JP3320776B2 - Antireflection film and display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film for effectively preventing reflection of external light and a display device having the antireflection film, and more particularly to a two-layer antireflection film.

[0002]

2. Description of the Related Art Usually, window glasses, show windows,
Glass is used as a substrate for a display surface or the like of a display device. This glass may reflect ambient light, for example, sunlight or illuminating light, in a specular manner, so that a reflection phenomenon occurs, which often impairs transparency and the like. In particular, in the case of a display device, when specular reflection occurs on the display surface, an image to be displayed on the display surface overlaps a light source reflected from the surroundings, a surrounding scenery, and the like, causing significant image degradation.

Therefore, as a method of preventing this reflection,
Conventionally, there is a method in which a single-layer or multilayer optical film is formed on a substrate surface, and an anti-reflection film for preventing reflection of external light is formed by utilizing a light interference effect.

One of the anti-reflection films generally well known is a so-called quarter-wave film. The １ ／ wavelength film will be described as follows. That is, when external light reflection is prevented by a single-layer antireflection film, the refractive index of air is n ₀ and the refractive index of the thin film is n.
_1, n ₂ the refractive index of the substrate, when the film thickness of the thin film d, the wavelength of light to be prevented reflection lambda, must satisfy the following non-reflection conditions. In _{n 1 d = λ / 4 ...} (1) n 1 2 = n 0 n 2 above relationship, the thickness of the thin film is in the thickness of 1/4 of the wavelength of light to be prevented reflection From 1 /
It is called a four-wavelength film.

When the above two equations are satisfied, the reflection of light of wavelength λ can be made zero. However, when glass is used for the substrate, n ₂ is 1.52 and the refractive index n _{0 of} air is 1.00. from the refractive index n ₁ of the thin film is required to be 1.23. However, the currently known low-refractive-index substance that is practically usable is MgF _2, which has a refractive index of 1.38, which is larger than the refractive index under the non-reflection condition (n ₁ = 1.23). It was impossible to completely prevent the reflection of external light.

Therefore, the lower layer on the substrate side and the
A two-layer anti-reflection film consisting of an upper layer
It has also been used to prevent shooting. In this case, the air
Folding rate n₀ , The refractive index of the upper layer is n_Three , The refractive index of the lower layer is n
_Four , The refractive index of the substrate is n_Two And the thickness of the upper layer is d₁ , The underlying membrane
Thickness d_Two , Where λ is the wavelength of light to be prevented from being reflected
When, The following non-reflection conditions must be satisfied. n_Three d₁ = Λ /4  n_Four d_Two = Λ /4 ... (2) n_Two n_Three ^Two = N₀ n_Four ^Two 

From the above relational expression (1), when the substrate is a glass plate, since n ₂ = 1.52 and n ₀ = 1.00, the lower layer and the lower layer are arranged so that the refractive index ratio n ₄ / n ₃ becomes 1.23. You only have to select the material in the upper layer.

As the two-layer antireflection film, JP-A-61-1
[0043] Japanese Patent Application Laid-Open Publication No. 0043/1993 discloses a low-refractive-index film made of a condensate of an alkoxysilane or chlorosilane containing a polyfluoroalkyl group as a lower-layer film with a high-refractive-index film made of a co-condensate such as an alkoxide of Ti, Zr, or Si. The one used for the upper layer has been proposed.

Although such a two-layer antireflection film can prevent reflection at a specific wavelength, it cannot basically satisfy the non-reflection condition with light other than the specific wavelength. So as to satisfy the glass substrate for anti-reflective condition of the refractive index of 1.52, lower, combining the top layer of the refractive index, the spectral reflectance of the two-layer antireflection film when an attempt is made to prevent the reflection of light of the wavelength lambda ₀ Figure It is shown in FIG. In FIG.
Curve 1 shows the refractive index of the upper layer n ₃ = 1.55 and the refractive index of the lower layer n ₄ =
In the case of 1.91, the curve 2 represents the refractive index of the upper layer n ₃ = 1.45, the refractive index of the lower layer n ₄ = 1.78, and the curve 3 represents the refractive index n of the upper layer.
₃ = 1.38 and the refractive index n _{4 of the} lower layer = 1.70. FIG.
As shown in the figure, the reflectance characteristic has a relatively steep curve, and the antireflection region where the reflectance is smaller than that of the substrate itself is relatively narrow. Further, the lower the refractive index of the upper and lower layers, the wider the antireflection area becomes. However, as described above, the currently known and practically usable low refractive index material is MgF _2. Only the degree shown in curve 3 was obtained.

In order to prevent reflection in a wide band,
It is known that three or more antireflection films may be used instead of two-layer films. That is, since the thickness of the anti-reflection film is determined by the wavelength of light, the reflectance of N wavelengths can be reduced theoretically by using an N-layer multilayer film. However, increasing the number of layers of the antireflection film leads to an increase in the number of steps, a decrease in yield, an increase in cost, and the like, which is industrially difficult.

[0011]

As described above, the conventional two-layer antireflection film cannot obtain the antireflection effect only in a relatively narrow wavelength range. Then, in a region deviated from a specific wavelength for which reflection is to be prevented, the reflectivity may increase more than that of the substrate itself, causing glare. The tendency is particularly large on the short wavelength side,
In the case of the display surface of the display device, it causes blue glare.

The present invention has been made in view of the above problems, and has as its object to provide an antireflection film having a two-layer structure capable of preventing reflection in a wider area than the conventional one. Another object of the present invention is to provide a display device having such an antireflection film on a display surface.

[0013]

In order to solve the above-mentioned problems, the present invention provides a first thin film formed on a substrate and a second thin film formed on the first thin film. In the prevention film, the first thin film has an average particle size of 3 to 300.
When the wavelength containing the dye of nm and the wavelength at which the spectral reflectance of the antireflection film in the visible light region is minimum is λr and the wavelength at which the spectral transmittance is minimum is λt, λt−50 nm <λr < λt + 70 nm.

Further, on the outer surface of the light-transmitting display portion substrate,
In a display device provided with an antireflection film composed of a first thin film formed on a base and a second thin film formed on the first thin film, the first thin film has an average particle size of 3 to 30
When a wavelength containing a dye of 0 nm and having a minimum spectral reflectance in the visible light region of the antireflection film is λr, and a wavelength having a minimum spectral transmittance is λt, λt−50 nm <λr < λt + 70 nm.

[0015]

As a result of investigations by the inventors, it has been found that a specific spectral transmittance characteristic is given to the antireflection film by giving a predetermined spectral transmittance characteristic to the lower layer film of the two-layer antireflection film as compared with the conventional one. It has been found that the antireflection film has an antireflection effect over a wide band, particularly over a shorter wavelength region. That is, by making the wavelength at which the spectral transmittance of the antireflection film has a minimum in the visible region substantially coincide with the wavelength at which the spectral reflectance becomes a minimum, an antireflection film having an antireflection effect over a wider band can be obtained. In order to form an anti-reflection film having such spectral transmittance and spectral reflectance characteristics, an appropriate dye may be contained in a first thin film formed on a substrate, that is, a lower layer.

The conventional two-layer antireflection film has a wavelength-dependent spectral transmittance characteristic in both a first thin film as a lower layer formed on a substrate and a second thin film as an upper layer formed thereon. The spectral transmittance characteristic as a two-layer antireflection film is maximized at the wavelength at which the spectral reflectance is minimum,
The characteristics are completely opposite to those of the antireflection film according to the present invention.

This will be described with reference to FIGS. 2 and 3 show the spectral reflectance and the spectral transmittance of the antireflection film according to the present invention and the conventional antireflection film. FIG.
FIG. 2A shows the characteristics of the antireflection film having the minimum wavelength of the spectral reflectance of 570 nm. FIG. 2A shows the spectral reflectance, and FIG. 2B shows the spectral transmittance. Solid lines 10a and 10b show the characteristics of the antireflection film of the present invention, and broken lines 11a and 11b show the characteristics of the conventional antireflection film. Similarly, FIG. 3 shows the characteristics of an antireflection film having a minimum reflectance at 620 nm in comparison, and solid lines 20a and 20b show the present invention, and broken lines 21a and 21b show a conventional example. As shown in FIGS. 2 and 3, it can be seen that the present invention has an antireflection function over a wider band than the conventional antireflection film. 2 and 3, as an example of the antireflection film according to the present invention, the upper layer film is a SiO ₂ film obtained by hydrolysis and dehydration condensation of Si (OC ₂ H ₅ ) ₄ , and the lower layer film is Is Ti (OC
_This shows that a TiO ₂ —SiO ₂ film obtained by hydrolyzing and co-condensing ₃ H ₇ ) ₄ and Si (OC ₂ H ₅ ) ₄ contains a dye so as to have a predetermined spectral transmittance. . The refractive index of the upper layer is about 1.45, and the refractive index of the lower layer is about 1.8 without a dye. Further, the conventional antireflection film does not contain a dye.

The wavelength at which the spectral reflectance of the antireflection film is minimum depends on the thickness of the lower and upper layers of the antireflection film. FIG. 4 shows a change in spectral reflectance when the film thickness of the lower and upper layers of the antireflection film having the spectral transmittance characteristics shown in FIG. 2 is reduced, and the film thickness of the lower and upper layers is increased. FIG. 5 shows the change in the spectral reflectance when the measurement is performed.

In FIG. 4, a curve 12-1 indicates the optimum film thickness, and the wavelength at which the spectral transmittance and the spectral reflectance are minimized is 570.
In this case, the values are almost the same in nm. Curves 12-2 and 12-3
Are the wavelengths at which the spectral reflectance is minimum are 540 nm and 5 respectively.
20 nm. As can be seen from FIG. 4, even if the anti-reflection area is enlarged as compared with the conventional two-layer anti-reflection film having the lowest reflection at each wavelength, the difference between the spectral transmittance and the minimum wavelength of the spectral reflectance is small. The higher the value, the higher the minimum value of the reflectance. Although not shown, if the deviation is larger than this, the reflectance further increases. It should be noted that, even in the conventional two-layer antireflection film, if the reflectance is increased by lowering the refractive index of the lower layer, the region having the antireflection effect can be expanded. Curve 12-4 shows the lower layer refractive index 5
The graph shows the spectral transmittance of an antireflection film formed so that 20 nm is the minimum value of reflection. However, in the case of the antireflection film of the curve 12-4, the minimum reflectance increases with respect to the antireflection film having the minimum value of the reflection at 520 nm without changing the refractive index of the lower layer. ~ 700nm)
The antireflection characteristics are almost the same as 12-3. In other words, a similar effect can be sufficiently obtained with a conventional antireflection film as long as the reflectance is as low as about curve 12-3. further,
If the minimum wavelength of the reflectance deviates beyond the curve 12-3, the minimum value of the spectral reflectance of the antireflection film further increases, so that the use of the conventional antireflection film is more effective.

Therefore, the wavelength at which the spectral reflectance is minimum is 50 nm shorter than the wavelength at which the spectral transmittance is minimum.
It must not be shifted. In addition, since the minimum reflectance is preferably 20% or less as an antireflection effect, more preferably, the size of the deviation is 30 nm or less.

Similarly, in FIG. 5, the curve 12-5 is the optimum film thickness, and the curves 12-6 and 12-7 are the wavelengths at which the spectral reflectance is minimum are 610 nm and 640 nm, respectively. As in the case described above, as the difference between the spectral reflectance and the minimum wavelength of the spectral reflectance increases, the minimum value of the reflectance increases. Curve 12-8 is a conventional anti-reflection coating formed by lowering the refractive index of the lower layer so that 640 nm has the minimum value of reflection. The antireflection film of the curve 12-8 has almost the same antireflection characteristics in the visible region as the antireflection film of the curve 12-7. When the deviation of the minimum wavelength is increased beyond the curve 12-7, the minimum reflectance further increases, and the antireflection characteristics are deteriorated as compared with the conventional antireflection film.

Therefore, the wavelength at which the spectral reflectance is minimum is 70 nm longer than the wavelength at which the spectral reflectance is minimum.
It should not deviate by more than a degree. In addition, the minimum reflectance is 20%
In order to achieve the following, the shift is preferably 40 nm or less. As described above, the wavelength at which the spectral transmittance of the antireflection film is minimum is λt, and the wavelength at which the spectral reflectance is minimum is λr
In this case, it is desired that the relationship of (λt−50) nm <λr <(λt + 70) nm is satisfied. A more preferable range is (λt−30) nm <λr <(λt + 40) nm.

The reason why the antireflection film of the present invention can prevent reflection in a wider area than the conventional antireflection film is presumed to be as follows. That is, as described above, the two-layer antireflection film must satisfy the above expression (2). Therefore, when the substrate is glass having a refractive index of 1.52, the ratio of the refractive index of the lower layer to that of the upper layer needs to be 1.23. Practical and lowest refractive index MgF _{2 for} upper layer
Since the refractive index is 1.38 when is used, the refractive index of the lower layer must be 1.7. By the way, the relationship of the refractive index must be satisfied only at the specific wavelength λ for which reflection is to be prevented, and the refractive index does not need to be 1.7 at other wavelengths. In addition, in order to use a material with a higher refractive index than the substrate for the lower layer,
In a certain wavelength region, the provision of this anti-reflection film, on the contrary, increases the reflection. The antireflection film of the present invention,
The lower layer contains a dye, and the wavelength at which the spectral transmittance of the lower layer containing the dye is minimum substantially coincides with the wavelength at which the reflectance of the antireflection film of the antireflection film is minimum. The refractive index of such an underlayer film becomes maximum in the wavelength region where the transmittance becomes minimum. In this portion, the above-described ratio of the lower layer and the upper layer of 1.23 is satisfied, and the refractive index of the lower layer is not unnecessarily high in other wavelength regions. Therefore, it is considered that the antireflection effect is provided over a wider band without increasing the reflection even in a region other than the wavelength where the reflection is to be prevented.

The antireflection film according to the present invention has an effect regardless of the manufacturing method. However, the lower layer film containing a dye is composed of a film forming material such as a metal alkoxide and a solvent, a dye and, if necessary, a catalyst. It is simple to form by applying and drying the mixed solution. In addition, a method of forming the upper layer using such a metal alkoxide or the like is simpler than a method such as vapor deposition. Examples of the pigment include a dye and a pigment, and a pigment is particularly desirable.

As a material for forming a film, a metal alkoxide is mainly most suitable. The metal alkoxide is represented by the general formula M (OR) ₄ . Here, M is a metal element, and OR is an alkoxyl group. For example, Ti, Zr, Si, A
Alkoxides containing metal elements such as 1, Zn, Fe, Co, Ni, etc. can be used alone or in combination for each purpose. In order to form the lower layer film, it is preferable to increase the mixing ratio of alkoxides such as Ti, Zr, and Zn having a relatively high refractive index as a binder and increase the specific gravity of Si alkoxide as a material for forming the upper layer.
Further, it is also possible to use a polymer produced by the condensation of the metal alkoxide. Further, R of the alkoxyl group OR is preferably an alkyl group having 1 to 5 carbon atoms. That is, specifically, Ti (OC
_{2 H 5) 4, Ti (} OC 3 H 7) 4, Ti (OC
₄ H ₉ ) ₄ , Zr (OC ₂ H ₅ ) ₄ , Zr (OC
_{3 H 7) 4, Zr (} OC 4 H 9) 4, Si (OCH 3)
_{4, Si (OC 2 H 5} ) 4, Al (OC 2 H 5) 3, A
l (OC ₃ H ₇ ) ₃ , Al (OC ₄ H ₉ ) ₃ , Zn (O
Metal alkoxides such as C ₂ H ₅ ) ₂ and Zn (OC ₃ H ₇ ) ₂ , and those in which part of an alkoxy group is substituted with another functional group, for example, titanate coupling agent, silane coupling agent, Ti , Zr metal chelates, for example, Ti, Zr β-diketones (such as acetylacetonate), or mixtures thereof. Examples of the coupling agent include a silane coupling agent as shown in Table 1, a titanate coupling agent as shown in Table 2,
There is an aluminum-based coupling agent as shown in Chemical formula 1. It was also confirmed that the addition of these coupling agents to the lower layer further expanded the antireflection region of the antireflection film of the present invention.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

Embedded image

The above-mentioned metal alkoxide and the like are hydrolyzed,
A metal oxide film is formed on the substrate by a dehydration condensation reaction. Further, by mixing and applying a dye to the solution containing the metal alkoxide, a dye-containing thin film in which the dye is sealed in a metal oxide can be formed.

Further, alcohols are suitable as a solvent for dissolving the metal alkoxide. Since the viscosity of alcohol increases with an increase in the number of carbon atoms, alcohol may be appropriately selected in consideration of this point. Generally usable alcohols include alcohols having 1 to 5 carbon atoms.
As specific examples, almost all alcohols such as isopropyl alcohol, ethanol, methanol, butanol, pentanol, methoxyethanol, ethoxyethanol, propoxyethanol and butoxyethanol can be used.

The membrane obtained by the above-mentioned method is generally porous. Therefore, when a dye is used for the lower layer, when the upper layer is formed by the above-described method, the dye of the lower layer passes through the pores of the upper layer and elutes into the upper layer that has not been dried yet when the solution of the upper layer is applied. In some cases, it becomes difficult to control manufacturing conditions. In the case of a pigment, since it is larger than a dye, it does not pass through the pores in the lower layer. Of course, when the upper layer is formed by a method such as vapor deposition, such a problem does not occur. However, a pigment which can be easily applied to all methods, particularly, when a film is formed by this simple method is preferable.

As the pigment, an organic pigment is preferable because of its variety. The particle size of these pigments is preferably 300 nm or less in view of the transparency of the film. Generally, in order to obtain the transparency of the film, the particle diameter of the pigment is 1/2 or less of the wavelength λ, that is, 200 nm or less in the case of visible light. This is because when the particle size of the pigment is large, light scattering is caused and transparency tends to be impaired. In the present invention, since the pigment is confined inside the film, the difference in the refractive index between the pigment and the film material is smaller than the difference in the refractive index between the pigment and the air, so that transparency can be maintained up to a particle size of 300 nm. In order to prevent elution from the porous film and to have sufficient light resistance, it is preferable that the pigment has a particle size of 3 nm or more. More preferably,
The pigment particle size is between 5 and 200 nm.

Almost any pigment can be used as the dye. In organic pigments, for example, azo yellow, red pigments such as benzene yellow, carmine FB, etc., condensed pigments such as perylene, perilone, dioxazine, thioindigo, isoindolinone, quinophthalone, quinacridone,
And phthalocyanine pigments. Inorganic pigments include titanium white, red iron, graphite, cobalt blue and the like.
Of course, dyes other than these can also be used in the present invention.

It is desirable that the material forming the upper layer film has a relatively lower refractive index than that of the lower layer film. For example, a silicon oxide thin film can provide a sufficient antireflection effect. A substance such as fluoroalkylsilane may be added for the purpose of improving the strength. As long as the above properties are satisfied as a whole of the antireflection film, another substance can be added to the lower layer film or the upper layer film in an auxiliary manner. That is,
By mixing a hygroscopic metal salt, for example, LiNO ₃ , LiCl, or the like into the upper layer, the lower layer, or both of the antireflection film of the present invention, the antireflection film is given conductivity, thereby providing an antistatic function. be able to. Also, Sn
An antistatic function can be imparted by introducing fine particles of O ₂ and ITO into the upper layer, the lower layer, or both.

The antireflection film as described above is considered to be particularly effective when applied to a display device or the like. Therefore, it is important to more effectively prevent reflection of visible light. The wavelength at which the human eye perceives light most strongly, that is, the wavelength with high luminosity, is said to be 555 nm, but ambient light often has a distribution that is slightly longer at longer wavelengths in visible light. Therefore, in order to effectively prevent the reflection of ambient light, it is preferable to mainly prevent wavelengths between 550 nm and 630 nm. Since the minimum wavelength of the spectral transmittance of the anti-reflection film needs to substantially coincide with the minimum wavelength of the spectral reflectance, it is similarly desirable to be between 550 nm and 630 nm. Examples of the display device include a device for viewing an image through a display base such as a cathode ray tube or a liquid crystal display device.

[0036]

Embodiments of the present invention will be described below in detail. (Example 1)-Preparation of lower layer forming solution First, a solution A having the following composition was prepared as a lower layer forming solution. A: Ti (OC ₃ H ₇ ) ₄ titanium isopropoxide 2.5 wt% pigment dispersion 1 15 wt% nitric acid 0.05 wt% IPA (isopropyl alcohol) balance

Here, the pigment dispersion 1 has an average particle diameter of 2
This is a liquid in which 0 nm Hosta Palm Pink E is dispersed in isopropyl alcohol at a concentration of 2.5 wt%. The mixed solution prepared as in the above composition A was stirred for about 1 hour and reacted to obtain a lower layer forming solution. Preparation of Upper Layer Forming Solution Next, a solution B having the following composition was prepared as the upper layer forming solution. B: Si (OC ₂ H ₅ ) ₄ silicon tetraethoxide 5.0 wt% water 1.0 wt% nitric acid 0.05 wt% IPA (isopropyl alcohol) balance After adjusting to the above composition, the mixture was stirred for about 1 hour to react and react. A solution for formation was used.・ Formation of anti-reflective coating

First, the above-mentioned solution for forming the lower layer was prepared with a refractive index of 1.
52 is applied on a glass substrate by a dipping method,
After drying for 10 minutes, a lower layer film having a thickness of 0.1 μm was formed. Next, an upper layer forming solution is applied on the lower layer film,
Baking for 20 minutes in an atmosphere of 150 ° C.
m was formed. FIG. 2 shows the spectral reflectance and spectral transmittance of the thus obtained two-layer antireflection film. The spectral reflectance of the antireflection film was measured using an MCPD-1000 manufactured by Otsuka Electronics Co., Ltd., using a halogen lamp as a light source at an incident angle of 0 °, and measuring the substrate on which the antireflection film was not formed. Is expressed as a reflectance of 100%. The spectral transmittance was measured by a Minolta Camera spectrophotometer CM-
Performed using 1000. The sample was placed on a white plate and measured, and expressed as the square root of the ratio to the value of the substrate on which the antireflection film was not formed.

As can be seen from FIG. 2, the antireflection film of the present invention has a spectral reflectance shown by a curve 10a and a spectral transmittance shown by a curve 10b. It has a preventive effect. Example 2 Preparation of Underlayer Forming Solution First, a solution C having the following composition was prepared as the underlayer forming solution. C: Ti (OC ₃ H ₇ ) ₄ titanium isopropoxide 2.5 wt% pigment dispersion 2 15 wt% nitric acid 0.05 wt% IPA (isopropyl alcohol) balance

Here, the pigment dispersion 2 has an average particle diameter of 1
This is a solution in which 0 nm Heliogen Blue EP-7S is dispersed in isopropyl alcohol at a concentration of 2.5 wt%. The mixed solution adjusted as described above was stirred with water in the air for about 1 hour, and reacted to obtain a lower layer forming solution.・ Formation of anti-reflective coating

The solution for forming the upper layer was the same as the solution B in Example 1.
Was used to form an antireflection film on the substrate. The application method, conditions, and film thickness are the same as in Example 1. The characteristics of the antireflection film thus obtained are as shown in FIG. curve
It has a spectral reflectance shown by 20a and a spectral transmittance shown by a curve 20b, and it can be seen that it has an antireflection effect in a wider wavelength range as compared with the related art, as in the first embodiment. Example 3 Preparation of Underlayer Forming Solution First, a solution D having the following composition was prepared as the underlayer forming solution. D: Ti (OC ₃ H ₇ ) ₄ titanium isopropoxide 2.5 wt% Zr (OC ₄ H ₉ ) ₄ zirconium butoxide 0.5 wt% Pigment dispersion 3 15 wt% Nitric acid 0.01 wt% IPA (isopropyl alcohol) balance

Here, the pigment dispersion 3 has an average particle diameter of 3
This is a liquid in which a 0 nm perylene-based organic pigment is dispersed in isopropyl alcohol at a concentration of 2.5 wt%. Composition D above
The mixture prepared as described above was stirred for about 1 hour and reacted to obtain a lower layer forming solution. Preparation of Upper Layer Forming Solution Next, a solution E having the following composition was prepared as the upper layer forming solution. E: Si (OC ₂ H ₅ ) ₄ silicon tetraethoxide _4.5 wt% CF ₃ Si (OCH ₃ ) ₃ 0.5 wt% water 1.0 wt% nitric acid 0.05 wt% IPA (isopropyl alcohol) balance Adjusted to the above composition After that, the mixture was stirred and reacted for about 1 hour to obtain an upper layer forming solution.・ Formation of anti-reflective coating

Under the same coating method and conditions as in Example 1, an antireflection film of about 0.1 μm was formed on both the upper and lower layers on the substrate. The characteristics of the antireflection film thus obtained are as shown in FIG.

This antireflection film has a spectral reflectance shown by a curve 30a and a spectral transmittance shown by a curve 30b, and has a wider wavelength range than the conventional film 31a as in the above-described embodiment. It turns out that it has an effect. (Example 4)

In the above embodiment, the lower layer contains a dye, but by including a coupling agent together with the dye, an antireflection effect over a wider band can be obtained. Therefore, an example in which a dye and a coupling agent are contained will be described.

A solution mixed with the composition shown in Table 3 was allowed to stand at room temperature for 30 minutes, then applied on a substrate to form a lower layer film, and baked at 100 ° C. for 5 minutes. The pigment dispersions in Table 3 used were those used in Example 1.

[0047]

[Table 3]

Subsequently, a liquid having the following composition was prepared and applied from above the lower film to form an upper film, which was baked at 150 ° C. for 5 minutes. FIG. 7 shows the characteristics of the antireflection film thus formed. In the figure, 50a and 50f to 50h indicate the compositions a and g to h in Table 3, respectively. Silicon tetraethoxide 4.0 wt% Hydrochloric acid 1.5 wt% Water 1.0 wt% Isopropyl alcohol Remainder wt% (Example 5) Next, an example using a cathode ray tube as a specific example of the display device of the present invention will be described.

FIG. 8 is a partially cutaway side view showing a cathode ray tube 60 manufactured according to the present invention. This cathode ray tube 60
It has an airtight glass envelope 61 whose interior is evacuated. The envelope 61 has a neck 62 and a cone 63 continuing from the neck 62. Further, the envelope 61 has a cone 63 and a face plate 64 sealed with frit glass. A metal tension band 65 is wound around the outer periphery of the side wall of the face plate 64 for explosion protection.
An electron gun 66 for emitting an electron beam is arranged on the neck 62. The inner surface of the face plate 64 has an electron gun
A phosphor screen 67 made of a phosphor layer that emits light when excited by the electron beam from 66 is provided. Also,
Outside the cone 63, a deflecting device (not shown) for deflecting the electron beam so as to scan on the phosphor screen is inserted.

On the outer surface of the face plate 64 of the cathode ray tube 60, the lower layer forming solution and the upper layer forming solution of the first embodiment are applied to form the two-layer antireflection film 68 of the present invention. Is formed.

In the first embodiment, the coating is performed by the dipping method. In the present embodiment, the coating is performed by spin coating on the front surface of the face plate of the 25-inch color cathode ray tube after the assembly is completed. The conditions for drying and firing and the thicknesses of the lower and upper layers are the same as in Example 1.

The characteristics of this antireflection film are as shown in FIG. The cathode ray tube on which the antireflection film is formed is hardly affected by the reflection of ambient light such as windows and lights, and becomes a reflected light without coloring, and can form a good image without hindering color reproducibility. did it.

The spectral reflectance of the anti-reflection film formed on the surface of the color picture tube was measured using an MCPD-1000 manufactured by Otsuka Electronics Co., Ltd., and a halogen lamp was used as a light source. At an incident angle of 0 °, and then the same portion when the anti-reflection film was removed was measured, and the value when the anti-reflection film was removed was expressed as 100%. The spectral transmittance was measured using a Minolta Camera spectrophotometer CM-1000, the sample was measured, and then the antireflection film of the sample was removed with a chemical or the like, the same portion was measured, and the antireflection film was removed. The measured value of the sample was used as a standard and represented by the square root of the ratio of the measured value of the sample. (Example 6)

The antireflection film shown in Example 2 was formed on the outer surface of the screen of the cathode ray tube by spin coating.
The drying conditions, firing conditions, and film thickness are the same as in Example 3. The characteristics of the antireflection film were as shown in FIG. The cathode ray tube on which the antireflection film was formed exhibited good characteristics as in Example 5. (Embodiment 7) A case where the antireflection film shown in Embodiment 3 is formed on the outer surface of a liquid crystal display device will be described below.

FIG. 9 shows a liquid crystal display device according to the present invention.
This liquid crystal display device comprises a pair of substrates 71 and 72 made of glass opposed to each other, and electrodes 73 and 74 of a predetermined pattern made of ITO (Indium Tin Oxide) formed on each of the opposing surfaces of the substrates 71 and 72. The alignment films 75, 7 formed on the opposing surfaces of the pair of substrates 71, 72 so as to cover the electrodes 73, 74, respectively.
6 and a spacer 77 made of a thermosetting resin which is disposed between the substrates 71 and 72 and is fixed to the alignment films 75 and 76 to regulate the distance between the pair of substrates 71 and 72, and between the substrates 71 and 72. It is composed of a filled liquid crystal 78 and a sealing agent 79 for sealing the peripheral portions of the substrates 71 and 72 filled with the liquid crystal 78. An anti-reflection film 80 is provided on the outer surface of one of the substrates 71 constituting the display base.

This anti-reflection film 80 seals the portion other than the anti-reflection film 80 forming portion, and is coated with the thin film forming coating liquid of Example 3 so as to have a thickness of 0.1 μm.
Then, it is formed by firing. The characteristics of this antireflection film are as shown in Example 3, and the antireflection region is enlarged as compared with the conventional one.

Although the embodiments of the present invention have been described above, the antireflection characteristics are appropriately set in accordance with the characteristics required for the substrate on which the antireflection film is to be formed. It is not something to be done. Further, the combination of the antireflection film and the display device is not limited to the above example.

[0058]

As described above, according to the present invention, a dye is introduced into the lower layer film of the two-layer antireflection film, and the spectral transmittance and the spectral reflectance thereof are optimized to thereby achieve reflection over a wide band. The prevention effect can be achieved. In particular, it is possible to suppress an increase in reflection in a region deviated from a specific wavelength in which reflection, which has conventionally caused glare, is to be prevented. As a result, a display device with excellent display characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between a refractive index of a two-layer antireflection film and an antireflection effect.

FIG. 2 is a characteristic diagram showing spectral reflectance characteristics and light transmittance characteristics of an example of the antireflection film of the present invention.

FIG. 3 is a characteristic diagram showing a spectral reflectance characteristic and a light transmittance characteristic of another example of the antireflection film of the present invention.

4 is a reflectance characteristic diagram for explaining a shift in minimum reflectance when the upper and lower layers of the antireflection film shown in FIG. 2 are made thinner.

FIG. 5 is a reflectance characteristic diagram for explaining a shift in minimum reflectance when the upper and lower layers of the antireflection film shown in FIG. 2 are made thicker.

FIG. 6 is a characteristic diagram showing a spectral reflectance characteristic and a light transmittance characteristic of another example of the antireflection film of the present invention.

FIG. 7 is a characteristic diagram showing spectral reflectance characteristics and light transmittance characteristics of another example of the antireflection film of the present invention.

FIG. 8 is a partially cutaway view illustrating the structure of a cathode ray tube according to the present invention.

FIG. 9 is a cross-sectional view illustrating a structure of a liquid crystal display device according to the present invention.

[Explanation of symbols]

 10a, 20a, 30a ... Reflectance characteristics 10b, 20b, 30b ... Transmittance characteristics

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuzo Matsuda 1-9-2 Hara-cho, Fukaya-shi, Saitama Pref. JP-A-4-3344853 (JP, A)

Claims (8)

(57) [Claims] 1. An anti-reflection film comprising a first thin film formed on a substrate and a second thin film formed on the first thin film, wherein the first thin film has an average particle size of 3 Λt−50 nm <λr, where λt contains a dye having a wavelength of about 300 nm and the wavelength at which the spectral reflectance in the visible light region of the antireflection film is the minimum is λr, and the wavelength at which the spectral transmittance is the minimum is λt. <Λt + 70 nm. An anti-reflection film having a relationship of: 2. An antireflection film comprising a first thin film formed on a substrate and a second thin film formed on the first thin film on an outer surface of the light-transmitting display portion base. In the display device, the first thin film contains a dye having an average particle diameter of 3 to 300 nm, and a wavelength at which a spectral reflectance of the antireflection film in a visible light region is minimum is λr, and a spectral transmittance is a minimum. A display device characterized by having a relationship of λt−50 nm <λr <λt + 70 nm, where λt is the wavelength that becomes. 3. The antireflection method according to claim 1, wherein the wavelength λr at which the spectral reflectance is minimum and the wavelength λt at which the spectral transmittance is minimum have a relationship of λt−30 nm <λr <λt + 40 nm. film. 4. The wavelength λt at which the spectral transmittance is minimized is 5
The anti-reflection film according to claim 1, wherein the thickness is 50 to 630 nm. 5. The display device according to claim 2, wherein the wavelength λr at which the spectral reflectance is minimum and the wavelength λt at which the spectral transmittance is minimum have a relationship of λt−30 nm <λr <λt + 40 nm. . 6. The wavelength λt at which the spectral transmittance is minimized is 5
The display device according to claim 2, wherein the thickness is 50 to 630 nm. 7. The display device according to claim 5 , wherein the display device is a cathode ray tube. 8. The display device according to claim 5, wherein the display device is a liquid crystal display device.