JPH05132768A - Double refraction sheet and its manufacture - Google Patents

Abstract

PURPOSE:To form a thin film of high density, high in a double refractive index and mechanical strength on a transparent substrate with tight adhesion, at the time of manufacturing a double refraction sheet by vapor-depositing a metallic oxide thin film on a transparent substrate by a plasma vapor depositing method, by radiating the material to be vapor-deposited at a specified angle to the substrate. CONSTITUTION:In a vacuum tank of a plasma vapor-depositing apparatus, a transparent substrate 1 in which an SiO2 undercoat film has been formed on the surface is arranged; then, the inside of the vacuum tank is evacuated; an active gas or an inert gas is introduced; and its state is regulated to a pressure-reduced one of <=9X10<-5>Torr. A vapor deposition source 3 constituted of specified metallic oxide is heated and evaporated, and the evaporated material is flied in a direction 4 at which the inclination theta to the surface of the substrate 1 will be regulated to 40 to 80 degrees, by which a film 2 of metallic oxide high in a double refractive index, density and mechanical strength can be formed on the surface of the transparent substrate 1 with tight adhesion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a birefringent plate and its manufacturing method.

[0002]

2. Description of the Related Art A birefringent plate is widely used in various optical systems as an optical element for converting between linearly polarized light and circularly polarized light and for converting azimuth of linearly polarized light. The birefringent plate is known to be thinly polished natural quartz or calcite, but these are expensive, so recently an artificial one is proposed in which a metal oxide film is obliquely deposited on the surface of a transparent substrate. Has been done.

A metal oxide film formed by oblique vapor deposition on the surface of a transparent substrate shows birefringence because the connection of vapor deposition particles varies depending on the direction. However, in the birefringent plate manufactured by this method, the density of the formed metal oxide film is not high enough,
Therefore, it is difficult to realize high birefringence. In addition, the adhesion of the formed metal oxide film to the transparent substrate and the strength of the film itself are not so strong, which causes a problem such as clouding on the birefringent plate or a process with poor mass productivity. There is also.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has high birefringence, loose restrictions on size, and arbitrary retardation, and high density. It is an object of the present invention to provide a novel birefringent plate that has a metal oxide film that has high adhesion to a transparent substrate, high mechanical strength, and excellent environmental resistance, and can be realized at low cost, and a manufacturing method thereof.

[0005]

The birefringent plate of the present invention comprises:
The metal oxide film is formed on the surface of the transparent substrate. The manufacturing method according to claim 1 is "40 to 80 relative to the surface of the transparent substrate."
The positional relationship between the transparent substrate surface and the evaporation source is set so that the evaporated material may fly from a tilted direction, and the pressure of the introduced gas may be set to 9
In the state of × 10 to ⁵ Torr or more, a thin film of a metal oxide is formed to a desired film thickness by a plasma vapor deposition method ”.

Since the flight direction of the evaporation material evaporated from the evaporation source is radial with the evaporation source as the center, the flight direction of the evaporation material with respect to the transparent substrate surface is not unique. Therefore, the phrase “evaporation material comes in from a direction inclined by 40 to 80 degrees with respect to the transparent substrate surface” means that the evaporation material comes in near the center of the transparent substrate surface in the absence of an electric field or magnetic field. Is inclined by 40 to 80 degrees with respect to the surface of the transparent substrate.

The "introduced gas" is an active gas and / or an inert gas. "Plasma deposition method" is closed
The vapor deposition method disclosed in Japanese Patent No. 53351 is carried out as follows. That is, the deposition target substrate is held by the counter electrode and is opposed to the evaporation source. A grid is provided between the evaporation source and the counter electrode, and an electric field is formed from the grid toward the counter electrode. In addition, a filament for thermionic emission is provided, and active gas and / or
Alternatively, an inert gas is introduced as the introduction gas.

At the time of vapor deposition, thermoelectrons are emitted from the filament, the introduced gas is ionized to generate plasma in the bell jar, and in this state, the evaporation material is evaporated from the evaporation source. The particles of the vaporized substance are ionized by collision with ions of the introduced gas and thermoelectrons, accelerated by the electric field formed between the grid and the counter electrode, and collide with the surface of the deposition target substrate at high speed to form a film. To do.

As described above, in the method for manufacturing a birefringent plate of the present invention, the range of the "tilt angle" of the surface of the transparent substrate with respect to the flying direction of the vaporized substance is set to 40 to 80 degrees.
A particularly preferable tilt angle for forming a thin film having high birefringence is about 70 degrees (claim 2). When the deposition area on the surface of the transparent substrate is relatively small, "the direction perpendicular to the plane including the normal line and the main flight line standing on the transparent substrate surface at the intersection of the main flight line of the evaporated substance and the transparent substrate surface is When the direction A is taken, the direction of the main flight line is taken as the reference flying direction of the evaporation material, and the evaporation source and the transparent substrate are relatively displaced in the direction A, and the metal oxide film is formed into a desired film by the plasma deposition method. It is desirable to form "thickness", and in this case, the "relative movement range of the evaporation source and the transparent substrate in the A direction" is preferably 30 degrees or less on both sides of the main flight line when viewed from the evaporation source ( Claim 3).

The above "main flight line" is defined as follows. When the evaporation material is evaporated from the evaporation source in the absence of an electric field or magnetic field, the particles of the evaporation material spread from the evaporation source as a source and fly radially with an angle. This radial extent is axisymmetric with respect to a particular straight line through the evaporation source.
This particular straight line is called the main flight line. A glass plate or a transparent plastic plate can be used as the transparent substrate. When using a transparent plastic plate, a "silicon oxide-based undercoat film" is formed on the surface on which the metal oxide film is formed.
The substrate on which the above is formed can be used (claim 4). The metal oxide film formed on the surface of the transparent substrate by the plasma vapor deposition method may be any one as long as it causes birefringence by oblique vapor deposition, but Ta ₂ O ₅ , WO ₃ , MoO ₃ , Bi ₂ O ₃ , Nb ₂
A film of O ₃ , CeO ₂ , ZrO ₂ , TiO ₂ , SnO ₂ or the like is particularly preferable (claim 5).

The birefringent plate of claim 6 is the birefringent plate manufactured by the method of claims 1 to 5. In this birefringent plate, "an antireflection film that exhibits an antireflection effect in combination with the metal oxide film" can be formed on the surface of the metal oxide film (claim 7).

[0012]

In FIG. 1, reference numeral 1 is a transparent substrate, reference numeral 2 is a metal oxide film, and reference numeral 3 is an evaporation source. As shown
The X and Y directions are defined in parallel with the surface of the transparent substrate 1, and the Z direction is taken orthogonal to the surface. Reference numeral 4 indicates the "flying direction" of the evaporated substance from the vapor deposition source. Therefore, the angle in the figure: θ represents the tilt angle of the surface of the transparent substrate 1 with respect to the flying direction 4.

In the state shown in FIG. 1, when the metal oxide film is vapor-deposited from the vaporization source 3 obliquely to the transparent substrate 1, the metal oxide film is vapor-deposited by the so-called "self-shadow effect". Is controlled, so "connection between particles"
Is likely to occur in the X direction and is unlikely to occur in the Y direction. Therefore, the density of the formed metal oxide film 2 is higher in the X direction than in the Y direction. Since the microscopic particle array structure in the metal oxide film 2 is sufficiently smaller than the wavelength of light, the refractive index Nx in the X direction is equal to the refractive index Ny in the Y direction.
Higher than that, and birefringence occurs. The flying direction 4 is the direction of the optical axis in the crystal structure of the formed metal oxide film 2.

When light is transmitted through the metal oxide film 2 shown in FIG. 1 in the Z direction, the light is divided into a linearly polarized light component in the X direction having the slowest phase velocity and a linearly polarized light component in the Y direction having the fastest phase velocity. move on. Therefore, as shown in FIG. 2A, when the light composed of the linearly polarized light component 40 in the X direction and the linearly polarized light component 50 in the Y direction is transmitted through the metal oxide film 2 in the Z direction, the transmitted light is as shown in FIG. As shown in (B), the linear polarization component 40 in the X direction is delayed by Γ with respect to the linear polarization component 50 in the Y direction. This delay amount: Γ is called retardation. Retardation: Γ is expressed as follows using the above-mentioned refractive indices Nx and Ny, where d is the thickness of the metal oxide film 2. Γ = (Nx−Ny) d Therefore, by adjusting the thickness: d of the metal oxide film 2, a birefringent plate having the functions of a λ / 2 wave plate, a λ / 4 wave plate, a λ / 8 wave plate, etc. Can be obtained.

Further, with respect to the optical axis direction of the metal oxide film 2, +
When the light linearly polarized in the direction of 45 degrees, that is, in the direction inclined by 45 degrees with respect to the X and Y amount directions is transmitted, the phase difference of the vibration components in the X and Y directions becomes the largest, so that the linearly polarized light The effect of polarization such as circular polarization is maximized.

When the vapor deposition of the metal oxide film 2 shown in FIG. 1 is performed by vacuum vapor deposition, the flight trajectory of the vaporized substance becomes substantially a straight line, so the incident angle of the vaporized particles on the transparent substrate surface is the transparent substrate 1.
According to the widths in the X and Y directions of the above, the tilt angle: changes considerably around θ. However, when oblique deposition is performed by the “plasma deposition method” as in the present invention, a counter electrode is formed behind the transparent substrate 1. The electric field lines of the electric field directed from the grid to the counter electrode are substantially orthogonal to the direction of the transparent substrate, and the particles of the evaporated substance are accelerated by the electric field.
The particles incident on the surface of the transparent substrate are deflected from the original flying direction to a direction slightly orthogonal to the surface, which effectively alleviates the change in the tilt angle. Therefore, in the metal oxide film formed by the method of the present invention, the positional variation of the optical axis is small.

Further, when the metal oxide film is formed by the method of claim 3, since the evaporation source and the transparent substrate are relatively displaced in the Y direction of FIG. 1, the change in the flying direction of the evaporated substance in the Y direction is average. It is possible to form a metal oxide film having better birefringence.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference numeral 10 in FIG. 3 schematically shows an example of a plasma vapor deposition apparatus for carrying out the method for manufacturing a birefringent plate of the present invention. An evaporation source 3, a filament 5, a grid 6, a counter electrode 8 and the like are provided in a bell jar indicated by reference numeral 7.

The counter electrode 8 holds the transparent substrate 1 on its grid 6 side surface. The counter electrode 8 can adjust its position in a swinging manner with a straight line that is parallel to the direction orthogonal to the drawing of FIG. 3 and that passes through the central portion of the electrode surface as an axis, and the main flight line indicated by reference numeral 4A is the reference flight direction. The posture is adjusted so that the inclination angle θ of the transparent substrate surface with respect to the flying direction is 70 degrees.

FIG. 4 shows the plasma deposition apparatus shown in FIG.
The state seen from the left side of FIG. 3 is shown. The counter electrode 8 is
With the transparent substrate 1 held, it can be displaced in the left-right direction of the figure (referred to as the direction A, which corresponds to the direction orthogonal to the drawing of FIG. 3). Reference numeral 9 indicates a baffle plate. Because of this baffle plate 9, when plasma deposition is performed while displacing the transparent substrate 1 held by the counter electrode 8 in the direction A, the flying direction of the vaporized substance in the direction A is only on the both sides of the main flight line 4 by the angle: α. Change. The size of this angle: α is set to 30 degrees or less.

As described above, the "arrival direction" of the vaporized substance
Is defined as the direction of the flight trajectory of the vaporized material that is incident near the central portion of the transparent substrate surface in the absence of an electric field or magnetic field, so that the transparent substrate 1 is displaced in the A direction as in the example in the description. When oblique vapor deposition is performed, the flying direction itself also changes. The direction of the main flight line set as the flight direction is referred to as the "reference flight direction", and in consideration of this point, it means that the inclination angle of the transparent substrate surface is set with the main flight line as the reference. ..

Specific examples will be described below. Example 1 Counter electrode 8 of plasma deposition apparatus 10 described in FIGS.
Further, a 50 mm × 50 mm glass plate was supported as the transparent substrate 1, and the inclination angle with respect to the main flight line 4A was set to 70 degrees. Metal Sn was put in the evaporation source 3. Angle shown in FIG. 4: α
Was set to 30 degrees, and the oblique deposition was performed by the plasma deposition method while moving the counter electrode 8 in the arrow direction (direction A) in FIG.

Inside the bell jar 7 is 10 to ⁶ by an exhaust pump.
The degree of vacuum is set to Torr or lower, and reactive O is used as an introduced gas.
_Two gases are introduced at a pressure of 9 × 10 to ⁵ Torr or more. A voltage is applied between the grid 6 and the counter electrode 8 so that an electric field from the grid 6 to the counter electrode 8 is generated, and thermoelectrons are emitted from the filament 5 to ionize O ₂ gas and generate plasma. To do. The evaporated substance Sn was locally heated by an electron beam to be evaporated, and a tin oxide thin film was formed to a thickness of 1.6 μm by plasma deposition.

The birefringent plate manufactured in this manner has a wavelength of λ /
It can be used as a four-wave plate.

Example 2 On the tin oxide thin film of the birefringent plate manufactured in Example 1, S
A film of iO ₂ was formed to a thickness of about 195 nm to form an antireflection layer. In this way, a birefringent plate with high light efficiency could be manufactured. MgF ₂ is also suitable as the material of the antireflection film.

Example 3 Tin oxide: SnO ₂ was put into the vapor deposition source 3 of the plasma vapor deposition apparatus 10 and the angle α in FIG. 4 was set to 20 degrees. Then, oblique vapor deposition was carried out in the same manner as in Example 1 to obtain a transparent substrate. 0.8μ thickness on top
m thin film of tin oxide was formed. The birefringent plate manufactured in this way can be used as a λ / 8 wave plate.

Example 4 Tantalum pentoxide: Ta was used as a vapor deposition source of the plasma vapor deposition apparatus 10.
₂ O ₅ was added, the angle α in FIG. 4 was set to 20 °, and then oblique vapor deposition was carried out in the same manner as in Example 1 to form a tantalum pentoxide film with a thickness of 1.5 μm on the transparent substrate. The birefringent plate manufactured in this way can be used as a λ / 4 wavelength plate.

Example 5 Tungsten: W was put into the vapor deposition source 3 of the plasma vapor deposition apparatus 10 and the angle α in FIG. 4 was set to 20 °. Then, oblique vapor deposition was carried out in the same manner as in Example 1 to form a transparent substrate. Thickness 0.9μ
m tungsten oxide film was formed. The birefringent plate manufactured in this way can be used as a λ / 8 wave plate.

On the metal oxide film of the birefringent plate manufactured in Examples 3, 4 and 5, SiO ₂ or MgF ₂ is added to about 195.
An antireflection film can be formed by forming a film with a thickness of nm.

Each of the birefringent plates of Examples 1 to 5 is
Since the metal oxide film is obliquely deposited by the plasma deposition method, the density of the metal oxide film is higher than that of the thin film formed by oblique deposition by vacuum deposition, and the adhesion to the transparent substrate and the mechanical strength of the film itself are stronger. There are also few voids. In addition, these Example 1
The thin films of tin oxide, tantalum pentoxide, and tungsten oxide, which are the metal oxide films of the birefringent plates of Nos. 5 to 5, have higher birefringence than the thin films of SiO ₂ and TiO ₂ known as birefringent thin films, Since the birefringence variation is very small, the film thickness can be made thin and the birefringence is stable. Further, as in Examples 1 to 5, when vapor deposition is performed at a vapor deposition angle controlled with high precision, light is incident in a direction of 45 degrees with respect to the optical axis of the formed metal oxide film. The incident light can be deflected without tilting the refraction plate.

When the same oxide as the metal oxide film formed on the transparent substrate is used as the evaporation material as in Examples 2, 3 and 4, compared with the case where the metal itself is used as the evaporation material. The pressure during vapor deposition is easy to adjust, and the reaction with oxygen only needs to be supplementary to the material metal atoms dissociated from oxygen during vaporization, so the rate of film formation can be increased and manufacturing efficiency can be improved. Is good.

[0032]

As described above, according to the present invention, a novel birefringent plate and a method for manufacturing the same can be provided. The birefringent plate of the present invention has a high density because the metal oxide thin film formed on the transparent substrate surface is formed by the plasma deposition method,
Therefore, the birefringence is high. Further, the metal oxide film has a strong adhesion to the substrate and a high mechanical strength, which facilitates mechanical handling.

Further, by providing an antireflection film on the surface of the metal oxide film as in the birefringent plate of the seventh aspect, it is possible to increase the light utilization efficiency in the optical device using the birefringent plate.

As the transparent substrate, an optical lens can be used in addition to those described above. That is, the metal oxide film may be directly formed on the lens surface of the optical lens.
In this case, a wave plate having a lens effect can be realized.

[Brief description of drawings]

FIG. 1 is a diagram for explaining oblique vapor deposition.

FIG. 2 is a diagram for explaining birefringence.

FIG. 3 is a diagram for explaining an example of a plasma deposition apparatus for carrying out the method for manufacturing a birefringent plate of the present invention.

FIG. 4 is a diagram illustrating a state of the apparatus of FIG. 3 viewed from the left side of FIG.

[Explanation of symbols]

 1 transparent substrate 2 metal oxide film 3 evaporation source 4 direction of evaporation material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazuhiro Umeki, Kazuhiro Umeki, 10th District, Ohata, Hanamaki City, Iwate Prefecture, 109, Rico Optical Co., Ltd. (72) Yuji Onodera, 3-5-7 Wakaba Town, Hanamaki City, Iwate Prefecture・ Heimeagle Room 2-1

Claims (7)

[Claims] 1. The positional relationship between the transparent substrate surface and the evaporation source is set so that the evaporated substance may fly from a direction inclined by 40 to 80 degrees with respect to the transparent substrate surface, and the pressure of the introduced gas is set to 9 × 10 to ^5.
A method of manufacturing a birefringent plate, which comprises forming a thin film of a metal oxide to a desired thickness by a plasma deposition method in a state of Torr or more. 2. The tilt angle of the surface of the transparent substrate with respect to the incoming direction of the vaporized material according to claim 1,
A method of manufacturing a birefringent plate, wherein the birefringent plate is about 70 degrees. 3. A direction perpendicular to a plane including the normal line standing on the transparent substrate surface and the main flight line at the intersection of the main flight line of the vaporized substance and the transparent substrate surface, as defined in claim 1 or 2. In this case, the direction of the main flight line is defined as the incoming direction of the evaporation material, and the evaporation source and the transparent substrate are
A method of forming a metal oxide film to a desired film thickness by plasma vapor deposition while relatively displacing it in the direction A, in which the relative range of movement of the evaporation source and the transparent substrate in the A direction is seen from the evaporation source. And a range of 30 degrees or less on both sides of the main flight line. 4. The method for producing a birefringent plate according to claim 1, 2 or 3, wherein the transparent substrate is a transparent plastic plate on which a silicon oxide-based undercoat film is formed. 5. The metal oxide film according to claim 1, 2 or 3 or 4, wherein the metal oxide film formed by plasma deposition is Ta ₂
O ₅ , WO ₃ , MoO ₃ , Bi ₂ O ₃ , Nb ₂ O ₃ , CeO ₂ ,
A method for producing a birefringent plate, which is a film of any one of ZrO ₂ , TiO ₂ , and SnO ₂ . 6. A birefringent plate manufactured by the method according to claim 1, 2 or 3 or 4 or 5. 7. The birefringent plate according to claim 6, wherein an antireflection film exhibiting an antireflection effect in combination with the metal oxide film is formed on the surface of the metal oxide film.