JP2009244345A - Electronic paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve inexpensive electronic paper which has an illegal duplication preventing function, and reduces risk of information leakage by a low power consumption and a simple configuration, and prevents occurrence of malfunction. <P>SOLUTION: The electronic paper includes: a display screen 10: display driving parts 28, 29, 30 for displaying and/or erasing images; fraud prevention parts 32, 33 for detecting first operation and controlling the display driving parts so as to erase a displayed image when the first operation is detected; and a control part 32 for bringing the fraud prevention parts to an operation state when an image to be display part is an image disabled from being disclosed, and bringing the fraud prevention parts to an operation stop state when the image to be displayed is an disclosable image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic paper having display memory characteristics, and more particularly to an electronic paper having a fraud prevention function for preventing unauthorized use of images whose images cannot be disclosed.

  In recent years, development of electronic paper has been actively promoted in companies and universities. As application fields in which electronic paper is expected to be used, various application forms such as electronic books, sub-displays for mobile terminal devices, and display units for IC cards have been proposed.

  Electronic paper generally has display memory characteristics, and can hold a display once written without a power source for a long time, and has low power consumption. Further, electronic paper has features such that it is easy to see with a reflective display, is thin and flexible, and is easy to carry.

  Since electronic paper has the same characteristics as the above paper, it can be easily copied by reading the display content with a copying machine, a scanner, or the like, as with paper. Therefore, when confidential information is displayed on the electronic paper, there is a problem of illegal copying in which the displayed confidential information is illegally copied and taken out. In the case of paper, various preventive measures for preventing such unauthorized copying have been proposed, and various measures for preventing unauthorized copying of electronic paper have also been proposed.

  Patent Document 1 is a digital content display device that uses a device such as liquid crystal or electronic paper. An image that cannot be copied is displayed with light in the visible wavelength band and with light in the invisible wavelength band. Thus, it is described that halation is generated to prevent image duplication when an image is duplicated using an optical means such as an image scanner or a digital camera.

  In Patent Document 2, a detection mechanism that detects light moving at a constant speed in a certain direction is provided in electronic paper, and copying is prevented by erasing the displayed image when a scanning operation in a copying machine or a scanner is detected. Electronic paper to be described.

JP 2007-79062 A JP 2004-233657 A International Publication WO2007 / 110949A1

  The digital content display device described in Patent Document 1 requires light emitting means for generating light in the visible and invisible wavelength bands, and has low power consumption that includes electronic paper without a power source or a small power source (battery) It cannot be applied to electronic paper.

  The electronic paper described in Patent Document 2 has a problem that it is necessary to provide a large number of optical sensors in order to detect a scanning operation, and the detection mechanism is complicated and expensive. In addition, a large number of optical sensors are always in an operating state, and there is a problem that power consumption increases. Further, when the optical sensor is masked with a tape or the like, there is a problem that the detection mechanism cannot detect the scanning operation, and unauthorized copying can be easily performed.

  Also, since electronic paper can be easily carried in the same way as paper, there is a risk of taking it outside the company while displaying confidential information and personal information (such as e-mails) that you do not want the third party to see. There is a security problem. However, the prior art including the cited references 1 and 2 does not take any measures against such illegal take-out.

  On the other hand, if it is not unauthorized use, the electronic paper is also required to securely hold the displayed information. In other words, a malfunction that deletes the displayed image is not allowed even though it is not an unauthorized use operation. If the displayed image is erased due to a malfunction, the convenience is greatly impaired.

  An object of the present invention is to realize low-cost electronic paper that has an illegal copy prevention function, can reduce the risk of information leakage with a simple configuration with low power consumption, and does not cause malfunction.

  In order to achieve the above object, the electronic paper according to the present invention includes a fraud prevention unit that detects an unauthorized use operation of an image displayed on the display screen and erases the image displayed on the display screen when the unauthorized use operation is detected. When the image to be displayed is an image that cannot be disclosed, the fraud prevention unit is set in an operating state, and when the image to be displayed is an image that can be displayed, the fraud prevention unit is set in an operation stopped state.

  According to the present invention, in the case of an image that can be disclosed, the fraud prevention unit is set in an operation stop state, so that it is not necessary to operate an optical sensor or the like for detecting an unauthorized use operation, thereby reducing power consumption. It is possible, and the power consumption can be practically zero. When displaying images that cannot be disclosed, it is necessary to operate optical sensors to detect unauthorized use. However, in actual use of electronic paper, the proportion of images that cannot be disclosed is not large and effective. Power consumption is small. Further, in the case of an image that can be disclosed, the fraud prevention unit is set in an operation stop state, so that it is possible to prevent a malfunction in which an image is erased by erroneously determining an unauthorized use operation even though it is not an unauthorized use operation. This increases the reliability when displaying a publicly available image.

  In general, it is difficult to completely prevent illegal copying or fraudulent takeout of electronic paper. The higher the reliability of prevention, the more complicated the prevention mechanism, which not only increases costs and power consumption, but also reduces convenience. To do. The present invention is intended to prevent unauthorized operation to some extent with a simple mechanism. However, in the case of a simple mechanism, erroneous operation is easily determined by erroneously determining an unauthorized use operation. An unpublishable image may be erased due to a malfunction. However, considering that the image cannot be disclosed, a certain degree of malfunction is often permitted. On the other hand, in the case of a publishable image, erasure of an image due to a malfunction is often not allowed, but according to the present invention, the erasure of a publishable image hardly occurs.

  The fraud prevention unit in the operating state deletes the displayed image by controlling the display driving unit when the fraudulent use operation is detected. Electronic paper takes a long time to write for image display, but can be erased in a short time. Therefore, unauthorized use can be prevented by performing an erase operation when an unauthorized use operation is detected. In order to perform erasing while the external power supply to the electronic paper is cut off, a small-capacity auxiliary battery is provided in the electronic paper so that power for image erasing operation can be supplied. Further, after erasure, an erasure message and a redisplay operation guide may be displayed.

  Various mechanisms for detecting an unauthorized use operation in the fraud prevention unit are possible. For example, an optical sensor group including a plurality of optical sensors having different sensitivities for detecting light incident on the same part of the electronic paper is provided, and an unauthorized operation is detected by a combination of outputs of the plurality of optical sensors in the optical sensor group. For example, the sensitivity of at least one first light sensor is set so as to detect a state where the electronic paper is placed in a dark environment where an image on which electronic paper is displayed cannot be read, and a state where the light sensor is masked with a tape or the like. . Further, the sensitivity of at least one other second light sensor is set so as to detect strong light from a copying machine or the like. If the first photosensor is in an ON state that exceeds the first threshold level and the second photosensor is in an OFF state that does not reach the second threshold level, the display image is maintained because it is considered to be in a normal environment. If the first optical sensor is in the OFF state, it is considered that the optical sensor is masked with a tape or the like, and the electronic paper is put in a bag or the like. If the second optical sensor is in the ON state, it is considered that copying is performed by a copying machine or the like, and the image is erased. In this way, copying with a copying machine or the like can be prevented, and in this case, copying can also be prevented by performing an act of disabling the function of the fraud prevention unit by masking the optical sensor with a tape or the like. Also, copying can be prevented when electronic paper is put in a bag or the like and taken outside.

  When detecting light incident on different parts of electronic paper using multiple photosensors with different sensitivities, masking one of them will disable the function of the fraud prevention unit. It is desirable to detect light incident on the same part of the electronic paper.

  In addition, when the optical sensor group is provided in one place of the electronic paper, if the place is scanned last by a copying machine or the like, the image will be erased after the copying is completed. It is desirable to provide a plurality of optical sensor groups at a plurality of locations on the electronic paper, for example, in the vicinity of two corners on the opposite corner of the electronic paper.

  In addition, as a mechanism for detecting an unauthorized use operation in the fraud prevention unit, a sensor for detecting whether the display screen is facing upward or downward is provided, and an unauthorized use operation can be performed when the display screen is facing downward. You may make it determine with there. In normal use, the electronic paper is arranged with the display screen facing upward or the display screen is in the vertical direction. When copying electronic paper with a copying machine, the display screen of the electronic paper is arranged facing downward, and this is detected to erase the image.

  Furthermore, after an image is erased due to use by an incorrect method of the user or a malfunction of the fraud prevention unit, the user may request to display an image that cannot be disclosed again. For this purpose, it is necessary to store in the image code storage unit the code number of the image indicating which image has been deleted. In addition, it is necessary to confirm that the user who has requested redisplay is a legitimate right holder who has the right to use an image that cannot be disclosed. For this reason, an authentication data storage unit for storing authentication information indicating that the user is a right holder is provided, and after confirming that the user is a right holder, the code number of the unpublishable image stored in the image code storage unit is set. read out. The code number of the read image is output to the electronic paper writing device, and the corresponding image is written on the electronic paper.

  According to the present invention, it is possible to realize an electronic paper having an illegal copy prevention function that is excellent in effective convenience, low power consumption, and low cost.

  One of the leading methods for electronic paper is cholesteric liquid crystal. Cholesteric liquid crystal has excellent characteristics such as semi-permanent display retention (memory property), vivid color display, high contrast, and high resolution. Hereinafter, embodiments in which electronic paper using cholesteric liquid crystal is taken as an example will be described. However, the present invention is not limited to this.

  First, the principle of display using cholesteric liquid crystal will be described. Cholesteric liquid crystals are sometimes referred to as chiral nematic liquid crystals, and by adding a relatively large amount (several tens of percent) of chiral additives (chiral materials) to nematic liquid crystals, the molecules of nematic liquid crystals are helical. It is a liquid crystal that forms a cholesteric phase.

  FIG. 1 is a diagram for explaining a state of a cholesteric liquid crystal. As shown in FIGS. 1A and 1B, the display element 10 using cholesteric liquid crystal has an upper substrate 11, a cholesteric liquid crystal layer 12, and a lower substrate 13. A cholesteric liquid crystal has a planar state that reflects incident light as shown in FIG. 1A and a focal conic state that transmits incident light as shown in FIG. The state is stably maintained even in the absence of an electric field.

  In the planar state, light having a wavelength corresponding to the helical pitch of the liquid crystal molecules is reflected. The wavelength λ at which the reflection is maximum is expressed by the following formula from the average refractive index n of the liquid crystal and the helical pitch p.

λ = n · p
On the other hand, the reflection band Δλ varies greatly depending on the refractive index anisotropy Δn of the liquid crystal.

  In the planar state, incident light is reflected, so that a “bright” state, that is, white can be displayed. On the other hand, in the focal conic state, by providing a light absorption layer under the lower substrate 13, light transmitted through the liquid crystal layer is absorbed, so that a "dark" state, that is, black can be displayed.

  Next, a method for driving a display element using cholesteric liquid crystal will be described.

  FIG. 2 shows an example of voltage-reflection characteristics of a general cholesteric liquid crystal. The horizontal axis represents the voltage value (V) of the pulse voltage applied with a predetermined pulse width between the electrodes sandwiching the cholesteric liquid crystal, and the vertical axis represents the reflectance (%) of the cholesteric liquid crystal. The solid curve P shown in FIG. 2 shows the voltage-reflectance characteristics of the cholesteric liquid crystal whose initial state is the planar state, and the broken curve FC shows the voltage-reflectance characteristics of the cholesteric liquid crystal whose initial state is the focal conic state. .

  In FIG. 2, when a predetermined high voltage VP100 (for example, ± 36 V) is applied between the electrodes to generate a relatively strong electric field in the cholesteric liquid crystal, the helical structure of the liquid crystal molecules is completely unwound and all molecules are Becomes homeotropic according to the direction of the electric field. Next, when the liquid crystal molecules are in a homeotropic state, the applied voltage is rapidly decreased from VP100 to a predetermined low voltage (for example, VF0 = ± 4 V), and the electric field in the liquid crystal is suddenly reduced to almost zero. The spiral axis is perpendicular to the electrode, and a planar state in which light according to the spiral pitch is selectively reflected is obtained.

  On the other hand, when a predetermined low voltage VF100b (for example, ± 24V) is applied between the electrodes to generate a relatively weak electric field in the cholesteric liquid crystal, the spiral structure of the liquid crystal molecules cannot be completely solved. In this state, when the applied voltage is suddenly lowered from VF100b to the low voltage VF0 and the electric field in the liquid crystal is suddenly made substantially zero, or a strong electric field is applied and the electric field is gently removed, The helical axis is parallel to the electrode, and a focal conic state in which incident light is transmitted is obtained.

  In addition, when an electric field having an intermediate strength is applied and the electric field is rapidly removed, a planar state and a focal conic state are mixed, and halftone display is possible.

  Here, in the curve P shown in FIG. 2, within the broken line frame A, the reflectance of the cholesteric liquid crystal can be lowered by increasing the ratio of the focal conic state as the voltage value of the applied voltage pulse is increased. Further, in the curves P and FC shown in FIG. 2, within the broken line frame B, the reflectance of the cholesteric liquid crystal can be lowered by increasing the ratio of the focal conic state as the applied voltage value is lowered.

  In order to display a halftone, area A or area B is used. When the area A is used, after a pixel is initialized and brought into a planar state, a voltage pulse between VF0 and VF100a is applied to partially bring the focal conic state. Further, when the region B is used, a pixel is initialized to a focal conic state, and then a voltage pulse between VF100b and VP0 is applied to partially make a planar state.

  Patent Document 1 describes the configuration of a cholesteric liquid crystal display device. In the present application, reference is made to the description in Patent Document 1, and a description of the gradation driving method of the cholesteric liquid crystal display device is omitted.

  FIG. 3 is a diagram showing a configuration of the cholesteric liquid crystal display element 10 of the embodiment capable of full color display. As shown in FIG. 3, the display element 10 includes three panels, a blue panel 10 </ b> B, a green panel 10 </ b> G, and a red panel 10 </ b> R, stacked in order from the viewing side. The light absorption layer 17 is provided below the red panel 10R. The panels 10B, 10G, and 10R have the same configuration, but the panel 10B has a blue central wavelength of reflection (about 480 nm), the panel 10G has a green central wavelength of reflection (about 550 nm), and the panel 10R has a central wavelength of reflection. The liquid crystal material and the chiral material are selected so as to be red (about 630 nm), and the content of the chiral material is determined.

  FIG. 4 shows an example of reflection spectra in the planar state of the B display unit 10B, the G display unit 10G, and the R display unit 10R.

  Panels 10B, 10G, and 10R are driven by blue layer control circuit 18B, green layer control circuit 18G, and red layer control circuit 18R, respectively.

  FIG. 5 is a diagram showing a basic configuration of one panel 10A among the three panels 10B, 10G, and 10R constituting the display element 10 of FIG. The three panels 10B, 10G, and 10R have a substantially common configuration except for the reflection wavelength. The panel used in the embodiment will be described with reference to FIG.

  As shown in FIG. 5, the display element 10 </ b> A includes an upper substrate 11, an upper electrode layer 14 provided on the surface of the upper substrate 11, a lower electrode layer 15 provided on the surface of the lower substrate 13, and a seal. Material 16. The upper substrate 11 and the lower substrate 13 are arranged so that the electrodes face each other, and after sealing a liquid crystal material therebetween, they are sealed with a sealing material 16. A spacer is disposed in the liquid crystal layer 12 but is not shown. A voltage pulse signal is applied from the drive circuit 18 to the electrodes of the upper electrode layer 14 and the lower electrode layer 15, whereby a voltage is applied to the liquid crystal layer 12. A voltage is applied to the liquid crystal layer 12 to display the liquid crystal molecules in the liquid crystal layer 12 in a planar state or a focal conic state. As described above, the display element 10A has a memory property, and the planar state and the focal conic state are maintained even after the application of the pulse voltage is stopped.

  The upper substrate 11 and the lower substrate 13 are both translucent, but the lower substrate 13 of the panel 10R may be opaque. Although there exists a glass substrate as a board | substrate which has translucency, you may use film substrates, such as PET (polyethylene terephthalate) and PC (polycarbonate), besides a glass substrate.

  As a material for the electrodes of the upper electrode layer 14 and the lower electrode layer 15, for example, indium tin oxide (ITO) is representative, but other indium zinc oxide (IZO: Indium Zic Oxide), etc. It is possible to use a transparent conductive film.

  The transparent electrode of the upper electrode layer 14 is formed as a plurality of strip-shaped upper transparent electrodes parallel to each other on the upper substrate 11, and the transparent electrode of the lower electrode layer 15 is a plurality of strip-shaped parallel to each other on the lower substrate 13. Is formed as a lower transparent electrode. The upper substrate 11 and the lower substrate 13 are arranged so that the upper electrode and the lower electrode intersect when viewed from a direction perpendicular to the substrate, and pixels are formed at the intersection. An insulating functional film is formed on the electrode. The functional film is a thin film having a function of preventing a short circuit between the electrodes of the liquid crystal display element and improving the reliability of the liquid crystal display element as a gas barrier layer. If this thin film is thick, it is necessary to increase the drive voltage, and it becomes difficult to configure a drive circuit with a general-purpose STN driver. Conversely, if there is no thin film, a leakage current flows, which causes a problem that power consumption increases. Here, since the thin film has a relative dielectric constant of about 5 and is considerably lower than that of the liquid crystal, the thickness of the thin film is suitably about 0.3 μm or less.

This insulating thin film can be realized by a thin film of SiO ₂ or an organic film such as polyimide resin or acrylic resin known as an orientation stabilizing film.

  As described above, the spacers are arranged in the liquid crystal layer 12 so that the distance between the upper substrate 11 and the lower substrate 13, that is, the thickness of the liquid crystal layer 12 is constant. The spacer is generally a sphere made of a resin or an inorganic oxide, but it is also possible to use a fixed spacer having a substrate surface coated with a thermoplastic resin. The cell gap formed by this spacer is suitably in the range of 3.5 μm to 6 μm. If the cell gap is smaller than this value, the reflectance is lowered and the display is dark. On the other hand, if the cell gap is larger than this value, the driving voltage rises and driving by the general-purpose driver IC becomes difficult.

  The liquid crystal composition forming the liquid crystal layer 12 is a cholesteric liquid crystal obtained by adding 10 to 40% by weight (wt%) of a chiral material to a nematic liquid crystal mixture. Here, the addition amount of the chiral material is a value when the total amount of the nematic liquid crystal component and the chiral material is 100 wt%.

  As the nematic liquid crystal, various types of conventionally known liquid crystals can be used, but a liquid crystal material having a dielectric anisotropy (Δε) in the range of 15 to 50 is desirable. If the dielectric anisotropy is too lower than this range, the drive voltage will increase. Conversely, if the dielectric anisotropy is too higher than this range, the drive voltage itself will decrease, but the specific resistance will be reduced, particularly increasing the power consumption at high temperatures. However, the stability and reliability of the device are reduced, and image defects and image noise are likely to occur. If the dielectric anisotropy is 15 or more, the drive voltage is relatively low, and if it is 20 or more, the selection range of usable chiral materials is widened.

  The refractive index anisotropy (Δn) is preferably 0.18 to 0.24. If the refractive index anisotropy is smaller than this range, the reflectivity in the planar state is low, resulting in a dark display with insufficient brightness. If the refractive index anisotropy is larger than this range, the scattering reflection in the focal conic state is increased. In addition to a blurred display with insufficient purity and contrast, the viscosity increases and the response speed decreases. A lower viscosity can suppress voltage increase and contrast decrease at low temperatures.

  FIG. 6 is a diagram illustrating an overall configuration of the electronic paper according to the embodiment. The display element 10 is the cholesteric liquid crystal display panel described with reference to FIGS. 3 to 5 and has A4 size XGA specifications and has 1024 × 768 pixels. The power source 21 outputs a voltage of 3V to 5V, for example. Here, it is assumed that a small capacity battery is attached to the power source 21, and an erasing operation described later can be performed even if the power source 21 is not electrically connected. The boosting unit 22 boosts the input voltage from the power source 21 to 36V to 40V by a regulator such as a DC-DC converter. As this boost regulator, a dedicated IC is widely used, and the IC has a function of adjusting the boost voltage by setting a feedback voltage. Therefore, it is possible to change the boosted voltage by selecting a plurality of voltages generated by voltage division by a resistor and supplying the selected voltages to the feedback terminal.

  The voltage switching unit 23 generates various voltages by resistance division or the like. For switching between the reset voltage and the gradation write voltage in the voltage switching unit 23, an analog switch having a high withstand voltage may be used, but a simple switching circuit using a transistor may be used. The voltage stabilizing unit 24 desirably uses an operational amplifier voltage follower circuit in order to stabilize various voltages supplied from the voltage switching unit 23. It is desirable to use an operational amplifier having a strong characteristic against a capacitive load. In addition, the structure which switches an amplification factor by switching the resistance connected to an operational amplifier is widely known, and if this structure is used, the voltage output from the voltage stabilization part 24 can be switched easily.

  The original oscillation clock unit 25 generates a basic clock that is a basic operation. The frequency divider 26 divides the basic clock to generate various clocks necessary for the operation described later.

  The temperature sensor 27 detects the temperature of the display element 10. In the cholesteric liquid crystal display element, the speed of orientation change corresponding to voltage application changes according to the temperature, so the temperature is detected and the writing process is controlled.

  The control circuit 28 generates a common driver control signal and a segment driver control signal based on the basic clock, various clocks, and the image data D, and supplies the common driver 29 and the segment driver 30 together with the image data D.

  The common driver 29 drives 1024 scan lines, and the segment driver 30 drives 768 data lines. Since the image data given to each pixel of RGB is different, the segment driver 30 drives each data line independently. The common driver 29 drives the RGB lines in common. As a result, there can be obtained an advantage that the number of components can be reduced by using one common driver, but the common driver for each RGB panel so that the scan line of each RGB panel can be driven independently. It is also possible to provide.

  In this embodiment, a general-purpose binary output STN driver is used as the driver IC. Various general-purpose STN drivers can be used.

  The image data input to the segment driver 30 is 4-bit data D0-D3 obtained by converting a full-color original image into 4096 color data of 16 gradations of RGB using an error diffusion method. The gradation conversion is preferably performed by a method capable of obtaining high display quality, and a blue noise mask method or the like can be used in addition to the error diffusion method.

  The electronic paper control unit 32 includes an input interface 34 to which a control signal from the writing device is input and an unauthorized use detection sensor 33 described later, and controls the control circuit 28. At the time of writing, the electronic paper control unit 32 supplies the control circuit 28 with the panel control signal generated based on the control signal from the writing device and the image data D supplied via the input interface 34. An image code number and disclosure permission / inhibition information C are added to the image data D. A memory 31 accessible from the electronic paper control unit 32 may be provided, and the image data D and the disclosure possibility information C supplied via the input interface 34 may be stored together with the image code number. Here, even when the image data D is not stored, the memory 31 is provided, and the image code number and the disclosure possibility information C are stored. The electronic paper control unit 32 detects whether an unauthorized use operation has been performed based on the output of the unauthorized use detection sensor 33. In other words, the electronic paper control unit 32 and the unauthorized use detection sensor 33 constitute an unauthorized prevention unit.

  The control circuit 27 and the electronic paper control unit 32 can be realized separately or integrally with a microcomputer, FPGA, or the like.

  Since the control processing by the control circuit 28 for writing and erasing the image is described in Patent Document 3, etc., description thereof is omitted.

  FIG. 7 is a diagram illustrating a configuration example of the unauthorized use detection sensor 33 in the first embodiment. As illustrated in FIG. 7, the electronic paper 1 includes a display element 10 and a housing 50 that holds the display element 10 and circuit components. The unauthorized use detection sensor 33 includes optical sensor units 51 and 52 provided at two locations near the diagonal corner of the electronic paper 1, respectively. Here, two photosensor units are provided at two locations, but three or more photosensor units may be provided at three or more locations.

  As shown in the drawing, the optical sensor unit 52 includes a hole 54 provided in the surface 53 of the electronic paper 1 (the housing 50 or the display element 10) and two optical sensors 55- provided in the electronic paper 1. 1, 55-2. The hole 54 is preferably filled with a transparent resin to protect the inside. The two optical sensors 55-1 and 55-2 are arranged such that the optical axes are directed in different directions, and the optical axes intersect at the hole 54 portion. The two optical sensors 55-1 and 55-2 are arranged to detect light that has passed through the single hole 54. When the hole 54 is shielded, the two optical sensors 55 are disposed. No light enters -1 and 55-2 simultaneously. The two optical sensors 55-1 and 55-2 have different ON / OFF threshold levels. For example, the optical sensor 55-1 is turned on with light of 50 lux (lx) or more, and the optical sensor 55-2 is 2000 lx. Turns on with the above light.

  The optical sensor unit 51 has the same configuration as the optical sensor unit 52. Here, the optical sensors 55-1 and 55-2 of the optical sensor unit 51 are referred to as sensors A-1 and A-2, and the optical sensors 55-1 and 55-2 of the optical sensor unit 52 are referred to as sensors B-1 and B-2. -2.

  FIG. 8 is a flowchart showing an erasing operation when the rewriting and unauthorized use of the image of the electronic paper 1 of the first embodiment are detected.

  The electronic paper 1 is electrically connected to a rewriting device to perform a rewriting process, and in a state where the electronic paper 1 is disconnected from the rewriting device, an unauthorized use detection operation and an image erasing according to the detection result can be performed.

  The operation starts when there is a rewrite request.

  In step 101, the sensor circuit 33 is turned off.

  In step 102, a flag C indicating display rewriting is set to an initial value 0.

  In step 103, the confidentiality level (whether it can be disclosed or not) of the information on whether or not to display the displayed image is confirmed. At this time, the image code and the disclosure possibility information C are stored in the memory 31. The disclosure possibility information C is included as an index of image data supplied from the writing device. The same applies to the case where the memory 31 is provided and image data stored in the memory 31 is displayed. If it is a publicly available image, the process proceeds to step 120, where image data is written and displayed in the same manner as in the prior art. In this case, the sensor circuit 33 remains OFF. In this case, all the circuit portions of the electronic paper 1 can be brought into a non-operating state, and the power consumption can be made substantially zero. If the image cannot be disclosed, the process proceeds to step 104.

  In step 104, the sensor circuit 33 is turned on.

  In step 105, the flag C is set to 1.

  In step 106, an unauthorized use operation is detected by determining the output of the sensor circuit 33 as will be described later. If it is not an unauthorized use operation, the process proceeds to Step 107, and if it is an unauthorized use operation, the process proceeds to Step 111.

  In step 107, flag C is determined. If it is 1, the process proceeds to step 108, and if it is 0, the process proceeds to step 110.

  In step 108, the flag C is set to 0. In step 109, the image data is displayed, and the process returns to step 106.

  In step 110, the presence / absence of display rewriting is determined. Therefore, after displaying the image data in step 109, if unauthorized use is not detected and the display is not rewritten, steps 106, 107, and 110 are repeated. When rewriting, the operation from step 101 is performed again.

  In step 111, since an unauthorized use operation is detected, the entire image displayed on the screen is erased.

  In step 112, a display indicating that the image is “unpublishable” is performed on the screen. Note that since this display requires electric power, step 112 may not be performed.

  In step 113, the sensor circuit 33 is turned off.

  FIG. 9 is a flowchart showing an unauthorized use presence / absence determination process based on the output of the unauthorized use detection sensor 33.

  In step 201, it is determined whether or not both or one of the sensors A-1 and B-1 is OFF for a certain period of time. When it is OFF, there is no light input to the sensor, that is, a very dark state with no ambient light. Since it is considered that the holes of the optical sensor units 51 and 52 are blocked with tape or the electronic paper is put in a bag, it is determined that the operation is illegal use, and the process proceeds to step 204. When both the sensors A-1 and B-1 are ON, the process proceeds to step 202.

  In step 202, it is determined whether both or one of the sensors A-2 and B-2 is ON. If it is ON, it is considered that very strong light is input, that is, it is considered that scan light from a copying machine or a scanner has entered. When both of the sensors A-2 and B-2 are OFF, the process proceeds to the display step 203.

  In step 203, it is determined that the display of the image data may be maintained.

  In step 204, it is determined that the entire displayed image needs to be erased.

In order to reduce the frequency of post-detection, for example, the output determination of the sensors A-1 and B-1 can be determined based on the duration of their outputs. For example,
(A) When both sensors A-1 and B-1 are OFF for 1 second or longer, or (b) When one of sensors A-1 and B-1 is OFF for 10 seconds or longer It is determined that there is no ambient light.

  Although the first embodiment for determining an unauthorized use operation using an optical sensor has been described above, in the second embodiment described below, an unauthorized use operation is determined by another method.

  FIG. 10 is a diagram illustrating the configuration and operation of the electronic paper according to the second embodiment. The parts other than the unauthorized use detection sensor 33 are the same as those in the first embodiment.

  In the second embodiment, the up / down position sensor 61 is used as the unauthorized use detection sensor 33 to detect which direction it is facing. As shown in FIGS. 10A and 10B, in the electronic paper 1, the display element 10 is attached to the housing 50. A vertical position sensor 61 is provided at an appropriate location of the housing 50.

  As shown in FIG. 10B, the vertical position sensor 61 has an upper electrode 64 and a lower electrode 65 arranged at predetermined intervals via an insulator 67, and one end fixed to the upper electrode 64. A metal spring 63, a metal ball 62 attached to the other end of the metal spring 63, and terminals 66 A and 66 B connected to the upper electrode 64 and the lower electrode 65 are included. In a state where the display surface of the display element 10 as shown in FIG. 10A faces upward, as shown in FIG. 10B, the metal sphere 62 is in contact with the lower electrode 65 according to gravity. become. Therefore, the electrical path from the terminals 66A to 66B becomes conductive. On the other hand, in the state where the display surface of the display element 10 as shown in FIG. 10C is directed downward, as shown in FIG. 10D, the metal ball 62 contracts the metal spring in accordance with gravity, The state is separated from the lower electrode 65. Therefore, the electrical path from the terminals 66A to 66B is in an insulated state. Therefore, if the resistance, capacitance, etc. between the terminals 66A and 66B are detected, it can be detected whether the display surface faces upward or downward. The operation of the metal ball 62 is realized by appropriately setting the weight of the metal ball 62 and the spring constant of the metal spring 63.

  When copying the display surface of the electronic paper with a copying machine, the display surface is directed downward, so if the image displayed when the vertical position sensor 61 detects that it is facing downward, Unauthorized copying can be prevented.

  It is also possible to combine the optical sensor unit of the first embodiment and the vertical position sensor 61 of the second embodiment and determine the unauthorized use operation from the combination of the outputs.

  As described above, the first embodiment and the second embodiment have been described. When an image that can be disclosed is displayed, the image is hardly erased due to a malfunction, but an image that cannot be disclosed is illegally used. There are cases where the detection sensor 33 makes an erroneous determination and the image is erased, or the image is erased due to use by an incorrect method of the user. In such a case, it is required to display the erased image again.

  In order to display the erased image again, it is necessary to store an image code number indicating which image was the erased image. As described above, the code number of the image displayed before erasure is stored in the memory 31 and is used. However, if the disclosure permission / inhibition information C stored in the memory 31 indicates that the image displayed before erasure cannot be published, the user who has requested re-displaying the erasure / impossibility of erasure It is necessary to confirm that the person is a right holder who has the right to use the image.

  Therefore, when writing an unpublishable image, a password indicating that it is a legitimate right holder having the right to use the image is received together with the image data and stored in the memory 31. When an illegal use operation is detected and the image is erased, as shown in FIG. 11, since it is an unpublishable image, the fact that it has been erased is displayed, and in the case of re-displaying, it is confirmed that the person is the right holder. Display requesting password input.

  FIG. 12 is a flowchart showing the re-display process. (A) shows a process added when the process of displaying image data is first performed, and (B) shows a process when a re-display is requested.

  In step 301, after the image data is displayed in step 109 of FIG. 8, a password indicating that the person is a right holder attached to the image data is stored in the memory 31.

  In step 401, the stored password stored in the memory 31 is read.

  In step 402, the input password input via the input interface 34 is read.

  In step 403, it is determined whether the stored password and the input password match. If they match, the process proceeds to step 405. If they do not match, the process proceeds to step 404.

  In step 404, it is displayed that the passwords do not match, and the process returns to step 402.

  In step 405, the code number of the image stored in the memory 31 is read.

  In step 406, processing for displaying image data corresponding to the code number is performed. Here, when the image data is stored in the memory 31, it is read and displayed. When the image data is not stored in the electronic paper, the code number is transmitted to the writing device so that the corresponding image data is supplied.

  The user who requested re-display accesses the control unit of the writing device and inputs the password, the control unit of the writing device sends the password to the electronic paper control unit 32, and the electronic paper control unit 32 confirms that the password matches. It is also possible to send the code number back to the control unit of the writing device.

  Even if the control unit of the writing device recognizes that the user is a right holder, if there are many unpublishable images allowed to be presented to the user, the image displayed on the electronic paper is searched. Is complicated. On the other hand, if the code number indicating the erased image is stored in the electronic paper, it can be displayed again easily.

  Although the embodiment of the present invention has been described above, it goes without saying that various modifications are possible. In particular, electronic paper using cholesteric liquid crystal has been described as an example, but the present invention is not limited to this.

FIG. 1 is a diagram illustrating a bistable state (planar state and focal conic state) of a cholesteric liquid crystal. FIG. 2 is a diagram for explaining a change in the state of the cholesteric liquid crystal due to the pulse voltage. FIG. 3 is a diagram illustrating a stacked structure of cholesteric liquid crystal elements of the color display device according to the embodiment. FIG. 4 is a diagram showing the spectral reflection characteristics of each layer of the color cholesteric liquid crystal element. FIG. 5 is a diagram illustrating a structure of one cholesteric liquid crystal element of the color display device according to the embodiment. FIG. 6 is a diagram illustrating a schematic configuration of the color display device according to the embodiment. FIG. 7 is a diagram illustrating a configuration of the unauthorized use detection unit of the first embodiment. FIG. 8 is a flowchart showing the display rewriting process in the first embodiment. FIG. 9 is a flowchart showing unauthorized use detection processing in the first embodiment. FIG. 10 is a diagram illustrating a configuration of the unauthorized use detection unit of the second embodiment. FIG. 11 is a diagram illustrating an example of a display image after image deletion. FIG. 12 is a flowchart showing the redisplay process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electronic paper 10 Display element 11 Upper side substrate 12 Liquid crystal layer 13 Lower side substrate 14 Upper electrode layer 15 Lower side electrode layer 17 Light absorption layer 18 Control circuit 21 Power supply 22 Booster part 23 Voltage switching part 24 Voltage stabilization part 28 Control circuit 29 Common driver 30 segment driver 32 electronic paper control unit 33 unauthorized use detection sensor

Claims (5)

A display screen;
A display driver for displaying and erasing images on the display screen;
A fraud prevention unit that detects the first operation and controls the display drive unit to erase the image displayed on the display screen when the first operation is detected;
When the image displayed on the display screen is an image that cannot be disclosed, the fraud prevention unit is set in an operating state. When the image displayed on the display screen is an image that can be disclosed, the fraud prevention unit is A control unit for stopping operation;
A display device comprising:   The fraud prevention unit includes a photosensor group including a plurality of photosensors having different sensitivities for detecting light incident on the same portion of the display device, and the combination of outputs of the plurality of photosensors in the photosensor group The display device according to claim 1, wherein the first operation is detected.   The said fraud prevention part is equipped with the said optical sensor group in each of several places of the said display apparatus, The said 1st operation | movement is detected by the combination of the output of these optical sensors of the said several optical sensor group. The display device described.   2. The fraud prevention unit includes a sensor that detects whether the display screen is facing upward or downward, and determines that the first operation is performed when the display screen is facing downward. The display device described in 1. An image code storage unit for storing an identifier of an image that cannot be disclosed;
An authentication data storage unit for storing first authentication information,
After detecting the first operation and erasing the image displayed on the display screen, the control unit accepts input of second authentication information, and the second authentication information is the first authentication information. The display according to any one of claims 1 to 4, wherein when the information matches the information, an identifier of the unpublishable image stored in the image code storage unit is read and an image corresponding to the identifier is displayed on the display screen. apparatus.

Images