JP2003043208A - Base material with reflection preventing film and defocusing substrate for liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base material with a reflection preventing film satisfying reflection preventing characteristics required for a defocusing substrate for a liquid crystal panel with only a small number of layers and deposited with a sputtering method and the defocusing substrate for the liquid crystal panel using the same. SOLUTION: The defocusing substrate 15 comprises the base material with the reflection prevention film containing four layers formed on the base material. The four layers are named as a first layer, a second layer, a third layer and a fourth layer successively from the base material side and, the first layer is a transparent layer with 1.8-2.4 refractive index and has 5-50 nm geometric thickness, the second layer is a transparent layer with 1.38-1.7 refractive index and has 10-70 nm geometric thickness, the third layer is a transparent layer with 1.8-2.4 refractive index and has 50-150 nm geometric thickness and the fourth layer is a transparent layer with 1.38-1.7 refractive index and has 60-140 nm geometric thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate with an antireflection film suitable as a defocus substrate for a liquid crystal panel used in a projection type liquid crystal device such as a liquid crystal projector.

[0002]

2. Description of the Related Art A liquid crystal panel used in a projection type liquid crystal device includes an active matrix substrate on which image electrodes and switching elements are formed, and an opposite substrate on which a counter electrode and a light shielding film are formed. It has a structure including a liquid crystal held in a gap between transparent substrates.

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

That is, the active matrix substrate of a liquid crystal panel is generally made of quartz glass and the counter substrate is made of crystallized glass. These transparent substrates are used for the purpose of reducing the thickness and weight of the liquid crystal panel. , 1.1
It has a thickness almost standardized to mm or 0.7 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, and the dust attached to the surface of the liquid crystal panel is, for example, 1 mm.
Even a minute size of about 0 to 20 μm will impair the quality of the projected image on the screen.

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. In addition, 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 arranging the defocus substrate on the transparent substrate with a space of about 2 mm, Even if dust adheres to the outer surface of the focus substrate, the distance between the dust and the liquid crystal, which is the condensing position of the projected light, becomes longer by the thickness of the defocus substrate or by adding a void 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, the light incident on an optical element formed of a transparent substrate such as glass or plastic is 3 times.
% Or more, and since 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 outer 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 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 of the switching element and the like from occurring.

Therefore, the defocus substrate for a liquid crystal panel has a reflectance of 0.5% at a wavelength of 450 to 650 nm.
The following requirements are required, and conventionally, there has been a multilayer film having seven or more layers as an antireflection film satisfying such requirements. However, in the antireflection film, as the number of layers increases, it is difficult to control the film thickness of each layer and the uniformity of the film, so that the reflectance is unstable and the raw material cost increases.
It is desirable to reduce the number of layers.

In the conventional antireflection film, the outermost layer is Mg
Since it is made of F _2, it is formed by the vacuum evaporation method. That is, in general, a multilayer film can be formed by a sputtering method, but it is extremely difficult to react Mg and F ₂ by a sputtering method. Therefore, when forming a multilayer film including a MgF ₂ layer, The vacuum deposition method is adopted.

However, the vacuum evaporation method has a small film formation rate, and in order to obtain a uniform film by the vacuum evaporation method, after setting the plate glass in the holder, the film is formed while rotating the surface in the vacuum evaporation apparatus. Since it is necessary to form a thin film, the film formation time becomes very short, and it is difficult to obtain a uniform film. In particular, when the film formation is completed during one rotation of the plate glass, it is extremely difficult to obtain a uniform film.

Moreover, the vacuum vapor deposition method is mainly carried out in a batch type apparatus, and when a dense film is to be formed, the ultimate vacuum before film formation must be reduced, and a very long vacuuming can be performed. Since it is necessary, there is a problem that workability is poor.

An object of the present invention is to provide an antireflection substrate having a small number of layers, which satisfies the antireflection characteristics required for a defocus substrate for a liquid crystal panel and can be formed by a sputtering method. It is to provide a defocus substrate for a used liquid crystal panel.

[0014]

In the substrate with an antireflection film of the present invention, an antireflection film including four layers is formed on the substrate, and the first, second, third and fourth layers are arranged in order from the substrate side. , The first layer is a transparent layer having a refractive index of 1.8 to 2.4 and has a geometric thickness of 5 to 50 nm, and the second layer has a refractive index of 1.38 to 1.7 transparent layer, 10
The third layer is a transparent layer having a refractive index of 1.8 to 2.4 and a geometrical thickness of 50 to 150 nm.
And a fourth layer having a refractive index of 1.38.
~ 1.7 transparent layer, having a geometrical thickness of 60-140 nm.

A defocus substrate for a liquid crystal panel of the present invention is characterized by comprising the above-mentioned substrate with an antireflection film.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The substrate with an antireflection film of the present invention will be described in detail below.

In the antireflection film of the present invention, the first layer formed closest to the substrate is a transparent layer having a refractive index of 1.8 to 2.4 and has a thickness of 5 to 50 nm (preferably 5 to 30 n).
m, more preferably 10 to 30 nm). The material of the first layer is titanium oxide: TiO ₂ (refractive index 2.35), niobium oxide: N.
b ₂ O ₅ (refractive index 2.25), zirconium oxide: ZrO
₂ (refractive index 2.10), tantalum oxide: Ta ₂ O ₅ (refractive index 2.10), hafnium oxide: HfO ₂ (refractive index 2.
20), cerium oxide: CeO ₂ (refractive index 2.20),
Silicon nitride: Si ₃ N ₄ (refractive index 2.00) or a mixture thereof can be used, but when the film is formed by the sputtering method, the optical characteristics of the film, the ease of producing a target, and the uniformity of the film. Considering the above, titanium oxide, niobium oxide, and silicon nitride are suitable.

The second layer is a transparent layer having a refractive index of 1.38 to 1.7 and is 10 to 70 nm (preferably 10 to 5 nm).
It has a geometric thickness of 0 nm, more preferably 15-40 nm. As the material of this second layer,
Silicon oxide: SiO ₂ (refractive index 1.46), magnesium fluoride: MgF ₂ (refractive index 1.38), aluminum oxide: Al ₂ O ₃ (refractive index 1.63), or a mixture thereof can be used. However, when this layer is formed by the sputtering method, the material is limited to silicon oxide and aluminum oxide, and silicon oxide is particularly preferable in consideration of the optical characteristics of the film, the ease of manufacturing the target, and the uniformity of the film. Most suitable.

When forming a film of silicon oxide by a sputtering method, it is effective to carry out reactive sputtering using a Si target because the film forming rate is large.
Since SiO ₂ which is an insulating film is formed on the surface of the target and abnormal discharge may occur, it is preferable to adopt the sputtering method using an AC power source.

The third layer is a transparent layer having a refractive index of 1.8 to 2.4 and a thickness of 50 to 150 nm (preferably 60 to 1).
30 nm, more preferably 70-125 nm). As a material of the third layer, titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, hafnium oxide, cerium oxide, silicon nitride, or a mixture thereof can be used. Considering the optical characteristics of, the ease of manufacturing the target, and the uniformity of the film, titanium oxide, niobium oxide, and silicon nitride are suitable. Especially the third layer
Although the film thickness is as large as 50 to 150 nm, niobium oxide is optimal because the film formation rate is fast (about 3 times that of titanium oxide).

The fourth layer is a transparent layer having a refractive index of 1.38 to 1.7 and a thickness of 60 to 140 nm (preferably 65 to 65 nm).
It has a geometric thickness of 120 nm). As the material of the fourth layer, silicon oxide, magnesium fluoride, aluminum oxide, or a mixture thereof can be used. However, when forming this layer by a sputtering method, the material is limited to silicon oxide or aluminum oxide, and in particular, the optical characteristics of the film, the ease of manufacturing the target,
Considering the film uniformity, silicon oxide is most suitable.

When forming a film of silicon oxide by the sputtering method, it is effective to carry out reactive sputtering using a Si target because the film forming rate is large.
Since SiO ₂ which is an insulating film is formed on the surface of the target and abnormal discharge may occur, it is preferable to adopt the sputtering method using an AC power source.

Although the antireflection film of the present invention has a four-layer structure, it strictly regulates the refractive index and geometrical thickness of each layer, so that it is 0.5% or less over a wide wavelength range of 450 to 650 nm. The visible light reflectance of is obtained. for that reason,
When this antireflection film is formed on the surface of the heat-resistant glass plate, it becomes suitable as a defocus substrate for a liquid crystal panel.

That is, when a defocus substrate is produced by depositing the above antireflection film on a heat-resistant glass plate, and the defocus substrate is adhered to a 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.

Even if dust adheres to the outer surface of the defocus substrate, the distance between the dust and the liquid crystal, which is the position where the projection light is focused, is equal to or less than the thickness of the defocus substrate. It becomes longer by adding. 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.

Further, since the antireflection film of the present invention is basically composed of four layers, it is easier to control the film thickness and uniformity of each layer than the conventional antireflection film having seven or more layers, and the raw material cost is also increased. It is cheap.

In the antireflection film of the present invention, all layers can be formed by the sputtering method. Particularly, when thin films such as the first layer and the second layer are formed by the sputtering method, a uniform film can be obtained. It is preferable because it is easy. Further, since the sputtering method has better workability than the vacuum evaporation method, it is possible to raise the index, and the film obtained by this has a dense structure, is less likely to be scratched, and is likely to have a reduced reflectance. .
Further, since the film surface is smooth, there is also an advantage that dirt is unlikely to adhere.

Further, in the present invention, when each layer of the antireflection film is formed by the magnetron sputtering method under the condition that the O ₂ concentration or N ₂ concentration in Ar is 50% or less, the film having a large film formation rate is obtained. Is preferable, and mass production is possible at a lower cost, which is preferable.

Crystallized glass, quartz glass, and borosilicate glass are suitable as the material of the heat-resistant glass used for the defocus substrate, and the coefficient of thermal expansion in the temperature range of 30 to 750 ° C. is -10 to 10 in particular. A transparent crystallized glass of + 15 × 10 ⁻⁷ / ° C. is suitable because it has excellent heat resistance, high thermal conductivity, and a 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.

[0031]

EXAMPLES The substrate with an antireflection film of the present invention will be described in detail below with reference to examples.

Tables 1 to 3 show the structures (materials and geometrical thickness of each layer) of the antireflection films of Examples and Comparative Examples and the wavelength of 450 n.
It shows the reflectance at m, 550 nm and 650 nm.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

The substrates with antireflection films of Examples 1 to 7 in the table were produced as follows.

First, as a substrate, 140 mm × 140 mm
Li ₂ O-Al ₂ O ₃ -SiO ₂ -based low expansion transparent crystallized glass substrate having a size of × 1.1 mm (coefficient of thermal expansion: −4 × 10
^-7 / ° C., visible light transmittance at 3 mm thickness: 80% or more, thermal conductivity: 1.7 W / m ° C.) was prepared, and a magnetron type sputtering film-forming apparatus was used on one surface of A four-layer antireflection film having the structure was formed. The film formation of each layer was performed under the condition that the O ₂ degree in Ar was about 20%.

On the other hand, the antireflection film of the comparative example shows an antireflection film which has been conventionally used for a defocus substrate. After preparing a substrate similar to that of the embodiment, a vacuum vapor deposition apparatus is provided on one surface thereof. It was produced by forming a 7-layer antireflection film having the constitution shown in the table.

The spectral reflection characteristics of each of the substrates thus obtained were measured, and the reflectance at wavelengths of 450 nm, 550 nm and 650 nm is shown in the table, and for Examples 1 and 2 and Comparative Example, reflection at wavelengths of 350 to 800 nm was performed. The rate curve is shown in FIG. As for the spectral reflection characteristic, 15 ° specular reflection was measured using an instantaneous multi-reflectance measuring instrument.

As is clear from Tables 1 to 3 and FIG. 1, each of the substrates of the examples has wavelengths of 450 to 65 like the substrate of the comparative example.
The reflectance at 0 nm is as low as 0.5% or less, which satisfies the low reflectance required for the defocus substrate of the liquid crystal panel.

Next, the substrate of Example 2 was set to 14 mm × 10 mm.
A defocus substrate for a liquid crystal panel was produced by cutting out to a size of × 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 mm) 1 made of low expansion transparent crystallized glass 1
After the liquid crystal panel 14 in which 1 is bonded at a predetermined interval by the sealing material 12 and the liquid crystal 13 is sealed in the space between the substrates 10 and 11 is prepared, the defocus substrate 15 is attached to the outer surface of the counter substrate 11. Was attached with a resin adhesive (not 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 this embodiment, the example in which the substrate with antireflection film is used as the defocus substrate of the liquid crystal panel is shown, but the application of the substrate with antireflection film of the present invention is not limited to this. Instead, it can be applied to various optical elements on which an antireflection film is formed, such as a window glass for a laser diode and a front plate of a reflecting mirror of a light source lamp.

[0044]

As described above, the substrate with an antireflection film of the present invention can suppress reflection in the visible region with a small number of film layers. Therefore, when this substrate is used as a defocus substrate for a liquid crystal panel, it is possible to prevent light leakage of a switching element, and to prevent floating dust from adhering to the transparent substrate of the liquid crystal panel. Even if dust adheres to the surface, it is in a defocused state and is greatly blurred on the screen, so that it is visually inconspicuous, and the heat accumulated in the liquid crystal is conducted to the defocusing substrate and is efficiently dissipated.

[Brief description of drawings]

FIG. 1 is a graph showing reflectance curves of antireflection films of Examples 1 and 2 and a comparative example.

FIG. 2 is an explanatory diagram 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

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H091 FA37X FA37Z FB06 FB07                       FC01 FD06 FD13 FD14 KA01                       KA10 LA12 LA16 LA30 MA07                 2K009 AA07 AA09 BB02 CC03 CC06                       DD04                 4F100 AG00E AR00A AR00B AR00C                       AR00D AT00E BA05 BA07                       BA10D BA10E BA26 EH66A                       EH66B EH66C EH66D JN01A                       JN01B JN01C JN01D JN06                       JN18A JN18B JN18C JN18D                       YY00A YY00B YY00C YY00D

Claims (5)

[Claims] 1. An antireflection film including four layers is formed on a substrate, and when referred to as a first layer, a second layer, a third layer, and a fourth layer from the substrate side, the first layer has a refractive index of A transparent layer of 1.8 to 2.4, having a geometric thickness of 5 to 50 nm, and a second layer
Is a transparent layer having a refractive index of 1.38 to 1.7,
The third layer is a transparent layer having a geometrical thickness of 10 to 70 nm and a refractive index of 1.8 to 2.4, and a thickness of 50 to 150 nm.
The fourth layer has a geometrical thickness of 1. nm and a refractive index of 1.
A substrate with an antireflection film, which is a transparent layer of 38 to 1.7 and has a geometric thickness of 60 to 140 nm. 2. The substrate with an antireflection film according to claim 1, wherein each layer is formed by a sputtering method. 3. The substrate with an antireflection film according to claim 1, wherein the reflectance of the antireflection film at a wavelength of 450 to 650 nm is 0.5% or less. 4. The substrate with an antireflection film according to claim 1, wherein the substrate is made of any one of crystallized glass, quartz glass and borosilicate glass. 5. A defocus substrate for a liquid crystal panel, which comprises the substrate with an antireflection film according to claim 1.