KR20080080017A - Method of producing electrophoretic display with organic thin transistor control circuit and electrophoretic display produced according to the method - Google Patents

Abstract

A method for manufacturing an electrophoretic display having an organic TFT control circuit and an electrophoretic display manufactured by the same are provided to simplify a manufacturing process and minimize the amount of products with defects. Plural electrophoretic display units are arranged on a common substrate. Each of the plural electrophoretic display units has cells capable of capacitive switching when performing optical development. Onto an electrophoretic display module(10), pixel electrodes(21) are applied. By directly applying an organic TFT(Thin Film Transistor) layer to a side of the electrophoretic display module supporting the pixel electrodes, an organic TFT control circuit(20) is prepared.

Description

Method of producing electrophoretic display with organic thin transistor control circuit and electrophoretic display produced according to the method

The present invention relates to a method for producing an electrophoretic display having an organic thin film transistor control circuit and an electrophoretic display produced by the method.

An electrophoretic display is a new reflective display whose image forming mechanism basically relies on changing the arrangement of colored charged particles or fluid in a dispersive or multiphase system by applying an electric field. Commercial examples include "particle systems" from E-ink and Sipix, "Liquid Powder" from Bridgestone, and "Electrowetting" from Liqua Vista. Electrophoretic displays are all capacitively controlled. That is, the electrophoretic display has a capacitively switchable cell in performing optical development. Capacitive switching of the cell is performed by the pixel electrode. When the voltage is applied to the pixel electrode, the optical development of one or a plurality of cells may be affected. In the following, electrophoretic displays having a particle system are described to explain this action. However, the present invention generally relates to all capacitively switchable electrophoretic displays and is not limited to the embodiments described below.

One electrophoretic display has a plurality of single electrophoretic displays. The single electrophoretic display has at least one cell filled with charged particles dispersed in a suitable solvent in the simplest design. Switching each cell capacitively is at least one pixel electrode designed and arranged such that the charged particles are aligned in the direction of the electric field when a voltage is applied. As such, the switching mechanism is capacitive and in the presence of an electric field the particles move in the direction of the pixel electrode and attach to it. Light is not transmitted under conditions where the coating accumulates, while light is transmitted through dispersion where particles are freely distributed. This feasible technology allows the manufacture of highly flexible displays, such as in electronic newspapers. This technology is also suitable for use in image forming parts of various electronic products such as laptops and mobile phones.

The electrophoretic display has a plurality of electrophoretic display units arranged on a common substrate. Such electrophoretic display components are hereinafter referred to as electrophoretic display modules. Pixel electrodes are applied to the electrophoretic display module. In order to control the operation of the plurality of electrophoretic display units of the electrophoretic display module, it is necessary to provide a complicated control circuit.

Small electrophoretic displays can be controlled via a so-called passive matrix. Specific pixels can be accessed by applying voltages to the rows and columns that require two conductors. This method is not suitable for large electrophoretic displays. In large electrophoretic displays, controlling the active matrix should be used. Each pixel is individually addressed through at least one of its own. As such, each single pixel has an active amplifier, for example in the form of a thin film transistor (TFT). The amplifier distributed to each pixel has two important functions. On the one hand, the control voltage of the pixel decreases as the number of used matrices of the pixel matrix increases. Thus, the size of the passive matrices is limited. However, the amplifier can increase this voltage to the value needed to switch the cell. On the other hand, a continuous increase in the number of matrices and a decrease in the pixel size lead to an increase in the parasitic capacitor of the pixel. To reach the high frame rates that are often needed, capacitors should not reduce the switching speed. Local amplifiers with independent power supplies can ensure fast switching with short, powerful current pulses.

Since the discovery and development of organic semiconductor materials, organic thin film transistors have emerged in the development of small electronic components. In its simplest form, the organic thin film transistor has a conductive gate electrode. The conductive gate electrode is covered with a dielectric thin film with an active organic semiconductor material layer attached thereto. Typically, a small number of molecules and oligomers such as pentacene and polythiophene are used as semiconductor materials. The semiconductor layer has a thickness of several ten nm and is laterally defined by the source and drain electrodes. Vertically the semiconductor layer has a size of several 100 nm. Ideally, a monocrystal may be used as the organic semiconductor material, but a polycrystalline or amorphous film may be used because it can be manufactured at a very effective cost.

Fabrication of organic thin film transistors can be realized at very cost effective, for example, in the prior art for producing fine composite structures, such as in inkjet printing. In practice regarding the fabrication of organic thin film transistors, the most important attempt to fabricate an organic semiconductor layer may be inkjet printing. Wherein the ink is selectively applied to a particular area of the substrate, the ink being composed of an organic semiconductor or in which the organic semiconductor is contained within the ink. According to the invention, the pixel electrode and further the organic thin film transistor layer is applied on the electrophoretic display module. The electrophoretic display module and the organic thin film transistor module including the pixel electrode are laminated.

Meanwhile, electrophoretic display modules can be used commercially from different manufacturers. In order to produce an electrophoretic display that can be operated immediately, an electrophoretic display module must be equipped with pixel electrodes and appropriate control circuits, especially organic thin film transistor control circuits. To this extent, the present invention uses an organic thin film transistor connected to an electrophoretic display module having an application pixel electrode through a lamination process. The organic thin film transistor module includes a plurality of organic thin film transistor units arranged on a common substrate. Both modules must be aligned with each other. This alignment establishes a desirable electrical connection between the pixel electrodes and thereby a plurality of electrophoretic display portions and organic thin film transistor portions that control their operation. In general, this requires a structure that supports the correct mutual alignment of the modules. The creation of such a structure as well as the alignment process of both modules is costly and can easily increase defective products.

There are more problems when manufacturing organic thin film transistor control circuits on independent substrate films. (1) There are always several temperature steps that lead to uncontrollable deformation and expansion of the substrate film during the process. This slightly deformed film is incorrectly combined with the electrophoretic display module, thereby reducing the quality and reproducibility of the manufacturing process. (2) When laminating both the electrophoretic display module and the organic thin film transistor module, additional pressure is required. This pressure can damage sensitive transistors.

In addition, laminating generally relates to the application of the adhesive between the modules as well as the usual heat treatment for the curing of the adhesive between the modules. On the one hand, such measures relate to the potential causes of bonding, which can increase material costs and process performance and even defective products. On the other hand, the organic semiconductor layer of the organic thin film transistor is temperature sensitive and may be limited in function by heat treatment. Therefore, there is a need for an alternative to solve the above problems of the conventional manufacturing method.

It is an object of the present invention to provide a method of manufacturing an electrophoretic display having an organic thin film transistor control circuit.

An aspect of the present invention is a method of manufacturing an electrophoretic display having an organic thin film transistor control circuit, comprising: (i) providing an electrophoretic display module having a plurality of electrophoretic display units, wherein the plurality of electrophoretic display units is a common substrate; And a capacitively switchable cell each arranged to perform optical development; (ii) applying pixel electrodes on the electrophoretic display module, wherein each pixel electrode is adapted to affect the performance of optical development of one or a plurality of cells of the electrophoretic display unit when a voltage is applied; Designed and arranged above the phoretic display module; And (iii) preparing an organic thin film transistor control circuit by directly applying an organic thin film transistor layer to a side of an electrophoretic display module supporting the pixel electrodes.

The method of the present invention does not perform lamination of the conventional electrophoretic display module and the organic thin film transistor module, thereby eliminating the drawbacks of the conventional method. The method of the present invention starts with a conventional electrophoretic display module that substantially provides a substrate for an organic thin film transistor control circuit. The pixel electrodes are applied using a known intermediate step on a commercially available electrophoretic display module. Next, an organic thin film transistor control circuit is prepared step by step by using a known method, that is, a method of sequentially forming layers, directly on the electrophoretic display module. Here, a contact necessary for the organic thin film transistor control circuit is formed between the organic thin film transistor and the pixel electrodes. According to the method of the present invention, as well as the laminating process having an intermediate step of the conventional heat treatment and the application process of the adhesive, the alignment of the electrophoretic display module and the organic thin film transistor module and the means necessary for this are no longer needed. Thus, according to the method of the present invention, the manufacture of the electrophoretic display is essentially simplified and the amount of defective product can be minimized.

Preferably, the step (iii) of preparing the organic thin film transistor control circuit in the method of the present invention comprises using organic photolithography or inkjet coating to form organic thin film transistor layers such as drain electrode, source electrode, gate electrode or organic semiconductor layer. Application. The use of such a coating method is particularly advantageous for large area electrophoretic displays in which numerous switching elements of organic thin film transistor control circuits have to be manufactured.

Another aspect of the invention is an electrophoretic display having an organic thin film transistor control circuit, comprising: an electrophoretic display module having a plurality of electrophoretic display units arranged on a substrate and having a capacitively switchable cell for performing optical development; A plurality of pixel electrodes coated on the electrophoretic display module; And an organic thin film transistor control circuit including an organic thin film transistor layer directly applied to a side of the electrophoretic display module supporting the plurality of pixel electrodes.

Preferably, in the present invention, the organic thin film transistor control circuit includes an organic thin film transistor layer having any one selected from the group consisting of a drain electrode, a source electrode, a gate electrode, and an organic semiconductor layer. The electrophoretic display of the present invention differs from the conventional structure in that a separate substrate for the organic thin film transistor control circuit is not needed and furthermore, the adhesive layer in the conventional dual module set is no longer needed. That is, in the electrophoretic display of the present invention, the layer thickness can be made thinner and the flexibility can be further increased.

The method of manufacturing the electrophoretic display of the present invention essentially simplifies the production of the electrophoretic display and can minimize the amount of defective products.

The electrophoretic display of the present invention can realize a thinner layer thickness than before and can further increase flexibility.

The invention is explained in more detail by the following examples in conjunction with the accompanying drawings.

1 shows a schematic cross-sectional view of an electrophoretic display of the invention. The electrophoretic display of the present invention includes an electrophoretic display module 10 including a substrate 12, a back plate electrode 13, an electrophoretic display unit 14, and a protective layer 15. Each electrophoretic display 14 has a cell filled with charged particles dispersed in a solvent. The backplate electrode 13 is needed to accumulate an electric field and is usually connected to ground or a constant potential. Furthermore, at least one pixel electrode is distributed to each cell, and the cells are structured and arranged such that charged particles are aligned in the direction of the electric field when voltage is applied. In general, the pixel electrodes are applied to the protective layer 15 at the time of manufacture of the display and are not illustrated in detail for the sake of simplicity because they must be structured differently according to the desired display resolution. Usually all already mentioned functional elements of electrophoretic display 14 as well as all other components available for electrophoretic display 14 have been omitted from FIG. 1 for clarity. In addition, since the image forming function of the electrophoretic display module 10 is already known, it will not be described in detail. In the present invention, at least one pixel electrode which can be switched in the above-described manner and whose operation should be controlled is distributed to each electrophoretic display 14 of the electrophoretic display module 10. For this purpose, the organic thin film transistor control circuit 20 is arranged on the side of the electrophoretic display module 10 supporting the pixel electrodes.

The organic thin film transistor control circuit 20 includes a plurality of organic thin film transistor units. Each organic thin film transistor section includes one or a plurality of organic thin film transistors. As described above, the organic thin film transistor is composed of not only an organic semiconductor layer but also layers which essentially include functional elements such as a drain, a source, and a gate electrode. One or a plurality of electrophoretic display units 14 are distributed to each organic thin film transistor unit. That is, one or a plurality of organic thin film transistors in the organic thin film transistor unit is responsible for controlling the operation of the one or the plurality of electrophoretic display units 14. To this end, at least one source or drain electrode of the organic thin film transistor of the organic thin film transistor unit is in electrical contact with the pixel electrode. The pixel electrode may extend over the plurality of electrophoretic display units 14 or only over a portion of one electrophoretic display unit 14. The display resolution determines the size of the pixel electrode. For clarity, components shown in the organic thin film transistor control circuit 20 are not shown schematically. Furthermore, since the main configuration of the organic thin film transistor control circuit 20 is well known, the detailed description of the functional elements, the description of the manufacturing and the operation mode thereof are omitted.

2 and 3 show schematic cross-sections of an electrophoretic display having a top gate and a bottom gate configuration, respectively, of the present invention. Parts having the same function are given the same reference numerals. Unlike the pixel electrode, the back plate electrode is not structured and extends over the entire electrophoretic display module.

2 shows a schematic cross section of an electrophoretic display having an organic thin film transistor control circuit 20 of the present invention, wherein the organic thin film transistors available in the organic thin film transistor control circuit 20 are electrophoretic display modules 10. ) Shows an upper gate configuration. The electrophoretic display module 10 shown in FIG. 2 is covered with a pixel electrode 21. The pixel electrode 21 may be applied using other commercial printing techniques such as photolithography, inkjet printing and screen printing.

The organic thin film transistor control circuit 20 may be formed by the following steps. Initially, the insulating layer 22 is applied onto the pixel electrode 21 by inkjet printing. In the next process step, through holes are formed in the insulating layer 22 using selective etching. Here, the through hole is filled with a material having electrical conductivity using inkjet printing to form the drain electrode 24 in contact with the source electrode 26. In parallel with this, the source electrode 26 is formed. An organic semiconductor layer 28 is then inserted between the source electrode 26 and the drain electrode 24, preferably using ink jet printing. The structure exhibited by this is then covered by another insulating layer 30. The gate electrode 32 is then applied, preferably using inkjet printing, and an appropriate protective layer 34 is applied over its ends. The insulating layer 22 is preferably formed by inkjet printing, which does not require etching. Alternatively, insulating layer 22 may be structured using photolithography. The source electrode 26 and the drain electrode 24 as well as the connecting vias are preferably formed in a single process operation using inkjet printing. Alternatively they can be formed using photolithography.

3 shows a schematic cross section of an electrophoretic display having an organic thin film transistor control circuit 20 of the present invention, wherein the organic thin film transistors available in the organic thin film transistor control circuit 20 are electrophoretic display modules 10. ) Shows a lower gate configuration. All organic thin film transistor layers can be formed similarly as described in detail with respect to FIG. 2.

By using photolithography, higher display resolutions can be achieved than with inkjet printing. For high resolution displays it is desirable to perform all the processes using photolithography, as long as the electrophoretic display allows, and then print the organic semiconductor layer 28. The gate electrode 32 can then also be printed as an alternative according to FIG. 2.

Substrate 12 of electrophoretic display module 10 may be formed from glass or a synthetic material thereof. In particular, the substrate 12 is made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), aromatic polyesters and polyimide (PI). It may be made of.

The electrodes 24, 26, 32 of the organic thin film transistor control circuit 20 as well as the pixel electrode 21 may be manufactured from a material conventionally used for electrodes. Such materials include, for example, chromium, aluminum, tantalum, molybdenum, copper, silver, gold, palladium, indium, nickel and cobalt and their alloys. Preferably some or all of the electrodes are formed of a transparent material such as indium-tin-oxide (ITO). The pixel electrode 21 is preferably made of a reflective material, for example, materials such as aluminum and silver. The backplate electrode 13 inside the electrophoretic display module 10 should be transparent.

The organic semiconductor layer 28 is a polymer such as poly (3-alkyl thiophene), poly (3-hexyl thiophene) (P3HT), poly (3-octyl thiophene), poly (2,5-thienylene vinylene): PTV or poly (paraphenylene vinylene) It may be made of a polymer such as (poly (paraphenylene vinylene): PPV). The use of molecular organic semiconductor materials such as anthracene, pentacene, hexacene or tetratracene is also possible. Furthermore, functionalized soluble pentacene materials such as triisopropylsilyl (TIPS) and triisopropylsilyl (TMS) derivatives can also be applied.

As the insulating layers 22 and 30, organic materials such as polyolefines, polyacrylates, polyimides, polystyrene and polyisobutylenes may be used. Can be. Inorganic materials such as silicon dioxide, silicon nitride, aluminum oxide tantalum oxide and the like may also be used.

INDUSTRIAL APPLICABILITY The present invention can be used for a manufacturing method of an electrophoretic display having an organic thin film transistor control circuit and an electrophoretic display manufactured by the method.

1 is a schematic cross-sectional view showing an electrophoretic display according to the present invention.

2 is a schematic cross-sectional view of an electrophoretic display having an upper gate structure of the present invention.

3 is a schematic cross-sectional view of an electrophoretic display having a lower gate structure of the present invention.

Brief description of symbols for the main parts of the drawings

10: electrophoresis display module 12: substrate

13: rear plate electrode 14: electrophoretic display

15, 34: protective layer

20: organic thin film transistor control circuit

21: pixel electrode 22: insulating layer

24: drain electrode 26: source electrode

28: organic semiconductor layer 30: insulating layer

32: gate electrode

Claims (4)

A method of manufacturing an electrophoretic display having an organic thin film transistor control circuit, (i) providing an electrophoretic display module having a plurality of electrophoretic display units, the plurality of electrophoretic display units arranged on a common substrate, each having a capacitively switchable cell in performing optical development ; (ii) applying pixel electrodes on the electrophoretic display module; And (iii) preparing an organic thin film transistor control circuit by applying an organic thin film transistor layer directly to a side of the electrophoretic display module supporting the pixel electrodes. The method of claim 1, (Iii) preparing the organic thin film transistor control circuit includes applying organic thin film transistor layers such as a drain electrode, a source electrode, a gate electrode or an organic semiconductor layer using photolithography or inkjet coating. Method for producing an electrophoretic display having a control circuit. An electrophoretic display having an organic thin film transistor control circuit, An electrophoretic display module having a plurality of electrophoretic display units arranged on a substrate and having capacitively switchable cells for performing optical development; A plurality of pixel electrodes coated on the electrophoretic display module; And An electrophoretic display having an organic thin film transistor control circuit comprising an organic thin film transistor control circuit comprising an organic thin film transistor layer applied directly to a side of the electrophoretic display module supporting the plurality of pixel electrodes. The method of claim 3, And the organic thin film transistor control circuit comprises an organic thin film transistor control circuit having any one selected from the group consisting of a drain electrode, a source electrode, a gate electrode and an organic semiconductor layer.

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