DK143525B - CELL WITH SPACES AND PROCEDURES FOR PRODUCING THE SAME - Google Patents

Description

(19) DENMARK

(12) PRESENTATION WRITING ου 143525 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 1443/75 (51) | nt.CI.3 β 02 F 1/13 (22) Filing date 4 Apr. 1975 (24) Race day Apr 4 1975 (41) Atm. available Oct 6 1975 (44) Presented 31 Aug. 198l (86) International Application No. - (86) International Filing Day - (85) Continuation Day - (62) Master Application No. -

(30) Priority 5 Apr 1974, 50199/74, IT

(71) Applicant GIORGIO BARZILAI, Rome, IT: PAOLO MALTESE, Rome, IT: CESARE

MARIA OTTAVI, Rome, IT.

(72) Invent the same.

(74) Associate Engineer Hofman-Bang & Boutard.

(54) cell with cavity and method for making the same.

The invention relates to a cell with voids of the kind set forth in claim 1.

In the known cells of this kind, there are stretched out areas where the spacers, upon exerting a compressive force, first touch the Q plate walls after the compressive force has caused some reduction of the original cavity thickness in these regions, which reduction cannot be compared. with the plane-0 error of the surfaces.

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The invention has for its object to provide a cell of the specified kind, in particular a liquid crystal cell, for which the thickness of the cavity is closely controlled, where the effect of the wave irregularities or roughness of the surface of the output support elements is decreased and the cell produced. has a high resistance to mechanical or thermal stresses that seek to change the thickness of the cell cavity.

This is achieved by a design of the type specified in claim 1.

Such a cell will, as a result of the internal stresses induced in the two support members, react to a compressive force on the support members as a cell with spaced apart spacers with the improvement that from the beginning, the wave irregularities are partially compensated and the roughness is partially smoothed, at least in the regions. for mutual contact, due to the permanently compressed state due to the internal stresses, and the cell reacts very favorably to tensile forces because the compressed state counteracts a deformation in that direction.

The invention also relates to a process for the preparation of the cell, which is characterized by the characterizing part of claim 4.

By this method, residual stresses are created in the supporting cell of the finished cell, maintaining the support members in a compressed state, which in turn contributes to smoothing the roughness of the contact areas (spacers and peripheral edges) between the two support bodies and to equalize the surfaces of the wave surfaces. These tensions are then the same that oppose the pulling forces that affect the cell.

The invention is further explained below in connection with the drawing, in which: FIG. 1 and 2 are schematic depictions of the two plate-shaped support bodies of the cell according to the invention, before and after their compression and closure, respectively. 3 is a voltage / stretch diagram of the cell according to the invention; FIG. 4 and 5 are views of a modified embodiment of a cell according to the invention, similar to FIG. 1 and 2, and FIG. 6 and 7 cross-section through other embodiments of the cell of the invention.

FIG. 1 shows a cell with two support plates 10 and 11, usually of glass. In the plate 10, corresponding to the surface intended to face the second plate 11, a cavity 12 is designed to accommodate the liquid crystal, and in which cavity also spacers 13 and a peripheral bridge are provided. 14 extending along the entire circumference of the cavity. Both the cavity 12 and the evenly spaced B1 pieces 13 are made by photogravings as known in the prior art to form a layer of desired shape and size with the tolerability obtainable by such a method.

As shown in FIG. 1, the plates 10 and 11 used as starting bodies are curved in cylindrical form and arranged with the convex surfaces facing each other.

When the manufacture of the individual plates is completed, the plates are placed against each other by approaching the divergent edges to one another under appropriate pressure until both the plates have become flat, and at this working step, make an edge weld 30 to form the one shown in FIG. 2.

The FIG. 3, the voltage / stretch curve shown for the active regions of the cell is obtained by applying two equal and oppositely directed forces F (Fig. 2) perpendicular to the surfaces and measuring the reduction L of the thickness of the cavity, for example by interferometric volume measurement. .

A characteristic feature of such curves is that for small deformations, the ratio of the deformation and the tension is that which corresponds to a structure in which the two support members are bonded to each other corresponding to the spacers and weld seams, whereas this ratio is sufficient for sufficient forces. the pull direction is similar to a structure where the two support members are bonded to each other only at the weld seams. All of the deformations mentioned are elastic and reversible.

In this connection, a plausible explanation for the behavior of the cell of the invention is to be a distribution of the internal voltages as assumed in FIG. 2nd

In the embodiment of FIG. 2, the weld seam 30 is subjected to the inner corner of the edge of the plates 10 and 11, which may be mechanically perceived as a hinge, to tensile forces 15 of the plates which would in a free state seek to assume the one shown in FIG. 1 convex shape. The outermost material layers of the sheets are stretched while the inner layers in contact with the cavity are shrunk. Corresponding to the spacers 13, there is a compressive force 16 acting between the one and the other plate, the resultant of which is equal to and opposite to the tensile forces 15.

A characteristic feature of the cell as shown in FIG. 1 and 2, the preferred embodiment shown is that by breaking the tight closure, the two plates seek to resume their original curvature. FIG.

4 and 5 show a change in which the output plates 10 and 11 have a spherical curvature, with the output plates being assigned the desired radius of curvature, taking into account the areas of tolerance of vital importance. It has been found appropriate to start with flat glass sheets of the desired quality, i.e. plates whose roughness and surface wave irregularities lie within an area which does not subsequently affect the thickness of the cavity. Therefore, according to the methods known from glass technology, the plate is assigned a spherical curvature with a radius of curvature of at least 5 m, preferably between 20 m and 80 m. After or before the assignment of the curvature, a prescribed number of spacers 13 is provided by conventional methods.

Then the plates with the convex surfaces facing each other are pressed together and sealed along the edges as for the one shown in FIG.

1 and 2.

In the embodiment of FIG. 6, the edge welding with the aid of a material 17 can be mechanically compared to a rigidly clamped end, and the middle surface of the plates would not change if the plates were released. The surface of the edge, on the other hand, would seek to assume the shape shown in a dashed line. This is in contrast to the previous embodiments that the outer layers of the plates of the material 17 are subjected to a compression 18 while the inner layer is subjected to a traction 19. The elastic response of the plates 10 and 11 produces compressive forces 20 at the spacers and counteracting forces 21 along the edges.

Also for the construction of FIG. 7, the middle surfaces of the plates 10 and 11 will, if released; do not change their shape. The plates are welded together at material layers 22 and are provided with grooves filled with a material 23 so that compressive forces 24 are exerted on the outer layers of the plates.

As a result, compressive forces 26 are induced at the spacers and compensating forces 25 and 27.

For the preparation of the cell according to the invention, support bodies having at least two surfaces facing each other are provided, and a suitable number of spacers are provided, or a plurality of cavities of the desired depth can be etched on one or more of the surfaces. if a variable thickness of the cavity is desired, these cavities (especially in the case where their width is large in relation to the thickness of the thin support body) can accommodate protruding teeth which act as spacers.

Then the surfaces are brought against each other by subjecting them to a compressive or tensile force adapted to the shape of the output surfaces so that the support members are deformed elastically and the surfaces can touch each other through the spacers. Then, the edges and possible other prescribed locations are welded so that, upon cessation of the applied forces, the surfaces remain in contact with each other through the spacers and that inside the support members and weld seams remain tensions which create a compressed state of the interconnected surfaces upon effect. 6 143525 of the distance pieces. Such weld seams also close the cavity.

Alternatively, the necessary internal stresses in the structure may be applied in whole or in part after or during the welding of the two support members by a plastic cross-cutting of all or part of the material of which the support members are made, since this cross-cutting is caused by the mechanical or thermal stresses. which are imprinted on these materials.

The supporting bodies used shall consist of materials such as glass having such mechanical properties that they can be subjected to stress while maintaining the internal stresses in operation and compatible with a suitable life of the cell without undergoing any additional deformation, breakage or other weakening during the cell's service life.

The spacers may also consist of different materials of such thickness, deformation capacity and arrangement as to obtain the prescribed cavity. For example, they can be made by spreading glass beads of the same diameter on at least one surface, but they can also be obtained by covering in the material of the support body a few areas from which no material is to be removed and performing the etching on the covered surface by an appropriate method. In all cases, it has been found that in order to obtain voids having a thickness of less than 5 micrometers, the distribution of the spacers must be such that no point in the void is more than 4 mm from a spacer or from the circumference of the void.

Holes for filling the cell can be drilled into the cell wall surfaces, or channels can be recessed, etc.

The FIG. 2 can be prepared as follows:

The starting material is flat glass sheets with a thickness of 3 mm and whose facing surfaces have wave irregularities of the order of 1 micrometer and so that curves of below one and every cross-sectional line of the surface occur.

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0.1 µm / cm. The sheets measuring 10 x 10 cm are subjected to such treatment that they assume a curvature of 1 µm / cm, which is almost uniform as it is much larger than the curves due to the initial wave irregularities present.

On the convex surface of each plate, a cavity of size 9 x 9 cm and a depth of 3 microns and with bridges is projected from the bottom of the cavity and at a height corresponding to the depth of the cavity of cylindrical configuration with a diameter of 0.1 mm and placed in the nodes of a theoretical grid of size 1 x 1 mm located in the interior of the cavity.

Then, on the convex surfaces, electrically and chemically active thin layers can be deposited by methods which do not provide further deformation in the glass to give the layers the desired profile.

Then the two convex surfaces abut each other, and by applying a uniform compressive force of 1 kg / cm all the spacers are brought into contact.

A small amount of resin is made to seep from the edges to the interior and brought to complete polymerization to prevent any subsequent shear.

Upon cessation of the pressure exerted on the plates, the inner surfaces are parallel within 0.2 microns as determined by interference figures from monochromatic sodium light.

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The same result can be achieved by applying a pressure of 2 kg / cm before and after the adhesive step, limited to a 5 mm wide strip along the entire circumference of the cell.

The FIG. 2 can also be made by repeating the above operations except for the glass vault, but for adhesive instead of a plastic material using a stirred glass mass having a melting point of about 10%. 550 ° C.

During the thermal circuit required for welding the glass, the cell is subjected to pressure on the entire surface and at the same time pressure which seeks to shrink the outer layers of the plates. These forces are obtained by placing the outer cell surfaces between two metal blocks which are aligned, rigid and have a larger coefficient of expansion than the glass. The blocks are pressed against the plates at a temperature of 570 ° C and cooled to 440 ° C while maintaining the cell under a pressure of 2 kg / cm. This provides a plastic creep of the sheet glass which, upon cooling, induces the internal stresses of FIG. 2 and the same thickness uniformity of the cavity as in the previously described embodiment.

The FIG. 6 can be obtained as follows:

The output support bodies are flat plates having the same thickness and surface properties as in the preceding embodiments.

Plates with a dimension of 53 x 73 cm are cut and one plate is provided with a cavity of 50 x 70 cm with a depth of 3 microns and with bridges in the nodes of an ideal grid of 5 mm as in the previous cases.

Any required thin layers are deposited on the plates without causing any deformation.

A 3 micron deep layer of resin is deposited on one plate as a strip with a width of 1.5 cm both along the edges and to form a grid with 10 cm long sides over the entire plate surface, except for certain interruptions of the strips, so that the 10 x 10 cm fields into which the plate surface is thus divided are interconnected.

The plates are pressed against each other and compressed under a pressure of 2 kg / cm while the plastic material completely polymerises.

The cell thus obtained is not uniform at the cessation of the pressure, as only a few spacers touch each other.

Then, U-shaped grooves are cut into the outer surfaces of both plates by means of a diamond grinding wheel in the welding areas, which grooves have a depth of 1.2 mm and a width of 1 mm.

9 143525 In the grooves an aluminum wire is pressed, whose intrinsic tension is such that it produces it in FIG. 7 shows a system of stresses and an even thickness of the cavity within 0.1 microns over the entire surface.

The construction of FIG. 5 can preferably be obtained by starting from plates with a spherical curvature. The starting material is flat glass sheets with a thickness of 3 mm and a size of 68 x 35.5 mm.

On the surface of one plate, a central cavity of 58 x 20 mm is formed by photogravure with a depth of 3 microns and with bridges extending from the bottom of the cavity and a height equal to the depth of the cavity of a cylindrical shape with a diameter of 0.05 mm, placed in the nodes of an ideal grid of 2 x 2 mm located within the cavity. The plates thus treated are subjected to such heat treatment as to produce a spherical curvature corresponding to a radius of 51 m.

Thereafter, electrically and chemically active thin layers are deposited on the convex surfaces without deforming the glass, thus obtaining the desired profiles of the layers.

The plates are brought against each other by applying uniform pressure along the edges until the spacers come into contact and the resin caused to seep from the edges towards the interior at a prescribed distance is brought to polymerization.

Upon cessation of the pressure on the two plates, the inner surfaces remain parallel within a tolerance of 0.1 to 0.6 microns as confirmed by the interference figures by monochromatic yellow sodium light.

Claims (4)

Patent Claims: A cell with voids, comprising at least one set of planar support members welded along the edges, and between opposite surfaces forming a cavity for receiving a liquid crystal, in which voids a plurality of spacers of the same thickness as the cavity in a prescribed pattern between the facing surfaces of the two support bodies, characterized in that internal stresses are developed in the support bodies so that the facing faces of the bodies are kept compressed to contact each other over the spacers. A cell according to claim 1, characterized in that the biasing results from the support bodies having been subjected to a chromium and arranged with their convex surfaces facing each other to define a cavity of the form as a negative lens before being compressed and welded along edges. Cell according to claim 1, characterized in that grooves are provided in the outer surfaces of the two support bodies and that a material is pressed and stored in the grooves to induce the internal prestresses. A method of producing a cavity cell according to claim 1, wherein two supporting bodies are first disposed with facing surfaces to define a cavity in which spacers are placed in a predetermined pattern, after which the edges of the two support bodies are welded, characterized by in that the two support bodies are internally prestressed so that their facing surfaces are compressed for contact with each other over the spacers.