JP2003131206A - Liquid crystal panel and counter substrate for liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal panel using a counter substrate provided with a reflection preventing film with desired reflection preventing properties and preventing micro scratches beyond the permissible range from being formed on the film surface. SOLUTION: The liquid crystal panel 10 is provided with an active matrix substrate 11, the counter substrate 12 placed opposite to the active matrix substrate 11 and a liquid crystal 14 held in a gap between the respective substrates 11, 12. The counter substrate 12 is constructed by forming an ITO (indium tin oxide) film 18 on the inside surface thereof, and forming a reflection preventing film 17 having a high refractive index film and a low refractive index film alternately laminated on the outside surface thereof and having a silicon oxynitride film as the outermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to 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 is formed by bonding an active matrix substrate, which is a liquid crystal driving substrate, and a counter substrate, on which a counter electrode and an alignment film mainly made of ITO film are formed. It has a structure including an active matrix substrate and a liquid crystal held in a gap between the counter substrate.

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.

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 each transparent substrate to prevent dust from directly adhering to the transparent substrate. There is. 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 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 defocus substrate, the distance between the dust and the liquid crystal, which is the position where the projected light is focused, is equal to the thickness of the defocus substrate or the amount of space added to it. become longer. As a result, the dust image is in a defocused state and is greatly blurred on the screen, so that it is visually inconspicuous.

By the way, generally, light incident on an optical element made of a transparent substrate such as glass or plastic reflects 3% or more, and since this phenomenon occurs on the front and back of the transparent substrate, it reflects 6% or more on the front and back. Become. 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%.
In order to satisfy such requirements, it is necessary to form an antireflection film in which a high refractive index film and a low refractive index film are alternately laminated on one surface of the defocus substrate. ing.

[0008]

The conventional liquid crystal panel is
Since the defocus substrate is adhered to the counter substrate or the defocus substrate is bonded to the counter substrate at a constant interval, the entire structure becomes complicated and the manufacturing cost increases. Therefore, in recent years, it has been considered to increase the thickness of the counter substrate to impart a defocus function to itself.

By the way, an ITO (Ind) is usually formed on the inner surface of the active matrix substrate or the counter substrate of the liquid crystal panel.
When a counter electrode having a large thickness such as that described above is formed by forming a transparent electrode made of an aluminum tin oxide film, an ITO film is formed on the inner surface side and an antireflection film is formed on the outer surface side. Will be. Moreover, after forming the ITO film and the antireflection film on the counter substrate, an alignment film is formed on the ITO film. At the time of this film formation, the antireflection film is placed on the lower side to hold the counter substrate. Since it is placed on the table, the antireflection film may rub against the holding table, and minute scratches may be formed on the surface.

That is, as the outermost layer of this type of antireflection film, a low refractive index film is used from the viewpoints of film strength and film design, and since a silica film is particularly excellent in film formability and durability. Most often used, when a minute scratch with a width of 20 μm or more and a length of 10 mm or more occurs on the antireflection film formed on the counter substrate, this may cause a shadow on the projection screen. Even if the outermost layer of the film is a silica film, minute scratches exceeding the allowable range may be formed.

The present invention has been made in view of the above circumstances and has an antireflection film having a desired antireflection property and capable of preventing the formation of minute scratches exceeding the allowable range on the film surface. An object of the present invention is to provide a liquid crystal panel using a counter substrate provided with.

[0012]

The liquid crystal panel of the present invention comprises:
A liquid crystal panel comprising an active matrix substrate, a counter substrate arranged to face the active matrix substrate, and a liquid crystal held in a gap between the substrates, wherein an ITO film is formed on an inner surface side of the counter substrate. The high refractive index film and the low refractive index film are alternately laminated on the outer surface side, and the antireflection film having the outermost layer made of a silicon oxynitride film is formed.

The liquid crystal panel of the present invention is characterized in that the counter substrate has a thickness of 2 mm or more.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal panel of the present invention will be described in detail below.

In the liquid crystal panel of the present invention, a high refractive index and a low refractive index are alternately laminated on the outer surface side of the counter substrate, and the outermost layer is formed with an antireflection film made of a silicon oxynitride film. Since the silicon oxynitride film is a transparent film and has a refractive index of 1.5 or less, optical characteristics similar to those of a multilayer film using a silica film as the outermost layer can be obtained. Further, the silicon oxynitride film is more flexible than the silica film and is excellent in scratch resistance, so that it is preferable that the silicon oxynitride film is less likely to be peeled off and less likely to be scratched even when contacted with another member. The silicon oxynitride film can be represented by a chemical formula of SiOxNy, where x is 1.9 or less and y is 0.
It is 9 or less. A ratio of (nitrogen / oxygen) in the silicon oxynitride film of 0.01 to 1 (atomic ratio) is more preferable because the film is 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, when the ratio of (nitrogen / oxygen) is greater 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.

In the antireflection film of the present invention, a high refractive index film having a refractive index of 1.9 to 2.4 is formed as the first layer and a refractive index of 1.4 to 1.5 is formed as the second layer from the side of the opposing substrate. Of the low refractive index film, the third layer of the high refractive index film having a refractive index of 1.9 to 2.4, and the outermost layer of the silicon oxynitride film having a refractive index of 1.4 to 1.5, It is preferable because it has very good antireflection properties. 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 above-mentioned first layer, oxidation is used.
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.

Further, in the present invention, when each layer of the antireflection film is formed by magnetron sputtering 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 obtained. It is preferable because it is possible to form a film and mass-produce it at a lower cost.

Further, this antireflection film has a wavelength of 450 to
Since the visible light reflectance at 650 nm is 0.5% or less, an excellent defocus function can be obtained by forming a counter substrate by coating the visible light reflectance on the surface of a heat-resistant glass plate having a thickness of 2.0 mm or more. To be That is, when the antireflection film is formed on the outer surface of the counter 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 from occurring in the switching element. further,
Even if dust adheres to the outer surface of the counter substrate having a thickness of 2 mm or more, the distance between the dust and the liquid crystal, which is the condensing position of the projection light, is increased by the thickness of the counter substrate. This will make the image of garbage
It will be in a defocused state and will be greatly blurred on the screen, making it visually inconspicuous. Therefore, unlike the conventional case, it is not necessary to attach the defocus substrate to the counter substrate, so that the structure and workability can be simplified and the cost can be reduced.

As the material of the counter substrate, crystallized glass,
Quartz glass and borosilicate glass can be used, but 30 to 75
Coefficient of thermal expansion in the temperature range of 0 ° C is -10 to + 15x
10 ^-7/ ° C transparent crystallized glass has very good heat resistance
Has a high thermal conductivity and a large heat dissipation effect,
The heat accumulated in the liquid crystal is conducted to the counter substrate, and the efficiency is improved from here.
It is preferable because it radiates heat well. That is, the counter substrate is
The heat dissipation function tends to decrease as the thickness increases.
However, the counter substrate is made of crystallized glass with high thermal conductivity.
Then, even if the thickness is 2 mm or more, a sufficient heat dissipation function can be obtained.
Be done.

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

Further, in the present invention, when the thickness of not only the counter substrate but also the active matrix substrate is 2 mm or more, even if dust adheres to the outer surface of the active matrix substrate, the distance between the dust and the liquid crystal cell is 2 mm or more. This is preferable because the dust image is in a defocused state.
On the inner surface of this active matrix substrate, the TFT
(Thin Film Transistor) may be formed, and an antireflection film having a four-layer structure as described above may be formed on the outer surface.

However, when the thickness of the counter substrate or the active matrix substrate is too large, the heat dissipation function is significantly deteriorated, and it is difficult to make the liquid crystal panel thin and lightweight. It is desirable to suppress it.

The transparent crystallized glass substrate is a quartz glass substrate.
Since it is cheaper than
Therefore, it is possible to reduce the material cost.
Quartz glass is used as the active matrix substrate.
Preferably. The reason for this is that the quartz glass substrate
Higher visible light transmission than crystallized glass substrates (especially shortwave
This is because it is easy to obtain high image quality (on the long side). Moreover, quartz moth
Lath substrate is about 5 × 10 ^-7Since it has a low expansion of / ° C,
Excellent heat resistance, heat when bonding to a transparent crystallized glass substrate
There is also an advantage that the stress is small.

[0029]

EXAMPLES The liquid crystal panel of the present invention will be described in detail below based on examples.

FIG. 1 is an explanatory view showing a liquid crystal panel of the present invention.

The liquid crystal panel 10 has a structure in which an active matrix substrate 11 and a counter substrate 12 are bonded together with a seal material 13 at a predetermined interval, and a liquid crystal 14 is sealed in the interval between the substrates 11 and 12. Have

The active matrix substrate 11 is made of quartz glass having a thickness of 0.7 mm, and a TFT (not shown) is formed on the inner surface thereof. In addition, the outer surface of the active matrix substrate 11 has a thickness of 0.7.
A defocus substrate 15 made of quartz glass of mm is attached with a resin adhesive, and an antireflection film 16 is formed on the outer surface of the defocus substrate 15.

The counter substrate 12 is made of Li ₂ O--Al ₂ O ₃
-SiO ₂ low expansion transparent crystallized glass substrate (coefficient of thermal expansion: -4 x 10 ^-7 / ° C, visible light transmittance at 3 mm thickness: 8
0% or more, thermal conductivity: 1.7 W / m ° C),
Its thickness is 2.2 mm. Further, an antireflection film 17 is formed on the outer surface of the counter substrate 12 to prevent unnecessary light due to surface reflection from entering the liquid crystal panel, while the inner surface is formed of a transparent ITO film 18. The electrodes and the alignment film 19 are formed.

The ITO film 18 formed on the active matrix substrate 11 and the counter substrate 12 is formed by using a magnetron sputtering film forming apparatus, and the antireflection films 16 and 17 on the defocus substrate 15 and the counter substrate 12 are also magnetron sputtered. A film was formed using the apparatus. The counter substrate 12 is ITO
After forming the film 18, the antireflection film 17 was formed, and then the alignment film 19 was formed on the ITO film 18. When the antireflection film 17 is formed by vacuum vapor deposition, the ITO formed earlier is formed.
It should be avoided as it may deteriorate the membrane 18 due to high heat. Each of the antireflection films 16 and 17 has a four-layer structure,
The formation of each layer was performed under the condition that the O ₂ concentration in Ar was about 20%. Table 1 shows the film configurations (materials and geometrical thickness of each layer) of the antireflection films 16 and 17 formed on the active matrix substrate and the counter substrate, and the wavelengths of 450 nm and 550 nm.
It shows the reflectance at 650 nm.

[0035]

[Table 1]

As is clear from Table 1, the antireflection film 1
Nos. 6 and 17 have a low reflectance of 0.5% or less at a wavelength of 450 to 650 nm, and have sufficiently low reflectance.

Next, the antireflection film 1 of the counter substrate 12 described above.
The scratch resistance of No. 7 was examined by a pencil test. HEID for pencil test
Based on ON surface property test, pencil angle 45 °, scratching speed 100 mm / min, load 200 g, Mitsubishi Pencil H
Performed using I-uni. The antireflection film 17 formed on the counter substrate 12 was tested three times using pencils of 6H and 7H and visually checked for scratches. No scratches occurred.

When this liquid crystal panel 10 is used as a light valve of a liquid crystal projector, even if a minute dust adheres to the outer surface of the counter substrate 12, the image (shadow) of the dust is
It was blurred on the screen and never projected enlarged. Moreover, the heat accumulated in the liquid crystal 14 is efficiently conducted to the counter substrate 12, and the temperature rise is suppressed.

[0039]

As described above, the liquid crystal panel of the present invention has a good antireflection property because the antireflection film using the SiOxNy film as the outermost layer is formed on the counter substrate. Since the anti-reflection film is unlikely to cause scratches on the surface of the film even when it comes into contact with other members, when the distribution film is formed on the ITO film formed on the opposite surface of the anti-reflection film, minute scratches are formed on the anti-reflection film. It is possible to suppress the occurrence of.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a liquid crystal panel of the present invention.

[Explanation of symbols]

10 LCD panel 11 Active matrix substrate 12 Counter substrate 13 Seal material 14 LCD 15 Defocus substrate 16,17 Anti-reflection film 18 ITO film 19 Alignment film

Claims (4)

[Claims] 1. A liquid crystal panel comprising an active matrix substrate, a counter substrate arranged to face the active matrix substrate, and a liquid crystal held in a gap between the substrates, wherein an inner surface side of the counter substrate is provided. , An ITO film is formed, a high refractive index film and a low refractive index film are alternately laminated on the outer surface side, and an antireflection film whose outermost layer is a silicon oxynitride film is formed. LCD panel. 2. The liquid crystal panel according to claim 1, wherein the counter substrate has a thickness of 2 mm or more. 3. An ITO film is formed on one surface, and an antireflection film is formed on the other surface. The antireflection film is formed by alternately stacking a high refractive index film and a low refractive index film, and forming an outermost layer. A counter substrate for a liquid crystal panel, comprising a silicon oxynitride film. 4. A counter electrode is formed on one surface, and an antireflection film is formed on the other surface. In the antireflection film, high refractive index films and low refractive index films are alternately laminated, and an outermost layer is formed. A counter substrate for a liquid crystal panel, comprising a silicon oxynitride film.