JPH09297214A - Polarizing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both of adhesion and antireflection of an oblique vapor deposition film by using the same material of the oblique vapor deposition film for the first layer of an antireflection film having at least two layers. SOLUTION: An oblique vapor deposition film 3 is formed into a columnar structure which grows as tilted from the substrate surface by arranging the substrate 1 tilted to the entering direction of an optical material in a vapor deposition device. Further, a first layer 4 of an antireflection film is formed on the oblique vapor deposition film 3 by using the same material as for the oblique vapor deposition film 3. Then a second layer 5 is formed under antireflection conditions. For example, light of 795nm wavelength is used for the optical element, the substrate 1 consists of glass and Ta2 O5 is used to form the oblique vapor deposition film 3. A Ta2 O5 film of 97nm thickness and a SiO2 film of 136nm thickness are formed by vapor deposition for the first layer 4 and second layer 5, respectively. The adhesion between the oblique vapor deposition film 3 and the first layer 4 of the antireflection film is firm because these films consist of the same material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing element using a diagonal vapor deposition film.

[0002]

2. Description of the Related Art Conventionally, as a polarizing element using an obliquely vapor-deposited film, one described in JP-A-5-132768 is known. FIG. 3 shows a schematic cross-sectional view of the invention described in this publication as an example of a polarizing element using an obliquely vapor-deposited film. An undercoat 22 is formed on a substrate 21 in advance, and an undercoat 22 is formed in the vapor deposition apparatus. The obliquely deposited film 2 is formed as a columnar structure in which the substrate 21 is arranged to be inclined with respect to the flying direction and grows obliquely from the substrate surface.
3 and the antireflection film 24 that is normally formed.

The obliquely deposited film has a refractive index anisotropy (birefringence) with respect to the plane of polarization of light and is used as a polarizing element such as a quarter wavelength plate.

[0004]

In an ordinary optical thin film (antireflection film, etc.) using vapor deposition or sputtering,
Although the adhesiveness between thin films or substrates (glass, transparent plastic, etc.) is not a problem, the obliquely deposited film has a large internal stress because it is formed as a columnar structure, and is composed of different materials due to expansion and contraction due to temperature change etc. There is a problem that the adhesiveness with the substrate or the antireflection film is deteriorated and peeling occurs. When either the obliquely vapor-deposited film using a metal oxide and glass or the metal oxide or the metal fluoride is an obliquely vapor-deposited film and the rest is an antireflection film, the adhesion is particularly poor and the film is easily peeled off.

In the conventional structure, in order to improve the adhesion with respect to the obliquely vapor-deposited film using a metal oxide, a silicon oxide undercoat is used on the substrate or an antireflection film using a metal oxide is used. Things have been disclosed.

However, as an optical material such as an antireflection film, a metal fluoride such as MgF2 or a metal oxide film such as SiO2 has been used for a long time, and it is known to use a metal oxide for the antireflection film. Further, for example, an undercoat improves the adhesion, but in an optical element, the refractive index of the substrate is N
s, assuming that the refractive index of the obliquely vapor-deposited film is No, an undercoat having a refractive index Nu of (Ns * No) ^1/2 is selected, and the optical thickness (film thickness d * Nu) is set to 1/4 of the wavelength. There is a need.
When the wavelength used is 795 nm, the substrate is glass (BK7, refractive index 1.51), and the oblique deposition film is Ta2O5 (refractive index 1.6 at oblique deposition), the optimum refractive index of the undercoat is 1.55. Silicon oxide (SiO2, refractive index 1.4
When 7) is used, the reflectance is 0.3%, which is higher than the reflectance of 0.1% without the undercoat.

Also in the case of the antireflection film, similarly, Ta2O5 which is a metal oxide is formed on the obliquely evaporated film (refractive index 1.
When 6) is used, the optimum refractive index is 1.26, and magnesium fluoride (MgF2, refractive index 1.38), which is a metal fluoride, is optimum (reflectance 0.7%), but adhesion is poor. In the case of metal oxides, silicon oxide (SiO2, refractive index 1.47) is close, but the reflectance is large (reflectance 2.2
%).

That is, in such a conventional technique, in order to prevent the reflection of light by the boundary surface, there is a restriction on the refractive index of the constituent material and thus on the material, and if the metal oxide is simply selected, the adhesion and the reflection can be reduced. It was difficult to achieve both prevention.

The present invention has been made for the purpose of providing a polarizing element capable of achieving both adhesion of an obliquely vapor-deposited film and antireflection.

[0010]

In order to solve this problem, the polarizing element of the present invention has a structure in which the first layer of the antireflection film consisting of at least two layers is made of the same material as the obliquely evaporated film. , Or an optical thickness obtained by multiplying the physical thickness by the refractive index (hereinafter abbreviated as optical thickness) with an undercoat formed to be 1/2 of the wavelength used, or a refractive index almost equal to that of the obliquely evaporated film An undercoat is formed of a metal oxide.

As a result, the adhesion of the obliquely vapor-deposited film can be ensured with almost no loss of light amount due to reflection.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a polarizing element having an oblique vapor deposition film having birefringence and an antireflection film in which an optical material is obliquely vapor-deposited, and the antireflection film is at least 2 The antireflection film, which consists of layers and is in contact with the obliquely evaporated film, is a polarizing element made of the same material as the obliquely evaporated film.
The anti-reflection film consisting of more than one layer can be selected as the first anti-reflection film because the combination of anti-reflection film materials can be selected relatively freely.
By providing an antireflection film composed of two or more layers in which the second layer is the same material as the obliquely evaporated film, not only the antireflection but also the adhesion can be secured.

According to a second aspect of the present invention, in a polarizing element having an obliquely evaporated film having birefringence by obliquely evaporating a metal oxide on a substrate, an optical thickness is used between the obliquely evaporated film and the substrate. Is a polarizing element having a metal oxide having a wavelength of ½, and the intensity of reflected light is the same as when the oblique deposition film and the substrate or the antireflection film are in direct contact,
There is an effect that the adhesiveness can be secured with almost no loss of light amount due to reflection.

According to a third aspect of the present invention, in a polarizing element having an obliquely vapor-deposited film having birefringence by obliquely vapor-depositing a metal oxide and an antireflection film, between the obliquely vapor-deposited film and the antireflection film. , A polarizing element having a metal oxide whose optical thickness is 1/2 of the wavelength used, and the intensity of reflected light is the same as when the obliquely vapor-deposited film and the substrate or the antireflection film are in direct contact. As in the case of the invention described in Item 2, there is an effect that the adhesiveness can be secured with almost no loss of light amount due to reflection.

According to a fourth aspect of the present invention, in a polarizing element having an obliquely evaporated film having birefringence by obliquely evaporating an optical material on a substrate, the optical thickness is used between the obliquely evaporated film and the substrate. It is a half of the wavelength, and is a polarizing element having a film made of the same material as the obliquely vapor-deposited film. As with the invention described in claim 2, there is almost no loss of light quantity due to reflection, and since it is the same material, the adhesiveness is In addition to being improved, it has an effect that it is effective not only for metal oxides but also for metal fluorides and metal thin films.

According to a fifth aspect of the present invention, in a polarizing element having an obliquely vapor-deposited film having an optical material obliquely vapor-deposited and having a birefringence and an antireflection film, between the obliquely vapor-deposited film and the antireflection film, It is a polarizing element having an optical thickness of ½ of the wavelength used and having a film made of the same material as the obliquely vapor-deposited film, and there is almost no loss of light quantity due to reflection as in the invention of claim 2, and the same material. Therefore, the adhesiveness can be further improved, and it is effective not only for metal oxides but also for metal fluorides and metal thin films.

The invention according to claim 6 or 7 has a metal oxide having a refractive index substantially equal to that of the obliquely-deposited film between the obliquely-deposited film and the substrate, or at least on the obliquely-deposited film, or the substrate. It is a polarizing element that has a metal oxide with the same refractive index as the above. Optically, it means that the obliquely deposited film or substrate is thick, but it is ignored because the obliquely deposited film and the substrate are very thick compared to the wavelength. This has the effect that the adhesiveness can be secured with almost no loss of the light amount due to reflection.

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. (Embodiment 1) FIG. 1 shows a schematic cross section of a polarizing element according to an embodiment of claim 1 of the present invention.
1 is a substrate, 3 is an obliquely evaporated film, 4 is a first antireflection film,
Reference numeral 5 denotes a second-layer antireflection film, which is a columnar structure that grows in an oblique direction from the surface of the substrate by performing vapor deposition by arranging the substrate 1 in a vapor deposition apparatus with the substrate 1 inclined with respect to the flying direction of the optical material. As a result, the obliquely deposited film 3 is formed.
Furthermore, on the obliquely vapor-deposited film 3, a first layer of an antireflection film made of the same material as the obliquely vapor-deposited film 3 and a second layer of the antireflection film selected from non-reflective conditions are formed.

The operation of the polarizing element having the above structure will be described below. As an example, the wavelength used is 795 nm, the substrate is made of glass (BK7, refractive index 1.
51), Ta2O5 is used for the obliquely evaporated film (refractive index of 1.6 when obliquely evaporated), and Ta2O5 is used for the first layer of the antireflection film.
(Refractive index 2.0) is deposited to 97 nm, and SiO2 (refractive index 1.47) is deposited to 136 nm to the second layer of the antireflection film so that the reflectance becomes 0.5%. The adhesiveness of is also strong because it is made of the same material.

As described above, according to this embodiment, it is possible to secure the adhesion between the obliquely vapor-deposited film and the antireflection film with almost no loss of light amount due to reflection.

(Embodiment 2) Next, FIG. 2 shows a schematic cross section of a polarizing element according to an embodiment of claim 2, and FIG.
In FIG. 1, 1 is a substrate, 2 is an undercoat for improving adhesion, 3 is a diagonal vapor deposition film, and 6 is an antireflection film, respectively. After the undercoat 2 made of a metal oxide is formed on the substrate 1 in advance, vapor deposition is performed. By obliquely arranging the substrate 1 in the apparatus with respect to the flying direction of the optical material and vapor-depositing the metal oxide, the oblique vapor deposition film 3 is formed as a columnar structure that grows in an oblique direction from the substrate surface. Further, an undercoat having the same specifications as the above undercoat is formed on the obliquely vapor-deposited film 3, and then the obliquely vapor-deposited film and an antireflection film 6 formed under a non-reflective condition obtained from the refractive index of air are used.

The operation of the polarizing element having the above structure will be described below. As an example, the wavelength used is 795 nm, the substrate is made of glass (BK7, refractive index 1.
51), Ta2O5 (refractive index of 1.6 at the time of oblique deposition) is used for the obliquely evaporated film, and SiO2 (refractive index of 1.47) is evaporated as an undercoat at 270 nm which is 1/2 of the optical thickness to form an antireflection film. Is the same as when there is no undercoat (SiO2) because the reflectance becomes 0.7% by vapor-depositing magnesium fluoride (MgF2, refractive index 1.38) which is ¼ of the optical thickness. Also, since the adhesion between the obliquely deposited film and the undercoat is the same oxide, the adhesion is strong, and the undercoat and the antireflection film are ordinary optical thin films using vapor deposition or sputtering (about 90 degrees to the substrate. Since the film is formed), the adhesion between the undercoat and the substrate and the adhesion between the undercoat and the antireflection film are strong.

As described above, according to the present embodiment, the antireflection film material, which has a small loss of light amount due to reflection but cannot be used due to poor adhesion, has almost no loss of light amount, and the oblique vapor deposition film and the antireflection film are not used. The adhesion between the film or the obliquely evaporated film and the substrate can be secured.

Further, if the same material as the obliquely vapor-deposited film material is used as the undercoat, the adhesion can be further improved.
Also, if an undercoating material having the same refractive index as that of the obliquely evaporated film material is used, there is no loss of light quantity regardless of the thickness of the undercoating film, and the adhesion between the obliquely evaporated film and the antireflection film or the obliquely evaporated film and the substrate is improved. It can be secured. However, among the commonly used optical materials, it is not possible to have the same refractive index. Therefore, it is desirable to use an optical material having a refractive index difference of 20% or less (a refractive index difference of 20%).
However, the reflectance is less than 1% and there is no problem). For example, if Ta2O5 (refractive index of 1.6 during oblique deposition) is used for the obliquely evaporated film and Al2O5 (refractive index of 1.65) is used as the undercoat, the reflectance is 0.
It becomes 4% or less, and there is almost no loss of light quantity, and the adhesion between the obliquely evaporated film and the antireflection film or the obliquely evaporated film and the substrate can be secured.

The obliquely vapor-deposited film is the same as that formed by not only vapor deposition but also sputtering, and conventional optical materials (metal oxides: TiO2, CeO2, WO2, etc.) are used as the obliquely vapor-deposited film, the antireflection film and the undercoat material. Metal film: Cr,
It goes without saying that Au, Cu, etc.) can be used.

[0026]

As described above, according to the present invention, there is almost no loss of light amount, the adhesion between the obliquely vapor-deposited film and the antireflection film or the obliquely vapor-deposited film and the substrate can be secured, and further, the loss of the light amount due to reflection is achieved. However, the advantageous effect that an antireflection film material which cannot be used due to poor adhesiveness can be used can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a polarizing element according to an embodiment of claim 1 of the present invention.

FIG. 2 is a schematic sectional view of a polarizing element according to an embodiment of claim 1 of the present invention.

FIG. 3 is a schematic sectional view of a conventional polarizing element.

[Explanation of symbols]

 1, 21 Substrate 2, 22 Undercoat 3, 23 Oblique vapor deposition film 4 1st layer antireflection film 5 2nd layer antireflection film 6, 24 Antireflection film

Claims (7)

[Claims] 1. A polarizing element having an obliquely vapor-deposited film having birefringence formed by obliquely vapor-depositing an optical material and an antireflection film, wherein the antireflection film comprises at least two layers, and the antireflection film is in contact with the obliquely vapor-deposited film. Is the same material as the obliquely deposited film, and is a polarizing element. 2. A polarizing element having an obliquely evaporated film having birefringence obtained by obliquely evaporating a metal oxide on a substrate,
A polarizing element comprising a metal oxide having an optical thickness obtained by multiplying a physical thickness by a refractive index to be 1/2 of a wavelength used, between the obliquely deposited film and the substrate. 3. A polarizing element having an obliquely vapor-deposited film having birefringence obtained by obliquely vapor-depositing a metal oxide, and an antireflection film, wherein a refractive index in physical thickness is provided between the obliquely vapor-deposited film and the antireflection film. A polarizing element comprising a metal oxide having an optical thickness multiplied by ½ of a wavelength used. 4. A polarizing element having an obliquely evaporated film having birefringence by obliquely evaporating an optical material on a substrate, wherein an optical thickness obtained by multiplying a physical thickness by a refractive index is used between the obliquely evaporated film and the substrate. A polarizing element having a film of the same material as that of the obliquely evaporated film, which is half the wavelength of the polarized light. 5. A polarizing element having an obliquely vapor-deposited film having birefringence formed by obliquely vapor-depositing an optical material, and an antireflection film, wherein a refractive index is provided in physical thickness between the obliquely vapor-deposited film and the antireflection film. A polarizing element, characterized in that the multiplied optical thickness is ½ of the wavelength used and has a film made of the same material as the obliquely evaporated film. 6. A polarizing element having an obliquely evaporated film having birefringence obtained by obliquely evaporating a metal oxide on a substrate,
A polarizing element comprising a metal oxide having a refractive index substantially equal to that of the obliquely evaporated film between at least one of the obliquely evaporated film and the substrate or on the obliquely evaporated film. 7. A polarizing element having an obliquely evaporated film having birefringence obtained by obliquely evaporating a metal oxide on a substrate,
A polarizing element comprising a metal oxide having the same refractive index as that of the substrate between the obliquely deposited film and the substrate.