JPH03181917A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make liquid crystal display without troubles even if a temp. compensating circuit is not incorporated by using a MIM element formed by using an insulating film consisting of a hard carbon film as an active element. CONSTITUTION:The insulating film of the active (MIM) element 5 consists of the hard carbon film (also called as an i-c film, diamond-like carbon film, amorphous diamond film or diamond thin film) contg. at least either of an amorphous material and fine crystals as the main structure forming elements of the carbon atoms and hydrogen atoms. Various conductors, such as Al, Ta, Cr, W, Mo, Pt, Ni, and transparent conductors, are used as the material of the 1st conductor 7 to constitute a lower electrode. While various conductors, such as Al, Cr, Ni, Mo, Pt, Ag, and transparent conductors, are used as the material of a 2nd conductor 6, the Ni, Pt, Ag ate more preferable. The need for providing a temp. compensation circuit for a driving circuit system is elimi nated even if an atmosphere temp. is changed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal display device, and more specifically, an active matrix type liquid crystal display device using an MIA (conductor-M film-conductor) element as an active element. Regarding.

[Conventional technology]

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 demand for large-area LCD panels for office automation equipment, LCD TVs, etc. This active matrix method employs a method of providing an active element for each pixel.

Incidentally, an active element is often used as one of the active elements. This is because it exhibits nonlinear current-voltage characteristics that are good for switching. As an IM element, conventionally, a metal electrode such as Ta, i, Ti, etc. is provided as a lower electrode on an insulating substrate such as a glass plate, and an oxide of the metal or a metal electrode made of 5in)(, 5iNz, etc.) is placed on top of the lower electrode. An insulating film is provided, and AQ and Cr are provided as upper electrodes on top of the insulating film.
There are known devices equipped with metal electrodes such as the following.

However, a device using a metal oxide as an insulator (insulating film) (Japanese Patent Application Laid-Open Nos. 57-196589 and 61-2326)
No. 89, No. 62-62333, etc.), the #4AS film is formed by anodic oxidation or thermal oxidation of the lower electrode, so the process is complicated and requires high-temperature heat treatment. In addition, the film controllability (uniformity and reproducibility of film quality and thickness) is poor, and the substrate is limited to heat-resistant materials. Also, since the insulating film is made of a metal oxide with constant physical properties, it is not possible to freely change the material of the device or the device characteristics, and there is a drawback that the degree of freedom in design is narrow. This means that it is extremely difficult to design and manufacture a device that fully satisfies the specifications of a liquid crystal display device incorporating an MIM element. Furthermore, as will be described later, there is a relationship between the relative dielectric constant Er and the steepness β of the element as βce l / i1, and when εr is high, the steepness becomes small, making it unsuitable for high-density display. It has the following disadvantages.

In addition, in the case of an MIM element using 5iOz or 5iNz for the insulating film (Japanese Unexamined Patent Publication No. 61-275819), the insulating film is formed by a vapor phase method such as plasma CVD or sputtering, but the substrate temperature is Since a temperature of about 300° C. is required, low-cost substrates cannot be used, and when the area is increased, film thickness and film quality tend to become non-uniform due to substrate temperature distribution. Furthermore, since these insulating films are synthesized in a gas phase, a large amount of dust is generated and the film has many pinholes, which reduces the yield of devices. Furthermore,
The film stress is large and film peeling occurs, which also reduces the yield of the device.

On the other hand, liquid crystal materials generally have temperature characteristics of threshold voltage.
In addition, due to the temperature dependence of conventional active elements,
Liquid crystal display devices require a temperature compensation circuit. and,
This temperature compensation circuit is usually designed to form part of the drive circuit system.

For example, a liquid crystal display device (L
CD), the temperature compensation coefficient is a reasonably large value of 120 Illv/℃ [Japan Society for the Promotion of Science 142nd Committee on Organic Materials for Information Science Subcommittee A (Liquid Crystal Subcommittee) 37th Research Meeting Materials (
62,6,11)). As one specific example, a liquid crystal display device using a temperature compensation sensor was published in Japanese Patent Application Laid-Open No. 58-176.
It is also described in Publication No. 622.

However, incorporating a temperature compensation circuit into a part of the drive circuit system complicates the device itself and inevitably increases costs.

[Problem to be solved by the invention]

The present invention provides a liquid crystal display device in which the insulating film in the HIM element is changed from the above-mentioned metal oxide, 5iOz, 5iN1, etc. to a specific film that can be formed at a low temperature, and at the same time does not incorporate a temperature compensation circuit. It is something to do.

[Means to solve the problem]

In the present invention, a liquid crystal material is sandwiched between a pair of transparent substrates, and at least one conductor-insulating film is provided on each of a plurality of pixel electrodes disposed on at least one of the substrates.
An active element consisting of a conductor is connected to an active element.
The matrix type liquid crystal display device is characterized in that the insulating film is a hard carbon film, the power is 1, and the drive circuit system has a temperature compensation circuit.

The inventors of the present invention have previously conducted a number of research studies on liquid crystal display devices, and found that using HIM elements whose insulating film is a hard carbon film as an active element, such MIM
Regardless of whether the device is formed, we have dared to confirm that liquid crystal display can be performed without any inconvenience without incorporating a temperature compensation circuit. The present invention has been made based on this.

In the following, the invention will be explained in more detail with reference to the accompanying drawings.

As described above, the liquid crystal display device of the present invention has an active element (M
The insulating film of the IM element is formed of a hard carbon film that can be formed at a deposition temperature of about room temperature, and the drive circuit system including the active element is constructed without a temperature compensation circuit.

That is, the liquid crystal display device of the present invention, compared to the conventional one,
By using active elements with low temperature dependence (conductor-insulator-conductor (MIM) elements using a hard carbon film as the insulation film), display characteristics can be maintained without the need for a compensation circuit even when temperature changes occur. It was designed to be maintained.

The insulating film in the MIM element of the present invention is a hard carbon film (i-C film, diamond-like carbon film, amorphous (also called diamond film or diamond thin film).

One of the features of the hard carbon film is that it is a vapor-phase grown film.
As will be described later, the various physical properties can be controlled over a wide range by controlling the film forming conditions. Therefore, even though it is an insulating film, its resistance value covers the range from semi-insulator to MA edge region, and in this sense, the MIM element used in the present invention is
The MST element (Metal-5emj, -Insul
, ator), and SIS elements (an element consisting of a semiconductor-insulator-semiconductor, where the semiconductor is doped with impurities at a high concentration).

Further, as the transparent substrate in the present invention, an insulating material such as a glass plate, a plastic plate, or a flexible polymer film is used.

Next, the production of an active element (an active element) and a liquid crystal display device using the same will be described with reference to FIGS. 1 and 2.

FIG. 1 shows how the four image electrodes are connected to the H element 5. First, a transparent electrode material for pixel electrodes is deposited on a transparent substrate (not shown) by a method such as vapor deposition or sputtering, and then patterned into a predetermined pattern to form a pixel shape [j4]. A conductor thin film for the lower electrode is formed by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern by wet or dry etching to form a first conductor 7 that will become the lower electrode,
A hard carbon film 2 is coated thereon by a plasma CVD method, an ion beam method, etc., and then patterned into a predetermined pattern by dry etching, wet etching, or a lift-off method using resist I to form a tIA edge film. A conductor thin film for a pass line is coated by a method such as vapor deposition or sputtering, and patterned into a predetermined pattern to form a second conductor 6 that becomes a pass line (common electrode).
Finally, unnecessary portions of the lower electrode 7 are removed to expose the transparent electrode pattern to form the pixel electrode 4. In this case, the configuration of the M element (active element) 5 is not limited to this, but it is also possible to provide a transparent electrode on the top layer after creating the MIN element. A structure that also serves as
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
They 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 100-8000 Å, preferably 200-5000 Å, more preferably 300-800 Å.
The number is in the range of 4,000 people.

By using the HIM element 5 using the hard carbon film 2, it is not only possible to improve the display quality and manufacture it at low temperatures, but also to provide a temperature compensation circuit that has previously constituted a part of the drive circuit system. The need has been eliminated. The reason for this will be clear from what will be described later.

Next, the material of the HIM element used in the present invention will be explained.

Materials for the first conductor 7, which becomes the lower electrode, include liver, Ta,
Various conductors are used, such as Cr, JNo, Pt, Ni, and transparent conductors.

The material of the second conductor 6, which becomes the pass line, is liver, Cr.
, Ni, Mo, Pt, Ag, and transparent conductors are used, but Nj, Pt, and Ag are preferred because they are particularly excellent in stability and reliability of I-■ characteristics.

The symmetry of the MIM device using the hard carbon film 2 as the insulating film does not change even if the type of electrode is changed, and the QnI ce
From the relationship sr;;(7), it can be seen that Poole-Frenkel type conduction is occurring. Further, from this fact, it can be seen that in the case of this type of MIM element, the upper electrode and the lower electrode may be combined in any manner. However, the device characteristics (IV characteristics) deteriorate and change depending on the adhesion between the hard carbon film and the electrode and the state of the interface. Considering these, Ni, Pt
, It is preferable to use Ag.

The current-voltage characteristics of the MIM element according to the present invention are shown in FIG. 2, and approximately expressed by the conduction equation shown below.

I = exp (βV1A) ・(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:
Thickness of hard carbon film: Boltzmann constant T: Ambient temperature C1: Dielectric constant ε of hard carbon film. ; Organic compound gas, especially hydrocarbon gas, is used to form the vacuum dielectric hard carbon film. The phase state of these raw materials does not necessarily have to be a gas phase at room temperature and normal pressure; they can be used in either a liquid phase or the same phase as long as they can be vaporized through melting, evaporation, sublimation, etc. by heating or reduced pressure. .

Regarding hydrocarbon gas as a raw material gas, for example, C
H4, C2H6, C,)1. , paraffinic hydrocarbons such as C4H1o, acetylenic hydrocarbons such as C, H4,
Gases containing at least all hydrocarbons such as olefinic hydrocarbons, acetinic hydrocarbons, diolefinic hydrocarbons, and even aromatic hydrocarbons can be used.

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

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 501/cm" Pressure Crab 10" to 10 Torr 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 to 1
5 (The temperature is 1°C.) Due to this plasma state, the source gas is decomposed into radicals and ions and reacts, thereby forming carbon atoms (C) on the substrate.
A hard carbon film containing at least one of amorphous (amorphous) and microcrystalline (crystal size is from several IOλ to several μm) is deposited. Table 1 shows the properties of the hard carbon film.

Table 1 IZ- Note) Measuring method; Specific resistance (ρ): Determined from knee characteristics using a coplanar cell.

Optical band gap (Egopt): Obtain the absorption coefficient (α) from the spectral characteristics, (ah v )1/2=B(h V −Egopt)
Determined from the relationship.

Amount of hydrogen in the film (CO): 290 from infrared absorption spectrum
Integrate the peak around 0a1+-' and multiply by the absorption cross section A to find it.

C) l=A・fα(v)/11・dw sp″/SP″ ratio: Infrared absorption spectrum, sp3°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.

As a result of analysis by IR absorption method and Raman spectroscopy, the hard carbon film thus formed shows that carbon atoms form SF3 hybrid orbitals and SF3 hybrid orbitals, as shown in FIGS. 3 and 4, respectively. It has become clear that the inter-bonds are mixed. The ratio of SP3 bonds to SP2 bonds is I
It can be roughly estimated by peak-separating the R spectrum.

In the IR spectrum, the spectra of many modes overlap in the range from 2800 to 3150 cm-', but the attribution of the peak corresponding to each wave number has been clarified.
Peak separation is performed using Gaussian distribution as shown in Figure 5,
If you calculate each peak area and find the ratio, SP3
/SP2 ratio can be known.

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 several tens of micrometers to several micrometers.

In the case of plasma CVD method, which is generally suitable for mass production,
The smaller the RF output, the higher the specific resistance value and hardness of the film, and the lower the pressure, the more active species are formed. A tendency for resistance and hardness to increase is observed. 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 of forming a high-quality hard carbon film even under relatively low temperature conditions of room temperature to 1.50°C, making it ideal 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, compared to Ta2O,..., A Q 203., which has been conventionally used in MIM. Since it is smaller than SiNx, when making an element with the same capacitance, the element size only needs to be larger, so it does not require much fine processing and the yield improves (because of the active conditions, LCD and MIM elements The capacity ratio of CLCD:C
HIN6- = about 10:1 is required).

Since the dielectric constant is small, the steepness becomes large.
The ratio between the on-current Ion and the off-current Ioff can be increased. Therefore, L at lower duty ratio
This enables the CD to move and open, making it possible to realize a high-density LCD.

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.

In view of the above points, by using a hard carbon film, a low-cost, gradation (color), and high-density LCD can be realized.

Furthermore, in addition to carbon atoms and hydrogen atoms, this hard carbon film contains
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 about 2 to 3 times thicker than that of non-doped ones. The occurrence of pinholes during device fabrication can be prevented, and the mechanical strength of the device can be dramatically improved. Further, 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 bonding energy between C-8 and C-x is larger for C-x.

In order to use these elements as the constituent elements of the film, in addition to hydrocarbon gas and hydrogen, the raw material gases include elements from group Ⅰ, elements from group Ⅰ, elements from group Ⅰ of the Periodic System Table, and alkali metals. element,
Compounds (or molecules) containing alkaline earth metal elements, nitrogen atoms, oxygen atoms, chalcogen elements, or halogen elements (
Hereinafter, these gases may also be referred to as "other compounds").

Examples of compounds containing Group Ⅰ elements of the periodic table include B(OC, H5)), B, H,, BCQ3, BBr,
, BF3, A flood (0-i-Ci Ht )], (coa
)a ha, (C21(,)a hQ, (i-C4H
, )3AQ, AnCQ, , Ga (0-i-Ci Hv
)a, (CH,)3Ga, (C,J), Ga, Ga a
CQ3, GaBr, (0-i-C3Ht)3,
In, (C2L)a In, etc.

Examples of compounds containing Group Ⅰ elements of the periodic table include Si.
H,,Si,H5x3H,,(C,)l,),SiH
,5IF4,Sin,C et al.,5i(OCHa)*,S
i (QC, H,) 4.5i (QC, Ht )4, G
eCQ4, GeH4, Ge(OCJW*-Ge(CzH
s)4, (CHa)4Sn, (CJs)4Sn, 5n
There are CQ4 etc.

19- Compounds containing Group I elements of the periodic table include, for example, P
H,,PF3,PF,,PCf12F,,pcparty2F,
P(,Q,,PBr3,pO(OCH3)3,P(c
z Is )3, pocu, , AsH3, AsCQ3,
AsBr3, AsF, , AsF, , AsCf1. , Sb
H3, SbF3.5bcn,, Sb (QC2H5)a
etc.

As a compound containing an alkali metal atom, for example, Li0
-i-C3H,, Na0-i-C3H7, KO-1-C
There are 3H7 etc.

Examples of compounds containing alkaline earth metal atoms include C
a(QC,H,)3. Mg(OCzHs)z, (Cz
Hs)zMg, etc.

Examples of compounds containing nitrogen atoms include nitrogen gas, inorganic compounds such as ammonia, organic compounds having functional groups such as amino 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, functional groups such as hydroxyl groups, aldehyde groups, acyl groups, ketone groups, nitro groups, nitrosone groups, sulfone groups, ether bonds, ester bonds, peptide bonds, heterocycles containing oxygen, etc. Alternatively, organic compounds having bonds, metal alkoxides, etc. may be mentioned.

Examples of compounds containing chalcogen elements include H2S
, (C13) (CH,) , s (C12) ,
CH3,C8,=CHCH25CH2CH=CH,,C
,H,SC,H,,C,H,5C)I,,thiophene,
H, Ss.

(CJs) ise, H, Te, etc.

Compounds containing halogen elements include, for example, fluorine,
Inorganic compounds such as chlorine, bromine, iodine, hydrogen fluoride, chlorine fluoride, bromine fluoride, iodine fluoride, hydrogen chloride, bromine chloride, iodine chloride, hydrogen bromide, iodine bromide, hydrogen iodide, alkyl halides , aryl halides, styrene halides, polymethylene halides.

Organic compounds such as haloform are used.

FIG. 6 is a graph showing the relationship between the threshold voltage of liquid crystal and the temperature dependence of transmittance. As can be seen from FIG. 6, as the ambient temperature increases, the threshold voltage decreases.

Therefore, a temperature compensation circuit is generally required. The temperature compensation coefficient of liquid crystal is about 3 to 201 mV/'C. The temperature compensation coefficient of the hard carbon film is 10 to 4 when 16V is applied when ON.
It was found that the value was quite small at 0111v/°C. but,
Since the signs of the coefficients are the same, it was thought that the value would be large due to addition with the temperature coefficient of the liquid crystal, but since the OFF resistance also changes with temperature changes, it cannot be evaluated simply.

From equations (2) and (3) above, it can be seen that β changes depending on the ambient temperature and trap depth. FIG. 7 shows an example of the effective voltage applied. Now, when the element characteristics are set to the actual IIA shown in FIG. 7, it can be seen from (2) and (3) above that when the temperature rises, β becomes smaller and β becomes larger. In Figure 7, it can be thought of as moving to the right. From this, it can be seen that when the temperature increases, the threshold voltage of the liquid crystal and the effective voltage applied to the liquid crystal layer decrease. As described above, the characteristics of an MIM element using a hard carbon film can be widely controlled from the characteristics of the hard carbon film, and the HIM characteristics reacted with each liquid crystal material can be utilized.

Therefore, by controlling the value of β and the temperature dependence of β, it is possible to match the temperature characteristics of the liquid crystal and the effective voltage applied to the liquid crystal layer, so that the display performance does not change even without using a temperature compensation circuit. I understand.

Actually, in order to manufacture the liquid crystal display device of the present invention, first, a transparent substrate for the common electrode 4, such as ITO5Z, is placed on the transparent substrate 1.
nO:Afl, ZnO:Si, SnO2, Ir+, 0
3rd grade from several hundred to several micrometers by sputtering, vapor deposition, etc.
The common electrode 4 is deposited to a thickness of Ill and patterned into stripes. A transparent substrate 1 provided with this common electrode 4'
and a transparent substrate 1 on which MIM elements 5 are previously provided in a matrix, and an alignment material 8 such as polyimide is applied to each surface.
A rubbing process is performed, a sealing material is attached, a gap material 9 is inserted to make the gap constant, and a liquid crystal 3 is sealed to form a liquid crystal display device (FIG. 8).

〔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. Next, ITO
was deposited to a thickness of about 800 Å using magnetron sputtering. Next, three pixel electrodes were formed by patterning.

Subsequently, an MI element using a hard carbon film as an active element was provided as follows. First, Afl was deposited on the pixel electrode of the substrate to a thickness of about 100 OA by vapor deposition, and then patterned to form a lower electrode. On top of that, a hard carbon film was deposited as an M edge film to a thickness of about 110 OA by plasma CVD, and then patterned by dry etching. Furthermore, approximately 100% of Ni was deposited on each hard carbon insulating film by vapor deposition.
After being deposited to a zero thickness, it was patterned to form an upper electrode.

I was placed on the PES substrate as the other transparent substrate (counter substrate).
TO was deposited to a thickness of about 100 OA by sputtering and patterned into stripes to form a common pixel electrode. Furthermore, a color filter was provided on the opposite surface where the common pixel electrode was provided.

A polyimide film was formed as an alignment film on both substrates, and a rubbing process was performed.

A color liquid crystal display device was fabricated by placing these substrates facing each other with each pixel electrode facing inwards, pasting them together with a gap material in between, and then filling the cells thus formed with a commercially available liquid crystal material.

At this time, the conditions for forming the hard carbon film used in the MIM element were as follows: Pressure Crab 0.03 Torr CH4 flow rate: to SCCM RF power: 0.2W/cJ Temperature: room temperature Met.

When this display device was driven while changing the ambient temperature from 0 to 60° C., no change in display performance was observed.

Example 2 A Pyrex substrate was used as a transparent substrate. Next, ITO was deposited as a pixel electrode to a thickness of about 1,000 yen by E, B, and evaporation methods, and then patterned. Next, AQ was deposited as a lower electrode to a thickness of about 1500 mm by vapor deposition, and then patterned.

Subsequently, a hard carbon film was deposited to a thickness of about 900 Å by plasma CVD, and then patterned by dry etching. Further, as an upper electrode, N1 was deposited to a thickness of about 1500 mm by E, B, and evaporation methods, and then patterned.

ITO was deposited on a Pyrex substrate as the other transparent substrate (counter substrate) to a thickness of about 100 OA by sputtering, and then patterned into stripes to form common pixel electrodes.

A polyimide film was formed as an alignment film on both substrates, and a rubbing process was performed.

A liquid crystal display device was fabricated by placing these substrates facing each other with each pixel electrode facing inward, pasting them together with a gap material in between, and then filling the cells thus formed with a commercially available liquid crystal material.

At this time, the conditions for forming the hard carbon film used in the MIM element were as follows: Pressure Crab 0.05 Torr CH4 flow rate: 205CCM RF power: 0.8W/- Temperature: 100℃ Met.

When this display device was driven while changing the ambient temperature from 0 to 60° C., no change in display performance was observed.

Example 3 On the other hand, an MIM element was provided on a Pyrex substrate as a transparent substrate in the following manner. First, Cr was deposited to a thickness of about 1000λ by sputtering, and then patterned to form a lower common electrode. After forming a hard carbon film with a thickness of 800 mm using the p-cvo method, it was patterned to form an insulating film. Furthermore, PT was vapor-deposited to a thickness of about 2000λ and patterned to form an upper electrode.

ITO was deposited to a thickness of about 500 Å on the HIM element thus formed by sputtering, and then patterned to form a pixel electrode.

A Pyrex substrate was used as the counter substrate.

ITO was deposited to a thickness of about 500 Å by sputtering, and then patterned into stripes to form a common pixel electrode.

These two substrates were bonded together via a gap material in the same manner as in Example 1, and then a commercially available liquid crystal material was encapsulated to produce a liquid crystal display device.

27 The conditions for forming the hard carbon film are as follows: Pressure Crab 0.07 Torr CH4 flow rate: 15 SCCM RF small power iw/i Temperature: 80℃ Met.

When this display device was operated with the ambient temperature varying from 0 to 60°C, no change in display performance was observed.Example 4 A PET substrate was used as the transparent substrate, and ITO was coated with E, B, and about 1000% by vapor deposition. It was deposited thickly. Next, it was patterned to form pixel electrodes.

Next, an elbow H element using a hard carbon film as an active element was provided as follows. First, i was deposited on a pixel electrode of a substrate to a thickness of about 900 Å by vapor deposition, and then patterned to form a lower electrode. Thereon, a hard carbon film was deposited as an insulating layer to a thickness of about 1300λ by plasma CVD, and then patterned by dry etching. Further, as an upper electrode, Ni was deposited to a thickness of about 1500λ by vapor deposition method 8-, and then patterned.

As the other transparent substrate, ITO was deposited as PET to a thickness of about 100 OA by E, B, and evaporation methods, and then patterned into stripes to form a common pixel electrode.

A polyimide film was formed as an alignment film on both substrates, and a rubbing process was performed. Next, these substrates were placed facing each other with each pixel electrode side facing inside, and bonded together with a gap material interposed therebetween, and a commercially available liquid crystal material was further sealed in the cells thus formed to produce a liquid crystal display device.

At this time, the conditions for forming the hard carbon film used in the HIM element were as follows: Pressure Crab 0.02Torr CH4 flow rate: 55CCM RF small power 0. ], 5s/d Temperature: room temperature Met.

When this display device was driven while changing the ambient temperature from 0 to 60° C., no change was observed in the display performance.

〔Effect of the invention〕

According to the liquid crystal display device according to the present invention, since the MIM element in which the insulating film is a hard carbon film is used, the following effects are brought about.

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) 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, driving at a low duty ratio is possible.

6) By matching the temperature characteristics of the liquid crystal material, a temperature compensation circuit can be provided in the driving circuit system even if the ambient temperature changes.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a state in which the IM element and the image electrode are continuous. FIG. 2 is a current-voltage characteristic diagram of the HIM element in the present invention. FIG. 3, FIG. 4, and FIG. 5 are diagrams for explaining the properties of the hard carbon film in the present invention. FIG. 6 is a graph showing the relationship between voltage temperature characteristics and transmittance. FIG. 7 is a graph showing the relationship between the conductivity coefficient and the effective voltage applied to the liquid crystal layer. FIG. 8 is a partially cutaway perspective view of the liquid crystal display device. 1...Transparent substrate 2...Hard carbon film 3...
-Liquid crystal 4...Pixel electrode 5...Active element (MIM element) 6...Common electrode 7...Lower electrode 8...Alignment film 9...Gap material 1-

Claims (1)

[Claims] (1) A liquid crystal material is sandwiched between a pair of transparent substrates, and each of a plurality of pixel electrodes provided on at least one substrate has at least one active element consisting of a conductor-insulating film-conductor. A connected active matrix liquid crystal display device, characterized in that the insulating film is a hard carbon film, and the drive circuit system does not include a temperature compensation circuit.