JP2007291475A - Cut filter for near ir ray, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cut filter for near IR rays suppressing the absorption of light in a visible light region and having excellent spectral characteristics. <P>SOLUTION: In the method for producing a cut filter for near IR rays in which low reflective index films and high reflective index films are alternately stacked on a substrate, the respective films are formed by magnetron sputtering, and oxygen is fed to an electron cyclotron resonance type ion source and an assist ion source, while plasma is excited so as to oxidize the films. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a near-infrared cut filter used for a front panel filter for protecting an internal glass substrate for optical use, communication using near infrared rays, remote control use, displays, and plasma displays.

Conventionally, a filter that selectively absorbs the near-infrared region is used in, for example, a cover of a semiconductor light-receiving element used in an automatic exposure meter of a camera, a plasma display, and the like, such as a light emitting part of a remote control device of a household appliance.
Regarding this filter, for example, Patent Document 1 proposes that a low refractive index film and a high refractive index film are alternately formed on a substrate such as a resin by sputtering.
However, when a film is formed by sputtering, the film is not sufficiently oxidized, and even the light in the visible light region is absorbed, so that there is a problem that sufficient spectral characteristics cannot be obtained as a near infrared cut filter. It was. In addition, when the substrate is made of a resin, there is a problem that distortion or the like occurs depending on the thickness of the substrate and cannot be practically used.

JP 2003-121636 A

  Therefore, an object of the present invention is to provide a near-infrared cut filter that suppresses absorption of light in the visible light region and has excellent spectral characteristics. Moreover, it aims at providing the near-infrared cut filter which suppressed the distortion of the resin substrate.

In order to solve the above-mentioned problems, the present inventors have intensively studied, and at the time of magnetron sputtering, an electron cyclotron resonance (hereinafter referred to as ECR) ion source is used as a main acid source, assist ions. Based on the knowledge that if the source is used as an auxiliary oxidation source, the laminated film can be sufficiently oxidized, the following solution has been found.
That is, the method for producing a near-infrared cut filter according to the present invention is a method for producing a near-infrared cut filter in which a low refractive index film and a high refractive index film are alternately laminated on a substrate as described in claim 1. Then, each of the films is formed by magnetron sputtering, oxygen is supplied to an electron cyclotron resonance ion source and an assist ion source, and plasma is excited to oxidize the films.
Further, the present invention according to claim 2 is the method for producing a near-infrared cut filter according to claim 1, wherein the films are respectively laminated on the front and back of the substrate, and the total film thickness on the surface (t ₁ ) , the absolute value of the difference between the back surface total thickness sum of _{(t 2) (Δ = |} t 1 -t 2 |) of the 15 with respect to the total thickness sum of value greater _{(t 1} or _{t 2).} The film is formed on a resin substrate having a thickness of 0.1 to 2.0 mm so as to be within 0%.
Moreover, the near-infrared cut filter of the present invention is a near-infrared cut filter in which a low-refractive index film and a high-refractive index film are alternately laminated on a substrate as described in claim 3. And the absolute value (Δ = | t ₁ −t ₂ |) of the difference between the total film thickness on the front surface (t ₁ ) and the total film thickness on the back surface (t ₂ ), The film is formed on a resin substrate having a thickness of 0.1 to 2.0 mm so as to be within 15.0% with respect to a large value (t ₁ or t ₂ ) of the total total film thickness.

  According to the present invention, it is possible to obtain a near-infrared filter excellent in spectral characteristics by enhancing the light transmittance in the visible light region by reliably oxidizing the optical thin film. Further, when the film is formed on the resin substrate, the distortion of the substrate can be suppressed. As a result, the near-infrared filter can be formed from a thin resin substrate, so that the applicable range can be expanded.

Next, an embodiment of the present invention will be described with reference to the drawings.
The vacuum apparatus whose cross section is shown in FIG. 1 is for producing the near-infrared cut filter of the present invention. A cylindrical rotating body 3 supporting a substrate 2 is disposed in the center of the cylindrical chamber 1, and a first magnetron sputtering apparatus 4, an ECR type ion source 5, an assist ion source are arranged along the inner periphery of the chamber 1. 6 and the 2nd magnetron sputtering apparatus 7 are arrange | positioned in order. The inside of the cylindrical chamber 1 is evacuated by a vacuum pump 10, 10 '.

The first and second magnetron sputtering apparatuses 4 and 7 form a film material on the substrate 2 by magnetron sputtering, and each apparatus is provided with a gas inlet 9 for introducing a sputtering gas. It has been. Further, two cathodes 11 each having a target attached so as to face the cylindrical rotating body 3 are disposed inside each of the devices 4 and 7. Each of these cathodes 11 is provided with a magnet (not shown) inside and connected to an AC power source (not shown) for applying an AC electric field to the target.
In addition, a shutter 12 is provided on the substrate 2 side of each device, and the shutter is selectively opened when the first or second sputtering device 4 or 7 is operated.

  The ECR ion source 5 is provided with an oxygen inlet 13 for introducing oxygen into the ECR ion source 5 and a magnetic circuit 14. In order to generate the microwave-excited plasma of ECR plasma from the magnetic circuit 14, a waveguide outside the vacuum layer and a microwave antenna inside the vacuum chamber are connected via a microwave introduction window (not shown). .

  The assist ion source 6 generates a plasma that is strongly ionized locally in order to cause an oxidation reaction. The assist ion source 6 is an ion beam irradiation ion source, a planar magnetron, or linear or inverse linear magnetron ions described in Japanese Patent No. 2501510. Source can be used. The assist ion source is provided with an oxygen inlet 15 for introducing oxygen therein, introduces oxygen around the substrate 2, generates reactive plasma, and oxidizes the film material.

  With the above configuration, a material constituting the low refractive index film is formed on the substrate 2 by the first magnetron sputtering apparatus 4, the cylindrical rotating body 3 is rotated, and the ECR ion source 5, the assist ion source 6, Is oxidized to form a low-refractive index film, and further, a material constituting the high-refractive index film is formed by the second magnetron sputtering apparatus 7 by rotating the cylindrical rotating body 2, and the ECR ion source 5 and assist ions are formed. The film is oxidized with the source 6 to form a high refractive index film, which is alternately repeated to form a multilayer film on the substrate 2 to obtain a near infrared cut filter.

  As described above, in the present invention, by using the assist ion source 6 in addition to the ECR ion source 5 as an oxidation source, absorption of visible light in the formed film can be suppressed, and the spectral characteristics are improved.

Next, another embodiment of the present invention will be described with reference to FIG.
The figure shows a state after film formation of a near infrared cut filter formed on both surfaces of the substrate 2. Absolute value (Δ = | t ₁ −t) of the difference between the total film thickness (t ₁ ) of the laminated structure 16 on the front surface side and the total film thickness (t ₂ ) of the laminated structure 17 on the back surface side ₂ |) is preferably set to 15.0% or less with respect to the larger value (t ₁ or t ₂ ) of the total total film thickness. Thereby, even if it is a case where it forms into a film on the resin-made board | substrates 2 of the range of thickness 0.1-2.0 mm, it is because the distortion of the board | substrate 2 can be suppressed.

  Substrates that can be used in the present invention are glass, polyester, polyethylene terephthalate, polybutylene terephthalate, polymethyl methacrylate, acrylic, polycarbonate, polystyrene, polyvinylidene chloride, polyethylene, ethylene-vinyl acetate copolymer, polyvinyl butyral, metal An ion-crosslinked ethylene-methacrylic acid copolymer, polyurethane, cellophane, or the like can be used. Among those exemplified, it is preferable to use acrylic, polycarbonate, PET, or the like. The thickness of the substrate may be a thickness that does not hinder transparency, and in the case of PET, it is generally 150 to 200 μm. This is because deformation of the resin substrate can be prevented even at 100 ° C. or lower.

The low refractive index film is not particularly limited as long as it has a refractive index of 1.5 or less, and examples thereof include silicon compounds such as SiO ₂ . The high refractive index film is not particularly limited as long as it has a refractive index of 2.0 or more. Examples thereof include niobium compounds such as Nb ₂ O ₅ and titanium compounds such as TiO ₂ .
In addition, there is no restriction | limiting in particular about film-forming conditions, What is necessary is just to sputter | spatter under film-forming pressure 0.20-0.35Pa as an example. The film forming rate can also be arbitrarily adjusted. For example, in the case of Nb ₂ O ₅ , 1.4 to 1.8 Å / s, and in the case of SiO ₂ , 1.7 to 2.2 Å / s. Etc.

Next, an embodiment of the present invention will be described.
By pressure of the vacuum chamber to 2.0 × ¹⁰ -3 Pa, introducing Ar at 300 sccm, and setting the cathode voltage to 17.5 kW, on one surface of a substrate made of acrylic 370 mm × 230 mm × 0.188 mm A Si film having a thickness of 1 nm was formed by magnetron sputtering.
Next, the inside of the vacuum chamber is adjusted to 2.4 × 10 ⁻³ Pa, Ar is introduced at 300 sccm, the cathode voltage is set to 11 kW, Nb is formed by magnetron sputtering, the ECR ion source and the assist are set. An Nb ₂ O ₅ film having a thickness of 11 nm was formed in combination with an ion source. The ECR ion source was introduced with oxygen at 350 sccm around it to generate plasma with a power of 3.6 kW (0.9 × 4). The assist ion source was composed of a linear electromagnetic tube, and oxygen was introduced around it at 85 sccm to generate plasma with a voltage of 1.6 kV.
Furthermore, the inside of the vacuum chamber was adjusted to 2.6 × 10 ⁻³ Pa, Ar was introduced at 300 sccm, the cathode voltage was set to 17.5 kW, Si was formed by magnetron sputtering, and an ECR ion source and A 28 nm-thick SiO ₂ film was formed in combination with the assist ion source. The ECR ion source was introduced with oxygen at 350 sccm around it to generate plasma with a power of 3.6 kW (0.9 × 4). The assist ion source was introduced with oxygen at 80 sccm around the assist ion source to generate plasma with a voltage of 1.75 kV.
This operation was repeated, and as shown in the left column (surface) of the table in FIG. 3, a film structure having a total of 37 layers was formed on the surface. The film thickness was adjusted by adjusting the sputtering time as described in the table.
Similarly, on the back surface of the substrate, a Si film having a thickness of 1 nm is formed by magnetron sputtering, an Nb ₂ O ₅ film having a thickness of 9 nm is formed thereon, and a SiO ₂ film having a thickness of 41 nm is formed thereon. As shown in the right column (rear surface) of the table in FIG. 3, a film structure having a total of 35 layers was formed on the surface.

Both the Nb ₂ O ₅ film and the SiO ₂ film formed by the above method were able to sufficiently oxidize the film, and a near infrared filter having the following excellent spectral characteristics could be obtained.

(Spectral characteristics)
a) λ: 430-620 nm: average transmittance 85.0% or more b) λ: 700-800 nm: average transmittance 2.0% or less c) λ: 800-1050 nm: average transmittance 4.0% or less d) half value (transmittance 50%) ): 650 ± 10nm
A graph of spectral characteristics is shown in FIG.

In addition, since the difference between the total film thickness on the surface of the near infrared filter and the total film thickness on the back surface is within 15% of the total film thickness on the back surface, distortion and curling of the substrate can be prevented. It was. Specifically, the total thickness (t ₁ ) on the front surface is 2261 nm, the total thickness (t ₂ ) on the back surface is 2595 nm, the layer thickness difference (| t ₁ −t ₂ |) is 334 nm, and t _Since t ₂ is large among ₁ or t ₂ , | t ₁ −t ₂ | / t ₂ = 334/2595 = 12.9%.
In addition, it was confirmed that if this value is within 15%, the distortion and curling of the substrate can be prevented.

  INDUSTRIAL APPLICABILITY The present invention can be used for optical applications, communication using near infrared rays, remote control applications, displays, front panel filters for protecting glass substrates for plasma displays, and the like.

Device sectional view for explaining the production method of the present invention Explanatory drawing which shows the relationship of the film thickness of each surface when film-forming on both surfaces The table | surface for demonstrating the film | membrane structure of the near-infrared cut off filter of one Example of this invention The graph which shows the spectral characteristics of one Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical chamber 2 Board | substrate 3 Cylindrical rotary body 4 1st magnetron sputtering apparatus 5 ECR type ion source 6 Assist ion source 7 2nd magnetron sputtering apparatus 9 Gas inlet 10, 10 'Vacuum pump 11 Cathode 12 Shutter 13 Oxygen Inlet 14 Magnetic circuit 15 Oxygen inlet 16 Laminated structure on the surface 17 Laminated structure on the back

Claims (3)

  A method of manufacturing a near-infrared cut filter in which a low refractive index film and a high refractive index film are alternately laminated on a substrate, each film being formed by magnetron sputtering, an electron cyclotron resonance ion source and an assist A method for producing a near-infrared cut filter, wherein oxygen is supplied to an ion source and plasma is excited to oxidize the film. The films are respectively laminated on the front and back of the substrate, and the absolute value (Δ = | t ₁ −t ₂ |) of the difference between the total film thickness on the front surface (t ₁ ) and the total film thickness on the back surface (t ₂ ). ) On a resin substrate having a thickness of 0.1 to 2.0 mm so as to be within 15.0% with respect to a large value (t ₁ or t ₂ ) of the total total film thickness. The manufacturing method of the near-infrared cut filter of Claim 1 characterized by the above-mentioned. A near-infrared cut filter in which low-refractive index films and high-refractive index films are alternately stacked on a substrate, wherein the films are stacked on the front and back of the substrate, respectively, and the total film thickness on the surface (t ₁ ) The absolute value (Δ = | t ₁ −t ₂ |) of the difference from the total film thickness (t ₂ ) on the back surface is set to 15.5 with respect to the large value (t ₁ or t ₂ ) of the total film thickness. A near-infrared cut filter, which is formed on a resin substrate having a thickness of 0.1 to 2.0 mm so as to be within 0%.

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