JPH03238424A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device which is high in fineness and resolution and can make large-sized display by forming this device into the structure in which liquid crystal cells with active elements are laminated in multiple layers. CONSTITUTION:This device is made into the structure in which the liquid crystal cells are laminated in at least >=2 layers. At least one of the active elements 45 are connected to each of plural pieces of picture element electrodes 44 provided on at least one substrate of the liquid crystal cells. Namely, the active element (switching element) 45 and a common electrode 46 are provided to each of the respective picture element electrodes 44 to execute active matrix driving. TFT elements formed by using a-Si, Poly-Si, etc., and MIM elements, etc., formed by using hard carbon films, etc., as insulating layers are used as the active elements 45. The liquid crystal display device which can make large- sized display and can make display with the fine fineness and high resolution is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and more particularly to a stacked liquid crystal display device formed by stacking at least two or more layers of liquid crystal cells using active elements.

[Prior Art and Problems to be Solved by the Invention] The mainstream of liquid crystal display devices is now shifting from simple matrix type panels to active matrix type panels. The reason for this is that there is a growing demand for large-area liquid crystal panels for office automation equipment, liquid crystal TVs, and the like. In this active matrix method, an active element is provided for each pixel.

By the way, active matrix type liquid crystal panels currently used in office automation equipment, liquid crystal TVs, etc. are usually equipped with a single-layer liquid crystal cell made by sandwiching a liquid crystal layer between a pair of transparent substrates. ing.

However, the display capability of this type of conventional liquid crystal panel is at most 16 gray levels, which is inferior to that of a conventional CRT.

Further, in the future, high-definition displays will be required for high-definition CAD, high-definition TVs, etc., but conventional liquid crystal panels will not be able to meet these demands.

The present invention has been made in view of the problems of the prior art, and provides a liquid crystal display device that has dramatically improved display capability, is capable of large-sized display, and can also realize high-resolution, high-quality display. The purpose is to provide.

[Means and effects for solving the problem] In order to achieve the above object, the present invention has a structure in which at least 2M or more liquid crystal cells each having a liquid crystal layer sandwiched between a pair of transparent substrates are laminated, There is provided a liquid crystal display device characterized in that at least one active element is connected to each of a plurality of pixel electrodes provided on at least one substrate of the liquid crystal cell.

Hereinafter, a liquid crystal display device of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view schematically showing a liquid crystal display device of the present invention. This liquid crystal display device has a structure in which two liquid crystal cells, namely a first cell 1 and a second cell 2, are stacked. 1st
The cell 1 and the second cell 2 each move independently, and the gradation is raised by changing the transmittance. For example, each liquid crystal cell may be manufactured separately and stacked on top of each other as shown in FIG. 2, or as shown in FIG. may be formed.

In FIG. 2, a smoothing transparent film 4 is formed on one glass substrate 3 of the first cell 1, and a common side transparent electrode 5 and an alignment film 6 are formed thereon and subjected to alignment treatment. Further, on the other glass substrate 7, a segment-side transparent electrode 8 and an alignment film 9 are formed and subjected to alignment treatment. These pair of electrode-attached substrates are arranged facing each other so that the electrode side faces inward, and are bonded together with a spacer 10 interposed around the periphery, and a liquid crystal 11 is sealed inside to form a first cell 1.

On the other hand, a common side transparent electrode 13 and an alignment film 14 are formed on one glass substrate 12 of the second cell 2, and an alignment treatment is performed. Further, on the other glass substrate 15, a segment-side transparent electrode 16 and orientation@17 are formed and subjected to an orientation treatment. These pair of electrode-attached substrates are arranged facing each other so that the electrode side faces inward, and are bonded together with a spacer 18 interposed around the periphery, and a liquid crystal 19 is sealed inside to form a second cell 2. These first cell l and second cell 2
A liquid crystal display device is constructed by stacking the above layers one above the other and disposing polarizing plates 20 and 21 on both sides thereof. Note that a color filter 22 is provided on the glass substrate 3 of the first cell 1. Although not shown, each of the plurality of pixel electrodes formed on the substrate of each liquid crystal cell is provided with at least one active element,
It is designed to perform active matrix opening.

FIG. 3 shows the upper glass substrate 7 of the first cell l in FIG.
This is an example of a structure in which the two glass substrates of the lower glass substrate 12 of the second cell 2 are one common glass substrate 30, and the other structure is the same as that in FIG.

Next, a method for manufacturing the liquid crystal display device of the present invention will be explained.
Since the manufacturing method of each liquid crystal cell is basically the same even in a multilayer panel having two or more layers, the method of manufacturing the -th layer liquid crystal cell will be mainly explained with reference to FIG. 4.

First, $1! As the edge transparent substrate 41, a glass plate, a plastic plate, a flexible plastic film, or the like is used. Then, ITO, ZnO:A(+, ZnO:Si,
A transparent electrode material such as SnO2:Sb is deposited from several hundred λ to several layers by sputtering, vapor deposition, CVD, etc.
Next, it is patterned into a predetermined pattern. At this time, if the substrate is a simple matrix substrate, transparent electrodes are patterned into stripes to obtain a liquid crystal display substrate. Active·
To use it as a matrix substrate, after patterning the transparent electrode, an active element (switching element) 45 and a common electrode 46 are provided for each pixel electrode 44. As the active element 45, a TPT element using a-5i, Poly-5i, etc., a hard carbon film, SiNx, SiC, T as a #@edge layer.
a2O,, AM20. ME elements, ASI elements, PIN diodes, back-to-back diodes, varistors, etc. are used. The wiring of the common electrode 46 is made of the previously used transparent electrode material, AQ, N1. Cr, Ni-C
Using a highly conductive material such as r, Mo, Ta, Ti, Au, Ag, or Pt, a thickness of several hundred to several micrometers is deposited by a method such as sputtering, vapor deposition, or CVD, and then patterned. In this way, an active matrix substrate is obtained.

A transparent substrate 41 made in the same manner was used as the opposite substrate to these substrates, and an alignment material 48 such as polyimide was applied to the surface and rubbed, a sealing material (not shown) was applied, and a gap material was applied. 49 to make the cell gap constant, and finally liquid crystal 43 is sealed to form a liquid crystal cell. Although not shown in FIG. 4, the smoothing transparent film 4 and color filter 22 shown in FIGS. 2 and 3 can be formed by a conventional method.

The liquid crystal display device of the present invention is obtained by stacking a plurality of liquid crystal cells produced by the method described above, but the stacking method is, for example, by bonding the liquid crystal cells together as shown in FIG. Alternatively, as shown in FIG. 3, one of the transparent substrates of both cells may be used in common, and liquid crystal cells may be formed on both sides thereof. If a plastic substrate is used as the common substrate, it is possible to further reduce the thickness and weight. Further, the liquid crystal display device of the present invention is applicable to both black and white display and color display.

Next, the fabrication of an MIM element preferably used as an active element in the present invention will be described with reference to FIG.

FIG. 5 shows how the pixel electrode 44 is connected to the MIM element 45. First, a transparent electrode material for pixel electrodes is deposited on a transparent substrate (not shown).
It is deposited by a method such as sputtering, and patterned into a predetermined pattern to form the pixel electrode 44, and then a conductive thin film for the lower electrode is formed by a method such as vapor deposition or sputtering.
The lower electrode 47 is patterned into a predetermined pattern by wet or dry etching, and a hard carbon film 42 is coated thereon by a plasma CVD method, an ion beam method, etc., and then a predetermined pattern is formed by tri-etching, wet etching, or a lift-off method using a resist. An insulating film is formed by patterning the insulating film, and then a conductor thin film for an upper electrode and a common electrode is coated thereon by a method such as vapor deposition or sputtering, and is patterned into a predetermined pattern to form an upper electrode/common electrode 46. Finally, unnecessary portions of the lower electrode 47 are removed to expose the transparent electrode pattern, which is used as a pixel electrode. In this case, the configuration of the M element is not limited to this, but N1! '! Element making machines, those with a transparent electrode on the top layer, and those with a structure in which the transparent electrode also serves as the upper or lower electrode.

Various modifications are possible, such as forming an MIM element on the side surface of the lower electrode.

Here, the thickness of the lower electrode, upper electrode and transparent electrode is usually
These range from several hundred to several thousand people, several hundred to several thousand people, and several hundred to several thousand people, respectively. The thickness of the hard carbon film is 100 to 8000 mm, preferably 200 to 5000 mm, and more preferably 300 mm.
~4000 Å range.

By using an MIM element using a hard carbon film, display quality can be improved and manufacturing can be performed at low temperatures.

Furthermore, conventionally, when a plastic substrate is used as a constituent substrate of a liquid crystal cell, it has been extremely difficult to fabricate an active matrix device using active elements due to its heat resistance.

However, a hard carbon film can be produced at a substrate temperature of about room temperature, and can also be produced on a plastic substrate, making it a very effective means for improving image quality.

Next, materials of the MIM element preferably used in the present invention will be explained.

The materials of the lower electrode 47 include AN, Dina, Cr, and W.
.

Various conductors are used, such as Pt, Ni, and transparent conductors.

Materials for the upper electrode (common electrode) 46 include ribs, Cr,
A wide variety of conductors can be used, including Ni, Mo, Pt, Ag, and transparent conductors, but Ni, Pt, and Ag are preferred because they have particularly excellent stability and reliability in -V characteristics. M! , in the ME element using a hard carbon film as the edge film 42, the symmetry of the E-V characteristics does not change even if the type of electrode is changed;
Also, from the relationship between QnIce (Tr), it can be seen that Poole-Frenkel type conduction is occurring.This also indicates that in the case of this type of MIM element, the combination of the upper electrode and the lower electrode may be used in any way. However, the device characteristics (1-V characteristics) deteriorate and change depending on the adhesion between the hard carbon film and the electrode and the interface condition. Taking these into consideration, Ni
, Pt, and Ag are preferable.

The IV characteristics of the MIM element in the present invention are shown in Figure 6, and can be approximated by the following conduction formula (1) = Lightning current V: Applied voltage N: Conductivity coefficient β : Poole-Frenkel coefficient n: Carrier density μ: Carrier mobility q: Electron charge Φ Nidrap depth ρ: Specific resistance
d: Niboltzmann constant for the thickness of the hard carbon film T: Ambient temperature ε,: Dielectric constant ε of the hard carbon film. : An organic compound gas, especially a hydrocarbon gas, is used to form a vacuum dielectric constant hard carbon film. The phase state of these raw materials does not necessarily have to be a gas phase at normal temperature and pressure; they can be used in either a liquid or solid phase as long as they can be vaporized through melting, evaporation, sublimation, etc. by heating or reduced pressure. be.

Regarding hydrocarbon gas as a raw material gas, for example, C
Paraffinic hydrocarbons such as H4, C2H, C, Hs, C4H1゜, acetylenic hydrocarbons such as C2H4, olefinic hydrocarbons, acetinic hydrocarbons, diolefinic hydrocarbons, and even aromatic hydrocarbons. Gases containing at least hydrocarbons can be used.

Furthermore, other than hydrocarbons, compounds containing at least carbon element, such as alcohols, ketones, ethers, esters, and C05C02, can be used.

The method for forming a hard carbon film from these raw material gases is as follows:
A method in which active species are formed through a plasma state generated by a plasma method using direct current, low frequency, high frequency, microwave, etc. is preferable, but it is preferable to form a film through a plasma state in which the active species is generated by a plasma method using direct current, low frequency, high frequency, or microwave. For this purpose, a method using a magnetic field effect is more preferred since the deposition is carried out under low pressure. However, active species can also be formed by thermal decomposition at high temperatures.

In addition, a hard carbon film may be formed through an ionic state generated by an ionization vapor deposition method or an ion beam vapor deposition method, or a hard carbon film may be formed from neutral particles generated by a vacuum vapor deposition method, a sputtering method, etc. Alternatively, a combination of these may be used to form a film.

An example of the deposition conditions for the hard carbon film produced in this manner is approximately as follows in the case of plasma CVD method.

RF output crab 0.1 to 50 W/cm Pressure crab to-' to 10 c orr Deposition temperature: room temperature to 950°C (such a wide range can be adopted, but preferably room temperature to 300°C, more preferably room temperature ~1
The temperature is 50°C. ) Due to this plasma state, the raw material gas is decomposed into radicals and ions and reacts, resulting in amorphous (amorphous) and microcrystalline (crystal sizes are several) consisting of carbon atoms C and hydrogen atoms H. A hard carbon film containing at least one of lOA to several μff1) is deposited. Table 1 shows the properties of the hard carbon film.

Table E Note) Measurement method: Specific resistance (ρ): Determined from I-■ characteristics using a coplanar cell.

Optical bandgap (Egopt): Obtain the absorption coefficient (α) from the spectral characteristics and determine from the relationship (ah v)””=B(h v −Egopt).

Hydrogen content in the film (CM): 290 from infrared absorption spectrum
Integrate the peak near 0 am-1 and multiply by the absorption cross section A to find it.

cl(=A1f a (w)/vdw SP3/SP" ratio: infrared absorption spectrum, SF3°S
It is decomposed into glass functions assigned to F3 and calculated from their area ratios.

Vickers hardness (H) by 2 micro Vickers meter.

Refractive index (n): By ellipsometer.

Defect density: Based on ESR.

Analysis of the hard carbon film thus formed by IR absorption and Raman spectroscopy revealed that carbon atoms formed SP3 hybrid orbital and SP' hybrid orbital as shown in Figures 7 and 8, respectively. It has become clear that there are interatomic bonds. The ratio of SP3 bonds to SP2 bonds is I
It can be roughly estimated by peak-separating the R spectrum.

The IR spectrum includes 2800-3150a++-1
Although the spectra of many modes overlap and are measured,
The attribution of the peaks corresponding to each wave number is clear, and if we perform peak separation using a Gaussian distribution as shown in Figure 9, calculate the area of each peak, and find the ratio, we can obtain S.
You can know the P3/SP” ratio.

Further, according to X-ray and electron diffraction analysis, it has been found that it is in an amorphous state (a-C: H) or an amorphous state containing microcrystalline grains of about several tens of amps to several μm.

In the case of plasma CVD method, which is generally suitable for mass production,
The lower the RF output, the higher the resistivity and hardness of the film, and the lower the pressure, the longer the life of the active species. There is a tendency for the number to increase. Furthermore, since the plasma density decreases at low pressures, methods using magnetic field confinement effects are particularly effective in increasing resistivity.

Furthermore, this method has the characteristic that it can form a hard carbon film of good quality even under relatively low temperature conditions of about room temperature to 150° C., so it is optimal for lowering the temperature of the MIM element manufacturing process. Therefore, the degree of freedom in selecting the substrate material (insulating transparent substrate material) to be used is increased, and the substrate temperature can be easily controlled, so that a uniform film can be obtained over a large area. Furthermore, as shown in Table 1, the structure, physical properties, etc. of the hard carbon film can be controlled over a wide range, so there is an advantage that device characteristics can be designed freely.

Furthermore, the dielectric constant of the film is 2 to 6, which is smaller than that of Ta2O, AQ, O, and SiNx, which are conventionally used in MIM. Because it only needs to be large, it does not require much microfabrication and the yield improves (because of the active conditions, LC
The capacitance ratio between D and ME element is CLCD: CMH4=1
0:1 is required).

Therefore, the smaller the dielectric constant, the greater the steepness,
The ratio between the on-current Ion and the off-current Ioff can be increased. Therefore, L at lower duty ratio
CDll1 movement becomes possible, and a high-density LCD can be realized. Furthermore, since the hard carbon film has high hardness, there is little damage caused by the rubbing process during encapsulation of the liquid crystal material, which also improves yield.

Considering the above points, by using a hard carbon film,
Low cost, gradation (colorization), and high density CD can be realized.

Furthermore, this hard carbon film contains 1 in addition to carbon atoms and hydrogen atoms.
It may also contain as a constituent element an element of Group 1 of the Periodic Table, an element of Group 2 of the Periodic Table, an element of Group 2 of the Periodic Table, an alkali metal element, an alkaline earth metal element, a nitrogen atom, an oxygen element, a chalcogen element, or a halogen atom.

One of the constituent elements is an element from group Ⅰ of the periodic table, also from group V.
By introducing elements, alkali metal elements, alkaline earth metal elements, nitrogen atoms, or oxygen atoms, the thickness of the hard carbon film can be made approximately 2-3 times thicker than that of non-doped ones. This makes it possible to prevent the occurrence of pinholes during device fabrication and to dramatically improve the mechanical strength of the device. Furthermore, in the case of a nitrogen atom or an oxygen atom, the same effect as in the case of an element of group Ⅰ of the periodic table as described below can be obtained.

Similarly, devices that incorporate elements from group Ⅰ of the periodic table, chalcogen elements, or halogen elements dramatically improve the stability of the hard carbon film and also improve the hardness of the film, resulting in highly reliable elements. can be made. These effects can be obtained because Group (I) elements and chalcogen elements reduce active double bonds present in the hard carbon film. In addition, in the case of halogen elements, 1) the decomposition of the source gas is promoted by an abstraction reaction with hydrogen to reduce dangling bonds in the film, and 2) the halogen element
extracts the hydrogen in the C-H bond and replaces it, C-x
It enters the membrane as a bond and increases the bond energy (
This is because the bond energy between C-H and between C-X is larger for C-0.

In order to use these elements as constituent elements of the film, raw material gases include, in addition to hydrocarbon gas and hydrogen, elements of group Ⅰ, group Ⅰ, and group ① of the Periodontal System Table.

Alkali metal elements, alkaline earth metal elements, nitrogen atoms,
A gas of a compound (or molecule) containing an oxygen atom, a chalcogen element, or a halogen element (hereinafter, these may be referred to as "other compounds") is used.

Examples of compounds containing Group I elements of the periodic table include B(OC2H5)3, B2HG, BCQ, BBr3
,BF,,AQ(0-i-C,H7),,(CH,),
AQ, (C, 1H1), AQ, (i-C4H,), A+
2, AQCQ, , Ga (0-1-C1H7L, (CH
]), Ga, (C2H9)]Ga, GaCQ, , Ga
Br,, (0-i-CiH7)], In, (C2H,
)]In etc.

Examples of compounds containing Group Ⅰ elements of the periodic table include Si.
H4,5i2H,,Si,)I9,(C2)1. ,),
SiH, SiF.

5it(2CQ2, Si(OCH3)4.51(oc2
H5)4, Si (QC,)17)4.

GeCQ4, GeH4, Ge(OC2H3), Ge
(C2H,)4, (CH,)4Sn, (C2H5)4S
n, 5nCQ4, etc.

As a compound containing an element of group Ⅰ of the periodic table, for example, P
H3,PF,,PF,,PCQ2F,,PcQ2F,
PCQ,,PBr,,PO(OCH,),,P(C2H
G) 3, POCQ, AsH3, AsCQ3, AsBr
,,AsF,,AsF9,AsCQ,,SbH,,S
bF, 5bcQ3, Sb(QC2Hs)y, etc.

As a compound containing an alkali metal atom, for example, Li0
-i-C,H7,Na0-i-C,)I,,KO-i-
There are C, H□, etc.

Examples of compounds containing alkaline earth metal atoms include C
a (QC21(S )!,'g(OCz)Is)3,
(CzHs)zMg, etc.

Examples of compounds containing nitrogen atoms include nitrogen gas, inorganic compounds such as ammonia, organic compounds having functional groups such as amine groups and cyano groups, and nitrogen-containing heterocycles.

Examples of compounds containing oxygen atoms include oxygen gas, ozone, water (steam), hydrogen peroxide, -carbon oxide, carbon dioxide, carbon suboxide, -nitrogen oxide, nitrogen dioxide, dinitrogen trioxide, and dinitrogen pentoxide. , inorganic compounds such as nitrogen trioxide, hydroxyl groups, aldehyde groups, acyl groups, ketone groups, nitro groups, nitroso groups, sulfone groups, ether bonds, ester bonds, peptide bonds, and functional groups or bonds such as heterocycles containing oxygen. Further, examples thereof include organic compounds having a metal alkoxide, metal alkoxides, and the like.

Examples of compounds containing chalcogen elements include H2S
,(C)1□)(CH2)4S(CH2),CH3,C
H2=C) ICH2SCH2CH=CH2, C21(,
5C2H3,C2)! ,SCH,,thiophene,)12
Se, (C2)1. ), Se, H2Te, etc.

Compounds containing halogen elements include, for example, fluorine,
Inorganic compounds and halogenated compounds such as chlorine, bromine, iodine, hydrogen fluoride, chlorine fluoride, bromine fluoride, iodine fluoride, chlorine hydrogen, bromine chloride, iodine chloride, hydrogen bromide, iodine bromide, hydrogen iodide, etc. Organic compounds such as alkyl, halogenated aryl, halogenated styrene, halogenated polymethylene, and haloform are used.

〔Example〕

Examples will be shown next, but the present invention is not limited thereto.

Example 1 A Pyrex substrate was used as a transparent substrate, and ITO was deposited on the Pyrex substrate to a thickness of about 800λ using the Macrotron sputtering method, and then patterned to form a pixel electrode.

Subsequently, an MIM element using a hard carbon film as an active element was provided as follows.

First, about 1,000 layers are deposited on the pixel electrodes of the substrate by vapor deposition.
After depositing to a thickness of λ, patterning was performed to form a lower electrode.

A hard carbon film was deposited thereon as an insulating film to a thickness of about 900 Å by plasma CVD, and then patterned by tri-etching. Further, Ni was deposited on each hard carbon insulating film to a thickness of about 100 OA by vapor deposition, and then patterned to form an upper electrode.

Two electrode-attached substrates were manufactured using the procedure described above.

Next, a Pyrex substrate was used as an intermediate transparent substrate (common substrate), and ITO was deposited on both sides thereof to a thickness of about 100 OA by sputtering, and patterned into stripes to form a common pixel electrode.

Next, a polyimide film was formed as an alignment film on the electrode formation surfaces of the two Pyrex substrates with electrodes and the intermediate Pyrex substrate with electrodes, and a rubbing treatment was performed.

Then, with the intermediate substrate in the center, substrates with electrodes are placed on both sides of the intermediate substrate, facing each other with the electrodes facing inside, and bonded together via a gap material, and furthermore, a commercially available liquid crystal material is sealed in each cell thus formed. created a liquid crystal display device.

At this time, the conditions for forming the hard carbon film used in the MIM element are as follows.

Pressure Crab 0.03 Torr CH4 flow rate: to SCCM RF PA'7-: 0.2W/cj Temperature: room temperature Met.

Example 2 A Pyrex substrate was used as a transparent substrate, and ITO was deposited on the Pyrex substrate to a thickness of about 1000 mm as a pixel electrode.
, B. After depositing by vapor deposition method, patterning was performed. Next, about 15% of AQ was deposited as a lower electrode by vapor deposition.
After depositing it to a thickness of 0.00 mm, it was patterned.

Subsequently, a hard carbon film was deposited to a thickness of about 800 Å by plasma CVD, and then patterned by dry etching. Further, as an upper electrode, Ni was deposited to a thickness of about 1500λ by E, B, and evaporation methods, and then patterned. Two electrode-attached substrates were created using the procedure described above.

Next, using a flexible plastic film as an intermediate transparent substrate (common substrate), ITO was deposited on both sides of the plastic film to a thickness of about 1000 mm by sputtering, and then patterned into stripes to form a common pixel electrode.

Next, a polyimide film was formed as an alignment film on the two Pyrex substrates with electrodes and the plastic film intermediate substrate with electrodes, and a rubbing treatment was performed.

Then, the plastic film intermediate substrate with electrodes is placed in the center, and the Pyrex substrates with electrodes are placed on both sides of the intermediate substrate with the electrodes facing each other with the electrodes facing inward, and bonded together with a gap material interposed therebetween.
Furthermore, a liquid crystal display device was manufactured by sealing a commercially available liquid crystal material into each cell thus formed. At this time, a color filter was installed on one of the Pyrex substrates to create a color display.

In the above, the conditions for forming the hard carbon film used in the MIM element were as follows: pressure: 0.02 Torr CH4 flow rate: 20 SCCM RF pressure: 0.8 W/ (temperature: 100°C).

Example 3 A Pyrex substrate was used as one of the transparent substrates, and an IM element was provided on the Pyrex substrate in the following manner.

First, Cr was deposited to a thickness of about 1000 mm by sputtering, and then patterned to form a lower common electrode. Next, an insulating film was formed by forming an 800λ thick 5iN film using SiH and NH3 using the P-CVD method, and then patterning it.Furthermore, Cr was deposited to a thickness of about 200OA, and then patterned. This was used as the upper electrode.

ITO was deposited to a thickness of about 500 Å on the MIM element thus formed by sputtering, and then patterned to form a pixel electrode. Two electrode-attached substrates were manufactured using the procedure described above.

Next, a Pyrex substrate was used as an intermediate transparent substrate (common substrate), and ITO was deposited on both sides of the substrate to a thickness of about 500 Å by sputtering, and then patterned into stripes to form a common pixel electrode.

Then, with the intermediate substrate in the center, substrates with electrodes are placed on both sides of the intermediate substrate, facing each other with each electrode side facing inside.

After bonding with a gap material in between, a commercially available liquid crystal was sealed in each cell to produce a liquid crystal display device.

Example 4 TP as an active element on a quartz substrate as one transparent substrate
A T was formed. The method for forming it is as follows.

First, a poly-5i active layer is deposited on a substrate to a thickness of 1000 μm at a substrate temperature of 850° C. by low-pressure CVDm, a gate insulating film made of SiO□ with a thickness of 300 OA is formed on it, and a poly A gate electrode made of -5i was formed, and a source/train electrode was further deposited on top of the gate electrode to a thickness of 300 OA. The interlayer insulating film was formed of a 5in2 film with a thickness of 8000 A. pol
Impurity diffusion into the y-5L active layer was performed using a coating type impurity diffusion material, but it is also possible to use a method such as ion implantation. After creating the TPT, ITO was deposited to a thickness of 800λ by sputtering, and then patterned to form a pixel electrode. Two electrode-attached substrates were created using the procedure described above.

Next, a plastic 71 film was used as the intermediate transparent substrate, and 800 A was applied to each side of the plastic film.
A thick ITO common pixel electrode was formed.

Then, a liquid crystal display device was manufactured by placing the intermediate plastic film substrate with electrodes in the center, pasting quartz substrates with electrodes on both sides of the intermediate plastic film substrate through gap materials, and then filling each cell with a commercially available liquid crystal.

Example 5 Ta was deposited as a lower electrode on a glass substrate to a thickness of 3000 nm by sputtering and patterned. Next, this Ta film was anodized to obtain a Ta2 film with a thickness of 600 mm.
O, a film was formed. Furthermore, Cr was deposited as an upper electrode to a thickness of 1000 nm by sputtering and patterned. ITO was deposited on this as a pixel electrode by sputtering and patterned. A liquid crystal display device was manufactured in the same manner as in Example 1 using the two glass substrates with electrodes thus obtained and the intermediate substrate obtained in the same manner as in Example 1.

Since each of the liquid crystal display devices obtained above had a multilayer structure, display with high gradation was possible. Furthermore, in an example using an intermediate substrate, in addition to the above advantages, pixel misalignment can be prevented and the cell thickness can be reduced.

〔Effect of the invention〕

According to the present invention, by forming a structure in which liquid crystal cells with active elements are laminated in multiple layers, higher definition (25
This makes it possible to provide a liquid crystal display device that has a high resolution (approximately 6 gradations) and is thin and lightweight.

Furthermore, when the active element is formed of an MIM element using a hard carbon film, in addition to the above-mentioned advantages, there are the following effects.

1) Since it is produced by a vapor phase synthesis method such as plasma CVD, the physical properties can be controlled over a wide range by changing the film forming conditions, and therefore there is a large degree of freedom in device design.

2) Since it is hard and can be made into a thick film, it is less susceptible to mechanical damage, and it is also expected that pinholes will be reduced by making the film thicker.

3) Since a high-quality film can be formed even at low temperatures near room temperature, there are no restrictions on the substrate material.

4) Since it has excellent uniformity in thickness and film quality, it is suitable for thin film devices.

5) Since the dielectric constant is low, advanced microfabrication technology is not required, and therefore it is advantageous for increasing the area of the device.Furthermore, the low dielectric constant allows the device to have a high steepness, resulting in I on/I off.
Since the ratio can be maintained, active operation at a low duty ratio is possible.

become.

Furthermore, when the active element is formed of an MIM element using a hard carbon film, in addition to the above-mentioned advantages, there are the following effects.

1) Since it is produced by a vapor phase synthesis method such as plasma CVD, the physical properties can be controlled over a wide range by changing the film forming conditions, and therefore there is a large degree of freedom in device design.

2) Since it is hard and can be made into a thick film, it is less susceptible to mechanical damage, and a thicker film can also be expected to reduce pinholes.

3) Since a high-quality film can be formed even at low temperatures near room temperature, there are no restrictions on the substrate material.

4) It has excellent uniformity in film thickness and film quality, making it suitable for thin film devices.

5) Since the dielectric constant is low, advanced microfabrication technology is not required, and therefore it is advantageous for increasing the area of the device.Furthermore, the low dielectric constant allows the device to have a high steepness, resulting in I on/I off.
Since the ratio can be maintained, active operation at a low duty ratio is possible.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a cross-sectional view schematically showing a liquid crystal display device according to the present invention, and FIGS. 2 and 3 are structural examples (two-layer structure) of the liquid crystal display device according to the present invention, respectively. FIG. 4 is a partially cutaway perspective view of a liquid crystal display device according to the present invention, FIG. 5 is a perspective view showing details of the MIM element in FIG. 4, and FIG. Graphs showing current-voltage characteristics, FIGS. 7 to 9, are diagrams for explaining the properties of the hard carbon film in the present invention. l・First cell 2...Second cell 3.7.12,
15.30・Glass substrate 5.8, 13.16・・Transparent electrode 6.9, 14.17・・Alignment film 11.19・・Liquid crystal 41・・Substrate 43・・Liquid crystal 45・・A■ A element 47 lower electrode

Claims (2)

[Claims] (1) Each of the plurality of pixel electrodes has a structure in which at least two layers of liquid crystal cells are stacked, each having a liquid crystal layer sandwiched between a pair of transparent substrates, and each of the plurality of pixel electrodes is provided on at least one substrate of the liquid crystal cell. A liquid crystal display device, characterized in that at least one active element is connected to the . (2) The liquid crystal display device according to claim 1, wherein the active element is a conductor-insulator-conductor (MIM) element, and the insulator is made of a hard carbon film.