JPH11337733A - Double refractive plate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To function plural diagonally vapor deposited films as a wavelength plate in a wide band of visible rays by laminating these films and utilizing the formability of a phase difference and to ameliorate the peeling at an adjacent boundary by the internal stress of the films themselves generated by the thickness increase accompanying the same. SOLUTION: Dielectric materials are deposited by evaporation on a solid substrate 23 from a direction diagonal with the normal 26 of the substrate surface 23, by which the diagonally vapor deposited films 21, 22 are formed. The diagonally vapor deposited films 21, 22 are formed on the opposite two surfaces of the solid substrate 23 and are manufactured by using the material exhibiting high wavelength dispersion and the material exhibiting low wavelength dispersion in the phase difference respectively, forming the double refractive films 24, 25 dividedly on the opposite two surfaces of the solid substrate 23 and intersecting the vapor deposition directions of the dielectric materials of the respective layers with the solid substrate 23 orthogonally with each other in such a manner that the lagging axes of the double refractive films 24, 25 intersect orthogonally with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to optical devices and optical elements that require circularly polarized light, linearly polarized light, and elliptically polarized light, and provides a birefringent plate that functions efficiently over a wide band. Things.

[0002]

2. Description of the Related Art Most conventional birefringent plates are made of an inorganic optical single crystal or a stretched polymer film. However, although the inorganic optical single crystal is excellent in performance, durability, and reliability as a wave plate, the raw material cost and the processing cost are high.

[0003] Further, the stretched polymer film has a disadvantage that it is easily deteriorated by heat and ultraviolet rays and has a problem in durability.

On the other hand, an oblique deposition film having an oblique columnar structure is:
Arbitrary phase difference can be set by adjusting the film thickness in principle, and it is relatively easy to increase the area, and there is a possibility of cost reduction by mass production.

However, in the conventional obliquely deposited film made of a single material, the wavelength dispersion characteristic of the phase difference generally becomes a monotonically decreasing curve as the incident light wavelength becomes longer in the visible light region. However, it functioned as a wave plate only for a specific single wavelength.

In order to improve this, Japanese Patent Application No. 09-174 discloses
The invention filed as Japanese Patent No. 909 uses a diagonal vapor deposition method to form a birefringent plate by vapor-depositing and laminating a plurality of types of birefringent diagonally vapor-deposited films, and utilizes the additive property of a phase difference. Thereby, it functions efficiently over a wide band.

[0007]

However, in order to obtain a function as a quarter-wave plate in a wide band of visible light, for example, a plurality of types of obliquely deposited films are laminated and a deposited film of at least about 5 to 6 μm is required. And a thick film must be formed.

In the formation of a thick film, peeling occurs at the interface with the solid substrate and at the adjacent interface between the deposited films due to the internal stress of the film itself. In particular, in the case of the oblique columnar structure film formed by the oblique deposition method, the first layer is formed. When oblique deposition is performed on the oblique columnar structure film formed on the solid substrate with the deposition direction orthogonal to the solid substrate, the adhesive force is reduced at the interface and the subject is easily peeled off.

[0009]

In order to solve the above problems, a birefringent plate having a birefringent dielectric material formed on two surfaces opposed to each other with a solid substrate interposed therebetween has a birefringence Δ
n (α = Δn _{(450 nm)} / Δn _{(650 nm)} ) is expressed as α _A > α _B (wavelength dispersion of dielectric material A: α _A ,
Dielectric material A having wavelength dispersion value of dielectric material B: α _B )
And B are respectively formed on two opposing surfaces of the solid substrate, and the phase difference R is R _A <R _B (the phase difference due to the dielectric material A:
R _A , which has a relationship of phase difference due to the dielectric material B: R _B ),
And each slow axis of the dielectric material having birefringence is characterized by being orthogonal, and the dielectric material is formed by being deposited obliquely with respect to the solid substrate surface normal. It is characterized by comprising an obliquely deposited film.

The manufacturing method is characterized in that the dielectric materials A and B formed via the solid substrate are manufactured so that the incident surfaces of the vapor-deposited particles on the solid substrate are orthogonal to each other.

The dielectric material is at least one of a metal oxide, a metal fluoride and a metal sulfide, and an antireflection film is formed on at least one surface of the solid substrate via the dielectric material on both surfaces. It is characterized in that a film is formed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The birefringent plate formed by the oblique vapor deposition forms an oblique columnar structure film by evaporating particles from a diagonal direction with respect to a solid substrate, and vertically enters the solid substrate. It has birefringence to light rays.

In oblique deposition, nuclei are formed in a well-known manner in the initial stage of deposition. However, when the nuclei grow and have a certain height, the nuclei are deposited obliquely as shown in FIG. Since the material comes flying, behind the nucleus when viewed from the incident direction of the deposition material, there is a shadow to which the deposition material cannot directly adhere. This is generally called the self-shadowing effect.
(Refer to NTT Co., Ltd., 1995)), which is one of the main factors in which the obliquely deposited film exhibits a unique form.

Due to this self-shadowing effect, the deposition angle θ is reduced from the normal to the solid substrate surface by a smaller angle α.
As a result, the inclined columnar structure grows. Since this columnar structure is coarse in the direction parallel to the incident surface of the particles and densely distributed in the perpendicular direction, the refractive index is the smallest in the former direction, the refractive index is the largest in the latter direction, and from the incident direction of the deposited particles. Seemingly, it forms an optically anisotropic medium. As a result, the cross section of the refractive index ellipsoid becomes an ellipsoid even for a light beam incident from the normal direction of the solid substrate surface, and the obliquely deposited film has birefringence. (Hereinafter, the obliquely deposited film is referred to as a birefringent film.)

Further, in order to realize a wide band, materials having different wavelength dispersion characteristics of the phase difference are used, the slow axes of the birefringent films are formed so as to be orthogonal to each other on the surface of the solid substrate, and are laminated in a multilayer structure. Here, since the slow axis coincides with the optical axis of the birefringent medium, that is, the deposition direction with respect to the solid substrate, in order to make the slow axis orthogonal, the evaporation direction is made orthogonal to the solid substrate surface by oblique evaporation. Then, a birefringent film may be formed. However, in the formation of a thick film having a multilayer structure, peeling easily occurs at the interface with the solid substrate and at the adjacent interface between the deposited films due to the internal stress of the film itself. In order to avoid such peeling, a birefringent film is formed by dividing the solid substrate into two opposing surfaces as shown in FIGS. 2 and 3, and at this time, the deposition directions are orthogonalized as described above. By performing oblique deposition, the birefringent films are formed with their slow axes orthogonal to each other. That is, in FIG. 4, a desired film thickness is formed by the evaporation source 41 by oblique evaporation, and then a desired film thickness is similarly formed using a different material from the evaporation source 44 to produce a birefringent plate. .

As described above, by forming the birefringent films of different vapor deposition materials on both sides of the solid substrate, the adhesive force at the interface is improved, and by utilizing the additive property of the phase difference, It is possible to realize a broadband wavelength plate with improved wavelength dispersion characteristics of the birefringent film.

That is, the present invention solves the problem of peeling of a vapor deposition film caused by thickening due to widening of the wavelength plate function by dividing the vapor deposition film into two opposing surfaces via a solid substrate, thereby forming an oblique columnar structure film. The purpose is to eliminate the interface between them and improve the adhesion strength of the birefringent film.

The thickness of each deposited film (birefringent film) and the deposition angle (the angle between the normal to the substrate surface and the direction in which the deposited particles fly) are required for the deposited film (birefringent film). It needs to be optimized to function as a desired wave plate, depending on the phase difference.

[0019]

The present invention will be described below with reference to specific examples. FIG. 1 is a side view of a vacuum evaporation apparatus showing an example of an evaporation apparatus used in the present invention.

The vacuum vapor deposition apparatus shown in FIG. 1 will be described. The vacuum vapor deposition apparatus has a bell jar 16 whose inside is evacuated by an exhaust pump (not shown), an evaporation source 15 for evaporating various evaporation materials, and It is composed of a substrate holder 12 and the like provided on the upper part. Regarding the evaporation source 15, regardless of its type, a source that is locally heated using resistance heating, an electron beam, a laser beam, or the like may be used.

The inside of the bell jar 16 is provided with the exhaust hole 1.
The pump 4 is connected to an exhaust pump (not shown) through the pump 4 so that the exhaust pump can exhaust air to the order of 10 ^-6 Torr.

By using the apparatus shown in FIG. 1, a metal compound as a vapor deposition material is heated and evaporated on the solid substrate 11 and an appropriate vapor deposition angle is set, thereby producing a birefringent plate with an oblique vapor deposited film.

In the embodiments described below, tantalum pentoxide (Ta ₂ O ₅ ) and lanthanum fluoride (LaF) are used as dielectric materials.
_{Although 3} ) was used, these may be any material that is transparent to visible light, and may be CeO ₂ , WO ₃ , Bi ₂ O ₃ , Sn
O ₂ , ZnS, NdF _3, etc. can be used. However, in consideration of the wavelength dispersion characteristics of the phase difference of each vapor-deposited film, a dielectric material that can be optimized by using the additivity of the phase difference must be selected. Must.

The thickness and material of the solid substrate are not particularly limited as long as the substrate has excellent transparency, a refractive index of 1.40 to 1.60, a low birefringence and excellent heat resistance. The material is not limited, and examples thereof include a glass substrate and a plastic substrate. As a material of the antireflection film, MgF2, SiO2, or the like is preferable.

A specific embodiment will be described below. In this embodiment, an example of the manufacturing method is described, and the present invention is not limited to this. (Example 1) In FIG. 1, a glass substrate was used as the solid substrate 11, and the deposition particles had an inclination angle θ = 7 with respect to the glass substrate.
It was set to enter at 0 °. Ta ₂ O ₅
(Tantalum pentoxide) was used. The wavelength dispersion value of the evaporant Ta ₂ O ₅ : α _A (= Δn _{(450 nm)} / Δn _{(650 nm)} ) is 1.
It was 18. The evaporating substance Ta ₂ O ₅ is heated and evaporated by passing a current through a resistance heating boat, and Ta ₂ O ₅
Phase difference R _{A (550 nm)} at an incident light wavelength λ = 550 _nm
= 137.5 nm, a film thickness of 1.7 μm is formed,
Further, an MgF ₂ evaporated film was formed to a thickness of about 0.1 μm on the evaporated film to form an antireflection film, thereby obtaining an upper birefringent film 21 shown in FIG.

Next, the glass substrate is set so that the incident surface of the vapor-deposited particles is perpendicular to the incident surface on the substrate surface on the opposing surface of the glass substrate (see FIG. 4), and is incident at an inclination angle θ = 70 °. Was set as follows. LaF ₃ (lanthanum fluoride) was used as a vapor deposition material. The wavelength dispersion value of the evaporating substance LaF ₃ : α _B = Δn _{(450 nm)} / Δn _{(650 nm)} was 1.04. The evaporating substance LaF ₃ is heated and evaporated by passing an electric current through a resistance heating boat, and the LaF ₃ thin film is made to have a phase difference R _{B (550 nm)} at an incident light wavelength λ = 550 nm of 275 nm.
Was formed to a thickness of 4.0 μm.

Further, an MgF ₂ evaporated film is formed to a thickness of about 0.1 μm on the evaporated film to form an anti-reflection film.
Was produced to obtain the birefringent plate. FIG. 3 is a sectional view of the birefringent plate. The birefringent plate configured as described above functions as a quarter-wave plate.

Comparative Example 1 In the same manner as in Example 1, a glass substrate was used as the solid substrate 11, and the evaporation particles were set to enter the glass substrate at an inclination angle θ = 70 °. Ta ₂ O ₅ is heated and evaporated by passing a current through a resistance heating boat so that the thin film of Ta ₂ O ₅ has a phase difference _{RA (550 nm)} at an incident light wavelength λ = 550 nm of 137.5 _nm. By forming a film having a thickness of 1.7 μm, Ta ₂ O ₅
Is used as a single material and consists of only one layer of obliquely deposited film.
A / 4 wavelength plate was obtained.

Comparative Example 2 In the same manner as in Example 1, a glass substrate was used as the solid substrate 11, and the vapor deposition particles were set to enter the glass substrate at an inclination angle θ = 70 °. Ta ₂ O ₅ was used as an evaporation material. The evaporating substance Ta ₂ O ₅ is heated and evaporated by passing an electric current through the resistance heating boat, and the Ta ₂ O ₅ thin film is made to have a phase difference _{RA (550 nm) of} 137.5 nm at an incident light wavelength λ = 550 nm. So that the film thickness is 1.
7 μm was formed.

Next, the glass substrate was set so that the incident surface of the vapor deposition particles was perpendicular to the incident surface on the substrate surface, and the tilt angle θ was set to 70 °. LaF _{3 for} evaporation material
, And similarly heated and evaporated by a resistance heating boat, and a LaF ₃ thin film was laminated to a thickness of 4.0 μm so that the phase difference R _{B (550 nm)} at an incident light wavelength λ = 550 _nm = 275 nm. Further, an MgF ₂ deposited film was formed on the
μm to form an antireflection film. The birefringent plate thus manufactured with a laminated structure functions as a quarter-wave plate.

(Effects of Example) Example 1 and Comparative Example 1
6 and 7 show the wavelength dispersion characteristics of the wavelength plate manufactured by the method described above. In FIG. 7, in order to function as an ideal wide-band quarter-wave plate, Δnd / λ is set to 0.
It should be 25. Here, comparing Example 1 with Comparative Example 1, it was found that at blue wavelength (λ = 480 nm), 0.31 →
0.28, which is about 50%, and the red wavelength (λ = 65
6 nm), 0.20 → 0.21 and about 20
%, Respectively, and can be provided as a quarter-wave plate having excellent functionality over a wide band.

Next, the adhesion of the obliquely deposited film is compared between Example 1 and Comparative Example 2. In order to evaluate the adhesion, a grid tape method based on Japanese Industrial Standards (JIS) was performed. Explaining the contents of implementation, according to a predetermined standard, a cut is made on the surface of the birefringent plate with a clearance of 5 mm and 9 squares on a grid, glued with a cellophane adhesive tape of a predetermined standard, and rubbed with an eraser. After the tape is adhered, one end of the tape is held at a right angle to the surface to which the tape is adhered, and the tape is instantaneously peeled off.

In the birefringent plate provided by Example 1,
The grid tape method was performed on both surfaces of the birefringent plate.
As a result of visual observation of the adhered state of the deposited film after the tape was peeled off, the birefringent plate of Example 1 did not peel off at both surfaces at a glance and maintained a good state.

On the other hand, when the birefringent plate according to Comparative Example 2 was similarly subjected to the cross-cut tape method, the width of peeling due to cuts was wide, the area of the defective portion was 15 to 35% of the total square area, and Peeling was confirmed. Thereby, Comparative Example 2
Plate with high functionality over a wide band
Although it can be provided as a 波長 wavelength plate, the adhesive strength is inferior to that of the birefringent plate according to Example 1, and the birefringent plate according to the present invention can be provided as compatible with both.

[0035]

As described above, the present invention relates to a birefringent plate using an obliquely deposited film using dielectric materials having different wavelength dispersion characteristics of retardation, wherein the birefringent film is formed on two opposing surfaces of a solid substrate. And the slow axes are orthogonal to each other.

As described in detail in the embodiments, the wave plate using the birefringent plate of the present invention not only functions as a wave plate for a single wavelength but also in a wide band while maintaining the conventional function. At the same time as functioning efficiently, the oblique deposition films are formed on the two opposing surfaces of the solid substrate to eliminate the interface between the oblique columnar structure films, thereby improving the adhesion strength of the oblique deposition films.

[Brief description of the drawings]

FIG. 1 is a side view showing one example of a vacuum evaporation apparatus for carrying out a method of manufacturing a birefringent plate of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a birefringent plate according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a birefringent plate according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a positional relationship between an evaporation source of a birefringent plate and a substrate according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a deposition angle θ and an inclination angle α of a columnar structure according to the present invention.

FIG. 6 is a diagram showing the wavelength dispersion characteristics of the wave plates of Example 1 and Comparative Example 1 of the present invention.

FIG. 7 is a diagram showing the wavelength dispersion characteristics of the functionalities of the wave plates of Example 1 and Comparative Example 1 of the present invention.

[Explanation of symbols]

 11: Solid substrate 12: Substrate holder 13: Power supply for heating 14: Exhaust hole 15: Evaporation source 16: Bell jar 17: Evaporation material 21: Upper birefringent film (oblique evaporation film) 22: Lower birefringent film (oblique evaporation) 23: solid substrate 24: slow axis of upper birefringent film 25: slow axis of lower birefringent film 26: substrate surface normal 31: solid substrate 32: birefringent film 41: evaporation source 42: solid substrate 43 : Oblique evaporation film 44: Evaporation source 45: Oblique evaporation film 46: Evaporation particle incidence surface of evaporation source 41 47: Evaporation particle incidence surface of evaporation source 44 51: Solid substrate 52: Incident angle θ 53: Inclination of columnar structure Angle α 54: Incident direction of deposition material 55: Inclination direction of columnar structure 56: Normal to substrate surface 57: Oblique deposition film

Claims (5)

[Claims] 1. A birefringent plate in which a dielectric material having birefringence is formed on two surfaces facing each other via a solid substrate,
Wavelength dispersion value of the birefringence Δn α (α = Δn _{(450 nm)} / Δn
Relationship _{(650 nm))} is, alpha _A> alpha dielectric materials A and B is _B are respectively formed on two opposing surfaces of the solid substrate, the phase difference R has a relation of R _A <R _B, A birefringent plate, wherein the slow axes of the birefringent dielectric material are orthogonal to each other. 2. The birefringent plate according to claim 1, wherein said dielectric material comprises an obliquely deposited film formed by being deposited from an oblique direction with respect to a normal to said solid substrate surface. 3. The birefringent plate according to claim 1, wherein the surfaces of the dielectric materials A and B formed via the solid substrate are perpendicular to the incident surfaces of the vapor-deposited particles on the solid substrate. Method for producing a birefringent plate. 4. The birefringent plate according to claim 1, wherein said dielectric material is at least one of a metal oxide, a metal fluoride and a metal sulfide. 5. A method according to claim 1, further comprising the steps of:
2. The birefringent plate according to claim 1, wherein the antireflection film is formed on at least one surface.