JP2012027221A - Wire grid polarizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire grid polarizer achieving a high polarization degree without increasing an aspect ratio of wires, having excellent reflection characteristics in a visible light region, particularly in a wavelength range centering the maximum visual sensitivity wavelength of 555 nm and from 100 nm shorter to 100 nm longer than the center wavelength, and allowing easy processing.SOLUTION: The wire grid polarizer comprises a substrate 1, metal wires 10 arranged in a grid on the substrate 1, and multilayer wires 11 deposited in two or more layers on the metal wires 10. The multilayer wire 11 is a laminate including: a low refractive index layer composed of a low refractive index material having a refractive index nof 1.00 or more and 1.65 or less; and a high refractive index layer provided on the low refractive index layer and composed of a high refractive index material having a refractive index nof 1.80 or more and 4.50 or less. The low refractive index layer and the high refractive index layer are formed of materials selected from elements selected from elements the fluorides of which have a boiling point of 250 degrees or lower, and oxides, nitrides, sulfides and carbonates of the elements.

Description

  The present invention relates to a wire grid polarizer.

  With the recent development of photolithography technology, it has become possible to form a fine pattern having a light wavelength level pitch. Such a member or product having a very fine pattern with a very small pitch is useful not only in the semiconductor field but also in the optical field (Non-Patent Document 1).

  For example, a wire grid in which conductor wires made of metal or the like are arranged in a grid pattern at a specific pitch has a pitch that is considerably smaller than incident light (for example, visible light wavelength 400 nm to 800 nm). For example, if it is less than half, most of the electric field vector component light that oscillates in parallel to the conductor line is reflected, and almost no electric field vector component light perpendicular to the electric conductor line is transmitted. Can be used as a polarizer to produce a single polarization. Since this wire grid polarizer can reflect and reuse light that does not transmit, it is also desirable from the viewpoint of effective use of light.

  An example of such a wire grid polarizer is disclosed in Patent Document 1. The wire grid polarizer includes metal wires spaced at a grid period smaller than the wavelength of incident light. This wire grid polarizer has a polarization characteristic that the electric field component reflects the polarization component (TE wave) parallel to the metal wire and transmits the polarization component (TM wave) perpendicular to the metal wire, and is often used as a beam splitter. Has been.

  In such a wire grid polarizer, the relationship between the metal wire shape and the optical shape is shown, and when the metal wire cross-sectional area increases, the extinction ratio increases, and the metal wire more than a predetermined width with respect to the period width Then, it is known that the transmittance decreases (Patent Document 2). Moreover, when the cross-sectional shape orthogonal to the longitudinal direction of a metal wire is a taper shape, it has been known that the wavelength dispersion of transmittance and polarization degree is small in a wide band and shows high extinction ratio characteristics (Patent Document 3). .

  Patent Document 4 exemplifies a wire grid polarizer in which a dielectric wire is laminated on a metal wire.

  Furthermore, as a promising method for forming a nano-sized lithography mask structure using a fine pattern, a method of transferring a pattern by pressing a mold having a fine pattern against a thermoplastic resin or a photocurable resin is known. (Patent Document 5, Non-Patent Document 2). As such a method, Patent Document 6, Non-Patent Document 3, and the like can be referred to.

  Further, Patent Document 7 discloses a method of providing a dielectric wire or layer on a metal wire for the purpose of improving scratch resistance or antifouling property.

  In addition, when a wire grid polarizer is used for a liquid crystal display device or the like, Patent Documents 8 and 9 disclose a method of bonding with an absorption polarizing plate or the like for the purpose of reducing reflection of external light and improving a contrast ratio. Is disclosed.

JP 2003-502708 A Japanese translation of PCT publication No. 2003-508813 JP 2005-172844 A Special table 2008-523422 gazette JP 2009-145742 A Japanese Patent Publication No.53-22427 JP 2007-33558 A JP-A-11-271534 JP 2006-330521 A

Bulletin of Japan Women's University Faculty of Science No. 14 (2006) Applied Physics Letters, vol. 96, 1995, pp. 3114-3116 IEICE technical report CPM76-125 (1977)

  As described above, the wire grid polarizer has excellent polarization characteristics. However, as shown in Patent Document 2, it can be seen that there is a large difference in transmittance and extinction ratio, that is, wavelength dispersion, in the wavelength range of 450 nm to 650 nm. Further, as a result of the study by the present inventors, it has been found that the wavelength dispersion of the transmittance at a wavelength of 400 nm to 800 nm in the structure shown in Patent Document 2 is very large. It is difficult to use.

  Moreover, as shown in Patent Document 3, in order to suppress a decrease in the extinction ratio and transmittance on the low wavelength side, it is effective to make the metal wire tapered, but the extinction ratio is increased. For this, it is necessary to increase the cross-sectional area of the metal wire. However, when the metal wire has a tapered shape, the cross-sectional area becomes smaller than that of the structure of Patent Document 2 even if the height of the metal wire is the same, so that it is higher to improve the extinction ratio. Metal wire height is required. However, when the tapered metal wire is made high, there is a problem that it is inferior in terms of workability and strength durability of the metal wire.

  In addition, the method described in Patent Document 7 requires film formation from a very deep angle with respect to the normal of the base material surface including the metal wire, and the thickness uniformity and large-scale production of the dielectric layer Leaving challenges in sex. Furthermore, as a result of studies by the present inventors, when the number of laminated dielectric layers and transparent materials provided on the metal wire increases, the polarized component (TM wave) having the transmitting characteristic is reflected by the interface between the layers. As a result, there was a problem that the transmittance was lowered.

  In addition, as a method of forming a wire shape on a substrate like a wire grid polarizer, after laminating a flat thin film made of metal or dielectric on the substrate, photolithography method, imprint method, electron beam A layer made of a resist material provided with a desired pattern is provided on the thin film by a drawing method or the like. Thereafter, using the layer as a mask, the thin film laminated by etching is processed into a wire shape. In this method, it is obvious that the dry etching method is an essential technique for anisotropically etching a thin film. However, among the materials exemplified in Patent Document 4, titanium dioxide, cadmium telluride, lead telluride and the like are very difficult to dry etch, and therefore, wire grid polarization using these materials as wires. It is difficult to make a child.

  Furthermore, in order to improve both the transmittance and the degree of polarization of the wire grid polarizer, there is a method of increasing the thickness while keeping the width of the metal wire (for example, aluminum wire) narrow. The aspect ratio of the wire (the thickness of the wire / the width of the wire) becomes large, and according to the study of the present inventor, when the aspect ratio is 5 or more, the wire falls down and may come into contact with the adjacent wire. .

  The method described in Patent Document 9 is required to reflect and reuse the light from the backlight while suppressing the reflection of external light. However, from the viewpoint of improving the efficiency of reuse of reflected light, further improvement in reflectivity is required, and it has been found that the reflectivity is insufficient when the wire grid portion is only a metal wire.

  The present invention has been made in view of the above points, and achieves a high degree of polarization without increasing the aspect ratio of the wire, and is in the visible light region, particularly in the range of 100 nm before and after centering on the maximum visibility wavelength of 555 nm, that is, An object of the present invention is to provide a wire grid polarizer that has excellent reflection characteristics at a wavelength of 455 nm to 655 nm and enables easier processing.

The wire grid polarizer of the present invention is a wire grid polarizer comprising a base material, metal wires arranged in a grid pattern on the base material, and multilayer wires laminated on the metal wire in two or more layers. The multilayer wire is provided on the low refractive index layer made of a low refractive index material having a refractive index n ₁ of 1.00 or more and 1.65 or less, and is provided on the low refractive layer, and is 1.80 or more and 4 And a high refractive index layer composed of a high refractive index material having a refractive index n ₂ of 50 or less, and the relationship between the refractive index and the film thickness of the multilayer wire is n ₁ d ₁ ≦ n ₂ d ₂ (d ₁ : film thickness of the low refractive index layer, d ₂ : film thickness of the high refractive index layer), and the low refractive index layer and the high refractive index layer have a fluoride boiling point of 250 degrees or less. An element selected from an element, and an oxide, nitride, sulfide of the element, Characterized in that it is formed of a material selected from any of the oxides.

  In the wire grid polarizer of the present invention, the material includes tantalum, molybdenum, tungsten, niobium, silicon, germanium, tellurium, and phosphorus, and a composite of two or more thereof, and oxides, nitrides, sulfides thereof, And a material selected from the group consisting of carbonates. Alternatively, the material is preferably a material selected from the group consisting of tantalum oxide, molybdenum oxide, tungsten oxide, silicon, silicon oxide, silicon nitride, germanium, germanium oxide, tellurium oxide, phosphorus oxide, and niobium oxide.

  The wire grid polarizer of this invention WHEREIN: It is preferable that the said base material is an absorption type polarizing plate of an iodine type polarizing plate or a dye type polarizing plate.

  The manufacturing method of the wire grid polarizer of the present invention includes a reflective material, a low refractive index material having a refractive index of 1.00 to 1.65, and a refractive index of 1.80 to 4.50 on a substrate. And a step of patterning the high refractive index material, the low refractive index material, and the reflective material to process them into a wire shape. The low-refractive index material and the high-refractive index material are elements selected from elements whose fluoride boiling point is 250 degrees or less, and oxides, nitrides, sulfides of the elements, It is a material selected from any of carbonates, and is characterized by being patterned into a wire shape by a dry etching method using a fluorine-based gas.

  ADVANTAGE OF THE INVENTION According to this invention, the wire grid polarizer which is excellent in the reflection characteristic in visible region, especially wavelength 455 nm to 655 nm, and can be processed easily can be provided.

It is a cross-sectional schematic diagram of the wire grid polarizer which concerns on embodiment of this invention. It is a dry etching relation figure of the metal material concerning an embodiment of the invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional perspective view showing an example of a wire grid polarizer according to an embodiment of the present invention. The wire grid polarizer shown in FIG. 1 has a grid-like metal wire 10 provided at a predetermined interval on a substrate 1, and a multilayer wire 11 is laminated on the metal wire 10. The multilayer wire 11 to be laminated may be a multilayer of two or more layers as will be described later, but here it will be described as two layers for simplicity. The multilayer wire 11 includes a low refractive index wire 12 and a high refractive index wire 13 as shown in FIG.

  Light incident on the wire grid polarizer can be considered as polarized light having two components. In the present invention, the light polarized in parallel with respect to the wire provided on the substrate is defined as TE polarized light, the reflectance is defined as R (TE), and the transmittance is defined as T (TE). Also, vertically polarized light is defined as TM polarized light, reflectance is defined as R (TM), and transmittance is defined as T (TM). The polarized light incident on the surface on which the multilayer wire 11 is provided reflects TE polarized light and transmits TM polarized light due to the structural and optical anisotropy of the wire. For this reason, most of the reflected light of the incident light is TE-polarized light, and most of the transmitted light is TM-polarized light. The reflected light also contains some TM polarization components, but R (TM) is almost negligible because R (TM) is as small as 1/20 of R (TE).

  In the present invention, by providing the multilayer wire 11, the reflectance of light incident on the surface on which the multilayer wire 11 is provided can be improved. According to a different expression, R (TE) can be increased by providing the multilayer wire 11 of the present invention rather than a wire grid polarizer in which only the metal wire 10 is processed into a wire shape.

  Aluminum, silver, and the like are known as highly reflective materials, but reflectivity is about 92% to 96% when those materials are formed flat on a glass substrate or the like with a thickness of about 200 nm. Actually, incident light is the outermost surface such as aluminum or silver, and about several percent of light is consumed as heat due to absorption of these metal materials. Therefore, the reflectance does not reach 96% or more. Even when a metal material is processed into a wire grid polarizer, the upper limit of the reflectance is determined by the absorption of the metal material.

  According to the inventor's consideration, when the multilayer wire 11 of the present invention is provided, the light incident on the surface provided with the multilayer wire 11 is first refracted by the incident medium and the high refractive index wire 13 on the surface of the high refractive index wire 13. Interfacial reflection occurs due to the rate difference. Furthermore, the light traveling through the high refractive index wire 13 without being reflected at the interface is reflected at the interface with the low refractive index wire 12 due to the difference in refractive index between the high refractive index wire 13 and the low refractive index wire 12. appear. Further, the light traveling through the low refractive index wire 12 without being reflected at the interface is reflected on the surface of the metal wire 10. Then, the incident light travels along the optical path as described above, whereby reflection occurs in the multilayer wire 11 and absorption at the outermost surface of the metal wire 10 is reduced. As a result, the incident light can increase the reflectance as compared with the case where the multilayer wire 11 is not provided.

  In other words, by providing the multilayer wire 11, TE-polarized light that is consumed as heat on the metal surface can be taken out as reflected TE-polarized light with a wire grid polarizer in which only the metal wire 10 is processed into a wire shape. It becomes.

  In general, a dielectric mirror in which a dielectric is laminated on a glass substrate or the like is known. This is because the low-refractive index material and the high-refractive index material are stacked alternately and in many layers so that the film thickness is ¼ of the optical film thickness with respect to the wavelength of incident light. By using the matching, the reflectance of incident light is increased.

  However, when the dielectric mirror structure is applied to the wire grid polarizer, the reflectivity does not show the maximum value when the optical film thickness of each dielectric layer is set to 1/4, and the value is 1/4. It is necessary to set it thinner. In addition, it is not possible to obtain a sufficient degree of polarization and reflectivity simply by processing the dielectric into a wire shape, and it is necessary to provide a wire made of a laminate of a reflective material such as aluminum, a high refractive index material, and a low refractive index material. It has become clear from the inventors' investigation.

  The material constituting the substrate 1 is not particularly limited as long as it has a smooth surface and is substantially transparent in the visible light region, and examples thereof include glass, transparent inorganic crystals, and transparent plastic. Examples of the glass include quartz glass and existing optical glasses such as BK (borosilicate crown), BaK (barium crown), LF (light flint), and SF (heavy flint). Of these, quartz glass is preferable because it is suitable for surface fine processing. Examples of the transparent inorganic crystal include sapphire, crystal, calcite, and alkali halide. Examples of the transparent plastic include polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin (COP), cross-linked polyethylene resin, polyvinyl chloride resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyether. Amorphous thermoplastic resin such as imide resin, polyether sulfone resin, polysulfone resin, polyether ketone resin, polyethylene terephthalate (PET) resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic Crystalline thermoplastic resins such as aromatic polyester resins, polyacetal resins, polyamide resins, and ultraviolet (UV) curable resins such as acrylic, epoxy, and urethane Curable resins.

  Further, as will be described later, a polarizing plate may be used as the substrate 1. As the polarizing plate, an iodine-type polarizing plate or a dye-type polarizing plate can be used, and the thickness of the polarizing plate is not limited, but in reality, it is preferably 1 μm to 5000 μm.

  As a material which comprises the metal wire 10, if it is a material with high light-shielding property, it can be used as a metal wire. In particular, aluminum, an aluminum alloy containing aluminum as a main component, or an aluminum mixed material is a preferable material from the viewpoints of workability and light shielding properties. Hereinafter, the material constituting the metal wire 10 is referred to as a reflective material.

  The material constituting the multilayer wire 11 is preferably a material containing at least one element having a fluoride boiling point of 250 degrees or less from the viewpoint of workability. More preferably, it is selected from the group consisting of tantalum, molybdenum, tungsten, niobium, silicon, germanium, tellurium, and phosphorus and a composite of two or more thereof, and oxides, nitrides, sulfides, and carbonates thereof. Preferably, the material is Among these, materials such as tantalum oxide, molybdenum oxide, tungsten oxide, silicon, silicon oxide, silicon nitride, germanium, germanium oxide, tellurium oxide, phosphorus oxide, and niobium oxide can be preferably used.

  From the viewpoint of refractive index, the low refractive index wire 12 and the high refractive index wire 13 constituting the multilayer wire 11 use a material having a refractive index in the range of 1.40 to 1.65. The high refractive index wire 13 is preferably made of a material having a refractive index in the range of 1.80 to 4.50. Moreover, in the combination of the material of the low refractive index wire 12 and the high refractive index wire 13, the combination from which a mutual refractive index difference becomes large is preferable, and it is preferable that a refractive index difference is 0.15 or more. For example, a combination in which a material having a refractive index of 1.40 is used for the low refractive index wire and a material having a refractive index of 4.50 is used for the high refractive index wire is most suitable. It is because the thickness of each wire layer can be made thin by doing so, and it is thought that it follows the way of thinking of an optical film thickness. In other words, since the optical film thickness is given by the product of the refractive index and the film thickness of each layer, the film thickness can be reduced by using a material having a high refractive index. In addition, the refractive index in this invention has shown the value in wavelength 550nm.

  As a specific example of the above contents, aluminum was formed with a film thickness of 100 nm, and silicon oxide was laminated thereon with a film thickness of 70 nm. Further, silicon having a film thickness of 50 nm and a refractive index of 4.05 was laminated thereon, and then a wire-forming process was performed. Then, when the reflectance of the surface in which the silicon wire was installed was measured, it was 44.8%. However, a wire grid polarizer was prepared by replacing silicon with molybdenum oxide having a refractive index of 2.00, and the reflectance was measured in the same manner. As a result, it was 40.1%. Therefore, when a similar wire grid was fabricated by changing the film thickness of molybdenum oxide from 50 nm to 120 nm, the reflectance could be increased to 44.5%. From the above, it can be said that the combination of the refractive indexes of the materials constituting the low refractive index wire 12 and the high refractive index wire 13 is preferably a combination in which the difference in refractive index between them becomes large. Preferably, the value of Y given by the following formula for the high refractive index wire 13 is preferably in the range of 0.25 to 1.00, more preferably in the range of 0.25 to 0.75. More preferably, it is in the range of 0.40 to 0.70, and most preferably in the range of 0.45 to 0.65.

Y = n ₂ d ₂ ÷ λ
n ₂ is the refractive index of the material constituting the high refractive index wire, d ₂ is the film thickness of the high refractive index wire, and λ is the wavelength of the incident light.

Moreover, about the low refractive index wire 12,
X = n ₁ d ₁ ÷ λ
And the combination of the refractive index and film thickness of the material constituting the low refractive index wire 12 and the high refractive index wire 13, that is, the relationship between X and Y is
X ≦ Y, that is, n ₁ d ₁ ≦ n ₂ d ₂
It is preferable that Here, n ₁ is the refractive index of the material constituting the low refractive index wire, d ₁ is the film thickness of the low refractive index wire, and λ is the wavelength of the incident light.

  Further, from the viewpoint of optical constants, among the above material groups, phosphorus oxide, silicon oxide, and germanium oxide are preferable as the low refractive index wire 12, and molybdenum oxide, niobium oxide, tantalum oxide, and tellurium oxide are preferable as the high refractive index wire 13. Tungsten oxide and silicon are preferable. Hereinafter, the material constituting the low refractive index wire 12 is referred to as a low refractive index material, and the material constituting the high refractive index wire 13 is referred to as a high refractive index material.

  The low refractive index wire 12 and the high refractive index wire 13 include the low refractive index wire 12 on the substrate 1, and the high refractive index wire 13 needs to be further laminated thereon. Moreover, when the combination of the low refractive index wire 12 and the high refractive index wire 13 is laminated a plurality of times, the order of the base material → the low refractive index wire → the high refractive index wire → the low refractive index wire from the base material side, or It is necessary to laminate in the order of base material → low refractive index wire → high refractive index wire → low refractive index wire → high refractive index wire.

  The workability here means etching characteristics. In order to produce a wire shape as shown in FIG. 1 on a base material, a flat thin film made of a metal or a dielectric is laminated on the base material, and a photolithography method, an imprint method, an electron beam drawing method, or the like is used. A layer made of a resist material having a desired pattern is provided on the thin film. Thereafter, using the layer as a mask, the thin film laminated by etching is processed into a wire shape. In this processing method, it is necessary to selectively (anisotropically) etch the thin film in the direction perpendicular to the base material, but the anisotropic etching method is very limited. For example, when the wet etching method is used, only the part of the material to be etched is changed in state (phase change, doping by ion implantation method, alloying, etc.), and the changed part is dissolved in the etching solution or changed. For example, only the unexposed portion is dissolved by an etching solution.

  However, since the wire grid polarizer used in the visible light region as shown in FIG. 1 needs to have a wire pitch in the submicron order, a method of changing the state only in such a fine region, or a certain level or more It is actually difficult to change the area equally.

  As a highly feasible anisotropic etching means, there is a dry etching method. This is a technique for etching an etching target material by introducing an etching gas reactive to the etching target material and ionizing or radicalizing the gas by plasma. Therefore, there is a reactivity factor between the material to be etched and the etching gas.

The etching gas generally used is C ₄ F ₈ , C ₃ F ₈ , C ₂ F ₈ , C ₂ F ₆ , C ₄ F ₆ , CH ₂ F ₂ , CHF ₃ , CF ₄ , CF ₄ , CF ₄ , CF ₄ , SF ₆ or the like. Examples of the chlorine-based gas include Cl ₂ , BCl ₃ , and CCl ₄ .

  Here, when considering the mechanism of dry etching with a fluorine-based gas, the fluorine activated in the vacuum chamber of the dry etching apparatus combines with the elements used in the low refractive index material and the high refractive index material, Forms fluoride. When the fluoride has a relatively high vapor pressure (ie, when the fluoride has a relatively low boiling point), the fluoride vaporizes and disappears from the low and high refractive index materials. As a result, it is etched. On the other hand, when the vapor pressure of the fluoride is relatively low (that is, when the boiling point of the fluoride is relatively high), the etching rate is slow or not etched because vaporization is difficult. The level of the vapor pressure is closely related to the boiling point of the fluoride.

As a result of repeated experiments, the present inventors have selected, as a material, an element having a boiling point of fluoride of the element of 250 degrees or less from among elements selected as a low refractive index material and a high refractive index material. Thus, from the viewpoint of manufacturing a wire grid polarizer, it was discovered that it has excellent workability, and its effect was confirmed. In addition, the boiling point of fluoride means the boiling point (= the boiling point of the main fluoride) of the fluoride of the main valence of the metal when the element forms a polyvalent fluoride. For example, when chromium is taken as an example, chromium can have a valence of 0, 2, 3, or 6. For this reason, CrF ₂ , CrF ₃ , and CrF ₆ can be formed as chromium fluoride, but since the main valence of chromium is trivalent, the main fluoride of chromium refers to CrF ₃ , The boiling point of the main fluoride refers to the boiling point of CrF ₃ .

The boiling point of the fluoride of the element constituting the low refractive index material and high refractive index material according to the present invention is 250 degrees or less, preferably 200 degrees or less, more preferably 100 degrees or less, and even more preferably 0 degrees or less. Yes, most preferably -70 degrees or less. As the boiling point of fluoride decreases, the dry etching efficiency using a fluorine-based gas increases. Table 1 below shows the fluoride boiling points of the elements constituting the low refractive index material and the high refractive index material according to the present invention. For comparison, the fluoride boiling points of titanium, chromium, and zirconium are also described. FIG. 2 shows the relationship between the boiling points of various metal fluorides disclosed in this specification and the dry etching rate by fluorine gas. The dry etching is a result obtained under the conditions of an applied power of 300 W and a processing pressure of 5.5 Pa, fluorine gas using tantalum and molybdenum using SF ₆ gas, and other materials using CF ₄ gas.

  As suggested by FIG. 2, the low refractive index material and the high refractive index material can have high dry etching efficiency by being composed of an element having a boiling point of fluoride of 250 degrees or less. Here, FIG. 2 shows the dry etching rate of a single metal, but also the oxide, nitride, carbide, carbonate, selenide, the metal contained in each compound greatly affects the dry etching rate, The same tendency is shown.

  Moreover, the base material 1 may use an absorption-type polarizing plate, and an iodine-type polarizing plate or a dye-type polarizing plate can be used as the absorption-type polarizing plate. This can enhance the polarization function as a wire grid polarizer by combining the metal wire 10, the multilayer wire 11, and the base material 1 made of an absorption polarizing plate.

  For example, when the transmittance when a wire grid polarizer is produced by laminating metal wires 10 and multilayer wires 11 using a quartz glass substrate as the base material 1 is given by T (TE) and T (TM) The degree of polarization P is given by the following formula (1).

P = [T (TM) −T (TE)] / [T (TM) + T (TE)] × 100 (1)
Here, since the transmittance of the quartz glass substrate is 90% or more, it is assumed that the quartz glass substrate is transparent, and T (TM) and T (TE) are considered to be light components transmitted through the metal wire 10 and the multilayer wire 11.

  In the above configuration, when the substrate 1 is changed to an absorptive polarizing plate, the polarization degree P described by the following formula (2) can be obtained by making the polarization axis parallel to the metal wire 10.

P = [T (TM) × τ (TM) −T (TE) × τ (TE)] / [T (TM) × τ (TM) + T (TE) × τ (TE)] × 100 (2)
Here, τ (TM): transmittance of light perpendicular to the polarization axis of the polarizing plate, and τ (TE): transmittance of light parallel to the polarization axis of the polarizing plate are shown. That is, by selecting an optimal value for the optical characteristics of the polarizing plate used for the substrate 1, the polarization characteristics of the wire grid polarizer can be improved.

  The optical performance required for the absorptive polarizing plate is not limited because it depends on the desired degree of polarization of the wire grid polarizer, but the total light transmittance is 30% or more and the degree of polarization is 80% or more, preferably The total light transmittance is 35% or more and the degree of polarization is 85% or more, more preferably the total light transmittance is 40% or more and the degree of polarization is 90% or more, and most preferably the transmittance is 40% or more. The degree is preferably 95% or more.

  Here, an example of a manufacturing method of the wire grid polarizer of the present invention will be described. First, a reflective material is disposed on the substrate 1. The reflective material can be provided by an ion plating method, a CVD method, a chemical adsorption, an electroforming method, a plating method, an MBE method, or the like, in addition to a sputtering film forming method and a vacuum vapor deposition film forming method. In particular, it is preferable to use a sputtering film formation method or a vacuum evaporation method because of the ease of film formation and the ease of increasing the area. In order to improve the adhesion between the base material 1 and the reflective material, the surface of the base material 1 is subjected to, for example, easy-adhesion coating, primer treatment, corona treatment, ozone treatment, high energy ray treatment, surface roughening treatment, and porous treatment. May be performed. Here, it has been clarified by the inventors that the thickness of the reflective material affects the polarization characteristics of the wire grid polarizer obtained in the present invention. Preferably it is the range of 50 nm to 300 nm, More preferably, it is the range of 100 nm to 250 nm.

  A low refractive index material is deposited on the reflective material with a desired film thickness, and a high refractive index material is further deposited thereon with a desired film thickness. Here, the film thickness of each material varies depending on the optical constant of each material, but from the viewpoint of workability, the film thickness is in the range of 10 nm to 200 nm, and more preferably in the range of 10 nm to 100 nm. As described above, the multilayer wire 11 may be formed by laminating a plurality of low refractive index materials and high refractive index materials.

  Next, a resist material made of a curable resin is uniformly applied on the high refractive index material. The coating method can be appropriately selected according to the size and material of the substrate 1, such as spin coating, bar coating, dip coating, reverse coating, and gravure coating. Details of each coating method are described in detail in the Converting Technology Handbook (2006) published by Processing Technology Research Institute, Inc. and can be referred to. For example, when a glass substrate having a size of about 100 mm square is used as the base material 1, a spin coating method can be selected from the viewpoint of simplicity of the coating apparatus and film thickness uniformity. Even when an absorption polarizing plate is used as the substrate 1, the absorption polarizing plate is swelled or bent by a state in which the absorption polarizing plate is bonded to a flat plate (for example, a glass substrate) or by a vacuum chuck method. If it is fixed in a state where it does not occur, spin coating can be applied.

  Next, the resist material is patterned by any of the following methods. The first method is an imprint method in which patterning is performed by pressing a mold on which a pattern is drawn against a resist material. According to this method, even a fine structure can be patterned quickly and easily. Moreover, the mold once produced can be used for patterning several times. After imprinting, a desired pattern can be obtained by removing the residue of the concave portion by the dry etching method while leaving the convex portion of the pattern. As the resist material, a commercially available photocurable resin such as PAK-01 (manufactured by Toyo Gosei Co., Ltd.) can be used. Alternatively, a thermoplastic resin such as polydimethylsiloxane or polystyrene can be used as a resist material by a thermal imprint method.

  The second method can be patterned by photolithography. According to this method, a photomask once produced can be used a plurality of times, and patterning can be performed at high speed by adjusting the exposure amount. When the pattern size becomes extremely fine, there is a drawback that clear patterning cannot be performed due to light interference. However, patterning is possible even in a fine shape by a technique such as interference exposure. After pattern exposure, a desired pattern can be obtained by removing unexposed portions with a solvent or the like. As the photoresist material, a commercially available PMER series (manufactured by Tokyo Ohka Co., Ltd.) or the like can be used.

  As a method other than the above, a method of exposing with an electron beam instead of the light exposure of the photolithography method or a method of directly patterning a resist material with an electron beam can be applied. From the viewpoint of improving efficiency, it is preferable to apply the above method.

  The patterned resist material is then used as a mask in a dry etching process described later. In the dry etching process, a high refractive index material, a low refractive index material, and a reflective material are patterned by dry etching and processed into a wire shape.

  In the dry etching process, first, the high refractive index material and the low refractive index material are etched using the patterned resist as a mask. As the gas used for the etching, a suitable gas type can be selected depending on the material constituting the high refractive index material and the low refractive index material. When etching tantalum oxide, molybdenum oxide, tungsten oxide, silicon, silicon oxide, silicon nitride, germanium, germanium oxide, tellurium oxide, phosphorus oxide, or niobium oxide, it is preferable to mainly select a fluorine-based gas. Moreover, when etching aluminum which is a reflective material, it is preferable to mainly use chlorine gas.

  In the present invention, it is necessary to dry-etch the reflective material, the low refractive index material, and the high refractive index material. Since the order in which dry etching is performed is performed from the upper layer side of each layer, it is processed in the order of a patterned resist material, then a high refractive index material, then a low refractive index material, and finally a reflective material. .

  In the dry etching step, the upper layer material is required to have dry etching resistance when the lower layer material is dry-etched. For example, when a high refractive index material is dry-etched, the resist material that is an upper layer thereof is required to have resistance to dry etching conditions of the high refractive index material. Similarly, when a low refractive index material is dry-etched, it is required that the high-refractive index material, which is an upper layer thereof, be resistant to the dry etching conditions of the low refractive index material. The same applies when the reflective material is dry-etched.

  Further, the resist material may not have resistance when the low refractive index material and the reflective material are dry-etched. In this case, this is because, even if the resist material does not have dry etching resistance, the high refractive index material functions as a mask for the dry etching process.

  Further, using the material of one upper layer as a mask, the two layers located under the lower layer may be simultaneously dry-etched. That is, the high-refractive index material and the low-refractive index material located in the lower layer may be simultaneously dry-etched using the upper resist material as a mask. For this purpose, it is necessary to use a material having a high dry etching resistance as the resist material or to maintain a certain film thickness during patterning.

  When the reflective material is dry-etched, it is preferable to use a chlorine-based gas as described above, but generally there are not many materials with high resistance to the chlorine-based gas. For this reason, there is a possibility that the high refractive index material is etched by the chlorine-based gas. In order to prevent this, a layer such as silicon oxide is provided as a hard mask layer between the high refractive index material and the resist material. Also good.

  Strictly speaking, a silicon oxide layer as a hard mask layer becomes a low-reflective material wire in terms of optical constant, but by making the hard mask layer a very thin layer of about 10 nm, optical influence is reduced. Can be installed without affecting. Incidentally, it has been clarified by the examination of the present invention that even a thin film of 10 nm can be given sufficient resistance in the dry etching process. The film thickness of the hard mask layer is preferably in the range of 5 nm to 15 nm, more preferably in the range of 5 nm to 12 nm, and still more preferably in the range of 5 nm to 10 nm.

  Next, examples performed for clarifying the effects of the present invention will be described. In addition, this invention is not limited at all by the following examples.

[Example 1]
1) Film formation of reflective material, low refractive index material, and high refractive index material Sputter film formation (by Shibaura Mechatronics Co., Ltd.) using TAC film as a base material and aluminum on the base material to a thickness of 100 nm Then, a silicon oxide film was formed thereon by sputtering so as to have a thickness of 70 nm. Further, a silicon film was formed thereon by sputtering so as to have a thickness of 50 nm. The sputtering film formation conditions were an applied power of 200 V, a film formation pressure of 0.5 Pa, an Ar gas flow rate of 50 sccm, and the film thickness was controlled by the film formation time.

2) Application of resist The non-deposited surface of the TAC film substrate formed as described above is bonded to a glass substrate, and a photocurable resist (PAK-01; Toyo Gosei Co., Ltd.) is formed on the film formation surface by spin coating. Kogyo Co., Ltd.) was uniformly applied at a rotation speed of 2000 rpm so as to have a thickness of 100 nm. Then, after drying for 5 minutes in 70 degreeC oven, the TAC film base material was peeled from the glass substrate.

3) Resist mask formation A resin mold (pattern mold) having a line & space pattern with a pitch of 130 nm, a duty of 0.4, and a pattern height of 180 nm is prepared, and the resist is uniformly pressed (applied) Under a pressure of 0.1 MPa, UV light including a wavelength of 365 nm was irradiated from the resin mold side with a light amount of 1000 mJ / cm ² and photocured, and then the resin mold was peeled off. Further, a concave portion of the resist pattern was selectively etched by plasma with oxygen gas using an RIE apparatus (Reactive Ion Etching treatment apparatus: manufactured by ULVAC) to obtain a resist mask leaving only the convex part. Etching conditions at that time are an oxygen flow rate of 10 sccm, a pressure of 0.2 Pa, an applied power of 50 V, and a processing time of 20 seconds.

4) Dry etching treatment of low-refractive index material and high-refractive index material After formation of the resist mask, a layer made of silicon and a layer made of silicon oxide are perpendicular to the TAC substrate by RIE apparatus using plasma with CHF ₃ gas. Etching was anisotropic in the direction. The dry etching processing conditions at this time are a processing pressure of 0.5 Pa, an applied power of 100 W, a bias power of 50 W, and an antenna power of 100 W.

5) Dry etching treatment of the reflective material After the etching treatment to the layer made of silicon oxide, the layer made of aluminum is anisotropically etched in the direction perpendicular to the TAC direction by plasma with Cl gas in the RIE apparatus. did. The dry etching processing conditions at that time are a processing pressure of 0.2 Pa, an applied power of 100 W, a bias power of 50 W, and an antenna power of 100 W. Furthermore, the resist mask remaining on the upper part of the layer made of silicon was removed by etching with plasma using oxygen gas to obtain a wire grid polarizer.

6) Optical performance evaluation As a result of measuring the degree of polarization of the wire grid polarizer obtained by the above process using a polarization photometer (manufactured by JASCO Corporation), the degree of polarization at 555 nm was 99.89, and the transmittance was 40.3. %. Furthermore, as a result of measuring the reflectance (light incident angle 5 degrees) with a reflection spectrophotometer (manufactured by Shimadzu Corporation), it was found that the average reflectance from 455 nm to 655 nm was 44.8%.

[Example 2]
A wire grid polarizer was produced by the same method and configuration as in Example 1 using an iodine type polarizing plate as a substrate. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm is 99.98, the transmittance is 36.3%, and the average reflectance from a wavelength of 455 nm to 655 nm is 44.5%. I found out.

[Example 3]
A wire grid polarizer was produced in the same manner as in Example 1 using a TAC film as a substrate. The wire structure at this time was made of aluminum as a metal wire with a thickness of 80 nm, the low refractive index wire was made with silicon oxide with a thickness of 70 nm, and the high refractive index wire was made with molybdenum oxide with a thickness of 105 nm. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm was 98.66, the transmittance was 39.1%, and the average reflectance from a wavelength of 455 nm to 655 nm was 45.4%. I found out. Moreover, as a result of measuring the wire structure with a scanning probe microscope, it was found that the wires were aligned at an equal interval of 130 nm without falling down.

[Example 4]
A wire grid polarizer was produced by the same method and configuration as in Example 3 using an iodine type polarizing plate as a substrate. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm is 99.92, the transmittance is 35.0%, and the average reflectance from a wavelength of 455 nm to 655 nm is 45.2%. I found out.

[Example 5]
A wire grid polarizer was produced in the same manner as in Example 1 using a TAC film as a substrate. The wire structure at this time was made of aluminum as a metal wire with a thickness of 80 nm, the low refractive index wire was made of germanium oxide with a thickness of 70 nm, and the high refractive index wire was made of molybdenum oxide with a thickness of 105 nm. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm was 98.36, the transmittance was 39.8%, and the average reflectance at a wavelength of 455 nm to 655 nm was 44.1%. I found out. Moreover, as a result of measuring the wire structure with a scanning probe microscope, it was found that the wires were aligned at an equal interval of 130 nm without falling down.

[Example 6]
A wire grid polarizer was produced by the same method and configuration as in Example 5 using an iodine type polarizing plate as a substrate. As a result of evaluating the optical characteristics with a polarization photometer and a reflection spectrophotometer, the degree of polarization at a wavelength of 555 nm was 99.91, the transmittance was 35.5%, and the average reflectance at wavelengths from 455 nm to 655 nm was 44.0%. I found out.

[Example 7]
A wire grid polarizer was produced in the same manner as in Example 1 using a TAC film as a substrate. The wire configuration at this time was made of aluminum as a metal wire with a film thickness of 80 nm, the low refractive index wire was formed with phosphorous oxide with a film thickness of 30 nm, and the high refractive index wire was formed with niobium oxide with a film thickness of 130 nm. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the degree of polarization at a wavelength of 555 nm is 98.46, the transmittance is 39.6%, and the average reflectance from a wavelength of 455 nm to 655 nm is 43.3%. I found out. Moreover, as a result of measuring the wire structure with a scanning probe microscope, it was found that the wires were aligned at an equal interval of 130 nm without falling down.

[Example 8]
A wire grid polarizer was produced by the same method and configuration as in Example 5 using an iodine type polarizing plate as a substrate. As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm is 99.91, the transmittance is 35.4%, and the average reflectance from a wavelength of 455 nm to 655 nm is 43.1%. I found out.

[Comparative Example 1]
In order to compare the etching characteristics of the multilayer wire, a sputtering film of TiO ₂ was prepared, and a dry etching rate comparison with a sputtering film of tellurium oxide was performed. The dry etching rate of tellurium oxide was 36 nm / min, whereas the dry etching rate of TiO ₂ was very slow at 1.6 nm / min. If the wire grid polarizer of the present invention is produced using TiO ₂ as a high refractive index material, the resist mask is etched with fluorine gas before the TiO ₂ is etched at this etching rate, and disappears. This suggests that the wire shape is difficult to form.

[Comparative Example 2]
In order to compare the effect of improving the reflectivity of the multilayer wire, a wire grid polarizer was prepared on a TAC film substrate with an aluminum wire as a metal wire having a height of 100 nm. The manufacturing method is the same as in Example 1.

  As a result of evaluating the optical characteristics using a polarization photometer and a reflection spectrophotometer, the polarization degree at a wavelength of 555 nm is 99.19, the transmittance is 40.1%, and the average reflectance from a wavelength of 455 nm to 655 nm is 42.0%. In other words, it was revealed that the reflectance is lower than that in the case where the multilayer wire is provided (Example 1).

  The wire grid polarizer according to the present invention is a highly feasible wire grid polarizer that has excellent reflection characteristics and enables processing. Specifically, it is useful in a member such as a liquid crystal display element and the optical field.

DESCRIPTION OF SYMBOLS 1 Base material 10 Metal wire 11 Multilayer wire 12 Low refractive index wire 13 High refractive index wire

Claims (5)

A wire grid polarizer comprising a substrate, a metal wire arranged in a lattice pattern on the substrate, and a multilayer wire laminated on the metal wire by two or more layers,
The multilayer wire is provided on a low refractive index layer made of a low refractive index material having a refractive index n ₁ of 1.00 or more and 1.65 or less, and on the low refractive layer, and is 1.80 or more and 4.50. A high refractive index layer composed of a high refractive index material having the following refractive index n ₂ ,
The relationship between the refractive index and the film thickness of the multilayer wire is n ₁ d ₁ ≦ n ₂ d ₂ (d ₁ : film thickness of the low refractive index layer, d ₂ : film thickness of the high refractive index layer),
The low refractive index layer and the high refractive index layer are selected from an element selected from elements having a fluoride boiling point of 250 degrees or less, and oxides, nitrides, sulfides, and carbonates of the elements. A wire grid polarizer characterized by being made of a material.   The material is selected from the group consisting of tantalum, molybdenum, tungsten, niobium, silicon, germanium, tellurium and phosphorus and a composite of two or more thereof, and oxides, nitrides, sulfides and carbonates thereof. The wire grid polarizer according to claim 1, wherein the wire grid polarizer is a material.   The material is a material selected from the group consisting of tantalum oxide, molybdenum oxide, tungsten oxide, silicon, silicon oxide, silicon nitride, germanium, germanium oxide, tellurium oxide, phosphorus oxide, and niobium oxide. Item 10. A wire grid polarizer according to item 1.   The wire grid polarizer according to any one of claims 1 to 3, wherein the substrate is an absorption polarizing plate of an iodine type polarizing plate or a dye type polarizing plate. A reflective material, a low refractive index material having a refractive index of 1.00 to 1.65, and a high refractive index material having a refractive index of 1.80 to 4.50 are sequentially stacked on the substrate. And a step of patterning the high refractive index material, the low refractive index material and the reflective material into a wire shape, and a method of manufacturing a wire grid polarizer,
The low refractive index material and the high refractive index material are selected from elements selected from elements having a boiling point of fluoride of 250 degrees or less, and oxides, nitrides, sulfides, and carbonates of the elements. A method of manufacturing a wire grid polarizer, characterized in that the material is patterned into a wire shape by a dry etching method using a fluorine-based gas.

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