JP3460317B2 - Diffraction grating and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffraction grating excellent in optical characteristics, heat resistance and low water absorption, and more particularly to a diffraction grating suitable for optical applications such as a spectroscope and a laser.

[0002]

2. Description of the Related Art Conventionally, in the transmission type, a diffraction grating is scratched in parallel with the surface of a glass plate, or a resist is applied to the surface of the glass plate, and an uneven pattern is optically written on this, or the resist is written on the resist. After removing the resist after etching the glass using the patterned pattern is used by taking advantage of the optical properties such as surface smoothness , heat resistance, low hygroscopicity, transparency, etc., but the manufacturing process is complicated and expensive. However, it has a drawback that it is heavy and breaks at the time of assembly, and it is cracked by impact when used as a final product. In the conventional diffraction grating, the reflection type is a mirror-like metal surface with a metallic luster, and is scratched mechanically in parallel with a needle-shaped surface, or the metal surface is etched using the pattern written on the resist. Is used by taking advantage of optical characteristics such as surface smoothness, heat resistance, low hygroscopicity, and high reflectivity, but it has the drawbacks of complicated manufacturing process, high cost, and heavy weight. It was Therefore, it has been proposed to use a transparent thermoplastic resin as a diffraction grating, but for example, in polymethylmethacrylate, deformation due to water absorption and a change in refractive index occur, and in polycarbonate, since the softness of the shape of the mold is insufficient, There was a problem that it was difficult to form irregularities on the surface, and birefringence occurred due to residual strain during molding and strain during clamping of the molded product.

[0003]

SUMMARY OF THE INVENTION The present invention solves these problems all at once and provides a diffraction grating excellent in optical characteristics, heat resistance and low water absorption.

[0004]

The present invention provides the following formula (V):
Hydrogenation obtained by hydrogenating a polymer obtained by metathesis polymerization of at least one tetracyclododecene derivative represented by or the tetracyclododecene derivative and an unsaturated cyclic compound copolymerizable therewith Diffraction grating, which is made of a polymer and has parallel linear irregularities on the surface at intervals of 0.1 to 1000 μm, and, if necessary, a metal having a metallic luster with a light reflectance of 50% or more on the surface. Alternatively, the diffraction grating and the intrinsic viscosity (η _inh ) of claim 1, wherein a thin film of a metal oxide is deposited, is 0.2 to 1.5 dl /
The method for producing a diffraction grating according to claim 1, wherein a hydrogenated polymer having a g (30 ° C in chloroform) is injection-molded or compression-molded.

[0005]

[Chemical 2]

(In the formula, A, B, C and D are hydrogen atoms.
Alternatively, it represents a monovalent organic group. ) Hydrogenation used in the present invention
The polymer (hereinafter also referred to as "thermoplastic resin")
It has a norbornane skeleton in the return unit.
Containing a norbornane skeleton represented by the general formula (III)
Is.

[0007]

[Chemical 3]

(In the formula, A, B, C and D represent a hydrogen atom or a monovalent organic group.) The thermoplastic resin having a norbornane skeleton used in the present invention is required to have sufficient strength. , Its weight average molecular weight is 5,000 to 100
10,000, preferably 8,000 to 200,000.

Examples of the thermoplastic resin having a norbornane skeleton which can be used in the present invention include, for example, JP-A-60-168708 and JP-A-62-2524.
No. 06, No. 62-252407, No. 2-133413, No. 63-145324, No. 63-264626, and No. 1-2.
Resins described in JP-B No. 40517, JP-B No. 57-8815 and the like can be mentioned. As a specific example of this thermoplastic resin, at least one tetracyclododecene derivative represented by the general formula (V) or the tetracyclododecene derivative and an unsaturated cyclic compound copolymerizable therewith can be metathesized. The hydrogenated polymer obtained by hydrogenating the polymer obtained by superposition | polymerization can be mentioned.

In the tetracyclododecene derivative represented by the general formula (V), it is preferable that A, B, C and D contain a polar group in terms of adhesion and heat resistance. Further, the polar group is — (CH ₂ ) _n COOR ¹ (wherein R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, and n is 0 to 1).
A group represented by (indicating an integer of 0) is preferable since the obtained hydrogenated polymer has a high glass transition temperature. In particular, when ^one polar substituent represented by — (CH ₂ ) _n COOR ¹ is contained per molecule of the tetracyclododecene derivative of the general formula (V), the water absorption is lowered. Is preferred. In the general formula,
R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, and it is preferable that the hydrogen absorption property of the obtained hydrogenated polymer becomes smaller as the carbon number increases, but R ¹ has a glass transition temperature of the obtained hydrogenated polymer. From the viewpoint of balance, a chain alkyl group having 1 to 4 carbon atoms or a (poly) cyclic alkyl group having 5 or more carbon atoms is preferable, and a methyl group, an ethyl group and a cyclohexyl group are particularly preferable.

Further, tetra-carbon of the general formula (V) in which a hydrocarbon group having 1 to 10 carbon atoms is simultaneously bonded as a substituent to the carbon atom to which the group represented by-(CH ₂ ) _n COOR ¹ is bonded Cyclododecene derivatives are preferable because they lower hygroscopicity. In particular, the tetracyclododecene derivative represented by the general formula (V) in which the substituent is a methyl group or an ethyl group is preferable because the synthesis thereof is easy. Specifically, 8-
Methyl-8-methoxycarbonyltetracyclo [4.
4.0.1 ^2,5 . 1 ^7,10 ] dodeca- 3 -ene is preferred. These tetracyclododecene derivatives or a mixture of unsaturated cyclic compounds copolymerizable therewith are described, for example, in JP-A-4-77520, page 4, upper right column, line 12 to page 6, lower right column, line 6; By the method described, the thermoplastic resin used in the present invention can be obtained by metathesis polymerization and hydrogenation.

In the present invention, the thermoplastic resin having a norbornane skeleton has an intrinsic viscosity (η _inh ) measured at 30 ° C. in chloroform of 0.2 to 1.5 dl / g, preferably 0.3 to 1 It is 0.0 dl / g. Intrinsic viscosity (η
_inh ) of less than 0.2 dl / g, the mechanical properties are poor,
When the impact resistance is lowered, on the other hand, when it exceeds 1.5 dl / g, the workability is poor and the injection moldability is poor. The hydrogenation rate of the hydrogenated polymer is 50% or higher, preferably 90% or higher, more preferably 98% or higher, as measured by ¹ H-NMR at 60 MHz. The higher the hydrogenation rate, the more stable the diffraction grating against heat and light can be obtained. The hydrogenated polymer used as the thermoplastic resin having a norbornane skeleton of the present invention has a gel content of 5 in terms of preventing the occurrence of defects such as silver streaks in diffraction grating molding. It is preferably not more than 1% by weight, particularly preferably not more than 1% by weight.

The thermoplastic resin having a norbornane skeleton used in the present invention is, for example, benzotriazole-based, benzophenone-based, salicylic acid-based, cyanoacrylate-based, etc. in order to improve its weather resistance and light resistance as required. In addition to the above UV absorbers, hindered amine-based, nickel complex salt-based, benzoate-based, and other UV stabilizers can be added. Further, it is also possible to add so-called additives such as an antioxidant, an anti-yellowing agent, an internal release agent, an antistatic agent and a leveling agent. As a method for adding these additives, these additives may be dissolved and dissolved in a solution before pelletization in the polymer production process, or may be dissolved with a ribbon blender, a tumbler blender, a Henschel mixer, etc. These additives may be mixed with pelletized or powdered or crumb-shaped resin, or they may be added while the resin is melted using a single-screw or multi-screw extruder, kneader, bandry mixer, or roll. The agent may be kneaded. The diffraction grating of the present invention can be molded by injection molding or compression molding of a thermoplastic resin having a norbornane skeleton.

The diffraction grating of the present invention has 0.1 to 0.1% on its surface.
Although it has parallel linear irregularities at intervals of 1000 μm, preferably 0.4 to 100 μm, the irregularities have linear irregularities formed on the surface of the mold at desired intervals. Can be formed by transferring to the surface of a thermoplastic resin having a norbornane skeleton during molding. The depth of the unevenness is usually 0.01 to 10 μm.
m, preferably 0.1 to 1 μm. In the present invention, as a method for forming a predetermined unevenness on the mold surface, a smooth mirror-finished surface is scratched with a sharp blade-like object, a photoresist is applied, and a diffraction pattern is obtained by electron beam or radiation. baked, path the photoresist
A method of forming irregularities on the metal surface by dry etching using plasma or the like, or chemical etching using a chemical after removing according to the turns is mentioned.

In the present invention, the resin temperature at the time of injection molding or compression molding is usually 230 to 360 ° C., preferably 2
It is 60 to 340 ° C. When the resin temperature is low, the fluidity is deteriorated, the molded product is distorted, and when the temperature exceeds 360 ° C., the resin is decomposed to cause silver streak, colored in yellow, or defective transfer of the diffraction grating pattern is likely to occur. The mold heating temperature during compression molding is usually 0 to 360.
C., preferably 160 to 340.degree. C., and the temperature during cooling is -40 to 200.degree. C., preferably 0 to 150.degree.
In injection molding, the mold temperature is generally set at a temperature lower than the glass transition temperature of the thermoplastic resin used. In order to reduce the strain of the obtained flat plate, it is preferable to set the temperature close to the glass transition temperature, but it requires a cooling time, the cycle time becomes long, and peeling occurs. When the mold temperature is set to a low temperature, the strain becomes large, but the cycle time becomes short. Therefore, the preferable mold temperature is 10 ° C. to 80 ° C. lower than the glass transition temperature of the resin, and more preferably 20 ° C. to 60 ° C. lower. Further, the resin temperature is formed as the residence time in the cylinder is reduced below 60 minutes because it is very high temperatures
It is preferable to set the shape machine or cycle time.

The diffraction grating of the present invention can be applied to a small size of 5 mm square or less to a large size of 60 cm square or more. The surface accuracy of the diffraction grating of the present invention depends on the surface accuracy of the mold and is determined according to the requirements of each application. Usually, for optical applications, those having irregularities of 10 μm or less are generally used. The thickness of the diffraction grating of the present invention is determined by product strength, workability during product assembly, and product design. In particular, in the case of A4 size or more, the thickness is 10 μm or more, preferably 0.05 to 5 mm, in order to suppress the deflection that is likely to cause the deflection with a practical quality. Specific applications of the diffraction grating of the present invention include a diffraction grating used in a laser optical system for an optical disk and a wavelength used when a double wavelength light is made by using a non-linear optical element to separate a fundamental wavelength from a fundamental wave. It can be suitably used for a diffraction grating for fractionation.
As an example of use in a laser optical system for optical disks, MD
For example, it can be used as a beam splitter that generates a tracking beam in a certain angle direction from the main beam.

[0017]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. In the examples, parts and% are based on weight unless otherwise specified. The various measurements in the examples are as follows. Intrinsic viscosity (η _inh ) Chloroform was used as a solvent, and the polymer concentration was measured with an Ubbelohde viscometer at a polymer concentration of 0.5 g / dl at 30 ° C. Hydrogenation rate In the case of a hydrogenated homopolymer, supersilipt H-NMR was measured at 60 MHz. Glass transition temperature Measured by a scanning calorimeter (DSC) in a nitrogen atmosphere at a temperature rising rate of 10 ° C./min.

Reference Example 1 8-Methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodeca-3-en 10
2. 0 g, 1,2-dimethoxyethane 60 g, cyclohexane 240 g, 1-hexene 9 g, and a solution of diethylaluminum chloride 0.96 mol / l in toluene 3.
4 ml was added to an autoclave having an internal volume of 1 liter. On the other hand, in another flask, a solution of tungsten hexachloride (0.1%) was added.
20 ml of a 05 mol / l 1,2-dimethoxyethane solution
And 10 ml of a 0.1 mol / l 1,2-dimethoxyethane solution of paraaldehyde were mixed. This mixed solution 4.9
ml was added to the mixture in the autoclave. After sealing, the mixture was heated to 80 ° C. and stirred for 2.5 hours. To the obtained polymer solution, a mixed solvent of 1/8 (weight ratio) of 1,2-dimethoxyethane and cyclohexane was added to make the polymer / solvent 1/10 (weight ratio), and then triethanolamine 20 g Was added and stirred for 10 minutes. To this polymerization solution, 500 g of methanol was added, stirred for 30 minutes and allowed to stand. The upper layer separated into two layers was removed, methanol was added again, and the mixture was stirred and allowed to stand, and then the upper layer was removed. The same operation was repeated twice, and the resulting lower layer was mixed with cyclohexane,
By appropriately diluting with 1,2-dimethoxyethane, a cyclohexane-1,2-dimethoxyethane solution having a polymer concentration of 10% was obtained. 20 g of palladium / silica magnesia [manufactured by JGC Chemical Co., Ltd., palladium amount = 5%] was added to this solution, and the mixture was reacted in an autoclave at a hydrogen pressure of 40 kg / cm ² at 165 ° C. for 4 hours, and then hydrogenated catalyst. Was removed by filtration to obtain a hydrogenated polymer solution. Further, to this hydrogenated polymer solution, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], which is an antioxidant, was added to the hydrogenated polymer. After adding 0.1%, the solvent was removed at 280 ° C. under reduced pressure. Then, the molten resin was pelletized by an extruder under a nitrogen atmosphere to give an intrinsic viscosity of 0.48 dl.
/ G (30 ° C, in chloroform), hydrogenation rate 99.5%,
A thermoplastic resin A having a glass transition temperature of 168 ° C. was obtained.

Example 1 Using the thermoplastic resin A obtained in Reference Example 1, a mold having a mirror finish was attached to a commercially available injection molding machine, and a resin temperature of 320
℃, mold temperature 130 ℃, cooling time 20 seconds, 10 cm ×
A diffraction grating having a size of 10 cm and a thickness of 1 mm was molded. Here, 100 parallel straight lines were previously formed on the surface of the mold by scribing with a gap of 6.23 μm and a depth of 0.5 μm.
The molded product after molding was taken out from the mold with a pin, and two projections were provided at the end of the flat plate. No scratches due to silver streaks or peeling were found on the obtained diffraction grating. The light transmittance of the mirror surface of the obtained diffraction grating is 92%, and the variation in thickness is 1
%, The birefringence is 20 nm for both normal incidence and gradual incidence.
The following is a small one, and the unevenness is 10 μm or less,
It was at a level that was possible for optical applications. Further, when a laser beam of 623 nm was vertically incident on the diffraction grating portion at the center of the diffraction grating, the emitted light was about 10 m at 1 m.
Since spots up to the 5th order were clearly observed at cm intervals, it was confirmed that the spots functioned as a diffraction grating.

Comparative Example 1 A diffraction grating was formed in the same manner as in Example 1 except that polycarbonate (L1225 manufactured by Teijin Kasei) was used in place of the thermoplastic resin A obtained in Reference Example 1. The light transmittance of the mirror surface portion of the obtained diffraction grating is 87%, the thickness variation is 1.5%, and the birefringence is 100 nm at normal incidence and 300 nm at 45 ° oblique incidence, which is unsuitable for optical applications. It was In addition, 62 in the center of the diffraction grating
When a 3 nm laser beam is incident, the emitted light is 1 m
However, the spots up to the second order were blurred at intervals of about 10 cm, the transfer of the diffraction grating pattern of the mold was poor, and it did not function sufficiently as a diffraction grating.

Reference Example 2 8-Ethyl-tetracyclo [4.4.0.1 ^2,5 . 1
^7,10 ] Dodeca-3-ene 100 g, 1,2-dimethoxyethane 60 g, cyclohexane 240 g, 1-hexene 9 g, and diethylaluminum chloride 0.96.
3.4 ml of a mol / l toluene solution was added to an autoclave having an internal volume of 1 liter. On the other hand, in another flask,
20 ml of a 0.05 mol / l 1,2-dimethoxyethane solution of tungsten hexachloride and 10 ml of a 0.1 mol / l 1,2-dimethoxyethane solution of paraaldehyde were mixed. 4.9 ml of this mixed solution was added to the mixture in the autoclave. After sealing, the mixture was heated to 80 ° C. and stirred for 2.5 hours. In the obtained polymer solution,
2/8 of 1,2-dimethoxyethane and cyclohexane
(Weight ratio) mixed solvent was added to give a polymer / solvent ratio of 1/10.
After adjusting to (weight ratio), 20 g of triethanolamine was added and stirred for 10 minutes. To this polymerization solution, 500 g of methanol was added, stirred for 30 minutes and allowed to stand. The upper layer separated into two layers was removed, methanol was added again, and the mixture was stirred and allowed to stand, and then the upper layer was removed. The same operation was repeated twice, and the obtained lower layer was appropriately diluted with cyclohexane and 1,2-dimethoxyethane to prepare a cyclohexane-containing polymer having a concentration of 10%.
A 1,2-dimethoxyethane solution was obtained. 20 in this solution
g of palladium / silica magnesia [JGC Corporation
Manufactured, palladium amount = 5%] was added, and the mixture was reacted in an autoclave at a hydrogen pressure of 40 kg / cm ² at 165 ° C. for 4 hours, and then the hydrogenation catalyst was removed by filtration to obtain a hydrogenated polymer solution. Moreover, pentaerythrityl-tetrakis [3-] which is an antioxidant is added to the hydrogenated polymer solution.
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] was added to the hydrogenated polymer in an amount of 0.1%, and then the solvent was removed at 280 ° C. under reduced pressure. Then
The molten resin was pelletized by an extruder under a nitrogen atmosphere, and the intrinsic viscosity was 0.48 dl / g (30 ° C. in chloroform), the hydrogenation rate was 99.5%, the glass transition temperature was 13
A thermoplastic resin B having a temperature of 8 ° C. was obtained.

Example 2 Using the thermoplastic resin B obtained in Reference Example 2, a mold for mirror finishing was attached to a commercially available injection molding machine, and a resin temperature of 290
℃, mold temperature 100 ℃, cooling time 20 seconds, 10 cm ×
A diffraction grating having a size of 10 cm and a thickness of 1 mm was molded. Here, 100 parallel straight lines were previously formed on the surface of the mold by scribing with an interval of 3.12 μm and a depth of 0.3 μm.
The molded product after molding was taken out from the mold with a pin, and two projections were provided at the end of the flat plate. An aluminum reflective film was vapor-deposited on the surface of the obtained molded product, and a protective coat was attached on the film to form a diffraction grating in which light entered and exited from the resin side. No scratches due to silver streak or peeling were observed. Further, the light reflectance of the mirror surface portion of the obtained diffraction grating is 92%, the variation in thickness is less than 1%,
The birefringence was as small as 20 nm or less in both normal incidence and gradual incidence, and the unevenness was 10 μm or less, which was a level possible for optical use. Furthermore, when a laser beam of 623 nm was perpendicularly incident on the center of the diffraction grating, spots up to the 5th order were clearly observed at an interval of about 20 cm at a distance of 1 m from the emitted light. I confirmed that.

[0023]

The diffraction grating made of the thermoplastic resin having the norbornane skeleton of the present invention is molded by injection molding or compression molding, so that the unevenness corresponding to the surface accuracy of the mold is satisfactorily transferred and there is no coloring. It has an excellent function as a diffraction grating. Further, the shape of the molded product can be changed by the mold, and it is not necessary to cut and match the shape after molding, and it is also possible to simultaneously form a projection for hole making and a stopper metal by molding.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-43302 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 5/18

Claims (3)

(57) [Claims] 1. A polymer obtained by metathesis polymerization of at least one tetracyclododecene derivative represented by the following formula (V) or the tetracyclododecene derivative and an unsaturated cyclic compound copolymerizable therewith. It is composed of a hydrogenated polymer obtained by hydrogenating the coalesced product, and has a surface of 0.1 to 100
A diffraction grating having parallel linear irregularities at intervals of 0 μm. [Chemical 1] (In the formula, A, B, C and D represent a hydrogen atom or a monovalent organic group.) 2. The intrinsic viscosity (η _inh ) is 0.2 to 1.5 d.
The hydrogenated polymer of 1 / g (in chloroform, 30 ° C.) is injection-molded or compression-molded.
Manufacturing method of the diffraction grating of. 3. A metal or metal oxide thin film having a metallic luster having a light reflectance of 50% or more is vapor-deposited on the surface.
Diffraction grating.