DE2159165C3 - Method of manufacturing a liquid crystal cell - Google Patents

Description

The invention relates to a method for producing a liquid crystal cell, in which two plates from inorganic material, of which at least one is transparent, while fixing their distance parallel be arranged to each other, in which the space between the plates with a liquid crystal is filled, and in which this gap compared to the outer space at the edge zones is sealed.

Under a liquid-crisiallzcllc one provides cmc controllable light barrier or a controllable reflector, in which the / wipe melting and Clear point occurring special properties of crystalline, d. H. exploited anisotropic liquids will. When using the light barrier, all plates and thin-film electrodes must be transparent be, in the implementation as a reflector you need transparent plates and thin-film electnides at least one reflective thin-film electrode, the carrier plate of which is opaque can be.

For liquid crystal / ellcn one uses before mainly nematic crystalline liquids and, as controlling parameters, preferably electric fields For practical use it is necessary to have relatively thin layers of the between plates to form crystalline liquid whose thickness is in the Order of magnitude from 10 ° to O-? [im, especially from 5 up to 30 μιτι is Fs is already known (DE-OS 18 14 619). to keep the plates at a fixed distance and to seal the gap. So far one is so vorgcg.m gen. dal! between plates made of transparent material, especially made of glass, depending on the requirement with transparent or reflective thin-film electrodes were covered, .in the pl.i'enr.ind stripes or a partially interrupted sequence from a Has arranged slide. whose thickness corresponded to the clear distance. Mainly as a film material Polyhoxafluorathylcn for seeding / After filling the crystalline liquid, the / hurry with a Sealed epoxy resin. Hey this embodiment allows the distance to be constant at some distance from the edge, especially with pressure loads. to To be desired This means that the production is more extensive Liquid crises made difficult, if not impossible. Furthermore, the service life is about 10 hours relatively low.

For the development of multiple glazing units, a process has become known (ATPS 2 84 361) in which the panels are shrunk to form a web at the edge and a watering hole is provided in one panel in at least one corner of the unit, which is finally sealed tightly. Multiple glazing units produced in this way cannot be used for liquid crystal cells, since the fusion necessary for their production

process the thin-film electrodes would be destroyed and the required narrow clearance would not or not can be produced with the required tolerance.

From US-PS 34 99 167 it has become known to maintain a gas discharge display cell an even distance between the glass plates at certain points between the plates To attach small glass beads that form a single layer with a correspondingly large spacing of the beads form. The pei'.en are attached to very specific individual points and melted there. The production of liquid crystal cells by such a method would be extremely expensive and expensive.

The object of the invention is to provide the simplest possible and to propose a cost-saving method of manufacturing liquid crystal cells.

The object is achieved by first placing grains of a selected grain fraction on the first plate by means of sieving. Sprinkling or screen printing can be applied so that the grains form a single layer in which the mean distance between the grains is at least ten times as large as the minimum grain size. and that on the first plate covered by the grains the / wide plate is placed, whereupon the panels are tightly connected to one another.

The main result of this is that a large number of grains are applied in a randomly distributed manner will.

Apart from the fact that the largely statistically distributed grains now ensure a constant spacing of the panels is reached over the entire surface, much thinner tarpaulins can be used what means material and space savings. The production of large-area liquid crystal cells is much easier.

If plates covered with thin-film electrodes are used, the grains must of course be made of insulating material.

Although i, ian are mostly nematic in practice crystalline liquids or mixtures with a nematic :! crystalline liquid as the main component for liquid crystal / cells are used, so are all other grades and mixtures, provided that they only have anisotropic behavior / inherent, applicable.

Be / üglicl, the narrowness of the Korrspektnims need no extreme demands are made. In practice it has been found to be sufficient To use grain fractions, the limits of which at a upper grain sizes of less than or equal to 25 μm not more than 6 μm and with an upper grain size / e of more jls 25 μπι not more than 25% of the upper Grain boundaries differ from each other. Such grain fractions can be found, for example, by sieving out with Sieve fabrics obtained according to DIN 4188, whereby one step can even be skipped, for example Grains from 25 μm to 32 μm clear mesh size or from 28 μm to 36 μm clear mesh size. There are Comminution processes are also known in which a narrow grain range is obtained without sieves, for example by means of a jet mill, which is used with advantage especially for grain sizes below 25 μm. Even by means of a wired sifter, a can niäil be useful Achieve edges grain spectrum.

The tolerance with respect to the grain size can be large because of the connection of the edge zones by means of hot pressure welding, the body

. • η

ner, which are pressed into the panels in the edge zones, if there are any, and in the rest of the panel area partly penetrate into the panels, partly be pressed flat, which increases the clear distance by a lot sets closer tolerance. It is also possible through Appropriate choice of material consciously strive for penetration or only flat pressure. When connecting the Plates without heating, the narrow tolerance of the clearance is achieved by initially only the grains lying at the upper grain boundary are clamped and it is thus possible to use the to remove the rest, for example by vibration.

The number of filling or ventilation openings can be up to a single opening per liquid crystal layer be reduced if the air between the distanced plates before filling the crystalline Liquid is evacuated, making use of a three-way stopcock. The closure the filling or ventilation openings can be in a known Way without disadvantages by means of an epoxy resin, since the area that mi the crystalline Liquid comes into contact with what is smaller than with the conventional designs and this contact also takes place on a "dead arm". Of the Closure can, however, also take place by welding or melting, with the "dead arm" again being the Protects the bulk of the crystalline liquid.

Since the grains cover a maximum of about one percent in terms of area, it is useful for many purposes. e.g. for neon letters, k'.a role if the grains are made of opaque material. However, the grains can be optically if necessary sufficient to make them disappear if they are made of a transparent material that at least has approximately the same index of refraction as the crystalline liquid. It is also without Significant loss of strength possible, individual, not / u large areas of the liquid crystal / elle of Keep grains free. In order to cut out these areas, it is advisable to use the help of Masks, screen printing stencils or the like.

Due to the fact that now much thinner plates can be used without impairing the stability, it is more easily possible to use liquid / istall cells to be formed in several layers, d. That is, a plurality of plates forming a stack are provided, in which Interstices / wipe the plates are arranged crystalline liquid. These separate layers crystalline liquid can advantageously consist of different crystalline liquids or with crystalline liquids doped with various foreign substances exist. The configuration of the thin-film electrocJen can differ from layer to layer.

After laying the desired number of panels with interposed Jen Korrilagen the entire stack is heated under the application of pressure. Vents hermetically connected and finally preserved, whereupon the crystalline Liquid is filled in and the filling or ventilation openings are hermetically sealed.

The production of curved liquid crystal cells is also possible in the embodiment according to the invention in FIG easily possible. Since the stack of plates is spaced over its surface by means of the grains, after connecting the plates by heating and then letting it cool down in one

IO

r>

20th

suitable shape are curved without the exact distancing is lost.

The one produced by the method according to the invention Liquid crystal cell can also be used as a screen, for example for an oscilloscope or a Television receiver, are used, wherein a known device for generating the Image grid is provided. For training as a screen of a color television receiver are expedient as many layers of crystalline liquid doped with the appropriate dyes are provided, are used as the basic colors to build up the color image.

If there is a compared to the panel material The lower 15-hour relaxation temperature of the grain material is advantageously the entire stack is heated to a temperature greater than the 15-hour relaxation temperature of the Körtieiwcikiiüffes. but less than the 5 hour release temperature of the panel material, the grains on the clear distance to be produced are compressed to produce an adhesive surface contact with the panels.

The 15-hour relaxation temperature is the substance-specific temperature at which the the respective substance is completely tension-free after 15 hours of heating.

If the 15-hour relaxation temperature is the same or higher than that of the panel material of the grain material, the entire stack is expediently heated to a temperature which exceeds the 15-hour relaxation temperature of the panel material. The plates When heated, they are pressed more strongly against one another and connected to one another over parts of their edges (Hot pressure welding).

The manufacturing method according to the invention offers the advantage above all, with relatively little Effort to be rationalizable.

The subject of the invention is described below with reference to the drawing, which relates to three exemplary embodiments relates, explained in more detail.

The F i g. 1 to 5 show one according to the invention Process produced liquid crystal cell with the plates practically completely covering thin- « layer electrodes, namely

F i g. 1 shows a section along the line I-I in FIG. 2, F i g. 2 a plan view,

3 shows an enlarged oblique view through a partially broken open part of the liquid crystal cell,

4 shows a detail on a further enlarged scale and

5 shows another possible embodiment of this Details. the

Figures 6 to 9 show various examples Training opportunities for thin-film electrodes; Fig. 10 shows a section through a multilayer Liquid crystal cell and

F i g. 11 is a section through a curved liquid crystal cell.

The in the Fi g. 1 to 5 shown liquid crystal cell consists of two on the inside practically entirely with thin-film electrodes 11,12 covered glass plates 1, 2, between which a single layer of Grains 3 is arranged from insulating material, through which the iicht distance between the flats is determined. The grains 3 are drawn to their clarity and better representation because of excessive

40 edge zones 4 ₍ 5, Θ, 7, the glass plates are hermetically connected to one another by hot pressure welding, which means the use of heat and pressure. In this case, filling and ventilation openings 8, 9 are cut out at two corners, for example in the case of hot pressure welding at the point of the openings 8, 9 to be made, wires made of a material with greater thermal expansion coefficients than the glass plate material, such as copper, are inserted, which can be easily pulled out after cooling; whereby the desired openings 8, 9 arise. One of these openings 8 becomes nematic crystalline The air can escape through the other opening 9. The openings 8, 9 are closed by means of epoxy resins 13, 14, with only very small contact surfaces of the oxide resin 13. 14 with the crystalline liquid 10. also on a "dead Ann ", appear. The number of openings 8, 9 is of course neither limited to two, nor do they have to be arranged diagonally opposite one another in the corners, but the embodiment shown has proven to be particularly practical. The openings 8, 9 can also be closed by welding or melting. When a voltage is applied to the thin-film electrodes 11, the previously translucent nematic crystalline liquid wedge 10 becomes opaque in a known manner, the degree of switch-off depending on the field strength. That's why it matters so much. to maintain the distance between the plates 1, 2 exactly over the entire surface, for which purpose the grains 3 are used according to the invention. The control can also take place by means of a magnetic field, in which case the thin-film electrodes 11, 12 can be dispensed with.

If a transparent material is selected for the grains 3, which has at least approximately the same refractive index like the crystalline liquid 10. the grains 3 are practically invisible, which is why they also in Fig. 2 are not shown.

In order to explain the invention clearly, m

- - - ·. , · .. ι ... t — 1-5: _i: - «" ιΐ ^ -, ιι-.

f I g- J CHI A \ US3l.niiUt dUS UCI t iu3 »5m idimii.i.iiv

shown enlarged in an oblique view. A part of the glass plate 1 and the thin-film electrode 11 were thereby used broken away. The distance between the plates 1, 2 is actually 10 ° to ΙΟ ^ μπι. with one realized Embodiment 20 μm, the thickness of the thin-film electrodes 11, 12 is of the order of magnitude 0.5 μm. It can be seen that the mean distance of the Grains 3 the grain size substantially, at least ten times larger, whereby the grain size of the grains 3 Required space a maximum of about one percent of the remaining space of the crystalline liquid 10 matters. Although the grains 3 therefore only take up little space and also optically disappear can be brought, they cause a decided improvement in the strength of the cell and the about the area of uniform spacing of the glass plates 1, 2. The thickness of the glass plates 1, 2 can be compared to the known designs are reduced, what the use of liquid crystal cells expanded.

Another advantage of the invention is that the surface quality of the glass plates 1, 2 is no longer so high demands must be made, as with the previous versions.

F i g. 4 and 5 show a greatly enlarged detail

From Fig. 1 two possible embodiments of the Distan-Zierurig tier glass plates Ij 2 through the grains 3. In the embodiment according to Fig.4, the körtierwerkstoff softens before the plate work. In the design according to Fig. 5, the plate material softens before the center ΐ material. These two AusführUngsmöglichkeiteri should be seen as extremes between which there are smooth transitions. If, for example, glass plates if 2 and grains 3 are made of the same glass, the result is a penetration of the grains 3 into the glass plates 1, 2 similar to that in FIG. 5, although not as pronounced, because the temperature of the grains 3 at F. The last-mentioned version offers the best strength results. The grains 3 can lie on the thin-film electrodes 11, 12 as shown in FIGS ), whereby you can press the bünnschicht-1-.lektrode 12 also clunis into the plate (Fig. 5). But you can also cut through the thin-film electrodes 11, 12, as shown in each case for plate I (thin-film electrode II).

Since the liquid crystal cell is designed sturdy chemically and thermally highly resistant material and hermetically sealed, it is thus suitable without further 2 ^r> protective measures for crystalline liquids verschiedenster Art. Alongside those with the anisotropy region at room temperature for those with higher and lower lying anisotropy region.

As mentioned, in the embodiment of a liquid crystal cell that can be controlled by electrical fields jo it is necessary to cover the inside of the glass plates 1, 2 in a known manner with thin-film electrodes 11, 12. Such transparent thin-film electrodes 11, 12 are produced, for example, from tin oxide or indium oxide. reflective z. B. made of aluminum. One covered the entire plate surface with thin film electrodes 11, 12 so it receives to an electrically controllable light barrier or an electrically controllable reflector einfachster Art. The edge zones 4,6 is only one thin film Elektnode 11, 12 according to anRpn apiiihrl u / ia 7 RP i η 1 fr »i- AIa Γ \ Γ · ήη« - / * Κ! / ιΙ> * nioL ·

- ο ■ - "- σ" - ■ "- * - " ~ - '—... "· ** ■». »* ■« ■ · ~ -.— ..

trode 12 at the edge zone 6 shows. At the edge zones 5, 7 small thin-film electrodes 11, 12 are applied.

It is known by designing the thin-film electrodes 11, 12 in the most varied of configurations possible to display different characters, for example numbers and letters, in a controlled manner.

The F i g. 6 to 9 show known exemplary embodiments for this purpose. The in F i g. 6 shown in plan view Glass plate 15 carries, for example, a thin-film electrode configuration 16, 17, 18, 19, 20, 21, 22, such as it is common for a seven segment digit display. The in F i g. 7 illustrated glass plate 23 is also covered with a thin-film electrode 24, which is used as a counter-electrode for the in F i g. 6 shown serve can.

8 and 9 show further examples of thin-film electrode configurations that are frequently used in practice. The in F i g. The glass plate 25 shown in FIG. 8 has vertically running tracks of thin-film electrodes 26a to 26g, which in P i g. 9 illustrated glass plate 27 on horizontally extending tracks of thin-film electrodes 28a to 28g. If the glass plates covered with the strips of thin-film electrodes 26, 28 are used to form a liquid crystal cell according to FIGS Horizontal · And Veflikälelekfrode 26,28 are connected to voltage.

10 shows a section through a multilayer, and in particular a three-layer liquid crystal cell. Four glass plates 29, 30, 31, 32 are each spaced apart by a single layer of grains 3 and attached the edge zones 31, 34 connected to one another by means of glass solder 35. For the purpose of filling crystalline liquid in the gaps are expediently similar to FIG. 2 at two opposite corners per layer 36, 37, 38 two filling or venting openings 8, 9 are provided, with the openings 8.9 of the middle Layer advantageously offset diagonally over those of the first and third layers. The openings can by leaving a gap when applying the amount of solder glass, which is expediently done by means of screen printing takes place, are produced. Each layer 36, 37, 38 of crystalline liquid is three-dimensional from the rest completely separated. It is also possible to use transparent thin-film electrodes insulated from one another on top and underside of the glass plates 30, 31 to attach - the glass plates 29,32 only need on their respective Inside thin-film electrodes -. so that also with regard to the electrical control a complete Separation is possible. Thus, each layer 36, 37, 38 of crystalline liquid can be seen to be completely different from the rest independent and can therefore also consist of different or with different foreign substances, for example Dyes, doped crystalline liquids are made. The practical application of a multilayer Liquid crystal cell is by the possibility, according to the invention, the glass plates 29, 30, 31, 32 without To make a loss of robustness thin is much easier, if not made possible in the first place.

7u / pplfc ÄttcKtMtincr rlot- Ρ | ίίο <: Ϊ € τ1 ^ τ * ί ^ α11-7 £> 1] £ »ale RiIrI.

The glass plates have a screen in a known manner, similar to the glass plates 25, 27 in FIGS. 8 and 9 Thin-film electrodes 26, 28. A screen for a color television receiving set is functionally similar 10, the thin-film electrodes also being similar to FIG. 8 and 9 are arranged.

It is now possible to manufacture curved liquid crystal cells with little effort. F i g. 11th shows a section through a curved liquid crystal cell. It is initially exactly like that in FIGS. 1 and 2 shown constructed. After or at the same time with the hot pressure welding, the already distanced from the grains 3 glass plates 39, 40 in a form made of a material that is not wetted by glass, for example graphite or boron nitride, placed on what by heating in the transformation area of the glass used for the glass plates 39, 40, the Deform glass plates 39,40 in the desired way, soft shape is retained after cooling. First then the crystalline liquid 10 is filled.

For this purpose 2 sheets of drawings

Claims (9)

Patent claims: 1. A method for producing a liquid crystal cell, in which two plates made of inorganic ϊ material, at least one of which is transparent, are arranged parallel to one another while fixing their distance, in which the space between the plates is filled with a liquid crystal, and in which this The intermediate space is sealed against the outer space at the edge zones, characterized in that first of all grains (3) of a selected grain fraction are applied to the first plate (2,32) by means of sieving, scattering or the screen printing process in such a way that the grains form a single layer form, in which the mean distance between the grains is at least ten times as large as the mean grain size, and that on the first plate covered with grains (2, 32) the / wide> n plate (I ₁ 31) is placed, whereupon the Plates with each other you; get connected. 2. A method for producing a liquid crystal cell according to claim 1, characterized in that the limits of the grain fraction of the grains (3) applied to the first>> plate (2, 32) at an upper grain limit of less than or equal to 25 μιτι not more than 6 μιτι and with an upper grain boundary of more than 25 μπι not more than 25% of the upper grain boundary differ from one another. in 3. The method according to claim I or 2. characterized in that after laying the desired number of plates (32, 39, 29) mn intermediate 'grain layers of the entire stack heated under pressure. d.'at the edge / o r> nen (4, 5, 6, 7, 33, 34) with the omission of filling b / w. Vent openings (8,9) hermetically connected and is finally brought to cool whereupon the crystalline liquid (10, 36, 37) is filled and the filling b / w. Air vents (8, 9) hermetically sealed. 4 Method according to one of Claims 1 to 3. characterized in that if a mt is present, compared to the panel material is lower 15 hour relaxation temperature of the grain r. factory the entire stack is heated to a temperature that is greater than the 15-hour ent chipming temperature of the grain material, depending but smaller than the 15-hour relaxation time perauir of the lath material. the grains (3) in are pressed together to the clear distance to be produced, producing an adhesive Area consumption on the plates. 5 Method according to one of Claims 1 to 4. characterized in that the plates (29, 30, 31,., 32) at least over parts of their edges (33, 34) itiiltels (ilaslotes (35) are hermetically connected (Fig. 10). 6 The method according to claim 5, characterized draws that the Glaslotmcnge by means of screen printing mi is applied. 7. The method according to any one of claims I to 3, characterized by the fact that if there is a material that is the same as the material or higher lS ^ levels ^ EnispännUflgSternperälUr des fi5 Grain material the entire stack on one Temperature is heated, which the 15-Slünden-EntspännliflgstempefätüT of the plate material over * increases. 8. The method according to claim 7, characterized in that the plates (1, 2,39,40) over parts of their Edges more pressed together when heated and be connected to each other. 9. The method according to any one of claims I to 8, characterized in that the plates (39,40) at be curved from heating.