JPH08292307A - Polarizing prism and its production - Google Patents

Abstract

PURPOSE: To obviate the total reflection in spite of diagonal light at the joint surfaces of plural prisms consisting of double refractive optical crystals having a high refractive index by interposing an adhesive having a high refractive index consisting of a polyimide resin or bromophenyl compd. between the joint surfaces of the prisms. CONSTITUTION: This polarizing prism is formed by joining the plural prisms 1, 2 consisting of the double refractive optical crystals by the adhesive. The adhesive of the polarizing prism having a relation of n1 sinθ>=1.7 when the max. incident angle to be utilized among the incident angle distributions of rays on the joint surfaces is defined as θ and the refractive index of the prism on the incident side as n1 is composed of the polyimide resin or bromophenyl compd. The polyimide resin of such high-refractive index joint layer 5 is high in refractive index and, therefore, even the light from diagonal is not totally reflected. The total reflection does not arise at the joint surfaces of exit surface of LN, the reflection of several % by the refractive index difference arises and, therefore, the prevention of the loss of energy by providing the polarizing prism with antireflection layers 4, 6 is effective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing prism having a plurality of prisms made of a birefringent optical crystal cemented together and a method for manufacturing the same.

[0002]

2. Description of the Related Art Plural prisms made of birefringent optical crystals
Polarizing prisms obtained by joining two frames, such as Wollast
The prisms and lotion prisms are
Used together, they are used as polarizing optical elements. one
Generally, it is disclosed in JP-A-5-181016.
As described above, artificial quartz is used as the birefringent optical crystal.
And are joined by an adhesive. In this case,
Use of low-viscosity UV-curable adhesive due to its goodness
There are many. In addition, as a means of joining, a mirror surface with high flatness
It is called an optical contact that vacuum-adheres each other.
The method is also used. On the other hand, as a birefringent optical crystal
In recent years, LiNb₃(LN), LiTaO ₃(LT)
Or TiO₂(Rutile) has a higher refractive index than artificial quartz
Is considered promising because of its high price.

[0003]

By the way, in the case of synthetic quartz, the refractive index is almost equal to the refractive index (synthetic quartz: 1.
46, adhesive: 1.4 to 1.6), so there is almost no reflection at the interface, and even if the refractive index of the adhesive is slightly different from that of the synthetic quartz, anti-reflection on the joint surface of the synthetic quartz is prevented. Reflection can be reduced by coating the film. However, LN, LT or rutile has a refractive index of 2.0.
For the above reasons, the refractive index is significantly different from that of the adhesive that is normally used, and the reflection at the interface cannot be ignored.

In such a case, even if the reflection of the vertically incident light is prevented by using the antireflection film, the reflection of the obliquely incident light cannot be prevented and the light is totally reflected. In order to prevent total reflection, it is necessary to deviate from the Snell total reflection condition. If the incident angle to the cemented surface is θ, the refractive index of the prism on the incident side is n ₁ , and the refractive index of the adhesive is n ₂ , It is necessary not to satisfy the relationship of n ₁ sin θ ≧ n ₂ . For example, a prism having a refractive index of 2.0 requires an adhesive having a refractive index of 1.7 or more when the incident angle is 58.2 °. However, it is difficult to obtain such a refractive index with an ordinary adhesive, and even the one sold as a high refractive index adhesive has a refractive index of about 1.58, and a high refractive index that is actively developed as an eyeglass lens. 1.66 even for organic optical materials
(Made by Asahi Glass Co., Ltd.) That is, n ₁ sin θ ≧
There is a problem in that it is extremely difficult to manufacture a polarizing prism having a size of 1.7.

In addition, in the prism bonding by optical contact, the bonding interval is extremely small and no reflection occurs at the interface, but the bonding strength is low, and there is a problem that peeling easily occurs due to temperature change and moisture. further,
The work environment requires extremely high degree of cleanliness, the outer diameter cannot be corrected by the bonding layer, and the precision of the prism itself must be maximized to produce a highly accurate polarizing prism. there were.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a joint surface of a plurality of prisms made of a birefringent optical crystal having a high refractive index, which is oblique. It is to provide a polarizing prism that does not totally reflect even the above light. An object of the invention according to claim 2 or 3 is to provide a manufacturing method capable of stably manufacturing the polarizing prism of the invention according to claim 1.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is such that a plurality of prisms made of a birefringent optical crystal are bonded to each other with an adhesive, and a light beam to a bonding surface is formed. the maximum incident angle for use of the incident angle distribution of theta, when the refractive index of the incident side of the prism and the n _1, n ₁
In a polarizing prism having a relationship of sin θ ≧ 1.7,
The adhesive is made of a polyimide resin or a bromophenyl compound.

According to a second aspect of the present invention, in the method of manufacturing a polarizing prism, a step of bringing the joint surfaces of a plurality of prisms made of a birefringent optical crystal into contact with each other to hold the prisms in a predetermined positional relationship, and the contact. The step of supplying the pre-curing solution of the energy-curable polyimide between the bonding surfaces that are doing, after removing the solvent of the pre-curing solution of the energy-curable polyimide at a low temperature, the temperature is raised to prepolymerize, and at a higher temperature. It is characterized by including the imidation-ized polyimidization process. According to a third aspect of the invention, in the method for manufacturing a polarizing prism, a film of a polyimide resin or a bromophenyl compound is sandwiched between the joint surfaces of a plurality of prisms made of a birefringent optical crystal, or a solvent diluted solution thereof is used. The method is characterized by including a step of applying and semi-curing, a step of holding the prism in a predetermined positional relationship, and a step of gradually heating and heating to a predetermined temperature while maintaining the positional relationship.

[0009]

In the operation of the invention according to claim 1, since a high refractive index adhesive made of a polyimide resin or a bromophenyl compound is interposed between the bonding surfaces of the prism, it is composed of a high refractive index birefringent optical crystal. With the joint surface of multiple prisms,
Even light from an angle does not totally reflect. The refractive index of the adhesive used for joining is 1.7 or more, preferably 1.
8 or more. Polyimide (PI) is composed of a benzene ring, nitrogen (N), oxygen (O) and carbon (C), and has a very high refractive index as an organic substance due to the benzene ring and imide structure. The bromophenyl compound has a basic structure in which the benzene ring is brominated (Br), and satisfies the above refractive index due to the refractive index improving action of the benzene ring and bromine.

According to the second aspect of the present invention, the step of supplying the pre-curing solution of the energy-curable polyimide between the contact surfaces of the prisms in contact with each other, and the pre-curing solution of the energy-curable polyimide as a solvent at a low temperature. After the removal, the temperature was raised to a prepolymer, and a polyimidization step of imidization at a higher temperature was included.
The liquefied energy-curable polyimide pre-curing solution easily penetrates into the joint surface, and then the solvent and the reaction products, water and alcohol, are completely removed by heating in three steps to achieve stable polymerization. Be seen. Claim 3
In the action of the invention according to, the step of sandwiching a film of a polyimide resin or a bromophenyl compound between the bonding surfaces of the prism, or applying a solvent diluting solution thereof to semi-cure, and setting the prism in a predetermined positional relationship. Since it includes the step of holding and the step of heating to a predetermined temperature and gradually cooling while maintaining the positional relationship, at the time of bonding, it becomes a viscous adhesive and is fixed on the bonding surface, Stable polymerization is performed by heating.

[0011]

EXAMPLES In the following examples, a prism using LN as a birefringent optical crystal will be described as a typical example, but similar effects can be obtained by substituting LT or rutile. However, it is necessary to slightly change the configurations of the polarizing film and the antireflection film.

[0012]

Embodiment 1 FIGS. 1 and 2 show Embodiment 1, FIG. 1 is a longitudinal sectional view of a polarizing prism, and FIG. 2 is an explanatory view showing a method of manufacturing the polarizing prism. In FIG. 1, reference numerals 1 and 2 are prisms made of LN, a polarizing film 3 on the surface 1a, an antireflection film 4 on the surfaces 1b and 2a, and an antireflection film 6 on the surface 2b.
They are formed by vacuum vapor deposition with the configurations shown in Table 1, Table 2 and Table 3 below.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

A high refractive index bonding layer 5 is a polyamic acid-based polyimide resin molding material "Vespel" (refractive index 1.7.
8: manufactured by Dupont).

A method of manufacturing the polarizing prism will be described with reference to FIG. First, the positioning jig 10 used in this manufacturing method will be described. The positioning jig 10 constitutes a mounting portion 10A with a spacer 11 for determining the thickness of the polarizing prism and two flat plates 12 sandwiching the spacer 11 therebetween. Further, the pressing portion 10B of the positioning jig 10 is configured by inserting the spring 15 and the pressing pin 14 into the cylindrical member 13 and fixing it to the sliding member 16 which slides in the direction of arrow X.

First, the prisms 1 and 2 on which the films shown in Tables 1 to 3 are formed are inserted into the mounting portion 10A of the positioning jig 10, and the tilt, shift and optical axis direction of the outer shape are adjusted to a predetermined accuracy. To do. After that, the pressing portion 10B is moved forward to press and fix the prisms 1 and 2. Next, the above-mentioned “vespel” is permeated through the joints 7 on the side surfaces of the prisms 1 and 2, and 80
The temperature is slowly raised to 0 ° C. and the temperature is maintained for 1 hour to remove the solvent. Further, the temperature is slowly raised to 250 ° C. and kept for 1 hour for prepolymerization, then the temperature is slowly raised to 300 ° C. and kept for 1 hour to imidize and then gradually cooled.
As a result, the high refractive index bonding layer 5 is formed, and the prism 1,
The two are joined to obtain a polarizing prism.

In the high-refractive-index bonding layer of this embodiment, since the polyimide resin has a high refractive index, it does not undergo total reflection even when light is oblique. In addition, at the joining surface and the emitting surface of the LN,
Although total reflection does not occur, reflection of several% occurs due to the difference in refractive index, so it is effective to provide an antireflection film to prevent energy loss.

Further, in this embodiment, since the heating process is divided into three steps, it is possible to prevent the generation of voids when the polyimide is cured. In the present embodiment, since it is a single polyimide and a single solvent, heating in three stages is sufficient.
When a plurality of polyimides are blended or diluted with a plurality of solvents, it is effective to increase the number of stages according to the respective curing temperatures and boiling points.

According to this embodiment, it is possible to obtain a polarizing prism in which total reflection of incident light by the high refractive index bonding layer does not occur, and deterioration or performance change due to environmental changes does not occur. Further, according to the manufacturing method of this embodiment, a highly accurate polarizing prism can be stably obtained.

[0022]

Second Embodiment The structure of the second embodiment is almost the same as that of the first embodiment except that only the composition of the high refractive index bonding layer 5 is different. Since the same reference numerals are given to the members, the description of the same parts will be omitted.

In FIG. 1, the high refractive index bonding layer 5 is made of a polymer of biphenyltetracarboxylic acid (BPDA) polyimide resin (manufactured by Ube Industries, Ltd.). Other configurations are the same as those of the first embodiment.

Since the manufacturing method of the polarizing prism is almost the same as that of the first embodiment, the manufacturing process of the high refractive index bonding layer 5 will be mainly described. In FIG. 2, the processes until the prisms 1 and 2 are mounted on the positioning jig 10 are the same as those in the first embodiment. Next, a polyimide solution obtained by heat-polymerizing a mixture of BPDA and aromatic diamine (DADE) is allowed to permeate through the joints 7 on the side surfaces of the prisms 1 and 2, and the temperature is slowly raised to 80 ° C. and kept for 1 hour. Volatilize the solvent. Next, +3
The temperature is slowly raised to 250 ° C. at a rate of ° C./min, the temperature is maintained for 1 hour, and then gradually cooled to prepolymerize. Further, the prisms 1 and 2 are removed from the positioning jig 10, the temperature is raised to 450 ° C. at a rate of + 5 ° C./min, imidized, and then gradually cooled.
As a result, the high refractive index bonding layer 5 is formed, and the prism 1,
The two are completely joined to obtain a polarizing prism.

According to this embodiment, in addition to the effects of the first embodiment, the polyimide used in this embodiment does not generate water during polymerization as compared with a general polyamic acid type, so that a uniform bonding layer is formed. Obtainable. Further, this type of polyimide is also characterized by having a small coefficient of linear expansion, and is excellent in durability. Further, since the final imidization step needs to be performed at an extremely high temperature, the linear expansion coefficient of the positioning jig and the prism cannot be ignored, but the effect of the jig can be eliminated by dividing the steps.

[0026]

Third Embodiment In the structure of the third embodiment, the structure of the polarizing prism is almost the same as that of the first embodiment. The difference is only the composition of the high refractive index bonding layer, which will be described with reference to FIG. Since the same reference numerals are given to the members, the description of the same parts will be omitted. The manufacturing method of the polarizing prism is different from that of the first embodiment, and therefore will be described with reference to FIG.

In FIG. 1, the high refractive index bonding layer 5 is a bonding layer made of a thermoplastic polyimide resin, and more specifically, a benzophenonetetracarboxylic acid type polyimide "P".
I-2080 "(manufactured by Upjohn).
Other configurations are the same as those in the first embodiment.

FIG. 3 shows a method of manufacturing the polarizing prism of this embodiment. Since the positioning jig 10 used in this manufacturing method is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted. First, between the prisms 1 and 2,
Polyimide film 5 made of the above "PI-2080"
A is sandwiched and mounted on the positioning jig 10, and the prisms 1, 2 are attached.
The tilt, shift, and optical axis direction of the outer shape between them are combined with a predetermined accuracy and pressure is maintained. Next, the polyimide film 5A is slowly heated to a temperature not lower than the glass transition point (310 ° C.) and then gradually cooled. As the heating temperature,
350 ° C due to the adhesion between LN and polyimide film 5A
The above is more preferable, and 500 ° C. or less is preferable from the viewpoint of heat resistance. As a result, the high refractive index bonding layer 5 having a refractive index of 1.7 or more is formed, the prisms 1 and 2 are completely bonded, and a polarizing prism is obtained.

According to this example, in addition to the effects of Example 1, the polyimide film does not undergo a reaction such as polymerization at the time of bonding, so that it can be bonded in a short time. In addition, since the glass transition temperature is high and the glass does not melt even when heated, the protrusion is minimized and the prism has excellent heat resistance.

In this embodiment, "PI-2080" was used as the polyimide film, but a similar material such as L-2020 was used.
ARC-TPI (manufactured by Mitsui Toatsu), Kapton (Dupo
nt company) and Upilex (manufactured by Ube Industries, Ltd.) and the like, and similar effects can be obtained by using these.

[0031]

Example 4 The structure of Example 4 is almost the same as that of Example 3 except for the composition of the high-refractive-index bonding layer 5, which is the same as that of Example 3. Since the same reference numerals are given to the members, the description of the same parts will be omitted.

In FIG. 1, the high refractive index bonding layer 5 is a bonding layer made of a special aromatic polyamide resin represented by the chemical formula of "Chemical formula 1" below. Since this polyamide has a brominated (brominated) benzene ring (phenyl) in its basic structure, it has an extremely high refractive index of 1.89. Other configurations are the same as those in the first embodiment.

[0033]

Embedded image

FIG. 3 shows a method of manufacturing the polarizing prism of this embodiment. Since the positioning jig 10 used in this manufacturing method is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted. First, between the prisms 1 and 2,
The polyamide film 5B made of the special aromatic polyamide resin of the above “Chemical formula 1” is sandwiched and mounted on the positioning jig 10, and the tilt, shift and optical axis direction of the outer shape between the prisms 1 and 2 are combined with predetermined accuracy. Hold under pressure. Next, the temperature is gradually raised to a temperature not lower than the glass transition point of the polyamide film 5B and then gradually cooled. Thereby, the high refractive index bonding layer 5 having a refractive index of 1.89 is formed, the prisms 1 and 2 are completely bonded, and a polarizing prism is obtained.

According to this example, in addition to the effects of Example 1, the polyamide film made of the special aromatic polyamide resin of "Chemical formula 1" has a refractive index of 1.89 and LN
It is possible to prevent total reflection even when an optical crystal having a higher refractive index is used or when a design with a larger incident angle is required. Further, since the above polyamide film does not undergo a reaction such as polymerization upon joining, it is joined in a short time. Furthermore, since the glass transition temperature is high and it does not melt when heated, squeeze-out is minimized,
Excellent heat resistance as a prism.

[0036]

Fifth Embodiment In the structure of the fifth embodiment, the structure of the polarizing prism is almost the same as that of the first embodiment, and the difference is only the composition of the high refractive index bonding layer, which will be described with reference to FIG. Since the same reference numerals are given to the members, the description of the same parts will be omitted. The manufacturing method of the polarizing prism is different from that of the first to fourth embodiments, and therefore will be described with reference to FIG.

In FIG. 1, the high-refractive-index bonding layer 5 is composed of a polymer (refractive index: 1.78) of a solvent-diluted solution of polyamic acid-based polyimide resin molding material "Piraline" (manufactured by Dupont). Other configurations are the same as those of the first embodiment.
Is the same as

FIG. 3 shows a method of manufacturing the polarizing prism of this embodiment. Since the positioning jig 10 used in this manufacturing method is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted. First, the bonding surface 1b of the prism 1
The above “Pyralin” is applied to the above, and the temperature is raised to 200 ° C. in the air at a rate of about + 5 ° C./min to semi-cure while removing the solvent and water generated by the polymerization, and then gradually rising to room temperature. Cool. Next, overlap prisms 1 and 2,
It is mounted on the positioning jig 10, and the outer shape tilt, the shift, and the optical axis direction are combined with a predetermined accuracy to be held under pressure.
As it is, the temperature is slowly raised to 350 ° C. at about + 5 ° C./min, and the temperature is maintained for 1 hour to imidize. As a result, the high refractive index bonding layer 5 having a refractive index of 1.78 is formed, and the prism 1,
The two are completely joined to obtain a polarizing prism.

According to the present embodiment, in addition to the effects of the first embodiment, in the joining method of the present embodiment, the solvent can be removed and the water generated by the reaction can be efficiently removed. Is less likely to occur, and a uniform and good quality bonding layer can be obtained.

[0040]

[Embodiment 6] FIGS. 4 to 6 show the present embodiment, and FIG.
The top view which mounted the polarization prism on the board | substrate. FIG. 5 is a perspective view in which a groove is provided in the upper surface of the Si substrate, and FIG. 6 is a front view showing a modified example. The polarization prism part of the present embodiment is the same as the polarization prism of the fifth embodiment, so the description of the structure of the polarization prism will be omitted, but since it is mounted on the Si substrate,
The manufacturing method will be described.

As shown in FIGS. 4 and 5, a Si substrate 9 having a (1,1,0) surface is provided with a (1,1,1) surface as a side surface by crystal anisotropic etching. Groove 8
It is formed with a predetermined size. Next, the prisms 1 and 2 are attached to the groove 8
The surfaces 8A and 8B are applied and held. Further, the “pyralin” is permeated from the joint portion 7 on the side surface of the prisms 1 and 2. At this time, "pyralin" may be permeated also between the prisms 1 and 2 and the bottom surface of the groove 8. In this state, the temperature is slowly raised to 400 ° C., held for 1 hour to cure, and then gradually cooled to room temperature. This gives a refractive index of 1.7.
The high-refractive-index bonding layer 5 of No. 8 was formed, the prisms 1 and 2 were completely bonded, and a polarizing prism was obtained. "Pyralin" was also permeated between the prisms 1 and 2 and the bottom surface of the groove 8. In this case, a mounting substrate in which a polarizing prism is mounted on a Si substrate can be obtained.

According to the present embodiment, in addition to the effect of the first embodiment, the distance between the surface 1a of the prism 1 and the surface 2b of the prism 2 and the parallelism of the groove 8 formed by anisotropic etching with respect to the Si substrate. Since it is regulated on the (1, 1, 1) side,
A polarizing prism with high dimensional accuracy can be manufactured. Also, when "Pyralin" is infiltrated into the bottom surface of the prism and the groove, it is possible to bond the prism and the Si substrate at the same time. Therefore, this Si substrate can be used as a mounting substrate for a light receiving element or a laser diode. Can be used.

The manner of placing the prism on the Si substrate is not limited to the orientation of this embodiment, and the same operational effect can be obtained by the arrangement shown in FIG. 6, for example.

In addition to the polyimide resin or the bromophenyl compound specifically shown in the respective examples of the present invention, there are useful ones. In the case of a polymide resin, a polyimide bonding layer can be obtained by bonding with a liquid prepared by dissolving a polyamic acid precursor as a starting material thereof in a suitable solvent and then imidizing it by a cyclization reaction.
Further, the BPDA type polyimide can be obtained directly from a polyimide solution. An example of this is U
There is PILEX (manufactured by Ube Industries). Further, the nadic modified polyimide is characterized in that a high quality polyimide can be obtained at low temperature, which is called in-situ polymerization type, and is useful in the present invention. As an example, PMR-15 (NAS
A) and LARC-150 (manufactured by Mitsui Toatsu).

The bromophenyl compound can be bonded by polymerizing it using an appropriate starting material or selecting a compound exhibiting thermoplasticity. An example is pentabromophenyl acrylate (refractive index: 1.71).

[0046]

According to the first aspect of the invention, since the high refractive index substance is used for the bonding layer of the prism using the high refractive index birefringent optical crystal, total reflection of incident light by the bonding layer is performed. It is possible to obtain a polarizing prism that does not cause
According to the invention of claim 2, the polarizing prism of the invention of claim 1 can be stably manufactured. Moreover, since the heating process is performed in three stages, a high-quality polarizing prism without voids in the bonding layer can be obtained. According to the invention of claim 3, the polarizing prism of the invention of claim 1 can be stably manufactured. Also, since the process is simple, it is possible to join in a short time.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a polarizing prism of Examples 1-5.

FIG. 2 is an explanatory diagram showing a method of manufacturing the polarizing prism of Examples 1 and 2.

FIG. 3 is an explanatory diagram showing a method of manufacturing a polarizing prism of Examples 3 to 5.

FIG. 4 is a plan view of a polarization prism mounted on a Si substrate of Example 6.

FIG. 5 is a perspective view in which a groove is provided in the upper surface of a Si substrate of Example 6;

FIG. 6 is a front view showing a modification of the sixth embodiment.

[Explanation of symbols]

 1 Prism 2 Prism 3 Polarizing Film 4 Antireflection Film 5 High Refractive Index Bonding Layer 6 Antireflection Film

Claims (3)

[Claims] 1. A plurality of prisms made of a birefringent optical crystal are bonded to each other with an adhesive, and the maximum incident angle used in the distribution of incident angles of light rays on the bonding surface is θ, and the refraction of the prism on the incident side is performed. When the ratio is n ₁ , n ₁ sin θ ≧ 1.
7. The polarizing prism having the relationship of 7, wherein the adhesive is made of a polyimide resin or a bromophenyl compound. 2. A step of bringing the joint surfaces of a plurality of prisms made of a birefringent optical crystal into contact with each other to hold the prisms in a predetermined positional relationship, and curing the energy-curable polyimide between the contact surfaces. A step of supplying a pre-solution and a step of removing the solvent of the pre-curing solution of the energy-curable polyimide at a low temperature, preliminarily heating to prepolymerize, and further imidizing at a high temperature. A method for manufacturing a polarizing prism. 3. A step of sandwiching a film of a polyimide resin or a bromophenyl compound or applying a solvent diluted solution thereof to semi-cure between the bonding surfaces of a plurality of prisms made of a birefringent optical crystal, A method of manufacturing a polarizing prism, comprising: a step of holding the prism in a predetermined positional relationship; and a step of heating to a predetermined temperature and gradually cooling while maintaining the positional relationship.