FR2534716A1 - MEMORY NEMATIC LIQUID CRYSTAL DISPLAY DEVICE - Google Patents

Abstract

THE INVENTION RELATES TO LIQUID CRYSTAL DISPLAY DEVICES. AN ELECTRICAL SWITCHING OF A BISTABLE NEMATIC LIQUID CRYSTAL CELL BETWEEN TOPOLOGICALLY EQUIVALENT ASYMETRIC HORIZONTAL STATES IS PERFORMED. THE CELL INCLUDES TOP AND LOWER SUBSTRATES 10, 11 PARALLEL, TEXTURED TILT ALIGNMENT SURFACES 20, 21 ON THE CORRESPONDING SUBSTRATES, AND A NEMATIC LIQUID CRYSTAL MATERIAL 30 BETWEEN THE SUBSTRATES. THE SWITCHING IS TRIGGERED BY THE APPLICATION OF A CONTINUOUS ELECTRIC FIELD TO BREAK THE SYMMETRY AND THE SWITCHING IS COMPLETED BY THE APPLICATION OF AN ALTERNATIVE ELECTRIC POTENTIAL. APPLICATION TO RAPID MATRIX DISPLAY DEVICES.

Description

25347 1 6

  The present invention relates to display devices, and in particular to crystal devices

bistable liquids.

  Bistable nematic liquid crystal display devices generally require potentials

  high electrical appliances to trigger the switching

  interstate between bistable states An important reason

  for the need for such high alternative switching electrical potentials is that sufficient electrical energy must be applied to each

  display cell for detaching and relocating disclin-

  sounds from de-fixation sites.

  An embodiment of a display device

  The two states, which exist separately in the absence of a holding potential, are not equivalent to topological point of view and derive their stability from the setting of disclinations.

  interstate switching by detaching and relocating

  bends from a fastening site, under the effect of an applied alternating switching potential that exceeds a high-value, sharp switching threshold. A reduction in the switching threshold level for this type is achieved.

  pre-polarized liquid crystal display device

  selected cells in the display with a

  potential for alternative preparation before applying

  higher switching potential.

  It should be noted with regard to the provisions

  described above that alternative switching potentials are used to perform inter-state switching. The signals that produce these

  alternative switching potentials come generally-

  of the family of constant-envelope signals and, more particularly, of the family of

  in the form of pulses, transmitted selectively and

  practically constant loppe

  constant-current signals to continuous or constant-amplitude signals, because these latter signals give rise to charge-space polarization effects which reduce the amplitude of the electric field

applied.

  In the display devices mentioned

  above, the problems of alternative switching potentials

  relatively high birthdays and switching by movement

  disclinations still exist.

  In accordance with the invention, a low DC electrical potential is applied to the nematic liquid crystal display cell to initiate bistable inter-state switching between two topologically equivalent horizontal orientation director configurations. configuration

  towards which an interstate switching cycle is triggered.

  Once switching has begun, a low AC potential is applied to the cell.

  example, less than ten volts, to complete the communication cycle.

  tation and to maintain the configuration of directors

  orientation in one of the two horizontal states.

  the nematic liquid crystal display bistable

  takes upper and lower substrates, a nematic liquid crystal material disposed between the two substrates and a combination of elements formed from a single

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  3- keeping with the substrates and able to orient preferentially directors of the crystal material

  in an asymmetric horizontal state with a

  substantially parallel to a predetermined substrate, in the presence of a continuous electric field of symmetry breaking, followed in sequence by a

  applied alternative electric potential.

  In one embodiment of the invention, the liquid crystal display cell comprises parallel upper and lower substrates on which electrically conductive strips and tilt-aligned surfaces, textured from the point of view, are arranged. topographic material, a nematic liquid crystals material disposed between textured surfaces facing, and a variable potential source connected to the bands

  conductors for generating electric fields of

  in the liquid crystal material A cell is divided into an active region and an isolation region that surrounds the active region In the active region of the cell, the textured inclination alignment surfaces

  side have a corresponding border condition

  at equal and opposite inclinations, and a twist

  or an angular difference between azimuthal orientations

  the textured inclination alignment surfaces in

  look, for the optical differentiation of states on each

  textured tilt alignment surface, the region of insulation is characterized by a condition parallel to

  boundaries Inter-state switching is carried out

  as a first continuous potential to the liquid crystal material to trigger the alignment of directors

  orientation in a first asymmetric horizontal state.

  A low alternative holding potential is applied,

  above a critical potential, in a normal direction

  the substrates, to complete the switch to the first

  first state Transitions to the second state are accomplished by applying a second DC potential to the liquid crystal material, thereby triggering correct alignment of the orientation directors in a second asymmetric horizontal state. Here again, the low AC potential is applied. holding to complete the switch

to the second state.

  In another embodiment of the invention, the liquid crystal display cell similarly comprises parallel upper and lower substrates on which are electrically conductive strips and textured tilt alignment surfaces of topographically, the nematic liquid crystal material disposed between textured surfaces facing, and the variable potential source connected to the conductive strips to produce switching electric fields in the liquid crystal material.

  embodiment differs from the embodiment described above

  the fact that the topographically textured inclination alignment surfaces on opposite substrates have a condition on their entire extent corresponding to inverse inclinations at

  The active regions of this latter mode of

  are not defined by the texture of the surfaces

  tilt alignment, but by the region of overlap

  between conductive strips on facing substrates. The invention will be better understood when reading

  the following description of embodiments and in

  referring to the accompanying drawings in which:

  Figure 1 shows a three-dimensional representation

  of a liquid crystal display cell; Figure 2 shows a theoretical representation

  of the upper inclination alignment surface, tex-

  topographically, 20, seen from line 2-2 in Figure 1; Fig. 3 shows a theoretical representation of the topographically textured lower inclination alignment surface, 21, viewed from the line

3-3 in Figure 1; and -

  Figures 4 to 7 illustrate various alignments

  horizontal orientation directors in the region.

  ve of the display cell of Figure 1, in accordance with

to the principles of the invention.

  The invention reveals a new effect

  bistable character for nematic liquid crystals

  the inter-state switching between two topologically equivalent states is triggered by the application of a continuous electrical potential of symmetry breaking. A state in its configuration is maintained.

  correct by then applying a low alterna-

  holding tif Each state has an inversion layer

  at the border with food orientation directors

  almost horizontally, in an adjacent position

  to a corresponding boundary Switching a state-

  to another does not require any movement of disclinations,

  because of the topological equivalence of states.

  Figure 1 shows a display cell with crys-

  liquid rate This display cell is an example

  Embodiment of the invention The cell of FIG. 1 is only one of many such cells which are

  incorporated in a liquid crystal display device

  As shown in Figure 1, the display cell

  liquid crystal display comprises an upper substrate 10,

  a lower substrate 11, a sloping alignment surface,

  superior, topographically textured,

  , a lower inclination alignment surface, tex-

  topographic point of view, 21, a crys-

  Nematic liquid levels 30, an upper conductor 40 and a lower conductor 41 Switching and holding potentials are applied to the cell from a variable potential source 50 which is connected to the upper conductor 40 and the lower conductor 41 A system reference base vectors (x, y, z) are shown in the figures to facilitate the orientation of FIG. 1 with respect to FIGS. 4 to 7. The substrates 10 and 11 respectively support the conductors 40 and 41, while providing a means for containing the liquid crystal material Each substrate consists essentially of a transparent dielectric material such as silicon dioxide or glass,

or a similar material.

  The conductors 40 and 41 are arranged on interior surfaces facing the respective substrates so as to allow the application of an electric field

  continuous alternative in a practically

  to each substrate Interdigitated electrodes

  as electrodes in the form of continuous uniform bands

  are configurations that can be used for

40 and 41.

  Figure 1 shows, by way of example only,

  the conductors 40 and 41 in the form of electrodes in the form of

  continuous uniforms arranged in a mutually

  The conductor 40 is formed on an integral surface

  the conductor 41 is similarly formed on an inner surface of the lower substrate 11, in a direction orthogonal to the direction of the conductor 40. Each conductor is deposited or etched by conventional photolithographic techniques in the form of 'a thin layer on the inner surface

  of the respective substrate Conductors

  transparent films such as indium-tin oxide, on the two display cell substrates operating in

  mode of transmission, while in the display cells

  in the mode of reflection, we use

  opaque ones consisting for example of aluminum, for

  conductors that are on one of the substrates.

  Inclined alignment surfaces are used

  Topographically textured regions, 20 and 21, to induce a known tilt alignment in the liquid crystal molecules adjacent to each surface. These surfaces are also referred to as "tilting alignment surfaces." Surfaces 20 and 21 are transparent non-conductive layers on surfaces.

  exposed surfaces of substrates and transducers, to define

  The surfaces 20 and 21 are formed in one piece with the respective substrate by depositing a surface alignment of the orientation directors of the liquid crystal material.

  oblique electron beam or thermal evaporation

  than a material such as titanium oxide or silicon oxide, these two materials constituting insulators This leads to a topography in the form of columns uniformly

  inclined for each inclination alignment surface.

  The topography of each of the surfaces 20 and 21 defines a surface tilt angle O%, measured from the normal to each substrate (interior surface) in the range of 0 to 900. Higher surface tilt angles

  at 450 are preferred to ensure the preponderance of

  horizontal representation of guidance directors

  Tilt alignment faces 20 and 21 are described more fully below in connection with FIGS. 2 and 3.

  The liquid crystal material 30 is a substance

  this liquid crystal-in the nematic mesophase having a

  positive dielectric anisotropy, at least in some

  frequency range, in an example of a display cell

  In the present invention, the material consists of E-type cyanodiphenyl samples from Merck Chemical Company.

  liquid crystal 30 is placed between parallel substrates.

  the opposites, and the separation between the surfaces of

  substrates is less than 20 rm and is typically

about 10 pm.

  Each display cell is divided into one

  active region and an inactive region The active working region

  takes a volume of liquid crystal material 30 which is capable of performing inter-state switching under the effect of appropriately applied electric fields. In general, for the cell type shown in FIG. 1, the active region is defined as being the region located in the overlap area of the conductors 40 and 41. In FIG. 1, the shaded area on the surface 21

  represents a lower boundary of the active region.

  The inactive region surrounding each active region

  ve is a volume of liquid crystal material that keeps

  a fixed configuration of orientation directors, inde-

  apart from the configurations in the active regions adja-

  Each inactive region, also known as the iso-

  Neutralization, separates, isolates and stabilizes the active region surrounded by a corresponding cell in the liquid crystal display device A theory of regions

  neutral insulation is presented by J Cheng in the article

  entitled "Surface Pinning of Disclinations and the Sta-

  Bility of Bistable Nematic Storage Displays, "J Appl.

Phys. 52, pp. 724-727 (1981).

  US Patent 4,333,708 provides additional information regarding the physical aspects and construction of the basic display cell which is

shown in Figure 1.

  The variable potential source 50 produces several

  any electrical signals that are applied to the upper conductor 40 and the lower conductor 41 to produce various alternating or continuous electric fields in the

  liquid crystal material 30, and in a practical direction

  Normally normal to substrates 10-and 11 Depending on the characteristics of the electric field applied in the region

  of the display cell, the configuration of direc-

  The orientation of the liquid crystal material 30 is changed from a horizontal distorted configuration (FIG. 5) to either an upper asymmetric horizontal state (FIG. 6) or a lower asymmetric horizontal state (FIG. once switching to an asymmetric state is triggered, the source 50 produces a

  alternating sustain signal to complete the com-

  mutation and to maintain the asymmetrical horizontal state

  in the display cell, with holding potential.

  The signals produced by the source 50 generally originate from the families of constant envelope signals and constant amplitude signals. More precisely, the constant envelope signals are alternating signals in the form of pulses, transmitted selectively, with a substantially constant envelope, whereas that constant amplitude signals are continuous signals in the form of pulses,

transmitted selectively.

  To perform the switching in accordance with the principles of the invention, the signals from the source

  50 produce referenced potentials-at a critical potential.

  Vc, which is described below in more detail.

  The signals are classified into broad categories, namely a

  continuous write signal, a continuous initialization signal

  or a continuous erase signal, and an alternating hold signal A write signal from the source 50 applies a continuous potential of value Vw across the display cell to trigger the switching of the

  cell to a first asymmetric horizontal state (superior

  lower or lower), the potential V being higher or lower than the critical potential Vc - so as to produce the

  desired switching characteristics An error signal

  cement applies a potential value VE across the display cell to trigger the switching of the

  cell to a second asymmetric horizontal state (inferred

  or higher), and VE has an absolute value

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  equal to that of VW, but opposite polarity Source 50 produces an alternating hold signal to complete the switch cycle and to maintain orientation directors in the particular asymmetric horizontal state to which they have been switched. establishes at the terminals of the cell an alternative potential

  of a value VH which is at least higher than the cryogenic potential

  It is possible to increase the value of the potential of

  to improve the optical contrast between

  first and second asymmetric horizontal states It should be noted that the potentials VE, VH, VW and Vc depend on the dimensions and other characteristics of the liquid crystal display cell. However, by way of example, it is known that for a single cell thin (10, am of separation between the substrates) containing the material E 7, preferred potentials are the following: Vc = 1.5 volts, Vw and VE between 1.5 volts and 5.0 volts, and V 1 H less than 10.0 volts

  more detailed information concerning the source of potential

  variable 50 and the bistable switching of the LCD cell are given below in

relationship with FIGS. 5 to 7.

  Figure 2 shows a representation of the surface area

  this upper inclination alignment, 20, seen from the position along the line 2-2 in FIG. 1 The inclined alignment surface 20 comprises a surface

  of active region 201 (thick ellipses) and a surface

  this isolation region 202 (ellipses in fine line) The ellipses were drawn to represent columns of

  molecules inclined in the inclined topography of the

  A vector along the main axis of several of the ellipses on the active region surface 201 has been drawn, and this vector represents an orthogonal projection of the main axis of each ellipse, i.e. molecular axis of a metal oxide column, on the tilting alignment surface Because the vector indicates a direction

2 5 3 4 7 1 6

  in which the metal oxide columns are pointed in the oppo-

  on the tilting alignment surface, we can say

  that the vector indicates a direction of inclination of surface

  this for the metal oxide columns, and therefore a direc-

  azimuth deviation for the surface, alignment by inclination. An azimuth deviation for an active region surface is measured in the form of an angular offset with respect to a reference line. In the figures, the line 213 is the reference line. The line 203 is parallel.

  to the vectors on the surface 201 to indicate the direction -

  of azimuthal deflection for the active region surface 201, forming an angle, denoting "the acute angle

  -90 and + 900 It should be noted that the area surface of iso-

  202 is aligned parallel to the direction of

  azimuth deviation of the active region surface 201.

  Figure 3 shows a representation of the surface area

  this lower inclination alignment, seen from the position along line 3-3 in FIG.

  surface 21 comprises an active region surface 211 (elliptical

  thick line) and an insulating region surface 212 (fine line ellipses) Reference line 213 indicates

  also the direction of azimuth deviation for the surface

  this of active region 211, so that the azimuth deviation

  for the surface 211 is 00 The azimuth deviation for the surface 212 corresponds to a direction parallel to

  the deflection direction for surface 211.

  In the active region of the display cell, the surfaces 20 and 21 form a boundary condition corresponding to a reverse tilt. The reverse tilt occurs because the azimuth deviation K of the surface 201 is between -90 È and - + 900 and, when measured as an acute angle from the respective normal to the substrate (inner surface), the surface tilt angle for the surface 201 has a

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  polarity opposite to that of the angle of inclination of surface

  For example, as shown in Figs.

  2 and 3, the surface tilt angle for the surface

  201 is measured in the opposite clockwise direction from the standard

  on the inner surface of the substrate 10, in the form of an acute angle, while the angle of inclination for the

  surface 211 is measured clockwise from the standard

  male to the inner surface of the substrate 11 as shown

  above, the angles of inclination of surface for

  faces 201 and 211 must have absolute values in the

  range from 0 to 900 from the normals to the substrate

  and, more preferably, above 450 to

  to create a horizontal configuration of the directors

  In addition, it is important in the context of

  of the invention that the reverse inclinations are also

  the, so that the absolute value of the angle of inclination

  surface area 201 is almost equal to the absolute value of

  read angle of inclination for surface 211.

  In the isolation region, the surfaces 20 and 21 form a uniformly parallel boundary condition, aligned parallel to the azimuth deviation of the corresponding active region surfaces.

  insulation region 202 and 212 have columns that show

  angle of inclination of about 900 to

  from normal to the substrate (see Figures 2 and 3).

  It has been found that, for ease of manufacture, the con-

  Parallel border edition of surfaces 201 and 202 can

  was obtained by oblique evaporation of Si O x, with the plane of incidence in a direction perpendicular to the preferred azimuthal deflection direction, at an angle

  about 650 relative to normal to the substrate.

  Alignment surfaces with superior inclination

  The bottom and bottom are important, individually and in combination, for the bistable switching of the liquid crystal display cell.

  in order to eliminate a preference of an asymmetrical horizontal state

  in relation to the other, in the absence of an elec-

  In particular, the difference between the azimuthal deviations of the upper and lower active region surfaces provides an optical differentiation between the bistable states. The symmetry of the surfaces in the display cell eliminates one

  preference for the establishment of an asymmetrical horizontal state

  close to a particular surface, in the absence of the field of symmetry rupture.

  more in connection with the description of Figures 4 to 7,

made below.

  Figure-4 shows a three-dimensional representation

the volume of liquid crystal material in the active region of the display cell shown with the orientation directors in a horizontal configuration

  undistorted This is the rest configuration of the cell

  1a, because the orientation directors of the liquid crystal material take this configuration in the absence of an electric field A plane section 401 of a boundary layer contains-directors of the crystal material

  liquids that are oriented almost at the angle of inclination

  surface area of the surface 211, while plane portions 403 of a boundary layer contain directors which are oriented at the angle of surface inclination of

  the surface 201 A flat section 402 of an inversion layer

  The Commission contains guidance directors who are practically horizontal, that is, virtually parallel to

each substrate surface.

  For the sake of simplicity, FIG. 4 only shows sufficient detail to show the plane section 402 as a single section of coplanar orientation directors in the inversion layer. a set of identical planar sections parallel to the plane section 402 which constitute the complete inversion layer Similarly, there are corresponding sets of identical planar sections parallel to each of the plane sections 401 and 403, which constitute the boundary layers to the respective surfaces and 21 This simplification of detail has also been

applied to Figures 5, 6 and 7.

  The alignment of orientation directors is

  not changed from the undisclosed horizontal configuration

  until a symmetry breaking field is applied to the cell. In addition, this change can be maintained provided that a holding potential greater than or equal to the critical potential is then applied to the cell. display The critical potential Vc is defined

  as the potential above which the liquid-crystalline material behaves in a bistable manner with respect to

  Horizontal configurations The critical potential is described in the following manner. It will be assumed that the boundary and inversion layers are completely separated and exhibit a uniform fan-twist deformation energy, U 0, per unit volume, with 1 J = - ' and 0 o 2 L 2 t J e t_ 1 lr 47 k 1 2 denoting by t the length of electrical coherence defined as the characteristic distance over which

  liquid crystal molecules with a module = yen de

  fan-flexion formation k and a dielectric anisotropy AF rotate from a direction perpendicular to a direction parallel to an applied electric field E The energy density per unit area of each boundary layer is proportional to the thickness of the layer particular, a 5 3 4 7 1 6 as shown in the table below: Layer Type Thickness Energy Density (Reference Numbers) per Area Unit Border / 2 U / 2 (5 o 01, 503) Inversion 2 2 U

(502) O

U-border inversion

(504, 505)

  The table above clearly shows that the distorted horizontal configuration shown in FIG.

  a total energy per unit area of 3 Uo, while each

  each of the asymmetrical horizontal states of FIGS. 6 and 7 has a total energy per unit area of 2 Uo However,

  the given argument is not valid for an applied field

  for which the boundary layers and fusion-merge inversion

  on the total thickness, d, of the display cell.

  Therefore, the thickness of the cell, d, is at least

  equal to 35 and the critical potential is given by the relation

  for a cyanodiphenyl sample E 7 and values

  absolute angles of inclination of surface of about 53, -

  the critical potential Vc is approximately 1.3 to

1.7 volts.

  When a potential greater than the critical potential

  that V is applied to the display cell, the direc-

  orientation-of the active region are quickly transformed into a distorted horizontal

  that shown in Figure 5 The horizontal configuration

  The distorted web contains planar sections 501 of the lower boundary layer, a plane section 502 of the inversion layer, and a plane section 503 of the upper boundary layer, hereinafter referred to as the lower boundary layer 501, respectively. inversion 502 and upper boundary layer 503 This state is unstable because

  the overall elastic and dielectric energy of the

  The orientation director can be decreased when the inverting layer 502 merges with the upper boundary layer 503 (FIG. 6) to form the horizontal state.

  asymmetric, either with the inferior border layer

  501 (Figure 7) to form the asymmetric horizontal state

  The two resulting asymmetrical horizontal states have equal energy, they are topologically equivalent and they are separated by an energy barrier

  represented by the distorted horizontal configuration.

  If the continuous potential applied to the cell in the distorted horizontal configuration is Vw, which corresponds to the write signal from the source 50,

  a transformation of the orientation directors is triggered

  from the distorted horizontal configuration (Figure 5) to the upper asymmetric horizontal state shown in Figure 6 Transformation occurs by

  a direct vertical movement of the inversion layer 502 -

  This leads to the formation of the boundary inversion layer 504, adjacent to the active area surface 201 of the surface 20. When the alternative holding potential VH is then applied to the cell via the sustain signal from the

  source 50, the switching cycle is completed and the

  The orientation directors in the boundary inversion layer 504 reside in the plane that contains both the normal to the substrate and the line corresponding to the azimuth deviation for the surface. of

  active region 201, i.e., line 203.

  On the other hand, if the continuous potential that is

  applied to the cell in the horizontal configuration dis-

  twisted is VE, which corresponds to the erasing signal

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  from source 50, a transformation of the directors

  orientation is triggered from the horizontal configuration.

  distal to the asymmetric horizontal state inferred

  which is shown in Figure 7 The transformation occurs by a vertical downward movement of the layer

  inverting 502 to the lower boundary layer 501.

  When an alternative holding potential VH is then

  applied to the cell via the hand signal.

  from the source 50, the switching cycle is completed and the orientation director configuration is maintained in the lower asymmetric horizontal state.

  the border inversion layer 505, the orientation directors

  reside in a plan that contains both the standard

  to the substrate and the line corresponding to the azimuth deviation for the active region surface 211, i.e.

the reference line 213.

  Interstate switching between horizontal states

  asymmetric rates, for example from the higher state to the lower state or from the lower state to the higher state, is accomplished by suppressing the alternative sustain signal that is applied to the cell, and allowing a momentary relaxation of the liquid crystal material 30 which returns it to the distorted horizontal configuration (FIG.) or in the undistorted horizontal configuration (FIG. 4). After a short relaxation time, a continuous write signal or a signal of continuous erase is applied to the cell to trigger the switching of

appropriate way.

  It should be noted that the relaxation of the cell makes it pass in a horizontal configuration practically

  undistorted in the presence of any potential

  or even slightly greater than the critical potential Vc Therefore, inter-state switching can also be accomplished by lowering the potential on the cell, since

  the level of holding potential up to a slight

  higher or lower than the critical potential.

  It is advantageous for the operation of the display cell in any asymmetrical state to prevent switching of the orientation directors to a vertical configuration. Switching to a vertical configuration can be prevented by operating the variable potential source 50 below the threshold level at which detachment of disclinations occurs. It is generally found that this threshold level is in the order of 60

volts.

  In a second embodiment of the display cell, the elements and methods of operation

  essential are identical to those described above in relation to

  with the display cell shown in the figures

  1 to 7 In addition, insulation regions 202 and 212 present

  a topography in the form of inclined columns, similar to

  to the topography of the respective active region

  that surrounds each region of isolation.

  Although this is not shown in the figures

  res, an appropriate combination of polari-

  linear probes and possibly a fixed retardation plate to improve the optical contrast between the asymmetrical states. An application of this type of nematic liquid crystal display cell is in the fast memory display devices, matrix addressed Although the current addressing speeds are

  30 ms, it is clear that certain modifications

  characteristics of the display cell are able to improve the performance of this cell. These modifications include in particular the reduction of

  the spacing between the substrates and the reduction of the visco-

  of the nematic liquid crystal material.

  It goes without saying that many other modifications can be made to the device and the method described and

25347 1 6

  represented, without departing from the scope of the invention.

Claims (5)

  1 LCD display cell capable of   be switched to a first state or a second state,   taking first and second substrates arranged parallel-   to each other, and a nematic liquid crystal material having orientation directors, placed between the two substrates, characterized in that each substrate has a topographically textured interior surface, which has an inclination uniform under a   angle of inclination of acute surface compared to a normal   respective to the surface, there are means for producing a continuous potential of a first polarity on either side of the liquid crystal material} to trigger a first change in the configuration of the   guidance directors, breaking the symmetry of cell   the LCD, in order to promote a guidance director configuration in which   a reversal layer of orientation directors is practically   adjacent means and parallel to the first substrate, and there are means connected to each substrate for producing an electrical potential in the liquid crystal material, so as to complete and maintain the first change in the orientation director configuration, thereby that   guidance directors have the corresponding configuration in the first state.   Display cell according to Claim 1, characterized in that the angle of inclination of the surface for   the textured interior surface from the topographical point of view   that on the first substrate is substantially equal, and of opposite sign, to the angle of inclination of the surface for the topographic textured interior surface   on the second substrate, so that the two surfaces   Topographic textures form a border condition corresponding to inclinations equal and opposite.   3 Display cell according to any one of   claims t or 2, characterized in that each surface   topographically textured interior has an azimuthal deviation from a predetermined reference line, the topographically textured interior surface on the first substrate having an azimuth deviation, U, which is exclusively in the range of -900 to + 900, while the topographically textured interior surface on the   second substrate has an azimuth deviation of 0.   4 Display cell according to any one of   1, 2 or 3, characterized in that the means   for initiating the first change include: means for producing a continuous potential of a second polarity on either side of the crystal material   liquids to trigger a second change in the   guiding directors, by breaking the sym-   sorting the liquid crystal display cell to promote the orientation director pattern in which an orientation director inversion layer is substantially adjacent and parallel to the second substrate; and in that the means for producing an electrical potential further comprises: means connected to each substrate for producing an electric potential in the liquid crystal material, so as to complete and maintain the second change in the configuration of the   guiding directors, so that the directors of   have the configuration corresponding to the second state.   5 Method of switching a display cell   liquid crystal material comprising a liquid crystal material with orientation directors, placed between first and second substrates arranged in parallel, each substrate having a topographically textured interior surface which has a uniform inclination at an angle of inclination of acute surface compared to a   the surface normal, characterized in that   gives a continuous potential of a first polarity on both sides of the liquid crystal material, to trigger a first change in the configuration of the directors   of orientation, by breaking the symmetry of the cell of   liquid crystal display, in order to favor a configura-   orientation director in which an orientation director inversion layer is substantially adjacent and parallel to the first substrate, and an electric potential is produced in the liquid crystal material layer to complete and maintain the first change in the configuration of guidance directors, so that   the orientation directors have a corresponding configuration laying in the first state.