JPH0758421B2 - Thermal head and display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a heat-driven display device.

[Conventional technology]

A conventional display device of this type is, for example, Japanese Patent Publication No. Sho 60-3325.
As disclosed in Japanese Patent No. 4 publication, a so-called thermal display is known which uses a line thermal head and a thermo sheet that moves relatively to the head.

FIG. 5 is a perspective view showing the structure of this thermal display. In the figure, 1 is a line thermal head, 2
Is an endless thermo sheet, 3 is a feed roller for moving the thermo sheet 2 in the direction of arrow A, 4 is a color filter, 5 is a cooler, 6 is a fluorescent lamp, and 7 is a heater. A thermoreversible material is applied on the surface of the thermosheet 2. The color of this thermoreversible material reversibly changes with temperature. That is, such a material has a hysteresis characteristic in the temperature concentration characteristic. FIG. 6 shows an example of characteristics of Ag ₂ HgI ₄ thermoreversible material. The thermal display utilizes this hysteresis characteristic to write (display) and erase images. That is, in displaying an image, heat is applied to the thermo-sheet 2 moving at a constant speed by the line thermal head 1, and the heat-applied portion of the thermo-sheet 2 is discolored. Also,
When the image is erased, the thermo sheet 2 is forcibly cooled by the cooler 5 to restore the color of the heat application portion. Here, in order to increase the contrast of the displayed image and improve the visibility, the fluorescent sheet 6 is normally used to irradiate the thermosheet 2 from the back side of the thermosheet 2, and the light caused by the heat application of the thermosheet 2 is applied. The change in translucency is taken out through the color filter 4.

Further, as a conventional display device, JP-A-60-208787 discloses a surface thermal display using a surface (two-dimensional) thermal head. A sectional view of this surface thermal display is shown in FIG. In the figure, 8 is a glass substrate, 9 is an X wiring, 10 is a heat insulating layer such as polyimide, 11 is a through-hole conductor, 12 is a Y wiring, and 13 is a temperature indicating material having the characteristics shown in FIG. Layers and 14 are resistors.
To display an image, first, one resistor 14 is selected by selecting one each from the X wiring 9 and the Y wiring 12. Actually, the selection terminal of the X wiring 9 is 0, and the non-selection terminal is
2 / 3E, E for selected terminal of Y wiring 12 and 1 / for non-selected terminal
Apply a voltage of 3E. This causes the selected resistor 14
To the low antibody 14 and 1 / 3E to the low antibody 14 which is not selected. Therefore, only the resistor 14 selected according to the image information is applied with a voltage three times as high as the other voltage, and as a result, the amount of heat generated is nine times, and the temperature indicating material layer 13 is locally heated and discolored.

[Problems to be solved by the invention]

However, the thermal display using the line thermal head has the following problems.

(B) Since this thermal display uses the line thermal head 1, it is necessary to move the thermal head 1 and the thermosheet 2 relative to each other, and thus a predetermined time is required to form one screen. There is a problem.

(B) In addition, in order to maintain the formed screen as it is, it is necessary to maintain the temperature state of the heat-applied portion and the non-heat-applied portion of the thermosheet 2. In order to maintain this temperature state in the state where the heat is applied once, it is necessary to maintain the discolored state of the thermosheet 2 by applying the heat once. In particular, the temperature inside the thermal display device is actually lower than the heat application temperature. Therefore, in order to prevent the color recovery even in this state, the thermo sheet 2 which exhibits a hysteresis characteristic at a relatively low temperature is used, or a medium for heat retention other than the thermoreversible material applied to the thermo sheet 2 is used. It is conceivable to mix in or heat the inside of the apparatus to some extent by providing a heater 7 as shown in FIG.

However, in the above case, when heat is repeatedly applied, the temperature inside the device rises, which may cause discoloration of the entire surface of the thermosheet 2. Further, in the case of, the translucency of the thermosheet 2 is deteriorated. Further, in the case of (1), it is useful to prevent the color restoration, but the temperature control is extremely difficult because it is necessary to forcibly cool by the cooler 5 in order to restore the color.

(C) Further, in order to improve the contrast, the fluorescent lamp 6
Since the color filter 4 and the cooler 5 for restoring the color are required, the size of the apparatus becomes large.

(D) On the other hand, the surface thermal display having the configuration shown in FIG. 7 has the following problems.
The structure and manufacturing are complicated because it is necessary to electrically connect with the conductor of the through hole passing through 13. Moreover, since resistors corresponding to the number of dots are required, the configuration and manufacturing become complicated. Therefore, the cost is high.

Therefore, the present invention provides a thermal head that is simple in structure and manufacturing and efficient, and does not require relative movement of the thermal head and the thermosheet, a color filter, a fluorescent lamp, a heater, a cooler, etc. An object of the present invention is to provide a display device which is easy to manufacture and whose image display is easily controlled.

[Means for solving problems]

The thermal head according to the present application includes a base in an electrically insulating state and a plurality of first bases arranged in one direction on one surface of the base.
Electrode lines, a resistance film formed on a surface including the first electrode lines, and a plurality of second electrode lines arranged on the resistance film in a direction intersecting with the first electrode lines. The surface area of the electrode wire portion corresponding to the heating element point in the resistance film formed by intersecting the two electrode wires is larger than the surface area of the other portion, and an electrically insulating base body is provided. A plurality of first electrode lines arranged in one direction on one surface of the base;
A resistance film formed on a surface including the electrode line, a plurality of second electrode lines arranged on the resistance film in a direction intersecting with the first electrode line, and And an insulating layer provided between the second electrode lines or between the second electrode lines.

The display device of the present application is formed on an electrically insulating substrate, a plurality of first electrode lines arranged in one direction on one surface of the substrate, and a surface including the first electrode lines. Resistance film,
A plurality of second electrode lines arranged on the resistance film in a direction intersecting with the first electrode line, and an electrode line corresponding to a heating element point in the resistance film formed by intersecting the two electrode lines. On the surface including the electrode wire and the insulating layer provided between the first electrode wires or between the second electrode wires, and the surface area of the part is larger than the surface area of the other part. And a discoloration layer formed of a thermoreversible material that discolors due to heat, provided directly or through a protective film electrically insulated.

[Action]

According to the thermal head of the present application, the electrode lines provided on both surfaces of the resistance film are selected according to the image signal, and the voltage is applied. Then, the current flows from one electrode line to the other electrode line through the resistance film. As a result, the region of the resistance film sandwiched by the energized electrode wires, that is, the heating element point, generates heat.
The generated heat is radiated to the outside through the electrode wire provided on the upper surface of the resistance film. The surface area of the electrode wire corresponding to the heating element point in the resistance film is increased to increase the heat radiation from this area, and the insulating layer provided between the electrode wires causes the adjacent electrode wires to be adjacent to each other. Heat transfer to the is blocked and leakage current is blocked.

According to the display device of the present application, the electrode lines provided on both surfaces of the resistance film are selected according to the image signal, and the voltage is applied. Then, the current flows from one electrode line to the other electrode line through the resistance film. As a result, the region of the resistance film sandwiched by the energized electrode wires, that is, the heating element point, generates heat. This heat generation is applied to the discoloration layer of the thermoreversible material via the electrode wire provided on the upper surface of the resistance film, and the area corresponding to the heat generation point is discolored. The surface area of the electrode wire corresponding to the heating element point in the resistance film is increased to increase the heat radiation from this area, and the insulating layer provided between the electrode wires causes the adjacent electrode wires to be adjacent to each other. The heat conduction to is blocked and the leakage current is blocked. Therefore, the display is efficiently and clearly displayed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment showing a technique on which the present invention is based. In the figure, 15 is a substrate. The substrate is in an electrically insulating state and is made of, for example, ceramics, glass, plastic, or a metal whose surface is electrically insulated. 16 is a glaze glass layer, which is provided on the substrate 15. The substrate 15 and the glazed glass layer 16 form a base. The glazed glass layer 16 has a heat retaining property. Reference numeral 17 is an electrode line, which is arranged on the surface of the glaze glass layer 16 in one direction (parallel direction to the paper surface in the figure) at substantially equal intervals. The electrode wire 17 is attached on the surface of the glaze glass layer 16 by plating, etching or the like. 18 is a resistance film. The resistance film 18 is applied on the surface of the glaze glass layer 16 including the electrode wires 17. The resistance film 18 is formed of tantalum nitride, for example. Reference numeral 19 is an electrode wire. The electrode wires 19 are arranged on the surface of the resistance film 18 at substantially equal intervals in a direction perpendicular to the longitudinal direction of the electrode wires 17. Each electrode wire 19 is formed by plating or etching. A region of the resistance film 18 sandwiched between the electrode wire 17 and the electrode wire 19 forms one heating element point. 20 is a thermo sheet. The thermo-sheet 20 is formed by applying a thermo-reversible material mainly on the surface of the substance on the sheet. The thermo-reversible material having the temperature-optical density characteristic as shown in FIG. 2 is used. As can be seen by comparing FIG. 2 and FIG. 6, this characteristic is characterized in that there is a thermochromic region on the relatively high temperature side and that the sensitivity of discoloration to temperature is excellent (heat retention is small). And An example of such a dye is mercury iodide (Ag ₂ HgI ₄ ). The thermosheet 20 formed in this manner is adhered and fixed on the entire surface of the resistance film 18 including the electrode wires 19 using an adhesive or the like.

However, the thermo sheet 20 has colors such as blue, yellow, and brown,
You can freely change and use this according to the way of operation as a display. Therefore, in such a case, the thermoseat 20 is provided so as to be removable.

Next, the operation will be described. First, according to the image signal, the electrode wire 17
When electricity is applied to the electrodes 19 and 19, the current flows in the order of the electrode wire 17 → resistive film 18 → electrode wire 19 (or vice versa), and the region of the resistive film 18 (heating element point) sandwiched between the electrode wire 17 and the electrode wire 19 is Fever.
This heat is mainly transferred to the thermosheet 20 via the electrode wire 19. Then, the corresponding area of the thermosheet 20 is discolored. At this time, since the thermoreversible material of the thermosheet 20 has a low heat preservation property as shown in FIG. 2 described above, the contrast of discoloration of the thermosheet 20 obtained by applying heat is extremely large. Therefore, there is no need for a fluorescent lamp or a color filter for obtaining an image by transmitted light as in the conventional case. Therefore, according to this embodiment, an extremely excellent display surface can be obtained by natural light from the surface side. Further, since the heat discoloration temperature is on the relatively high temperature side and the sensitivity of discoloration is excellent, there is an advantage that a cooler for recoloring is not required.
In the above operation, if discoloration is maintained for a long time,
The application of heat to the thermosheet 20 may be repeated in a short time.

FIG. 3 is a sectional view of another embodiment showing the technology on which the present invention is based. In the figure, the same members as those shown in FIG. 1 are designated by the same reference numerals. Reference numeral 21 is a protective film. The protective film 21 is attached on the surface of the resistive film body 18 including the electrode wires 19. The protective film 21 is formed of, for example, Ta ₂ O ₅ or SiO ₂ .
The film pressure of the protective film 21 may be about 2 to 3 μm. 22 is a protective film 21
A layer of thermoreversible material applied directly on top. Since the display operation of this structure is the same as the display operation of the structure of FIG.
The description here is omitted. As another structure, the first
A further transparent thin protective film may be provided on the thermosheet 20 shown in the figure or on the layer 22 of thermoreversible material shown in FIG.
In this way, writing and erasing become possible on the surface of this protective film.

In the above, the Example which shows the technique used as the premise of this invention was demonstrated. Although the electrode wire 19 used in the above embodiment has a constant width over the entire length, as a feature of the present invention, the heat generated at the heat generating raw material is adjacent to the heat generating raw material via the electrode wire 19. In order to reduce the transmission to the electrode wire 17, the surface area of the electrode wire 19 intersecting the electrode wire 17 may be made large, and the surface area of the other part may be made small. Further, as shown in FIG. 4, a control circuit (shift register or driver) 23 and a matrix wiring section 24 which are peripheral devices thereof may be provided on the same substrate 25 as the thermal display according to this embodiment. Is.

FIG. 8 shows a sectional view of another embodiment of the present invention. In the figure, the same elements as those shown in FIG. 1 are designated by the same reference numerals. In this embodiment, a heat insulating portion 29 having the same resistance as that of the electrode surface of the electrode wire 19 and having an electric insulation property is provided between the adjacent electrode wires 19. The heat insulating section 29 is for blocking the leakage current in the adjacent direction of the adjacent electrode wire 19, that is, the heating element, and for insulating the heat diffusion. With such a configuration, when a current is applied to one electrode wire, it is possible to prevent the heat generating elements along the adjacent electrode wires from generating heat, and it is possible to better guide the heat generation to the outside.

9 (a) to 9 (f) show still another embodiment of the present invention. Of these, FIG. 7 (a) is a perspective view showing a part of it, and FIGS. 6 (b) to 6 (f) are BB of FIG.
It is a line, CC line, DD line, and FF line sectional drawing. In this embodiment, as in the embodiment shown in FIG. 8, heat insulating portions 29 are provided at intervals between the adjacent electrode wires 19 (FIG. 9 (b)). Further, a heat insulating portion 41 is provided for the space between the electrode wires 17 (FIG. 9 (f)). Further, the resistive layer 42 in this embodiment comprises three layers 43, 44 and 45. Middle layer 44
Is a continuous layer of resistive material, as shown in Figure 9 (d). The upper and lower layers 43 and 45 are insulating layers 43a and 45a, as shown in FIGS. 9 (c) and (e).
The spot-like resistance materials 43b and 45b are arranged in the generating element positions so as to form a matrix. The spots 43b and 45b are continuous with the resistance layer 44. Therefore, at the position of the heating element point, the resistance material is continuous in the vertical direction to form the resistance element. As described above, when the insulators 43a and 45a are provided so as to surround the spot, it is possible to prevent the diffusion of heat from the selected exothermic element to the surrounding area, and thus drive the selected exothermic element. It can reduce the power required to

Alternatively, layers 43 or 45 or both may be omitted. The difference between both layers 43 and 45 omitted from FIG. 8 is that the heat insulating layer 41 is provided.

10 (a) to 10 (d) show still another embodiment of the present invention. Of these figures, the same figure (a) is a plan view and the same figure (c).
(D) is BB line, CC line, DD sectional view taken on the line. This embodiment is generally shown in FIG.
This is the same as the embodiment of (f), but a diode 51 is provided at each heating element point. In this diode 51, one electrode, for example, the anode 51a, is connected to the electrode wire 17, and the other electrode, for example, 51b, is connected to the spot 45b of the resistive material. The diode 51 is made of, for example, polysilicon, and can be formed by, for example, depositing it by a CVD method, selectively doping p-type and n-type impurities, and etching it so as to have a desired pattern. The pn junction that is reverse bypassed is also bypassed by the Al layer 52. The electrode wire 17 is formed so that one side is connected to the anode 51a of the diode 51. In the illustrated configuration, each heating element is formed at a position where the cathode 51b of each diode 51 is exposed to the resistance layer and is connected thereto. The insulating layer 45 on the electrode wire 17 has a current
From flowing directly into the resistance layer 44.

The circuit configuration of the matrix of the heating element points having the diodes is as shown in FIG. The role of the diode is to prevent heat generation at the non-selected heating element points. When the diode 51 is not provided, a small current flows through the resistance element of the heating element point that is not selected. For example, it is assumed that the heat generation raw point at the intersection of the electrode lines B3 and A2 is selected. Then, the resistance element R23 at the intersection of B3 and A2
A part of the current passing through the resistance element R2 at the intersection of A2 and B2
Flow through line 2 into line B2. As a result, the unselected heating element at the intersection of B2 and A2 generates heat. Providing the diode as described above avoids such undesired heat generation.

12 (a) to (d) show still another embodiment of the present invention. Of these figures, the same figure (a) is a plan view and the same figure (b).
(D) is a BB line, CC line, DD sectional view taken on the line of (a) of the figure. This embodiment is roughly the same as the embodiment of FIGS. 10 (a)-(d), but the anode of the diode 51 is connected to the electrode wire 17 on its lower surface. Each electrode wire 17
Is the wide lower part 17a and the narrow upper part 1 connected to it.
7b and the upper part 17b has an anode 51a on its upper surface.
It is connected to the.

13 (a) to 13 (c) show still another embodiment of the present invention. Of these, FIG. 7A is a plan view, and FIGS. 7B and 7D are cross-sectional views taken along line BB and CC in FIG. This embodiment is generally the same as the embodiment of FIGS. 10 (a)-(d) and 12 (a)-(d), except that each diode 51 has p-type and n-type layers They differ in that they are stacked in the same direction. The lower end of the stacked body constitutes the anode 51d and is connected to the electrode wire 17. The upper end of the stack forms the cathode 51e and is connected to the resistance layer 44.

〔The invention's effect〕

As described above, according to the invention of the present application, the following effects can be obtained.

(A) In the present invention, the electrode wire is provided with the resistance film interposed therebetween, so that the structure is simple and the manufacturing is easy. Also, the control of image display and deletion becomes simple.

(B) In the present invention, the layer having a thermoreversible material (for example, a thermosheet) is provided so as to be fixed to the heat generating portion. Therefore, it is not necessary to relatively move the heat generating portion and the layer having a thermoreversible material. .

(C) The thermoreversible material used has a relatively high thermal discoloration temperature, so it is possible to display an image with high contrast without using color filters, fluorescent lamps, heaters, etc., and downsize the device. can do.

In the invention of the present application, in addition to the above, an insulating layer is further provided between the electrode wires to prevent heat transfer from one electrode wire to an adjacent electrode wire. Also, leakage current is blocked. Therefore, when a current is applied to one electrode wire, it is possible to prevent heat generation in the heating elements along the adjacent electrode wires. Therefore, the display becomes clear.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment showing a technology on which the present invention is based, FIG. 2 is a view showing temperature-optical density characteristics of a thermoreversible material used in this embodiment, and FIG. FIG. 4 is a cross-sectional view of another embodiment showing the technology underlying the invention, FIG. 4 is a perspective view of a structure in which the display device according to the embodiment of the present invention and its peripheral circuits are mounted on the same substrate, and FIG. 5 is a line thermal head. FIG. 6 is a perspective view of a conventional display device using the same, FIG. 6 is a diagram showing temperature-optical density characteristics of Ag ₂ HgI ₄ , and FIG. 7 is a sectional view of a conventional display device using a surface thermal head, FIG. Is a cross-sectional view of another embodiment of the present invention, FIG. 9 (a) is a perspective view of yet another embodiment of the present invention, and FIGS. 9 (b) to 9 (f) are B of FIG. 9 (a). -B line, CC line, DD line, EE line, F
FIG. 10 is a cross-sectional view taken along line -F, FIG. 10 is a view showing a further embodiment of the present invention, FIG. 11 is a view showing a circuit configuration of the embodiment shown in FIG.
12 and 13 are views showing still another embodiment of the present invention. 15 …… Substrate, 16 …… Glazed glass layer, 17 …… Electrode wire, 18 …… Resistance film, 19 …… Electrode wire, 20 …… Thermosheet, 21 …… Protective film, 22 …… Thermo-reversible material Layer, 23 ... control circuit, 24 ... matrix wiring part, 25 ... substrate.

Claims (3)

[Claims] 1. An electrically insulating substrate, a plurality of first electrode lines arranged in one direction on one surface of the substrate, and formed on a surface including the first electrode line. A resistance film and a plurality of second electrode lines arranged in a direction intersecting with the first electrode line on the resistance film, and heat generated in the resistance film formed by intersecting the two electrode lines. The thermal head is characterized in that the surface area of the electrode wire portion corresponding to the raw point is larger than the surface area of other portions. 2. An electrically insulating substrate, a plurality of first electrode lines arranged in one direction on one surface of the substrate, and a surface including the first electrode lines. A resistance film, a plurality of second electrode lines arranged on the resistance film in a direction intersecting with the first electrode line, between the first electrode lines or between the second electrode lines. A thermal head comprising an insulating layer provided between them. 3. An electrically insulating substrate, a plurality of first electrode lines arranged in one direction on one surface of the substrate, and formed on a surface including the first electrode line. A resistance film, a plurality of second electrode lines arranged on the resistance film in a direction intersecting with the first electrode line, and a heating element point in the resistance film formed by intersecting the two electrode lines. The surface area of the corresponding electrode wire is made larger than the surface area of the other portion, and the insulating layer and the electrode wire provided between the first electrode wires or between the second electrode wires are A display device, comprising: a color change layer formed on a surface including the film directly or via a protective film electrically insulated and formed of a thermoreversible material that changes color by heat.