JPH09265265A - Reflection type display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type display element which has a simple structure and with which the effective utilization of incident light is possible and the display at a high contrast is possible. SOLUTION: This reflection type display element has a white opaque porous film 11, an impregnated film 12 which is arranged on the rear surface of the porous film 11 and is impregnated with a coloring liquid and piezoelectric plates 15 which are two-dimensionally arranged along the rear surface of the impregnated film 12 and put the coloring liquid reversibly into and out of the porous film 11 from the rear surface of the porous film 11. The respective piezoelectric plates 15 are disposed in correspondence to respective pixels. Images are displayed by controlling the respective piezoelectric plates 15 by each of the respective pixels. Namely, the color of the coloring liquid is produced on the front surface side of the porous film 11 by oozing the coloring liquid into the porous film. On the other hand, the color of the coloring is annihilated and the color of the porous film 11 itself is produced by returning the coloring liquid to the rear surface side of the porous film 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective display element that electrically controls pixels arranged two-dimensionally to display an image or a character.

[0002]

2. Description of the Related Art As a display used in a portable information device, a thin, lightweight and low power consumption type display is required. Conventionally, liquid crystal displays (LCDs), plasma displays, flat CRTs and the like are known as thin displays. Among them, the LCD, which has excellent characteristics such as power consumption, is most suitable for such applications, and thus is being put to practical use.

Among LCDs, the one in which the display surface of the display is directly viewed is called a direct-view type. Direct-view LCDs include a transmissive type that incorporates a light source such as a fluorescent lamp on the back surface and a reflective type that uses ambient light. Of these,
The former requires a backlight and is not suitable for low power consumption. Therefore, the latter reflective type is most popular as a display for portable information equipment.

The reflective LCD has an ECB (Electrically
Controlled Birefrigence mode, GH (Guest Hos
t) mode, TN (Twisted Nematic);
1737) mode, STN (Super Twisted Nema)
tic; JP 60-107020 A) mode and the like are used. A polarizing plate is required when using the ECB mode, TN mode, or STN mode. The polarizing plate is
Since the light transmittance is about 40%, there is a problem that the light utilization efficiency deteriorates.

When the GH mode is used, a polarizing plate is unnecessary, but the contrast is not generally high. On the other hand, a white tailor type GH which is a kind of GH element
Device (DLWhite, GNTaylor; J.Appl.Phys., Vol.45,
p.4718 to 4723 (1974)) has a structure in which a liquid crystal exhibiting a chiral nematic phase is mixed with a dichroic dye and arranged in parallel with the substrate surface. The alignment of the dichroic dye also changes with the change in the alignment of the liquid crystal due to the application of an electric field, and the dichroic dye changes its direction, whereby the light transmittance changes. Due to the twisted structure due to the chiral nematic phase, light absorption by the dye occurs efficiently, so that in principle, a relatively high display contrast can be obtained even without a polarizer. However, in order to achieve high contrast in this display method, it is necessary to match the spiral pitch of the chiral nematic liquid crystal with the wavelength order of light, but if the spiral pitch is shortened to that extent, many disclination lines occur. Display quality is impaired,
At the same time, a hysteresis phenomenon appears, and the response to an electric field becomes extremely slow. Therefore, when compared with the above-mentioned TN mode and STN mode, there remains a problem in practicality.

A reflection type display in which a dichroic dye is mixed in a nematic liquid crystal and a reflector or a liquid crystal structure is devised has been proposed (JP-A-59-178429 and JP-A-59-178428). ), The essential solution is not reached.

PDLC (Polymer Dispersed Liquid Cr) is another typical display method that does not use a polarizer.
There is a display system called ystal; JP-A-58-501631).

In this display system, nematic liquid crystal having positive dielectric anisotropy is dispersed in a polymer matrix in the form of particles having a diameter of several μm. As the liquid crystal, a material having a refractive index for ordinary light that is substantially the same as that of a polymer material and a refractive index for extraordinary light different from that of the polymer material is selected and used. In the initial state, the liquid crystal particles have a distorted array structure in the particles, and moreover, the difference in the refractive index occurs between most of the liquid crystal particles and the polymer matrix due to the dispersion of the array direction between the liquid crystal particles, As a result, it scatters light like frosted glass. When a sufficient voltage is applied to this, rearrangement of the liquid crystal molecules in the grains occurs, and the refractive indices of the liquid crystal and the polymer matrix with respect to vertically incident light become equal. As a result, refraction and reflection at the interface between the liquid crystal and the polymer disappear, and the state changes to a transparent state. The incident light need not be linear light.
Since the display is performed using the above-described operation principle, a polarizer is not necessary, and the incident light can be effectively used, resulting in a bright display. However, in order to achieve a sufficient display contrast, a film thickness of several tens of μm is required, resulting in a driving voltage of several tens of volts. Moreover, since it is a scattering type, it is effective for a projection type display, but is not suitable for a direct view display for OA equipment or the like.

The biggest drawback of the reflective display device using the liquid crystal as described above is that the light utilization efficiency is low or the contrast is insufficient. On the other hand, a reflective display element that does not use liquid crystal is also known. JP 4-16698
Japanese Laid-Open Patent Publication No. 1-58242 discloses a reflection type display element in which a colored liquid is taken in and out through a minute hole provided at the bottom of the recess in an inverted pyramidal recess formed by micromachining a Si substrate. Also, a reflective display element has been proposed in which a movable film is taken in and out by utilizing electrostatic force. Although these reflective display elements that do not use liquid crystals have excellent characteristics in terms of contrast and reflectance, they generally have the disadvantage that it takes more time to prepare the elements than the above-mentioned liquid crystal display elements.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a simple structure as compared with a conventional liquid crystal display device and effectively use incident light. Another object of the present invention is to provide a reflective display element capable of achieving high contrast display.

[0011]

In order to achieve the above object, the reflective display element of the present invention comprises an opaque porous film, a layer of a coloring liquid disposed on the back surface of the porous film, and the coloring. A driving means arranged two-dimensionally along the back surface of the liquid layer and reversibly putting the colored liquid in and out of the porous film from the back surface of the porous film; An image is displayed by controlling the driving unit for each pixel in correspondence with the pixel.

According to the present invention, by controlling the driving means two-dimensionally arranged on the back surface of the opaque porous film and the layer of the coloring liquid, the coloring liquid is made to permeate from the back surface of the opaque porous film. It is reversibly put in and taken out for each pixel area in the quality film. That is, by exuding the colored liquid into the porous film, the color of the colored liquid appears on the front surface side of the porous film for each pixel region, while returning the colored liquid to the back surface side of the porous film. By (collecting), the color of the colored liquid disappears from the surface side of the porous film, and the color of the porous film itself is displayed.

In the reflective display element of the present invention, the porous film itself does not need to be subjected to any special fine processing, so that its structure can be made relatively simple.

In the above reflective display element, if the viscosity of the coloring liquid is adjusted so that the adjacent pixels do not affect each other, the coloring liquid layer may be formed in each pixel region. It is not necessary to arrange the partition member, and the structure is further simplified.

Further, by providing a partition member corresponding to each pixel region in the layer of the coloring liquid and regularly allocating a plurality of kinds of coloring liquids to each of the pixels, color display is possible.

By setting the contact angle between the porous film and the coloring liquid to be 30 degrees or more, it is possible to prevent the coloring liquid from seeping out spontaneously on the surface of the porous film, and at the same time, to add the coloring liquid to the porous film. It is possible to ensure the stability of the operation of reversibly moving in and out.

Further, the impregnated film is disposed between the opaque film and the driving means, and the colored liquid is held by the impregnated film to prevent the leakage of the colored liquid and to repeatedly perform the operation of exuding and returning. It becomes possible to have credibility about. Further, since the coloring liquid which is difficult to handle can be easily arranged in the form of a film, the production of the reflection type display device becomes easy.

When the impregnated film is used to hold the coloring liquid, the contact angle between the impregnated film and the coloring liquid is smaller than the contact angle between the porous film and the coloring liquid. As a result, it is possible to prevent the coloring liquid from seeping out into the porous film naturally. Further, it becomes possible to return the liquid that has once exuded into the porous film to the inside of the impregnated film without leaving it.

Further, when a transparent protective substrate such as a glass plate is arranged on the porous film, the contact angle between the protective substrate and the coloring liquid is determined by determining the contact angle between the porous film and the colored film. It should be larger than the contact angle with the liquid. This prevents the colored liquid from leaking or evaporating from the reflective display element and prevents the protective liquid from being colored by the colored liquid.

When a liquid containing a liquid crystal substance is used as the coloring liquid, a transparent electrode is arranged on the surface side of the porous film and the driving means is arranged corresponding to each pixel. It consists of. When an electric field is applied between the pixel electrode and the transparent electrode, it is more stable in terms of energy when the liquid crystal is oriented and gathered in the part to which the electric field is applied. Bleeds into the porous film and the surface of the porous film is colored.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

Example 1 FIG. 1 shows a first example of the embodiment of the present invention. FIG. 1 is a schematic configuration diagram showing a cross section of a reflective display element, in which 13 is a glass substrate, 11 is a white opaque porous film, 12 is an impregnated film impregnated with a coloring liquid in which a dye is dissolved, and 14 Is a diaphragm, and 15 is a piezoelectric plate (driving means). Electrodes (not shown) are formed on both surfaces of the piezoelectric plate 15, and each electrode is connected to an active matrix circuit so that a voltage can be selectively applied.

In this example, as the glass substrate 13, a glass plate having a thickness of 1.5 μm whose surface is hydrophilically treated, and as the white opaque porous film 11, a porous cross-linked polyvinyl alcohol film (in which titanium oxide fine particles are dispersed) ( The thickness is 20 μm), silicone oil in which lipophilic black dye is dissolved is used as the coloring liquid, and the impregnation film 12 is a porous polystyrene film (thickness 60 μm) partially crosslinked with divinylbenzene. Further, a Teflon film is used as the diaphragm 14, a piezoelectric thin film is laminated on the surface of the Teflon film by a sputtering method, and then the piezoelectric thin film is etched into a predetermined pattern to form a piezoelectric plate 15 corresponding to each pixel. Has been done.

In this reflective display element, the contact angle formed by the silicone oil, which is a coloring liquid, and the white opaque porous film 11 was 80 degrees. By adjusting the viscosity of the silicone oil to 5,000 cP or more, it is possible to prevent the coloring from bleeding between the pixels, so that it is not necessary to provide a partition member in the layer of the coloring liquid for each pixel. .

Next, the operation of the reflection type display device having the above structure will be described with reference to FIG.

When no voltage is applied to the piezoelectric plate 15, the reflective display element looks white when viewed from the glass substrate 13 side. When a voltage is applied to a particular piezoelectric plate 15, the piezoelectric plate 15 is deformed into a concave shape as shown in FIG. As a result, the coloring liquid seeps out from the impregnated film 12 into the white opaque porous film 11, and as a result, the opaque porous film 11 is colored black when viewed from the glass substrate 13 side. When the application of voltage is stopped, the opaque porous film 11, the impregnated film 12 and the diaphragm 14 are all elastic bodies, and thus return to the original state as shown in FIG. Since the respective members are combined so that the affinity between the coloring liquid and the impregnated film 12 is maximized, no color remains.

As described above, by driving the piezoelectric plate 15 to exude the black colored liquid into the white porous opaque film 11, an image or a character can be displayed with a combination of white and black pixels. it can. Further, it is also possible to display an intermediate color by adjusting the amount of deformation of the piezoelectric plate 15 with a voltage. In this example, since the coloring liquid is directly taken in and out, the contrast is sufficiently large, the reflectance in the white state can be increased, and so-called paper-like display characteristics can be realized.

(Example 2) FIG. 3 shows a second example of the embodiment of the present invention. FIG. 3 is a schematic configuration diagram showing a cross section of the reflective display element, in which 13 is a glass substrate, 11 is a white opaque porous film, 17 is red (R), green (G), and blue (B). , A coloring liquid in which each of the black (Bl) dyes is dissolved,
16 is a partition member between each pixel, 14 is a diaphragm, 1
Reference numeral 5 indicates a piezoelectric plate. Electrodes (not shown) are formed on both surfaces of the piezoelectric plate 15, and each electrode is connected to an active matrix circuit so that a voltage can be selectively applied.

Silicon oil is used as the coloring liquid 17, a silicone resin template is placed on the diaphragm 14 as the partition member 16 between pixels, and a prepolymer of urethane resin is injected from the outside using surface tension. After being cured by heating, the one prepared by removing the mold was used.

By driving the piezoelectric plate 15, a colored liquid of any color among the above four colors is exuded into the white opaque porous film 11 to display a color image or characters. You can Further, it is also possible to display an intermediate color by adjusting the amount of deformation of the piezoelectric plate 15 with a voltage. In this example, since the coloring liquid is directly taken in and out, the contrast is sufficiently large, the reflectance in the white state can be increased, and so-called paper-like color display characteristics can be achieved.

Here, the above red green blue black (R, G,
By using the coloring liquids of yellow, magenta, and cyan colors instead of B, Bl), the color becomes pastel and bright display is possible.

(Example 3) FIG. 4 shows a third example of the embodiment of the present invention. FIG. 4 is a schematic configuration diagram showing a cross section of the reflective display element, in which 13 is a glass substrate, 11 is a white opaque porous film, 12 is red (R), green (G), and blue (B). , An impregnation film containing any one of black (Bl) coloring liquids, 18 is a space between pixels, 14 is a diaphragm, and 15 is a piezoelectric plate. Electrodes (not shown) are formed on both surfaces of the piezoelectric plate 15, and each electrode is connected to an active matrix circuit so that a voltage can be selectively applied.

Silicon oil is used as the coloring liquid. The impregnated film 12 is a polystyrene resin impregnated with a coloring liquid, and an ink-like one is used for the diaphragm 1.
It is formed by printing on 4.

Displaying a color image or characters by driving the piezoelectric plate 15 to exude a coloring liquid of any color from the above four colors into the white opaque porous film 11 You can Further, it is also possible to display an intermediate color by adjusting the amount of deformation of the piezoelectric plate 15 with a voltage. In this example, since the colored liquid is directly taken in and out, the contrast is sufficiently large, the reflectance in the white state can be increased, and so-called paper-like color display characteristics can be realized.

Example 4 FIG. 5 shows a fourth example of the embodiment of the present invention. FIG. 5 is a schematic configuration diagram showing a cross section of a reflective display element, in which 13 is a glass substrate, 20 is a transparent electrode, 11 is a white opaque porous film, and 12 is a black dye-dissolved silicone oil ( An impregnated film impregnated with a coloring liquid, 14 is a diaphragm, and 19 is an aluminum electrode corresponding to a pixel electrode. Each aluminum electrode 19
Are connected to an active matrix circuit (not shown) so that voltage can be selectively applied.

When no static voltage is applied to the aluminum electrode 19 (pixel electrode), the reflective display element looks white when viewed from the glass substrate 13 side. When a static voltage is applied to the specific aluminum electrode 19, an electrostatic attractive force is generated between the aluminum electrode 19 and the transparent electrode 20, and the aluminum electrode 19 is deformed into a concave shape. by this,
The coloring liquid exudes from the impregnated film 12 into the white opaque porous film 11 and is colored black when viewed from the glass substrate 13 side. When the application of the voltage is stopped, the white opaque porous film 11, the impregnated film 12 and the diaphragm 14 are elastic bodies and thus return to the original state. Coloring liquid and impregnated film 1
Since the members are combined so that the affinity with 2 is the highest, there is no residual color.

As described above, in this example, by driving the aluminum electrode 19 to exude the black colored liquid into the white opaque porous film 11, images and characters are combined with a combination of white and black pixels. Can be displayed. Further, by adjusting the amount of deformation of the aluminum electrode 19 with a voltage, it is possible to display an intermediate color. In this example, since the coloring liquid is directly taken in and out, the contrast is sufficiently large, the reflectance in the white state can be increased, and so-called paper-like display characteristics can be realized.

(Example 5) In the reflective display element of the fifth example of the embodiment of the present invention, a nematic liquid crystal (Mer) was used as the coloring liquid instead of the silicone oil in the fourth example (FIG. 5).
K-7, E-7) is used. Other configurations are the same as those in the fourth example.

When the AC voltage (50 Hz) is not applied to the aluminum electrode 19 (pixel electrode), the reflective display element looks white when viewed from the glass substrate 13 side. When an alternating voltage is applied to the specific aluminum electrode 19, the liquid crystal is attracted between the aluminum electrode 19 and the transparent electrode 20, and the porous film 1 is removed from the impregnated film 12.
The reflective display element oozes out into the glass substrate 1
Seen from the 3 side, it is colored black. When the voltage application is stopped, it returns to the original state. Since the respective members are combined so that the affinity between the coloring liquid and the impregnated film 12 is maximized, no color remains.

As described above, in this example, by driving the aluminum electrode 19 to exude the black colored liquid into the white opaque porous film 11, a combination of white and black pixels is used to form an image or image. Characters can be displayed. Further, it is possible to display an intermediate color by adjusting the amount of seepage of the liquid crystal by the voltage or the frequency. In this example, since the colored liquid is directly taken in and out, the contrast is sufficiently large, the reflectance in the white state can be increased, and so-called paper-like display characteristics can be realized.

[0041]

As described above, since the reflective display element of the present invention displays an image and the like based on a very simple operation principle, it makes effective use of incident light and has a high contrast. It is possible to realize the display of
It has excellent characteristics as a low power consumption type display used in portable information devices.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a cross section of a reflective display element of a first example of an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an operating state of the reflective display element of the first example of the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a cross section of a reflective display element of a second example of an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a cross section of a reflective display element of a third example of an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing a cross section of a reflective display element of a fourth example of an embodiment of the present invention.

[Explanation of symbols]

 11 ... White opaque porous film, 12 ... Impregnation film holding a coloring liquid, 13 ... Glass substrate (protective substrate), 14 ... Diaphragm, 15 ... Piezoelectric plate (driving means) , 16 ... Partition member between pixels, 17 ... Colored liquid, 18 ... Space between pixels, 19 ... Aluminum electrode (pixel electrode), 20 ... Transparent electrode.

Claims (8)

[Claims] 1. An opaque porous film, a layer of a coloring liquid disposed on the back surface of the porous film, and two-dimensionally arranged along the back surface of the layer of the coloring liquid, A driving means for reversibly moving the porous film into and out of the porous film from the back surface thereof, wherein each driving means is associated with each pixel and an image is formed by controlling the driving means for each pixel. A reflective display element characterized by displaying. 2. The layer of the colored liquid is not provided with a partition member corresponding to each pixel, and the viscosity of the colored liquid is adjusted so as not to affect each other between adjacent pixels. The reflective display element according to claim 1, characterized in that: 3. The color liquid layer is provided with a partition member corresponding to each pixel, and color display is performed by assigning a plurality of kinds of color liquid to each pixel. Reflective display device. 4. The reflective display element according to claim 1, wherein a contact angle formed by the porous film and the colored liquid is 30 degrees or more. 5. The impregnating film is arranged between the porous film and the driving means, and the coloring liquid is retained by the impregnating film. The reflective display element described. 6. The reflective display element according to claim 5, wherein a contact angle formed by the impregnated film and the coloring liquid is smaller than a contact angle formed by the porous film and the coloring liquid. 7. A transparent protective substrate is provided on the surface side of the porous film, and a contact angle between the protective substrate and the coloring liquid is larger than a contact angle between the porous film and the coloring liquid. The reflective display element according to any one of claims 1 to 3, characterized in that. 8. The coloring liquid contains a liquid crystal substance, and a transparent electrode is arranged on the surface side of the porous film,
The driving means is composed of pixel electrodes arranged corresponding to each pixel, and an electric field is applied between the pixel electrodes and the transparent electrode, whereby the coloring liquid is introduced from the back surface of the porous film into the porous film. The reflective display element according to any one of claims 1 to 3, wherein the reflective display element is reversibly put in and taken out of the film.