JPH04331917A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the infiltration of water, oxygen, etc., into substrates and to stabilize the display characteristics of the liquid crystal display device over a long period of time by executing the end face treatment of the substrates. CONSTITUTION:The substrate end faces of the liquid crystal display device constituted by crimping a liquid crystal between two sheets of the plastic substrates are subjected to treatments for impartation of air permeation resistance and moisture permeation resistance. The chemicals to be used for the treatments for impartation of the air permeation resistance and moisture permeation resistance are not particularly limited, insofar as these chemicals apply the air permeation resistance and moisture permeation resistance characteristics to the end faces when applied on the end faces of the plastic substrates. The air permeation resistant and moisture permeation resistant inorg. films, such as SiO2, hard carbon films, BN, AIN, and Si3N4, can be applied to the end faces by an ordinary film forming method. The impartation of the air permeation resistance and moisture permeation resistance by applying a reactive resin compsn. and photosetting resin compsn. is possible as well. Of course, the applying and calcining of an org. silicon compd. and further the plasma treatment thereof are possible as well.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a liquid crystal display device.

0002

[Prior Art] Liquid crystal display devices have a structure in which liquid crystal is sealed between substrates, but if the substrate has low air permeability and moisture permeability, bubbles may form in the display area or the resistivity of the liquid crystal itself may decrease. etc., resulting in changes in characteristics, resulting in display unevenness. A method of coating the surface of a plastic substrate with a material having high air permeability and moisture permeability in order to increase the air permeability and moisture permeability of the plastic substrate 2-68519), but this coating needs to be performed at the initial stage of the process. On the other hand, in the manufacturing process of a liquid crystal cell, a cutting process is usually used after the element is manufactured. In this case, no moisture-proofing measures have been taken on the cut end face of the board, and the surface is rougher than other faces, and the condition of this end face has a large effect on the reduction in air permeability and moisture permeability of the entire board. It turned out that it was. However, this point is not considered at all in the prior art.

0003

[Objective] In order to solve the above-mentioned problems, the present invention prevents water, oxygen, etc. from entering the inside of the substrate by applying gas permeation and moisture permeation resistance treatment to the end face of the plastic substrate.
The purpose is to improve the reliability of liquid crystal display devices.

0004

The present invention relates to a liquid crystal display device in which a liquid crystal is sandwiched between two plastic substrates, in which the end surfaces of the substrates are treated to make them resistant to air permeation and moisture permeation.

[0005] There are no particular restrictions on the chemical used for the above-mentioned gas permeation and moisture permeation resistance treatment, as long as it can be applied to the end face of the plastic substrate to impart gas permeation and moisture permeation resistance to the end face. SiO2, hard carbon film, BN, AlN, Si3N
An air-permeable, moisture-permeable inorganic film such as No. 4 can be applied to the end face by a normal film forming method. Furthermore, resistance to air permeation and moisture permeation can be achieved by applying a reactive resin composition or a photocurable resin composition. Of course, it is also possible to apply the organic silicon compound, bake it, and further perform plasma treatment if necessary. Examples of organic silicon compounds include RnSiO
Hm (m=n-4, R is an alkyl group such as methyl or ethyl) can be used. Although the film thickness is not particularly limited, it is preferably 3000 Å to 1 μm. The processing on the end face of the substrate may be performed after the step of cutting the board, or the end face processing may be performed after the liquid crystal cell is created and the driving IC is mounted. Of course, it is preferable to treat the front and back surfaces of the substrate in advance with the treatment agent of the present invention or the like.

[0006] The plastic substrate is used in the form of a film, sheet, plate, etc., and the plastic material is not particularly limited, but polyethylene terephthalate (PET), polyether sulfone (PES), polyarylate, polyimide, Polyetheretherketone (
Examples include heat-resistant plastics such as PEEK) and polyethylene naphthalate (PEN), as well as polycarbonate, polymethyl methacrylate (PMMA), and polysulfone.

[0007] The present invention does not impose any restrictions on the driving method of the liquid crystal display device (a simple matrix method or an active matrix method such as TFT or MIM may be used). The present invention does not impose any restrictions on the configuration or materials of the active elements. A metal-insulating layer-metal (MIM) element may be used as an example of an active element, and by using a hard carbon film as the insulating film, a liquid crystal display device with stable characteristics can be manufactured at low production cost. .

Next, a hard carbon film used as an edge treatment agent and as an insulating film of the MIM element in the present invention will be explained. An organic compound gas, especially a hydrocarbon gas, is used to form a 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, but can be melted, evaporated, or evaporated by heating or reduced pressure.
As long as it can be vaporized through sublimation or the like, either liquid phase or solid phase can be used. Regarding hydrocarbon gas as raw material gas, for example, CH4, C2H6, C3H8, C4H1
A gas containing at least all hydrocarbons such as paraffinic hydrocarbons such as C2H4, olefinic hydrocarbons such as C2H4, diolefinic hydrocarbons, and even aromatic hydrocarbons can be used. Furthermore, other than hydrocarbons, for example,
Alcohols, ketones, ethers, esters, C
Any compound containing at least a carbon element, such as O or CO2, can be used. The method of forming a hard carbon film from a raw material gas in the present invention is a method in which the film-forming active species is formed through a plasma state generated by a plasma method using direct current, low frequency, high frequency, microwave, etc. However, since the deposition is performed under low pressure for the purpose of increasing the area, improving uniformity, and forming a film at a low temperature, a method using a magnetic field effect is more preferable. Active species can also be formed by thermal decomposition at high temperatures. In addition, ionization vapor deposition method,
Alternatively, it may be formed through an ionic state generated by ion beam evaporation, etc., it may be formed from neutral particles generated by vacuum evaporation, sputtering, etc., or a combination thereof. It may be formed by

An example of the deposition conditions for the hard carbon film produced in this manner is as follows in the case of the plasma CVD method. RF output: 0.1 to 50 W/cm2 Pressure: 1/103 to 10 Torr Deposition temperature: Room temperature to 950°C, preferably room temperature to 300°C By this plasma state, the raw material gas is decomposed into radicals and ions and reacts. A hard carbon film containing at least one of an amorphous (non-crystalline) and a microcrystalline (crystal size is several tens of angstroms to several micrometers) consisting of carbon atoms C and hydrogen atoms H is deposited on the substrate. Further, Table 1 shows various properties of the hard carbon film.

[Table 1] Note) Measurement method; Specific resistance (ρ): I-V using a coplanar cell
Determined from characteristics. Optical bandgap (Egopt): Obtain the absorption coefficient (α) from the spectral characteristics and determine from the relationship shown in Equation 1.

[Equation 1] Amount of hydrogen in the film [C(H)]: 29 from the infrared absorption spectrum
It is determined by integrating the peak near 00/cm and multiplying it by the absorption cross section A. That is, [C(H)]=A・∫α(v)/v
・dvSP3/SP2 ratio: The infrared absorption spectrum is
3. Decompose into Gaussian functions respectively attributed to SP2,
Calculate from the area ratio. Vickers hardness (H): Based on micro Vickers meter. Refractive index (n): By ellipsometer. Defect density: Based on ESR.

[0010] As a result of analysis by Raman spectroscopy and IR absorption method, the hard carbon film thus formed shows that the carbon atoms have SP3 hybrid orbitals and SP2 hybrid orbitals, as shown in FIGS. 6 and 7, respectively.
It has become clear that there are interatomic bonds that form a hybrid orbital. The ratio of SP3 bonds to SP2 bonds can be approximately estimated by peak-separating the IR spectrum. 2800-3150/cm for IR spectrum
Although the spectra of many modes overlap and are measured,
The attribution of peaks corresponding to each wave number is clear, and if we perform peak separation using a Gaussian distribution as shown in Figure 5, calculate the area of each peak, and find the ratio, we can obtain SP.
3/SP2 can be known. Moreover, according to X-ray and electron diffraction analysis, it has been found that it is in an amorphous state (a-C:H) and/or an amorphous state containing microcrystalline grains of about 50 Å to several μm. In the case of the plasma CVD method, which is generally suitable for mass production, the lower the RF output, the higher the specific resistance and hardness of the film, and the lower the pressure, the longer the life of active species, so lowering the substrate temperature and increasing the The area can be made uniform, and the specific resistance and hardness tend 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 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 and physical properties 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 Ta2O, which is used in conventional MIM devices.
5.Since it is smaller than Al2O3 and 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 driving conditions, LCD The capacitance ratio of C(LCD)/C(MIM) = approximately 10:1 is required between C(LCD) and MIM element. Also, since the element steepness is β∝1/√ε・√d, the smaller the dielectric constant ε, the greater the steepness.
The ratio between the on-current Ion and the off-current Ioff can be increased. Therefore, LCD with lower duty ratio
This makes it possible to drive a high-density LCD. Furthermore, since the film has high hardness, there is less damage caused by the rubbing process during encapsulation of the liquid crystal material, which also improves the yield. Considering 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 elements of group III, group IV, and V of the periodic table, alkali metal elements, alkaline earth metal elements, nitrogen atoms, and oxygen elements. , a chalcogen-based element, or a halogen atom as a constituent element. If a group III element of the periodic table, a group V element, an alkali metal element, an alkaline earth metal element, nitrogen atom, or oxygen atom is introduced as one of the constituent elements, the thickness of the hard carbon film is non-doped. It can be made about 2 to 3 times thicker compared to the previous one, and this prevents pinholes from forming during device fabrication.
The mechanical strength of the element can be dramatically improved. Further, in the case of a nitrogen atom or an oxygen atom, the same effect as in the case of a group IV element of the periodic table as described below can be obtained. Similarly, devices incorporating Group IV elements of the periodic table, chalcogen elements, or halogen elements dramatically improve the stability of the hard carbon film and improve the hardness of the film, resulting in highly reliable elements. can be made. These effects can be obtained because Group IV elements and chalcogen elements reduce the active double bonds present in the hard carbon film, and in the case of halogen elements, 1) abstraction for hydrogen The reaction promotes the decomposition of the raw material gas and reduces dangling bonds in the film, and
extracts the hydrogen in the C-H bond and replaces it, C-X
It enters the membrane as a bond, increasing the bond energy (C
This is because the bond energy between -H and between C-X is larger for C-X. In order to use these elements as constituent elements of the film, in addition to hydrocarbon gas and hydrogen as raw material gases, elements from group III, group IV, and group V of the periodic table must be added as dopants to the film. elements, alkali metal elements,
In order to contain alkaline earth metal elements, nitrogen atoms, oxygen atoms, chalcogen elements, or halogen elements, compounds (or molecules) containing these elements or atoms (hereinafter these may also be referred to as "other compounds") ) gas is used. Examples of compounds containing Group III elements of the periodic table include B(OC2H5)3, B2H6, BCl3
,BBr3,BF3,Al(O-i-C3H7)3,(
CH3)3Al, (C2H5)3Al, (i-C4H9
)3Al, AlCl3, Ga(O-i-C3H7)3,
(CH3)3Ga, (C2H5)3Ga, GaCl3,
GaBr3, (O-i-C3H7)3In, (C2H5
)3In etc. Examples of compounds containing Group IV elements of the periodic table include Si2H6, (C2H5)3SiH,
SiF4, SiH2Cl2, SiCl4, Si(OCH
3) 4, Si(OC2H5)4, Si(OC3H7)4
,GeCl4,GeH4,Ge(OC2H5)4,Ge
(C2H5)4, (CH3)4Sn, (C2H5)4S
n, SnCl4, etc. Examples of compounds containing Group V elements of the periodic table include PH3, PF3, PF5, and PCl.
2F3, PCl3, PCl2F, PBr3, PO (OC
H3)3, P(C2H5)3, POCl3, AsH3,
AsCl3, AsBr3, AsF3, AsF5, AsC
l3, SbH3, SbF3, SbCl3, Sb(OC2
H5) There is a 3rd grade. Examples of compounds containing alkali metal atoms include LiO-i-C3H7, NaO-i-C3
There are H7, KO-i-C3H7, etc. Examples of compounds containing alkaline earth metal atoms include Ca(OC2H5)
3, Mg(OC2H5)2, (C2H5)2Mg, etc. Examples of compounds containing nitrogen atoms include nitrogen gas,
Examples include 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 monoxide, carbon dioxide, suboxide, nitrogen monoxide, 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,
Examples include organic compounds having functional groups or bonds such as peptide bonds and oxygen-containing heterocycles, and metal alkoxides. Examples of compounds containing chalcogen elements include H2S, (CH3)(CH2)4S(CH2)4CH
3, CH2=CHCH2SCH2CH=CH2,C2H
5SC2H5, C2H5SCH3, thiophene, H2S
e, (C2H5)2Se, H2Te, etc. Compounds containing halogen elements include, for example, fluorine, chlorine, bromine, iodine, hydrogen fluoride, carbon fluoride, chlorine fluoride, bromine fluoride,
Iodine fluoride, hydrogen chloride, bromine chloride, iodine chloride, hydrogen bromide,
Inorganic compounds such as iodine bromide and hydrogen iodide, and organic compounds such as alkyl halides, aryl halides, halogenated styrene, halogenated polymethylene, and haloform are used. A hard carbon film suitable for a liquid crystal driving MIM element is
Due to the driving conditions, the film thickness is 100 to 8000 Å and the specific resistance is 10.
Advantageously, it is in the range from 6 to 10 13 Ω·cm. In addition, considering the margin between drive voltage and withstand voltage (dielectric breakdown voltage), it is desirable that the film thickness is 200 Å or more.
In addition, in order to prevent color unevenness caused by the level difference (cell gap difference) between the pixel part and the thin film two-terminal element part from becoming a practical problem, it is desirable that the film thickness be 6000 Å or less. It is more preferable that the film thickness is 200 to 6000 Å and the specific resistance is 5×10 6 to 10 13 Ω·cm. The number of device defects due to pinholes in hard carbon films increases as the film thickness decreases, and becomes especially noticeable below 300 Å (defect rate exceeds 1%), and the uniformity of the in-plane distribution of film thickness (The accuracy of film thickness control is limited to about 30 Å,
(The variation in film thickness exceeds 10%), the film thickness is 3.
More preferably, the thickness is 00 Å or more. In addition, in order to make it difficult for the hard carbon film to peel off due to stress, and to lower the duty ratio (preferably 1/1000 or less)
It is more desirable that the film thickness is 4,000 Å or less in order to drive the semiconductor device with 4,000 Å or less. Taking these into consideration, the thickness of the hard carbon film is 300 to 4000 Å, and the specific resistivity is 107 to 1.
More preferably, it is 0.011 Ω·cm.

[0011]

EXAMPLES Examples of the present invention will be described, but the present invention is not limited thereto. Example 1 A cell was fabricated using PET as a substrate and using a method of forming a hard carbon film on the end face of the substrate as the gas permeation and moisture permeation resistance treatment according to the present invention (referred to as cell 1). The manufacturing method is shown below. ITO was deposited on substrate 1 to a thickness of 800 Å using magnetron sputtering. Next, the pixel electrode 2 was formed by patterning. Next, an MIM element using the hard carbon film 4 as an active element was provided as follows. First, Al was deposited to a thickness of 1000 Å on the pixel electrode 2 of the substrate 1 by vapor deposition, and then patterned to form the lower electrode 3. A hard carbon film 4 was deposited thereon as an insulating film to a thickness of 1100 Å by plasma CVD, and then patterned by dry etching. Furthermore, after depositing Ni to a thickness of 1000 Å on each hard carbon insulating film by vapor deposition, it is patterned to form an upper electrode 5.
was formed. Next, ITO was deposited to a thickness of 1000 Å by sputtering on the other transparent substrate (counter substrate) having the same water content, 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. Next, a polyimide film was formed as an alignment film on both substrates, and a rubbing process was performed. Here, the substrate was cut to a predetermined size, the electrode pattern and display surface on the substrate were masked, and a hard carbon film was formed on the end surface of the substrate in the same manner as described above. Next, these substrates were placed facing each other with each pixel electrode side facing inside, and were bonded together with a gap material interposed therebetween, and a commercially available liquid crystal material was further sealed in the thus formed cells to produce a color liquid crystal display device. At this time, the hard carbon film formation conditions used for the substrate end face and MIM element were as follows: Pressure: 0.03 Torr CH4 flow rate:
10 SCCM RF power: 0.2 W/cm2 Temperature: Room temperature. Example 2 During the fabrication process of a liquid crystal display device using a MIM element using a hard carbon film having the same structure as Example 1, when the substrates were cut and pasted together, the end surfaces of the substrates were cut to prevent the film from being deposited on the electrodes and display areas of the substrates. Organosilicon compound [(CH3)3S
Apply iOH and heat at 120℃ for 1 hour, then apply A
The treatment was carried out in r plasma at a temperature of 120°C and a pressure of 0.1To.
I went by rr. ] was fabricated (referred to as cell 2). Example 3 After manufacturing a liquid crystal display device using an MIM element using a hard carbon film having the same configuration as Example 1 and mounting a driving IC,
An acetone-free silicone resin was applied to the end surface of the substrate and cured at room temperature (referred to as cell 3). Comparative Example A liquid crystal display device having the same configuration as these three types of liquid crystal display devices, but using an MIM element whose substrate end face was not subjected to air permeation resistance or moisture permeation resistance treatment was fabricated (referred to as cell 4). These 4
10 different types of liquid crystal display devices at 60°C and 90%
A continuous operation test was conducted for 00 hours. As a result, as shown in FIG. 2, there was no change in display characteristics when the end face of the substrate was subjected to air permeation resistance and moisture permeation resistance treatment according to the present invention. On the other hand, in the case where the end face of the substrate was not subjected to air permeation-proofing or moisture-permeation-proofing treatment, display unevenness such as a decrease in contrast ratio occurred. The vertical axis in Figure 2 is contrast ratio, and the horizontal axis is time (unit).
It is.

0012

[Effect] The display characteristics of a liquid crystal display device can be stabilized for a long period of time by performing gas permeation and moisture permeation resistance treatment on the end face of a plastic substrate.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of an MIM element used in the LCD of the present invention.

FIG. 2 is a graph showing contrast deterioration life of a liquid crystal display device.

FIG. 3 is a spectrum diagram showing the results of an IR absorption analysis of the hard carbon film used as the insulating layer of the MIM type element of the present invention.

FIG. 4 is a spectrum diagram showing the results of Raman spectroscopy analysis of the hard carbon film used as the insulating layer of the MIM type element of the present invention.

FIG. 5 shows a Gaussian distribution of the IR spectrum.

[Explanation of symbols]

1 Board 2 Pixel electrode 3 Lower electrode 4 Hard carbon film 5 Upper electrode

Claims (3)

[Claims] 1. A liquid crystal display device comprising a liquid crystal sandwiched between two plastic substrates, characterized in that end surfaces of the substrates are treated to make them resistant to air permeation and moisture permeation. 2. The liquid crystal display device according to claim 1, wherein a hard carbon film is used as the material for performing the vapor permeation resistance and moisture permeation resistance treatment. 3. The liquid crystal display device according to claim 1, wherein an organosilicon compound is used as the material for performing the vapor permeation resistance and moisture permeation resistance treatment.