JP3322070B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat display device,
More specifically, the present invention relates to a liquid crystal display device that can eliminate a transmittance offset state due to the polarity of a voltage applied to a liquid crystal layer as an electro-optical material layer.

[0002]

2. Description of the Related Art A basic cross-sectional structure of a typical color liquid crystal display device as a flat display device is shown in FIG. The liquid crystal display device 30 shown in FIG. 9 has a first transparent substrate 32 and a second transparent substrate 34.

On the inner surface of the first transparent substrate 32, a first transparent electrode layer 36, a color filter layer 38 and a first alignment film 40 are laminated in this order. On the outer surface of the first transparent substrate 32, a first polarizing plate 48 is mounted.
A second transparent electrode layer 42 is provided on the inner surface of the second transparent substrate 34.
And a second alignment film 44 are stacked in this order. Further, the second polarizing plate 50 is provided on the outer surface of the second transparent substrate 34.
Is installed. The first and second transparent electrode layers 36 and 42
For example, it is composed of an ITO film or the like. In addition, ITO
It is an indium oxide doped with tin as a different additive, and is excellent in conductivity while being transparent.

Then, liquid crystal is injected into a gap between the first alignment film 40 and the second alignment film, and a liquid crystal layer 46 is formed. When the color filter layer 38 is formed by a dyeing method, for example, a natural polymer material such as gelatin, casein, glue or the like, or a synthetic polymer material such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone is used as a substrate, Alternatively, it contains a dye such as a reactive dye and is made of an organic substance. When a color filter layer is formed by a pigment dispersion method, this layer is made of, for example, an organic material mainly containing an acrylic resin or polyvinyl alcohol (PVA). When a color filter layer is formed by an electrodeposition method, this layer is made of an organic substance containing a polyester resin, a melamine resin, or the like as a main component.

The first and second alignment films 40 and 44 are made of an organic substance such as a polyimide resin. In the conventional liquid crystal display device 30, as shown in FIG. 9, the first transparent electrode layer 36 is in contact with the organic film constituting the color filter layer 38, and the second transparent electrode layer 42 is in contact with the second transparent electrode layer 42. The organic films constituting the alignment film 44 are in contact with each other, and the two electrode layers 36,
An organic film having a different material and / or thickness is in contact with 42.

A voltage corresponding to the potential difference between the two electrode layers 36 and 42 is applied to the liquid crystal layer 46 to drive the liquid crystal. In addition, the polarity of the voltage applied to the liquid crystal layer 46 in the liquid crystal constituting the liquid crystal layer 46 in order to prevent the deterioration of the liquid crystal,
It is inverted every predetermined period (AC drive).

[0007]

When an organic film of a different material and / or thickness is in contact with both electrode layers 36 and 42, the voltage is applied from both electrode layers 36 and 42 as shown in FIG. It has been confirmed by the present inventors that the transmittance of the liquid crystal layer 46 becomes asymmetric depending on the polarity of the voltage. In addition,
In FIG. 10, the horizontal axis represents the potential difference between the first electrode layer 36 and the second electrode layer 42, and the plus side represents the case where the first electrode layer 36 has a positive potential with respect to the second electrode layer 42. The minus side is the opposite. The vertical axis represents the transmission intensity of the liquid crystal layer 46.

As described above, due to the asymmetry of the transmittance with respect to the applied voltage, when the liquid crystal display device 30 is driven by an alternating current, an offset voltage is spontaneously generated at both ends of the liquid crystal layer, and the screen flickers. Cause. In addition, it causes deterioration of the liquid crystal. Such a phenomenon similarly occurs in a monochrome liquid crystal display device without a color filter film, even when the alignment film sandwiching the liquid crystal layer is made of a different material.

The present invention has been made in view of such a situation, and eliminates an offset voltage spontaneously generated when a voltage is applied inside a flat display device, thereby eliminating one of the causes of screen flicker. It is an object of the present invention to provide a flat display device capable of improving display quality.

[0010]

Means and Functions for Solving the Problems The present inventor has provided:
The cause of the offset voltage is examined, and it is found that the cause of the offset voltage is that an organic film is directly laminated on the surface of the electrode layer. It has been found that the offset voltage can be eliminated by laminating an organic film via the inorganic film of the present invention, and the present invention has been completed. It is considered that the inorganic film is less likely to trap charges than the organic film.

Preferred embodiments of the present invention are described below. In the liquid crystal display device according to the present invention , the second surface is provided on one surface side of the liquid crystal layer.
(1) First organic film layer including alignment film and color filter layer
And a first transparent electrode layer, and the other of the liquid crystal layers
A second organic film layer including a second alignment film and a second transparent film
A bright electrode layer, wherein the first organic film layer and the first
Between a transparent electrode layer, and between the second organic film layer and the second
Between the first and second transparent electrode layers between the first and second transparent electrode layers.
The internal offset voltage due to the polarity of the voltage applied to the
And first and second inorganic films are provided.

[0012]

The inorganic film is, for example, a silicon oxide film,
For example, a silicon nitride film is used. The inorganic film is preferably an inorganic film that does not trap charges. The thickness of the inorganic film is not particularly limited, but is preferably about 0.1 to 0.3 μm. The electro-optic material layer is made of, for example, liquid crystal or ferroelectric ceramic.

[0014]

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a flat display device according to the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic cross-sectional view of a main part of a flat panel display according to an embodiment of the present invention.
(A) is a schematic diagram showing a light transmittance test device, FIG. 2 (B)
FIG. 3 is a diagram illustrating a waveform of a voltage applied during a test, FIG. 3 is a graph illustrating transmission intensity with respect to an applied voltage of the flat display device according to the present embodiment, and FIG. 4 is a diagram illustrating a flat display device according to another embodiment of the present invention. FIG. 5 is a schematic perspective view of a main part of the flat display device shown in FIG. 4, FIG. 6 is a diagram showing an example of the arrangement of electrodes of the flat display device shown in FIG. 5, and FIG. 7 is a flat display device shown in FIG. FIG. 8 is a diagram showing driving waveforms of the cathode voltage and the data voltage.

First Embodiment As shown in FIG. 1, a flat display device 60 according to this embodiment is shown.
Has a first transparent substrate 62 and a second transparent substrate 64. These substrates 62 and 64 are made of, for example, a glass substrate.

On the inner surface of the first transparent substrate 62, a first transparent electrode layer 66, a first inorganic film 68, a color filter layer 7
0 and the first alignment film 72 are stacked in this order. Further, a first polarizing plate 82 is provided on the outer surface of the first transparent substrate 62.
Is installed. On the inner surface of the second transparent substrate 64, a second transparent electrode layer 74, a second inorganic film 76, and a second alignment film 7 are formed.
8 are stacked in this order. Also, the second transparent substrate 64
A second polarizing plate 84 is mounted on the outer surface of the. The first and second transparent electrode layers 66 and 74 are composed of, for example, an ITO film or the like. ITO is an indium oxide doped with tin as a different additive, and has excellent conductivity while being transparent. The thickness of these electrode layers 66 and 74 is
Although not particularly limited, it is 0.2 μm in this embodiment.

Then, the first alignment film 72 and the second alignment film 78
The liquid crystal is injected into the gap between them, and the liquid crystal layer 80 is formed. The liquid crystal injected into the liquid crystal layer 80 is not particularly limited, and nematic liquid crystal, cholesteric liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, polymer dispersed liquid crystal, or the like can be used.

The color filter layer 70 is necessary for performing color display. For example, when formed by a dyeing method, a natural polymer material such as gelatin, casein, glue, or polyvinyl alcohol (PVA) is used. ), A synthetic polymer material such as polyvinylpyrrolidone as a substrate, which contains a dye such as an acid dye or a reactive dye, and is composed of an organic substance. When a color filter layer is formed by a pigment dispersion method, this layer is made of, for example, an organic material mainly containing an acrylic resin or polyvinyl alcohol (PVA). When a color filter layer is formed by an electrodeposition method, this layer is made of an organic substance containing a polyester resin, a melamine resin, or the like as a main component. The thickness of the color filter layer 70 is not particularly limited, but is 1 μm in the present embodiment.

The first and second alignment films 72 and 78 are made of, for example, an organic material such as a polyimide resin, and the rubbing treatment controls the pretilt angle of liquid crystal molecules. The thickness of each of the alignment films 72 and 78 is not particularly limited, but is 0.05 μm in this embodiment.

The first and second polarizing plates 82 and 84 have a structure in which a polarizing substrate (PVA) containing a polarizing element (iodine, dye) is sandwiched between transparent substrates (TAC: triacetyl rose) from both sides. , And the thickness is about 0.12 to 0.18 mm. By arranging the polarizing plates 82 and 84 on both sides of the liquid crystal layer 80, transmission and non-transmission of light for each pixel can be controlled according to a voltage for driving the liquid crystal layer 80.

In this embodiment, the color filter layer 70 is provided inside the first transparent electrode layer 66 with the first inorganic film 68 interposed therebetween.
And a first organic film layer including a first alignment film 72 and the like . A second organic film layer including a second alignment film and the like is provided inside the second transparent electrode layer 74 via a second inorganic film 76. Laminated. In this embodiment, the first inorganic film 68 and the second inorganic film 7
6 is composed of silicon oxide. The thickness of the first inorganic film 68 and the second inorganic film 76 is 0.2 μm in this embodiment.
It is.

The voltage of the flat panel display 60 according to the present embodiment
In order to examine the light transmission intensity (transmittance) characteristics, a measurement device (a liquid crystal evaluation device manufactured by Otsuka Electronics Co., Ltd.) shown in FIG. 2A was used.
As shown in FIG. 2A, the display device 60 includes a thermostat 86
And placed between the light source 88 and the luminance meter 87. The inside of the thermostat 86 was kept at 25 ° C. As shown in FIG. 2, a power supply 89 is provided between the electrode layers 66 and 74 of the display device 60.
A voltage having a waveform shown in (B) was applied. In the voltage waveform shown in FIG. 2B, the plus side is a case where the first transparent electrode layer 66 shown in FIG. 1 has a positive potential with respect to the second transparent electrode layer 74, and the minus side is the opposite. .

FIG. 3 shows the results. In FIG. 3, the horizontal axis represents the first
The potential difference between the transparent electrode layer 66 and the second transparent electrode layer 74 is positive when the first transparent electrode layer 66 has a positive potential with respect to the second transparent electrode layer 74, and the negative side is the reverse. It is. The vertical axis indicates the transmission intensity of the liquid crystal layer 80. The transmission intensity was set to 100% when the voltage was 0 in the normally white mode.

On the other hand, as shown in FIG. 9, a similar test was performed using a flat display device having the same structure as that of the above embodiment except that no inorganic film was used. Obtained. In comparison with FIG. 10, as shown in FIG. 3, in the present embodiment, the asymmetry of the transmittance characteristics is improved by interposing an inorganic film such as a silicon oxide film between the transparent electrode layer and the organic film. It was confirmed that the internal offset voltage due to the polarity of the applied voltage disappeared. If the internal offset voltage can be eliminated, one of the causes of the screen flicker can be eliminated, and the display quality of the flat display device can be improved.

Second Embodiment As shown in FIG. 4, a flat panel display 100 according to this embodiment is shown.
Is a plasma addressed display device. First, FIGS.
The outline of the plasma addressed display device will be described based on the above.

As shown in FIG. 5, the plasma addressed display panel 100 has a flat panel structure in which an electro-optical display cell 1, a plasma cell 2, and a dielectric sheet 3 interposed therebetween are laminated. Dielectric sheet 3
Is made of thin glass or the like. The dielectric sheet 3 needs to be as thin as possible in order to drive the display cell 1, and is made of, for example, thin glass having a thickness of about 50 μm.

The display cell 1 is constructed using an upper transparent glass substrate (upper substrate) 4. A plurality of row electrode layers (data electrodes) 5 made of a transparent conductive material and extending in the row direction (vertical direction) are provided on the inner main surface of the upper substrate 4 at predetermined intervals along the row direction in the column direction. (Horizontal direction) are formed in parallel. The upper substrate 4 is joined to the dielectric sheet 3 while maintaining a predetermined gap by a spacer (not shown). The gap between the upper substrate 4 and the dielectric sheet 3 is filled with a liquid crystal as an electro-optical material to form a liquid crystal layer 7. Here, the dimension of the gap between the upper substrate 4 and the dielectric sheet 3 is, for example, 4 to 10 μm, and is kept uniform over the entire display surface. In FIG. 5, the first alignment film 72 and the second alignment film 78 arranged on both sides of the liquid crystal layer 7 shown in FIG. 4 are omitted. Further, the color filter layer 70 and the inorganic film 68 shown in FIG. 4 are also omitted.
These will be described later.

On the other hand, the plasma cell 2 is configured using a lower transparent glass substrate (lower substrate) 8. On the inner main surface of the lower substrate 8, a plurality of anode electrodes 9 and cathode electrodes 11 constituting a plasma electrode and extending in the column direction are alternately formed in parallel in the row direction at predetermined intervals. In addition, approximately in the center of each upper surface of the anode electrode 9,
The partition walls 10 each having a predetermined width so as to extend along the respective electrodes.
Is formed. The top of each partition 10 is in contact with the lower surface of the dielectric sheet 3 so that the size of the gap between the lower substrate 8 and the dielectric sheet 3 is kept constant. The partition 10 is formed in a stripe shape by, for example, screen printing, and is made of a material mainly composed of glass. The positional relationship between the anode electrode 9 and the cathode electrode 11 can be variously modified, and may be the reverse of FIG.

A frit sealing material (not shown) using a low-melting glass or the like is provided along the periphery of the lower substrate 8, and the lower substrate 8 and the dielectric sheet 3 are provided.
Are hermetically joined. An ionizable (dischargeable) gas is sealed in the gap between the lower substrate 8 and the dielectric sheet 3. As the gas to be sealed, for example, helium,
Neon, argon, or a mixed gas thereof is used.

In the gap between the lower substrate 8 and the dielectric sheet 3, a plurality of discharge channels (spaces) 12 extending in the column direction and separated by each partition 10 are formed in parallel in the row direction.
That is, the discharge channel 12 is formed so as to be orthogonal to the row electrode layer 5. Each row electrode layer 5 serves as a column drive unit. Further, as described later, since the anode electrodes 9 are connected in common and an anode voltage is supplied, each of the cathode electrodes 11 is connected.
Are the row drive units. Then, at the intersection of the two, as shown in FIG.
3 are defined.

In the above configuration, the anode electrode 9 and the cathode electrode 1 corresponding to a predetermined pair of discharge channels 12 are provided.
When a predetermined voltage is applied to the discharge channel 1, the gas in the portions of the pair of discharge channels 12 is selectively ionized to generate plasma discharge, and the inside thereof is maintained at substantially the anode potential. In this state, when a data voltage is sequentially applied to the row electrode layer 5, the liquid crystal layers 7 of the plurality of pixels 13 arranged in the column direction corresponding to the pair of discharge channels 12 in which the plasma discharge has occurred.
Then, a data voltage is written via the dielectric sheet 3. When the plasma discharge ends, the discharge channel 12 becomes a floating potential, and the data voltage written in the liquid crystal layer 7 of each pixel 13 is held by the action of the dielectric sheet 3 until the next writing period (for example, after one frame). You. In this case, the discharge channel 12 functions as a sampling switch, and the liquid crystal layer 7 and / or the dielectric sheet 3 of each pixel 13 functions as a sampling capacitor.

Since the liquid crystal operates by the data voltage written in the liquid crystal layer 7 of each pixel 13, display is performed in pixel units. Therefore, as described above, the liquid crystal layer 7 of the plurality of pixels 13 arranged in the column direction by generating the plasma discharge is formed.
A two-dimensional image can be displayed by sequentially scanning a pair of discharge channels 12 in which data voltages are written in the row direction.

FIG. 7 shows a circuit configuration of the plasma addressed display device 100 described above. In this FIG.
5 and 6 are denoted by the same reference numerals. Reference numeral 21 denotes a liquid crystal driver.
Is supplied with video data (DATA). The liquid crystal driver 21 data voltages DS ₁ to DS _m of a plurality of pixels constituting each line every horizontal period is output at the same time, the data voltages of the plurality of pixels DS ₁ to DS _m each buffer 22 ₁ through 22 _m It is supplied to a plurality of data electrodes 5 ₁ to 5 _m through.

The operation of the liquid crystal driver 21 is controlled by the control circuit 23. The control circuit 23 is supplied with a horizontal synchronization signal HD and a vertical synchronization signal VD corresponding to video data (DATA) as synchronization reference signals. Also,
The control circuit 23 also controls the operations of an anode driver 24 and a cathode driver 25 described later.

Reference numeral 24 denotes an anode driver. Anode voltage VA as a reference voltage is supplied to the plurality of anode electrodes 9 ₁ to 9 _n connected in common from the anode driver 24. Reference numeral 25 denotes a cathode driver. The cathode voltage VK ₁ ~VK _n-1 sequentially anode potential and a predetermined potential difference to the plurality of cathode electrodes 11 ₁ ~11 _n-1 from the cathode driver 25 is supplied to every horizontal period. As a result, a plasma discharge is sequentially generated in the discharge channels 12 corresponding to the cathode electrodes 11 _{1 to} 11 _n−1 for each horizontal period, and therefore, the plurality of pixels 1 arranged in the column direction (horizontal direction) are arranged.
The pair of discharge channels 12 for writing the data voltages DS _{1 to} DS _m to the liquid crystal layer 7 of No. 3 are sequentially scanned in the row direction (vertical direction).

Here, the cathode voltage applied to the cathode electrode 11 and the data voltage D applied to the row electrode layer 5
S will be described. Figure 8 (A) ~ (D) shows a cathode voltage VK _a ~VK _{a + 3} which are respectively applied to the cathode electrode 11 _a ~11 _{a + 3} consecutive, FIG (E)
Indicates a data voltage DS applied to a predetermined row electrode layer 5. The cathode electrode 11 _a ~11 _{a + 3,} the cathode voltage VK _a ~VK _{a + 3} of the anode potential and a predetermined potential difference in each 1 horizontal period each successive every frame (1H)
Is applied. Thus, the discharge channels 12 for generating the plasma discharge are sequentially scanned in the row direction (vertical direction). The polarity of the data voltage DS is inverted with respect to the anode potential every horizontal period and every frame, and the liquid crystal layer 7 is AC-driven. The AC driving of the liquid crystal layer 7 is performed by
This is for preventing the deterioration of the liquid crystal.

In this embodiment, in such a plasma addressed display device 100, as shown in FIG. 4, the color filter layer 70 and the first alignment film 7 are directly applied to the row electrode layer 5.
An inorganic film 68 made of a silicon oxide film is interposed without stacking organic films such as No. 2.

On the plasma cell side of the liquid crystal layer 7, a second alignment film 78 as an organic film is laminated on the surface of the dielectric sheet 3 as an inorganic film. Plasma address display device 10
In the case of 0, since the dielectric sheet 3 as an inorganic film is necessarily required, the organic film is not laminated on the surface of the electrode layer by laminating the second alignment film which is an organic film on this surface.

Also in this embodiment, the organic film such as the color filter layer 70 and the first alignment film 72 is not directly laminated on the electrode layer 5, but the inorganic film 6 made of a silicon oxide film is used.
8, the asymmetry of the transmittance characteristic is improved and the internal offset voltage due to the polarity of the applied voltage is eliminated for the same reason as in the first embodiment. If the internal offset voltage can be eliminated, one of the causes of the screen flicker can be eliminated, and the display quality of the flat panel display device 100 can be improved.

The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention.

[0042]

As described above, according to the present invention, it is possible to eliminate an offset voltage which is spontaneously generated when a voltage is applied to a flat display device. Thereby, one of the causes of the flicker on the screen can be eliminated, and the display quality can be improved.

In the plasma addressed display device, since an organic film is not originally laminated on the surface of the electrode layer on the plasma cell side, an inorganic film is interposed on the surface of the electrode layer disposed on the liquid crystal cell side. An organic film may be interposed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a flat panel display according to an embodiment of the present invention.

FIG. 2A is a schematic diagram showing a light transmittance test device, and FIG. 2B is a diagram showing a waveform of a voltage applied during a test.

FIG. 3 is a graph showing a transmission intensity with respect to an applied voltage of the flat panel display according to the present embodiment.

FIG. 4 is a schematic sectional view of a flat panel display according to another embodiment of the present invention.

FIG. 5 is a schematic perspective view of a main part of the flat display device shown in FIG. 4;

FIG. 6 is a diagram showing an example of an arrangement of electrodes of the flat panel display device shown in FIG. 5;

FIG. 7 is a drive circuit diagram of the flat panel display device shown in FIG.

FIG. 8 is a diagram showing driving waveforms of a cathode voltage and a data voltage.

FIG. 9 is a schematic sectional view of a main part of a flat panel display according to a conventional example.

FIG. 10 is a graph showing the transmission intensity of the flat panel display device shown in FIG. 9 with respect to an applied voltage.

[Explanation of symbols]

 5 Row electrode layer 7 Liquid crystal layer 60, 100 Flat panel display 62 First transparent substrate 64 Second transparent substrate 66 First transparent electrode layer 68 First inorganic film 70 Color filter layer 72 First Alignment film 74 Second transparent electrode layer 76 Second inorganic film 78 Second alignment film 80 Liquid crystal layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1333 G02F 1/1335

Claims (2)

(57) [Claims] To claim 1 wherein one surface side of the liquid crystal layer, a first organic film layer comprising a first orientation film and the color filter layer, Yes and the first transparent electrode layer is disposed, the other surface side of the liquid crystal layer in, the second chromatic including a second alignment film
A machine layer, tare arranged second transparent electrode layer is, between the first transparent electrode layer and the first organic film layer, Oyo
And between the second organic film layer and the second transparent electrode layer.
Is the polarity of the voltage applied between the first and second transparent electrode layers.
1st and 2nd for eliminating internal offset voltage due to
2 of the inorganic film is placed a liquid crystal display device Ru tare. To wherein one surface of the liquid crystal layer, and the organic layer including the first alignment layer and the color filter layer, transparency electrode layer
An electro-optical display cell a is arranged on the other surface side of the liquid crystal layer, a second alignment layer, the second distribution
It is arranged through the dielectric sheet laminated on the surface of the alignment film
Plasma discharge of the ionizable gas to be sealed,
Driving for image display in cooperation with the electro-optical display cell
It has a plasma cell defining a pixel, the transparent electrode between the organic film layer and the transparent electrode layer
Internal due to the polarity of the applied voltage between the layer and the plasma cell
A plasma-addressed liquid crystal display device in which an inorganic film for eliminating an offset voltage is disposed.