CN1188901A - Manufacture of liquid crystal display device using polarization storage film as alignment film - Google Patents

Abstract

A substrate formed with an optical polarization memory film which produces the properties to orient liquid crystal molecules in a certain direction to a polarization direction on its surface when the film absorbs polarized light is first prepd. This optical polarization memory film is then irradiated with non-polarized light from a direction diagonal with the plane of the substrate to have the light absorbed in the optical polarization memory film. Next, a liquid crystal cell is produced by arranging a pair of the substrates including the substrate subjected to the orientation treatment in such a manner in at least one thereof opposite to each other. A liquid crystal material is injected into such liquid crystal cell.

Description

Use of the manufacturing of polarization storage film as the LCD of alignment films

The application is that the full content of the document is incorporated herein by reference based on the flat 08-132039 of Japanese patent application of on May 27th, 1996 application.

The present invention relates to a kind of method that its liquid crystal molecule is directed to the LCD at pre-determined tilt angle of making.

Method for alignment as a kind of routine has used so-called rubbing method, in the method, and with cotton or the analog fixing glass substrate of liquid crystal molecule therebetween that rubs in one direction.Because be attached on this substrate at generation static or dust on the substrate, this rubbing method can cause orientation defective or display defect.

As a kind of alternative method of rubbing method, also used method for alignment with polarization storage film.Use this method for alignment, after forming polarization storage film on the substrate surface, make the liquid crystal molecule orientation in needed direction thereby polarized light is used for this polarization storage film.Can make the orientation of liquid crystal molecule identical with this polarization storage film that polarized light uses together with used polarisation of light direction.Use the method for alignment of polarization storage film to exist below.

(1) uses the silicon polyimide (Wayne M, people such as Gibbons, NATURE Vol.351 (1991) are p.49) that mixes with diazamine color.

(2) use (people such as Harfumi IIMURA with azo dyes doped P VA (polyvinyl alcohol (PVA)), 18th liuquid Crystal Panel, The Chemical Socciety of Japan, 64th AutumnAnnual Meeting, p.34, issued on September 11,1992 by a corporatejuridical person, The Chemical Society of Japan, and Jpn J.Appl.Phys.Vol.32 (1993), pp.L93-L96).

(3) use photopolymerisable photopolymer (people such as Martin Schacdt, Jpn J.Appl.Phys.Vol.31 (1992), pp.2155-2164).

(4) polarized light is applied to polyvinyl 4-methoxy cinnamic acid salt (PVC) thus film make liquid crystal molecule with the horizontal direction of this polarization direction quadrature orientation (for example, JP-A-5-326990).

(5) with polarized light along the direction with the substrate quadrature be applied to the PVC film and after this with polarized light along with the direction (azimuth direction) of this polarization direction quadrature with using polarized light to obtain pre-tilt angle (for example, JP-A-5-203184) with respect to the direction that becomes a constant angle with this substrate of quadrature.

Some Twisted Nematic LCDs contain in advance the liquid crystal molecule that tilts with respect to substrate surface.That is, be in such state: when between the liquid crystal pond, not applying voltage, by a raise end of this liquid crystal molecule of the specific angle with respect to substrate surface at each liquid crystal molecule on the substrate interface.When applying voltage between substrate, all liquid crystal molecules under the rising state begin to tilt in one direction.This state is called pre-tilt, and this angle is referred to as pre-tilt angle.

When applying voltage between substrate, the liquid crystal molecule with pre-tilt angle begins to raise from an end that is raise by this substrate.If all liquid crystal molecules have identical pre-tilt angle, they all begin to raise in identical direction so.

For the liquid crystal molecule that does not have pre-tilt angle, it is uncertain which end of each liquid crystal molecule begins to raise.If all liquid crystal molecules do not have pre-tilt angle or have less pre-tilt angle, then form two zones, an end of each liquid crystal molecule raises and raises at another its other end of zone in a zone.Edge in two zones, line defect (counter-rotating tilt discrimination line) may appear on the LCDs.

This counter-rotating tilt discrimination line is usually forming near the threshold voltage place that applies voltage especially.The position of counter-rotating tilt discrimination line changes so that uses eyes to be easy to recognize the existence of line defect with applying voltage and time.Also being attended by light scattering and low contrast causes the display quality of liquid crystal display to reduce widely.

Top method for alignment (1)-(4) can not obtain pre-tilt and relevant with the problems referred to above.

Method for alignment (5) can obtain pre-tilt angle by using twice polarized light.When for the first time using polarized light, thereby it store film and forms mild (easy) spool who is parallel to this substrate surface and is orthogonal to this polarization axis direction along the directive effect that is orthogonal to substrate in polarization.When for the second time using polarized light, it is along acting on polarization storage film with respect to substrate surface with the vergence direction of given pre-tilt angle.In this way, if use twice polarized light only to can be implemented in the orientation that required direction has the liquid crystal molecule of pre-tilt angle.

Method for alignment (5) only forms little pre-tilt angle.For example, if use the PVC film to store film and use fluorenes type mixed liquid crystal as liquid crystal material as polarization, the pre-tilt angle that obtains is about 0.1-0.3 degree.So little pre-tilt angle forms a lot of counter-rotating tilt discrimination lines immediately after applying voltage, be similar to the situation that does not provide pre-tilt angle.Although As time goes on these counter-rotating tilt discrimination lines disappear, such liquid crystal molecule can not be used for motion video and show, (about tens seconds) eliminate defect line because need the time.

Use the method for polarized light can not use nonpolarized light (natural light).Owing to use transmission to cross the polarized light of polaroid or analog, so the service efficiency of luminous energy is low and light intensity reduces half of about initial light intensity degree.The more important thing is that method for alignment (5) needs the method for two kinds of use polarized lights to cause by the working time and the labour has reduced the manufacturing turnout and manufacturing cost raises.

The purpose of this invention is to provide a kind of method of making LCD, this method can be easily and is carried out orientation process with the short time, obtains enough big pre-tilt angle simultaneously and does not use the friction process that can cause product defects.

According to one aspect of the present invention, a kind of method of making LCD is provided, comprise: preparation has the preparation process of the substrate that forms polarization storage film thereon, when this polarization storage film of absorbing polarization light time has the ability of liquid crystal molecule in a direction orientation relevant with this polarized light polarization direction that make; Nonpolarized light is stored the orientation step that absorbs this nonpolarized light in film along the directive effect that favours this substrate in this polarization storage film with at this polarization; Comprise that with making thereby the pair of substrate opposite that substrate has at least carried out orientation step places the injecting step that forms the liquid crystal pond and liquid crystal material is injected into this liquid crystal pond.

Can access this method for alignment of enough big pre-tilt angle can be only by with nonpolarized light along with respect to this substrate surface vergence direction direct action in substrate and easily the short time carries out with polarization storage film.Owing to form the pre-tilt direction not by polarized light but by nonpolarized light formation, so can improve the service efficiency of energy of light source and can reduce manufacturing cost.

When applying voltage, the rising direction of liquid crystal molecule can be by pre-tilt along a direction adjustment.Therefore can realize less than demonstration such as counter-rotating tilt discrimination line orientation.The problem that this optical orientation method does not need friction process to make can to solve static and dust to adhere to.

If the use photomask can easily apply the present invention to multizone orientation (subregion orientation) so.

Figure 1A is the side view of explanation light directional process, Figure 1B is the front elevation of substrate, Fig. 1 C is that amplification cross-sectional side view and Fig. 1 D of the polyimide polarization storage film before using unpolarized ultraviolet ray is the amplification cross-sectional side view of this film after using unpolarized ultraviolet ray.

Fig. 2 is the curve map that generation state (elimination time) characteristic of the counter-rotating tilt discrimination line that forms under various tiltangles on the liquid crystal pond of making is described.

Fig. 3 is to use photomask to form the cross-sectional view of subregion orientation.

Fig. 4 is to use photomask to form the planimetric map of optical orientation technology.

Fig. 5 is the synoptic diagram that forms the microphoto of thin pattern on substrate, and it has illustrated uses photomask to carry out the state of orientation in the liquid crystal pond of optical orientation technology.

Fig. 6 is the synoptic diagram that forms the microphoto of thin pattern on substrate, and it has illustrated uses photomask to carry out the state of orientation in another liquid crystal pond of optical orientation technology.

Fig. 7 illustrates that the twisted nematic liquid crystal pond with 4 subregions orientations (multizone) that forms by the optical orientation technology of using photomask is at the various curve maps that apply the viewing angle characteristic of transmissivity under the voltage.

With reference to the optical orientation technology of figure 1A-1D description according to the LCD manufacture method of an embodiment.Figure 1A is the schematic side view of explanation orientation system, and Figure 1B is when the front elevation when being seen by the arrow B direction among Fig. 1.In Figure 1A and 1B, X, Y and Z have shown mutually orthogonal directions.By only once using natural light or nonpolarized light, the optical orientation technology of this embodiment can obtain enough big pre-tilt angle.

Be placed on the stand 3 is to have the glass substrate 1 that forms polyimide polarization storage film 2 in its surface.Form electrode and the driver element that is generally used for LCD panel in the glass substrate 1 below polarization storage film 2.To put at the light source 4 that ultraviolet range generates light (nonpolarized light) 5 causes it nonpolarized light can be acted on the polarization storage film 2 that forms in place on substrate 1.Interference filter 10 is placed on to cause between light source 4 and the stand 3 can removes the light that does not need wavelength coverage.As shown in Figure 1A, stand 3 is at the obliquely-angled θ of X-direction with respect to the X-Y horizontal plane.Similarly, substrate 1 is with respect to the obliquely-angled θ of X-Y horizontal plane.

The transmission direction of the light of launching from light source 45 is parallel to the Z-direction with X-Y horizontal plane quadrature.Therefore, light 5 is θ with respect to the pitch angle of the normal direction L of substrate 1.In other words, ultraviolet ray 5 acts on this polarization storage film obliquely with incident angle θ.This ultraviolet ray is unpolarized ray and can be divided into the ray that contains X-direction polarized light component 51 and Y direction polarized light component 52.

Shown in Figure 1B, expand in the X-direction in the lip-deep light radiation of polarization storage film zone.The surface of supposing polarization storage film 2 is the plane and interacts with the polarized light component 51 and 52 of radiant light.Irrelevant with tiltangle, the component 52 of Y-direction polarization always is parallel to the surface of polarization storage film 2, and the total intensity of these Y-direction polarized light components exerts an influence to this interaction.On the other hand, X-direction polarized light component 51 is stored film 2 surfaces with respect to polarization angle θ becomes big and becomes big along with this tiltangle, and the component reduction coefficient in the plane of X-direction polarized light component 51 is cos θ.That is, the active strength of X-direction polarized light component reduces along with the increase at pitch angle.

When effect of light at the substrate that the X-direction shown in Figure 1A and 1B tilts the time, the effective dose maximum of the Y-direction polarized light component of use, and the effective dose of the X-direction polarized light component that uses is littler than Y-direction polarized light component.As a result, form directionality in the direction in the plane of this polarization storage film.

If this polarization storage film 2 is to have the polyimide film of side chain and tend to make liquid crystal molecule being orthogonal to the direction orientation of this polarization direction, can think that so the orientation of liquid crystal molecule causes by the minimizing of UVA side chain.Even using the remaining side chain in ultraviolet ray back to make the orientation of liquid crystal molecule in other words.Can suppose that the solubilizing reaction that ultraviolet ray has strengthened polyimide causes the exposure light quantity few more, the power of directional crystal molecule is more little.

Fig. 1 C and 1D are the cross-sectional side views of the amplification of polyimide polarization storage film 2.The polyimide polarization storage film 2 of Fig. 1 C explanation before using unpolarized ultraviolet ray, the polyimide polarization storage film 2 of Fig. 1 D explanation after using unpolarized ultraviolet ray.Being drawn as the side chain 6 that resembles jaggies in Fig. 1 C and 1D plays a part to give polyimide molecule with pre-tilt angle.As previously mentioned, along with the institute of effective dose uses up and becomes bigger, the power of the liquid crystal molecule that polyimide material is orientated in one direction reduces manyly.That is, the solubilizing reaction of side chain carries out manyly.Therefore can suppose, in Fig. 1 D with respect to the big easier dissolving of the side chain with cross symbols of about 90 degree of tilting of ultraviolet ray 5 radiation direction, and generally with this radiation direction equidirectional with the side chain of circle symbolic representation even under remarkable radiation condition, also be insoluble.As a result, most of side chain that points at radiation direction equidirectionals general and ultraviolet ray 5 is still undissolved and these side chains cause that liquid crystal molecule is oriented at vergence direction and causes the pre-tilt that can be implemented on the light radiation direction.

The orientation that uniformity is arranged with the nonrecoverable polyimide that does not have a side chain of nonpolarized light with pre-tilt.Bigger tiltangle when, need using than the polyimide that is used to have side chain.

Prepare two substrates that carried out above-mentioned optical orientation technology, perhaps another method above-mentioned substrate of preparation and a substrate that carries out conventional directional process.Two substrates of every cover have a predetermined gap toward each other therebetween, and the orientation direction of substrate is configured to vertically, so that form the liquid crystal pond of a sky.Nematic liquid crystal material is injected into this empty liquid crystal pond, on two faces in this pond, loads onto polaroid with the crossed nicols form and finish 90 degree twisted nematic liquid crystal display.

First embodiment

On substrate, form polyimide film with side chain.Can use the paint-on technique of knowing to form this film.The material of this polyimide film can be buied and not be specific a kind of from the polyimide material that those sale are used for LCD.When using polarized light, this film has the character at the direction aligned liquid-crystal molecule that is orthogonal to this polarization axle.

With as arranging this substrate, use energy density to be 500mJ/cm along the Z-direction with polyimide film at the degree of 30 as shown in Figure 1A tiltangle ²Nonpolarized light.In this case, be that the interference filter 10 of 254nm is placed on the light component of being used up wavelength outside the 210-300nm scope between ultraviolet light source and the substrate to remove with centre wavelength.

Two substrates of Xing Chenging have 90 degree twisted-oriented process relations toward each other in the above described manner, by a clearance control element being inserted betwixt so that the adjusting play is 5 μ m, thereby form empty liquid crystal pond.Can use known manufacturing technology to make the empty liquid crystal pond and (carrying out) the LCD ejection method of following.

The fluorine-containing mixed liquid crystal material that will add chiral material (S-811) by the vacuum injection is injected in the empty liquid crystal pond.After the injection, sealing injection hole and this liquid crystal pond is heated to NI (to row-isotropy) phase inversion temperature (98 ℃) or highlyer is orientated with eliminate fluid.After this, this liquid crystal pond is cooled off so that again liquid crystal molecule is adjusted to nematic phase.

Observe the display surface in the liquid crystal pond apply voltage with polarizing microscope, do not observe counter-rotating tilt discrimination line.

By the method identical with said method with various tiltangles under identical condition, promptly use near 100 seconds of ultraviolet ray the 254nm, make several liquid crystal pond.On the display surface in these liquid crystal ponds that apply voltage, the reverse generation state of tilt discrimination line of observation.The results are shown in the curve map of Fig. 2.

As what obviously find out from the curve map of Fig. 2, being up to tiltangle at all is that the 25-50 degree does not generate counter-rotating tilt discrimination line.At the 20-60 degree, generate the counter-rotating tilt discrimination line of very little (weak point), but their pop-offs in 0.5 second or the shorter time.When the little pitch angle of 10 degree, counter-rotating tilt discrimination heading line off in 3 seconds or the shorter time.With the conventional method of using polarized light for twice, even the pre-tilt angle of the identical polyimide material that is issued in top condition is 0.3 degree or littler and to make the counter-rotating tilt discrimination line required time of complete obiteration be tens seconds.Compare with this fact, the result who is shown among Fig. 2 shows that the effect of this embodiment is extraordinary.

Second embodiment

Be similar to first embodiment, on substrate, form polyimide film.At the pitch angle is to arrange this substrate with polyimide film under the 45 degree conditions.Do not use the interference filter as in the first embodiment, in nonpolarized light with all wavelengths 50 seconds of Z-direction usable range at 254-365nm.Be similar to first embodiment, two substrates that carried out above-mentioned optical orientation technology toward each other, its gap is 5 μ m and injects liquid crystal material to form the liquid crystal pond.In this embodiment, do not observe counter-rotating tilt discrimination line yet.Have the ultraviolet pitch angle of above-mentioned wide wavelength coverage and the relation between the counter-rotating tilt discrimination line generally be shown in Fig. 2 in the characteristic of curve map identical.

The 3rd embodiment

Describe another embodiment with reference to figure 3 and Fig. 4, wherein the subregion orientation by the optical orientation method is divided into many zonules with pixel.Be similar to first embodiment, forming polyimide film on the substrate 1 and this substrate is being placed on the stand of inclination.Placement one photomask 7 and photomask as shown in FIG. 3 are parallel to substrate 1 between light source and substrate 1.Fig. 4 is the planimetric map of this photomask 7.On quartz plate, form metal pattern.This metal pattern is to have only ultraviolet ray can pass through its perforate 8 fonts.

If tiltangle is too big or the optical radiation time is short when by photomask 7 ultraviolet ray 5 being acted on this substrate, can imagine that so the light of q.s becomes and is difficult to act on this substrate because on the surface of photomask 7 or interior lights be reflected or absorb.For example, when tiltangle is that 60 degree use the light time down,, the long duration can not obtain conventional orientation even making to use up.

Under different conditions, promptly tiltangle be to place substrate 1 under 45 degree and by centre wavelength be the interference filter of 254nm and by photomask 71 time was to carry out directional process under the condition in 200 seconds along the Z-directive effect in substrate with ultraviolet ray 5.Fig. 5 is the synoptic diagram of the microphotograph of the directed state of this substrate of explanation.As indicated in, liquid crystal molecule is by fully directed in the ultraviolet zone of using 8 font perforates by photomask 7.Yet, using light some zones mask shielding and action of ultraviolet radiation of no use, liquid crystal molecule is directed only very weakly.

These weak directed zones only be located at the polarization storage film 2 shown in Fig. 3 radiation areas than lower part 9 places, and in the top of these radiation areas part, left and right part is not all found them.This phenomenon can be thought because ultraviolet ray is passed 8 font perforates of photomask 7 obliquely or repeatedly reflected in polyimide film 2 and be radiated on the periphery area of polyimide film 2 radiation areas caused.

Also can be with less 35 degree substrate tiltangles, under identical condition, promptly by centre wavelength be the interference filter of 254nm and by photomask 71 time was to carry out directional process under the condition in 200 seconds along the Z-directive effect in substrate with ultraviolet ray 5.Fig. 6 is the synoptic diagram of the microphotograph of the directed state of this substrate of explanation.As indicated in, liquid crystal molecule is orientated subtly has and rectangular patterns size identical shaped with 8 font perforate radiation areas of photomask 7.

At tiltangle is under the 35 degree conditions, by the position and the radiation direction that change photomask 7 action of ultraviolet radiation is stored film 4 times in polarization.The orientation that obtains has the very fine pattern that is divided into 4 zones.The substrate that has carried out above-mentioned 4 subregion orientations is used to form twisted nematic liquid crystal pond (super multizone liquid crystal pond).Measure the viewing angle characteristic of these liquid crystal pond shadow tones.The results are shown in the curve map of Fig. 7.When passing through, preferably tiltangle is arranged on the scope that is the 25-40 degree to the maximum with photomask inclination use light.

The ordinate of Fig. 7 with (%) expression transmissivity, wherein 100% be when not applying voltage the visual angle be 0 the degree under transmissivity.Horizontal ordinate represents to be symmetrical in 0 degree from-60 spending+60 visual angles (degree) that line represents of writing music.Obtain in Fig. 7 from top to bottom curve under increasing applying voltage.The characteristic of Fig. 7 shows the fabulous viewing angle characteristic that has general mild transmissivity in wide angular field of view.

Above-mentioned embodiment uses polarization storage film to be used for being orthogonal to this polarization axis direction directional crystal molecule.By using polarization storage film to be used for to obtain identical effect being parallel to this polarization axis direction directional crystal molecule.The method of injection liquid crystal is not limited to the vacuum impregnating shooting method, but can use various other methods, for example utilizes capillarity.Can inject liquid crystal material at isotropic phase, after it cools off gradually, carry out orientation again.

As polarization storage film, can use the surface energy that does not have side chain to be about the polyimide film of 40dyn/cm.For by obtain the pre-tilt angle of uniformity with such polyimide film, preferably spend or the bigger light orientation process of carrying out by the substrate tiltangle being set to 45.Can use other film, for example light orientation PVC film.As previously mentioned, by pixel being divided into many zones with the change radiation direction with for each regional substrate pitch angle, the present invention can be used for the multizone orientation.

With reference to embodiment preferred the present invention has been described.The present invention is not limited in above-mentioned embodiment.Obviously, those skilled in the art can carry out various adjustment, improve combination etc.

Claims (12)

1. method of making LCD comprises:

Preparation has the preparation process of the polarization storage film substrate that forms thereon, when this polarization storage film of absorbing polarization light time has the ability of liquid crystal molecule in a direction orientation relevant with this polarized light polarization direction that make;

Nonpolarized light is acted on this polarization storage film and stores the orientation step that absorbs this nonpolarized light in film at this polarization along favouring this substrate; With

Comprise that the pair of substrate opposite that substrate has at least carried out orientation step places the injecting step that forms the liquid crystal pond and liquid crystal material is injected into this liquid crystal pond thereby make.

2. according to the process of claim 1 wherein that described preparation process uses by having the polarization storage film that the material that makes liquid crystal molecule directional nature on the direction of the longitudinal direction of polarization direction that is orthogonal to linearly polarized photon or elliptically polarized light constitutes.

3. according to the process of claim 1 wherein that described preparation process uses by having the polarization storage film that the material that makes liquid crystal molecule directional nature on the direction of the longitudinal direction of polarization direction that is parallel to linearly polarized photon or elliptically polarized light constitutes.

4. according to the process of claim 1 wherein that this polarization storage film is to be made of the polyimide with side chain.

5. according to the process of claim 1 wherein that the surface energy of this polarization storage film is about 40dyn/cm.

6. according to the process of claim 1 wherein that this polarization storage film is made of soluble polyvinyl cinnamate.

7. according to the process of claim 1 wherein on the polarization storage film that nonpolarized light is applied to form on this substrate with the angle that is the 10-60 degree with respect to this substrate surface normal.

8. according to the process of claim 1 wherein on the polarization storage film that nonpolarized light is applied to form on this substrate with the angle that is the 25-50 degree with respect to this substrate surface normal.

9. according to the angle that to the process of claim 1 wherein with respect to this substrate surface normal be the 25-40 degree, on the polarization storage film that nonpolarized light is applied to form on this substrate by the photomask that forms with transmittance figure.

10. according to the process of claim 1 wherein in described orientation step, twice or repeatedly nonpolarized light is used on this polarization storage film so that form and has mild different zones by the position that changes radiation direction and change nonpolarized light simultaneously.

11. according to the process of claim 1 wherein that nonpolarized light contains the light that wavelength is 254nm.

12. according to the process of claim 1 wherein that nonpolarized light contains the light that wavelength coverage is 254nm-365nm.

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