JP2003131011A - Multilayer film and substrate with multilayer film using the multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film which has optical characteristics approximate to a multilayer film using a silica film as the outermost layer, and which can prevent small scratches from being formed on the surface of the film. SOLUTION: A multilayer film 16 has a high refractive-index film and a low refractive-index film laminated alternately on the surface of a substrate 11. The refractive-index of the outermost layer is 1.5 or less, and it is formed from a film which has a better scratch resistance than the silica film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film formed on various optical elements, and more particularly to a multilayer film suitable for a defocus substrate for a liquid crystal panel used in a projection type liquid crystal device such as a liquid crystal projector. is there.

[0002]

2. Description of the Related Art A liquid crystal panel used in a projection type liquid crystal device includes an active matrix substrate which is a liquid crystal driving substrate, an opposite substrate on which an ITO electrode and an alignment film are formed, and an active matrix substrate which is bonded to each other. And a liquid crystal held in the gap between the alignment substrates.

When this liquid crystal panel is used as a light valve of a liquid crystal projector, if floating dust or the like adheres to the surfaces of a pair of substrates (transparent substrates) that compose the liquid crystal panel, the projection light modulated by the liquid crystal panel will be generated. , The dust image (shadow) is enlarged and projected.

That is, an active matrix substrate is generally made of quartz glass and an opposite substrate is made of crystallized glass. These transparent substrates are used for the purpose of making the liquid crystal panel thinner and lighter. 1 mm or 0.
It has a thickness almost standardized to 7 mm. Therefore, the surface of the liquid crystal panel (transparent substrate) is separated from the liquid crystal, which is the focus position of the projected light, by only about 1 mm,
Dust adhering to the surface of the liquid crystal panel is, for example, 10 to 20μ.
Even if the size is as small as m, the image quality of the projected image on the screen will be impaired.

Further, since the liquid crystal projector enlarges and projects it on the screen, a strong light source light from a light source such as a metal halide lamp is incident on the liquid crystal panel in a condensed state. When such strong light source light is incident, the temperature of the liquid crystal sandwiched between the pair of transparent substrates also rises, the characteristics of the liquid crystal deteriorate, and the image quality tends to deteriorate. Although such a temperature rise of the liquid crystal is somewhat mitigated by disposing a heat ray cut filter between the light source and the liquid crystal panel to reduce the incidence of unnecessary infrared rays, or by providing a cooling mechanism in the liquid crystal panel, In order to achieve high image quality, more efficient temperature rise prevention measures are necessary.

In order to solve such a problem, in recent years, a transparent glass plate called a defocus substrate is provided on the outer surface of one or both of the transparent substrates to prevent dust from directly adhering to the transparent substrates. I have to. Further, by bonding the transparent substrate and the defocus substrate with a resin or the like so that the total thickness of both is about 2 mm or more, or by disposing the defocus substrate on the transparent substrate with a space of about 2 mm, Even if dust adheres to the outer surface of the defocus substrate, the distance between the dust and the liquid crystal, which is the focus position of the projected light, is equal to the thickness of the defocus substrate.
Alternatively, it becomes longer by adding voids to it. As a result, the dust image is in a defocused state and is greatly blurred on the screen, so that it is visually inconspicuous.

Further, when the defocus substrate is provided on the outer surface of the transparent substrate, the heat accumulated in the liquid crystal is conducted to the defocus substrate and is efficiently dissipated. Therefore, by combining this with a cooling mechanism, it becomes possible to suppress the temperature rise of the liquid crystal panel extremely efficiently.

[0008]

Generally, light incident on an optical element made of a transparent substrate such as glass or plastic is
Since 3% or more is reflected and this phenomenon occurs on the front and back of the transparent substrate, 6% or more is reflected on the front and back. Since this reflection causes a loss of transmittance, an antireflection film is formed on the surface of an optical element such as a defocus substrate of a liquid crystal panel that requires high transmittance. When the antireflection film is formed on the surface of the defocus substrate, it becomes difficult for unnecessary light due to surface reflection to enter the liquid crystal panel, and it is possible to prevent light leakage or the like of the switching element.

In the case of a defocus substrate for a liquid crystal panel, the reflectance at a wavelength of 450 to 650 nm is 0.5%.
The following is required, and conventionally, as an antireflection film satisfying such requirements, a multilayer film in which a high refractive index film and a low refractive index film are alternately laminated is used.

The outermost layer of this type of multilayer film is often a low refractive index film from the viewpoint of film strength and film design, and a silica (SiO ₂ ) film is particularly excellent in film formability and durability. Most commonly used because However, the antireflection film on the defocus substrate has a width of 20 μm or more and a length of 10 mm.
When the above-mentioned minute scratches occur, a shadow may be formed on the projection screen due to this, and even if the outermost layer of the antireflection film is a silica film, minute scratches exceeding the allowable range may be formed.

Such minute scratches on the silica film are formed when the surface of the defocus substrate comes into contact with other members. Especially when the defocus substrate is placed on the holding table, its reflection is prevented. When the surface of the membrane is brought into contact with the holding base, the outermost silica membrane is often brought into contact with the holding base to form scratches.

The present invention has been made in view of the above circumstances and has optical characteristics similar to those of a multilayer film using a silica film as the outermost layer, and prevents the formation of minute scratches on the film surface. It is an object of the present invention to provide a multilayer film capable of

[0013]

A multilayer film of the present invention is a multilayer film in which a high refractive index film and a low refractive index film are alternately laminated on the surface of a substrate, and the outermost layer has a refractive index of It is 1.5 or less, and is characterized by being formed from a film having excellent scratch resistance as compared with a silica film.

In the substrate with a multilayer film of the present invention, the first layer has a high refractive index film having a refractive index of 1.8 to 2.4, and the second layer has a refractive index of 1.38 to 1. 7, a low refractive index film, a third layer having a high refractive index of 1.8 to 2.4, and an outermost layer having a silicon oxynitride film having a refractive index of 1.5 or less. And

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The multilayer film of the present invention is formed by alternately laminating a high refractive index film and a low refractive index film, and the outermost layer has a refractive index of 1.5 or less and silica. Since it consists of a film that is more scratch-resistant than a film, optical properties similar to those of a multilayer film using a silica film as the outermost layer can be obtained, and scratches are less likely to occur even when it comes into contact with other members. .

Particularly, the silicon oxynitride film is a transparent film and is more flexible than the silica film, so that it is not peeled off easily even when it comes into contact with other members, and scratches are less likely to occur, which is preferable. The silicon oxynitride film can be represented by a chemical formula of SiOxNy, where x is 1.9 or less and y is 0.9 or less. The ratio of (nitrogen / oxygen) in the silicon oxynitride film is 0.01 to 1
The (atomic ratio) is more preferable because the film has a very high flexibility. In addition, when the ratio of oxygen and nitrogen is the above-mentioned ratio, the refractive index of the film can be suppressed to a low level, which is the most suitable as a substitute film for the silica film. Ie (nitrogen / oxygen)
If the ratio is larger than 1, the film strength increases, but the refractive index increases, and the difference from the refractive index of the silica film tends to increase. If the ratio of (nitrogen / oxygen) is less than 0.01, the flexibility of the film tends to decrease.

The multilayer film-coated substrate of the present invention comprises:
A high refractive index film having a refractive index of 1.9 to 2.4 as the first layer, a low refractive index film having a refractive index of 1.4 to 1.5 as the second layer, and a third layer
The layer is composed of a high-refractive index film having a refractive index of 1.9 to 2.4, and the outermost layer is composed of a silicon oxynitride film having a refractive index of 1.4 to 1.5. Have
It is preferable to form each of these layers by a sputtering method because the workability is good and the index can be increased as compared with the case of forming a film by a vacuum evaporation method.

As the high refractive index layer of the first layer, oxidation is
Titanium: TiO₂(Refractive index 2.35), niobium oxide: N
b₂O_Five(2.25), tantalum oxide: Ta₂O_Five(Refractive index
2.10), silicon nitride: SiN (refractive index 2.0
0), zirconium oxide: ZrO ₂(Refractive index 2.1
0), hafnium oxide: HfO₂(Refractive index 2.20),
Cerium oxide: CeO₂(Refractive index 2.20), suboxide
Lead: ZnO (refractive index 2.00) and mixtures of these
Although a transparent layer can be used, this layer is formed by sputtering.
If so, the optical characteristics of the film and the ease of manufacturing the target
Considering the uniformity of the film, titanium oxide, nitric oxide
Suitable is silicon nitride. This first layer is 5-5
With a geometrical thickness of 0 nm, preferably 10-30 nm
It is desirable to do.

As the second low refractive index layer, silica: S
iO ₂ (refractive index 1.46), magnesium fluoride: Mg
F ₂ (refractive index 1.38), aluminum oxide: Al ₂ O ₃
(Refractive index 1.63) or a transparent layer made of a mixture of these can be used. However, when this layer is formed by the sputtering method, the optical characteristics of the film, the ease of manufacturing a target, and the uniformity of the film. Considering the property, silica is most suitable. This second
The layers desirably have a geometrical thickness of 10 to 50 nm, preferably 15 to 40 nm.

When forming a film of silica by a sputtering method,
When reactive sputtering is performed using a Si target, the film formation rate is large and effective, but SiO ₂ that is an insulating film is formed on the target surface, and abnormal discharge may occur. It is preferable to adopt the sputtering method.

As the high refractive index layer of the third layer, a transparent layer made of titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, hafnium oxide, cerium oxide, silicon nitride, or a mixture thereof can be used. In the case of forming a film by the method described above, titanium oxide, niobium oxide, and silicon nitride are suitable in view of the optical characteristics of the film, the ease of manufacturing the target, and the uniformity of the film. This third layer is 50-
It is desirable to have a geometric thickness of 130 nm, preferably 60-125 nm. In particular, niobium oxide is optimal because it has a film formation rate about three times that of titanium oxide and it is easy to increase the film thickness.

Fourth layer silicon oxynitride film (SiOxNy)
Is a transparent film having a low refractive index, and as described above, since this film is more flexible than a silica film, it does not easily peel off even if it comes into contact with other members, and scratches do not easily occur. In particular, it is preferable that the ratio of (nitrogen / oxygen) in the silicon oxynitride film be 0.01 to 1 (atomic ratio) because the film becomes extremely flexible. In addition, when the ratio of oxygen and nitrogen is the above-mentioned ratio, the refractive index of the film can be suppressed to a low level, which is the most suitable as a substitute film for the silica film. That is, if the ratio of (nitrogen / oxygen) is greater than 1, the film strength increases, but the refractive index increases, which makes it unsuitable as a substitute film for a silica film. If the ratio of (nitrogen / oxygen) is less than 0.01, the flexibility of the film tends to decrease. This fourth layer is 60 to 140n
It is desirable to have a geometric thickness of m, preferably 60-100 nm.

In the present invention, each layer of the multilayer film is
When a film is formed by a magnetron sputtering method under the condition that the O ₂ concentration or N ₂ concentration in Ar is 50% or less, a film having a large film formation rate is formed, and it becomes possible to mass-produce more inexpensively. preferable.

Further, this multilayer film has a wavelength of 450-65.
Since the visible light reflectance at 0 nm is 0.5% or less, it is suitable as a defocus substrate for a liquid crystal panel when it is coated on the surface of a heat resistant glass plate.

That is, when a defocus substrate is manufactured by depositing the above-mentioned multilayer film on a heat-resistant glass plate, and the defocus substrate is adhered to the liquid crystal panel or arranged with a gap, unnecessary light due to surface reflection is reflected on the liquid crystal panel. It becomes difficult for the light to enter, and it is possible to prevent light leakage or the like from occurring in the switching element.

Further, even if dust adheres to the outer surface of the defocus substrate, the distance between the dust and the liquid crystal, which is the focus position of the projected light, is equal to the thickness of the defocus substrate, or a void is added to this. It becomes longer by the amount. As a result, the dust image is in a defocused state and is greatly blurred on the screen, so that it is visually inconspicuous. Moreover, by providing the defocus substrate, the heat accumulated in the liquid crystal can be conducted to the defocus substrate and can be efficiently dissipated.

Examples of the material of the heat resistant glass used for the defocus substrate include crystallized glass, quartz glass and borosilicate glass. The coefficient of thermal expansion in the temperature range of 30 to 750 ° C. is -10. ~ + 15 × 10 ^-7 / ° C
The transparent crystallized glass is suitable for its excellent heat resistance, high thermal conductivity, and large heat dissipation effect.

More specifically, in terms of mass percentage, Li ₂ O
1 to 7%, Al ₂ O ₃ 15 to 35%, SiO ₂ 55
~ 70%, TiO ₂ 1-5%, ZrO ₂ 0-5%, P
₂ O ₅ 0-5%, Na ₂ O + K ₂ O 0.1-5% composition, β-quartz solid solution crystals are deposited, -10 to +15 x
A transparent crystallized glass having a thermal expansion coefficient of 10 ⁻⁷ / ° C., a visible light transmittance at a thickness of 3 mm of 80% or more, and a thermal conductivity of 1.5 W / m ° C. or more is suitable.

[0029]

EXAMPLES The present invention will be described in detail below based on examples.

Table 1 shows the structures of the multilayer films (materials and geometrical thickness of each layer) of Examples and Comparative Examples, wavelengths of 450 nm and 5
It shows the reflectance at 50 nm and 650 nm.

[0031]

[Table 1]

The multilayer films in the table were formed as follows.

First, as a substrate, 140 × 140 × 1.1
A Li ₂ O—Al ₂ O ₃ —SiO ₂ system low expansion transparent crystallized glass substrate (Neoceram N-0 manufactured by Nippon Electric Glass Co., Ltd.) having a size of mm is prepared, and a magnetron sputtering film forming apparatus is used on one surface thereof. Thus, a four-layer antireflection film having the structure shown in the table was formed. The film formation of each layer was performed under the condition that the O ₂ concentration in Ar was about 20%.

The spectral reflectance characteristics of each of the substrates thus obtained were measured, and the reflectances at wavelengths of 450 nm, 550 nm, and 650 nm are shown in Table 1, and the reflectance curves of the samples of Example 1 and Comparative Example at wavelengths of 350 to 800 nm. Figure 1
It was shown to. As for the spectral reflection characteristic, 15 ° specular reflection was measured using an instantaneous multi-reflectance measuring instrument.

As is clear from Table 1, each of the substrates of the examples has a low reflectance of 0.5% or less at a wavelength of 450 to 650 nm and is required as a defocus substrate of a liquid crystal panel, like the substrates of the comparative examples. The low reflectance is satisfied. Further, as is clear from FIG. 1, Example 1 had a reflectance characteristic similar to that of the comparative example.

Table 2 shows the results of subjecting each of the samples of Examples and Comparative Examples to a pencil test.

[0037]

[Table 2]

In this pencil test, the scratch resistance of each sample was evaluated by the HEIDON surface property test. The pencil angle was 45 °, the scratching speed was 100 mm / min, and the load was 200.
g, Mitsubishi Pencil HI-uni (6H-9H).

For the evaluation, the multilayer film on one surface of each sample was tested three times with a pencil of 6H to 9H, and the presence or absence of scratches was visually confirmed. The case is indicated by ○, and the case where any scratch can be confirmed is indicated by ×.

Next, the substrate of Example 1 was set to 14 mm × 10 m.
A defocused substrate for a liquid crystal panel was produced by cutting out into a size of m × 1.1 mm and then chamfering. Further, as shown in FIG. 2, an active matrix substrate (thickness 0.7 mm) 10 made of quartz glass and a counter substrate (thickness 0.7 m) made of low expansion transparent crystallized glass are used.
m) 11 are pasted together with a sealant 12 at a predetermined interval, and after preparing a liquid crystal panel 14 in which liquid crystal 13 is sealed in the gaps between the substrates 10 and 11, the above defocus is applied to the outer surface of the counter substrate 11. The substrate 15 was attached with a resin adhesive (not shown). In the figure, 16 is an antireflection film formed on the outer surface of the defocus substrate 15, 17 is an opposing electrode made of an ITO film formed on the inner surface of the defocus substrate 15, 18 is an alignment film, and 19 is an active film. The antireflection film formed on the outer surface of the matrix substrate 10 is shown.

When this liquid crystal panel 14 is used as a light valve of a liquid crystal projector, even if a minute dust adheres to the surface of the defocus substrate 15, the dust image (shadow) is enlarged and projected on the screen. In addition, the heat accumulated in the liquid crystal 13 was efficiently conducted to the defocus substrate 15, and the temperature rise was suppressed.

In the present embodiment, an example in which the multilayer film is used as the antireflection film of the defocus substrate of the liquid crystal panel has been shown, but the multilayer film of the present invention is not limited to this, and the increased reflection is achieved. It can be applied to various applications such as a film, an interference filter, a half mirror, a dichroic mirror, a cold mirror, a laser mirror, a polarization filter, and the like.

[0043]

INDUSTRIAL APPLICABILITY As described above, the multilayer film of the present invention has optical characteristics similar to those of a multilayer film using a silica film as the outermost layer, and even if it comes into contact with other members, minute scratches are formed on the film surface. Since it is difficult to generate, it can be applied to various optical elements, and is particularly suitable for a defocus substrate for a liquid crystal panel in which the allowable level of minute scratches on the antireflection film is severe.

[Brief description of drawings]

FIG. 1 is a graph showing reflectance curves of multilayer films of Example 1 and Comparative Example.

FIG. 2 is a schematic cross-sectional view showing a liquid crystal panel to which a defocus substrate is attached.

[Explanation of symbols]

10 Active matrix substrate 11 Counter substrate 12 Seal material 13 LCD 14 LCD panel 15 Defocus substrate 16, 19 Antireflection film 17 Counter electrode 18 Alignment film

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H091 FA37X FB06 FD06 KA01                       LA02                 2K009 AA07 AA15 BB02 CC01 CC03                       DD04                 4F100 AA12C AA12K AA31A AD05C                       AD05K AG00A AR00B AR00C                       AR00D AT00A BA03 BA04                       BA07 BA08 BA10A BA10C                       BA26 GB41 JA11A JK12                       JN06 JN18B JN18C JN18D                       YY00 YY00C

Claims (6)

[Claims] 1. A multilayer film in which a high refractive index film and a low refractive index film are alternately laminated on the surface of a substrate, wherein the outermost layer has a refractive index of 1.5 or less, which is higher than that of a silica film. A multi-layer film formed by a film having excellent scratch resistance. 2. The multilayer film according to claim 1, wherein the outermost layer is formed of a silicon oxynitride film. 3. The silicon oxynitride film has a nitrogen / oxygen ratio of 0.01 to 1 in atomic ratio.
The multilayer film described. 4. From the substrate side, the first layer has a refractive index of 1.
8 to 2.4 high refractive index film, the second layer has a refractive index of 1.3
Low refractive index film of 8 to 1.7, refractive index of 1.8 as the third layer
A substrate with a multilayer film, comprising a high-refractive index film of about 2.4 and a silicon oxynitride film having a refractive index of 1.5 or less as an outermost layer. 5. The visible light reflectance at a wavelength of 450 to 650 nm is 0.5% or less.
A substrate with a multilayer film as described above. 6. The substrate with a multilayer film according to claim 4, wherein the substrate is made of any one of crystallized glass, quartz glass and borosilicate glass.