JP2000347184A - Information display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an information display device capable of displaying of various information by combining a memorizable reflective liquid crystal display element having various advantages with another display means capable of covering its demerit. SOLUTION: This information display device 1A is composed of, for example, a memorizable reflective liquid crystal display element 2 constituting a comparatively large area display screen and a thin film transistor(TFT) driven liquid crystal display element 3 in a state of overlapping it and constituting a small display screen. A still picture with little movement is displayed on the display element 2 and a dynamic picture is displayed on the display element 3 capable of being driven at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information display device, and more particularly to an information display device having various display means such as LC, EL, and PDP.

[0002]

BACKGROUND OF THE INVENTION At present, information is provided over a wide area by printed matter, but there is concern that it will be discarded as garbage and that forest resources for pulp and paper will be depleted. The present inventors distribute the information printed on conventional paper in a state recorded on a digital information recording medium, and establish a form in which a user can read the information on a display device such as an LC, EL, or PDP. An electronic book system is being developed with the idea that the consumption of paper itself is suppressed and the resource problem is eased. As information, we believe that any printed matter such as books (paperback books, weekly magazines, monthly magazines, specialized magazines, etc.), newspapers, and advertising magazines can be replaced with such a system.

[0003] Digital information of books is distributed as a recording medium by a publisher (manufacturer), and a general user who owns (or rents) a reproduction display device inserts the recording medium into the electronic book device body. This is a system for viewing (reproducing) information.

[0004] In order to achieve the above systematization, it is necessary to finish the device as small and thin as a book, and to be freely open and viewable anywhere. For that purpose, it is necessary to use a display element with low power consumption and make the power supply compact. Further, it is preferable to adopt a reflection type which does not require a light source in order to make the apparatus lighter and thinner. Most preferably, a reflective liquid crystal display element having a memory property is mounted.

However, it has been found that the reflection type liquid crystal display element having the memory property has a peculiar drawback that the drive response speed is slow, and the above system depends on how to overcome this drawback. .

[0006]

Heretofore, when referring to display devices using liquid crystal display elements, they use low molecular liquid crystals. For this reason, the type using a glass substrate has a problem that, when the substrate is large, it is difficult to uniformly apply a rubbing orientation treatment and the substrate is easily broken. Further, the viewing angle of the display unit was narrow, and it was difficult to read the displayed information. Furthermore, when a shock or pressure is applied to the display panel itself, the orientation is disturbed, and image information cannot be read.In addition, the liquid crystal itself has no memory property, and it is necessary to constantly supply a constant power during display, and power consumption is reduced. Was also large.

In view of the above problems, it is an object of the present invention to combine a reflective liquid crystal display element having a memory effect with various advantages with other display means capable of covering the drawbacks, thereby providing a wide variety of devices. An object of the present invention is to provide an information display device capable of realizing display of information. The present invention proposes an information display device that is put to practical use as a portable electronic book and that also considers the electronic information supply mode (bending system).

[0008]

In order to achieve the above object, an information display device according to the present invention comprises display means for displaying information in a plurality of different modes, and at least one display means has a memory function. It consisted of a reflection type liquid crystal display element. Further, another information display device according to the present invention,
Display means for displaying information in a plurality of different systems are stacked, and at least the display means located at the uppermost layer is constituted by a reflective liquid crystal display element having a memory property.

As described above, since the information display device according to the present invention includes a plurality of display means for displaying information in different modes, it is possible to display various information utilizing the advantages of each mode. In particular, when at least one display means is configured by a reflective liquid crystal display element having a memory property, the advantage of the display element, that is, a wider display area, a thinner and lighter display screen can be achieved, and power saving It becomes possible.

In particular, a reflection type liquid crystal display element having a memory function does not require power for maintaining a display, so that a still image display is provided, and a moving image portion is provided by another display means having good responsiveness. , It is possible to obtain a preferable information display device utilizing the characteristics of each display means.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the information display device according to the present invention will be described below with reference to the accompanying drawings.

(First Embodiment, see FIGS. 1 and 2) As shown in FIG. 1, an information display device 1A according to a first embodiment has
A reflective first display element 2 having a memory function using a cholesteric liquid crystal or a chiral nematic liquid crystal as a display medium, and a TFT having a display area in a part of the screen of the first display element 2 (Thin Film
Transistor) and a second display element 3 which is a liquid crystal display element. The main body substrate 5 has a built-in power supply and control unit, and a power supply switch 11 and five screen selection switches 12 are provided below the power supply and the control unit.

As shown in FIG. 2, the second display element 3 and the spacer 6 are arranged on the main body substrate 5, and the first display element 2 is stacked thereon. The structure of the first display element 2 and its driving method will be described below. The second display element 3 employs the same structure and driving method as the conventionally known TFT liquid crystal display element.

As shown in FIG. 1, the display mode is such that a relatively fixed still image requiring little movement is displayed on the first display element 2, and a moving image for rewriting the screen at high speed is displayed on the second display element 3. Is displayed. When the second display element 3 is set to the display state, the overlapping part of the first display element 2 is set to a transparent state, and the image of the second display element 3 is displayed through the transparent part. When the second display element 3 is turned off, the entire screen can be displayed only by the first display element 2.

Although a TFT-driven liquid crystal display element has a quick response and is suitable for displaying moving images, it is difficult to produce a large-sized screen, which leads to an increase in cost. Therefore, in the first embodiment, a large screen is formed of a cholesteric liquid crystal or a chiral nematic liquid crystal that is easy to manufacture, and the advantages of the elements 2 and 3 are utilized to complement each other's disadvantages. Larger size, lower cost, and power saving have been achieved.

(Second Embodiment, See FIGS. 3 and 4) An information display device 1B according to a second embodiment has a first display element 2, a second display element 3, and a main body substrate similar to those of the first embodiment. 5
The screen configuration is as shown in FIG.

However, in the second embodiment, the second display element 3 is fitted into a part of the screen of the first display element 2, as is apparent from FIG. Therefore, as in the first embodiment, the entire screen cannot be displayed as the screen of the first display element 2 if the second display element 3 is turned off, but the elements 2 and 3 are completely separated without being stacked. Therefore, it can be manufactured at a lower cost than the first embodiment. Further, in the first embodiment, when an image is displayed on the second display element 3, it is necessary to set the overlapping portion of the first display element 2 in a transparent state, but this is not necessary in the second embodiment. The display mode and the operation and effect in the second embodiment are the same as those in the first embodiment.

Third Embodiment An information display device 1C according to a third embodiment includes a first display element 2, a second display element 3, and a main substrate 5 similar to the first embodiment. The screen configuration is the same as that of FIG.

However, in the third embodiment, as apparent from FIG. 5 showing the cross-sectional structure, the portion 2a where the first display element 2 overlaps the second display element 3 is filled with a transparent resin or the like. The method of use and the effects of the third embodiment are the same as those of the second embodiment.
This is the same as the embodiment.

(Fourth Embodiment, See FIG. 6) An information display apparatus 1D according to a fourth embodiment includes a first display element 2, a second display element 3, and a main substrate 5 similar to those of the first embodiment. The screen configuration is the same as that of FIG.

However, in the fourth embodiment, as is apparent from FIG. 6 showing the cross-sectional structure, the second display element 3 can be attached to and detached from the back side of the main body substrate 5 together with the substrate portion 7 having its built-in control section. It has been. Therefore, in the fourth embodiment, the second display element 3 can be detached from the main substrate 5 and an image can be displayed only on the second display element 3 independently of the first display element 2. The method of use, operation, and effects of the fourth embodiment are the same as those of the first embodiment.

The attachment / detachment mechanism for the second display element 3 can employ various configurations. For example, as shown in FIG.
A holding projection 8 and a slider 9 are provided on the back surface of the main body substrate 5,
The second display element 3 may be attached and detached according to the left and right sliding of the slider 9.

(Fifth Embodiment, see FIG. 7) The fifth embodiment is configured as an electronic book 20A, in which a first display element 21 and a second display element 22 are provided on a main body substrate 25, and a power supply is provided. Switch 26, multiple operation buttons 27
Is provided. The first display element 21 includes the first to the first elements.
Similar to the first display element 2 of the fourth embodiment, this is a reflection type liquid crystal display element having a memory function using a cholesteric liquid crystal or a chiral nematic liquid crystal as a display medium. As the second display element 22, an organic EL (electro luminescence) display element is used. As is well known, the organic EL display element is of a light emitting type and has a very fast driving response speed.

As shown in FIG. 2, the first and second display elements 21 and 22 have a laminated structure in which a second display element 22 is disposed below the first display element 21 and the display mode is the first display element 21.
This is the same as the embodiment.

In the fifth embodiment, the first display element 2
1 mainly displays character information of a book by utilizing its memory property. The second display element 22 makes use of its high-speed response,
It is used as a fast-forward display similar to the operation of flipping pages of a book. Of course, a moving image may be displayed.

In the fifth embodiment, other than the organic EL display element, various high-speed display elements can be used as the second display element 22. For example, PDP (plasma display panel), FED
(Field emission display), LED (light emitting diode), and FIL (fluorescent light emitting display element).
Of course, a TFT driven liquid crystal display element may be used.

(Sixth Embodiment, see FIG. 8) The sixth embodiment is configured as an electronic book 20B having the same configuration as that of the fifth embodiment.
The second display element 22 having two small areas with respect to the display element 21
a, 22b. The second display element 22a,
Reference numeral 22b denotes a TFT-driven liquid crystal display element having high-speed response, an organic EL, a PD similar to the second display element 22.
Any of P, FED, LED, FIL, etc. is used.

(Seventh Embodiment, see FIG. 9) The seventh embodiment is configured as a two-page spreadable electronic book 30. That is, it has two panels 35a and 35b that can be folded at the central portion 36. Left panel 35a
Similar to the first display elements 2 and 21, there is provided a reflective liquid crystal display element 31 having a memory function using a cholesteric liquid crystal or a chiral nematic liquid crystal as a display medium, a power switch 33, a plurality of operation buttons 34, and control thereof. Part is provided. On the right panel 35b, similarly to the second display element 22, a second display element 32 using a TFT liquid crystal as a display medium and its control unit are provided.

In the seventh embodiment, the first display element 3
The first display area is configured to be larger than the display area of the second display element 32, and the usage thereof is the same as that of the fifth embodiment. Therefore, the first and second display elements 31, 32
It is possible to display information taking advantage of the features described above. The second
As the display element 32, similarly to the second display element 22, a light-emitting display element having a high-speed response, such as EL, PDP, FED, LED, or FIL, can be used.

(Eighth Embodiment, see FIG. 10) This eighth embodiment is configured as a bulletin board 40. Here, the first display element 41 is provided on the main body substrate 45 to form a large-area character information display area, and the second display element 42
To provide a small area image information display area. The first display element 41 is a reflective liquid crystal display element having a memory function using a cholesteric liquid crystal or a chiral nematic liquid crystal as a display medium, like the first display element 21 of the fifth embodiment. As the second display element 42, an organic EL display element is used similarly to the second display element 22. The stacked structure of the first and second display elements 41 and 42 is arranged such that the display of the element 42 does not overlap the display of the element 41 as shown in FIGS.

Normally, it is considered that the image information has a larger amount of information than the text information, and it is easier for the viewer to identify the information at a glance. Therefore, when character information and image information are mixed on one screen, the second display element 42 capable of high-speed driving is used.
It is preferable to display the image information on the first display element 41 after fast-displaying the image information and determining the image to be displayed.

As the second display element 42, various display elements of the light emitting type described in the fifth and sixth embodiments can be used other than the TFT liquid crystal.

(Configuration of Liquid Crystal Display Element) Here, the first
FIG. 11 shows an example of a liquid crystal display element that can be used as the display elements 2, 21, 31, and 41. In this liquid crystal display element, a red display layer 111R for performing display by switching between red selective reflection and a transparent state is disposed on a base film 118 via a light absorber 119, and green selective reflection and a transparent state are provided thereon. Green display layer 1 that performs display by switching
11G, and a blue display layer 111B on which display is performed by selectively reflecting blue and switching between transparent states.
Are laminated.

Each display layer 111R, 111G, 111B
Has a structure in which a resin columnar structure 115 and a liquid crystal 116 are sandwiched between transparent substrates 112 on which transparent electrodes 113 and 114 are formed, respectively. Further, an orientation control film or an insulating film (not shown) may be provided on the transparent electrodes 113 and 114.

The transparent electrodes 113 and 114 are respectively connected to a drive circuit 120, and a predetermined pulse voltage is applied between the transparent electrodes 113 and 114 by the drive circuit 120. In response to the applied voltage, the display is switched between a transparent state in which the liquid crystal 116 transmits visible light and a selective reflection state in which visible light is selectively reflected.

The transparent electrodes 113 and 114 provided on each of the display layers 111R, 111G and 111B are composed of a plurality of strip electrodes which are arranged in parallel with a fine interval therebetween. They are opposed so as to be at right angles. Current is sequentially applied to these upper and lower strip electrodes. That is, display is performed by sequentially applying a voltage to each liquid crystal 116 in a matrix. By performing such a matrix drive for each display layer sequentially or simultaneously, a full-color image is displayed on the liquid crystal display element.

More specifically, in a liquid crystal display device in which a cholesteric liquid crystal or a chiral nematic liquid crystal is sandwiched between two substrates, display is performed by switching the liquid crystal state between a planar state and a focal conic state. When the liquid crystal is in the planar state, assuming that the helical pitch of the cholesteric liquid crystal is P and the average refractive index of the liquid crystal is n, light of wavelength λ = P · n is selectively reflected. In the focal conic state, when the selective reflection wavelength of the cholesteric liquid crystal is in the infrared light range, it is scattered, and when it is shorter than that, it transmits visible light. Therefore, by setting the selective reflection wavelength in the visible light region and providing a light absorbing layer on the side opposite to the observation side of the element indicated by arrow A, the display of the selective reflection color in the planar state and the display of black in the focal conic state are achieved. Will be possible. In addition, by setting the selective reflection wavelength in the infrared light range and providing a light absorption layer on the side opposite to the observation side of the element, light in the infrared light range is reflected in the planar state, but the wavelength in the visible light range is reflected. Is transmitted, so that a black display and a white display due to scattering in the focal conic state are possible.

By the way, if the first threshold voltage for untwisting the liquid crystal exhibiting the cholesteric phase is Vth1,
After the voltage Vth1 has been applied for a sufficient time, the voltage becomes lower than a second threshold voltage Vth2 which is lower than the first threshold voltage Vth1, and a planar state is established. Further, when a voltage of Vth2 or more and Vth1 or less is applied for a sufficient time, a focal conic state is established. These two states are stable even after the voltage application is stopped. It is also known that there is a state where these two states are mixed, and it is possible to display a halftone, that is, display a gradation.

Since the liquid crystal exhibiting a cholesteric phase has a memory characteristic capable of maintaining a display state even when no voltage is applied, a display element partitioned into a large number of pixels is driven by a simple matrix drive to obtain a desired image or character. Can be displayed. However, since this type of liquid crystal has a hysteresis characteristic, the display state is different even with the same driving voltage due to the state before the liquid crystal.

In view of the above, in the normal display mode, the liquid crystal constituting all the pixels is simultaneously reset to a focal conic state which requires a long time for selection, and thereafter, each pixel is constituted. A selection signal is sequentially applied to the liquid crystal to select the display state of the liquid crystal constituting all the pixels. According to this driving method, all the pixels are simultaneously reset to the focal conic state, so that the long selection time required to select the focal conic state is required only once for one screen. As a result, the rewriting speed is improved when simple matrix driving is performed.

(Full Color Display) Each display layer 111R, 1
In the liquid crystal display element in which 11G and 111B are stacked, the blue display layer 111B and the green display layer 111G are set in a transparent state in which liquid crystals are in a focal conic arrangement, and the red display layer 111 is formed.
By setting R to a selective reflection state in which the liquid crystal is in a planar arrangement, a red display can be performed. Further, the blue display layer 111B is set in a transparent state in which the liquid crystal is in a focal conic arrangement, and the green display layer 111G and the red display layer 11B are arranged.
By setting 1R to a selective reflection state in which the liquid crystal has a planar arrangement, yellow display can be performed. Similarly, by appropriately selecting the state of each display layer between a transparent state and a selective reflection state, red, green, blue, white, cyan,
Magenta, yellow, and black displays are possible. Further, by selecting an intermediate selective reflection state as the state of each display layer, an intermediate color can be displayed, and the display layer can be used as a full-color display element.

(Drive Circuit and Drive Method for Liquid Crystal Display Element)
Since the pixel configuration in each display layer of the liquid crystal display element is a simple matrix, as shown in FIG.
1, R2 to Rm and an m × n matrix of signal electrodes C1, C2 to Cn. The pixel at the intersection of the scanning electrode Ra and the signal electrode Cb (a and b are natural numbers satisfying a ≦ m and b ≦ n) is defined as LCa-b. These electrode groups are respectively a scan drive IC 121 and a signal drive IC 1
22 are connected to the output terminals of these ICs.
A scanning voltage and a selection voltage are applied from 21 and 122 to each electrode.

The driving circuit of the liquid crystal display element is not limited to the driver having the matrix configuration, but the signal driving IC 12 is provided for each line of the scanning driving IC 121.
The image data may be transferred serially from the second through the line latch memory. In this case, the scan drive IC 121 is not line-compatible, but needs to be for serial use, and the cost of the driver is low.

In the liquid crystal display device, the display state of the liquid crystal is a function of the applied voltage and the pulse width. When a pulse voltage having a constant width is applied to the liquid crystal after first resetting each liquid crystal to the focal conic state showing the lowest Y value (luminous reflectance), the display state becomes as shown in FIG. Changes. In FIG. 13, the vertical axis indicates the Y value, and the horizontal axis indicates the applied voltage. When the pulse of the voltage Vp is applied, the planar state showing the highest Y value is selected, and the voltage Vf
Is applied, the focal conic state showing the lowest Y value is selected. When an intermediate voltage is applied, a state in which the planar state and the focal conic state exhibiting an intermediate Y value are mixed is selected, and halftone display becomes possible.

FIGS. 14A and 14B show waveforms (a) and (b) of the pulse voltage applied to the liquid crystal of the test cell prototyped by the present inventors. Here, only the selection signal is applied from the signal electrode during scanning with respect to only one pixel. The voltage of the reset signal is 50 V, the pulse width (reset time) is 200 msec at the wavelength (a), and 50 msec at the wavelength (b).
c. Then, a selection signal for setting the liquid crystal to the planar state was applied at a voltage of 110 V for 5 msec. Although 110 V is used here, the value is not limited to this value, and another value can be taken depending on the material, thickness, and pulse width of the voltage of the liquid crystal.

As shown in the waveform (a), when the reset signal is applied for 200 msec, the selection signal is applied regardless of whether the state of the liquid crystal before reset is the planar state or the focal conic state. A good planar state was obtained, and gradation expression when the voltage value of the selection signal was changed was also possible. On the other hand, as shown in the waveform (b), when the reset signal was applied for 50 msec, the liquid crystal was not always reset sufficiently, and the Y value when the liquid crystal was set to the planar state thereafter varied.

It has been found from the above experiments that the longer the reset signal application time is, the less likely it is to be affected by the state before rewriting, and that if it is sufficiently long, it can be rewritten to a desired display state regardless of the state before rewriting. It is. In other words, by applying the reset signal for a sufficiently long time,
No longer affected by the previous state. In the waveform (a), it was found that the display time of about 4 gradations was possible with the application time of the reset signal being 200 msec.
By applying a reset signal of c or more, there is no difference in the selected display state due to the difference in the initial state, and a display of four or more gradations is possible.

FIG. 15 shows a drive / image signal processing circuit adapted to rewrite image data. The scan drive IC 121 and the signal drive IC 122 are connected to the liquid crystal display element, and these ICs 121 and 122 are driven by control signals from the scan controller 123 and the signal controller 124, respectively. Image data to be newly displayed is input from the memory 126 to the signal controller 124, but is converted into a selection signal by the image data conversion means 125 before that.

FIG. 16 shows a circuit configuration in which only a portion changed when information is rewritten can be partially rewritten. Since the first liquid crystal display element has memory characteristics, partial rewriting is possible.

First, the current image data is stored in the image memory 1. The image data to be newly displayed is stored in the image memory 2. Line memory 1 has image memory 1
, Data per scanning electrode is read out and stored. In addition, data is similarly read from the image memory 2 and stored in the line memory 2. This line memory 1,
2 are compared by a comparator, here a comparator 141, and the line numbers that do not match are compared with the address storage
2 is stored. In this way, only the part that changes from the current image is extracted for each scanning electrode, and is set as a rewriting target.

A predetermined time is set in advance in a time counter built in the controller 124, and when this time has elapsed, the scanning controller 123 and the signal controller 124 refer to the address stored in the address storage means 142. Then, the control signal is sent to the scan driving IC 12 so that only the liquid crystal on the corresponding scan electrode is rewritten.
1. Output to the signal drive IC 122. As a result, the scanning drive IC 121 and the signal drive IC 122 drive only the liquid crystal to be rewritten. According to such a driving method, only the portion to be rewritten can be rewritten, and display can be performed faster than rewriting the entire screen.

(Distribution control of information on screen, see FIG. 17) Next, as an example of the control method of the information display device according to the present invention, a part of information displayed on the first display element (first screen) Is displayed on the second display element (second screen) with reference to FIG. It should be noted that the first display element used here is provided with a well-known mechanism capable of determining the position by irradiating light from a light pen. For the position determination, a touch sensor can be used.

First, the first and second screens are reset in step S1, and when a display request for the first screen is confirmed in step S2, information is written on the first screen in step S4 (display state (b)). reference). Next, when the display request on the second screen is confirmed in step S5, the user specifies the area of the information to be moved with the light pen in step S6 (see the display state (c)). In step S7, the information of the designated area is transferred to the second screen, and in step S8, the information is written on the second screen. If a full reset request is confirmed in step S9, step S1 is executed to display the next screen.
Then, the whole screen is reset. Steps S3 and S10 are periods during which information is displayed on the screen.

(Other Embodiments) The information display device according to the present invention is not limited to the above embodiments, but can be variously modified within the scope of the invention.

In particular, the screen configuration of the information display device, its use method, and the display mode are various, and the most appropriate control method may be adopted.

[Brief description of the drawings]

FIG. 1 is a front view showing a first embodiment of an information display device according to the present invention.

FIG. 2 is a schematic sectional view of the first embodiment.

FIG. 3 is a front view showing a second embodiment of the information display device according to the present invention.

FIG. 4 is a schematic sectional view of the second embodiment.

FIG. 5 is a schematic sectional view of a third embodiment of the information display device according to the present invention.

FIG. 6 is a schematic sectional view of a fourth embodiment of the information display device according to the present invention.

FIG. 7 is a front view showing a fifth embodiment of the information display device according to the present invention.

FIG. 8 is a front view showing a sixth embodiment of the information display device according to the present invention.

FIG. 9 is a front view showing a seventh embodiment of the information display device according to the present invention.

FIG. 10 is a front view showing an eighth embodiment of the information display device according to the present invention.

FIG. 11 is a sectional view showing an example of a liquid crystal display element used as a first display element in each of the embodiments.

FIG. 12 is a block diagram showing a matrix drive circuit of the liquid crystal display element.

FIG. 13 is a graph showing a relationship between a voltage applied to a selection signal and a Y value in the matrix driving circuit.

FIG. 14 is a chart showing a voltage waveform experimentally applied to a test cell of the liquid crystal display element.

FIG. 15 is a block diagram showing a driving / image processing circuit of the liquid crystal display element.

FIG. 16 is a block diagram showing another example of the driving / image processing circuit.

FIG. 17 is a flowchart illustrating an example of a control method of the information display device according to the present invention.

[Explanation of symbols]

 1A, 1B, 1C, 1D Information display device 2 First display element 3 Second display element 20A, 20B, 30 Electronic book 21, 31 First display element 22, 22a, 22b, 32 Second display Element 40: bulletin board 41: first display element 42: second display element

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideo Hotomi 2-13-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. (reference) 2H089 HA22 HA28 LA09 RA05 RA11 TA12 2H091 FA16Z FD06 GA13 HA07 HA11 LA15 5C094 AA51 AA56 BA03 BA09 BA21 BA27 BA43 BA49 CA19 DA02 DA03 DB02 DB05

Claims (8)

[Claims] 1. An information display apparatus comprising: display means for displaying information in a plurality of different modes, wherein at least one display means is a reflective liquid crystal display element having a memory property. 2. A display device comprising: a panel having a reflective liquid crystal display element having a memory property; and a panel having other display means, wherein the display area of the former display element is larger than the display area of the latter display means. 2. The information display device according to claim 1, wherein the information display device also has a large value. 3. An information display, wherein display means for displaying information in a plurality of different modes are stacked, and at least the display means provided on the uppermost layer is a reflective liquid crystal display element having a memory property. apparatus. 4. The information display device according to claim 1, wherein a total display area of the reflective liquid crystal display element having a memory property is larger than a total display area of other display means. 5. The information display apparatus according to claim 1, wherein display means other than the reflective liquid crystal display element having a memory function is detachable from the apparatus main body. 6. The information display device according to claim 1, wherein a moving image is displayed on display means other than the reflective liquid crystal display element having a memory function. 7. The information display device according to claim 1, wherein the display means other than the reflective liquid crystal display element having a memory property is a light emitting display element. 8. The information display device according to claim 3, wherein at least a liquid crystal material of the display element does not exist on a display area of a display unit other than the reflective liquid crystal display element having a memory function.