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
  • G02F1/137—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
• • 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
  • G02F1/1339—Gaskets; Spacers; Sealing of cells
  • G02F1/13394—Gaskets; Spacers; Sealing of cells spacers regularly patterned on the cell subtrate, e.g. walls, pillars
• • 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
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/133509—Filters, e.g. light shielding masks
  • G02F1/133512—Light shielding layers, e.g. black matrix
• • 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
  • G02F1/137—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
  • G02F1/139—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
  • G02F1/141—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 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent using ferroelectric liquid crystals
• • 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
  • G02F1/1339—Gaskets; Spacers; Sealing of cells
  • G02F1/13392—Gaskets; Spacers; Sealing of cells spacers dispersed on the cell substrate, e.g. spherical particles, microfibres

Definitions

• the present invention relates to a ferroelectric liquid crystal screen, with electrodes opacified in the non-switchable region of the screen as well as a method for obtaining spacers for this screen and a method for processing the screen. It applies to the display of information (images, characters,
• the invention is for example achievable with the chiral smectic liquid crystals C, I, F, G or H inclined (tilted according to English terminology), and in particular with the liquid crystals with chiral smectic phase C.
• a display device is described, the electrooptic display material of which is a liquid crystal with chiral smectic phase C.
• This display device shown diagrammatically in longitudinal section in FIG. 1, comprises a first linear polarizer 2 and a second crossed linear polarizer 4, between which is inserted a waterproof display cell 6.
• This display cell operating in transmission is formed by two walls, or plates, electrically insulating and transparent 10 and 12, generally made of glass. These walls, parallel to each other, are made integral by their edges by means of a bonding 14 serving as a seal.
• the walls 10 and 12 are covered respectively with an electrode 16 and a counter-electrode 18 of a shape suitable for display, made of a transparent conductive material.
• the electrode and the counter electrode may each be formed of parallel conductive strips, The strips of the electrode, which can be called “column electrodes”, and the strips of the counter electrode, which can be called “line electrodes”, being crossed, that is to say perpendicular.
• the electrode and the counter-electrode make it possible to apply to the terminals of a liquid crystal film 20 with chiral smectic phase C, contained in cell 6, an electric field continuous whose direction or value can be changed.
• the electrode 16 and the counter electrode 18 are connected, by means of an inverter 22, to a source of continuous electrical power 24.
• a molecular scale shows the structure of a smectic phase C liquid crystal film when it is contained in the display cell 6.
• the lower wall 12 constitutes for example a reference plane containing the two axes X and Y of an orthogonal XYZ coordinate system.
• the smectic liquid crystal film C is composed of molecules 26 of elongated shape, having a longitudinal axis 28 and arranged in layers 30. These molecules each have a permanent dipole moment perpendicular to their Longitudinal axis 28.
• the smectic layers 30 are all mutually parallel and oriented perpendicular to the walls 10 and 12 of the cell.
• the solid lines have been represented molecules 26 of the liquid crystal in a first orientation A 1 (state 1) forming an angle - ⁇ with respect to the direction X, the dipole moments being oriented perpendicular to the walls 10 and 12 of the cell and in the direction of the electric field going from the wall 10 towards the wall 12.
• the change of polarity of the electric field allows the tilting of the dipole moments in the opposite direction (from wall 12 to wall
• FIG. 2 also shows the respective polarization directions P and P 'of the straight polarizers Lines 2 and 4.
• Liquid crystals with a chiral smectic C phase, oriented correctly can therefore be used as display materials. They are likely, in addition to their bistability, to present interesting properties such as a rapid response or switching time, of the order of a microsecond, for low voltages applied to the electrodes (a few volts) and a wide response. electrooptical.
• the thickness of Liquid crystal must be extremely small, of the order of 2 micrometers for example.
• the spacing of the walls 10 and 12 leading to such a thickness is generally obtained by means of spacers made up of calibrated plastic balls.
• FIG. 3 there is shown very schematically and in top view a liquid crystal display screen which comprises line electrodes 32 transparent and parallel to each other and transparent column electrodes 34, parallel to each other and perpendicular to the line electrodes.
• This contrast is defined by the ratio of the intensity transmitted in the white state IB to the intensity transmitted in the black state IN.
• the intensity of the black state corresponding for example to state 1 of the device described with reference to FIGS. 1 and 2, the white state then corresponding to state 2, is as low as possible, so as to have a large IB / IN ratio.
• the non-switchable zone 36 of the screen - it is recalled that the switchable zone, referenced 38 in FIG. 3, corresponds to all of the "overlaps" of the electrodes 32 and 34 (in top view) and that the non-switchable area (or non-addressable area) corresponds to the rest of the screen - contains substantially equal densities of states 1 and states 2.
• the surface treatments which allow the orientation of the liquid crystal are such that the two states are equiprobable in the non-switchable zone.
• This non-switchable zone 36 therefore appears gray when an appropriate electrical voltage is established between the electrodes 32 and 34 and that straight line polarizers are suitably arranged on either side of the assembly, or cell, comprising the electrodes 32, 34 (respectively arranged on electrically insulating plates generally glass) and the layer of liquid crystal.
• non-switchable area cannot be reduced significantly, since in particular for large, complex screens, the yields of the etchings necessary for their manufacture impose a size limit on the non-switchable area.
• This problem relating to the gray appearance of the non-switchable zone is also encountered with screens using other liquid crystals.
• the problem in question is then resolved by placing between the line electrodes and between the column electrodes a screen opaque to light.
• This screen generally consists of an electrically insulating colored material, the thickness of which must be of the order of a few microns, 1 to 2 microns for example, so that the insulating material is sufficiently absorbent.
• Such a thickness is incompatible with screens using a ferroelectric liquid crystal. Indeed, the thickness of the layer of this Liquid crystal does not allow the crossing of layers of colored insulating material, arranged in the intervals separating the electrodes-lines and of layers of this same material, arranged in the intervals separating the electrodes- columns.
• the density of these defects depends on the liquid crystal used and on the surface treatments carried out on the plates between which this liquid crystal is located.
• One of the possible surface treatments consists in placing on each of these plates a layer of an appropriate material and rubbing the layers of this material either parallel to the line electrodes or parallel to the column electrodes.
• the object of the present invention is to improve the contrast of a ferroelectric liquid crystal screen, for example of a screen using a chiral smectic liquid crystal inclined C, by opacifying in a particular way the non-switchable zone of the screen. and allowing to push back the defects zig-zag in the non-switchable area of the screen or in the vicinity of this area.
• the present invention firstly relates to a ferroelectric liquid crystal screen comprising an assembly comprising a layer of ferroelectric liquid crystal capable of exhibiting zigzag defects, this layer being between a group of electrodes -transparent lines, parallel and separate from each other and a group of transparent column electrodes, parallel, separate from each other and perpendicular to the line electrodes, said groups of electrodes being respectively arranged on two electrically insulating and transparent plates , screen characterized in that it further comprises, on each part of each row electrode, facing an interval separating two column electrodes, and on each part of each column electrode, facing a gap separating two electrodes -lines, an element intended to prevent the crossing of the screen by an incoming light ant on this screen in the direction of this element, and in that the elements which are arranged on the row electrodes or the elements which are arranged on the column electrodes are further provided to allow spacing, without electrical connection between the row electrodes and column electrodes, of the screen plates and have dimensions which, counted parallel to these plates, allow the
• said elements are therefore arranged in the non-switchable zone of the screen, which makes it possible to suppress the gray appearance of this zone, mentioned above, the technique used in the present invention to make the non-zone opaque. switchable screen remaining compatible with the extreme thinness of the ferroelectric liquid crystal layer used.
• the thickness of this layer which in fact depends on the liquid crystal used, is generally of the order of 1.5 micrometers to 2 micrometers. Furthermore, because the elements allowing the spacing of the plates, and thus having the function of spacers, are placed in the non-switchable area of the screen, the zig-zag defects are no longer hampered in the switchable area of the screen and, after a more or less long time of use (of addressing) of the screen, these faults will end up abutting against the elements allowing the spacing of the plates, in the opaque non-switchable zone or in the vicinity thereof.
• the screen generally also comprises two polarization means located on either side of said assembly.
• These polarization means can consist of two crossed rectilinear polarizers.
• each element comprises an opaque layer which covers the electrode part on which this element is disposed and each element allowing the spacing of the plates comprises, in addition to this opaque layer, an electrically insulating spacer which is placed on the latter.
• the width of the opaque layer is greater than the width of the interval separating two electrodes and facing the part which is covered by this opaque layer, in particular to favor the positioning of the opaque layers situated on a plate relative to the corresponding interelectrode spaces, located on the other plate and mask the edge of the electrodes which are opposite the opaque layers, this edge being liable to exhibit imperfect switching.
• each spacer has an elongated shape transverse to the electrode on which the element comprising this spacer is disposed. This increases in particular the rigidity of the screen compared to that of known screens, using balls as spacers.
• the width of each spacer may be greater than the width of the gap separating two electrodes and facing the part on which the element comprising this spacer is placed.
• the width of each spacer is less, for example by half, than the width of the gap separating two electrodes and facing the part on which the element comprising this element is placed. spacer. Indeed, in some cases considered below, it is preferable to have such a small width. as possible for the spacers in order to best conceal the zig-zag defects.
• this screen further comprising two crossed line recti polarizers, on either side of said assembly, each element allowing the spacing of the plates is an electrically insulating spacer which has an elongated shape transversely to the electrode on which this element is disposed and a width greater than the width of the gap separating two electrodes and facing the electrode part on which the element is disposed, this element is made of an optically isotropic material and each element preventing said passage of the screen by light without allowing the spacing of the plates is made of an opaque layer which covers the electrode part on which the latter element is disposed.
• the optically isotropic material can be a photosensitive, optically isotropic resin.
• This material can be transparent or opaque.
• said plates being further coated with orientation layers of the liquid crystal which are made anisotropic in a direction parallel to the electrodes of one of the two groups of electrodes, the elements allowing the spacing of the plates are arranged on the electrodes of this group.
• the zig-zag defects are parallel to the direction of the spacers - we mean by this, the direction which is parallel to the length of these spacers - and in such a case, it is preferable that the width of the spacers is less - of preferably much lower - than that of the inter-electrode interval relative to the other group of electrodes, in order to be able to repel the zig-zag faults in the non-switchable zone of the screen.
• said plates being further coated with orientation layers of the liquid crystal which are made anisotropic in a direction parallel to the electrodes of one of the two groups of electrodes, the elements allowing the spacing of the plates are arranged on the electrodes of the other group.
• the zigzag defects are perpendicular to the direction of the spacers and in such a case, it is preferable that the length of each spacer is substantially equal to the width of the electrode which carries this spacer, in order to confine the zig-zag faults in the non-switchable area of the screen, whereas in the case considered above, this length may be less than or equal to this electrode width.
• this length of spacer is of the order of the width of the electrode in question in order to obtain a screen of good rigidity.
• the width of these spacers is less than or equal to that of the corresponding opaque layers.
• Each opaque layer can advantageously be an opaque metallic layer. Indeed, the metal layers are opaque at low thicknesses which are compatible with the low thickness of liquid crystal used in the present invention.
• a layer of chromium can be used and this layer of chromium can have a thickness of between approximately 30 nm and approximately 200 nm.
• the liquid crystal can be chosen from the group comprising the chiral smectic liquid crystals C, I, F, 6, H inclined.
• the present invention also relates to a process for obtaining the spacers of the particular embodiment mentioned above, an embodiment in which the spacers are on opaque layers, this process being characterized in that it comprises:
• the present invention also relates to a method for processing the screen which is the subject of the invention.
• This method is characterized in that it comprises the application, between the row electrodes and the column electrodes, of an alternating electric voltage, while maintaining the screen at a temperature close to the phase transition temperature ferroelectric smectic to the immediately higher phase (from the point of view of temperature) of the liquid crystal, in order to locate the zigzag faults of the liquid crystal in the vicinity of the non-switchable area of the screen.
• FIG. 3 is a schematic view of the row electrodes and the column electrodes of a liquid crystal display screen
• FIGS. 4 and 5 are schematic and partial views of a screen according to the invention.
• FIG. 6 is a top view of part of the screen shown in Figure 5
• FIG. 7 and 7A are schematic and partial views of other screens according to the invention.
• FIGS. 8A to 8E schematically illustrate different steps of a method for producing a screen according to the invention
• FIG. 9 schematically illustrates a step of a variant implementation of this method
• FIGS. 10A and 10B schematically and partially represent a screen according to the invention.
• FIG. 11 shows schematically and partially another screen according to the invention.
• FIG. 4 schematically and partially illustrates a particular embodiment of the invention: a layer 40 (respectively 42) of an opaque material, of thickness compatible with the thickness of the layer of ferroelectric liquid crystal used, is formed on each line electrode 32 (respectively column 34) in the form of a strip (see FIG. 3), opposite each of the intervals separating the column electrodes (respectively-lines).
• a layer of chromium is used, the thickness of which is a few tens of nanometers, for example, which is enough to make this layer opaque.
• the chromium layer is etched so as to remain only on the electrodes 32, 34 and more precisely on the parts of these, which are opposite the intervals in question, to form on each electrode-line 32 (respectively - column 34) a succession of rectangular patterns whose width is equal - or, preferably, greater - than that of the interval between two column electrodes (respectively -lines) and whose length is equal to the width of the row electrodes (respectively - columns).
• the interval between two patterns corresponding to the row electrodes is equal - or preferably, less - to the width of the column-electrode electrodes (respectively -lines).
• the relative positioning of the glass plates 44 and 46 respectively carrying the row electrodes and the column electrodes then makes it possible to cause said patterns to optically close off the greater part of the non-switchable zone: the patterns produced on the row electrode (respectively - columns) face the intervals separating the column electrodes (respectively - lines).
• the non-switchable zone made opaque is used as explained above, seeking to locate the faults in this zone or in the vicinity of this one.
• a zig-zag defect (generally in the form of a line) sees its migration stopped by its encounter with a dust or a spacer.
• a dust or a spacer sees its migration stopped by its encounter with a dust or a spacer.
• plastic balls as spacers, these balls being distributed randomly over a pixel, is unacceptable.
• spacers 50 such as photosensitive resin pads are produced in the non-switchable region 36 made opaque of the screen (FIG. 6). In this way, the switchable area of the screen has no spacer capable of hindering the migration of faults.
• These spacers are respectively arranged either on the opaque patterns which are found on the line electrodes (FIG. 6) or on the opaque patterns which are found on the column electrodes (case of FIG. 7 where the spacers bear the reference 52).
• Each spacer has the shape of a parallelepiped block, the width of which may be less, for example by half, than that of the inter-electrode space which faces it, that is to say the space separating two electrodes- columns (respectively -lines) if the spacers are on the row electrodes (respectively -columns).
• the length of the block is less than or equal to the width of the electrode on which it is located.
• FIGS. 5 to 7A it is known that these orientation layers must be given an anisotropy direction, for example by rubbing.
• the defects are placed perpendicular to this direction of anisotropy (which can be either parallel to the row electrodes or parallel to the column electrodes).
• We can therefore orient the spacers (in the direction of their length) perpendicular to the intended direction of friction D1 ( Figure 6) and give them a width less than that of the corresponding opaque patterns (which is the case for the screen of the Figure 6), so that the zig-zag defects, which are then parallel to the spacers, can be blocked in the non-switchable zone, the length of the spacers being less than or equal to the length of the electrodes on which they are arranged.
• the spacers can be oriented parallel to the intended rubbing direction (case of FIG. 7 where this direction bears the reference D2) and give them a length equal to the width of the electrodes on which they are located (the column electrodes in the case of FIG. 7), so that the zigzag defects ZZ, which are then perpendicular to the spacers, can be blocked in the non-switchable zone of the screen, the width of the spacers then being equal to the width of the opaque material, or less than this width and in the latter case, it is preferably either less than or greater than the width of the opposite interelectrode space.
• FIG. 7A an embodiment of the invention is shown which is identical to that of FIG. 7, except that the width of each spacer is greater than that of the inter-electrode space which faces it.
• ITO indium tin oxide
• a layer of positive photosensitive resin 58 is then spread over the chromium layer 56, the thickness of which is equal to that which is provided for the spacers, ie a thickness of between approximately 1.5 and 2 micrometers for liquid crystals of the type Inclined smectic chirals (Figure 8B).
• the resin is first exposed through the mask used to define the electrode-lines 32 (respectively -columns 34), the resin is developed and then the layers of chromium 56 and ITO 54 are etched, which defines line electrodes 32 (respectively -columns 34), coated with the chromium layer (FIG. 8C).
• the resin is exposed a second time through an appropriate mask, to define the patterns of chromium 40 (respectively 42), the resin is developed and the chromium remaining unprotected by the resin is removed by etching ( Figure 8D). so that there remain the row electrodes (respectively - columns) provided with chrome patterns which correspond to them and which are surmounted by a calibrated resin layer, these patterns having a width at least equal to the inter-electrode space - column (respectively -line).
• the resin is annealed at 200 ° C. for approximately one hour so that the spacers 50 thus produced by these layers of resin do not deform.
• the plate 46 carrying the column electrodes its resin is removed (so as not to prevent the subsequent introduction of liquid crystal between the plates 44, 46 combined).
• this resin is removed after the step comprising the second exposure of said resin, its development and etching allowing the definition of chromium patterns (FIG. 8D), after which a layer 60 of positive resin is spread whose thickness is calibrated and corresponds to that which is provided for the spacers (FIG. 9 ) and this layer 60 is exposed through the glass plate in question, so that the chrome patterns serve as a mask (FIG. 9). Then, the resin is developed and annealed for one hour at 200 ° C.
• each spacer covers the entire pattern of corresponding chrome 40 or 42.
• the defects in the form of lines are located at the edge of the pixels (after for example heating and application of the electric voltage -see above), this which is visually embarrassing.
• It is nevertheless possible to completely locate the faults in the non-switchable zone by making spacers which each occupy a smaller surface (FIG. 6), each spacer, seen in section parallel to the plates 44, 46, having for example the shape of a rectangle whose width is less than the length and width of the corresponding pattern.
• an additional suitable mask is used to expose the layer 60 or 50 (52) of resin.
• orientation layers are used. These are, for example, produced in the following manner: a layer 62 of silica, 60 nanometers thick for example, is deposited in the vapor phase on the face of each plate 44, 46 which carries the electrodes, and is formed on this silica layer an alignment layer 64 of nylon 6 (R) or polyamide 6, of thickness 150 nanometers for example, in a manner known in the state of the art. This layer 64 is then annealed for one hour at 120 ° C. and then rubbed in a known manner in a chosen direction which. is either parallel or perpendicular to the electrodes on which the spacers are located and in one and / or the other direction relative to this direction.
• R nylon 6
• polyamide 6 polyamide 6
• the screen is then heated to 120oC and therefore the liquid crystal so that it is in its isotropic phase and, at this temperature, an alternating voltage of the order of 30V is applied between each row electrode and each column electrode to bring the zigzag defects in the vicinity of the spacers.
• the resin is that which is marketed by the company SHIPLEY under the reference 1350J; it is developed, with the developer
• the liquid crystal is for example either the mixture A indicated below, or this mixture A doped with 0 to 35% by volume of the compound B also indicated below.
• line 66 and 68 polarizers (FIG. 5) are put in place on either side of the sealed cell obtained, so that their respective directions of polarization are perpendicular and the polarizer first encountered by the light allowing 'Illuminating the screen has its direction of polarization parallel to one of the two directions A1 or A2 of orientation of the ferroelectric liquid crystal molecules.
• FIG. 5 also shows conventional control means 70 for the row electrodes and column electrodes and the liquid crystal layer is referenced 72.
• the mixture A is composed, by volume, of:
• This phenol is 4- (4-heptyloxy-3-bromobenzoyloxy) - biphenyl-4'-ol of formula:
• the cooled solution is then acidified with a 10% HCl solution by volume in water and extracted 3 times with ether (30 ml).
• the precipitate obtained is filtered.
• the solution is taken up in 25 ml of methylene chloride and washed with: - 3 x 15 ml of H 2 O,
• the aqueous phases are taken up twice with 25 ml of methylene chloride.
• the transition temperatures of the final product are:
• K represents the solid state, Se a smectic structure C, * a chiral structure, N a nematic structure, I an isotropic structure.
• the spacers are on the line electrodes 32 and the rubbing direction D1 is parallel to these electrodes.
• the electrodes are made of ITO and have a width of 300 micrometers.
• the opaque patterns are in chrome, have a thickness of 100 nanometers and a width of 60 micrometers while the inter-electrode-column spaces are only 40 micrometers wide.
• Each spacer surmounting a chrome motif is made of photosensitive resin, has a width of 20 micrometers, a length of 300 micrometers and a height of 1.6 micrometers.
• FIG. 11 Another example is schematically and partially shown, in perspective, in FIG. 11.
• the opaque patterns, in chrome, do not carry any spacer and are all placed on the electrodes of the same group of electrodes (either the line electrodes, or the column electrodes) and the spacers 52a (electrically insulating) are carried directly by the electrodes of the other group.
• the chrome patterns are carried by the column electrodes and the spacers by the row electrodes.
• the rubbing direction D2 is parallel to the spacers, the length of which is equal to the width of the electrodes which carry them so as to be able to confine the zigzag defects ZZ in the non-switchable zone.
• the spacers can be opaque or transparent and have a width greater than that of the inter-electrode gap facing them. They must be optically isotropic so that, even if they are transparent, they cooperate with the crossed line recti polarizers 66, 68 with which the screen of FIG. 11 is provided, to stop the light falling on the screen in the direction of spacers. In the example shown in FIG.
• the electrodes have a width of 300 micrometers and the interelectrode space has a width of 40 micrometers;
• the chrome patterns have a thickness of 0.1 micrometers and a width of 60 micrometers;
• the spacers 52a are made of photosensitive resin, have a thickness of 1.5 micrometers, a length equal to the width of the electrodes which carry them and a width of 60 micrometers.

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• Nonlinear Science (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Mathematical Physics (AREA)
• Liquid Crystal (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

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• 1987
  • 1987-07-20 FR FR8710215A patent/FR2618587B1/fr not_active Expired - Lifetime
• 1988
  • 1988-07-20 FI FI900176A patent/FI900176A0/fi not_active IP Right Cessation
  • 1988-07-20 JP JP63506220A patent/JPH03501169A/ja active Pending
  • 1988-07-20 EP EP88907009A patent/EP0400007A1/de not_active Ceased
  • 1988-07-20 KR KR1019890700502A patent/KR890702071A/ko not_active Withdrawn
  • 1988-07-20 WO PCT/FR1988/000375 patent/WO1989000713A1/fr not_active Ceased
• 1990
  • 1990-01-22 NO NO900301A patent/NO900301D0/no unknown
• 1991
  • 1991-07-24 US US07/735,193 patent/US5138473A/en not_active Expired - Fee Related

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