JPH08136906A - Liquid crystal panel - Google Patents

Abstract

PURPOSE: To improve outdoor visibility by reducing the reflectivity of light from outside and accordingly, extremely reducing the external light as for a liquid crystal panel which is mainly intended for outdoor use. CONSTITUTION: In this panel, antireflection films are formed on the surfaces of transparent glass substrates, or transparent plastic sheet substrates or transparent plastic film substrates, which is filled with a liquid crystal, and/or in the outer layer part on the atmosphere side of the panel. Each of the antireflection films consists of a three-layer laminated, inorganic dielectric thin film and the optical film thickness of a first and third layers is a quarter of the designed main wavelength of light and the refractive index of the second layer is increased in the depth direction of the film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel, which makes it possible to reduce the reflection of external light and improve the visibility, and particularly to a liquid crystal television or a portable terminal used outdoors. It is possible to improve the visibility of the liquid crystal panel.

[0002]

2. Description of the Related Art A liquid crystal panel is often used indoors in a calm environment such as a monitor for a workstation or a monitor for a personal computer. But in recent years
Cases used in bright outdoor environments are increasing. For example, video cameras with LCD TVs, outdoor LCD TVs, mobile phones, in-vehicle display panels such as navigation systems and head-up displays, and portable displays.
For example, a computer computer. The visibility of these outdoor liquid crystal panels becomes extremely poor due to the reflection of external light on the panel surface and the glass substrate portion. Therefore, in order to impart an antiglare effect to the panel surface, a method has been adopted in which a SiO2 layer having fine irregularities is attached to the surface, or the surface is etched with hydrofluoric acid to provide irregularities. However, these methods are called non-glare processing that scatters external light, and there is a limit to the reduction of reflectance because it is not a method of essentially providing a low reflection layer. It was also a cause of

Therefore, conventionally, an antireflection film formed of a multilayer film formed by a coating method (Japanese Patent Laid-Open No. 59-50401) or a single-layer or two-layer antireflection film formed by a vacuum deposition method (Japanese Patent Laid-Open No. 62-62).
164021) and the like.

[0004]

However, an antireflection film formed of a multilayer film obtained by applying and curing a liquid material lacks uniformity of the refractive index and the film thickness distribution of each layer of the multilayer film. As a result, it is extremely difficult to manufacture a device having a reflectance of 1% or less. In addition, by vacuum deposition method, MgF
_The one coated with a single layer film such as ₂ is well known, but the reflectance is 1% or more. An antireflection film having a reflectance of 1% or less can be produced by forming a multilayer film of two layers or three layers by a vacuum vapor deposition method, but since a reflection type liquid crystal panel used in a mobile terminal has no backlight, High contrast is required and lower reflectance antireflective coatings are needed. Such an antireflection film having an extremely low reflectance can be obtained by forming a multilayer film such as a four-layer film or a five-layer film by a vacuum evaporation method, but the process becomes extremely long, which is not realistic.

[0005]

The liquid crystal panel of the present invention is
In a liquid crystal panel characterized by forming an antireflection film on the surface of a transparent glass substrate filled with liquid crystal, or a transparent plastic sheet substrate, or a transparent plastic film substrate, or / and the atmosphere side outer layer portion of the liquid crystal panel, The antireflection film is a three-layer thin film made of an inorganic dielectric, and the first layer (thin film layer on the base material side) of the three-layer thin film has a refractive index of 1.5 or more and 1.8 or less and an optical property. Film thickness is λ /
4 (λ is the designed main wavelength of light), the refractive index of the third layer (the thin film layer provided on the second layer) is 1.25 or more and 1.5 or less, and the optical film thickness is λ. / 4 (λ is the design dominant wavelength of light), and the refractive index of the second layer changes in the depth direction of the film thickness as described below. _{n 2 = (n 23 -n 21} ) × (L / d 2) X + n 21 0 ≦ L ≦ d 2 1 ≦ x ≦ 4 1.6 ≦ n 21 ≦ 2.2 1.8 ≦ n 23 ≦ 2. 4 1.05 ≦ n ₂₃ / n ₂₁ ≦ 1.2 where n ₂ and d ₂ are the refractive index and film thickness of the second layer, and n ₂₁
Is the refractive index of the surface of the second layer in contact with the first layer, and n ₂₃ is the second
The refractive index L of the surface of the layer in contact with the third layer is the position in the film thickness direction from the first layer to the third layer of the second layer. The antireflection film of the present invention can be produced with a very low reflectance of 1% or less, which is equivalent to that of a four-layer film, in the same process as that for producing a three-layer film.

The antireflection film in the present invention has an extremely low reflectance in the entire wavelength range of visible light, preferably 1
% Or less, more preferably 0.5% or less.

The inorganic layer of the first layer of the antireflection film referred to in the present invention is
Refractive index of 1.5 or more and 1.8 or less as an electric material
And specifically LaF₃(Refractive index of 1.
59 and below are the same in parentheses), NdF₃(1.60), Al
₂O₃(1.62), CeF ₃(1.63), PbF₃
(1.75), MgO (1.75), ThO₂(1.8
0) etc., and refraction as the inorganic dielectric material of the third layer
The rate is 1.25 or more and 1.5 or less, and specifically
CaF₂(1.26), NaF (1.34), Na₃A
IF₆(1.35), LiF (1.37), MgF
₂(1.38), SiO₂(1.46) and so on
It If the refractive index is within the above range, these
Not limited to things. In addition, these two or more types are uniform
It may be mixed or compounded. Also the first
The thickness of the layer and the third layer is n₁d₁= Λ / 4, n₃d₃= Λ /
4 (n₁, N₃Is the refractive index of the first and third layers, d₁, D
₃Is the thickness of the first and third layers, and λ is the design dominant wavelength of light.
It ) Must be satisfied. For example, the designer of light
When the wavelength is 510 nm, Ce is used as the material for the first layer.
F₃(Refractive index of 1.63 at 550 nm), the material of the third layer
Then MgF₃(Refractive index 1.38 at 550 nm) was used
In this case, the thickness of the first layer is 78 nm and the thickness of the third layer is 92 n.
m.

The second layer of the antireflection film according to the present invention has a refractive index increasing in the film thickness direction from the first layer to the third layer,
This change is like the following formula. _{n 2 = (n 23 -n 21} ) × (L / d 2) X + n 21 0 ≦ L ≦ d 2 1 ≦ x ≦ 4 1.6 ≦ n 21 ≦ 2.2 1.8 ≦ n 23 ≦ 2. 4 1.05 ≦ n ₂₃ / n ₂₁ ≦ 1.2 where n ₂ and d ₂ are the refractive index and film thickness of the second layer, and n ₂₁
Is the refractive index of the surface of the second layer in contact with the first layer, and n ₂₃ is the second
The refractive index L of the surface of the layer in contact with the third layer is the position in the film thickness direction from the first layer to the third layer of the second layer.

As a method of forming a thin film in the present invention,
In addition to the vacuum vapor deposition method, a physical vapor deposition method such as a sputtering method and an ion plating method, a chemical vapor deposition method such as a CVD method, and the like are used, but the present invention is not limited thereto. Regarding the vacuum evaporation method, electron beam heating, laser beam heating, resistance heating,
However, the present invention is not limited to these. In the case of electron beam heating or laser beam heating, the electron gun or laser may be a single unit or a plurality of units. Regarding the vacuum vapor deposition method and the sputtering method,
Introduce oxygen, nitrogen, steam, etc. as reactive gas,
Reactive vapor deposition using ozone, ion assist, or the like, reactive sputtering, or the like can also be used.
Further, a deposition condition such as applying a bias to the substrate or raising or cooling the substrate temperature may be changed.

By continuously increasing the refractive index of the second layer, it is possible to realize an extremely low reflectance as high as that of a four-layer thin film, and the productivity can be increased because the film can be formed in one step. X showing the form of the change of the refractive index with respect to the film thickness direction
When the value is 1 or less, the refractive index rapidly increases in the layer near the first layer, which is substantially the same as the uniform thin film layer having almost no change in the refractive index. X like this
When is larger than 4, the refractive index of the third neighboring layer is sharply increased, which is substantially the same as a uniform thin film layer having almost no change in refractive index. Therefore, the range of 1 ≦ x ≦ 4 is preferable. The thickness of the second layer is n
It is necessary to satisfy the condition of ₂₁ d ₂ = λ / 4.

Of the refractive index of the second layer, the range of the refractive index n ₂₃ of the portion facing the third layer is 1.05 ≦ n ₂₃ / n ₂₁
It must be ≦ 1.2. 1.0 ≦ n ₂₃ / n ₂₁ <
At 1.05, it is difficult to say that the refractive index is changing in the film thickness direction, and only a reflectance equivalent to that of a homogeneous thin film is exhibited. 1.0
When> n ₂₃ / n ₂₁ , the reflectance of the designed dominant wavelength becomes high. When 1.2 ≧ n ₂₃ / n ₂₁ , the reflectance in the vicinity of the designed main wavelength is extremely low, but on the contrary, the low reflectance band becomes narrow, and the reflectance on the low wavelength side and the high wavelength side in the visible light region is decreased. Will become bigger. Therefore, in order to obtain an extremely low reflectance in the entire visible light wavelength region, 1.05 ≦ n ₂₃
The range of / n ₂₁ ≦ 1.2 is preferable.

The thin film layer in which the refractive index continuously changes between one layer can be prepared by arranging two materials adjacent to each other in the moving direction of the glass substrate, the plastic sheet substrate, or the plastic film substrate. . As this material, the material on the first layer side is NdF.
₃ (1.6), Al ₂ O ₃ (1.62), CeF
₃ (1.63), PbF ₃ (1.75), MgO (1.
75), ThO ₂ (1.80), SnO ₂ (1.9).
_{0), Ln 2 O 3 (} 1.95) SiO (1.7~2.
0), In ₂ O ₃ (2.00), Nd ₂ O ₃ (2.0
0), Sb ₂ O ₃ (2.04), ZrO ₂ (2.1
0), CeO ₂ (2.2) and the like, and as the material of the third layer side, Th0 ₂ (1.80), SnO ₂ (1.2.
90), Ln ₂ O ₃ (1.95), In ₂ O ₃ (2.0
0), Nd ₂ O ₃ (2.00), Sb ₂ O ₃ (2.0
4), ZrO ₂ (2.10), CeO ₂ (2.2). T
Examples include iO ₂ (2.2 to 2.4) and ZnS (2.35). Further, if it is within the range of the refractive index, it is not limited to these.

As another method for continuously changing the refractive index between one layer, even if only one material is vaporized, a space with a large number of excited vapor deposition particles and a space with a small number of excited vapor deposition particles are formed and formed. The refractive index can be changed by continuously changing the filling rate of the formed thin film. Specifically, in order to partially increase the number of excited vapor-deposited particles in the film forming space, an electromagnetic wave such as a laser, a microwave, or a high frequency is incident, or an electron beam, an ion beam, or a negative ion beam.
This can be realized by injecting a particle beam such as a beam of particles or a beam of neutral particles. On the contrary, the energy of vapor deposition particles
In order to reduce the amount, the gas particles may be caused to collide with the vapor deposition particles by partially flowing the gas into the film formation space. The method is not limited to these methods as long as the number of excited vapor deposition particles can be controlled.

The plastic sheet or plastic film referred to in the present invention is obtained by melt-extruding or solution-casting an organic polymer and, if necessary, stretching, cooling and heat setting in the longitudinal direction and / or the axial direction. The film is an organic polymer, and examples of the organic polymer include polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, nylon 6, nylon 4, nylon 66, nylon 12, polyvinyl chloride, polychlorine. Vinylidene, polyvinyl alcohol, wholly aromatic polyamide, polyamideimide, polyimide, polyetherimide, polysulfane, polyphenylene sulfide, polyphenylene oxide, polycarbonate, polyethersulfone, polyarylate and the like. To be Further, these (organic polymer) organic polymers may be copolymerized or blended with a small amount of another organic polymer.

Further, known additives such as an ultraviolet absorber, a plasticizer, an antistatic agent and a lubricant may be added to the organic polymer. In addition, the base material made of these organic polymers is subjected to corona treatment, glow discharge treatment, and other surface roughening treatment prior to laminating the thin film layer, unless the object of the present invention is impaired. May be given,
Further, known anchor coat treatment, printing, decoration, etc. may be applied. The base material of the present invention has a thickness of 5 to 50.
It is preferably 0 μm, more preferably 10 to 300 μm.

The glass substrate referred to in the present invention means glass such as soda lime aluminosilicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, quartz glass and single crystals such as corundum, magnesia and sialon. Examples include translucent ceramics, but the present invention is not limited to these.

As the liquid crystal of the liquid crystal panel in the present invention,
Not only TN type and STN type liquid crystal using general nematic liquid crystal but also ferroelectric liquid crystal, antiferroelectric liquid crystal, polymer dispersed liquid crystal are mentioned, and liquid crystal used for these is nematic, cholesteric, smectic. A liquid crystal may be mentioned, and a mixture of two or more of these may be used. Next, the present invention will be described with reference to examples.

[0018]

Example 1 Using an aluminosilicate glass having a thickness of 0.5 mm as a glass substrate, an antireflection film composed of a three-layer thin film was first prepared. A vacuum deposition method using electron beam heating was used as a film forming method. As a vapor deposition material for forming the first layer,
3-5 mm sized particulate CeF ₃ (purity 99.9
%), As a vapor deposition material for forming the third layer, particulate MgF ₂ having a size of about 3 to 5 mm was used. In order to form the second refractive index gradient layer, ZrO _{2 in the} form of particles having a size of about 3 to 5 mm (purity 99.9%) and 3 to 5 mm are used.
Two kinds of materials of TiO ₂ (purity 99.9%) in the form of particles having a size of the order of magnitude were used. First, a first layer made of CeF ₃ was formed by a usual electron beam evaporation method. The input power from the electron gun at this time was fixed at 35 kW. The thickness of the first layer was set to 84 nm in order to set the designed dominant wavelength of light to 550 nm. In order to form the second layer, ZrO ₂ was put in the crucible on the front side in the moving direction of the glass, and TiO ₂ was put in the crucible on the back side in the moving direction. At this time, the distance between the two crucibles is
It was set to 1/5 of the distance between the substrates. At this time, one electron gun was used to heat each of ZrO ₂ and TiO _{2 in} a time-division manner, and by changing this ratio, the changing shape of the refractive index in the film thickness direction was changed. The input power was constant at 60 kW, and the flow rate of oxygen gas was 130 cc / min. And The thickness of the second layer was 131 nm because the designed dominant wavelength of light was 550 nm. In order to form the third layer, the input power from the electron gun was set to 20 kW to form a MgF ₂ thin film. The thickness of the third layer is 100 nm because the designed dominant wavelength of light is 550 nm.
And As described above, the glass feed rate when forming three layers is 5
m / min. The substrate temperature was kept constant at 80 ° C.

The composition distribution in the film thickness direction of the three-layer thin film thus obtained was measured by Auger electron spectroscopy. At this time, Zr-MNN, Ti-LMM, O-KLL, Ce-
The measurement was performed while sputtering the thin film using Auger transition signals of MNN, F-MNN, F-KLL, and Mg-KLL. The distribution of the refractive index calculated from these in the film thickness direction is shown in FIG.

Further, the spectrophotometric characteristics of the antireflection film formed of the three-layer thin film in the visible light region were measured. Measurement wavelength is 300n
It carried out in the range of m to 800 nm. As a result of this measurement, as shown in FIG. 2, an antireflection film having an extremely low reflectance of 0.2% or less in the entire visible light wavelength region was obtained.

A transparent electrode made of ITO was formed on one surface of the glass substrate prepared as described above by a sputtering method, patterned into a desired electrode pattern, and then the surface of the substrate was flattened by using a smoothing agent. An alignment film made of polyimide was coated on this surface by a gravure printing method, and then a rubbing treatment was performed. The glass substrates were pasted together with the surfaces subjected to the orientation treatment facing each other, the ends of the substrates were sealed with an epoxy resin, and STN type liquid crystal was injected between the substrates.

Polarizing plates located on both sides of the glass substrate
The polarizing layer is made of PVA-iodine,
It was used after being sanded with a protective layer. This polarizing plate
Then, on the surface that becomes the outermost layer on the atmosphere side,
Similar three-layer thin film (first layer CeF ₃, Second layer ZrO₂-T
iO₂Antireflection coating consisting of a gradient refractive index layer and a third layer MgF)
A stop membrane was created.

As a result of measuring the reflectance of the STN type liquid crystal panel produced as described above, it was 1.5%, which showed sufficient visibility even in outdoor use.

[0024]

Comparative Example 1 The same glass substrate as in Example 1 and an antireflection film composed of a three-layer thin film were formed on the surface of a polarizing plate. First
A thin film of CeF ₃ for the layer, ZrO _{2 for} the second layer, and MgF for the third layer having a uniform refractive index was prepared by the electron beam evaporation method. Example 1 except that the vapor deposition material for the second layer was one type
A film was formed in the same manner as in. The thickness of each layer is such that the designed dominant wavelength of light is 550 nm, so the first layer 84 nm and the second layer 131
nm and the third layer 100 nm. The distribution of the refractive index of this antireflection film in the film thickness direction was uniform in each layer as shown in FIG. Further, as a result of measuring the spectrophotometric characteristics of the antireflection film in the visible light region in the same manner as in Example 1, there was a region having a reflectance of 0.5% in the visible light wavelength region. A liquid crystal panel was assembled using the glass substrate and the polarizing plate in the same manner as in Example 1. The light reflectance of this panel was measured and found to be 5.8%. There was a lot of crowding and the visibility was not good.

[0025]

Example 2 A 100 μm thick polycarbonate is used as a liquid crystal filled substrate.
-Bone film is used, and electron beam is used as a film forming method.
A vacuum evaporation method by heating was used. Vapor deposition to form the first layer
As a material, granular Al having a size of 3 to 5 mm₂O₃
(Purity of 99.95%) as a vapor deposition material for forming the third layer
Particle size Na of about 3-5 mm₃AlF ₆
(Purity of 99.98%) was used. Second refractive index gradient layer
To form a particle having a size of about 3 to 5 mm.
CeO2 (purity 99.95%) and 3-5 mm
Two types of ZnS (purity 99.9%) in the form of particles
Material was used. First, Al2 O is formed by the usual electron beam evaporation method.
A first layer of 3 was formed. Throw from the electron gun at this time
The input power was fixed at 60 kW. To form the second layer
, Put CeO2 into the crucible on the front side of the film running direction.
Insert ZnS into the crucible on the back side in the film running direction.
Was. At this time, the distance between the two crucibles is set between the crucible and the chill roll.
It was set to 1/6 of the distance. At this time, using one electron gun, C
Each of eO2 and ZnS is heated in a time division manner, and the ratio is
By changing it, the changing shape of the refractive index in the film thickness direction was changed. Throw
The input power is constant at 80 kW and the flow rate of oxygen gas is 70 c
c / min. And Electron gun for forming the third layer
The input power from the unit is 35 kW and the Na3 AlF6 thin film is
Formed. Above, the film feed speed when forming three layers
Is 100 m / min. And the temperature of the chill roll is 120
It was kept constant at ℃.

The composition distribution in the film thickness direction of the three-layered thin film obtained as described above was measured by Auger electron spectroscopy as in Example 1. At this time, Al-LMM, Na-KLL, F
-KLL, Ce-MNN, Zn-LMM, S-LMM,
The thin film was measured while being sputtered using the signal of the Auger transition of O-KLL, and the distribution of the refractive index calculated from these in the film thickness direction is shown in FIG.

Further, the spectrophotometric characteristics in the visible light region of the antireflection film made of a three-layer thin film were measured. Measurement wavelength is 30
It carried out in the range of 0 nm to 800 nm. As a result of this measurement, an antireflection film having an extremely low reflectance of 0.25% or less in the entire visible light wavelength region was obtained.

Using the polycarbonate film with the antireflection film and the polarizing plate, the same process as in Example 1 was carried out.
A TN type liquid crystal panel was assembled. The light reflectance of this panel was 1.6%, and it was excellent in visibility with little reflection of external light even when used outdoors.

[0029]

Comparative Example 2 An antireflection film was formed on the same polycarbonate film and polarizing plate as in Example 2, and the vacuum deposition method by electron beam heating was used as the film forming method. Al2 O3 is used as the vapor deposition material for the first layer, and CeO2 and Zn are used for the second layer.
S, the third layer was Na3 AlF6. The measurement result of the change in the refractive index of the three-layer thin film in the film thickness direction is shown in FIG. Further, as a result of measuring the spectrophotometric characteristic in the visible light region in the same manner as in Example 2, there was a region having a reflectance of 0.55%. Using this glass substrate and polarizing plate, the STN was prepared in the same manner as in Example 1.
A type liquid crystal panel was assembled, and the light reflectance of this panel was measured and found to be 6.5%. In addition, external light was often reflected in the outdoor use, and the visibility was not good.

[0030]

EFFECTS OF THE INVENTION The liquid crystal panel using the specific antireflection film of the present invention makes it possible to display with good visibility even in the outdoors with less reflection of external light. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of the distribution of the refractive index of a three-layer antireflection film in the present invention in a film thickness direction.

FIG. 2 is an explanatory diagram showing an example of spectrophotometric measurement of a three-layer antireflection film according to the present invention.

FIG. 3 is a film thickness direction distribution of the refractive index of the three-layer antireflection film in Comparative Example 1.

FIG. 4 is an explanatory diagram showing another example of the distribution of the refractive index of the three-layer antireflection film in the film thickness direction in the present invention.

FIG. 5 is an explanatory view schematically showing a structure of an STN type liquid crystal panel according to the present invention.

[Explanation of symbols]

(1-1-1), (1-4-1), (2-4-1) ... First layer of antireflection film (1-1-2), (1-4-2), (2- 4-2) ... Second layer of antireflection film (1-1-3), (1-4-3), (2-4-3) ... Third layer of antireflection film (1-2), ( 2-2) ... Polarizing plate (1-3), (2-3) ... Glass substrate (1-5), (2-5) ... Surface smoothing agent (1-6), (2-6) ... Transparent electrode (1-7), (2-7) ... Alignment film (3) ... Liquid crystal

Claims (1)

[Claims] 1. An antireflection film is formed on the surface of a transparent glass substrate, a transparent plastic sheet substrate, or a transparent plastic film substrate filled with liquid crystal of a liquid crystal panel, and / or on the atmosphere side outer layer portion of the liquid crystal panel. In a liquid crystal panel characterized by:
A three-layer thin film made of an inorganic dielectric, the first of the three-layer thin film being
The refractive index of the layer (the thin film layer on the base material side) is 1.5 or more and 1.8 or less, the optical film thickness is λ / 4 (λ is the design dominant wavelength of light), and the third layer (second The refractive index of the thin film layer provided on the layer is 1.25 or more and 1.5 or less, and the optical film thickness is λ / 4.
(Λ is the designed main wavelength of light), and the refractive index of the second layer is sequentially changed in the film thickness direction as follows. _{n 2 = (n 23 -n 21} ) × (L / d 2) X + n 21 0 ≦ L ≦ d 2 1 ≦ x ≦ 4 1.6 ≦ n 21 ≦ 2.2 1.8 ≦ n 23 ≦ 2. 4 1.05 ≦ n ₂₃ / n ₂₁ ≦ 1.2 where n ₂ and d ₂ are the refractive index and film thickness of the second layer, and n ₂₁
Is the refractive index of the surface of the second layer in contact with the first layer, and n ₂₃ is the second
The refractive index L of the surface of the layer in contact with the third layer is the position in the film thickness direction from the first layer to the third layer of the second layer.