.

  The branched polygermane can be obtained, for example, by heating and polycondensing a halogermane mixture containing an organotrihalogermane compound, a tetrahalogermane compound and a diorganodihalogermane compound. The degree of branching of the branched polysilane can be adjusted by adjusting the amounts of the organotrihalogermane compound and the tetrahalogermane compound in the halogermane mixture. For example, a branched polygermane having a branching degree of 2% or more can be obtained by using a halogermane mixture in which the organotrihalogermane compound and the tetrahalogermane compound are 2 mol% or more of the total amount. Here, the organotrihalogerman compound is a Ge atom source having 3 bonds with adjacent Ge atoms, and the tetrahalogerman compound is a Ge atom source having 4 bonds with adjacent Ge atoms. The branched structure of the branched polygermane can be confirmed by, for example, an ultraviolet absorption spectrum.

  The halogen atom that each of the organotrihalogermane compound, tetrahalogermane compound, and diorganodihalogermane compound has is preferably a chlorine atom. Examples of the substituent other than the halogen atom that the organotrihalogermane compound and the diorganodihalogermane compound have include the above-described hydrogen atom, hydrocarbon group, alkoxy group, or functional group.

  The branched polygermane is not particularly limited as long as it is soluble in an organic solvent, is compatible with a silicone compound and polysilane, and can form a transparent film by coating.

  The polygermane preferably has a weight average molecular weight of 3000 to 50000, more preferably 5000 to 20000.

  The polygermane may contain a germane oligomer as necessary. The germane oligomer content in the polygermane is preferably 5% to 25% by weight. By containing the germane oligomer in such an amount, molding at a lower temperature becomes possible. When the amount of the oligomer exceeds 25% by weight, flow or the like may occur in the heating step during processing.

  The weight average molecular weight of the germane oligomer is preferably 200 to 3000, more preferably 500 to 2000.

  The polygerman may be used in a ratio of preferably 10 parts by weight to 150 parts by weight, more preferably 70 parts by weight to 120 parts by weight with respect to 100 parts by weight of the total of the polysilane and the silicone compound. By using polygermane in such a range, a birefringent portion having a very high refractive index can be obtained.

B-4. Solvent The material for a birefringent part generally contains a solvent. The solvent is preferably an organic solvent. Preferred organic solvents include hydrocarbon solvents having 5 to 12 carbon atoms, halogenated hydrocarbon solvents, and ether solvents. Specific examples of the hydrocarbon solvent include aliphatic solvents such as pentane, hexane, heptane, cyclohexane, n-decane, and n-dodecane, and aromatic solvents such as benzene, toluene, xylene, and methoxybenzene. . Specific examples of the halogenated hydrocarbon solvent include carbon tetrachloride, chloroform, 1,2-dichloroethane, dichloromethane, chlorobenzene and the like. Specific examples of the ether solvent include diethyl ether, dibutyl ether, tetrahydrofuran and the like. The amount of the solvent used is preferably in a range such that the total concentration of polysilane, silicone compound and polygermane in the composition is 10% to 50% by weight.

B-5. Other Additives The birefringent material may further contain any appropriate additive depending on the purpose. Typical examples of additives include sensitizers, surface conditioners, metal oxide particles for adjusting hardness, and the like. A typical example of the sensitizer is an organic peroxide. As the organic peroxide, any appropriate compound can be adopted as long as it is a compound that can efficiently insert oxygen between the Si—Si bonds of polysilane and the Ge—Ge bond of polygermane. Examples thereof include peroxy ester peroxides and organic peroxides having a benzophenone skeleton. More specifically, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone (hereinafter referred to as “BTTB”) is preferably used. Further, the organic peroxide acts on the double bond of the double bond-containing silicone compound and has an effect of promoting the addition polymerization reaction between the double bonds.

  The sensitizer may be used in a proportion of preferably 1 to 30 parts by weight, more preferably 2 to 10 parts by weight, based on 100 parts by weight of the total of the polysilane and the silicone compound. By using a sensitizer in such a range, the oxidation of polysilane is promoted even in a non-oxidizing atmosphere, and a molded article or optical element having extremely excellent hardness can be formed at low temperature, low pressure, and in a short time. .

  Specific examples of the surface conditioner include fluorine-based surfactants. The surface conditioner may be used in a proportion of preferably 0.01 part by weight to 0.5 part by weight with respect to 100 parts by weight of the total of the polysilane and the silicone compound. By using a surface conditioner, the applicability of the birefringent material can be improved.

  Any appropriate particles can be used as the metal oxide particles as long as the effects of the present invention can be obtained. Specific examples of the metal constituting the metal oxide include lithium (Li), copper (Cu), zinc (Zn), strontium (Sr), barium (Ba), aluminum (Al), yttrium (Y), indium ( In), cerium (Ce), silicon (Si), titanium (Ti), zirconium (Zr), tin (Sn), niobium (Nb), antimony (Sb), tantalum (Ta), bismuth (Bi), chromium ( Cr), tungsten (W), manganese (Mn), iron (Fe), nickel (Ni), ruthenium (Ru) and alloys thereof. The composition of oxygen in the metal oxide is determined according to the valence of the metal. As the metal oxide, zircon oxide, titanium oxide and / or zinc oxide can be suitably used. By using these, it is possible to obtain a composition capable of forming a molded article having very excellent hardness.

  The average particle diameter of the metal oxide particles is preferably 1 nm to 100 nm, and more preferably 1 nm to 50 nm. By using metal oxide particles having an average particle diameter in such a range, it is possible to form a birefringent portion particularly excellent in hardness and transparency.

  The metal oxide particles are contained in the birefringent part material in a proportion of preferably 50 parts by weight to 500 parts by weight, more preferably 100 parts by weight to 300 parts by weight with respect to 100 parts by weight of the total of the polysilane and the silicone compound. Is done. By containing the metal oxide particles in such a range, it is possible to obtain a birefringent material having excellent both hardness and coating film forming characteristics.

  The metal oxide particles can be obtained using any appropriate method. For example, it can be formed using a wet method, a baking method, or the like. Moreover, you may use a commercial item for the said metal oxide particle. As a specific example of a commercial item, the brand name nano zirconia dispersion liquid NZD-8J61 by Sumitomo Osaka Cement Co., Ltd. is mentioned.

C. Hereinafter, a method for forming the birefringent portion 20 will be described. 2A to 2E are schematic views for explaining the procedure of the method for forming a birefringent portion according to a preferred embodiment of the present invention.

  First, as shown in FIG. 2A, the birefringent material 20 ′ described in the above section B is applied to the substrate 10. Arbitrary appropriate methods may be employ | adopted as a coating method of the material for birefringence parts. A typical example is spin coating. The coating thickness of the birefringent part material is preferably larger than the height of the fine pattern of the birefringent part molding mold. For example, when the height of the fine pattern portion of the mold is 1.0 μm, the coating thickness of the birefringent portion material is preferably about 1.1 μm to 2.0 μm. The coating thickness of the birefringent part material can be controlled by adjusting the concentration of the birefringent part material and the rotation speed of the spin coater.

  Next, as shown in FIG. 2B, a mold 30 on which a fine pattern corresponding to a desired uneven periodic structure of the birefringent portion is formed is pressed against the applied birefringent portion material 20 ′. The pressure welding is preferably performed near room temperature. By using the birefringent material as described above and performing a series of processes described later, it is possible to perform pressure welding near normal temperature. Since pressure welding near room temperature can minimize the time required for temperature increase and decrease, the processing time of the nanoimprint process can be greatly shortened. Furthermore, the advantage of pressure welding near normal temperature is that the expansion and contraction of the material (mold, substrate, birefringence material) due to temperature change is very small, so the thermal change of the fine pattern during transfer is extremely well prevented. There is to be able to be done. In one embodiment, the pressure welding temperature is room temperature to 80 ° C., the pressure welding pressure is 1 MPa to 3 MPa, and the pressure welding time is 5 seconds to 15 seconds. In the present invention, it is preferable to perform heat treatment (so-called pre-bake treatment) on the material for the birefringence part before pressure welding. As pre-bake treatment conditions, for example, the heating temperature is 50 ° C. to 100 ° C. The time is 3-7 minutes.

  The mold 104 is preferably made of an energy ray transmissive material, more preferably a light transmissive material for aligning the mold and the lower substrate. Specific examples of the material constituting the mold include quartz glass and a Si substrate excellent in workability.

  Next, as shown in FIG. 2C, energy rays (typically ultraviolet rays, which will be described later) are irradiated in a state where the mold 30 and the birefringent portion material 20 ′ are pressed. As a result, the birefringent material is vitrified. Typically, the energy beam irradiation is performed from the substrate 10 side. By irradiating energy rays from the substrate 10 side, the birefringent material as a whole undergoes oxidation (typically photooxidation) until the pattern of the mold is sufficiently fixed, and the birefringent portion in the vicinity of the substrate 10 As for the material, for example, when a quartz substrate is used, a Si—O—Si bond can be formed even with Si atoms of the substrate, and very strong adhesion can be realized. In addition, for the birefringent material in the vicinity of the mold 30, it is possible to suppress the progress of oxidation (typically photooxidation) by selecting an appropriate amount of light irradiation and to ensure excellent releasability from the mold. Can do. As a result of leaving a non-photo-oxidized part at the interface between the mold and the birefringent part material, the mold and the birefringent part material can be released without being fixed, and the birefringent part can be obtained with a very high yield. Can be formed. In addition, in the present invention, since the aspect ratio of the birefringent portion can be reduced, the yield can be further improved.

  Representative examples of the energy rays include light (visible light, infrared rays, ultraviolet rays), electron beams, and heat. In the present invention, ultraviolet rays are particularly preferably used. The ultraviolet rays preferably have a wavelength spectrum peak of 365 nm or less. Specific examples of the ultraviolet light source include an ultra-high pressure mercury lamp and a halogen lamp. In one embodiment, when the application thickness of the birefringent material is about 2 μm, irradiation with ultraviolet light having a horizontal radiation intensity of 105 μW / cm (wavelength λ = 360 nm to 370 nm) is performed for about 3 minutes. Vitrification can be performed.

  Next, the mold 30 is released from the birefringent material 20 ′. As described above, since the material for the birefringent portion in the vicinity of the mold is moderately suppressed, the mold release is extremely easy, and the pattern loss and the yield reduction during the release can be remarkably suppressed. . In addition, as shown in FIG. 2D, when the mold is released, the uneven periodic structure of the birefringent portion is formed sufficiently satisfactorily in appearance.

  Here, the oxygen plasma may be irradiated to the birefringent portion material 20 ′ on which a predetermined uneven periodic structure is formed, if necessary. By irradiating oxygen plasma, a sufficient amount of oxygen is supplied to the birefringent material in the vicinity of the mold that has not been oxidized, and as a result, a hard oxide film is formed on the surface. As a result, the deformation of the formed irregular periodic structure is prevented very well. The thickness of the oxide film formed by the plasma treatment is, for example, 2 nm to 3 nm. The oxygen plasma irradiation conditions are, for example, an oxygen flow rate of 800 cc, a chamber pressure of 10 Pa, an irradiation time of 1 minute, and an output of 400 W.

  Next, as necessary, as shown in FIG. 2D, the opposite side of the substrate 10 (that is, the mold 30 is pressed against the birefringent portion material 20 ′ on which a predetermined uneven periodic structure is formed. Irradiate energy rays (typically ultraviolet rays) from the side that had been exposed. By the ultraviolet irradiation, the photo-oxidation of the birefringent material in the vicinity of the mold is substantially completed, and the pattern (uneven periodic structure) surface is sufficiently oxidized. In one embodiment, the ultraviolet irradiation can be performed in the presence of ozone. By performing ultraviolet irradiation in the presence of ozone, a chemical oxidation reaction by ozone proceeds in addition to a photo-oxidation reaction by ultraviolet irradiation, and oxidation of the unreacted pattern surface can be completed very well.

  Preferably, after the energy ray irradiation from the mold side, a heat treatment (so-called post-bake treatment) can be further performed. By performing the post-bake treatment, an oxidation reaction (thermal oxidation) due to heat occurs in addition to the oxidation reaction (photo-oxidation) due to the ultraviolet irradiation. As a result, the oxidation further proceeds and a very hard vitrification can be realized (see FIG. 2 (e)). In one embodiment, the post-baking conditions are such that the heating temperature is preferably 150 ° C. to 450 ° C., and the heating time is 3 minutes to 10 minutes. The heating temperature can be changed according to the purpose. For example, chemical resistance can be imparted to the resulting birefringent portion by post-baking at 150 ° C. to 200 ° C. Further, for example, by performing post-baking at 400 ° C., a birefringent part having a Vickers hardness comparable to that of a low melting glass can be obtained.

  As described above, the birefringent portion 20 having an uneven periodic structure in which the wall portion 21 and the groove portion 22 are periodically repeated is formed. Practically, since the coating thickness of the birefringent portion material is larger than the pattern height of the molding mold as described above, the obtained birefringent portion 20 can include a portion 23 where the remaining coating film is cured.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 1)
1. Synthesis of polysilane A 1000 ml flask equipped with a stirrer was charged with 400 ml of toluene and 13.3 g of sodium. The contents of this flask were heated to 111 ° C. in a yellow room shielded from ultraviolet rays, and the sodium was finely dispersed in toluene by stirring at high speed. Polymerization was carried out by adding 42.1 g of phenylmethyldichlorosilane and 4.1 g of tetrachlorosilane and stirring for 3 hours. Then, excess sodium was inactivated by adding ethanol to the obtained reaction mixture. After washing with water, the separated organic layer was put into ethanol to precipitate polysilane. The obtained crude polysilane was reprecipitated from ethanol three times to obtain a branched polymethylphenylsilane having a weight average molecular weight of 11600 and containing 10% of an oligomer.

2. Synthesis of polygermane A 100 ml flask equipped with a stirrer was charged with 40 ml of toluene and 3.14 g of sodium. The contents of this flask were heated to 111 ° C. in a yellow room shielded from ultraviolet rays, and the sodium was finely dispersed in toluene by stirring at high speed. Polymerization was carried out by adding 9.3 g of phenylmethyldichlorogermane and 2.6 g of phenyltrichlorogermane and stirring for 2 hours. Then, excess sodium was deactivated by adding 30 ml of 2-propanol to the obtained reaction mixture. Furthermore, polygermane was precipitated by throwing the reaction product into 200 ml of 2-propanol with stirring. The obtained crude polygermane was reprecipitated three times from ethanol to obtain a 20% branched polymethylphenyl / phenylgermane having a weight average molecular weight of 10,000 and containing 10% of oligomers.

3. Preparation of birefringent part material 66.6 parts by weight of polymethylphenylsilane (PMPS) obtained as described above, vinyl group-containing phenylmethylsilicone resin (trade name “KR-2020”, Mw = 2900, iodine value) = 61) 33.4 parts by weight and 5 parts by weight of organic peroxide BTTB (manufactured by NOF Corporation, solid content 20% by weight) in methoxybenzene (trade name “anisole-S”, manufactured by Kyowa Hakko Chemical Co., Ltd.) It was dissolved so as to be 77% by weight. On the other hand, a methylphenyl germane / phenylgermane copolymer (copolymerization ratio: 8/2, branched type) obtained as described above was prepared. The solution and the copolymer were mixed so that the solid content ratio (weight ratio) was 50/50 to prepare a birefringent material.

4). Production of Structural Birefringent Wavelength Plate The birefringent material obtained as described above was spin-coated on the quartz substrate surface at 2500 rpm for 40 seconds to obtain a coating film having a thickness of about 2 μm. A Si mold in which a pattern of an uneven structure (wall height H: 1130 nm, pitch P: 500 nm, width L: 250 nm) formed by periodically repeating a wall portion and a groove portion is applied under a pressure of 2 MPa. And pressed against the coating film. Next, the birefringent material was completely vitrified by UV irradiation, O ₂ plasma treatment, and heat treatment to form a birefringent portion. In this way, a structural birefringent wave plate was produced. The birefringent portion of the structural birefringent wave plate was transferred very well without the mold pattern being lost or deformed. In addition, when a large number of structural birefringent wave plates were produced by the same production procedure, the yield was extremely high. When the refractive index at a wavelength of 632 nm of the birefringent part was determined using a measuring instrument (Filmtec 4000 manufactured by SCI) employing biaxial reflection spectroscopy, the refractive index was 1.695. Furthermore, it was confirmed that the obtained structural birefringent wave plate exhibited a phase difference of about 170 nm with respect to light having a wavelength of 700 nm, and functioned very well as a quarter wave plate.

Further, the birefringent part material prepared as described above was cured by heating at 250 ° C. for 30 minutes, and then subjected to the following evaluation:
(1) Heat resistance The material for birefringence parts after curing was heat-treated, and the shrinkage rate by heating was examined. In the heat treatment at 250 ° C. for 5 minutes, the shrinkage rate was zero, and in the heat treatment at 350 ° C. for 5 minutes, the shrinkage rate was 5%. Thus, the birefringent material used in this example showed excellent heat resistance after curing.
(2) Mechanical properties Micro Vickers hardness was measured and evaluated. The Vickers hardness of the birefringent material after curing was 310 HV, which was about three times that of PMMA. Thus, the birefringent material used in this example exhibited excellent mechanical properties (hardness) after curing.
(3) Light transmittance The transmittance was measured by a usual method. As a result, the visible light transmittance of the birefringent part material after curing was about 90% or more, and the transmittance of deep ultraviolet light having a wavelength of 300 nm was 70% or more. Thus, the birefringent material used in this example had excellent transparency not only in the visible region but also in the deep ultraviolet region after curing.
(4) Chemical resistance The cured birefringent material was ultrasonically cleaned in acetone for 5 minutes. The composition used in this example maintained its shape substantially completely after ultrasonic cleaning.
The cured birefringent material was immersed in a 10% HCl aqueous solution, a 10% NaOH aqueous solution, and a 5% HF aqueous solution for 30 minutes. As a result, the birefringent part material used in this example maintained its shape substantially completely in any solution treatment. Thus, the birefringent material used in this example had very good chemical resistance after curing.

(Example 2)
A structural birefringent wavelength plate was produced in the same manner as in Example 1 except that the height H of the wall was 900 nm. The obtained structural birefringent wave plate exhibited a phase difference of about 140 nm with respect to light having a wavelength of 700 nm.

(Comparative Example 1)
A structural birefringent wave plate was produced in the same manner as in Example 1 except that the birefringent material was prepared without using the methylphenylgermane / phenylgermane copolymer. The obtained structural birefringent wave plate showed only a phase difference of about 80 nm with respect to light having a wavelength of 700 nm, and was not a practical level as a quarter wave plate.

(Comparative Example 2)
Using PMMA, a structural birefringent wavelength plate having the same uneven periodic structure as in Example 1 was produced. The obtained structural birefringent wave plate showed only a phase difference of about 50 nm with respect to light having a wavelength of 700 nm, and was not a practical level as a quarter wave plate. Further, this wave plate is insufficient in hardness, heat resistance and chemical resistance.

  The structural birefringent wave plate of the present invention can be suitably used for an optical pickup optical system, for example.

1 is a schematic perspective view of a structural birefringent wave plate according to a preferred embodiment of the present invention. FIG. It is a schematic diagram explaining the formation procedure of the birefringent part of the structural birefringent wave plate by preferable embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Structural birefringence wavelength plate 10 Substrate 20 Birefringence part 21 Wall part 22 Groove part

Claims (3)

Structural birefringence wavelength formed from a composition comprising a substrate, a polysilane, a silicone compound, and polygermane, having a birefringent portion having a concavo-convex periodic structure in which a wall portion and a groove portion are periodically repeated. Board.   The structural birefringent wave plate according to claim 1, wherein the birefringent portion is formed by imprinting the composition with a mold. The predetermined phase difference is expressed with respect to light having a predetermined wavelength by optimizing the refractive index of the birefringent portion and the pitch, height, and filling rate of the wall portion. The structural birefringent wave plate as described.

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