KR20000047951A - Anti-reflection film and display device - Google Patents

Abstract

PURPOSE: An anti-reflection film and display device is provided which can adjust a light transmissivity at the wide range and has an intended view quality. CONSTITUTION: An anti-reflection film has multi-layered structure which plural films are piled on base thereof. The anti-reflection film comprises a first light absorption film consisted of at least one kind chosen among a metal film, a metal nitride film and a metal oxide film; a second light absorption film consisted of at least one kind chosen from a group consisted of a metal film, a metal nitride film and a metal oxide film; an induced film having a refractive index within the range of about 1.4 to 1.9. The induced film is located between the first light absorption film and the second absorption film.

Description

Anti-reflection film and display device {ANTI-REFLECTION FILM AND DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film and a display device, and more particularly to an antireflection film for preventing reflection of external light and a display device formed on the surface of a panel member for displaying an image.

When viewing an object through a transparent material such as a spectacle lens, when the intensity of the reflected light becomes strong, a phenomenon called ghost or flare occurs, which is a clearly reflected reflected image.

On the other hand, ordinary window glass or shovel window glass causes an in-glass image phenomenon in which ambient light, for example, sunlight or illumination light, is caused by specular reflection from the window glass. Such in-glass image development may lower the transparency of the window glass. In order to prevent this, attempts have been made on the base to form an antireflection film having a difference in refractive index from the base by a vacuum deposition method or the like. In this case, as is well known, in order to maximize the antireflection effect, it is important to properly select the thickness of the coating formed on the base. For example, for monolayer coatings, the minimum reflectance, i.e. the maximum transmittance of the coating, is determined by selecting the optical film thickness of the coating material, which is lower than the refractive index of the base material, at 1/4 (or odd multiples) of the target wavelength. Can be done. It should be noted that the optical film thickness of the coating material is given by the product of the refractive index of the coating material and the film thickness of the coating material. The anti-reflection film can be constructed by laminating a plurality of layers on the base. Regarding the antireflection film having a multilayer structure, various techniques related to the selection of the thickness of each layer are described, for example, in "Optical Technique Contact", Vol. 9, No. 8, page 17, 1971. The coating constituting the antireflection film mainly consists of an inorganic oxide or an inorganic halide, and has a low reflectance and a high transmittance in the visible light region.

Even in a display device such as a brown tube or a liquid crystal display device, an image may be opaque due to reflection of external or irradiated light on the screen, and in most cases, an anti-reflection film for preventing such surface reflection may display an image. It is formed on the surface of the panel base for. On the other hand, in the display device, depending on its structure or application, the light transmittance of the panel base should be adjusted within the range of 20 to 92% in order to improve the contrast. For example, when a panel base such as a panel glass for brown tubes or an acrylic resin is formed on the surface of a transmissive projector (rear projector), the light transmittance is adjusted by changing the light transmittance of the panel base itself.

However, the image display panel base serves to maintain the mechanical strength of the display device. In other words, when the display device is expanded, the panel base should be thick. In order to change the light transmittance of the panel base formed to such a thickness, it is necessary to prepare various kinds of panel bases whose transmittances are changed by changing the grade of the dye or the concentration of the pigment.

Moreover, with regard to the panel glass as the panel base for the brown tube, the center part is thin and the end part is thick to ensure sufficient mechanical strength. As a result, when adjusting the light transmittance of the panel glass by changing the light transmittance of the panel glass itself, there arises a problem that the light transmittance at the center portion is different from the light transmittance at the end portion. In particular, with respect to recent brown tubes with an image display screen having a nearly flat surface, the difference in light transmittance between the center and the end becomes larger because the center is made thinner and the end is thicker to increase the mechanical strength. .

One type of heat shield film component utilizing an optical thin film is configured such that the light absorbing film is formed of a metal thin film for controlling light transmittance. Specific examples of the material for forming the light absorbing film may include Au, Pt, Ni-Cr, Al, In ₂ O ₃ -SnO ₂ , CuI, and CuS. Such hot ray shielding films preferably have a visible light transmittance in the range of 60 to 90%. Specific examples using the light absorbing film such as the antireflection film may include a dark mirror, a selective absorbing mirror or an augmented absorbing mirror. As the antireflection film in the visible light region, a configuration called "dark mirror" can be used. For example, a double layer dark mirror in which a light absorbing film is combined with a dielectric film is described in "Optical Thin Film User Handbook", page 160. Japanese Patent Laid-Open No. 9-9-156964 discloses a technique in which a metal nitride film made of TiN, ZrN or HfN can be used as a light absorbing film to obtain a low reflectance in a wide visible light region. U. S. Patent No. 5,091, 244 discloses an antireflection film having a four to six layer structure in which a light transmittance can be controlled using a metal or metal nitride film as a light absorbing film while keeping the reflectance low in the visible light region.

However, a problem arises when a material suitable for forming the aforementioned light absorbing film is used as part of the antireflection film. For example, in the technique disclosed in Japanese Patent Laid-Open No. 9-156964, the light reflectance from the surface of the panel base is sufficiently low, but the light reflectance from the inner surface of the panel base is as high as 5 to 10%. In the display device, the light reflectance from the inner surface of the panel base causes a double vision (or ghost) of the character or image or darkens the contour of the character or image, thereby significantly reducing the image quality. In the antireflection film disclosed in US Pat. No. 5,091,244, there is disclosed a method of reducing the reflection of light from the surface while controlling the light transmittance, but reducing the light reflection from the inner surface of the panel base, which is an important problem of the display device as described above. No irradiation was made, and as a result, the light reflectance from the inner surface of the panel base is as high as 8 to 20%.

When the light transmittance of the panel base for the brown tube is as low as 35 to 60%, the light reflectance from the inner surface of the panel base is so much because the reflected light penetrates the panel base and the reflected light from the inner surface is attenuated three times. Does not cause problems In contrast, when the light transmittance of the panel base for the brown tube is 60% or more, for example, the grade "clear" (transmittance: 75% or more) or the grade "gray" specified in EIAJ ED-2138. In the case of using a panel base exhibiting (transmittance: 60-75%), light reflection from the inner surface of the panel base causes a problem that cannot be ignored.

SUMMARY OF THE INVENTION An object of the present invention is to provide an antireflection film capable of adjusting light transmittance in a wide range and a display device having desired image quality.

According to the present invention, in order to solve the above-described problem, there is provided an antireflection film having a multilayer structure in which a plurality of thin films are stacked on a base, wherein the thin films are at least selected from the group consisting of a metal film, a metal nitride film and a metal oxide film. A first light absorbing film made of one kind; A second light absorbing film made of at least one kind selected from the group consisting of a metal film, a metal nitride film and a metal oxide film; And a dielectric film having a refractive index in a range from about 1.4 to about 1.9, wherein the dielectric film is disposed between the first light absorbing film and the second light absorbing film.

According to the present invention, there is provided a display device in which an antireflection film is formed on a surface of a panel base for displaying an image, wherein the antireflection film is

A first light absorbing film made of at least one kind selected from the group consisting of a metal film, a metal nitride film and a metal oxide film; A second light absorbing film made of at least one kind selected from the group consisting of a metal film, a metal nitride film and a metal oxide film; And a dielectric film having a refractive index in a range from about 1.4 to about 1.9, wherein the dielectric film is disposed between the first light absorbing film and the second light absorbing film. In this display device, the panel base preferably has a light transmittance within a range of 60% or more.

Other objects and advantages of the present invention will become apparent by reading the following detailed description and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the difference between light reflection from a surface and light reflection from an inner surface in accordance with a change in refractive index of a dielectric film formed between two light absorption films of an antireflection film of the present invention.

The panel base for display apparatus consists of a glass material or a synthetic resin material. Specific examples of the glass material may include soda glass, lead glass, hard glass, quartz glass, and liquid crystal glass. For the brown tube, silicate glass containing strontium or barium is preferably used, and alkali less glass is preferably used as the liquid crystal display.

As the synthetic resin material for forming the panel base, any kind of organic high polymer material can be used. However, from the viewpoint of optical properties such as transparency, refractive index and dispersion and other properties such as impact force, heat resistance and durability,

(Meth) acrylic resins such as polymethylmethacrylate, or copolymers of methylmethacryl and vinyl monomers such as alkyl (meth) acryl or styrene; Polycarbonate resins such as polycarbonate, or diethylene glycol biseli carbonate (CR-39); Thermosetting (meth) acrylic resins or homopolymers or copolymers of urethane-modified (brominated) bisphenol A-mono (meth) acryl, such as homopolymers or copolymers of (brominated) bisphenol A-type di (meth) acrylics; Polyesters, in particular polyethyleneterephthalate, polyethylenenaphthalate or unsaturated polyesters; Acrylonitrilestyrene copolymers; Polyvinyl chloride; Polyurethane; Or it may be preferable to use an epoxy resin. In addition, aramid resins can be used from the viewpoint of heat resistance. The film-shaped base can be prepared by drawing the above-mentioned synthetic resin material or by diluting the above-described synthetic resin material in a solvent, applying the diluted material to the film form and drying it. The thickness of a film base is generally within the range of 25-500 micrometers.

If the panel base for the display device is formed of a synthetic resin material, the surface of the panel base is Japanese Patent Publication Nos. 50-28092, 50-28446, 51-24346, 52-112698 and 57-2735. It may also be coated with a coating material, such as the hard coat disclosed in. In addition, various properties such as adhesion, strength, chemical resistance, durability, and dye affinity for a panel base made of a synthetic resin material can be improved by providing an inorganic coating material as an underlayer of the antireflection film. The thickness of the hard cord is generally within the range of about 3-20 μm. Furthermore, the panel base for display device may be colored with a pigment such as carbon black or dye. In this case, as disclosed in Japanese Patent Application Laid-Open No. 7-36044, the panel base so colored can provide a specific wavelength as a selective absorption filter that selectively absorbs light.

The antireflection film including the light absorbing film may be formed by a physical vapor deposition (PVD) process, an ion implantation process, or a sputtering process, which is represented by a vacuum deposition process. Specific examples of materials suitable for forming the light absorption film by the PVD process include Au, Pt, Pd, Fe, Fe-Ni, Ni-Cr, Ni-V, Al, Ag, Cr, Fe-Cr, Cu, Ti, Zr And metals such as Hf and nitrides and oxides thereof. Moreover, specific examples of the material for forming the dielectric film include SiO ₂ , SiO, Si ₃ N ₄ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Ta ₂ O ₅ , TaHf ₂ , TiO, Ti ₂ O ₃ , HfO ₂ , Inorganic oxides and inorganic nitrides such as ZnO, In ₂ O ₃ , In ₂ O ₃ / SnO ₂ , Y ₂ O ₃ , Yb ₂ O ₃ , Sb ₂ O ₃ , MgO and CeO ₂

An oxide barrier layer for preventing oxidation of the light absorbing film may be inserted in the antireflection film, as disclosed in Japanese Patent Laid-Open Nos. 59-165001 and 9-156964. Specific examples of the material for forming the oxide barrier layer described above may include metal nitrides such as Si ₃ N or AlN and various metals.

Since the oxide barrier layer is unnecessary from an optical point of view, the thickness of the oxide barrier layer is preferably in the range of 20 μm or less in order to prevent the deterioration of the antireflection property. In addition, as disclosed in US Pat. No. 2,628,927 and Japanese Patent Publication No. Hei 3-81121, when the panel base is made of a synthetic resin material, a film of metal oxide such as SiO ₂ or metal sulfide has an adhesive force between the panel base and the antireflective film. It can be formed extremely thin as the first layer of the anti-reflection film for improving the efficiency.

According to the aforementioned means, it is possible to provide an antireflection film having a desired antireflection property with a minimum number of layers. In the display device in which such an anti-reflection film is formed on the surface of the panel base for image display, the light transmittance can be adjusted in a wide range without having to prepare various panel bases whose light transmittance changes as in the prior art. In addition, in the display device, since a single light transmittance can be obtained on the entire surface of the panel base for displaying an image regardless of the mechanical strength of the display device, ghost or ghost due to light reflection from the inner surface of the panel base. Good image quality can be guaranteed without the occurrence of flare.

The present invention is applicable to an antireflection film having a multilayer structure in which a plurality of thin films are formed on a base, and a display device in which an antireflection film is formed on a surface of a panel base for displaying an image. Subsequently, an example using an antireflection film formed on the surface of the panel base represented by the panel glass for brown tube ("clear" glass specified under EIAJ H-8601) will be described. In addition, the thickness of the center part of the display play of panel glass is 12 mm. It should be noted that the present invention is of course not limited thereto.

Example 1

In this embodiment, the brown tube panel glass formed on, and then the four films, TiN of the first light-absorbing film having a thickness of 10nm, an Al ₂ O ₃ having a thickness of 82nm (refractive index: about 1.7) for a dielectric film, a thickness of 12nm Since the second light absorption film of TiN and the dielectric film of SiO _{2 having} a thickness of 90 nm are sequentially formed, a four-layer antireflection film is obtained.

Comparative Example 1

In comparison, since the following four films were formed on the panel glass for the brown tube, the first light absorbing film of TiN having a thickness of 10 nm, and the dielectric film of SiO ₂ (refractive index: about 1.4) having a thickness of 87 nm, two-layer reflection A prevention film is obtained. In this comparative example, the second light absorbing film is not formed.

Comparative Example 2

In the comparative example, on the panel glass for the brown tube, the following four films, the first light absorbing film of TiN having a thickness of 19.9 nm, the dielectric film of TiO ₂ (refractive index: about 2.6) having a thickness of 30 nm, and the TiN having a thickness of 6.7 nm Since the second light absorption film and the dielectric film of SiO _{2 having} a thickness of 82.2 nm are sequentially stacked, an antireflection film is obtained. In this comparative example, the refractive index of the dielectric film formed between the first and second absorbing films is 1.9 or more.

The results of simulating the antireflection films of Example 1 and Comparative Examples 1 and 2 using a computer are shown in Table 1. As the composite refractive index of the film material used for the simulation, the values obtained based on the relationship of the composite refractive index = (n-ik) and the values shown in Table 2 were used. Note that k must be zero for dielectric materials.

Light reflectance from the surface (visual reflectance) Light reflectance from the inner surface (visual reflectance) Transmittance (wavelength: 546nm) Example 1 0.1% 0.8% 53% Comparative Example 1 0.1% 6.6% 75% Comparative Example 2 0.1% 16.8% 48%

Membrane material Composite refractive index wavelength 450 nm 550 nm 650nm TiN Refractive index (n) 2.00 1.75 1.70 TiN Extinction coefficient (k) 0.95 1.20 1.67 Al ₂ O ₃ Refractive index (n) 1.67 1.67 1.67 SiO ₂ Refractive index (n) 1.46 1.46 1.45

As is apparent from Table 1, with the antireflection film obtained in Example 1, the visual reflectance of the light reflected from the surface was 0.1%, the visual reflectance of the light reflected from the inner surface was 0.8%, and the transmittance of the light having a wavelength of 546 nm was 53. %to be. These results meet the requirements of the display device. In contrast, for the antireflection films obtained in Comparative Examples 1 and 2, the visual reflectance of the light reflected from the surface was lower than 0.1%, but the visual reflectance of the light reflected from the inner surface was as high as 6.6% in Comparative Example 1 and the comparative example. In 2 it is as high as 16.8%. These results do not meet the requirements of the display device.

1 is a graph showing the relationship between the refractive index and the luminance reflectance of the dielectric material forming the dielectric film of the antireflection film. More specifically, on the transparent glass as the panel base, the following four layers, the first light absorbing film of TiN having a thickness of 10 nm, the dielectric film (1/4 wavelength film), the light absorbing film of TiN having a thickness of 12 nm, and the thickness A dielectric film of SiO _{2 having} a thickness of 90 nm is sequentially stacked to form an antireflection film. With respect to such an antireflective film, the visual reflectance of the light reflected from each of the surface and the inner surface is calculated as the refractive index of the dielectric material of the dielectric film taken as a parameter.

The reflectance of light reflected from each of the surface and inner surface of the panel base made of glass material or synthetic resin material is within the range of about 4 to 6%. Criteria for determining the antireflection effect required for the display device are specified under the European standard TUV. In order to meet such standards, the visual reflectance must be suppressed to a value of 2% or less (see Television Society Technical Report, Vol. 19, No. 2, 1995). Even in the simulation results described above, the refractive index of the dielectric film is in the range of 1.4 to 1.9, preferably 1.5 to 1.8, so that both the light reflectance from the surface and the light reflectance from the inner surface are simultaneously placed within the range of 2% or less. It should be within the range of.

The present invention can provide an antireflection film having a desired antireflection function with a minimum number of layers. A display device in which an antireflection film is formed on a surface of a panel base for displaying an image has the following effects.

(1) The light transmittance can be adjusted in a wide range without having to prepare various kinds of panel bases whose light transmittance is changed as in the prior art.

(2) Desired image quality can be ensured without generation of ghosts or flares due to light reflection from the inner surface of the panel base.

(3) A uniform light transmittance can be obtained on the entire surface of the panel base for displaying an image regardless of the mechanical strength of the display device.

While the preferred embodiments of the present invention have been described using specific terminology, such description is for illustrative purposes only and it will be appreciated that changes and modifications may be made without departing from the scope of the appended claims and the spirit.

Claims (9)

In the anti-reflection film having a multilayer structure in which a plurality of thin films are stacked on a base, A first light absorbing film selected from the group consisting of metals, metal nitrides and metal oxides; A second light absorbing film selected from the group consisting of metals, metal nitrides and metal oxides; And A dielectric film having a refractive index in the range of about 1.4 to about 1.9; And the dielectric film is disposed between the first light absorbing film and the second light absorbing film. The method of claim 1, wherein the metal of the first light absorption film is Au, Pt, Pd, Fe, Fe-Ni, Ni-Cr, Ni-V, Al, Ag, Cr, Fe-Cr, Cu, Ti, Zr and An antireflection film comprising a metal, a metal nitride and a metal oxide selected from the group consisting of Hf. The method of claim 1, wherein the metal of the second light absorption film is Au, Pt, Pd, Fe, Fe-Ni, Ni-Cr, Ni-V, Al, Ag, Cr, Fe-Cr, Cu, Ti, Zr and An antireflection film comprising a metal, a metal nitride and a metal oxide selected from the group consisting of Hf. The method of claim 1, wherein the dielectric layer is formed of SiO ₂ , SiO, Si ₃ N ₄ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Ta ₂ O ₅ , TaHf ₂ , TiO, Ti ₂ O ₃ , HfO ₂ , ZnO, An antireflection film comprising a material selected from the group consisting of In ₂ O ₃ , In ₂ O ₃ / SnO ₂ , Y ₂ O ₃ , Yb ₂ O ₃ , Sb ₂ O ₃ , MgO and CeO ₂ . In the display device in which the antireflection film was formed on the surface of the panel base for image display, The anti-reflection film A first light absorbing film selected from the group consisting of metals, metal nitrides and metal oxides; A second light absorbing film selected from the group consisting of metals, metal nitrides and metal oxides; And A dielectric film having a refractive index in the range of about 1.4 to about 1.9; And the dielectric film is disposed between the first light absorbing film and the second light absorbing film. The display device of claim 2, wherein the panel base has a light transmittance in a range of 60% or more. The metal of the first light absorbing film is Au, Pt, Pd, Fe, Fe-Ni, Ni-Cr, Ni-V, Al, Ag, Cr, Fe-Cr, Cu, Ti, Zr and A display device comprising a metal, a metal nitride and a metal oxide selected from the group consisting of Hf. The metal of the second light absorption film is Au, Pt, Pd, Fe, Fe-Ni, Ni-Cr, Ni-V, Al, Ag, Cr, Fe-Cr, Cu, Ti, Zr and A display device comprising a metal, a metal nitride and a metal oxide selected from the group consisting of Hf. The method of claim 5, wherein the dielectric film is SiO ₂ , SiO, Si ₃ N ₄ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Ta ₂ O ₅ , TaHf ₂ , TiO, Ti ₂ O ₃ , HfO ₂ , ZnO, A display device comprising a material selected from the group consisting of In ₂ O ₃ , In ₂ O ₃ / SnO ₂ , Y ₂ O ₃ , Yb ₂ O ₃ , Sb ₂ O ₃ , MgO and CeO ₂ .