FR2577693A1 - Process for manufacturing a liquid-crystal cell - Google Patents

Abstract

The present invention relates to a process for manufacturing a liquid-crystal cell. This process is characterised in that, while one or more plane cells 10, having a gap in which the liquid-crystal material 5 is sealed, are held under pressure in such a way that the gap can be made uniform over the entire zone in question, the opening 6 provided for the injection of the liquid-crystal material 5 is sealed in a leaktight manner.

Description

The present invention relates to a method of manufacturing

  cation of a liquid crystal cell in which. in particular, the glass substrates constituting an element to

  linuid crystals are designed to be uniformA-

ment plans.

  In a conventional liquid crystal cell

  n the two glass substrates are arranged in layers having a uniform interval between them and they are sealed

  by means of adhesives, at their periphery, the material has

  liquid rates being housed inside. Ti is preferred

  rable that the interval between the two aforementioned glass substrates are uniform throughout the area of the element

  because if this interval is not uniform, a contrast appears

  appears in the liquid crystal display and this contrast

  causes a lack of uniformity in the display and the fran-

  qes. To avoid these phenomena, the methods illustrated in FIGS. 7 (a), (b), (c), (d) have already been adopted as

  that methods of making a liquid crystal cell

2n quides.

  In other words, grains 3 are sprayed for controlling the interval over the entire surface of a glass substrate 2 and the adhesives 4 are applied, including

  grains 3, using printing methods

  notch or others, and this at the periphery, except at the place of an opening 6 provided for the injection of the liquid crystal material 5. nn then applies the other substrate

  in glass J on the previous one, we maintain the two subs-

  trats by means of a pressing frame 7 and a single piece 30.l4ment is formed with the cell in the form of a plaster, by curing the adhesives 4 under the effect of heat and under pressure. fn then injects the liquid crystal material into the internal space, through the opening 6, and finally the linear crystal cell is obtained by sealing it

by means of a waterproof adhesive 6a.

  In this manufacturing process the grains 3 are provided in the interval between the two glass substrates l and 2 in order to maintain, as it has been indicated? prec,; demim, a uniformity of this interval throughout the area where the liquid crystal material 5 is injected. Consequently, when the glass substrates are applied under pressure against each other by means of the pressing frame 7, the deformations of the glass substrates 1 and 2 are corrected and the interval becomes uniform.

  throughout the affected area. However, when this pres-

  zion is suppressed, recovery forces are concentrated

  trent in the center, because the w5 peripheries of the glass substrates 1 and 2 are fixed by means of the adhesive 4, and these forces again cause deformation at the places where the degrees of freedom of the glass substrates 1 and 2 are the

higher.

  As described above, it is impossible

  ble, with the conventional method, to maintain uniform the interval between the substrates throughout the area and by

  therefore the liquid crystal cell that we

  holds, presents a contrast in the display and

  so much so that you cannot get a sharp display.

  In particular, this phenomenon appears in a remarkable way.

  ble in liquid crystal cells of large dimensions

  sions and the problem of reduced manufacturing yield

cation persists.

  The object of the present invention is to resolve the

  aforementioned problems and relates to a manufacturing process

  cation of a liquid crystal element in which the opening provided for the injection of the liquid is sealed under pressure conditions such as naked i'intervaiie between

  substrates is kept uniform in any location.

  An embodiment of the present invention will be described below, by way of non-limiting example, with reference to the appended drawing in which: Figure 1 is an elevation view of a planar cell. Figure 2 is an elevation view of a frame

  of pressane from flat cells kept under pressure.

  Figure 3 is a side view of the frame of

Figure 2.

  Figure 4 is an elevational view of a belt.

  plane on which a shock absorbing material is placed.

  shock. Figure 5 is a block diagram of an apparatus

  injection of a liquid crystal material.

  Figure 6 is a comparative data diagram.

  which relate to the process according to the invention and

1i0 to conventional methods.

  Figures 7 (a), (b), (c), (d) are diagrams il-

  polishing the various phases of the conventional process.

  According to the invention the crystal material iiaui-

  is sealed under conditions such as subs-

  glass trats are kept under pressure, and so even

  after the pressure condition is removed, the subs-

  glass trats are kept in correct condition by atmospheric pressure so that a

  uniform display area over the entire area concerned.

  2 9 In the process according to the invention, the part of the

  process in which grains 3 are provided for the con-

  distance between the glass substrates I and 2

  and we form, by means of the adhesive 4 and the qrains 3, the

  vertex for the injection of the liquid crystal material, is ia same as in the case of the method described above and illustrated in FIGS. 7 (a), (b), (c), (d). In other words the glass substrates 1 and 2 are arranged in layers and the flat cell in is produced in one piece as well

  that it is illustrated in the figure].

  tion of the transparent electrodes which are necessary to obtain an element? liquid crystals and the necessary orientation treatment are applied to the substrates in

  glass 1 and 2 nar well known means and which by cons "-

  These will not be described in detail at this time.

  The flat cells 10 as illustrated on the

  Figure 1, are arranged one on top of the other, more

  sinnches, as shown in Figure 2.

  and the correction of the pian cells] n is carried out by training them by means of the pressing frame 11. Thus nu'ii

  has been explained previously ia the press phase is slowed down

  sée, during the manufacturing process of flat cells 1], to prevent a deformation from appearing, after the pressure has disappeared, at the location of the free face portion which is not fixed by means of the adhesives. Thanks to the correction phase by means of the press mount 11. the glass substrates 1 and 2 constitute a planar cell 10 whose pianity is corrected so as to have a uniform interval between the substrates as long as the pressure

  is maintained. The pressing frame It includes a plate

  ne upper lia, a lower plate 11b and an orqane

  stop stop which keeps the flat cells ln under pressure

  if we. The role of the arresting body] lc is to maintain the pres-

  sion exerted by a press on the upper face of the

upper plate lla.

  During the correction phase of the flat cells 10i by means of the pressing frame 11, the layers 12 of shock absorbing material are placed on the faces

  upper and lower plane cells ln. nn use-

  preferably reads as a shock absorbing material

  shock, a flat rubber plate that is placed by my-

  to cover the entire surface except the opening provided for the injection of the liquid crystal material

  in the flat cell 10 (see figure 4).

  The liquid crystal material 5 can be injected

  ted before the correction of the planar cell 10 by means of the press mount II but it can also be injected while this planar cell is kept under 3n pressure by the press mount 11. In the first case,

  that is, when the liquid crystal material 5 replaces

  folds the cell Jf beforehand, the interval is kept uniform throughout the area of the cell as a result of the correction pressure exerted on this flat cell 10 and

  while this pressure is maintained, the saddle is opened

  ture 6 using adhesive 6a. Then, after the removal of the press mount i] l, the cell 10 is maintained

  in the correct conditinn under the effect of the pressure at-

  mosphrinue and we can thus obtain a cell h cris-

  linuid rates with a uniform interval over its entire extent. In the second aforementioned case we place the cell

  plane 1n in a vacuum enclosure 13, with a view to 1'in.jec-

  tion of the liquid crystal material 5 (see the figure) while the planar cell In is maintained under pressure by means of the pressing mount II. After put under

  vacuum of the enclosure by means of a vacuum pump] 4. wave-

  place a support 16 for a 1.5 container upwards

  1R holding the liquid crystal material, we connect the

  conduits mites 17 of the container 15 containing the liquid crystal material at each opening 6 of the cells

  planes 10 and then the pressure inside the enclosure

  te sous vide 13 is restored to a value close to the

  atmospheric ion, by introducing nitrogen gas 18. From

  this way the liquid crystal material 5 is injected

  t in the interval between the substrates of each cell

  plane In, practically under vacuum, through a conduit 17.

  Once this injection is complete, the flat cell is 2n out of the enclosure while being kept under pressure by the pressing frame 11, and the opening 6 is sealed with a waterproof adhesive 6a, after which the cell

  liquid crystal is obtained after removal of the mon-

pressure 11.

  As described above, the deformations of glass substrates 1 and 2 can be corrected by one or

  the other of two different injection methods of the material

re liquid crystal 5.

  When opening 6 sceiiemPnt by means of

  the waterproof adhesive 6a, the flat cell] 0 must be natural-

  iement kept under pressure until the adhesive 6a has been hardened. However, if the pressure is reduced slightly before the adhesive is fully cured, a small amount of adhesive 6a enters the opening 6, this

  which makes sealing even more reliable.

  Figure 6 illustrates the comparison between the varia-

  tion of the interplay between the substrate of a cell

  linuildes nr product rate- according to the invention and a cei-

  iule obtained with the conventional process. The green lines

  thin ticals, in the form of a T, represent the variation obtained with the conventional process, while the thick vertical lines, in the form of an I, illustrate the variation obtained with the process according to the invention. Ii clearly results from this fioure that the intervals at the neighboring places of the adhesives 4 are almost the same but that on the other hand in a position remote from the ends, position where the degree of freedom is high; the difference between

  ln intervals can be of the order of 3 h 4 times and the

  tition of the intervals is not uniform in the case where the

  cell is obtained by the conventional method.

  As described above, in the process according to the invention the planar cell is pressurized and it is sealed in a sealed manner while being kept under pressure, after which the application of the pressure and therefore the flat cell can be kept in the state where any deformation has been corrected

  and we can thus obtain a uniform interval on the to-

  29 the surface of a liquid crystal display device. According to the invention, the fact that one can obtain

  a liquid crystal cell having a single interval

  formed on the entire liquid crystal display surface, the quality of the display is improved. In other words, no contrast and no fringe appear in

  the display and furthermore there is no difference in the responses

his.

  Consequently, this process has proven to be quite narti-

  efficient processing for the production of h cells

  liquid crystals having a relative display area-

  large and for the liquid crystal cells of the

type h dot matrix.

-7

Claims (4)

RESENDTrATTnNS   1.- Procedure for manufacturing a liquid crystal cell, characterized in that, while maintaining   under pressure one or more flat cells (10) taken   as a gap in which the liquid crystal material (5) is sealed, so that the gap can be made uniform over the entire area concerned, the opening (6 ) scheduled for   injection of the liquid crystal material (5).   2.- Method according to claim 1 characterized in that layers (12) of a shock absorbing material are provided on the upper and lower faces of the planar cell (10), during the correction phase of   the deformation of the planar cell (10) by means of a pressing structure (11).   3.- Process according to any one of the claims.   tions above characterized in that the liquid crystal material (5) is injected into the planar cell (10) before the cell deformation correction phase by means of the pressing frame (11) or else the liquid crystal material (5) in the planar cell (10) while this planar cell (10) is held under   pressure by means of the pressing frame (11).   4.- Process according to any one of the claims   previous tions characterized in that we decrease   pressure before the adhesive (4) is completely hard-   ci, when the opening (6) of the planar cell (ln) is   secured using a waterproof adhesive (h).