CN101055378B - Alignment layer for liquid crystal display - Google Patents

Alignment layer for liquid crystal display Download PDF

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Publication number
CN101055378B
CN101055378B CN2007100960951A CN200710096095A CN101055378B CN 101055378 B CN101055378 B CN 101055378B CN 2007100960951 A CN2007100960951 A CN 2007100960951A CN 200710096095 A CN200710096095 A CN 200710096095A CN 101055378 B CN101055378 B CN 101055378B
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silicon oxide
layer
liquid crystal
oxide layer
lcd
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CN101055378A (en
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卢淳俊
全栢均
朴庆玉
李熙根
白弘九
金京粲
金钟福
黄昞嘏
玄东賰
安汉镇
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Industry Academic Cooperation Foundation of Yonsei University
Samsung Display Co Ltd
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Industry University Cooperation Foundation Yonsei
Samsung Electronics Co Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1337—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
    • G02F1/133734—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by obliquely evaporated films, e.g. Si or SiO2 films
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
    • H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
    • H01L21/02282—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating

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  • Nonlinear Science (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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  • Spectroscopy & Molecular Physics (AREA)
  • Optics & Photonics (AREA)
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  • Condensed Matter Physics & Semiconductors (AREA)
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Abstract

An alignment layer for an LCD includes a thin layer of silicon oxide SiOx. The silicon oxide layer horizontally aligns liquid crystals having a negative dielectric anisotropy thereon when the value of x is in the range from about 1.0 to about 1.5, but vertically aligns such liquid crystals when the value of x is in a range from about 1.5 to about 2.0. The alignment layer is readily formed on a large area of the substrate through chemical vapor deposition or evaporation deposition. Because the alignment layer is thermally and physically stable, the operational characteristics of the liquid crystal display employing this alignment layer are improved. In addition, the alignment layer has a thickness of about 500 to about 3000 angstroms thereby improving light transmittance of the LCD having the alignment layer.

Description

The oriented layer that is used for LCD
Technical field
The present invention relates to a kind of oriented layer, form the method for oriented layer and have the LCD (LCD) of oriented layer.
Background technology
LCD (LCD) is utilized according to the orientation transmission or is stopped the liquid crystal display image of light.The orientation of liquid crystal depends on oriented layer, and this oriented layer is formed among the LCD on two substrates near liquid crystal.Oriented layer allows liquid crystal according to arranging as perpendicular or parallel particular orientation in oriented layer.
By utilizing printing technology that the thin layer of polyimide-based material is applied on two substrates, and, form oriented layer with organic layer with the after-baking thin layer., organic oriented layer has relatively poor thermal stability and chemical stability.
Summary of the invention
The invention provides a kind of LCD of using the inorganic alignment layer of calorifics and chemical stabilization.In one aspect of the invention, oriented layer comprises silicon oxide sio x thin layer, and wherein the x value is greater than 1.5 and less than 2.0.Silicon oxide layer allows the liquid crystal direction vertical substantially in the silicon oxide layer upper edge to arrange.Preferably, silicon oxide layer has about refractive index of 1.0 to 1.8, and liquid crystal has approximately-1.0 to-3.9 dielectric anisotropies.
In another aspect of this invention, oriented layer comprises silicon oxide sio x thin layer, and wherein x numerical value is greater than 1.0 and less than 1.5.Silicon oxide layer allows the liquid crystal direction substantially parallel in the silicon oxide layer upper edge to arrange.
In these embodiments, silicon oxide layer has the surface of substantially flat.At length, the root mean square of the surfaceness of silicon oxide layer is equal to or less than 3nm.
Still in another aspect of this invention in, followingly provide a kind of method that forms oriented layer.Utilize process materials to form silicon oxide sio x thin layer on substrate, wherein x numerical value is greater than 1.5 and less than 2.0.Silicon oxide layer allows the liquid crystal direction vertical substantially in the silicon oxide layer upper edge to arrange.When forming silicon oxide layer, can be along the direction cvd silicon oxide that is basically perpendicular to substrate.In addition, can come cvd silicon oxide by chemical vapor deposition or vapor deposition.
Still in still another aspect of the invention in, LCD comprises two substrates, liquid crystal and oriented layer.Oriented layer comprises silicon oxide sio x thin layer, and wherein x numerical value is greater than 1.5 and less than 2.0.Liquid crystal is basically perpendicular to the direction of two substrates and arranges in the silicon oxide layer upper edge.
Description of drawings
In conjunction with the drawings with read instructions, can make aforementioned and other aspects, feature and advantage of the present invention become clear at an easy rate, wherein:
Figure 1A and 1B are for showing the sectional view according to the oriented layer of the embodiment of the invention respectively;
Fig. 2 is the curve map that shows the constituent analysis result of three sample thin layers;
Fig. 3 A, 3B and 3C are the microscopic analysis picture of three sample thin layers;
Fig. 4 is the view that is used to explain common inorganic alignment layer orientation principle;
Fig. 5 is the curve map that shows the measurement result of three sample thin layer refractive indexes;
Fig. 6 is for showing the picture of transmittance in the LCD (LCD) according to the dielectric anisotropy of liquid crystal on the same orientation layer;
Fig. 7 is the curve map that shows the orientation characteristic, and described orientation characteristic is according to the variations in refractive index of oriented layer;
Fig. 8 A and 8B are respectively and are used to explain the view of formation according to the method for the oriented layer of the embodiment of the invention; With
Fig. 9 is the sectional view of LCD according to an embodiment of the invention;
Figure 10 is the curve map that shows as the light reflectivity of LCD function of wavelength among Fig. 9;
Figure 11 be show in Fig. 9 the oriented layer of LCD have heterogeneity than the time, as the curve map of the transmittance of function of wavelength;
Figure 12 A shows when the oriented layer of LCD has different-thickness in Fig. 9, as the curve map of the transmittance of function of wavelength;
Figure 12 B shows when the oriented layer of LCD has different-thickness in Fig. 9, the curve map of the transmittance of accumulation in the corresponding wavelength of visible light scope; With
Figure 13 shows in order to allow the curve map that LCD has the transparency electrode and the mutual relationship between the oriented layer thickness of high transmission rate among Fig. 9.
Embodiment
With reference to Figure 1A and 1B, the oriented layer 2 that comprises monox (SiOx) layer is formed on the transparent insulation substrate 1.Liquid crystal 3 is arranged on the oriented layer 2.Liquid crystal 3 has oval xsect, and wherein the length of major axis is different from the length of minor axis.
Below, the orientation of liquid crystal 3 is described according to the longitudinal direction of major axis.The orientation of liquid crystal 3 depends on the silica ratio that constitutes monox.When monox was expressed as chemical formula SiOx, ratio related to by the numerical value of " 1:x " expression (hereinafter, " ratio " is identical with " x " use implication).
Shown in Figure 1A, when x had from 1.5 to 2.0 numerical value, liquid crystal 3 was vertically arranged.Shown in Figure 1B, when x had 1.0 to 1.5 numerical value, liquid crystal 3 along continuous straight runs were arranged.Like this, the orientation of liquid crystal 3 can change according to the x value, and this can be proved by following test and analysis result thereof.
Below form represent the formation condition of three sample thin layers forming under the different condition.
Form
Sample First pressing (Torr) Working pressure (Torr) Oxygen flow speed (SCCM)
S1 1.0×10 -6 7.8×10 -7 -
S2 5.2×10 -6 2.3×10 -5 -
S3 5.2×10 -6 1.0×10 -4 2
Table in the reference, three sample thin layers are by the formed silicon oxide layer of hot vapor deposition, wherein each sample has different first pressing, working pressure and oxygen flow speed in process chamber.
The first sample S1 is lower than in first pressing and working pressure under the condition of the first pressing of the second and the 3rd sample S2 and S3 and working pressure and forms.If first pressing and working pressure in the process chamber are low, the hypoxgia in the process chamber then, and then reduce the x value of monox among the first sample S1.The 3rd sample S3 forms under the condition that equates of first pressing and the second sample S2, and the oxygen of scheduled volume is injected in the process chamber.Therefore, big than among the second sample S2 of the x value among the 3rd sample S3.
Fig. 2 is the curve map that shows the constituent analysis result of three sample thin layers.Analyze type (Si-Si, Si-O, the Si-O of the key that exists in each sample by measuring bond energy 2, Si-O 3, SiO 4) and number percent.According to analysis, can access silica ratio among first, second and the 3rd sample S1, S2 and the S3.That is, among the first sample S1 x value of monox (SiOx) be 1.322, the second sample S2 be 1.658, and the 3rd sample S3's is 1.726.According to first, second treatment conditions with the 3rd sample S1, S2 and S3, these analysis results and prediction coupling.
Fig. 3 A, 3B and 3C are the microscopic analysis picture of three sample thin layers.Fig. 3 A is the picture that shows the liquid crystal structure of three sample thin layers.Two polaroids are set and insert liquid crystal and thin layer simultaneously betwixt according to the orthogonal mode of its absorption axes (arrow is indicated among Fig. 3 A).In Fig. 3 A, under the condition that absorption axes is spent with 0 respectively and 90 degree are provided with of two polaroids, obtain Image to left, and obtain Image to right under the condition with 45 degree and 135 degree settings respectively at the absorption axes of two polaroids.
With reference to Fig. 3 A, about the first sample S1, light transmission between two polaroids, and observe liquid crystal structure thus.For the second sample S2 and the 3rd sample S3, not transmission between two polaroids of light, and therefore can not observe liquid crystal structure.Be appreciated that for the first sample S1 that from these results liquid crystal can be with the phase change of light to preset range, and for the second sample S2 and the 3rd sample S3, liquid crystal can not change the phase place of light.In other words, the first sample S1 does not allow liquid crystal vertically to arrange, but the second and the 3rd sample S2 and S3 allow liquid crystal molecule vertically to arrange.
Fig. 3 B is the one group of amplification picture that shows three sample thin layer end faces, and Fig. 3 C is the one group of amplification picture that shows three sample thin layer vertical cross-section.With reference to Fig. 3 B and 3C, first, second and the 3rd sample S1, S2 and S3 have flat surfaces and not to upper process or corrugated structure., and different, wherein the surface ratio second sample S2 of the first sample S1 and the 3rd sample S3's is more smooth according to the silica ratio for the flatness of these samples.
Measure surface roughness is to carry out the quality analysis of flatness.The root mean square that measurement demonstrates the surfaceness of the first sample S1 be 1.067, the second sample S2 be 1.304, and the 3rd sample S3's is 1.348.The first sample S1, the second sample S2 and the 3rd sample S3 have smooth surface, because the root mean square of the surfaceness of sample S1, S2 and S3 is 2nm or still less.
Usually, be approximately 3nm or still less the time, the surface of thin layer is smooth when the root mean square of surfaceness.On the contrary, when the root mean square of surfaceness surpassed predetermined value, the surface of thin layer was a waveform, to the bad influence of orientation generation of liquid crystal.
Fig. 4 is the view that is used to explain the orientation principle of common orientated layer.With reference to Fig. 4, predetermined oriented layer 2 ' be formed is having waved surface, and liquid crystal 3 physically is fixed in the waved surface simultaneously along the predetermined direction oblique arrangement.Oriented layer with this waved surface allows liquid crystal to arrange along required direction.Conventional inorganic alignment layer makes liquid crystal arrange along vertical, level or vergence direction based on above-mentioned principle.
In the first sample S1, the second sample S2 and the 3rd sample S3, except that the first sample S1, only the second and the 3rd sample S2 and S3 allow liquid crystal vertically to arrange., shown in Fig. 4 B and 4C, first, second physical form with the 3rd sample S1, S2 and S3 is mutually the same.Therefore, although be different from liquid crystal among the first sample S1, the liquid crystal homeotropic alignment among the second and the 3rd sample S2 and the S3, this does not relate to the physical factor based on the thin layer surface configuration.
As mentioned above, except that the physical factor based on the thin layer surface configuration, Van der Waals for is considered chemical factor, by this power the liquid crystal among the second and the 3rd sample S2 and the S3 is vertically arranged.Between molecule spaced apart a predetermined distance, produce Van der Waals for, and the potential energy of Van der Waals for can be represented by following equation (1):
V＝(-)λ/r 6 (1)
(source: Minhua Lu, " Liquid Crystal Orientation Induced by van der WaalsInteraction (Van der Waals for interact caused liquid crystal aligning) ", Jap.J.Application.Phy.Vol.43, pp8156,2004)
When liquid crystal that is used to be separated from each other when equation (1) and oriented layer, r represents the distance between liquid crystal and the oriented layer, and as expressed in the equation (2), and multiplying each other by the polarization intensity with oriented layer and liquid crystal obtains λ.
λ∝∫α 1(ω)·α 2(ω)dω (2)
(source: identical) with equation (1)
In equation (2), α 1(ω) be the polarization intensity of oriented layer, α 2(ω) be the polarization intensity of liquid crystal, and ω is the light frequency of transmission by oriented layer and liquid crystal.
Equation (1) and (2) can be analyzed according to following.Suppose liquid crystal homeotropic alignment on oriented layer with particular physical characteristics, if frequencies omega does not cause variation, the α of equation (2) then 2(ω) can be considered to a constant.Because α 1(ω) depend on composition ratio in the oriented layer, so at α 2When (ω) having fixed value, potential energy can be according to α 1(ω) change.
In this case, shown in equation (2), work as α 1When (ω) value increased, it is big that λ becomes.In addition, shown in equation (1), when λ increased, potential energy reduced.Because material is presented on aspect the thermodynamics more stable status when potential energy reduces, if α 1(ω) have bigger numerical value, liquid crystal can be with stable manner homeotropic alignment more.
Under this supposition situation, when x value in monox (SiOx) thin layer increases, the potential energy step-down.This can be according to hereinafter inferring qualitatively.In thin layer of silicon oxide, interatomic bond is divided into two types: silicon-silicon (Si-Si) key and silicon-oxygen (Si-O) key.When the x value increased, the quantity of Si-O key was greater than the quantity of Si-Si key.This can be from above-mentioned Fig. 3 finds out in the form for the constituent analysis of first, second and the 3rd sample S1, S2 and S3.
Referring again to Fig. 2, the Si-Si key is present among the first sample S1, but is not present among the second and the 3rd sample S2 and the S3.The Si-Si key shows nonpolar, because identical atom bonding each other, and the Si-O key shows polarity, because the mutual bonding of homoatomic not, wherein oxygen has the electronegativity greater than silicon.
As mentioned above, when the x value increased, the polar bond quantity in the silicon oxide layer increased.Therefore, when applying external electrical field, indicate the polarization intensity of the ability that is polarized into positivity (+) and negativity (-) to increase.Consider equation (1) and equation (2), when polarization intensity increased, liquid crystal can be with stable manner homeotropic alignment on oriented layer more.
X value among the first sample S1 is 1.322, and it is less than 1.5.X value among the second and the 3rd sample S2 and the S3 is 1.658 and 1.726, all greater than 1.5.These results show when the x value near 1 the time, the polarization intensity in the silicon oxide layer reduces, and then has improved horizontal characteristic, and when the x value near 2 the time, the polarization intensity in the silicon oxide layer increases, and then has improved the homeotropic alignment characteristic.Therefore, according to i.e. 1.5 orientations of determining liquid crystal of the intermediate value between 1 and 2.That is to say, if the x value greater than 1.5, the liquid crystal homeotropic alignment.On the contrary, if the x value less than 1.5, then liquid crystal is horizontal.In addition, in the situation of homeotropic alignment, the x value preferably is arranged in 1.65 to 1.75 the scope so that cover x value among the second and the 3rd sample S2 and the S3.
Except that above-mentioned qualitative analysis, according to the following polarization intensity that can calculate quantitatively among first, second and the 3rd sample S1, S2 and the S3.
In particular medium, polarization intensity can be represented by following equation (3):
4 παN 3 = n 2 - 1 n 2 + 1 V - - - ( 3 )
(source: J.N.Israelachvili, " Intermolecular and Surface Forces (intermolecular force and surface force) ", Academic Press, 1991)
In equation (3), α is a dielectric polorization intensity, and N is an avogadros constant, and n is a refractive index, and V is the molar volume of medium.In order to utilize equation (3) to calculate the polarization intensity of first, second and the 3rd sample S1, S2 and S3, must measure the refractive index among first, second and the 3rd sample S1, S2 and the S3.
Fig. 5 is the curve map that shows about the measurement result of the refractive index of three sample thin layers.In Fig. 5, the x axle represents to transmit the light wavelength by medium, and the y axle is represented the refractive index based on wavelength.Fig. 6 shows the silicon dioxide (SiO of example as a comparison 2) refractive index, and the refractive index of first, second and the 3rd sample S1, S2 and S3.
With reference to Fig. 5, except that the first sample S1, refractive index reduces when wavelength increases., the first sample S1 shows the trend that is similar to the second and the 3rd sample S2 and S3 in the luminous ray scope except very short wavelength coverage (from about 380nm to 770nm).
Under the situation of identical wavelength, when the x value reduced, refractive index increased.For example, for the ruddiness with 633nm wavelength, the first sample S1 has 1.8564 refractive index, and the second sample S2 has 1.6041 refractive index, and the 3rd sample S3 has 1.5695 refractive index, and silicon dioxide has 1.4551 refractive index.
Utilize these refractive indexes and equation (3) to calculate the polarization intensity of first, second and the 3rd sample S1, S2 and S3.As a result, the first sample S1 has 1.841 polarization intensity, and the second sample S2 has 2.378 polarization intensity, and the 3rd sample S3 has 1.726 polarization intensity.Like this, when the x value in the thin layer of silicon oxide increased, polarization intensity increased.This result and above-mentioned The qualitative analysis are consistent.
In description before, suppose shared liquid crystal in first, second and the 3rd sample S1, S2 and S3, so that carry out qualitative analysis according to equation (2)., although oriented layer has extraordinary vertical orientated characteristic in LCD, liquid crystal can not be according to the physical property homeotropic alignment.
Fig. 6 is for showing the picture of transmittance in the LCD (LCD) according to the dielectric anisotropy of liquid crystal on the same orientation layer.Silicon oxide layer (x=1.726) corresponding to the 3rd sample S3 is used as oriented layer, and uses the liquid crystal with-2.0 ,-3.8 and-4.0 dielectric anisotropies (Δ ε).Two polarization plates are set and insert liquid crystal and thin layer therebetween in the orthogonal mode of the absorption axes of polarization plates.Like this, when liquid crystal is arranged perpendicular to oriented layer, black state occurs, thereby show black.As shown in Figure 6, when liquid crystal has-2.0 and during-3.8 dielectric anisotropies, liquid crystal presents black state.On the contrary, when liquid crystal has-4.0 dielectric anisotropies, light takes place leak.
Therefore, for homeotropic alignment liquid crystal, the preferred liquid crystal that has less than-4.0 dielectric anisotropy that uses.In addition, in the situation of the liquid crystal of homeotropic alignment, liquid crystal must have negative dielectric anisotropy, so that can arrange along the direction perpendicular to electric field.Thus, liquid crystal must have the dielectric anisotropy in about-4.0 to 0 scope.When dielectric anisotropy near 0 the time, the operation of LCD worsens.For this reason, the dielectric anisotropy of liquid crystal preferably has-3.9 to-1.0 scope.
Fig. 7 is the curve map that shows the orientation characteristic, and described orientation characteristic is according to the variations in refractive index of oriented layer.
In Fig. 7, the x axle is represented the refractive index of oriented layer, and the y axle is represented the variation of interfacial energy at the interface between oriented layer and the liquid crystal.By utilizing fixed value (γ 0) removing vertical interface can (γ 1) (when liquid crystal is vertically arranged) and horizontal interface energy (γ 2) difference (γ between (when the liquid crystal along continuous straight runs is arranged) 1-γ 2), the interfacial energy of standardization y axle changes (Δ γ/γ 0).From drawing the curve map that refractive index changes with respect to interfacial energy based on equation (1) and (2) result calculated, this is disclosed in the paper of Minhua Lu.
With reference to Fig. 7, interfacial energy changes refractive index in oriented layer and has negative value in less than 1.8 zone, and interfacial energy change refractive index in oriented layer have in greater than 1.8 zone on the occasion of.The former (Δ γ＜0) means that vertical interface can (γ 1) being lower than horizontal interface can (γ 2).This expression is when liquid crystal is vertically arranged, and liquid crystal is a Thermodynamically stable, make liquid crystal tend to the refractive index of oriented layer less than 1.8 regional in homeotropic alignment.On the contrary, liquid crystal tends to have in the zone of (Δ γ＞0) horizontal in the interfacial energy variation.
This analysis is consistent with first, second test result with the 3rd sample S1, S2 and S3.As shown in Figure 7, when first, second and the 3rd sample S1, S2 and S3 according to its refractive index (1.8564,1.604 and 1.569) when being plotted on the curve map, the first sample S1 is positioned at horizontal alignment zone HAR, and the second and the 3rd sample S2 and S3 are positioned at vertical orientated regional VAR.
Described in equation (3) before, the refractive index of oriented layer is relevant with the polarization intensity of oriented layer.In addition, the polarization intensity of oriented layer also with the silica that constitutes oriented layer than relevant.Therefore, the horizontal or vertical orientation characteristic of oriented layer and the silica that constitutes oriented layer are than relevant.
Below, the method for making oriented layer is described.
Fig. 8 A and 8B are used to explain the view of formation according to the method for the oriented layer of different embodiments of the invention.
With reference to Fig. 8 A, form oriented layer by chemical vapor deposition.Processing target substrate 1 is sent in the process chamber 10, and with being placed on the worktable 9.Process materials 20 is provided in the process chamber 10.Process materials 20 comprises and the reactant 21 of substrate 1 reaction and the carrier gas of carrying reactant 21.Carrier gas is flowed along the direction that is parallel to substrate 1 in process chamber 10.When carrier gas was flowed, reactant 21 moved towards the surface of substrate 1.Reactant 21 be diffused into substrate 1 the surface and with its reaction.Therefore, produce the nucleus of the material that will be deposited.And then stringer is nucleus growth simultaneously.
When forming silicon oxide layer, can use various reactants.For example, use silane (SiH 4) and oxygen (O 2) satisfy the silicon oxide layer of following formula with formation.
SiH 4+O 2→SiO 2+2H 2
Like this, when regulating silane (SiH 4) and oxygen (O 2) concentration the time, can regulate and constitute the silica ratio be formed on the oriented layer on the substrate 1.Especially, when forming vertical orientated layer, the oxygen density increase makes the silica ratio become greater than 1: 1.5.In addition, when forming the horizontal alignment layer, oxygen density reduces makes the silica ratio become less than 1: 1.5.
Chemical vapor deposition makes oriented layer vertically be deposited on the substrate and finally has flat surfaces.Usually, the surface of oriented layer is suitable for having depression and projection, and then liquid crystal is orientated along required direction.Therefore, chemical vapor deposition is difficult to the formation of oriented layer., regulating silica than to arrange along horizontal or vertical direction among the present invention of liquid crystal, although oriented layer has flat surfaces, also can the applied chemistry vapour deposition.This application of chemical vapor deposition allows to form at an easy rate large-area oriented layer and advances to be used for large-sized LCD.
With reference to Fig. 8 B, can utilize vapor deposition to form oriented layer.Processing target substrate 1 is sent in the process chamber 10, and with being placed on the worktable 9.Process materials 30 is stored in the supply source 35, and its central vertical with substrate 1 is separated.Supply source 35 is furnished with heating arrangement, and then can heat and evaporation technology material 30.Vapor deposition comprises solid state process material 30 is sublimed into gas and liquid process material 30 is flashed to gas.The process materials 31 of evaporation flows also attached thereto towards substrate 1, and is deposited on simultaneously on the substrate 1.
When forming thin layer of silicon oxide, can use various process materials 31.For example, use silicon monoxide (SiO) powder and silicon dioxide (SiO 2) powder.In this case, by regulating the working pressure in the process chamber 10 and can providing oxygen separately if desired, can regulate the silica ratio that is formed on the thin layer on the substrate 1.
Shown in Fig. 8 B, when supply source 35 just was positioned at the top, center of substrate 1, oriented layer vertically placed on the substrate, makes oriented layer have flat surfaces.Routinely, the surface of oriented layer is a waveform, so that arrange liquid crystal along required direction.Therefore, by with respect to substrate 1 supply source 35 is set centroclinally, carry out the inclination vapor deposition.The inclination vapor deposition need be controlled the pitch angle exactly., although because oriented layer has flat surfaces, owing to can arrange liquid crystal along horizontal or vertical direction by the silica ratio of regulating oriented layer, so above-mentioned inclination vapor deposition is unwanted.
For the purpose of illustration, described and utilized chemical vapor deposition or vapor deposition to form the method for oriented layer, but can use the additive method of the formation thin layer outside these methods.Below, the LCD with the oriented layer that forms by said method is described.
Fig. 9 is the sectional view of LCD according to an embodiment of the invention.
With reference to Fig. 9, provide first substrate 100 respect to one another and second substrate 200.First substrate 100 comprises pixel region, and each pixel region is restricted to the minimum unit of display image.Liquid crystal 300 is arranged between first substrate 100 and second substrate 200.In order to control the orientation of liquid crystal 300, on first substrate 100 and second substrate 200, form transparency electrode 310 and oriented layer 320.The transparency electrode 310 that is formed on first substrate 100 is used as the pixel electrode 110 that is respectively formed in each pixel region.The transparency electrode 310 that is formed on second substrate 200 is used as the public electrode 210 that covers second substrate, 200 whole surfaces.Oriented layer 320 comprises first oriented layer 120 and second oriented layer 220 that is formed on the public electrode 210 that is formed on covering pixel electrode 110 on first substrate 100.
Oriented layer 320 comprises monox (SiOx) layer.In the time of in the x value is in about scope of 1.5 to 2.0, liquid crystal 300 is basically perpendicular to first and second substrates 100 and 200 and arranges.
First and second substrates 100 and 200 are on its outer surface with first and second polarization plates 150 and 250.First and second polarization plates 150 and 250 are set makes its absorption axes vertical mutually.When liquid crystal 300 is vertical orientated, is incident on light on first polarization plates 150 along a direction polarization, and is absorbed by second polarization plates 250 subsequently.Therefore, LCD becomes black state.
LCD is respectively pixel electrode 110 and applies different voltage with public electrode 210.When applying different voltage with public electrode 210, between first and second substrates 100 and 200, vertically set up electric field and liquid crystal 300 is applied this electric field for pixel electrode 110.Liquid crystal 300 has negative dielectric anisotropy, and therefore with respect to the direction oblique arrangement perpendicular to electric field.In the state of liquid crystal 300 oblique arrangement, be incident on light on first polarization plates 150 along a direction polarization, the experience phase transition is transmitted simultaneously by liquid crystal 300, and passes second polarization plates 250.Pass the outside display image of light of second polarization plates 250.The image that the intensity of adjusting electric field will show with correspondence.When forming the electric field of maximum intensity, LCD becomes the brightest white states.
Although not shown in Fig. 9, when the x value in first and second oriented layer 120 and 220 is in about 1.0 to about 1.5 scope the time, liquid crystal 300 is horizontal.In this case, liquid crystal 300 has positive dielectric anisotropy, makes LCD become white states when not applying electric field, simultaneously LCD at liquid crystal 300 owing to become black state when electric field and homeotropic alignment.
When as described above operation LCD, the transmittance among the LCD is subjected to the thickness effect of x value and oriented layer 320.LCD according to the present invention is by having maximum transmittance according to the thickness of hereinafter described controlling x value and oriented layer 320.
Figure 10 is the curve map that shows as the light reflectivity of LCD function of wavelength among Fig. 9.
In Figure 10, curve a1 represents that LCD does not have the light reflectivity of LCD under the situation of transparency electrode 310, has the light reflectivity of LCD under the situation of transparency electrode 310 and curve a2 represents LCD.The reflectivity of the LCD that is represented by curve a1 has about 4% steady state value, and the reflectivity of the LCD that is represented by curve a2 has about 4% to about 20% scope.Therefore, the transmittance of LCD reaches 20% owing to the transparency electrode 310 as pixel electrode 110 and public electrode 210 descends.This damping capacity of transmittance is owing to transparency electrode 310 reflection institutes cause.Transparency electrode 310 comprises indium tin oxide (ITO) or indium-zinc oxide (IZO).Light reflectivity with transparency electrode 310 of ITO or IZO relies on the thickness of x value and oriented layer 320.
Figure 11 be show in Fig. 9 the oriented layer of LCD have heterogeneity than the time, as the curve map of the transmittance of function of wavelength.
Curve b0 shown in Figure 11 represents that LCD does not have the transmittance under the situation of transparency electrode 310 and oriented layer 320.Curve b1 to b7 shown in Figure 11 represents that LCD has transparency electrode 310 and contains transmittance under the situation of oriented layer 320 of heterogeneity ratio.Oriented layer 320 comprises monox (SiOx) layer, and the x value is respectively 1.13,1.27,1.46,1.65,1.70,1.83 and 1.89 according to curve b1, b2, b3, b4, b5, b6 and b7.
With reference to Figure 11, the transmittance of LCD increases according to the increase of x value usually.This result's reason is that absorption coefficient reduces with the increase of x value.For example, when the x value increased, oriented layer 320 had glass performance, had increased the transmittance of LCD thus.On the contrary, when the x value reduced, oriented layer 320 had the characteristic opposite with glass performance, and then had reduced the transmittance of LCD.
LCD uses the visible light display image.Therefore, determine that preferably the composition of oriented layer 320 is than the high transmission rate that has with permission LCD about corresponding wavelength of visible light scope.As shown in figure 11, when the x value is approximate during greater than 1.65 (b4, b5, b6, b7), LCD has about 90% the transmittance to about 770nm wavelength coverage about about 380nm of corresponding visible light.
Figure 12 A shows when the oriented layer of LCD has different-thickness in Fig. 9, as the curve map of the transmittance of function of wavelength.Figure 12 B shows when the oriented layer of LCD among Fig. 9 has different-thickness, the curve map of the transmittance of accumulation in the corresponding wavelength of visible light scope.
Curve c0 shown in Figure 12 A represents that LCD has such as the transmittance under the situation of organic oriented layer of polyimide, and described organic oriented layer has the thickness of about 100nm.Curve c1 to c5 shown in Figure 12 A represents that LCD has transparency electrode 310 and comprises transmittance under the situation of the oriented layer with different-thickness 320 of monox (SiOx).Oriented layer 320 is respectively 107nm, 120nm, 170nm, 220nm and 280nm about the thickness of curve c1, c2, c3, c4 and c5.
With reference to Figure 12 A, transmittance when using organic oriented layer approximate less than 100% and when use has the oriented layer 320 of monox greater than 100%.In the present embodiment, the transmittance shown in Figure 12 A and the 12B is a relative value about reference, and for the situation of reference, LCD has transparency electrode and do not have oriented layer 320.Shown in Figure 12 A, the transmittance the when transmittance when LCD has organic oriented layer does not have oriented layer 320 with respect to LCD reduces.Transmittance when the transmittance when LCD has the oriented layer that contains monox does not have oriented layer 320 with respect to LCD increases.The increase of transmittance depends on wavelength coverage.
With reference to Figure 12 B, the accumulation transmittance when LCD has the oriented layer 320 that contains monox increases about 7% with respect to the transmittance when LCD has organic oriented layer.Have at LCD under the situation of the oriented layer 320 that contains monox, the increase of the transmittance of accumulation depends on the thickness of oriented layer 320.LCD has maximum transmittance when the thickness of oriented layer 320 is approximately 100nm.When the thickness of oriented layer surpassed 200nm, transmittance reduced with the increase of oriented layer thickness.
If oriented layer 320 is too thin, then be difficult to the orientation of control liquid crystal 300.So oriented layer 320 need have the thickness of about 50nm at least so that control the orientation of liquid crystal 300 at an easy rate.If oriented layer 320 is too thick, then the transmittance of LCD reduces.Therefore, oriented layer 320 is restricted to the thickness that has less than about 300nm.If the thickness of oriented layer 320 surpasses 300nm, then the transmittance of LCD is less than 100%, shown in Figure 12 A and 12B.In other words, preferably, oriented layer 320 has the thickness from 50nm to about 300nm.
Figure 13 is that the correlationship that shows between transparency electrode and the oriented layer thickness has the curve map of high transmittance to allow LCD among Fig. 9.
With reference to Figure 13, allow LCD to have the thickness of transparency electrode 310 of high transmission rate and the thickness of oriented layer 320 is in inverse ratio.That is to say that when the thickness of transparency electrode 310 increased, the thickness of oriented layer 320 reduced, so that make LCD have high transmittance.
As shown in figure 13, the thickness of oriented layer 320 is in about 70nm to the scope of about 110nm, and when the thickness of oriented layer 320 during near 100nm, LCD has the transmittance of maximum, shown in Figure 12 A.Consider above-mentioned two thickness ranges, preferably, oriented layer 320 has the thickness from about 90nm to about 110nm.
As mentioned above, owing to do not consider the physical factor relevant, can make liquid crystal 300 horizontal or vertical arrangements, so utilize chemical vapor deposition can form large-area first and second oriented layer 120 and 220 at an easy rate with monox by only regulating the silica ratio.
According to the present invention, utilize thin layer of silicon oxide to form the oriented layer of LCD.Thin layer of silicon oxide has good transparency and heat/chemical/physical stability.
In addition, regulate the silica ratio in the thin layer, make that liquid crystal can horizontal or vertical substantially arrangement.When liquid crystal when predetermined direction is arranged, utilize chemical vapor deposition and need not consider physical factor outside the ratio, as the morphology of thin layer of silicon oxide, can be formed for large-sized oriented layer at an easy rate.
, yet should be appreciated that under the situation that does not break away from the spirit and scope of the present invention that those of ordinary skills are clear and can carry out various changes and modification although described exemplary embodiment of the present invention.
The present invention depends on the right of priority of korean patent application No.2006-33677 that submitted on April 13rd, 2006 and the korean patent application No.2006-129412 that submitted on Dec 18th, 2006, and its content comprises incorporated by reference at this.

Claims (21)

1. oriented layer that is used for LCD, comprise silicon oxide sio x layer, wherein the x value is greater than 1.5 and less than 2.0, and silicon oxide layer is along the liquid crystal on the vertical substantially direction arrangement silicon oxide layer, and wherein silicon oxide layer has the surfaceness that root mean square is equal to or less than 3nm.
2. oriented layer according to claim 1, wherein silicon oxide layer has the surface of substantially flat.
3. oriented layer according to claim 2, wherein the x value has from 1.65 to 1.75 scope.
4. oriented layer according to claim 1, wherein silicon oxide layer has 1.0 to 1.8 refractive index.
5. oriented layer according to claim 4, wherein liquid crystal has from-3.9 to-1.0 dielectric anisotropy.
6. oriented layer according to claim 1, wherein the x value is greater than 1.65.
7. oriented layer according to claim 1, wherein silicon oxide layer has 50 to 300nm thickness.
8. oriented layer according to claim 7, wherein silicon oxide layer has 90 to 110nm thickness.
9. method that is formed for the oriented layer of crystal liquid substrate comprises:
Form silicon oxide sio x layer on substrate, wherein x value is greater than 1.5 and less than 2.0, and silicon oxide layer is along the liquid crystal on the vertical substantially direction arrangement silicon oxide layer, and wherein silicon oxide layer has the surfaceness that root mean square is equal to or less than 3nm.
10. method according to claim 9 wherein forms silicon oxide layer and comprises along the direction cvd silicon oxide that is basically perpendicular to substrate.
11. method according to claim 9 wherein forms silicon oxide layer and comprises by chemical vapor deposition and come cvd silicon oxide.
12. method according to claim 9 wherein forms silicon oxide layer and comprises by vapor deposition and come cvd silicon oxide.
13. method according to claim 12 is wherein supplied with the process materials that is used to form silicon oxide layer from the supply source that is positioned on the dotted line that extends from substrate center along the direction that is basically perpendicular to substrate.
14. method according to claim 13, wherein process materials comprises the powder of silicon monoxide or silicon dioxide.
15. a LCD comprises:
Two substrates respect to one another;
Be arranged in two liquid crystal between the substrate; With
Be respectively formed at two liquid crystal on the substrate,
Wherein oriented layer comprises silicon oxide sio x layer, and wherein the x value is greater than 1.5 and less than 2.0, and silicon oxide layer allows liquid crystal to arrange along the direction that is basically perpendicular to two substrates, and wherein silicon oxide layer has the surfaceness that root mean square is equal to or less than 3nm.
16. LCD according to claim 15, wherein silicon oxide layer has the surface of substantially flat.
17. LCD according to claim 15, wherein silicon oxide layer has 1.0 to 1.8 refractive index.
18. LCD according to claim 17, wherein liquid crystal has from-3.9 to-1.0 dielectric anisotropy.
19. LCD according to claim 15, wherein the x value is greater than 1.65.
20. LCD according to claim 15, wherein silicon oxide layer has 50 to 300nm thickness.
21. LCD according to claim 20, wherein silicon oxide layer has 90 to 110nm thickness.
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