JP2661057B2 - Electrochromic display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochromic display device capable of controlling a coloring state reversibly by heat and an electric field. [Summary of the Invention] The present invention is reversible by heat and an electric field by laminating a color-decoloring material that colors and decolors by an electrochemical oxidation-reduction reaction and an electrolyte layer whose electric conductivity increases by heating. The coloring state can be controlled and there is little crosstalk.
It is an object of the present invention to provide a novel electrochromic display device capable of displaying a large area and a high resolution. Furthermore, the present invention, by applying a plurality of coloring and decoloring materials that emit and decolor to different colors in a predetermined pattern,
It is an object of the present invention to provide an electrochromic display device capable of color display. [Prior art] For example, in the field of various display devices, the purpose is to reduce the size of the device and increase the degree of freedom of installation location, etc.
Development of a flat so-called flat display has been advanced, and as one of them, an electrochromic display device (so-called ECD) using an electrochromic material as a display material has been proposed. This electrochromic display device uses a voltage (current)
Utilizes a reversible color change that occurs in an electrochromic material due to an oxidation-reduction reaction caused by application, and is expected to be a high-quality display device, as it is much better in viewability than a liquid crystal using a polarizing plate. . By the way, as a conventional electrochromic display device, an electrochromic material is a solution-soluble type in which an electrochromic material is dissolved in an electrolyte solution, or an ionic conductor such that a current flows when a necessary potential for causing an oxidation-reduction reaction is applied. A thin film type in which a certain electrolyte layer (for example, a propylene carbonate solution of lithium perchlorate or β-alumina) is provided in contact with an electrochromic thin film is known. And
These electrochromic display devices employ a configuration in which display is performed only by controlling current, and operate as a current-type element. However, in an electrochromic display device that performs display only by the above-described current control, for example, when an attempt is made to perform display driving with an electrode having a simple XY matrix structure, color development of unnecessary portions due to current leakage or the like due to a current-type element is caused. Inevitably, non-selected points are colored and the resolution is reduced. Regarding the display memory state (display state with the external voltage turned off), in a device that controls only the current, if the off-resistance of the IC in the external circuit is small, the color density gradually decreases, etc. Is seen to decrease. Alternatively, particularly in a solution-dissolution type device or a thin film type device using an electrolyte in a solution state, it is necessary to give due consideration to liquid leakage, and the structure tends to be complicated. Furthermore, in a conventional current control type electrochromic display device, it is difficult to selectively recolor only a predetermined portion in the same cell that is not electrically insulated to perform partial rewriting, much less a simple matrix structure. In reality, it is almost impossible to realize multi-color display such as multi-color display and full-color display using electrodes. [Problems to be Solved by the Invention] Therefore, the present invention has been proposed in view of the above-described conventional situation, and there is no crosstalk even with a simple matrix, and large-area display and high-resolution display are possible. An object is to provide an electrochromic display device. Further, the present invention provides an electrochromic display device capable of performing full-color display, capable of performing color erasing and erasing of a plurality of colors such as RGB (three primary colors of an additive color method) and YMC (three primary colors of a subtractive color method). Aim. [Means for Solving the Problems] The present inventors have conducted intensive studies with the achievement of the above-mentioned object, and as a result, provided an electrolyte layer whose electric conductivity increases by heating in contact with the electrochromic layer. For example, by heating the electrolyte layer, it is possible to cause an electrode reaction that induces an oxidation-reduction reaction of the electrochromic layer. Therefore, the coloring state is controlled by both heat and an electric field, and simple matrix driving causes crosstalk. This has led to the finding that there is no such problem, and that the electrochromic layer can be colored separately by making the electrochromic layer solid. The electrochromic display device of the present invention has been completed based on such findings, and is different from each other due to an electrochemical oxidation-reduction reaction, and has at least red, green, and a plurality of color erasures that emit and eradicate blue. A solid organic electrochromic layer in which the material is applied in a predetermined pattern, an electrolyte that contains a supporting electrolyte, changes in solid-liquid state by heating and cooling, and increases in electrical conductivity when heated and melted, and electrodes are formed on both electrodes. Is formed, the organic electrochromic substance that emits red color is 2,4,7-trinitro-
9-Fluorenone is used, and 2,4,7-trinitro-9-fluorenylidene malononitrile is used as the organic electrochromic substance that develops green color.
The present invention is characterized in that tetracyanoquinodimethane is used as the organic electrochromic substance that emits blue light. These electrochromic materials may be used alone as an electrochromic layer. For example, a multicolor electrochromic material such as a combination of red, blue, green or yellow, magenta, cyan, etc. is selected, and a matrix-like, stripe-like material is used. Alternatively, they may be formed in different shapes. In this case, full-color display, multi-color display, and the like can be performed. On the other hand, the electrolyte layer is made of a material whose electrical conductivity increases by heating, and plays a role of securing conductivity when heated and promoting the oxidation-reduction reaction of the electrochromic layer. Therefore, as the electrolyte layer, for example, a material in which a supporting electrolyte is dispersed in an insulating medium which undergoes a phase transition by heat and is solid at room temperature is used. In the above case, the supporting electrolyte may be an aliphatic quaternary ammonium salt such as tetra-n-butylammonium tetrafluoroborate, tetra-n-butylammonium perchlorate, cetyltrimethylammonium bromide, dioctadecyldimethylammonium chloride, or myristyl. Benzalkonium salts such as dimethylbenzylammonium chloride, benzyldimethyl [2- [2-p-1,
[1,3,3-tetramethylbutylphenoxy) ethoxy] ethyl] benzedonium chlorides such as ammonium chloride, alkylpyridinium salts, imidazolinium salts, lithium perchlorate, lithium borofluoride and the like can be used. In addition, an ionic surfactant such as an anionic surfactant can be used as the supporting electrolyte. Examples of the anionic surfactant include carboxylic acid salts such as aliphatic soap, sodium palmitate, potassium stearate, and alkyl ether carboxylic acid; alkyl benzene sulfonates such as sodium lauryl benzene sulfonate; and sodium naphthalene sulfonate. Sulfonates represented by alkyl naphthalene sulfonates, sodium naphthalene sulfonate / formalin condensates, dialkoxy sulfosuccinates, etc., alkyl sulfates, alkyl ether sulfates, polyoxyethylene alkyl ether sulfates, alkyls Examples thereof include sulfates represented by phenyl ether sulfate and the like, and phosphates represented by alkyl phosphate and alkyl ether phosphates. The insulating medium is required to dissolve the supporting electrolyte and to change solid-liquid by heating and cooling.
Polyacrylates, polymethacrylates, polyacrylamides and the like, homopolymers or copolymers thereof, ethylene carbonate, N-methylacetamide,
Sulfolane or the like can be used. Among them, a high molecular weight compound having a long-chain alkyl in the side chain is preferable. For these polymers, higher molecular weights can be obtained by polymerizing higher fatty acid esters of acrylic acid or methacrylic acid alone or linearly in the presence of other monomers, for example, by a method such as radical polymerization or radical copolymerization. Can be synthesized. Alternatively, liquid crystalline polymer materials such as a cyanobiphenyl polymer, a copolymer of cyanophenylbenzoate and methoxybiphenylbenzoate, a phenylbenzoate / azomethine polymer, and an azomethine polymer can be used. Since the concentration of the supporting electrolyte in the insulating medium needs to be completely dissolved in the insulating medium to be used, the upper limit is naturally the solubility limit. The lower limit is the lowest concentration that provides conductivity sufficient for performing oxidation-reduction of the electrochromic layer at the electrode. In the case where the above-mentioned supporting electrolyte itself shows a solid-liquid change, it is not always necessary to use this insulating medium, and the supporting electrolyte alone may constitute the electrolyte layer. In the electrochromic display device of the present invention,
The method utilizes the fact that an electrochemical oxidation-reduction reaction of the electrochromic layer occurs by applying a current when the above-mentioned electrolyte layer is heated, and the color is developed and erased. Therefore, images and characters can be displayed by combining the heating electrode and the current application electrode. Various combinations are adopted as the combination of the heating electrode and the current application electrode. For example, electrodes for applying a current may be provided on both sides of the display unit including the electrochromic layer and the electrolyte layer, and the display unit may be selectively heated by a thermal head while the entire surface is energized. Alternatively, an electrode for heating the entire surface of the display portion and an electrode for selectively applying a current to the display portion may be provided. As the electrode for heating the entire surface of the display unit, an electrode may be literally formed on one surface of the display unit, and an AC bias may be applied thereto.
On the other hand, as an electrode for selectively applying a current to the display unit,
For example, a driving element such as a TFT (Thin Film Transistor) may be provided for each pixel. In this case, if the display section is heated by the entire surface heating electrode and a predetermined electric signal is supplied to the selective current applying electrode, images, characters, and the like are displayed according to the electric signal. Further, a heating electrode to which an AC bias is applied, and a current application electrode for applying a DC current with the heating electrode as a counter electrode are disposed on both surfaces of the display unit so as to form a simple XY matrix. Is also good. In this case, the display section is colored only at the intersection of the heating electrode and the current application electrode. [Operation] In the electrochromic display device of the present invention, the electrolyte layer shows conductivity only when heated, and therefore, the electrochromic layer undergoes an electrochemical oxidation-reduction reaction when both heating and current application are completed. An image, a character, or the like is displayed indicating the coloring / erasing behavior. Here, if the electrochromic layer is separately coated with a combination of red, blue, green or yellow, magenta, cyan, and the like, full-color display is achieved by individually driving these colors. EXAMPLES Hereinafter, specific examples of the present invention will be described with reference to the drawings. Example 1 In this example, full-color display is enabled by separately applying electrochromic layers. First, as shown in FIG. 1, a transparent electrode (3) made of, for example, ITO (Indium Tin Oxide) is provided on the entire surface of one glass substrate (1), and an electrochromic layer (5) is further formed thereon. Formed. As shown in FIG. 3, the electrochromic layer (5) is separately coated with an electrochromic material that emits three colors of RGB. In FIG. 3, R, G, and B represent deposited films of electrochromic materials for red, green, and blue. The electrochromic layer (5) having the above-mentioned pattern is formed by successively applying a mask vapor deposition method. In this example, 2,4,7-trinitro-9-fluorenone was used as the red electrochromic material, and 2,4,7-trinitro-9 was used as the green electrochromic material.
-Fluorenylidene malononitrile as tetracyanoquinodimethane (TCNQ) as an electroluminescent material for blue color
Was used. The molecular structure of each electrochromic material is shown below. 2,4,7-trinitro-9-fluorenone 2,4,7-trinitro-9-fluorenylidenemalononitrile Tetracyanoquinodimethane The deposition conditions and film thickness of each electrochromic material are as follows. Vacuum degree Evaporation rate Film thickness Red: 5 × 10 ^-5 Torr 5Å / sec 1300Å Green: 5 × 10 ^-5 Torr 5Å / sec 1500Å Blue: 5 × 10 ^-5 Torr 5Å / sec 800Å Deposition is performed by resistance heating and resistance Power supply voltage for heating is 10
V, the current was in the range of 5 to 25 A. On the other hand, the glass substrate (2) prepared separately also has ITO
A transparent electrode (4) consisting of
Myristyldimethylbenzylammonium chloride (melting point 51 ° C), which was heated to 60 ° C to be in a solution state, was applied by spin coating, and cooled to form an electrolyte layer (6). Next, the glass substrate (1) on which the transparent electrode (3) and the electrochromic layer (5) are adhered and formed, and the glass substrate (2) on which the transparent electrode (4) and the electrolyte layer (6) are adhered are formed. The electrochromic layer (5) and the electrolyte layer (6) were bonded so as to overlap with each other, and a portion in contact with the outside air was sealed with an epoxy resin to obtain a display device shown in FIG. As shown in FIG. 2, a transparent electrode (3),
(4) A DC power supply (7) is connected between them, and the electrolyte is applied only to R at the upper left corner in FIG. 3 by the thermal head (8) with the 4.0V full power supply so that the electrode (3) side is negative. Selective heating was performed to such an extent that the layer (6) was slightly moistened. As a result, the heated portion was colored red and returned to the original colorless state by applying a reverse voltage. Similar results were obtained when the other R, G, and B portions were heated and a voltage was applied. Then, when the thermal head (8) was driven based on the image signal, a full-color image was formed on the electrochromic layer (5). By the way, in the present embodiment, the selective heating is performed by the thermal head provided with the electrodes on the entire surface. However, the method for selectively coloring each of the R, G, and B electrochromic materials is not limited thereto. As typified by a method such as -y matrix or selective energization using a thin film transistor, any method of energization / selective heating, full-surface heating / selective energization, or selective heating / selective energization may be used. [Effects of the Invention] As is clear from the above description, in the display device of the present invention, since the coloring and erasing state of the electrochromic layer is controlled by both heat and electric field, it is possible to use a simple matrix. It is possible to provide an electrochromic display device capable of large-area display and high-resolution display without crosstalk. Further, in the electrochromic display device of the present invention, since the electrolyte layer and the electrochromic layer are solid at room temperature, liquid leakage does not occur even in the event that the cell is damaged, and handling becomes very easy. . Further, in the present invention, current flows only in the portion where heat is applied, and causes an oxidation-reduction reaction of the electrochromic layer.
Partial rewriting is possible, and the memory state does not deteriorate due to current leakage from the electrolyte layer side. Further, in the electrochromic display device of the present invention,
Since the electrochromic layer is coated with a plurality of materials with different colors, it is possible to color-deform multiple colors such as RGB (three primary colors of the additive method) and YMC (three primary colors of the subtractive color method). ,
Therefore, full-color display is also possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a main part showing an example of a configuration of an electrochromic display device to which the present invention is applied, and FIG. 2 is a cross-sectional view of a main part showing a selective heating state by a thermal head. is there. FIG. 3 is a plan view of a main part schematically showing an example of an electrochromic layer painted in three colors of RGB. 1,2 ... glass substrate 3,4 ... electrode 5 ... electrochromic layer 6 ... electrolyte layer

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-63-102104 (JP, A)                 JP-A-50-102291 (JP, A)                 Journal of Polymers, 44 [4] (1987)               P. 317-322

Claims (1)

(57) [Claims] A solid organic electrochromic layer in which a plurality of coloring / decoloring materials different from each other due to an electrochemical oxidation-reduction reaction and coloring / decoloring at least red, green, and blue are separately applied in a predetermined pattern; and a supporting electrolyte. In an electrochromic display device in which an electrode is formed on both electrodes while the solid-liquid changes by heating and cooling and the electric conductivity increases upon heating and melting, the organic electrochromic substance that develops a red color 2,4,7-trinitro-9-fluorenone is used, and 2,4,7-trinitro-9-fluorenylidene malononitrile is used as the organic electrochromic substance that emits green light. Characterized by using tetracyanoquinodimethane as an organic electrochromic substance that develops color Electrochromic display device that.