CA2026361A1 - Process for producing a liquid-crystal cell - Google Patents
Process for producing a liquid-crystal cellInfo
- Publication number
- CA2026361A1 CA2026361A1 CA002026361A CA2026361A CA2026361A1 CA 2026361 A1 CA2026361 A1 CA 2026361A1 CA 002026361 A CA002026361 A CA 002026361A CA 2026361 A CA2026361 A CA 2026361A CA 2026361 A1 CA2026361 A1 CA 2026361A1
- Authority
- CA
- Canada
- Prior art keywords
- rubbing
- orientation
- pretilt
- orientation layer
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- 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
- G02F1/13378—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation
- G02F1/133784—Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers by treatment of the surface, e.g. embossing, rubbing or light irradiation by rubbing
Landscapes
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Mathematical Physics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Liquid Crystal (AREA)
Abstract
ABSTRACT
Process for producing a liquid-crystal cell In a process for treating an organic orientation layer on a substrate plate for a liquid-crystal cell, the orientation layer for causing the orientation is rubbed in the conventional way in a specified direction.
Rubbing is then performed in the opposite direction, but with a weaker rubbing pressure.
It has emerged that rubbing in the opposite direction with weak pressure leads to an increase of some degrees in the pretilt angle, and this is essentially independent of the material used for the orientation layer.
Process for producing a liquid-crystal cell In a process for treating an organic orientation layer on a substrate plate for a liquid-crystal cell, the orientation layer for causing the orientation is rubbed in the conventional way in a specified direction.
Rubbing is then performed in the opposite direction, but with a weaker rubbing pressure.
It has emerged that rubbing in the opposite direction with weak pressure leads to an increase of some degrees in the pretilt angle, and this is essentially independent of the material used for the orientation layer.
Description
- 2 ~
DESCRIPTION
Process for producing a l;qu;d-crystal cell The invent;on relates to a process for producing a l;quid-crystal cell, or more prec;sely a process for treat;ng an organic orientation layer on a substrate plate for a liqu;d-crystal cell. Or;entation layers of this type serve to generate an orientat;on and a pretilt of the l;qu;d-crystal molecules. The term "orientat;on" is here taken to mean the angle between the edge of a substrate plate and the projection of a liqu;d-crystal molecule onto th;s substrate plate. The pret;lt ;s the angle by which a liqu;d-crystal molecule ;s t;lted against the plane of the substrate plate.
DESCRIPTION OF THE PR}OR ART
Orientation layers of the type ment;oned are produced with two d;fferent mater;al groups us;ng two different processes. One process utilizes inorganic mater;als wh;ch are vacuum-depos;ted slantwise onto the substrate plate ;n the direct;on of or;entation. The second process ut;lizes organ;c substances wh;chl for example, are appl;ed by spray;ng, ;mmers;on or (as a rule) by sp;ncoat;ng. The polymer films are subjected to a tempering process, and then rubbed w;th a soft mater;al (generally velvet~ aff;xed to a roller. Th;s rubbing ;s performed in the des;red direct;on of or;entation.
It is known from DE 27 22 389 A1 that for orientation and pret;lt sett;ng both processes are used jo;ntly, ;.e. both slantw;se deposit;on and rubbing. The rubbing ;s performed several t;mes ;n a spec;f;ed d;rect;on.
The direction specified will, when a steep deposition angle has been used, stand at r;ght angles to the project;on of the depos;t;on d;rection onto the substrate plate. In the case of flat deposit;on angles, rubb;n~ ;s performed parallel to the projection of the depos;t;on direction onto the substrate plate, from the side on wh;ch due to the slantw;se deposition the l;quid-crystal molecules lie deeper in the fin;shed liqu;d-crystal cell, i.e. in the d;rection of r;sing pretilt, so to speak. This process perm;ts S. Bros;g-19-3 03.10.1989 .
- 2 ~
the pretilt (which is also relatively steep with flat slantwise deposition) to be set to smaller values.
While when using slantwise-deposited ;norganic orientation layers theretend to be problems with the finished liquid-crystal cells due to excess;vely high pretilt angles, the s;tuation is rather the opposite when polymer rubbed orientation layers are used. Efforts have been made in this context to achieve higher pretilt angles by developing the materials used.
Attempts have also been made not to rub the materials, but instead to cause an or;entat;on of the polymer or;entation-layer molecules by pouring these on in the orientation direct;on or by means of other flow-applicat;on processes. It seemed desirable to avoid the rubbing, since it was known that rubbing reduces the originally attainable high pretilt angles (see in this context the findings of DE 27 22 389 A1 quoted above).
All attempts so far made to develop better materials for orientation layers and to improve production methods ~or such layers have not yet led to fully satisfactory results, i.e. to polymer orientation layers with which very high pret;lt angles can be simply and reliably achieved.
DESCRIPTION OF THE INVENTION
The process described ;n the ;nvention for treating a polymer orientation layer is distinguished by the fact that first rubbing is performed in the convent;onal way ;n one d;rect;on one or more times. Then, however, rubbing is performed in the opposite direction but with a weaker application pressure. This rubbing in the opposite direction can also be repeated several times.
It has been shown that with this process the pretilt angles of all organic orientation layers can be increased by some degrees, irrespective of the material used. The increase in pretilt by some degrees is thus achieved both with conventional polyimide orientation layers (which conventionally exhibit a pret;lt of only a few degrees) and with more recently developed materials, e.g. polyphenylene or more recent polyimides, w;th which under S. Brosig-19-3 03.10.1989 ~' - 3 - ~ ~2~
the conventional production processes pretilt angles of about 15 - 20 are ach;eved.
WAYS TO IMPLEMENT THE INVENTION
Trials have been performed both w;th conventional polyimide a~d with known polyphenylene layers. The polyimide used was obtained from Messrs. Merck, Federal Republic of Germany, and the polyphenylene used from Messrs. ICI, Great Britain. Using a customary spincoating process, these materials were applied to substrate plates made of glass, and tempered in the usual way.
The subsequent rubbing in a specified orientation direction, too, was performed in the conventional way, i.e. with the customary rubbing speed and customary rubbing pressure. A velvet-covered roller was used, the length of the velvet hairs being about 2 mm. It must be noted that up to this point in the production process there is no difference from the customary processes already known.
Then, however, the layers were rubbed in the opposite direction, using the same velvet roller and the same rubbing speed, but with a reduced rubbing pressure. The roller was moved only near enough to the orientation layer for the velvet hairs just to touch down on the layer. During rubbing in the original direction, contrariwise, the distance between orientation layer and roller was about 1/4 - 1/2 mm less, so that the velvet hairs (about 2 ~m in length) were considerably bent.
It has emerged that it is of advantage to rub several times with a weakpressure. Probably, when the pressure applied is weak, there are, statistically speaking, relatively large differences in treatment in the different areas, which differences are equalized by repeated rubbing.
~here is no certain explanation for the effect observed, neither is there a substantiated explanation for the effects of pretilt and orientation generation. Observations made on slantwise-deposited inorganic layers ;ndicate that the pretilt is determined not anly by chemical-physical properties, but also by mechanical properties of the layer, namely by a corrugated structure. If such a corrugated structure is likewise generated S. Brosig-19-3 03 . 10. 1989 .
::
~ ' with the customary relatively strong rubbing of a polymer orientation layer, it can be i~agined that the weak rubbing in the opposite direction leads to the crests of the corrugations being pushed somewhat backwards and therefore increased in height. Th;s would render ;t plausible that the we~k rubbing in the opposite direction causes an ;ncrease ;n pret;lt.
~ust as customarily the optimum rubbing pressure, the optimum rubbing speed and the optimum rubbing mater;al have to be found for every orientation-layer mater;al used and every concrete product;on sequence, it is also necessary ;n the process descr;bed here to ascertain exper;me~tally in each individual case how the process variables must be selected for the rubb;ng in the opposite direction in order to achieve optimum increase in pretilt.
It has, however, emerged that here optimization is considerably simpler than is the case with optimization of conventional rubbing, since the optimization process for the rubbing in the opposite direction follows on the conventional optimization process for the customary rubbing, so that the rubbing material (usually a velvet-covered roller) and the rubbing speed are already essentially settled, and only the rubbing pressure remains to be optimized.
In the experiments described, no equipment for precise measurement of the pretilt was available. The increase in the pretilt was, however, in the case of twisted-nematic liquid-crystal cells easily recognizable between crossed polarizers by the lesser brightness of the cells treated in comparison to the untreated cells. The higher the pretilt, the stronger is the component of polarized light, whose vector is not twisted by the twisted-nematic cell; this non-twisted component is cancelled by the crossed second polarizer. The effect of decreasing brightness was equally evident both when using polyimide for the orientation layer and also when using polyphenylene. In the conventional production method, the pretilt when using conventional polyimide measures about 1 - 5, while the pretilt when using polyphenylene measures about 10 - 20, depending on how elaborately the process is conducted. The increase in pretilt generated by light rubbing in the opposite direction is estimated (in view of the brightness reduction observed) as a few degrees, and probably measures about 3 - 6.
S. Brosig-19-3 03.10.1989
DESCRIPTION
Process for producing a l;qu;d-crystal cell The invent;on relates to a process for producing a l;quid-crystal cell, or more prec;sely a process for treat;ng an organic orientation layer on a substrate plate for a liqu;d-crystal cell. Or;entation layers of this type serve to generate an orientat;on and a pretilt of the l;qu;d-crystal molecules. The term "orientat;on" is here taken to mean the angle between the edge of a substrate plate and the projection of a liqu;d-crystal molecule onto th;s substrate plate. The pret;lt ;s the angle by which a liqu;d-crystal molecule ;s t;lted against the plane of the substrate plate.
DESCRIPTION OF THE PR}OR ART
Orientation layers of the type ment;oned are produced with two d;fferent mater;al groups us;ng two different processes. One process utilizes inorganic mater;als wh;ch are vacuum-depos;ted slantwise onto the substrate plate ;n the direct;on of or;entation. The second process ut;lizes organ;c substances wh;chl for example, are appl;ed by spray;ng, ;mmers;on or (as a rule) by sp;ncoat;ng. The polymer films are subjected to a tempering process, and then rubbed w;th a soft mater;al (generally velvet~ aff;xed to a roller. Th;s rubbing ;s performed in the des;red direct;on of or;entation.
It is known from DE 27 22 389 A1 that for orientation and pret;lt sett;ng both processes are used jo;ntly, ;.e. both slantw;se deposit;on and rubbing. The rubbing ;s performed several t;mes ;n a spec;f;ed d;rect;on.
The direction specified will, when a steep deposition angle has been used, stand at r;ght angles to the project;on of the depos;t;on d;rection onto the substrate plate. In the case of flat deposit;on angles, rubb;n~ ;s performed parallel to the projection of the depos;t;on direction onto the substrate plate, from the side on wh;ch due to the slantw;se deposition the l;quid-crystal molecules lie deeper in the fin;shed liqu;d-crystal cell, i.e. in the d;rection of r;sing pretilt, so to speak. This process perm;ts S. Bros;g-19-3 03.10.1989 .
- 2 ~
the pretilt (which is also relatively steep with flat slantwise deposition) to be set to smaller values.
While when using slantwise-deposited ;norganic orientation layers theretend to be problems with the finished liquid-crystal cells due to excess;vely high pretilt angles, the s;tuation is rather the opposite when polymer rubbed orientation layers are used. Efforts have been made in this context to achieve higher pretilt angles by developing the materials used.
Attempts have also been made not to rub the materials, but instead to cause an or;entat;on of the polymer or;entation-layer molecules by pouring these on in the orientation direct;on or by means of other flow-applicat;on processes. It seemed desirable to avoid the rubbing, since it was known that rubbing reduces the originally attainable high pretilt angles (see in this context the findings of DE 27 22 389 A1 quoted above).
All attempts so far made to develop better materials for orientation layers and to improve production methods ~or such layers have not yet led to fully satisfactory results, i.e. to polymer orientation layers with which very high pret;lt angles can be simply and reliably achieved.
DESCRIPTION OF THE INVENTION
The process described ;n the ;nvention for treating a polymer orientation layer is distinguished by the fact that first rubbing is performed in the convent;onal way ;n one d;rect;on one or more times. Then, however, rubbing is performed in the opposite direction but with a weaker application pressure. This rubbing in the opposite direction can also be repeated several times.
It has been shown that with this process the pretilt angles of all organic orientation layers can be increased by some degrees, irrespective of the material used. The increase in pretilt by some degrees is thus achieved both with conventional polyimide orientation layers (which conventionally exhibit a pret;lt of only a few degrees) and with more recently developed materials, e.g. polyphenylene or more recent polyimides, w;th which under S. Brosig-19-3 03.10.1989 ~' - 3 - ~ ~2~
the conventional production processes pretilt angles of about 15 - 20 are ach;eved.
WAYS TO IMPLEMENT THE INVENTION
Trials have been performed both w;th conventional polyimide a~d with known polyphenylene layers. The polyimide used was obtained from Messrs. Merck, Federal Republic of Germany, and the polyphenylene used from Messrs. ICI, Great Britain. Using a customary spincoating process, these materials were applied to substrate plates made of glass, and tempered in the usual way.
The subsequent rubbing in a specified orientation direction, too, was performed in the conventional way, i.e. with the customary rubbing speed and customary rubbing pressure. A velvet-covered roller was used, the length of the velvet hairs being about 2 mm. It must be noted that up to this point in the production process there is no difference from the customary processes already known.
Then, however, the layers were rubbed in the opposite direction, using the same velvet roller and the same rubbing speed, but with a reduced rubbing pressure. The roller was moved only near enough to the orientation layer for the velvet hairs just to touch down on the layer. During rubbing in the original direction, contrariwise, the distance between orientation layer and roller was about 1/4 - 1/2 mm less, so that the velvet hairs (about 2 ~m in length) were considerably bent.
It has emerged that it is of advantage to rub several times with a weakpressure. Probably, when the pressure applied is weak, there are, statistically speaking, relatively large differences in treatment in the different areas, which differences are equalized by repeated rubbing.
~here is no certain explanation for the effect observed, neither is there a substantiated explanation for the effects of pretilt and orientation generation. Observations made on slantwise-deposited inorganic layers ;ndicate that the pretilt is determined not anly by chemical-physical properties, but also by mechanical properties of the layer, namely by a corrugated structure. If such a corrugated structure is likewise generated S. Brosig-19-3 03 . 10. 1989 .
::
~ ' with the customary relatively strong rubbing of a polymer orientation layer, it can be i~agined that the weak rubbing in the opposite direction leads to the crests of the corrugations being pushed somewhat backwards and therefore increased in height. Th;s would render ;t plausible that the we~k rubbing in the opposite direction causes an ;ncrease ;n pret;lt.
~ust as customarily the optimum rubbing pressure, the optimum rubbing speed and the optimum rubbing mater;al have to be found for every orientation-layer mater;al used and every concrete product;on sequence, it is also necessary ;n the process descr;bed here to ascertain exper;me~tally in each individual case how the process variables must be selected for the rubb;ng in the opposite direction in order to achieve optimum increase in pretilt.
It has, however, emerged that here optimization is considerably simpler than is the case with optimization of conventional rubbing, since the optimization process for the rubbing in the opposite direction follows on the conventional optimization process for the customary rubbing, so that the rubbing material (usually a velvet-covered roller) and the rubbing speed are already essentially settled, and only the rubbing pressure remains to be optimized.
In the experiments described, no equipment for precise measurement of the pretilt was available. The increase in the pretilt was, however, in the case of twisted-nematic liquid-crystal cells easily recognizable between crossed polarizers by the lesser brightness of the cells treated in comparison to the untreated cells. The higher the pretilt, the stronger is the component of polarized light, whose vector is not twisted by the twisted-nematic cell; this non-twisted component is cancelled by the crossed second polarizer. The effect of decreasing brightness was equally evident both when using polyimide for the orientation layer and also when using polyphenylene. In the conventional production method, the pretilt when using conventional polyimide measures about 1 - 5, while the pretilt when using polyphenylene measures about 10 - 20, depending on how elaborately the process is conducted. The increase in pretilt generated by light rubbing in the opposite direction is estimated (in view of the brightness reduction observed) as a few degrees, and probably measures about 3 - 6.
S. Brosig-19-3 03.10.1989
Claims (2)
1. Process for treating an organic orientation layer on a substrate plate for a liquid-crystal cell, with the orientation layer serving to generate an orientation and a pretilt of liquid-crystal molecules, in which process - the orientation layer is rubbed in a specified direction in order to achieve the desired orientation effect, characterized in that - the orientation layer is then rubbed in the opposite direction with a weaker rubbing pressure, thus increasing the pretilt effect.
2. Process in accordance with Claim 1, characterized in that the orientation layer is rubbed several times in the opposite direction with a weak rubbing pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3933422.8 | 1989-10-06 | ||
| DE3933422A DE3933422A1 (en) | 1989-10-06 | 1989-10-06 | METHOD FOR PRODUCING A LIQUID CRYSTAL CELL |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026361A1 true CA2026361A1 (en) | 1991-04-07 |
Family
ID=6390974
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002026361A Abandoned CA2026361A1 (en) | 1989-10-06 | 1990-09-27 | Process for producing a liquid-crystal cell |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0421190B1 (en) |
| JP (1) | JPH03139613A (en) |
| CA (1) | CA2026361A1 (en) |
| DE (2) | DE3933422A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0613037B1 (en) * | 1993-01-29 | 2001-05-16 | Sharp Kabushiki Kaisha | A liquid crystal display apparatus,a method for producing the same,and a substrate |
| DE69427202T2 (en) * | 1993-01-29 | 2001-10-18 | Sharp Kk | Liquid crystal display device, method of manufacturing the same, and a substrate |
| US5689322A (en) * | 1993-07-30 | 1997-11-18 | Sharp Kabushiki Kaisha | Liquid crystal display device having regions with different twist angles |
| TW259845B (en) * | 1993-07-30 | 1995-10-11 | Sharp Kk |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2568574B2 (en) * | 1987-08-26 | 1997-01-08 | 松下電器産業株式会社 | Liquid crystal cell manufacturing method |
-
1989
- 1989-10-06 DE DE3933422A patent/DE3933422A1/en not_active Withdrawn
-
1990
- 1990-09-19 EP EP90118009A patent/EP0421190B1/en not_active Expired - Lifetime
- 1990-09-19 DE DE59006208T patent/DE59006208D1/en not_active Expired - Fee Related
- 1990-09-27 CA CA002026361A patent/CA2026361A1/en not_active Abandoned
- 1990-10-05 JP JP2266544A patent/JPH03139613A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0421190A3 (en) | 1992-03-04 |
| EP0421190A2 (en) | 1991-04-10 |
| EP0421190B1 (en) | 1994-06-22 |
| DE59006208D1 (en) | 1994-07-28 |
| DE3933422A1 (en) | 1991-04-11 |
| JPH03139613A (en) | 1991-06-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |