JP3402122B2 - Filter that polarizes light in a specific wavelength range - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter which polarizes light in a specific wavelength range, and more particularly, the present invention polarizes light having a relatively large area suitable for forming an alignment film on a liquid crystal substrate. The present invention relates to a polarizing filter for.

[0002]

2. Description of the Related Art In recent years, a method of utilizing polarized light has been proposed as one of the techniques for aligning liquid crystals without rubbing in the production of liquid crystal substrates. In this method, a thin film such as a polyimide resin is irradiated with polarized light to chemically change the polymer in a specific direction of the thin film to align the orientation, and ultraviolet rays in the vicinity of 365 nm are effective for the orientation. However, in order to apply the above technique to the formation of the alignment film on the liquid crystal substrate, a large polarizing filter is required. That is, when a liquid crystal display device is manufactured, since 4 to 6 liquid crystal display devices are usually formed on one substrate, the size of the substrate to be irradiated with light is usually 550 m.
It is about m × 650 mm. Therefore, the irradiation area of the polarized light used for forming the alignment film of the liquid crystal substrate is 80
0 mm x 800 mm is required. Heretofore, there has been no polarizing element suitable for forming the above-mentioned alignment film on the liquid crystal substrate.

[0003]

As the polarizing element, the polarizing element and the like shown in the following (1) and (2) are known, but the following (1)
The polarizing element of (2) has the following problems and is not preferable when applied to the above-mentioned formation of the alignment film of the liquid crystal substrate. (1) Cube-type polarizing element As shown in FIG. 6, two right-angle prisms exhibiting birefringence are made to face each other with their slant faces facing each other.
There are Taylor polarization prism, Gran Thomson polarization prism, etc.

Since the cube-type polarizing element has a shape shown in FIG. 6, when attempting to polarize a large area of light, the volume of the cube becomes large and the device for mounting it becomes large. Therefore, it is not suitable for forming the alignment film of the liquid crystal substrate which requires a large irradiation area. In the Glan-Taylor polarizing prism and the Glan-Thomson polarizing prism, the light (ordinary ray) that is not emitted from the prism is absorbed by the black polymer that is the mount material provided in the housing. Therefore, when a laser having a power of 2 W or more in continuous oscillation is used, there is a problem that the black polymer is eroded by the ordinary ray and the prism is peeled off.

(2) Polarizing element made of organic film This is a polarizing element having an organic film formed on a substrate. Due to the bonding structure of the molecules constituting the film, only the light of a specific polarization component is transmitted and the light of the remaining components is Absorbed by the membrane. 280nm
When the light in the wavelength region of about 2 μm is polarized, the temperature of the film is 95 ° C. or lower. Membrane temperature is 100 ° C
When it becomes the above, the quality of the film deteriorates and the transmittance decreases. When used for a longer time, the film absorbs light energy and the temperature of the film rises, so that the film cannot be used for a long time. Further, the organic film usually has a large absorption for light having a wavelength of 400 nm or less, and the transmittance is lowered. That is, the polarization efficiency of light in the ultraviolet region is poor.

On the other hand, in order to form the alignment film on the liquid crystal substrate, it is necessary to irradiate the substrate surface with relatively strong light energy.
Further, it is desirable that the wavelength range is ultraviolet light having a wavelength of about 365 nm as described above. Therefore, the polarizing element made of the organic film cannot satisfy the conditions required for forming the alignment film of the liquid crystal substrate. The present invention has been made in view of the above circumstances, and the purpose thereof is to:
A filter that polarizes light in a specific wavelength range that can polarize light with a large irradiation area. It has high heat resistance, its transmittance does not change due to heat, and it is used for a long time in areas where light energy is strong. In addition, it is possible to provide a polarization filter that does not make the device to which the polarization filter is applied extremely large.

[0007]

When a thin film is vapor-deposited on a substrate, as shown in FIG. 7 (a), a transparent substrate is arranged vertically with respect to the direction in which vapor deposition particles fly, and the film is vapor-deposited. ,
Light incident in a direction perpendicular to this film has the same refractive index in any direction (this is called an isotropic film). On the other hand, as shown in FIG. 7B, when a transparent substrate is arranged so as to be inclined with respect to the direction in which vapor deposition particles fly, and a film is vapor-deposited, the film having a columnar structure as shown in FIG. Grows. This columnar structure is dense in a direction orthogonal to a plane formed by the direction of vapor deposition particles and a normal line of the substrate (hereinafter, this direction is referred to as x direction), parallel to the substrate, and orthogonal to the x direction. (Hereinafter, this direction is referred to as the y direction). Therefore, the deposited film has an x-direction and a y-direction.
It has a different refractive index depending on the direction and has optical anisotropy (a method of depositing a film on a substrate by arranging the substrate with respect to the direction in which vapor deposition particles fly is called "oblique evaporation method"). ).

When light is incident on the film having optical anisotropy as described above, the phase shifts depending on the vibration direction of the electric field of light. A film having the above optical anisotropy utilizing this property,
Conventionally, it has been used as a quarter wave plate, a half wave plate, etc. as an optical phase plate. Here, the refractive index in the x direction is nx,
Assuming that the refractive index in the y direction is ny and | nx−ny | = Δn, “Δn × physical thickness of film” is 1 of the wavelength of incident light.
When it is / 4, it becomes a quarter-wave plate, and when it is 1/2 the wavelength of the incident light, it becomes a half-wave plate (for the above-mentioned oblique deposition method and optical retardation plate, see “Surface Technology” Vol. , No.7,19
95, P32-P35).

The present invention comprises a filter that polarizes light in a specific wavelength range by the above oblique vapor deposition method, and paying attention to the point that a film having optical anisotropy can be formed by the oblique vapor deposition method, 1/4 of the optical thickness and the film having optical anisotropy and the film having isotropic property are alternately laminated in a multilayer as shown in FIG. A filter that polarizes. The optical thickness is “physical thickness of film × refractive index”. Here, when the vapor deposition film is formed by the oblique vapor deposition method, the thickness of the anisotropic film has a slope shape in which one end is thicker than the other end. However, in the present invention, as shown in FIG. The optical thickness (1/4 of the wavelength at which polarization is desired) is defined by the thickness of the central portion of the isotropic film.

The multilayer film formed as described above has no difference in the refractive index between the layers with respect to the light whose electric field oscillates in the x direction, and acts as a single film having a predetermined refractive index. For light in which the electric field oscillates in the y direction orthogonal to the direction, the film acts as a multilayer film in which films having different refractive indexes are alternately laminated. Therefore, when light of a predetermined wavelength to be polarized (light having a wavelength of ¼ of the optical thickness of the film) is incident on the multilayer film formed in this way, FIG. 1 (b) (c) As shown in, the light whose electric field oscillates in the x direction is transmitted, but y
Since the refractive index of each layer is different with respect to the light whose electric field oscillates in the direction, the reflected lights at the interfaces of the respective layers interfere with each other to strengthen each other and reduce the transmitted light.

This is due to the following characteristics of the optical thin film.
Light is reflected at the interfaces having different refractive indexes. Here, when light of wavelength λ is incident on a film having an optical thickness of ¼ of wavelength λ, assuming that the phase of the incident light at the light incident side interface of the film is 0 °, the incident light is The phase is 180 ° when the light is reflected at the interface on the side opposite to the light incident side of the film and reaches the interface on the light incident side again. On the other hand, at the interface between the low refractive index layer and the high refractive index layer, when the light incident from the low refractive index layer side is reflected, the phase of the reflected light at the interface is relative to the phase of the incident light at the interface, Inversion (180 ° out of phase)
Happens. That is, the phase of the incident light at the interface is 0
When the angle is °, the phase of the reflected light at the interface becomes 180 °. Therefore, when the refractive index for the wavelength λ of the adjacent medium of the film having the optical thickness of ¼ of the wavelength λ is lower than the refractive index for the wavelength λ of the film, that is, on the light incident side of the film. When the interface is the interface from the low refractive index layer to the high refractive index layer, and the interface on the side opposite to the light incident side of the film is the interface from the high refractive index layer to the low refractive index layer, the light incident on the film When the phase of the incident light at the side interface is 0 °, the phase of the reflected light reflected at the interface is 180 °. On the other hand, the phase when the incident light is reflected at the interface on the side opposite to the light incident side of the film and reaches the interface on the light incident side again is 1
It will be 80 °. Therefore, the phase of the reflected light at the interface on the light incident side of the film and the phase of the reflected light at the interface on the opposite side of the light incident side of the film match. (For the characteristics of optical thin films, see, for example, HAMacleod Original, Shigetaro Ogura and others 3
Name translation, Nikkan Kogyo Shimbun, published November 30, 1989, "Optical thin film", pages 6 to 11, edited by Shiro Fujiwara, Kozo Ishiguro and two others, Kyoritsu Publishing Co., Ltd., published February 25, 1985, See Optical Technology Series 11, "Optical Thin Films," pages 12-15, etc.).

Therefore, when films having different refractive indexes are alternately laminated and light having a wavelength λ at which the electric field oscillates in the y direction is incident on a multilayer film having an optical thickness of ¼ of each wavelength λ, As shown in FIG. 1C, the reflected light at each interface returns in a state where the phases are aligned on the incident surface of the multilayer film, and these components are recombined so as to strengthen each other. Therefore, when the number of layers increases, a large amount of reflected light of the same phase is reflected, the intensity of the reflected light becomes strong, and the intensity of the transmitted light becomes correspondingly weak. However, this multilayer film transmits light having a wavelength other than the predetermined wavelength λ regardless of the x direction and the y direction. As the material for forming the deposited film, tantalum pentoxide (Ta ₂ O ₅ ), hafnium dioxide (HfO ₂ ),
Tungsten trioxide (WO ₃ ), cerium dioxide (Ce)
O ₂ ), zirconium dioxide (ZrO ₂ ) and the like can be used.

According to the first and second aspects of the present invention,
As described above, the first film having a constant film thickness and the second film having a different film thickness in a slope are alternately deposited to form a multilayer film.
And the optical thickness of each film in the approximate center of the filter.
The optical anisotropy so that the wavelength becomes 1/4 of the specific wavelength of light.
Alternating layers of films with isotropic films
The slope of the two second membranes adjacent to the first membrane
The directions are opposite, and there is no difference in the refractive index between layers for light whose electric field oscillates in the x direction, and for light whose electric field oscillates in the y direction that is orthogonal to the x direction, the refractive index differs. Since a filter that polarizes light in the wavelength range of 1 is configured, a polarizing element having an arbitrary size according to the irradiation area can be made by preparing necessary vapor deposition equipment. Moreover, since the polarizing element can be configured by the flat plate, the applied device does not become large. Further, since the multilayer film is formed by the vapor deposition film, it has high heat resistance and does not deteriorate optical characteristics such as transmittance due to heat, and can be used in a region where light energy is strong. Furthermore, since it is formed of a vapor deposition film, it is possible to polarize light in the ultraviolet region (240 nm to 400 nm).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (1) Formation of Vapor Deposition Film FIG. 2 is a diagram for explaining a method for forming a vapor deposition film according to the present invention, in which 1 is a transparent substrate for forming a multilayer film,
Reference numeral 2 is a vapor deposition source that emits vapor deposition particles, and a filter that polarizes light in a specific wavelength range is manufactured as follows. (a) As shown in (a) of the same figure, the transparent substrate 1 is inclined (inclination angle: + α) with respect to the direction in which vapor-deposited particles fly, and the optical thickness is 1/4 of the wavelength to be polarized. A film of (physical thickness x refractive index) is deposited. The film thus deposited has the property of optical anisotropy as described above. When the oblique vapor deposition is performed as described above, the vapor deposition film on the substrate becomes thicker near the vapor deposition source and thinner at the farther away, as described above.

(B) As shown in FIG. 1B, the transparent substrate 1 on which an anisotropic film is vapor-deposited is arranged perpendicularly to the direction in which vapor-deposited particles fly, and the wavelength of the desired wavelength of 1 is obtained. Deposit / 4 optical thickness film. The film deposited in this manner has the optical isotropic property as described above. (c) As shown in FIG. 7C, the transparent substrate 1 on which the isotropic film is formed is arranged at an angle (tilt angle: −α) with respect to the direction in which the vapor deposition particles fly, and polarized. 1/4 of desired wavelength
Deposit a film with an optical thickness of. (d) In the same manner as in (b) above, a film having an optically isotropic property is formed. (e) The processes (a) to (d) are repeated to form a multilayer film in which an optically anisotropic film and an optically isotropic film are alternately deposited.

During oblique vapor deposition, the thickness of the vapor deposition film becomes thicker near the vapor deposition source and thinner at the farther away as described above. Therefore, if the substrate is tilted in the same direction, the thickness of the multilayer film produced will be It will be different at both ends, resulting in a shift in the reflection band at both ends of the film. Although the width of the reflection band does not change, the entire reflection band moves in parallel to the long wavelength region or the short wavelength region. The width of the reflection band is defined by the width W of the wavelength at the transmittance between the maximum value Tmax and the minimum value Tmin of the transmittance, as shown in FIG. 4 described later. So, as mentioned above,
After the substrate 1 is obliquely vapor-deposited at an angle α with respect to the direction in which the vapor deposition particles fly, vapor deposition is performed with the substrate 1 perpendicular to the direction in which the vapor deposition particles fly, and then the substrate 1 is placed in the direction in which the vapor deposition particles fly. -Slant vapor deposition with a tilt. By performing the vapor deposition as described above, a multilayer film as shown in FIG. 3 is formed, and the thickness of both ends of the created multilayer film becomes the same.

The angle α at which the substrate is tilted during oblique deposition
Is determined based on the magnitude of Δn [= (refractive index nx in x direction)-(refractive index in y direction is ny)].
The larger Δn is, the wider the reflection band is, and the higher the reflection efficiency can be obtained with a smaller number of layers, which is advantageous in optical characteristics. 2 tantalum pentoxide (Ta
_In the case of a ₂ O ₅ ) film, it has been confirmed by experiments that the angle of inclination is about 70 ° to obtain a large Δn.

When light having a wavelength of 4 times the optical thickness of the film is incident on the multilayer film formed as described above, as described above, light whose electric field oscillates in the x direction is transmitted, but y As for the light whose electric field oscillates in the direction, the transmitted light is reduced because the refractive index of each layer is different, and it functions as a polarizing element for the light of a specific wavelength range. When forming the above vapor deposition film, the same vapor deposition material is used to repeat the above (a) oblique vapor deposition, → (b) ordinary vapor deposition → (c) diagonal vapor deposition → (d) ordinary vapor deposition. A multi-layer film may be formed, or the x direction of the formed film, y
If the respective refractive indexes in the directions are the same, the same effect can be obtained even if vapor deposition is performed using a plurality of substances.

(2) Specific Example The following multilayer film was prepared by the method described above.・ Evaporated film: 2 tantalum pentoxide (Ta ₂ O ₅ ). ・ Optical thickness of one layer: 100 μm, number of layers: 31 layers ・ Refractive index (ny) in y direction of anisotropic film: 1.59 (wavelength 397 nm) X) Refractive index (nx) of anisotropic film and isotropic film: 1.72 (at wavelength of 396 nm) FIG. 4 shows the transmittance of the above multilayer film in x and y directions. As shown in the figure, it was possible to form a multilayer film that transmits only the light of which the electric field oscillates in the x direction out of the light of 400 nm. By irradiating the multilayer film with light including ultraviolet rays, polarized light having a predetermined wavelength could be obtained in a wavelength region of 400 nm or less.

(3) Application Example FIG. 5 is a diagram showing an example of the configuration of a polarized light irradiation device using a polarizing filter formed of the multilayer film of the present invention. As shown in the figure, the polarized light irradiation device includes a discharge lamp 11 such as an ultra-high pressure mercury lamp, an elliptical focusing mirror 12, and a first plane mirror 1.
3, the integrator lens 15, the shutter 14, and the second
The flat mirror 16, the collimator lens 17, the filter 18 for transmitting light of a specific wavelength, and the polarization filter 19 formed of the above-mentioned multilayer film.

In FIG. 1, light including ultraviolet light emitted from the discharge lamp 11 is condensed by the elliptical condenser mirror 12, reflected by the first plane mirror 13, and incident on the integrator lens 15 through the shutter 14. . Integrator lens 15
The light emitted from the second plane mirror 16 is further reflected by the second plane mirror 16, collimated by the collimator lens 17, and incident on the polarization filter 19 via the filter 19 that transmits light of a specific wavelength. As described above, the polarization filter 19 transmits only the light whose electric field oscillates in the x direction and reduces the transmitted light of the light whose electric field oscillates in the y direction with respect to the light in the specific wavelength range. Therefore, of the light in the specific wavelength range that has passed through the filter 18, only the light whose electric field oscillates in the x direction passes through the polarization filter 19 and is applied to the work W such as the liquid crystal substrate via the mask M. . Reference numeral 20 is an alignment microscope for performing the alignment between the mask M and the work W described above, and 2
1 is a work stage, work stage 21 is X,
The work stage 21 is movable in Y, Z, and θ directions.
The work is placed on top. The X axis is an axis parallel to the work surface, the Y axis is an axis parallel to the work surface and orthogonal to the X axis, the Z axis is an axis orthogonal to the X and Y axes, and θ is rotation about the Z axis. .

Next, the photo-alignment treatment of the alignment film of the liquid crystal display element using the polarized light irradiation device shown in FIG. 5 will be described.
The entire surface of the thin film of the liquid crystal substrate can be optically aligned by irradiating the entire surface of the thin film of the liquid crystal substrate with polarized light as described below. (a) In FIG. 5, the work W is placed on the work stage 21. The mask M is not used when the entire surface of the substrate is irradiated with polarized light. Alternatively, a mask M that transmits light only in the thin film portion of the liquid crystal substrate may be used. (b) The work stage 21 is rotated around the Z axis so that the polarization direction is oriented in a predetermined direction with respect to the work W.
When the mask M is used, the mask M is set on a mask stage (not shown), and the alignment marks of the mask M and the work W are observed with an alignment microscope.
The work stage 21 is driven in the X, Y, and θ directions to align the mask M and the work W so that the alignment marks of the mask M and the work W match. In this case, the mask M may be set in advance so that the orientation thereof matches the polarization direction.

(C) The shutter 14 is opened and the work W is irradiated with polarized light for a predetermined time. In the above description, the case where polarized light is irradiated to the entire surface of the thin film of the liquid crystal substrate has been described. However, polarized light is radiated through a mask to a part of the liquid crystal substrate where the alignment film has already been formed by rubbing or optical alignment. The orientation characteristics can be changed by irradiation.

[0024]

As described above, in the present invention, a first film having a constant film thickness and a second film having a different film thickness in a slope form are alternately deposited to form a multilayer film, And
The optical thickness of each film near the center of the filter
A film with optical anisotropy to be 1/4 of the wavelength of
The first film described above is formed by alternately stacking multi-layered films having multiple directions.
The direction of the slope of the two second membranes adjacent to
However, for light whose electric field oscillates in the x direction, there is no difference in the refractive index between the layers, and for light whose electric field oscillates in the y direction that is orthogonal to the x direction, the refractive index is different. Since the filter that polarizes the light is configured, the following effects can be obtained. (1) If the required vapor deposition equipment is prepared, a polarizing element having an arbitrary size according to the irradiation area can be manufactured. Moreover, since the polarizing element can be configured by the flat plate, the applied device does not become large. (2) Since the multilayer film is formed by the vapor deposition film, the heat resistance is high, the optical characteristics such as transmittance are not deteriorated by heat, and it can be used in a region where light energy is strong. (3) Since the polarizing element is formed of a vapor deposition film, it is possible to polarize light in the ultraviolet region (240 nm to 400 nm).

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a polarizing element and its action in the present invention.

FIG. 2 is a diagram illustrating a method for forming a vapor deposition film according to the present invention.

FIG. 3 is a diagram illustrating a relationship between a tilt of a substrate and a film thickness to be deposited.

FIG. 4 is a diagram showing characteristics of a polarizing element of an example of the present invention.

FIG. 5 is a diagram showing an example of a configuration of a polarized light irradiation device using the polarizing element of the present invention.

FIG. 6 is a diagram showing a configuration of a cube-type polarizing element.

FIG. 7 is a diagram illustrating an oblique vapor deposition method.

FIG. 8 is a diagram illustrating a columnar structure formed by an oblique vapor deposition method.

[Explanation of symbols]

1 transparent substrate 2 evaporation source 11 discharge lamp 12 Elliptical focusing mirror 13 First plane mirror 14 Shutter 15 Integrator lens 16 Second plane mirror 17 Collimator lens 18 filters 19 Polarizing element 20 Alignment microscope 21 work stage M mask W work W

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-49924 (JP, A) JP-A-8-227014 (JP, A) JP-A-10-81955 (JP, A) JP-A-9- 166710 (JP, A) JP 59-97105 (JP, A) JP 57-179807 (JP, A) JP 63-132203 (JP, A) US 3610729 (US, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 5/30 G02B 5/28

Claims (2)

(57) [Claims] 1. A filter for polarizing light in a specific wavelength range, which is formed by depositing films in multiple layers on a substrate, wherein the multilayer film includes a first film having a constant film thickness and a sloped film thickness. And a second film having different anisotropy, and a film having optical anisotropy so that the optical thickness of each film in the substantially central portion of the filter is ¼ of a specific light wavelength. , Isotropic
Of the second film adjacent to the first film are diametrically opposite to each other, and the multi-layer film has a structure in which an electric field vibrates in the x direction. Is a polarizing filter characterized in that there is no difference in the refractive index between the layers, and the refractive index is different for light whose electric field oscillates in the y direction orthogonal to the x direction. 2. The polarizing filter according to claim 1 , wherein the second film is formed by an oblique vapor deposition method.