RU2226293C2 - Display panel and multilayer plate for its manufacture - Google Patents

Abstract

FIELD: information displaying equipment. SUBSTANCE: multilayer plate contains optically transparent substrate, protective layer, currentconducting layer and at least one layer of anisotropic film crystal. Film crystal is formed by substance which includes aromatic rings and shows Bragg reflex

Description

The present invention relates to devices for displaying information, in particular to display elements.

Traditionally, the display is made in the form of a flat cuvette formed by two plane-parallel plates, on the inner surfaces of which an electrode system is formed from an optically transparent electrically conductive material (for example, SnO ₂ and I ₂ O ₃ - ITO solid solution). The surface of the plates with electrodes is usually covered with a layer of polyimide or another polymer and subjected to special treatment, which provides a given uniform orientation of the liquid crystal molecules (LC) at the surface of the plates and in the volume of the LCD layer in the display. After assembling the cuvette, it is filled with an LC, which forms a layer with a thickness of 5-20 μm. LC is an active medium that changes its optical properties under the influence of an electric field. The change in optical properties is recorded in crossed polarizers, which are usually glued on the outside of the cell [L.K. Vistin. ZhVHO, 1983, volume XXVII, issue 2, p.141-148].

In industry, a display panel is made of plates having a glass substrate and a conductive layer. Glass plates should have good flatness and not have bubbles and other optical defects. Depending on the operating conditions of the display, a blank with different conductive layers is used. For displays operating in the light, conductive layers are transparent. For displays operating on reflection, the front panel of the display is made of a plate with a transparent conductive layer, and the back is made of a plate with a reflective conductive layer. [A.A. Groshev, V. B. Sergeev. LCD-based information display devices. - L: Energy, 1977]. Transparent conductive layers have a surface resistance of 10 to 10 ² ohms and a transmittance of 0.7-0.9 in the visible region of the spectrum. Conductive layers are formed by precipitation methods.

Typically, a panel of display panels is formed on each panel. The required electrode configuration for each display panel is performed by mask etching. The electrodes go to the edge of the glass, where they end with a contact pad, for soldering the external terminals. The panels are separated by etched tracks along which the display will be glued. To create the necessary gap between the panels, spacer strips are placed along their perimeter. The assembled panel (or panel matrix) is filled in an LCD vacuum with heated plates. This achieves a decrease in viscosity and better filling of the gap. Then the display in the matrix is separated from each other (scribe and break) and each cell is sealed. Outside, polarizers containing a protective layer on the surface are pasted onto the display and / or covered with a glass plate.

To prevent ion diffusion from the glass into the LCD during the display operation, a protective layer is usually formed between the glass and the conductive layer. Typically, the protective layer is a film of silicon oxide or heavy metal oxides, but some polymers can be used. The protective layer should be transparent in the working region of the spectrum, and its thickness and density should ensure reliable insulation of the glass from the LCD.

There is a wide variety of methods for producing protective coatings: physical methods based on the evaporation or atomization of the material, or chemical methods based on the use of chemical reactions [N.P. Gvozdeva et al. Physical optics. - M.: Mechanical Engineering, 1991, p. 178 and 179]. Currently, the most common is evaporation in a vacuum. The method consists in the thermal evaporation of the required material in a deep vacuum. The resulting pairs condense in the form of a thin film on the surface of the substrate. The process is fast - from a few seconds to several minutes.

Another physical method is cathodic sputtering. The process is based on knocking out atoms of the cathode material during its bombardment by high-energy rarefied gas ions. Atoms escaping from the cathode surface are deposited on the substrate. During reactive cathodic sputtering, an active gas (for example, oxygen) is introduced into the working chamber, which helps to obtain films of the desired chemical composition.

Chemical methods include, for example, the method of forming films from solutions of hydrolyzable compounds. In this case, a silicon oxide film is formed by depositing a solution of silica ether on a centrifuge rotating in a workpiece.

US Pat. No. 5,358,739, 1994 describes a method for forming a silica coating by applying a silazane polymer to a substrate and then heating it in an oxidizing medium. There are also other methods.

From the literature [WO 94/28073] a polarizer is known which is obtained on the basis of liquid crystalline solutions of organic dyes. The polarizer according to this technology is made by applying a thin film of an LCD dye solution to a glass or polymer substrate using one of the known methods. A feature of the technology is that the orientation of the dye molecules occurs during the deposition of the film, so that immediately after it dries on the substrate, a thin heat-resistant polarizing coating is obtained. Their application allows us to create new designs of liquid crystal displays in which polarizers can be formed directly on the walls of the LCD cell, both on its external and internal sides. The internal arrangement of polarizers is more preferable, since it allows to increase the strength and reliability of the display, as well as to simplify its design and reduce the number of technological operations.

With the appropriate choice of application conditions and the magnitude of the orienting effect, it is possible to obtain a dichroic polarizer containing an anisotropic film, at least a part that has a crystalline structure [PCT RU 99/00400]. Such dichroic polarizers have a higher degree of anisotropy and thermal stability.

In a display with an internal polarizer, a dichroic polarizer is usually formed above the electrode system [RU 2139559]. To do this, the electrodes are coated with a special planarizing layer, which also contributes to good adhesion of the dichroic polarizer material. This leads to an increase in the number of layers in the display (its thickness) and the number of technological operations during production. In addition, in this case, a dichroic polarizer can be applied only after the formation of the electrode system, which reduces the flexibility of production to change the range of products.

The present invention is directed to the creation of a multilayer plate that can be used in the manufacture of displays, as well as to the design of the display with an internal polarizer.

The technical result of the claimed invention is to increase reliability and reduce the thickness of the display, as well as reduce production costs, increase yield, reduce the number of operations during assembly of the display.

вдоль одной из оптических осей. По крайней мере один слой пленочного кристалла расположен между подложкой и электропроводящим слоем и отделен от последнего защитным слоем. Вещество пленочного кристалла может содержать гетероциклы.The technical result is achieved in that the multilayer plate contains an optically transparent substrate, a protective layer, an electrically conductive layer, at least one layer of an anisotropic film crystal. The film crystal is formed by a substance that contains aromatic rings and has a Bragg reflex (3.4 ± 0.2)

along one of the optical axes. At least one layer of the film crystal is located between the substrate and the electrically conductive layer and is separated from the latter by a protective layer. The substance of the film crystal may contain heterocycles.

The substrate of the multilayer plate may be made of glass, and the protective layer may be made of silicon oxide and / or oxide (s) of heavy metal (s), or polymer (s). The electrically conductive layer is usually made of ITO.

Sometimes a metal mesh can be applied to the ITO layer (for example, by means of mask spraying) in order to increase the conductivity of the layer. Moreover, the total surface area of the metal mesh should be less than 10% of the total surface of the multilayer plate.

Typically, a film crystal is an E-type polarizer. Sometimes a film crystal can simultaneously serve as a polarizer and a phase-holding layer.

Sometimes at least part of the protective layer can be conductive (for example, by doping the surface).

When transporting in order to prevent damage, it is preferable to additionally cover the multilayer plate with polymer (s) film (s).

вдоль одной из оптических осей. При этом по крайней мере один слой пленочного кристалла расположен между подложкой и системой электродов слоем и отделен от последнего защитным слоем. Вещество пленочного кристалла может содержать гетероциклы. Подложка панели дисплея может быть выполнена из стекла. Защитный слой может быть выполнен из оксида кремния, и/или оксида(-ов) тяжелых(-ого) металлов(-а), или полимера(-ов). Система электродов обычно выполнена из ITO.In addition, the claimed technical result is achieved in that the display panel contains an optically transparent substrate, a protective layer, an electrode system and at least one layer of a film crystal. The film crystal is formed by a substance that contains aromatic rings and has a Bragg reflex (3.4 ± 0.2)

along one of the optical axes. At the same time, at least one layer of the film crystal is located between the substrate and the electrode system by a layer and is separated from the latter by a protective layer. The substance of the film crystal may contain heterocycles. The backing of the display panel may be made of glass. The protective layer may be made of silicon oxide and / or oxide (s) of heavy metal (s), or polymer (s). The electrode system is usually made of ITO.

A metal mesh can be applied to the ITO layer in the display panel. In this case, the total surface area of the metal mesh should be less than 10% of the total area of the electrodes.

In a display, a film crystal is usually an E-type polarizer. Sometimes a film crystal in a display can combine the functions of a polarizer and a phase-holding layer.

Additionally, the display panel may contain adhesive (s) layer (s).

вдоль одной из оптических осей; сверху наносится защитный слой, например слой оксида кремния, и затем проводящий слой, обычно ITO.The laminated plate according to the claimed invention contains the following main layers: an optically transparent substrate, usually sodium-calcium glass (soda-lime glass); optically anisotropic layer - a film crystal formed by a substance containing aromatic rings and having a Bragg reflex (3.4 ± 0.2)

along one of the optical axes; a protective layer is applied on top, for example a silicon oxide layer, and then a conductive layer, usually ITO.

The optically anisotropic layer will perform the functions of a polarizer in the display or, at the same time, the functions of a polarizer and a phase-holding layer. It is necessary that said layer be at least partially crystalline, this will ensure high stability of its structure and the required optical parameters. The initial choice of material for the formation of such a layer is determined by the presence of a developed system of π-conjugated bonds in aromatic cycles and the presence in the molecules of groups such as amine, phenolic, ketone, etc., lying in the plane of the molecule and which are part of the aromatic bond system. The molecules themselves or their fragments have a flat structure. For example, it can be organic substances such as indantrone (Vat Blue 4), or dibenzoimidazole 1,4,5,8-naphthalene tetracarboxylic acid (Vat Red 14), or dibenzoimidazole 3,4,9,10-perylenetetracarboxylic acid, or quinacridone (Pigment Violet 19) and others whose derivatives or mixtures thereof form a stable lyotropic liquid crystal phase.

When such an organic compound is dissolved in a suitable solvent, a colloidal system (lyotropic liquid crystal) is formed in which the molecules are combined into supramolecular complexes, which are kinetic units of the system. LC is a pre-ordered state of the system from which an anisotropic crystalline film (or in other terms, a film crystal) is formed during the orientation of supramolecular complexes and subsequent removal of the solvent.

A method for producing film crystals from a colloidal system with supramolecular complexes provides

applying this colloidal system to a substrate; the colloidal system must also have the property of thixotropy, for this the colloidal system must be at a given temperature and have a certain concentration of the dispersed phase;

bringing the applied or applied colloidal system to a state of increased fluidity by any kind of external action, which provides a decrease in the viscosity of the system (this can be heating, shear deformation, etc.); external influence can continue during the entire subsequent orientation process or take the time necessary for the system to not have time to relax into a state with increased viscosity during the orientation time;

external orienting effect on the system, which can be produced both mechanically and in any other way; the degree of this effect should be sufficient so that the kinetic units of the colloidal system receive the necessary orientation and form a structure that will form the basis of the future crystal lattice of the resulting layer;

the transfer of the oriented region of the obtained layer from a state with a reduced viscosity, which was achieved by the initial external influence, into a state with an initial or higher viscosity of the system; it is carried out in such a way that there is no disorientation of the structure of the formed layer and there are no defects on the surface of the layer;

the next operation is the drying operation (removal of solvent), during which the formation of a crystalline structure occurs directly;

usually the final operation is the conversion of the film crystal into a water-insoluble form by treating its surface with a solution containing 2- and 3-valent metal ions.

In the resulting layer, the planes of the molecules are parallel to each other, and the molecules form a three-dimensional crystal at least in part of the layer. When optimizing the production method, it is possible to obtain a single crystal layer. The optical axis in such a film crystal will be perpendicular to the plane of the molecules. Such a film crystal will have a high degree of anisotropy and a high refractive index for at least one direction.

). Во влажном слое молекулы имеют дальний порядок по крайней мере в одном направлении, что связано с ориентацией супрамолекулярных комплексов на подложке. При испарении растворителя молекулам, оказывается, энергетически выгодно образовать трехмерную кристаллическую структуру.To obtain layers with the required optical characteristics, colloidal systems can be mixed (in this case, joint supramolecular complexes will form in the solution). In the layers obtained from mixtures of colloidal solutions, absorption and refraction can take different values within the limits determined by the starting components. Mixing of various colloidal systems with the formation of joint supramolecular complexes is possible due to the coincidence of one of the sizes of the molecules of the above organic compounds (3.4

) In the wet layer, molecules have a long-range order in at least one direction, which is associated with the orientation of supramolecular complexes on the substrate. When the solvent evaporates, it turns out to be energetically beneficial for the molecules to form a three-dimensional crystalline structure.

The thickness control of the layer is carried out by the solids content in the applied solution and the thickness of the wet layer on the substrate. The technological parameter in the formation of such layers is the concentration of the solution, which is convenient to control during production. The degree of crystallinity of the layer can be controlled by x-ray or optical methods.

A distinctive feature of the film crystal is its high thermal stability, which is especially important with modern display technology.

A silicon oxide layer is necessary to protect the anisotropic layer from damaging external influences in the process, in particular during the ITO etching operation and isolating it during operation of the display from contact with electrodes and LCDs. A silicon oxide layer is formed by known methods: evaporation in vacuum during heating, cathodic atomization, the so-called “wet method”, from solutions, etc. The protective layer, in addition to silicon oxide, may also contain heavy metal oxides. For example, the CERAMATE composition for forming the protective layer from the solution contains up to 6 wt.% Of the solid phase (TiO ₂ , ZrO ₂ , SiO ₂ , Sb ₂ O ₅ ). The layer obtained from the solution is usually sintered at elevated temperature. This operation in the production of multilayer plates is possible due to the high thermal stability of the anisotropic layer. It can withstand heating up to 180 ° C or short-term heating up to 250 ° C and higher without significant changes in optical characteristics.

Various thermally stable and chemically stable polymers can also be used as a protective layer. The thermal stability of all layers of a multilayer plate is necessary, since a number of technological operations in the production of a display (for example, the formation of a planarizing and orienting polyimide layer on an electrode system) include high-temperature heating.

The conductive layer (ITO) is formed by one of the known methods.

Also, the multilayer plate may contain additional outer layers that protect it during transportation and are removed during the manufacture of the display.

Such a multilayer plate is a blank for the production of display panels and already contains the main functional layers of the display. This allows us to simplify the manufacturing technology of displays, reducing the number of production operations.

The dimensions of a multilayer plate are determined by the requirements of display manufacturers. Usually on each plate fits several display panels. On the plate for each display panel, a corresponding electrode system is formed, and tracks are formed along which the displays will be glued together. The removal of the material of the conductive layer in the corresponding sections of the plate can be carried out by photolithography, laser ablation, etc.

The density and thickness of the protective layer should be sufficient so that during photolithography or other similar methods of etching the conductive layer, the anisotropic film crystal is not destroyed.

When laser ablation is used in places where tracks for gluing the LCD cells are formed, glass with a protective layer of silicon oxide can sinter simultaneously with the removal of the conductive layer.

Then, the electrode system is usually covered with a layer of polyimide, which acts as a planarizing and orienting LCD layer. Other materials can be used as the planarizing layer, in particular silicon oxide. In this case, the layer material will additionally play the role of an insulator, preventing breakdown between the electrodes.

After the matrix of the front and rear display panels is formed, the corresponding plates are glued together and the resulting cells fill the LCD. Then there is a separation of the LCD displays. Formed LCD displays have internal polarizers. This allows us to simplify the design of the display, reduce its thickness and increase reliability in operation.

The display panel may contain several layers of an anisotropic film crystal, while one of the layers can act as a polarizer and the other as a retarder (phase-holding layer). As is known, the use of phase-shifting layers in displays, for example, of the STN type, leads to an increase in the viewing angle and a decrease in chromatic aberrations of the image.

As a material for the phase-retaining layer, aromatic compounds are selected that are not absorbing or have weak absorption in the visible spectrum and are capable of forming a stable lyotropic liquid crystal phase. Such a film crystal will have a high degree of anisotropy and, for one direction, a high refractive index.

The layers of the anisotropic film crystal can be separated by an intermediate protective layer or applied directly to each other. In the latter case, the lower layer must first be converted into a water-insoluble form by treating its surface with a solution containing 2- and 3-valent metal ions.

The invention is illustrated by the following drawings: figure 1 shows a diagram of a multilayer plate according to the claimed invention; figure 2 presents a diagram of an LCD display with internal polarizers.

The laminated plate in one embodiment (FIG. 1) comprises an optically transparent substrate 1 of sodium-calcium glass; polarizer 2, which is a film crystal formed from a 9.5% aqueous solution of sulfonated indantrone. The thickness of the polarizer is about 100 nm. A silica protective layer 3 and then a conductive layer 4, usually ITO, are applied on top. During transportation, the plate is usually protected from above with polymer films 5.

Such a multilayer plate is a blank for the production of display panels and already contains the main functional layers of the display. One possible construction of such a display with internal polarizers is shown in FIG. 2. The display is a flat cuvette formed by two parallel glass plates 6, on the inner surfaces of which a polarizer layer 2, a protective layer 3 of silicon oxide, an electrode system 7 of optically transparent electrically conductive material (ITO), and a polyimide layer 8 are orientated layer. After assembly of the cell, it is filled with a liquid crystal 9 and sealed, for example, with sealant 10.

The design of the display with an internal polarizer allows to reduce the thickness of the device and increase its reliability during operation. In addition, the optical properties of film crystals used as anisotropic layers in such displays make it possible to create devices with high contrast and a wide viewing angle.

Claims (21)

1. A multilayer plate containing an optically transparent substrate, a protective layer, an electrically conductive layer and at least one layer of an anisotropic film crystal, the substance of which contains aromatic rings and having a Bragg reflection (3.4 ± 0.2) Å along one of the optical axes, and at least one layer of the film crystal is located between the substrate and the electrically conductive layer and is separated from the latter by a protective layer. 2. The multilayer plate according to claim 1, characterized in that the substance of the film crystal contains heterocycles. 3. A multilayer plate according to claims 1 and 2, characterized in that the substrate is made of glass. 4. A multilayer plate according to any one of claims 1 to 3, characterized in that the protective layer is made of silicon oxide and / or at least one heavy metal oxide, or at least one polymer. 5. A multilayer plate according to any one of claims 1 to 4, characterized in that the electrically conductive layer is made of ITO. 6. A multilayer plate according to claim 5, characterized in that a metal mesh is applied to the ITO layer. 7. The multilayer plate according to claim 6, characterized in that the total surface area of the metal mesh is less than 10% of the total surface of the multilayer plate. 8. A multilayer plate according to any one of claims 1 to 7, characterized in that the film crystal is an E-type polarizer. 9. A multilayer plate according to any one of claims 1 to 8, characterized in that the film crystal is both a polarizer and a phase-holding layer. 10. The multilayer plate according to claim 1, characterized in that at least part of the protective layer is conductive. 11. A multilayer plate according to any one of claims 1 to 10, characterized in that the multilayer plate is additionally coated with a polymer film or polymer films. 12. A display panel containing an optically transparent substrate, a protective layer, an electrode system, and at least one layer of an anisotropic film crystal, the substance of which contains aromatic rings and having a Bragg reflection (3.4 ± 0.2) Å along one of the optical axes, and at least one layer of the film crystal is located between the substrate and the electrode system and is separated from the latter by a protective layer. 13. The display panel according to claim 11, characterized in that the substance of the film crystal contains heterocycles. 14. The display panel according to claims 11 and 12, characterized in that the substrate is made of glass. 15. The display panel according to any one of paragraphs.11-13, characterized in that the protective layer is made of silicon oxide and / or at least one heavy metal oxide or at least one polymer. 16. The display panel according to any one of paragraphs.11-14, characterized in that the electrode system is made of ITO. 17. The display panel according to claim 15, characterized in that a metal mesh is applied to the ITO layer. 18. The display panel according to clause 16, characterized in that the total surface area of the metal mesh is less than 10% of the total area of the electrodes. 19. The display panel according to any one of paragraphs.11-17, characterized in that the film crystal is an E-type polarizer. 20. The display panel according to any one of paragraphs.11-18, characterized in that the film crystal combines the functions of a polarizer and a phase-holding layer. 21. The display panel according to any one of paragraphs.11-19, characterized in that the display panel further comprises an adhesive layer or adhesive layers.

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