JP2010060621A - Polarizing element and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polarizing element, which can easily obtain a polarizing element with a large area in which the distribution of the spectral characteristics in the plane is uniform and which has high reliability in a short time, and to provide a polarizing element produced with the method for producing a polarizing element. <P>SOLUTION: The method for producing the polarizing element comprises: a photolithography step where a resist layer 13a is formed on either main face of a substrate 11a (c) transparent to visible light and in which a pair of confronted edge faces are respectively made into slopes where the other main face overflows to either main face, and ultraviolet light is made incident so as to be oblique to the surface of the resist layer 13a and also in such a manner that the incident optical flux face including the light flux of the ultraviolet light is made vertical to the faces made into the slopes, thus interference exposure (d) and development (e) are performed regarding the resist layer 13a; an etching step (f) where either main face side of the substrate 11a is subjected to etching to form a diffraction grating-shaped concavo-convex part 14 on either main face; and an inorganic fine particle layer-forming step (g) where an inorganic fine particle layer 15 is formed on the top or one side face part of the convex part in the concavo-convex part 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a manufacturing method of an inorganic absorption type polarizing element and a polarizing element manufactured by the manufacturing method of the polarizing element.

  In a liquid crystal display device (particularly a transmissive liquid crystal display device), it is indispensable to dispose a polarizing element (polarizing plate) on the surface of the liquid crystal panel from the principle of image formation. The function of the polarizing plate is to absorb one of the orthogonally polarized components (so-called P-polarized wave and S-polarized wave) and transmit the other. As such a polarizing plate, conventionally, a dichroic polarizing plate in which an iodine-based or dye-based high molecular organic substance is contained in a film is often used.

  As these general production methods, a method is used in which a polyvinyl alcohol film and a dichroic material such as iodine are dyed, followed by crosslinking using a crosslinking agent and uniaxial stretching. Since this is produced by stretching, this type of polarizing plate generally tends to shrink. In addition, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed under heating and humidification conditions. Moreover, since the film is fundamentally used, the mechanical strength as a device is weak. In order to avoid this, a method of adhering a transparent protective film may be used.

  In recent years, the use of liquid crystal display devices has expanded and their functions have increased, and accordingly, high reliability and durability have been required for individual devices constituting the liquid crystal display device. For example, in the case of a liquid crystal display device using a light source with a large amount of light such as a transmissive liquid crystal projector, the polarizing plate receives strong radiation. Therefore, excellent heat resistance is required for the polarizing plate used in these. However, since the film-based polarizing plate as described above is an organic substance, there is a limit in improving these characteristics.

  In response to this problem, Corning Corporation in the United States sells a highly heat-resistant inorganic polarizing plate under the name Polarcor. This polarizing plate has a structure in which silver fine particles are diffused in glass, and does not use an organic substance such as a film, and its principle uses plasma resonance of island-like fine particles. That is, light absorption by surface plasma resonance when light is incident on noble metal or transition metal island-like particles is used, and the absorption wavelength is affected by the particle shape and the surrounding dielectric constant. Here, when the shape of the island-shaped fine particles is elliptical, the resonance wavelengths in the major axis direction and the minor axis direction are different, and thereby deflection characteristics are obtained. Specifically, a polarization component parallel to the major axis on the long wavelength side is obtained. A polarization characteristic of absorbing and transmitting a polarization component parallel to the minor axis is obtained. However, in the case of Polarcor, the wavelength range in which the polarization characteristics can be obtained is a region close to the infrared region, and does not cover the visible light range required for a liquid crystal display device. This is due to the physical properties of silver used in the island-shaped fine particles.

  Here, in order to function as a polarizing plate, the shape anisotropy of the metal fine particles used as a polarizer is extremely important. Patent Document 1 discloses several methods for producing a polarizing plate using aluminum fine particles. Among them, glass based on silicate is undesirable as a substrate because aluminum and glass react. Calcium aluminoborate glasses are described as suitable (paragraphs 0018, 0019). However, glass using silicate is widely distributed as optical glass, and it is economically unfavorable that a highly reliable product can be obtained at a low cost and this is not suitable. Further, a method for forming island-like particles by etching a resist pattern is described (paragraphs 0037 and 0038). Usually, a polarizing plate used in a liquid crystal projector needs to have a size of about several centimeters and a high extinction ratio. Therefore, for the purpose of a visible light polarizing plate, the resist pattern size needs to be sufficiently shorter than the visible light wavelength, that is, several tens of nanometers. In order to obtain a high extinction ratio, it is necessary to form a pattern with high density. Further, when used for a liquid crystal projector, a large area is required. However, in the method of applying high-density fine pattern formation by lithography as described herein, it is necessary to use electron beam drawing or the like in order to obtain such a pattern. Electron beam drawing is a method of drawing individual patterns from an electron beam, and is not practical because of poor productivity.

  Therefore, Patent Document 2 uses a quartz substrate having higher heat dissipation than glass, and has a large area with excellent heat dissipation characteristics by a nanoimprint method in which a mold is pressed against a resist layer on the substrate and the unevenness of the mold is transferred to the resist layer. Thus, there has been proposed a method for manufacturing a polarizing element capable of obtaining a polarizing element having a uniform in-plane spectral characteristic distribution and high reliability.

  However, the nanoimprint method has a problem that it requires time to prepare a mold corresponding to the target polarizing element and is expensive as equipment.

JP 2000-147253 A JP 2008-158460 A

  The present invention has been made in view of the above problems in the prior art, and is a polarizing element capable of easily obtaining a large-area polarizing element with a uniform in-plane spectral characteristic distribution and high reliability in a short time. It aims at providing a manufacturing method, and also aims at providing the polarizing element manufactured with the manufacturing method of this polarizing element.

  The present invention provided to solve the above problems is a substrate (substrate 11a) which is transparent to visible light and has a pair of opposed end faces each having an inclined surface such that the other main surface protrudes from one main surface. ) Is used to form a resist layer (resist layer 13a) on one main surface of the substrate (FIG. 3 (c)), and then the ultraviolet light is oblique to the resist layer surface and the ultraviolet light. The resist layer is subjected to interference exposure (FIG. 3 (d)) and development (FIG. 3 (e)) so that the incident light beam surface including the light beam is perpendicular to the inclined end surface. A photolithography process for patterning a layer, and an etching process for etching one main surface side of the substrate to form a diffraction grating-shaped unevenness (uneven portion 14) on the one main surface (FIG. 3F) ) And the convex and concave parts (convex part 14a) Top or inorganic particle layer on one side surface of the inorganic fine particle layer forming step of forming a (inorganic fine particle layer 15) (FIG. 3 (g)), a method of manufacturing a polarizing element having a (FIG. 3, FIG. 4).

Here, it is preferable that the angle φ formed by the inclined surface of the end surface with the vertical surface of the main surface of the substrate is in the relationship of the following formula (1).
φ> sin ⁻¹ (sin θ / n) (1)
(Θ: angle of incidence of ultraviolet light on the resist layer in the photolithography process, n: refractive index of the substrate with respect to the ultraviolet light)
A layer that absorbs the ultraviolet light may be formed on the slope.

  Further, an antireflection film forming step for forming an antireflection film having an antireflection function on visible light incident on the other main surface of the substrate perpendicularly to the main surface of the substrate and ultraviolet light incident obliquely. It is preferable to have (FIG. 3B).

  In addition, the present invention provided to solve the above-described problems uses a substrate that is transparent to visible light and has a pair of opposed end faces each having a slope such that the other principal surface protrudes from one principal surface. Then, a resist layer is formed on one main surface of the substrate, and then ultraviolet light is inclined with respect to the resist layer surface, and an incident light beam surface including a light beam of the ultraviolet light is on the inclined end surface. The resist layer is subjected to interference exposure and development, and the resist layer is patterned, and one main surface side of the substrate is etched to form the resist layer on the one main surface. It is manufactured by a method for manufacturing a polarizing element, comprising: an etching step for forming a diffraction grating-shaped unevenness; and an inorganic fine particle layer forming step for forming an inorganic fine particle layer on the top or one side surface of the convex portion of the unevenness. A polarizing element.

According to the method for manufacturing a polarizing element of the present invention, a polarizing element having a large area can be easily manufactured in a short time by using a photolithography technique. In addition, since the end face of the substrate is sloped, ultraviolet light is prevented from being exposed again to the resist layer in the photolithography process, so that the uneven diffraction grating shape formed on the substrate is made uniform and in-plane spectral characteristics are obtained. The distribution can be made uniform. Furthermore, the antireflection film on the back side of the substrate prevents reflection of ultraviolet light transmitted from the front surface side (resist layer side) to the back side of the substrate, so that the ultraviolet light exposes the resist layer again. Therefore, the uneven diffraction grating shape formed on the substrate can be made uniform, and the in-plane spectral characteristic distribution can be made more uniform. Furthermore, the antireflection film can also function as an antireflection film for visible light in the polarizing element.
In addition, according to the polarizing element of the present invention, the end face having the inclined surface as described above prevents the ultraviolet light from becoming stray light in the photolithography process, so that the in-plane spectral characteristic distribution is uniform and highly reliable. A polarizing element can be provided.

  As described above, a manufacturing method using a photolithography technique can be considered as a manufacturing method of the polarizing element instead of the conventional nanoimprint method. In that case, possible manufacturing processes are, for example, (resist application) → (interference exposure) → (development) → (etching (unevenness formation)) → (inorganic fine particle layer formation) → (antireflection film formation).

  Here, when the visible light region is set to 430 nm to 730 nm, when the period of the wire grid of the inorganic fine particle layer in the polarizing element, that is, the pitch of the one-dimensional lattice-shaped unevenness formed on the substrate is at least 200 nm or less. Can be expected.

  Therefore, in the photolithography technique, it is necessary to form an interference fringe having such a pitch with ultraviolet light and pattern the resist layer by interference exposure. Specifically, using a YAG quadruple wave solid-state laser of 266 nm as a light source, two lights with an incident angle of ± 64 ° with respect to the substrate are incident, and interference fringes with a pitch of about 150 nm are formed on the substrate (resist layer). It is what you create on top.

  By the way, as a substrate material of a polarizing element, since heat dissipation characteristics are required as described above, it is necessary that the thermal conductivity is high, and quartz or quartz is mainly used. These materials do not absorb ultraviolet light and exhibit high transmittance. Therefore, when the substrate is irradiated with ultraviolet light to obtain interference fringes as described above, the substrate is transmitted through the substrate, and the light becomes stray light.

There are the following two main stray light caused by such a substrate, and it is necessary to examine countermeasures independently.
(1) Scattered light on the substrate end surface (2) Reflected light on the back surface of the substrate

Here, the scattered light at the substrate end face is examined.
FIG. 1 shows a state where interference exposure is performed on a general substrate. In the interference exposure, two ultraviolet light beams L ₁ and L ₂ having a deep incident angle are used, but the cross-sectional area of scattering at the end surface (end surface A) parallel to the incident light beam surface including the light beam is small, and the incident light beam surface The cross-sectional area of scattering is large on the plane perpendicular to (B end face). Therefore, an end surface (B end surface) perpendicular to the incident light beam surface mainly including the light beams L ₁ and L ₂ becomes a problem.

On the B end face, as shown in FIG. 2, the following two scattered lights become stray light.
(Stray light 1) Light entering from the air side of the B end face and entering the substrate.
(Stray light 2) Light that enters from the front surface of the substrate (front surface, resist layer forming surface), passes through the inside of the substrate, and further reflects on the B end surface.

  In general, the end face is often a sand-printed surface or a surface obtained by cutting the substrate, and is not an optical surface. Therefore, when light is incident on this surface, random coherent scattering, so-called speckle, is generated. The intensity of speckle can be many times the amount of incident light when viewed in a narrow place, and the influence on patterning quality is great. Further, the degree of scattering on the sand-printed surface depends on the surface roughness and the wavelength, but in many cases, the scattered light intensity is larger in the reflection than in the transmission. Therefore, the influence of stray light 2 is more problematic than stray light 1.

  As described above, the inventors focused on the reflection / scattering state of the end face of the substrate in the interference exposure, and conducted intensive studies to arrive at the present invention. Hereinafter, a method for manufacturing a polarizing element according to the present invention will be described with reference to the drawings. The present invention will be described with reference to the embodiment shown in the drawings, but the present invention is not limited to this, and can be appropriately changed according to the embodiment. -As long as an effect is produced, it is included in the scope of the present invention.

  The method for manufacturing a polarizing element according to the present invention uses a substrate that is transparent to visible light and has a pair of opposed end faces each having a slope that protrudes from one main surface to the other main surface. A resist layer is formed on one main surface of the substrate, and then ultraviolet light is inclined with respect to the resist layer surface, and an incident light beam surface including a light beam of the ultraviolet light is perpendicular to the end surface as the inclined surface. The resist layer is subjected to interference exposure and development, and the resist layer is patterned, and one main surface side of the substrate is etched to form a diffraction grating shape on the one main surface. And an etching step for forming the irregularities, and an inorganic fine particle layer forming step for forming an inorganic fine particle layer on the top or one side of the convex portions of the irregularities.

The manufacturing method of the polarizing element of this invention is demonstrated based on the schematic which shows the manufacturing process of the polarizing element which concerns on this invention of FIG.
(S11) A substrate 11a transparent to visible light is prepared as an original plate (FIG. 3A). Here, the substrate 11a is made of quartz or quartz. For example, a high-purity quartz substrate having a crystal structure, and an optical artificial quartz substrate may be used.

FIG. 4 shows the shape of the substrate used in the present invention. 4A is a perspective view of the substrate 11a, and FIG. 4B is a cross-sectional view of the substrate 11a viewed from the direction of the arrow in FIG. 4A.
In the substrate 11a, the main surfaces St and Sb are rectangular, and one of the main surfaces St is subjected to a predetermined process (a photolithography process, an etching process, etc.) to form an inorganic fine particle layer having a wire grid structure as described later. The front face to be done. That is, the main surface St is a surface on which the resist layer 13a is formed, a surface on which ultraviolet light for interference exposure is obliquely incident, and a surface on which the uneven portion 14 is formed by etching. The other main surface Sb is a back surface on which the antireflection film 12 is formed as necessary.

  Further, each of the opposing pair of end surfaces t1 and t2 of the substrate 11a is a slope such that the other main surface Sb protrudes in the X direction with respect to the one main surface St. At this time, the length of the main surface Sb protruding in the X direction from the main surface St is the same on each of the end surfaces t1 and t2. That is, when it becomes the polarizing element 10 of this invention, the cross-sectional shape of the direction (X direction) perpendicular | vertical to a polarization direction is a trapezoid which makes a polarizing surface (front surface) side a short side. (FIG. 4B). The lengths of the main surfaces St and Sb in the Y direction perpendicular to the X direction are the same, and the other pair of end surfaces t3 and t4 are surfaces perpendicular to the main surfaces St and Sb.

By setting it as the shape of such a board | substrate 11a, the bad influence of the stray light in an end surface can be suppressed in the interference exposure performed at a post process. FIG. 5 shows a preferred configuration thereof.
FIG. 5 is an enlarged cross section of the end face t1 (or t2). At this time, the angle φ formed by the inclined surfaces of the end surfaces t1 and t2 and the vertical surface of the substrate main surface St (conventional vertical end surface) is preferably in the relationship of the following formula (1).
φ> sin ⁻¹ (sin θ / n) (1)
(Θ: angle of incidence of ultraviolet light on the resist layer 13a (substrate 11a) in the photolithography process, n: refractive index of the substrate 11a with respect to the ultraviolet light)

  The substrate 11a is manufactured by being cut by machining, but it is only necessary that the end surfaces t1 and t2 be formed in a chamfering process that is always performed thereafter.

  Thereby, the stray light 1 incident on the end surface t1 (or t2) is scattered in the substrate 11a, but is mainly scattered on the back surface Sb side of the substrate 11a, and the stray light reaching the front surface St is reduced. Further, the stray light 2 incident on the resist layer 13a reaches the back surface Sb of the substrate 11a without being scattered by the end surface t1 (or t2) of the substrate 11a. Thereby, it can suppress that ultraviolet light becomes stray light and exposes the resist layer 13a again. For example, when the substrate 11a is a quartz substrate and θ = 64 °, if φ = 45 °, the equation (1) is satisfied and the problem of stray light does not occur.

(S12) Next, the antireflection film 12 is formed on the other main surface (back surface) Sb of the substrate 11a (FIG. 3B).

  As described above, during interference exposure in the photolithography process, (2) there is a problem that reflected light on the back surface of the substrate becomes stray light. That is, since the reflectance of the ultraviolet light on the surface of the quartz or quartz substrate exceeds 20%, the ultraviolet light transmitted through the substrate 11a is reflected on the back surface Sb side (interface between the substrate and air) of the substrate 11a. This ultraviolet light which became the stray light again exposed the resist layer 13a. As a result, the desired patterning cannot be obtained because the desired patterning cannot be performed. In order to prevent such a problem from occurring, it was necessary to set the stray light intensity to 1% or less as a standard.

  Further, since an antireflection film is finally provided on the back surface side of the conventional polarizing element, an antireflection film is formed in advance on the other surface (back surface) Sb of the substrate 11a before the resist coating. It is possible. However, this antireflection film only has an antireflection function for visible light required when the polarizing element is incorporated as a component of a liquid crystal projector. That is, since such an antireflection film does not consider the reflectivity with respect to ultraviolet light (for example, light with a wavelength of 266 nm) and has a high reflectivity, it reflects more ultraviolet light than the state of the substrate. Therefore, the ultraviolet light transmitted through the substrate at the time of exposure in the photolithography process is reflected by the antireflection film and again exposes the resist layer, which has a great adverse effect on the characteristics of the polarizing element. .

  Therefore, in the present invention, the antireflection film 12 has an antireflection function with respect to visible light incident on the resist layer 13a (main surface St of the substrate 11a) and ultraviolet light incident obliquely.

Here, the visible light incident perpendicularly to the main surface of the substrate 11a refers to light incident from a light source when incorporated in a projector (for example, a liquid crystal projector (described later)) as a polarizing element. The wavelength range of the light is, for example, 430 to 730 nm. Alternatively, the wavelength range may be any of red light L _R , green light L _G , and blue light L _B used as a light source. For example, if the wavelength range of the red light _{L R,} depending on the liquid crystal projector specification is 730nm from 650 nm. The antireflection film 12 is required to transmit the light source light so as not to be attenuated as much as possible (no reflection or absorption).

  Further, the ultraviolet light obliquely incident on the resist layer 13a (the main surface St of the substrate 11a) means that from the front side of the substrate 11a during interference exposure in the photolithography process (described later) of the manufacturing process of the polarizing element. This refers to ultraviolet light incident at a predetermined angle. The ultraviolet light is s-polarized light, and its wavelength corresponds to the wavelength of a laser used as an exposure light source (193 nm for ArF excimer laser, 248 nm for KrF excimer laser). The antireflection film 12 is required not to reflect the ultraviolet light transmitted through the substrate 11a as much as possible.

  The antireflection film 12 is an optical laminated film in which a plurality of optical films having different refractive indexes are laminated. At this time, the optical film has one or a plurality of types as a high refractive index optical film (for example, a refractive index of 1.70 to 2.40), and a low refractive index having a refractive index smaller than that of the high refractive index optical film. An optical film having a refractive index (for example, a refractive index of 1.30 to 1.69) is composed of one type or a plurality of types.

Each of the optical films is made of a transparent (absorptive) material from the visible to the ultraviolet region. Alternatively, it is possible to use a material that is transparent in the visible region and absorbs in the ultraviolet region. In that case, the uppermost layer of the optical laminated film may be an optical film made of a material that absorbs in the ultraviolet region.
The optical film may be formed by a dry process such as vapor deposition or coating.

  In addition, by adjusting the refractive index and thickness of each optical film, or the laminated structure, it is possible to shift and adjust the wavelength position where the light is transmitted as the anti-reflection film 12, and as a result, it is incident obliquely as interference exposure. An optical multilayer film corresponding to the wavelength of the ultraviolet light and the wavelength of visible light projected from the liquid crystal projector can be obtained. As a design method of the optical multilayer film as such an antireflection film 12, a conventionally known one may be used. For example, assuming that there is no film absorption of light in these wavelength regions, the reflectance is designed to be the lowest in each wavelength region.

FIG. 6 shows a configuration example of the antireflection film 12. An optical multilayer film composed of 18 layers is formed on a substrate 11 made of quartz by combining optical films composed of four types of materials, and the antireflection film 12 is formed. Specifically, the four types of materials are: Substance M2 (product for vapor deposition manufactured by Merck & Co., Inc .; refractive index at wavelength 266 nm = 1.8041, material name H ₁ ), TiO ₂ (refractive index at wavelength 266 nm = 2. 387, material name H ₂ ), SiO ₂ (refractive index at wavelength 266 nm = 1.475, material name L ₁ ), MgF ₂ (refractive index at wavelength 266 nm = 1.3874, material name L ₂ ), Using these materials, the antireflection film 12 having the layer structure shown in Table 1 may be used. Each optical film (optical films m _{1 to} m ₁₈ ) is formed by a sputtering method.

  According to the antireflection film 12 having the configuration shown in Table 1, the reflectance when light in the visible light region (wavelength of 430 nm to 730 nm) is perpendicularly incident is 1% or less. Further, when s-polarized light in the ultraviolet region (wavelength 266 nm) is incident on the substrate 11 at an incident angle of 64 °, the reflectance is 1% or less (design value 0.14%), and the back surface reflection of the substrate during interference exposure Reflectivity without the problem of re-exposure due to. Note that there is no problem of re-exposure due to reflection of the back surface of the substrate during interference exposure even if there is a variation in the incident angle on the substrate 11 such that the incident angle is 64 ° ± 5 °.

  In FIG. 6, in order to provide an antireflection function in all of the three primary color wavelength regions of RGB, a total of 18 layers are formed. However, since a liquid crystal projector uses one sheet for each wavelength of RGB, If the polarizing element is exclusively used for the wavelength region, the number of optical films stacked in the antireflection film 12 can be reduced.

(S13) A resist layer 13a is formed on the main surface (one main surface) St opposite to the surface on which the antireflection film 12 is formed on the substrate 11a (FIG. 3C). The resist layer 13a is made of a photoresist material (photosensitive organic material) corresponding to an exposure light source generally used in photolithography, and can be etched together with the substrate 11a by a reactive gas or an ion beam as will be described later. It is. For example, a resist for KrF manufactured by Tokyo Ohka Co., Ltd. is applied to form a resist layer 13a having a thickness of 200 nm or less. The resist layer 1a is formed after the formation of the antireflection film 12 or simultaneously with the formation of the antireflection film 12.

(S14) The resist layer 13a is subjected to interference exposure to form a photosensitive layer 13b in which the resist layer is exposed to a predetermined pattern (FIG. 3D). At this time, the ultraviolet light is incident obliquely with respect to the surface of the resist layer 13a, and the incident light beam surface including the ultraviolet light beam is incident perpendicular to the end surfaces t1 and t2 which are the inclined surfaces, thereby performing interference exposure. Do. Interference exposure may be performed with an exposure apparatus (stepper) used in the manufacture of semiconductor elements.

7 and 8 show configuration examples of optical systems used for interference exposure.
FIG. 7 shows an optical system called a Lloyd Mirror type, which has a structure of a resist layer 13a / substrate 11a / antireflection film 12, and a target substrate having a principal surface St inclined at a predetermined angle with respect to the optical axis. The mirror disposed adjacent to a position perpendicular to the target substrate is irradiated with diffracted light (s-polarized light) having a wavelength of 266 nm using a YAG fourth harmonic solid-state laser. As a result, diffraction fringes (interference fringes) are formed on the resist layer 13a on the substrate 11a from the diffracted light that is directly incident from the light source side and the diffracted light that is reflected by the mirror and incident, and subjected to interference exposure.

  FIG. 8 shows an optical system called a Mach-Zehnder type, which splits light (s-polarized light) having a wavelength of 266 nm using a YAG quadruple wave solid-state laser into two optical paths, and then resist layer 13a / substrate 11a / reflection. The diffracted light is incident on the target substrate having the structure of the prevention film 12 from two directions to perform interference exposure.

In both the optical systems of FIGS. 7 and 8, interference fringes are formed on the substrate 11a by two-beam interference, and the resist layer 13a is exposed. This is shown in FIG. Here, the exposure light beam L ₁ incident angle + theta with respect to the normal L of the substrate 11a, the resist layer 13a as interference fringes of the pitch p and the light beam L ₂ is incident on the resist layer 13a of the angle of incidence -θ To do.

Note that the relationship shown in the following equation (2) holds between the pitch p and the wavelength λ of the ultraviolet light and the incident angle θ.
p = λ / (2 sin θ) (2)

  Therefore, if the pitch p of the diffraction grating is determined as the polarizing element substrate, the incident angle can be determined based on the equation (2) from the wavelength λ of the exposure light source (ultraviolet light) to be used. The wavelength of ultraviolet light may be in the range of 180 to 300 nm, but is actually determined by the laser light source mounted on the exposure apparatus. For example, in order to form a diffraction grating with a pitch of 150 nm using laser light having a wavelength of 266 nm, the incident angle θ is set to 64 ° from the equation (2).

In the exposure process, for example, in the optical system configured as shown in FIG. 7, after performing interference exposure for 20 seconds at a power of 30 nm / cm ² with a laser (s-polarized light) having a wavelength of 266 nm, post-heating (PEB (PEB ( Post Exposure Bake)).

  A part of the light incident on the resist layer 13a at the time of interference exposure is incident on the end portions on the end surfaces t1 and t2 or on the end surfaces t1 and t2, but the main surface (mainly due to the shape (slope) of the end surfaces t1 and t2. Since there is almost no light scattered on the St side, exposure of the resist layer again by this light is suppressed. Furthermore, since light transmitted through the substrate 11a is hardly reflected on the back surface Sb side of the substrate 11a by the antireflection film 12, exposure of the resist layer again by this light is suppressed.

(S15) The photosensitive layer 13b is developed (FIG. 3E). The development conditions are, for example, alkali development for 30 seconds and fixing with pure water washing for 30 seconds. Thereby, for example, the exposed portion of the photosensitive layer 13b is removed and the unexposed portion is left (or the unexposed portion is removed and the exposed portion is left). The patterned layer 13c is patterned into a diffraction grating-like uneven shape. Here, since the photosensitive layer 13b is exposed to the shape of the end faces t1 and t2 and the re-exposure of the end face scattering and the back face reflection by the antireflection film 12 in step S14, it is accurately patterned into a diffraction grating pattern. The patterned layer 13c can be obtained.

(S16) Next, the patterning layer 13c and the substrate 11a are etched (FIG. 3F). The etching may be a method that allows the patterning layer 13c and the substrate 11a to be sequentially removed from the surface layer by etching. For example, RIE (reactive ion etching) or reactive gas using fluorine-based gas such as CF ₄ , Ar gas, or a mixed gas thereof. Etching) or ion beam etching. At this time, since the patterning layer 13c becomes a mask pattern of the substrate 11a, the substrate 11a is accurately etched into the concavo-convex shape of the diffraction grating pattern corresponding to the pattern of the patterning layer 13c, and the concavo-convex portion 14 is formed. Is done.

FIG. 10 shows the configuration of the substrate 11 after the etching process. 10A is a plan view of the substrate 11 as viewed from above, and FIG. 10B is a cross-sectional view of the substrate 11.
In a predetermined region of the substrate 11, a concave-convex shape of the diffraction grating pattern, that is, a grid structure in which convex lines are arranged at regular intervals on the substrate 11 is exhibited (FIG. 10A). The pitch which is the interval between the adjacent convex portions 14a and the convex portions 14a or the interval between the concave portions 14b and the concave portions 14b corresponds to the above formula (2). Further, the cross-sectional shape of the concavo-convex portion 14 is a sawtooth shape in which the tip end portion of the convex portion 14a is tapered (FIG. 10B).

  Note that the concavo-convex portion 14 including the convex portion 14 a and the concave portion 14 b is a line of the convex portion 14 a formed on the main surface of the substrate 11 so as to extend in one direction (absorption axis Y direction) parallel to the main surface of the substrate 11. Are periodically formed in a direction (line arrangement direction, transmission axis X direction) orthogonal to the absorption axis Y direction of the substrate 11 at a pitch smaller than the wavelength of the visible light region. Accordingly, the recess 14b between the lines of the protrusion 14a has a valley shape in cross section, and becomes a groove extending in one direction (absorption axis Y direction) parallel to the main surface of the substrate 11. This uneven shape is provided in order to form the inorganic fine particle layer 15 formed in the next step in a wire grid shape. Therefore, the shape and size of the uneven portion 14 are important for obtaining the desired polarization characteristics of the polarizing element 10, but in the present invention, the uneven portion 14 is etched according to the patterning layer 13c of the diffraction grating pattern formed with high precision. Is formed into a concavo-convex shape suitable for a wire grid structure.

(S17) The inorganic fine particle layer 15 is formed by performing sputter film formation in which the inorganic fine particles p are incident on the top of the convex portion 14a of the concave and convex portion 14 of the substrate 11 or at least one side surface thereof from a diagonal direction at a predetermined angle. (FIG. 3 (g)). FIG. 11 shows the state of oblique sputtering film formation. Here, an example of ion beam sputtering is shown.

  In FIG. 11, 1 is a stage for supporting the substrate 11, 2 is a target, 3 is a beam source (ion source), and 4 is a control plate. The stage 1 is inclined at a predetermined angle α with respect to the normal direction of the target 2, and the substrate 11 has a direction in which the lattice direction (longitudinal direction) of the uneven portion 14 is orthogonal to the incident direction of the inorganic fine particles from the target 2. Is arranged. The angle α is, for example, 0 ° to 15 °. Ions extracted from the beam source 3 are irradiated to the target 2. The inorganic fine particles knocked out from the target 2 by the irradiation of the ion beam are incident on and adhered to the surface of the substrate 11 from an oblique direction. At this time, if the flat control plate 4 is arranged on the substrate 11 at a constant interval (for example, 50 mm), the direction of the incident particles on the surface of the substrate 11 is controlled, and the particles are deposited only on the side wall portion of the convex portion 14a. Can do.

  As described above, by tilting the substrate 11 with respect to the target 2 at the time of film formation and restricting the incident direction of the inorganic fine particles, the inorganic fine particle layer 15 made of inorganic fine particles is selected as the top portion or one side surface portion of the convex portion 14a. Thus, the polarizing element 10 can be formed (FIG. 12).

Here, as the material used for the inorganic fine particle layer 15, an appropriate material needs to be selected according to the use band. Metal materials and semiconductor materials satisfy these requirements. Specifically, in the case of metals, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, Si, Ge, Te, Sn, Au , Ag, Cu alone or an alloy containing them. The semiconductor material is Si, Ge, Te, ZnO. Further FeSi ₂ (particularly _{β-FeSi 2), MgSi 2} , silicide-based materials such as _{NiSi 2, BaSi 2, CrSi 2} , CoSi 2 is suitable. In the present invention, the target 2 made of these materials is used in the oblique sputtering film formation of FIG.

  In the polarizing element 10 manufactured by the above method, as shown in FIG. 12, the inorganic fine particle layer 15 formed on the surface of the substrate 11 is distributed with an anisotropic shape in the in-plane X and Y directions. (Wire grid structure). These inorganic fine particle layers 15 exhibit a characteristic of absorbing a polarized component having an electromagnetic traveling direction in the major axis direction (Y direction) and transmitting a polarized component having an electromagnetic traveling direction in the minor axis direction (X direction). In addition, in the interference exposure, re-exposure due to scattering on the end surfaces t1 and t2 of the substrate and reflection on the back surface Sb is prevented, so that the in-plane spectral characteristic distribution as the polarizing element 10 becomes uniform. Furthermore, since the substrate 11 excellent in heat dissipation is used as the substrate of the polarizing element 10, it has better heat resistance than the conventional inorganic absorption polarizing element, and is used in, for example, a liquid crystal projector device or the like in the vicinity of the light source for a long time. Even if it is exposed and heated, since it has good heat dissipation, a polarizing element that is less prone to malfunction than a glass substrate can be obtained.

  Note that the same antireflection film as the antireflection film 12 may be formed on the end surfaces t1 and t2 instead of forming the end surfaces t1 and t2 of the substrate 11a to be inclined. However, since the end surface of the substrate 11a is a sand-printed surface or a surface that has been cut, the formed film is peeled off, or the scattering of stray light does not decrease due to partial film formation, On the other hand, there is a possibility of increasing the number, so that it is necessary to treat the end face to obtain a good film formation.

  Moreover, you may form the layer (ultraviolet light absorption layer) which absorbs the said ultraviolet light in the slope of end surface t1, t2. However, particles such as carbon having a relatively large absorption coefficient in an adhesive (binder) that absorbs small amounts of visible light in visible light that is applied to the edge of the lens (externally processed end face) with a lens barrel for a camera. The ink is designed so that there is no reflection on the surface of the ink as a whole by repeating the reflection and absorption of light inside the applied ink (so that the light does not go out of the ink again) Is not suitable because the absorption coefficient of the adhesive (binder) increases with ultraviolet light. In the present invention, it is only necessary to apply to the end surfaces t1 and t2 black ink exclusively for the ultraviolet region in which particles having a relatively large absorption coefficient are dispersed in an adhesive (binder) having a small absorption light in the ultraviolet light. Such sanitization is effective in blocking stray light 1 that enters from the air side and enters the end faces t1 and t2 of the substrate 11a.

Next, a liquid crystal projector using the polarizing element according to the present invention will be described.
The liquid crystal projector of the present invention includes a lamp serving as a light source, a liquid crystal panel, and the polarizing element 10 of the present invention described above.

FIG. 13 shows a configuration example of the optical engine portion of the liquid crystal projector according to the present invention.
Optical engine portion of the liquid crystal projector 100, incident-side polarization element 10A with respect to the red light _{L R,} the liquid crystal panel 50, the emission pre-polarizing element 10B, outgoing main polarizing element 10C and the incident side polarizing element 10A with respect to the green light _{L G,} a liquid crystal panel 50, outgoing pre-polarizing element 10B, and the outgoing main polarizing element 10C, the incident side polarizing element 10A with respect to the blue light _{L B,} the liquid crystal panel 50, the emission pre-polarizing element 10B, and the outgoing main polarizing element 10C, each of the outgoing main polarizing element 10C And a cross dichroic prism 60 that synthesizes light emitted from the light and emits the light to a projection lens. Here, the polarizing element 10 of the present invention is applied to each of the incident side polarizing element 10A, the outgoing pre-polarizing element 10B, and the outgoing main polarizing element 10C.

In the liquid crystal projector 100 of the present invention, to separate the light emitted from the light source lamp (not shown) the red light L _R by the dichroic mirror (not _shown), the green light L _G, the blue light L _B, respectively corresponding to the light The light L _R , L _G , and L _{B that} is incident on the incident-side polarizing element 10A and then polarized by the respective incident-side polarizing elements 10A is spatially modulated and emitted by the liquid crystal panel 50, and is then emitted to the outgoing pre-polarizing element 10B. After passing through the outgoing main polarizing element 10C, it is synthesized by the cross dichroic prism 60 and projected from a projection lens (not shown). Since the light source lamp uses the polarizing element 10 of the present invention that has excellent light resistance against strong light and has a uniform in-plane spectral characteristic distribution even if it has a high output, a highly reliable liquid crystal projector Can be realized.

  The polarizing element of the present invention is not limited to application to the liquid crystal projector, but is suitable as a polarizing element that receives heat as a use environment. For example, the present invention can be applied as a polarizing element for a car navigation system of an automobile or a liquid crystal display of an instrument panel.

It is a schematic diagram which shows the relationship between a board | substrate and ultraviolet light. It is a schematic diagram which shows the scattering state of the stray light in a normal board | substrate end surface. It is process drawing which shows the manufacturing procedure of the polarizing element in the manufacturing method of the polarizing element which concerns on this invention. It is a schematic diagram which shows the shape of the board | substrate used by this invention. It is a schematic diagram which shows the scattering state of the stray light in the board | substrate end surface used by this invention. It is the schematic which shows the film | membrane structure of the antireflection film used by this invention. It is a schematic diagram which shows the structural example (1) of the optical system used for interference exposure. It is a schematic diagram which shows the structural example (2) of the optical system used for interference exposure. It is explanatory drawing which shows the mode of the interference fringe by interference exposure. It is the schematic which shows the uneven | corrugated state of the substrate surface at the time of completion | finish of an etching process. It is the schematic which shows the structure of oblique sputtering film-forming. It is the schematic which shows the structure of the polarizing element manufactured by the manufacturing method of the polarizing element which concerns on this invention. It is sectional drawing which shows the structure of the optical engine part of the liquid crystal projector using the polarizing element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stage, 2 ... Target, 3 ... Beam source (ion source), 4 ... Control board 10, 10A, 10B, 10C ... Polarizing element, 11, 11a ... Substrate , 12 ... Antireflection layer, 13a ... Resist layer, 13b ... Photosensitive layer, 13c ... Patterning layer, 14 ... Concave and convex part, 14a ... Convex part, 14b ... Concave part, 15 ... inorganic fine particle layer, 50 ... liquid crystal panel, 60 ... cross dichroic prism, 100 ... liquid crystal projector, L _1, L ₂ ... ultraviolet light, p ... inorganic fine particles, St, Sb ... main surface, t1, t2, t3, t4 ... end face

Claims (5)

A resist layer is formed on one main surface of the substrate by using a substrate that is transparent to visible light and has a pair of opposed end faces each having a slope with the other main surface protruding from one main surface. Then, ultraviolet light is incident on the resist layer so that the incident light is inclined with respect to the resist layer surface and an incident light beam surface including the ultraviolet light beam is perpendicular to the end surface as the inclined surface. A photolithography process for performing exposure and development and patterning the resist layer;
An etching step of etching one main surface side of the substrate to form a diffraction grating-shaped unevenness on the one main surface;
An inorganic fine particle layer forming step of forming an inorganic fine particle layer on the top or one side surface of the convex portion of the unevenness;
The manufacturing method of the polarizing element which has this. 2. The method for manufacturing a polarizing element according to claim 1, wherein an angle φ formed by an inclined surface at the end surface and a vertical surface of the main surface of the substrate is represented by the following formula (1).
φ> sin ⁻¹ (sin θ / n) (1)
(Θ: angle of incidence of ultraviolet light on the resist layer in the photolithography process, n: refractive index of the substrate with respect to the ultraviolet light)   The method for manufacturing a polarizing element according to claim 1, wherein a layer that absorbs the ultraviolet light is formed on the inclined surface.   An antireflection film forming step of forming an antireflection film having an antireflection function on visible light incident on the main surface of the substrate perpendicularly to the main surface of the substrate and ultraviolet light incident obliquely on the main surface of the substrate; The manufacturing method of the polarizing element in any one of Claims 1-3. A resist layer is formed on one main surface of the substrate by using a substrate that is transparent to visible light and has a pair of opposed end faces each having a slope with the other main surface protruding from one main surface. Then, ultraviolet light is incident on the resist layer so that the incident light is inclined with respect to the resist layer surface and an incident light beam surface including the ultraviolet light beam is perpendicular to the end surface as the inclined surface. A photolithography process for performing exposure and development and patterning the resist layer;
An etching step of etching one main surface side of the substrate to form a diffraction grating-shaped unevenness on the one main surface;
A polarizing element produced by a method for producing a polarizing element, comprising: an inorganic fine particle layer forming step of forming an inorganic fine particle layer on a top portion or one side surface portion of the convex portion of the unevenness.