JP2007187994A - Antireflection film and optical filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an optical filter having an antireflection film at a low cost by rapid film-forming technology using a low-cost facility. <P>SOLUTION: A low refractive index transparent film and a high refractive index transparent film constituting the antireflection film of the optical filter are film-formed by a gas flow sputtering method. Since high vacuum gas exhausting is unnecessary, the gas flow sputtering method can be executed by using a low-cost facility and rapid film formation can be achieved. Thereby by adopting the gas flow sputtering method, cost of equipment is reduced and film-forming time is shortened and consequently the optical filter can be manufactured at a low cost. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antireflection film and an optical filter, and more particularly to an antireflection film formed by a gas flow sputtering method and an optical filter having the antireflection film.

PDP (plasma display panel) for OA equipment, liquid crystal plates, window materials for vehicles or special buildings are provided with an antireflection film on a transparent substrate to prevent light reflection and ensure high light transmission. An optical filter is applied. Conventionally, an antireflection optical filter used for this type of application has a structure in which a transparent film such as TiO ₂ , SiO ₂ , ITO, SnO ₂ , or MgF ₂ is laminated on a substrate. In recent years, a structure in which a high refractive index transparent film and a low refractive index transparent film are laminated has been proposed as an optical filter.

Usually, as these high refractive index transparent film and low refractive index transparent film, organic or inorganic insulators or semiconductor films are used. For example, Japanese Patent Application Laid-Open No. 11-142603 discloses a high refractive index transparent film made of ZnO, TiO ₂ , SnO ₂ , ZrO, etc. doped with ITO (tin indium oxide) or ZnO, Al, SiO ₂ , MgF _2. And an antireflection film in which low refractive index transparent films made of Al ₂ O _{3 and the} like are alternately formed on an organic film.

  Moreover, in such an antireflection film, an organic film is used as a transparent substrate, and a hard coat layer is formed between the organic film and the antireflection film (Japanese Patent Laid-Open No. 11-305008). .

  Conventionally, a high-refractive index transparent film and a low-refractive index transparent film constituting an antireflection film on a transparent substrate are sputtering methods (planar-type magnetron sputtering method, hereinafter sometimes referred to as “normal sputtering method”). It is formed by.

Note that the gas flow sputtering method to be described later employed in the present invention is a known film formation method, and the applicant of the present invention previously performed the gas flow sputtering method on the catalyst layer of the polymer electrolyte fuel cell electrode or the dye. Techniques applied to the formation of semiconductor electrode layers for sensitized solar cells have been proposed (Japanese Patent Application Nos. 2004-319592, 2004-319548, and 2004-319598).
Japanese Patent Laid-Open No. 11-142603 JP-A-11-305008 Japanese Patent Application No. 2004-319592 Japanese Patent Application No. 2004-319548 Japanese Patent Application No. 2004-319598

  Conventional sputtering methods used to form high-refractive-index transparent films and low-refractive-index transparent films that constitute antireflection films can be formed uniformly, but the film-forming speed is slow, and vacuum chambers are used. Since a large exhaust system is indispensable for exhausting the interior to a high vacuum state, there is a disadvantage that expensive equipment is required.

  In particular, when a transparent film having a low refractive index is formed, a film having a lower refractive index can be formed by providing a gap at the time of film formation, but an appropriate gap is formed by a normal sputtering method. There was also a problem that it was not easy.

  Furthermore, in a normal sputtering method, since a magnet is provided below the target, a target region having a strong horizontal magnetic field directly above the target is selectively sputtered and consumed, so that the target utilization efficiency is low. there were.

  The present invention solves the above-described conventional problems, does not require expensive equipment such as sputtering, and can perform high-speed film formation, and can easily control film formation conditions for forming voids. An object of the present invention is to provide a high-performance antireflection film and an optical filter having the antireflection film at a low cost by a film forming technique with a high effective utilization rate of a target.

  The antireflection film of the present invention (Claim 1) is formed by gas flow sputtering.

  An antireflection film according to a second aspect is characterized in that, in the first aspect, the antireflection film is formed of a laminated film of a high refractive index transparent film and a low refractive index transparent film.

  According to a third aspect of the present invention, there is provided the antireflection film according to the second aspect, wherein at least the low refractive index transparent film is formed by a gas flow sputtering method.

Antireflection coating according to claim 4, in claim 2 or 3, the high-refractive-index transparent film ITO, ZnO, _TiO 2, Al-doped _{ZnO, SnO 2, In 2 O} 3, Nb 2 O 5, Ta 2 O _5. It is characterized by being made of Ga-doped ZnO, TiN, or ZrO.

An antireflection film according to claim 5 is characterized in that, in any one of claims 2 to 4, the low refractive index transparent film is made of SiO ₂ , MgF ₂ , Si ₃ N ₄ , or Al ₂ O _3. To do.

  An antireflection film according to a sixth aspect is characterized in that, in any one of the second to fifth aspects, the laminated film is an alternating laminated film of a high refractive index transparent film and a low refractive index transparent film.

  An optical filter of the present invention (invention 7) is characterized in that the antireflection film according to any one of claims 1 to 6 is formed on a transparent substrate.

  An optical filter according to an eighth aspect is characterized in that, in the seventh aspect, a hard coat layer is provided between the transparent substrate and the antireflection film.

  An optical filter according to a ninth aspect is the optical filter according to the seventh or eighth aspect, wherein the uppermost layer of the antireflection film is a low refractive index transparent film having a low density.

  The gas flow sputtering method is a method in which sputtering is performed under a relatively high pressure, and sputtered particles are transported to a deposition target substrate by a forced flow of gas and deposited. Since this gas flow sputtering method does not require high vacuum evacuation, it is possible to form a film by mechanical pump evacuation without using a large evacuation device like the conventional normal sputtering method. It can be implemented with inexpensive equipment. Moreover, the gas flow sputtering method can form a film 10 to 1000 times faster than the usual sputtering method. Therefore, according to the present invention, it is possible to manufacture the antireflection film and the optical filter at low cost by reducing the equipment cost and the film formation time by adopting the gas flow sputtering method.

  In particular, when forming a transparent film having a low refractive index, a large power can be applied to greatly increase the film formation speed or the film formation pressure can be increased so that voids can be easily formed during film formation. A sufficiently low low refractive index transparent film can be formed. Moreover, since a magnet is not provided under the target, the effective utilization rate of the target is as high as 90% or more.

  And if it is a gas flow sputtering method, a film | membrane with favorable adhesiveness with respect to a transparent base material can be formed into a film, and a high quality anti-reflective film and an optical filter can be manufactured.

  Embodiments of an antireflection film and an optical filter according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1A is a schematic diagram showing a schematic configuration of a gas flow sputtering apparatus suitable for carrying out the present invention, and FIG. 1B shows a target and back plate configuration of FIG. 1A. It is a perspective view. 2 and 3 are system diagrams showing an embodiment of the optical filter of the present invention. 2 and 3, members having the same function are denoted by the same reference numerals.

  First, with reference to FIG. 1, the film-forming method by the gas flow sputtering method employ | adopted by this invention is demonstrated.

  In the gas flow sputtering apparatus, a rare gas such as argon is introduced into the chamber 20 from the sputtering gas inlet 11 and is generated by discharge between an anode 13 connected to a power source 12 such as a DC power source and a target 15 serving as a cathode. The target 15 is sputtered by the generated plasma, and the sputtered particles that have been blown off are transported to the substrate 16 and deposited by a forced flow of a rare gas such as argon. In the illustrated example, the substrate 16 is supported by a holder 17, and a reactive gas inlet 18 is disposed in the vicinity of the substrate 16 so that reactive sputtering can be performed. Reference numeral 14 denotes a water-cooled backing plate.

  In the present invention, by using such a gas flow sputtering apparatus, any one layer or two or more layers of a high refractive index transparent film and a low refractive index transparent film, which will be described later, constituting the antireflection film are gas flow sputtering methods. The film is formed by

  The film forming method and film forming conditions for each layer will be described below.

<High refractive index transparent film>
When a high refractive index transparent film is formed by gas flow sputtering, the targets are Ti, Nb, Ta, In, Sn, ITO (Sn doped In ₂ O ₃ ), InSn alloy, Zn, AZO (Al doped ZnO). ), GZO (Ga-doped ZnO), ZnAl alloy, ZnGa alloy, and one or more selected from the group consisting of Zr, and depending on the size of the chamber and the target size, the film is formed under the following conditions: can do.
Sputtering pressure: 10-100 Pa
Sputter power density: 1 to 25 W / cm ²
Argon: 0.5-30 SLM
Reactive gas: 0 to 120 sccm
Substrate temperature: room temperature

Usually, the high refractive index transparent film is made of ITO (tin indium oxide), ZnO, Al-doped ZnO, TiO ₂ , SnO ₂ , In ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Ga-doped ZnO, TiN. A high refractive index material having a refractive index of 1.8 or higher, such as ZrO, is used. In this case, by employing a gas flow sputtering method according to the present invention, a dynamic film formation rate of 30 to 150 nm · m / min is achieved. High-speed film formation can be performed.

<Low refractive index transparent film>
When the low refractive index transparent film is formed by the gas flow sputtering method, Si and / or Al is used as a target. it can.
Sputtering pressure: 10-100 Pa
Sputter power density: 1-35 W / cm ²
Argon: 0.5-30 SLM
Reactive gas: 0 to 120 sccm
Substrate temperature: room temperature

Usually, the low refractive index transparent film is made of a low refractive index material having a refractive index of 1.6 or less, such as SiO ₂ , MgF ₂ , Si ₃ N ₄ , Al ₂ O ₃ . By employing the gas flow sputtering method, high-speed film formation with a dynamic film formation speed of 30 to 300 nm · m / min can be performed.

  In particular, in forming the low refractive index transparent film, by increasing the input power and increasing the film forming pressure, a void is formed at a high film forming speed of 150 to 300 nm · m / min, It is possible to further reduce the refractive index of the formed low refractive index transparent film.

  Note that when forming each of the above layers by the gas flow sputtering method, it is also possible to form a composite oxide layer using two or more types of targets. Each layer can be a multilayer film of two or more materials.

  Next, specific configurations of the antireflection film and the optical filter of the present invention will be described with reference to FIGS.

  In the optical filter 10 of FIG. 2, an antireflection film 5 composed of a hard coat layer 2, a high refractive index transparent film 3 and a low refractive index transparent film 4 is formed on one surface of a transparent substrate 1, and the other side. The adhesive layer 6 is formed on the surface.

  An optical filter 10A shown in FIG. 3 is an antireflection film comprising a hard coat layer 2 on one surface of a transparent substrate 1 and alternating laminated films of high refractive index transparent films 3A and 3B and low refractive index transparent films 4A and 4B. 5A is formed.

  In the present invention, the transparent substrate 1 includes glass such as alkali silicate glass, non-alkali glass, and quartz glass, polyester, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfide (PES), Triacetyl cellulose (TAC), polybutylene terephthalate, polymethyl methacrylate (PMMA), acrylic, polycarbonate (PC), polystyrene, triacetate, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyethylene, ethylene-vinyl acetate copolymer And a transparent film made of an organic material such as polyurethane and cellophane.

  The thickness of the transparent substrate 1 is appropriately determined depending on required characteristics (for example, strength and thin film properties) depending on the use of the obtained optical filter, and is usually in the range of 1 μm to 10 mm.

  The hard coat layer 2 can be formed by coating a normal hard coat material such as an acrylic resin or a silicone resin. The hard coat layer 2 may have an ultraviolet cut property. In this case, the hard coat layer may be coated with a hard coat material mixed with about 0.05 to 5% by weight of a known ultraviolet absorber. Can be formed. The thickness of the hard coat layer 2 is preferably about 1 to 20 μm.

  The preferred thickness of the high refractive index transparent film and low refractive index transparent film constituting the antireflection film varies depending on the film configuration, film type, and center wavelength in order to reduce the reflectance in the visible light region due to light interference. However, as shown in FIG. 2, in the case of the two-layer structure of the high refractive index transparent film 3 and the low refractive index transparent film 4, the film thickness of the high refractive index transparent film 3 is 50 to 80 nm. 4 is preferably 85 to 120 nm. In the case of a four-layer structure as shown in FIG. 3, the high refractive index transparent film 3A (first layer) on the transparent substrate 1 side is 5 to 50 nm, and the low refraction is low. The refractive index transparent film 3A (second layer) is 5 to 50 nm, the high refractive index transparent film 3B (third layer) is 50 to 150 nm, and the low refractive index transparent film 3B (fourth layer) is about 50 to 150 nm. Preferably formed.

  The antireflection film is not limited to the configuration shown in FIGS. 2 and 3, and other layers having only one low refractive index transparent thin film, or a multilayer having a low refractive index transparent thin film and a high refractive index transparent thin film. Those laminated on can also be used.

  As the pressure-sensitive adhesive (pressure-sensitive adhesive) of the pressure-sensitive adhesive layer 6, thermoplastic elastomers such as acrylic, SBS, and SEBS are preferably used. To these pressure-sensitive adhesives, tackifiers, ultraviolet absorbers, colored pigments, colored dyes, anti-aging agents, adhesion-imparting agents, and the like can be appropriately added. The thickness of the adhesive layer 6 is preferably about 10 to 1000 μm. An appropriate release paper (film) (not shown) is attached to the adhesive layer 6.

  2 and 3 are diagrams showing an example of the optical filter of the present invention, and the present invention is not limited to the illustrated one as long as the gist thereof is not exceeded.

  For example, in the optical filter of the present invention, a transparent conductive film, a near-infrared cut film, an antifouling film and the like may be formed in addition to the antireflection film.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

  In the following, the PET film used as the substrate is one in which a hard coat layer made of an acrylic resin having a thickness of 5 μm is formed on one surface of a PET film having a thickness of 188 μm.

  Further, the refractive index of the formed transparent film was determined by an ellipsometer.

Example 1
Using the gas flow sputtering apparatus shown in FIG. 1, a PET film is set as a substrate in the chamber, exhausted to 1 × 10 ⁻¹ Pa with a roughing pump (rotary pump + mechanical booster pump), and then transparent with a high refractive index. A film (TiO ₂ film), a low refractive index transparent film (SiO ₂ film), a high refractive index transparent film (TiO ₂ film), and a low refractive index transparent film (SiO ₂ film) are laminated in this order to form a multilayer of 4 layers. An antireflection film made of a film was formed to produce the optical filter shown in FIG.

  In order to obtain a target film thickness, a multilayer film was manufactured by adjusting the substrate moving speed.

Specific film forming conditions were as shown in Table 1 below, and other conditions were as follows. The refractive indexes of the formed transparent films were as shown in Table 1.
・ Target dimensions: 80mm x 160mm x 5mmt
・ Cathode shape: Parallel plate facing type (using two of the above targets, distance 30 mm)
-Substrate position: 50mm distance between the upper end of cathode and substrate

Example 2
In Example 1, except that the power input to the target was increased at the time of film formation of the low refractive index transparent film of the fourth layer, the film formation pressure was increased, and high speed film formation was performed under the conditions shown in Table 2 below. An optical filter was produced in the same manner as in Example 1.

  Specific film forming conditions were as shown in Table 2 below. The refractive index of each formed transparent film was as shown in Table 2.

Comparative Example 1
Using an ordinary magnetron sputtering apparatus, an optical filter having a film configuration similar to that of Example 1 was manufactured.

A PET film is set as a substrate in a vacuum chamber, exhausted to 1 × 10 ⁻¹ Pa with a roughing pump (rotary pump + mechanical booster pump), then exhausted to 1 × 10 ⁻⁴ Pa with a turbo molecular pump, A four-layer multilayer film was formed. Note that the substrate moving speed was adjusted in order to obtain the desired film thickness.

Specific film forming conditions were as shown in Table 3 below, and other conditions were as follows. The refractive index of each formed transparent film was as shown in Table 3.
・ Target dimensions: 125mm x 500mm x 5mmt
・ Cathode shape: Planar type magnetron, installed facing the substrate in parallel ・ Substrate position: Distance to target substrate 80mm

  As a result, the following was confirmed.

  That is, the film formation speed is low in the normal sputtering method, and even if the film is formed with the same input power density as in the gas flow sputtering method, the substrate moving speed is low and a film with a large film thickness is formed. The film cannot be thickened without passing through the cathode several times. On the other hand, according to the present invention, high-speed film formation is possible by employing the gas flow sputtering method.

In particular, in Example 2 in which the film formation conditions of the low refractive index transparent film of the fourth layer (the outermost layer) were changed to high power input and high film formation pressure, the refractive index of the formed SiO ₂ film further decreased, As a result, it was revealed that the antireflection performance was further improved, and an optical filter superior in antireflection performance was obtained compared to that of Example 1.

FIG. 1A is a schematic diagram showing a schematic configuration of a gas flow sputtering apparatus suitable for carrying out the present invention, and FIG. 1B shows a target and back plate configuration of FIG. 1A. It is a perspective view. It is typical sectional drawing which shows the structural example of the optical filter of this invention. It is typical sectional drawing which shows the other structural example of the optical filter of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Hard-coat layer 3, 3A, 3B High refractive index transparent film 4, 4A, 4B Low refractive index transparent film 5, 5A Antireflection film 10, 10A Optical filter 12 DC power supply 13 Anode 14 Backing plate 15 Target 16 Substrate 20 Chamber

Claims (9)

  An antireflection film formed by a gas flow sputtering method.   2. The antireflection film according to claim 1, comprising a laminated film of a high refractive index transparent film and a low refractive index transparent film.   3. The antireflection film according to claim 2, wherein at least the low refractive index transparent film is formed by gas flow sputtering. According to claim 2 or 3, the high-refractive-index transparent film ITO, ZnO, _TiO 2, Al-doped _{ZnO, SnO 2, In 2 O} 3, Nb 2 O 5, Ta 2 O 5, Ga -doped ZnO, TiN, or An antireflection film comprising ZrO. 5. The antireflection film according to claim 2, wherein the low refractive index transparent film is made of SiO ₂ , MgF ₂ , Si ₃ N ₄ , or Al ₂ O ₃ .   6. The antireflection film according to claim 2, wherein the laminated film is an alternating laminated film of a high refractive index transparent film and a low refractive index transparent film.   An optical filter, wherein the antireflection film according to any one of claims 1 to 6 is formed on a transparent substrate.   8. The optical filter according to claim 7, further comprising a hard coat layer between the transparent substrate and the antireflection film.   9. The optical filter according to claim 7, wherein the uppermost layer of the antireflection film is a low refractive index transparent film having a low density.

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