JP3794185B2 - Device using photoconductive switching element, device incorporating the device, recording apparatus and recording method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical switching element using an organic photoconductor, a device, an apparatus, a recording apparatus, and a recording method using the same.
[0002]
[Prior art]
In recent years, a light writing type spatial modulation device combining a photoconductive switching element and a functional element such as a display element has been developed and put into practical use as a light valve in a projector, etc. In addition, "Liquid Crystal Spatial Modulator and Information Processing" As described in Vol.2, No.1, '98, pp3-18, possibilities are also being investigated in the field of optical information processing.
The optical writing type spatial modulation device drives the display element by controlling the voltage applied to the display element by changing the impedance of the photoconductive switching element according to the amount of received light while applying a predetermined voltage to the element. Then, an image is displayed.
[0003]
Examples of these elements that can control the voltage or current depending on the amount of received light include, for example, a-Si used in a photodiode used in a CCD and a contact image sensor, and organic light used in a photosensitive material for electrophotography. Conductors are being researched and developed. In particular, organic photoconductors (OPCs) have been put to practical use in electrophotographic photosensitive materials and solar cells because of their low dark current, high material costs due to low cost of materials, and ease of manufacture. Based on the same reason, it is expected that the organic photoconductor is applied to the photoconductive switching element.
[0004]
Conventionally, an OPC that has been proposed and put to practical use as an electrophotographic photosensitive material generally has a structure as shown in FIG. That is, OPC is formed on the surface of the conductive substrate 50 with a two-layer structure of a charge generation layer 51 (CGL) and a charge transport layer 52 (CTL), and ions are charged on the surface. It becomes a switching element, the ion charge is extinguished in the portion irradiated with light, and the charge remains in the portion not irradiated with light. The mechanism by which the ion charge in the portion irradiated with light is extinguished is as follows. That is, when the charge generation layer 51 receives light, carriers and electrons are generated in the layer according to the wavelength and light amount, thereby generating charges. The generated electrons or carriers move to the surface through the charge transporting layer 52 and cancel out the charges due to the ions on the surface. As a result, the charge is lost in the portion irradiated with light, and the charge remains in the portion not irradiated with light. Thereafter, the charged toner is attached to the portion where the charge remains, and then the toner is transferred and fixed on paper to obtain a printed image. The reason why the charge transport layer is necessary is that the charge generation layer has a low breakdown voltage. In order to increase the breakdown voltage of OPC as an optical switch, it is necessary to provide a charge transport layer.
As shown in FIG. 28, for example, the structure applied to the solar cell is a translucent conductive film 61 such as Al on a transparent substrate 60, for example, an n-type inorganic photoconductive layer 62 such as SiO 2 or ZnO, and an X-type. A p-type organic photoconductive layer 63 such as metal-free phthalocyanine and an electrode 64 are sequentially stacked. This utilizes the fact that a potential difference is generated at the interface between the n-type layer and the p-type layer when photons are incident thereon. In this case, a high breakdown voltage is not required, and therefore a charge transport layer is not necessary.
[0005]
However, the organic photoconductor switching element has the following problems. That is, it has a rectifying action. Usually, transport by the charge transport layer is either electrons or carriers. This is because the charge transport layer material is an electron withdrawing or electron donating material. Of course, some materials such as polyvinyl carbazole can be bipolarly transported, but there is a problem in sensitivity, and they are hardly put into practical use.
For this reason, the organic photoconductor cannot be applied to, for example, an image display device combined with a liquid crystal element or an optical writing type spatial modulation element as described in “Optical Information Processing” pp171 edited by the Japan Society of Applied Physics. This is because, as described below, the applied voltage becomes higher and image burn-in occurs accordingly. That is, when a voltage is applied to an OPC having a rectifying action, it is difficult to apply a voltage with both positive and negative polarities, so the time during which an electric field is effectively applied to the liquid crystal is reduced. Therefore, in order to control the alignment of the liquid crystal, it is necessary to apply a higher voltage or to apply a voltage for a longer time.
[0006]
In addition, because it is difficult to apply an electric field of one polarity due to the rectifying action, it is equivalent to effectively applying a DC bias to the liquid crystal, so that the ions in the liquid crystal move to the vicinity of the electrode due to the bias, Switching is difficult due to the electric field generated by the ions, and image burn-in occurs. Therefore, a positive / negative AC electric field is usually applied to prevent image burn-in due to movement of ions in the liquid crystal.
It is difficult to use an OPC having a conventional structure for switching not only a liquid crystal but also an element to which a DC bias component should not be applied effectively.
For this reason, for example, in an optical switching type image display device using liquid crystal, H. Yoshida, T. Takizawa et al. “Reflective Display with Photoconductive Layer and a Bistable, Reflective Cholesteric Mixture” SID'96 APPLICATIONS DIGEST pp59 A-Si is used as a conductive switching element. Although a-Si can generate and transport charges at both electrodes, it requires advanced film formation means, and the manufacturing process is generally plasma CVD, but it is usually necessary to heat the substrate to 200 ° C or higher. Therefore, it is difficult to apply to plastic substrates, the production cost is high, and the process control is strict. Photosensitive materials such as Se and CdS can also be considered instead of a-Si, but these are materials that are extremely harmful to the environment and the human body.
[0007]
[Problems to be solved by the invention]
  The present invention has been made to solve the above-described problems, and its purpose is a functional element driven by an alternating electric field or alternating current.WhenHighly functional and inexpensive photoconductive switching elementsElectrically connected devicesIn addition, a device in which a functional element such as a photoconductive switching element and a liquid crystal display element is integrated, an apparatus incorporating the device, a recording apparatus, and a recording method are also provided.
[0008]
[Means for Solving the Problems]
  The above object can be solved by providing the following photoconductive switching elements, devices, apparatuses, recording apparatuses, and recording methods.
(1) Functional element driven by AC electric field or AC currentAnd a photoconductive switching element for switching the functional element that is electrically connected to the functional element, and an alternating electric field or an alternating current that drives the functional element is light applied to the photoconductive switching element. Device applied to the functional element under irradiationBecause
  The photoconductive switching element isAt least on a light transmissive substrate,The AC electric field or AC current is appliedA light transmissive electrode layer,Composed of organic charge generation materialCharge generation layer,Consists of organic charge transport materialsA charge transport layer, andComposed of organic charge generation materialConstructed by laminating charge generation layers sequentiallyA device characterized by that. (Hereinafter, the charge generation layer and the charge transport layer are simply referred to as “charge generation layer” and “charge transport layer”.)
  The present inventionUsed forSince the photoconductive switching element has two charge generation layers sandwiching the charge transport layer, the symmetry about 0 V is extremely excellent when an AC electric field is applied.
  In addition, a photoconductive switching element in which a charge generation material and a charge transport material are mixed at the boundary between the charge generation layer and the charge transport layer and the mixing ratio continuously changes in the stacking direction of each layer is advantageously cited. Can do. It is more advantageous to use a plastic substrate as the substrate. Moreover, an organic material can be advantageously used as a material constituting the charge generation layer and the charge transport layer.
[0009]
(2) A device in which the photoconductive switching element according to the above (1) and a functional element are integrated.
When the functional element is a functional element having a memory property, a display element, a display element having a memory property, a liquid crystal display element, a liquid crystal display element having a memory property, or a cholesteric liquid crystal display element, the device of the present invention effectively Demonstrate the function.
  By integrating the photoconductive switching element and the functional element, the connection between the photoconductive switching element and the functional element can be stabilized. In particular, a device in which a functional element having a memory property and a photoconductive switching element are integrated can be separated from a main body that drives the device, and the separated device can be distributed.
(Three) A device in which the photoconductive switching element according to (1), the functional film for removing a direct current component, and a functional element such as a display element are sequentially stacked and integrated.
  By providing the functional film for removing the direct current component in the device of the present invention, the symmetry about 0V is further improved.
  Since the functional film for removing a direct current component has a larger capacitance component than the display element portion, the performance is more effectively exhibited.
  Further, the material constituting the functional film for DC component removal is an organic material selected from the group consisting of polyvinyl alcohol (PVA), polyvinyl carbazole, polyvinyl acetate, polyethylene oxide, polybutyl alcohol, or Si-O, By using an inorganic material selected from the group consisting of Ti-O, Al-O, Si-N, PZT, Ta-O, and Al-N as a main component, the performance is more efficiently exhibited.
[0010]
(Four)the above (1)A device in which the photoconductive switching element described in 1 and a functional element having a memory property, a display element, a display element having a memory property, a liquid crystal display element, a liquid crystal display element having a memory property or a cholesteric liquid crystal display element are integrated, and the device An apparatus having a drive mechanism that is electrically connected to drive a device, the drive mechanism being separable from the device.
  The device is driven by applying an AC electric field or an AC current to a functional element or each display element integrated with the photoconductive switching element under light irradiation to the photoconductive switching element.
  This apparatus has a device in which the photoconductive switching element and the functional element as described above are integrated, and a drive mechanism that can be separated from the device, so that the device and the body that drives the device can be separated. , You can distribute the separated devices.
(Five) the above(ThreeAnd a drive mechanism that is electrically connected to the device and drives the device, wherein the drive mechanism is separable from the device.
[0011]
(6) A device in which the photoconductive switching element and the display element described in (1) above are integrated, optical writing means for making light incident on the photoconductive switching element, and a positive pulse as a drive pulse for driving the device And a pulse input means for inputting a negative pulse to the device.
  The device is adapted to irradiate the display element with light on a photoconductive switching element.Positive electrodeA negative pulse and a negative pulse are applied.
  Since this recording apparatus uses the photoconductive switching element of (1), a high reflectance can be obtained when AC electric field driving is performed.
[0012]
(7) As the pulse input means of the recording apparatus, a negative pulse is input as a final pulse, a positive pulse is input as a first pulse, or a positive pulse is input as a first pulse and a negative pulse as a final pulse. A pulse input means for inputting a pulse is preferable. Here, the negative pulse means a pulse applied so that the electrode on the display element side has a higher potential than the electrode on the photoconductive switching element side of the device. The positive pulse means a pulse applied so that the electrode on the photoconductive switching element side of the device has a higher potential than the electrode on the display element side. In this recording apparatus, it is preferable that the device further includes a functional film for removing a direct current component. Further, in this recording apparatus, a cholesteric liquid crystal display element is used as a display element, and a pulse input means for inputting a negative pulse as a final pulse (regardless of the polarity of the first pulse) is used as a pulse applying means. A recording device is preferred.
(8) the above(7), And a positive pulse and a negative pulse are input to the device as drive pulses to drive the device, and light is incident on the photoconductive switching element. Write optically and input a negative pulse as the final pulse, input a positive pulse as the first pulse, or input a positive pulse as the first pulse and a negative pulse as the final pulse. A characteristic recording method.
the above(7) and(8), A negative pulse is input as the final pulse (regardless of the polarity of the first pulse), so that a steep voltage drop occurs when the voltage is turned off, as in a cholesteric liquid crystal display element. When using the required display element, the display element can be effectively turned on.
  The above (7) and(8As in the recording apparatus and recording method in (2), by inputting a positive pulse as the first pulse, the effect of the time constant of the photoconductive switching element and the display element is eliminated, and a modulation effect can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
  Of the present inventionUse for devicesA photoconductive switching element is basically composed of a light transmissive substrate, a light transmissive electrode layer, a lower charge generation layer, a charge transport layer and an upper charge generation layer, with the charge transport layer sandwiched therebetween. It has two charge generation layers. (Hereinafter, the property of “light transmission” may be expressed as “transparent”.)
  The photoconductive switching element of the present invention will be described with reference to FIG. FIG. 1 shows the structure of a photoconductive switching element (organic photoconductive switching element having a dual CGL structure) according to the present invention, and carriers and electrons generated when the photoconductive switching element is irradiated with light. In the figure, 10 is an upper charge generation layer (top CGL), 12 is a charge transport layer, 14 is a lower charge generation layer (tail CGL), 18 is a light transmissive electrode layer, and 19 is a light transmissive substrate. As shown, the photoconductive switching element of the present invention basically comprises these elements. Reference numeral 16 denotes an electrode layer formed on the upper charge generation layer of the photoconductive switching element of the present invention.
  When light is irradiated, carriers and free electrons are generated in the upper charge generation layer 10 and the lower charge generation layer 14, and an electric field is applied so that the electrode layer 16 is a positive electrode and the electrode layer 18 is a negative electrode. Carriers generated in the upper charge generation layer 10 are injected into the charge transport layer 12 and simultaneously free electrons enter the electrode 18. The transported carriers are combined with electrons generated in the lower charge generation layer 14 and the carriers generated in the lower charge generation layer are injected into the electrode 16. As a result, current flows. When the electric field is reversed, it flows in the opposite direction. Therefore, the photoconductive switching element having this structure can be driven by an alternating electric field or alternating current.
[0014]
In the photoconductive switching element of the present invention, the charge generation material and the charge transport material are mixed at the boundary between the charge generation layer and the charge transport layer, and the mixing ratio continuously changes in the stacking direction of each layer. In the photoconductive switching element, the adhesion between the charge generation layer and the charge transport layer is increased, and a highly reliable photoconductive switching element is obtained. For example, when the composition ratio of the upper and lower charge generation layers is M and the composition of the charge transport layer is M ′, the layer structure of the photoconductive switching element is as follows. Means that.
Lower charge generation layer M / lower boundary layer x M- (1-x) M '/ charge transport layer M' / upper boundary layer (1-y) M '+ yM / upper charge generation layer M
However, 1> x> 0, 1> y> 0, and in the lower boundary layer, x changes from 1 to 0 toward the charge transport layer from the lower charge generation layer, and in the upper boundary layer, the charge transport layer Y changes from 0 to 1 toward the upper charge generation layer.
Thus, since the composition of the charge generation material and the charge transport material changes continuously, the adhesion between the charge generation layer and the charge transport layer increases.
[0015]
Below, the structure of each layer of the photoconductive switching element of this invention is demonstrated sequentially.
First, as a light-transmitting substrate used for the photoconductive switching element of the present invention, a substrate such as glass, PET (polyethylene terephthalate), PC (polycarbonate), polyethylene, polystyrene, polyimide, PES (polyethersulfone), or the like is used. Used. It is advantageous to use a light-transmitting plastic substrate from the viewpoint of obtaining a flexible substrate, being easily molded, and cost. In addition, as the light transmissive electrode layer in the present invention, an ITO film, Au, SnO₂Al, Cu, etc. are used.
[0016]
Next, materials used for the upper charge generation layer and the lower charge generation layer of the photoconductive switching element of the present invention will be described. As the material constituting the charge generation layer, organic materials that generate charges when irradiated with light, such as perylene, phthalocyanine, bisazo, dithiopytoceropyrrole, squarylium, azurenium, thiapyrylium / polycarbonate, are advantageously used. Can do.
Since the upper charge generation layer (10) and the lower charge generation layer (14) are required to generate the same amount of carriers and free electrons, the same sensitivity to wavelength, light amount, and voltage is required. Although it is desirable that both be the same material, there is no problem even if the materials are different as long as they have the same sensitivity. When the photoconductive switching element is configured using materials having the same sensitivity of the upper and lower charge generation materials, when an alternating electric field is applied under light irradiation, the asymmetry of the extracted voltage waveform with respect to 0 V, which will be described in detail later, will be described. The sex becomes extremely large.
As a method for forming the charge generation layer, a dry film forming method such as a vacuum deposition method or a sputtering method, a spin coating method using a solution or a dispersion, a dip method, or the like can be applied. Neither method requires substrate heating or strict process control as in a-Si or photodiode fabrication.
The film thickness of the upper and lower charge generation layers is 10 nm to 1 μm, preferably 20 nm to 500 nm. If the thickness is less than 10 nm, the photosensitivity is insufficient and it is difficult to produce a uniform film. If the thickness is greater than 1 μm, the photosensitivity is saturated and peeling is likely to occur due to in-film stress.
[0017]
As the charge transport material constituting the charge transport layer, trinitrofluorene, polyvinylcarbazole, oxadiazole, pyrarizone, hydrazone, stilbene, triphenylamine, triphenylmethane, diamine, etc. are applicable Is possible. LiClO_FourIt is also possible to apply ion conductive materials such as polyvinyl alcohol and polyethylene oxide to which is added. Of these, diamines are preferably used from the viewpoints of sensitivity and carrier transport capability.
As a method for forming the charge transport layer, a dry film forming method such as a vacuum deposition method or a sputtering method, a spin coating method using a solution or a dispersion, a dip method, or the like can be applied.
The film thickness of the charge transport layer is 0.1 μm to 100 μm, preferably 1 μm to 10 μm. If the thickness is less than 0.1 μm, the withstand voltage is low and it is difficult to ensure reliability. If the thickness is more than 100 μm, impedance matching with a functional element becomes difficult and design becomes difficult.
[0018]
Although described in detail in Examples, the fact that the photoconductive switching element of the present invention is excellent in voltage symmetry will be described with reference to the drawings. FIG. 2 shows a photoconductive switching element of the present invention in which a transparent electrode layer is provided on a transparent substrate, and a lower charge generation layer, a charge transport layer, and an upper charge generation layer are sequentially provided thereon. When two electrodes are connected via a resistor and an AC sine wave is applied under light irradiation, the voltage appearing at both ends of the resistor is observed. On the other hand, FIG. 3 shows the change in voltage similarly using the photoconductive switching element having the structure in which the upper charge generation layer is removed from the photoconductive switching element of FIG. As is clear from FIGS. 2 and 3, it can be seen that the symmetry of the voltage centered on 0 V is extremely superior to the conventional photoconductive switching element of the photoconductive switching element of the present invention.
[0019]
When a photoconductive switching element that is inferior in voltage symmetry is used, for example, as a switching element that drives a display element, even if a sufficient voltage is applied in one polarity to the display element during light irradiation, A sufficient voltage application cannot be obtained, and as a result, a desired display image cannot be obtained.
For example, in order to obtain a high reflectance, when a voltage higher than a threshold voltage is applied to a liquid crystal element as a display element, a sufficient voltage is applied with one polarity, and a sufficient voltage is obtained after polarity reversal even if the reflectance is increased. In other words, the liquid crystal has a low reflectance, and a predetermined high reflectance cannot be obtained. In addition, the threshold characteristics, that is, the steepness of the reflectance change with respect to the applied voltage may be deteriorated. In this case, for example, a blur or the like occurs at the edge of the image during writing, thereby degrading the resolution. Further, this is equivalent to a state in which a DC bias is effectively applied. For example, in a liquid crystal, ions are attracted to one polarity, resulting in “image burn-in” that is difficult to rewrite.
In order to avoid this problem, for example, it is conceivable to apply a higher voltage to the display element so that the voltage application to the display element is sufficient for both polarities. In this case, an even higher voltage is applied, and the reliability of the device is lowered and the power consumption is increased from the viewpoint of withstand voltage.
[0020]
As described above, the photoconductive switching element of the present invention in which two charge generation layers are provided as compared with the conventional photoconductive switching element has an excellent voltage symmetry, but the upper charge generation layer and the lower charge generation layer. Even if the same material is used, when an alternating electric field is applied under light irradiation, the extracted voltage is not necessarily symmetrical. That is, even if the same charge generation material is used for the upper and lower charge generation layers, the same photoconductive characteristics are not obtained. FIG. 4 shows a change in the voltage taken out when an AC electric field is applied under the condition where no light is irradiated. In this case, asymmetry does not occur. On the other hand, FIG. 6 shows that when an AC electric field is applied under light irradiation, the extracted voltage (for example, the voltage applied to the display element) becomes asymmetric with respect to positive and negative polarities in the positive polarity and the negative polarity. .
[0021]
The reason why voltage asymmetry occurs in the photoconductive switching element having the dual CGL structure as described above is presumed as follows. That is, for example, in the case of a dual CGL structure in which charge generation layers are formed above and below the charge transport layer, the charge generation layer on the opposite side has a lower light absorption amount than the charge generation layer prepared on the light incident side, that is, the substrate side. It can be mentioned. After the light is incident, the reduced light absorbed by the charge generation layer on the substrate side reaches the charge generation layer on the opposite side. Therefore, the light absorption amount of the charge generation layer on the opposite side to the light absorption amount of the charge generation layer on the substrate side. It is considered that the amount of light absorption differs and asymmetry occurs. In addition to this, a charge generation layer formed on a transparent electrode on a normal light incident substrate, or a charge generation layer formed on a transparent electrode via an adhesive layer as a functional film, is provided on the charge transport layer. The formed charge generation layer is considered to have a reduced photosensitivity.
Therefore, as will be described later, when a device is configured by laminating a functional element such as a display element on the photoconductive switching element of the present invention, for the reason described above, charges easily flow from the light incident side to the functional element side, and function reversely. It is difficult to flow from the element side to the substrate side. That is, when the electrode on the light incident side changes to a higher potential than the electrode on the functional element side, the current is more likely to flow from the light incident side to the functional element side, and the resistance of photoconductive switching is further reduced. Conversely, even when the functional element side electrode changes to a higher potential than the light incident side electrode, current does not easily flow from the functional element side to the light incident side, and the resistance of the photoconductive switching element increases.
[0022]
The present invention provides a functional film having a capacitive component capable of removing a direct current component, that is, a function for removing a direct current component when the photoconductive characteristics of the charge generation layers formed above and below the charge transport layer of the photoconductive switching element are not the same. It has been found that providing a film on the photoconductive switching element is effective in removing an effective DC bias and improves the voltage symmetry. The functional film for removing a direct current component will be described in detail below.
The following evaluation experiment was conducted for the purpose of observing the effect of applying a capacitive AC voltage, which is a characteristic of the functional film for removing DC components.
Since it is practically difficult to measure the waveform of each functional member in a device having a liquid crystal display, an experimental cell was fabricated as follows.
First, benzimidazole perylene (BZP) is prepared as a lower charge generation layer by vapor deposition on a glass substrate (Dow Corning: 7059) on which an ITO film is formed, and then a biphenyl-diamine material as a charge transport layer. (3,3′-Dimethyl-N, N′-bis (4-ethylphenyl) -N, N′-bis (4-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine) A solution comprising 7.2% by weight, polycarbonate-Z (bisphenol (Z) polycarbonate) 10.8% by weight, and monochlorobenzene 82% by weight was further diluted 2-fold with monochlorobenzene and applied by spin coating. A film having a thickness of 3 μm after drying was produced. Further, a BZP layer having a thickness of 0.08 μm was formed as the upper charge generation layer in the same manner as described above. An Au electrode is formed on the surface of the upper charge generation layer, and this Au electrode is replaced with a functional film for removing a direct current component at 5 nF / cm.²The capacitor was connected to make an experimental cell. Cell area is 1cm²It was. The capacitance component of the liquid crystal was 2 nF as measured with an impedance analyzer (MAP-1260 manufactured by solartron).
In order to observe the waveform, a 1 MΩ resistor was connected in series to the fabricated experimental cell, an AC sine wave of 25 Hz 140 Vpp was applied to this under irradiation of 130 mW of halogen light, and the voltage appearing across the resistor was observed. The results are shown in FIG.
[0023]
In addition, as a model in which no functional film was formed, an experimental cell was fabricated in the same manner except that a 5 nF capacitor was not provided. This was directly connected to a 1 MΩ resistor, and its waveform was examined by the same method as described above. The waveform and frequency were the same, but the applied voltage was 100 Vpp. This result is shown in FIG. 6 described above.
By comparing FIG. 5 and FIG. 6, it is clear that the symmetry with 0V as the center is remarkably superior in the former where the capacitor is connected, and the characteristic of the functional film for removing DC components of the present invention is important. The sex could be confirmed.
In the present invention, a functional film for removing a direct current component can be formed on the upper charge generation layer of the photoconductive switching element, and this can be used as another mode of the photoconductive switching element.
[0024]
Examples of the material for the functional film for removing a direct current component having such a capacitive component include, for example, polyvinyl alcohol (PVA), polyvinyl carbazole, polyvinyl acetate, polyethylene oxide, and polybutyl alcohol as organic materials. Since it is easy to manufacture, it is particularly suitable for the present invention. However, any other highly insulating material is applicable. For example, polyolefin, polystyrene, polyacetylene, polyvinyl ester, polyvinyl ether, polyether, polyester, polyacetal, polycarbonate, polyamine, polyamide, polypeptide, polyurethane, polyurea, polyimide, polyimidazole, polyoxazole, polypyrrole, polyaniline, polysulfide, polysulfide Examples include sulfone, polysiloxane, polysilane, polyphosphoric acid, polyphosphine, polyphosphine oxide, polyphosphinate, polyphosphonate, polyphosphate, polyphosphazene, phenol resin, urea resin, melamine resin, epoxy resin, alkyd resin, etc. It is done. It is effective to apply a known method such as a spin coat method or a roll coater method as a method for producing the functional film.
As the inorganic material, Si-O, Ti-O, Al-O, Si-N, PZT, Ta-O, Al-N, etc. are particularly suitable for the present invention because the functional film can be easily produced. However, other inorganic materials can be used as long as they are dielectric materials such as oxides, nitrides, carbides, etc. having high insulating properties. For example, Bi-O, Ca-O, Fe-O, Zn-S, WO, Ta-O, Mg-O, YO, Hf-O, Zr-O, Li-Ti-O, La-Ti-O, Ca-VO, Sr-Cr-O, Sr-Ti-O and the like can be mentioned.
As a method for producing the functional film made of these materials, vapor deposition, sputtering, CVD, or the like can be applied. As the insulating property, when the thin film is produced, the insulating property of the thin film is 1 MΩ / cm.²The above is desirable.
Moreover, the said functional film can be formed by using the said organic material and an inorganic material together, ie, mixing both, or laminating | stacking.
[0025]
The characteristics required for the functional film for removing a direct-current component of the present invention are high insulation and capacitance. The reason for this is that partial voltage is generated with respect to the functional film at the time of voltage application, so that the smaller the capacitance component, the higher the impedance, making it difficult to apply a sufficient voltage to the display element portion. On the other hand, when the capacity component of the functional film exceeds a certain capacity, a good liquid crystal image can be formed without increasing the applied voltage. Although it can be applied as the functional film as long as it has these characteristics, it preferably has a larger capacitance component than the display element. Needless to say, when a sufficient voltage can be applied, a functional film for removing a direct current component whose capacitance component is smaller than that of the display element can be used sufficiently. In general, 0.1 to 10 nF / cm²It is possible to use a functional film for removing a direct current component having a capacitance component of
The value of the capacitance component of the functional film can be obtained by adjusting the film thickness, for example. In general, in the case of a functional film made of an inorganic material, the thickness is generally about 0.1 μm to 1 μm, and in the case of an organic material, it is about 1 to 10 μm. It is appropriately determined depending on conditions such as the impedance of the photoconductive switching element, the impedance of the photoconductive switching element, and the writing frequency.
[0026]
In the photoconductive switching element of the present invention, a functional layer as described below can be formed. For example, a layer that prevents entry of carriers can be formed between the electrode and the charge generation layer. Further, it is possible to form a reflective film or a light shielding film, or a functional layer having a plurality of these functions may be used. Such a functional layer can be applied as long as it does not significantly impede the flow of current.
The structure of the organic optical switching element of the present invention is such that a charge generation layer is produced between charge transport layers, and the structure is such as charge generation layer / charge transport layer / charge generation layer / charge transport layer / charge generation layer, etc. It is also possible.
Thus, the photoconductive switching element of the present invention is characterized in that at least a charge generation layer, a charge transport layer, and a charge generation layer are laminated in this order on a substrate, and the material constituting each layer is a particularly expensive material. There is no necessity, and since a normal organic photoconductor (OPC) can be used, it can be mass-produced at low cost. Moreover, when an AC electric field is applied to this photoconductive switching element, its voltage symmetry is excellent, so it is particularly suitable for driving (switching) AC drive functional elements that dislike DC components such as liquid crystal display devices. Yes.
[0027]
This organic photoconductive switching element can be used by being electrically connected to a functional element as described below. The photoconductive switching element and the functional element may be connected in series, connected in parallel, or a combination thereof. Furthermore, it may be connected to other elements.
Examples of the functional element include a liquid crystal display element for image display, a display element such as an electrochromic element, an electrophoretic element, and an electric field rotation element, a spatial modulation element other than image display, an optical arithmetic element, a memory element used for a storage device, and a thermal element. Examples thereof include an image recording element for a head.
The photoconductive switching element of the present invention is effective for switching an image display element, particularly a liquid crystal display element. When a liquid crystal display element is used, it can be used as an optical writing type liquid crystal spatial modulation element. In particular, the liquid crystal display device is basically driven by alternating current and dislikes the direct current component as described above. Therefore, the application of the photoconductive switching element of the present invention is effective. The liquid crystal that can be used is nematic, smectic, discotic, cholesteric, and the like.
[0028]
In addition, examples of the functional element of the present invention include a functional element having a memory property. Examples of the functional element having a memory property include a liquid crystal display device having a memory property among the liquid crystal display elements. A liquid crystal having a memory property is a liquid crystal having a characteristic that the orientation of the liquid crystal is maintained for a certain period of time after the orientation of the liquid crystal is controlled by voltage application and then the voltage application is released. For example, a polymer-dispersed liquid crystal (PDLC), a ferroelectric liquid crystal such as a chiral smectic C phase, or a cholesteric liquid crystal. The liquid crystal having a memory property does not require power for holding an image display due to the memory property, and an integrated device described later can be manufactured and used separately from the main body. In addition, the device can be manufactured at low cost.
Further, examples of the display element having a memory property include an electrochromic element, an electrophoretic element, and an electric field rotating element in addition to the liquid crystal display element.
[0029]
In addition to this, examples of the functional element having a memory property include a memory element for a storage device using a phase change material such as a GeSbTe material or a phase separation material such as an SbOx material. These elements can be controlled, for example, by controlling an applied current, that is, Joule heat, and detection for control can be performed by detecting resistances of these elements.
[0030]
In the present invention, when the photoconductive switching element and the functional element as described above are connected, it is preferable to integrate them into a device. By integrating, the connection between the photoconductive switching element and the functional element can be stabilized.
In particular, it is effective to integrate a functional element having a memory property and a photoconductive switching element. The device in which these are integrated can be separated from the main body that drives the device. Therefore, for example, a device separated from the main body can be distributed. Further, the user can browse in a free posture at a free place.
Of course, the present invention can also be applied to separating only the image display of the liquid crystal unit. However, since it may be difficult to ensure reliability when the functional element and the organic photoconductive switching element are connected again, it is more effective to integrate the functional element and the organic photoconductive switching.
A device (image display medium) in which a liquid crystal element having a memory property and photoconductive switching are integrated as a functional element having the above memory property is particularly effective as the device of the present invention.
Further, among liquid crystal elements having a memory property, cholesteric liquid crystal has high reflectivity and excellent display performance. Therefore, a device in which a cholesteric liquid crystal display element and a photoconductive switching element are integrated is particularly desirable as an image display medium. .
Furthermore, in the present invention, it is advantageous to form a device in which the photoconductive switching element, the DC component removing functional film, and the functional element are sequentially stacked and integrated.
[0031]
As an example of a device in which the photoconductive switching element and the functional element of the present invention are integrated, FIG. 7 shows a schematic diagram of a photo-writing type spatial modulation device provided with the functional film for removing the direct current component. This device has a functional film for removing a direct current component as a functional layer 20 on a photoconductive switching element composed of a transparent substrate 19, a transparent electrode 18 a, a lower charge generation layer 14, a charge transport layer 12 and an upper charge generation layer 10. A liquid crystal display element comprising a spacer 24, a liquid crystal 22, a transparent electrode 18b, and a transparent substrate 19 is integrated on this film, and an alternating electric field is applied between the transparent electrodes 18a and 18b. Optical writing is performed by light indicated by arrows.
[0032]
In the present invention, a device that exhibits various functions can be manufactured by electrically connecting a driving mechanism that drives the device to the device in which the photoconductive switching element and the functional element are integrated as described above. it can. At this time, by configuring the drive mechanism to be detachable from the device, the device can be separated from the apparatus main body and used for browsing or distributed. Examples of the functional element include a functional element having a memory property, a display element, a display element having a memory property, a liquid crystal display element, a liquid crystal display element having a memory property, or a cholesteric liquid crystal display element. For example, a liquid crystal display element having a memory property, particularly a cholesteric liquid crystal display element is preferably used.
Further, when the device of the apparatus is a device provided with the functional film for removing a direct current component, voltage symmetry when driven by an alternating electric field is further improved.
[0033]
Next, the recording apparatus of the present invention will be described. FIG. 8 shows a schematic diagram of an example of a recording apparatus. The recording apparatus shown in FIG. 8 includes a transparent electrode 18a, a lower charge generation layer (CGL) 14, a charge transport layer (CTL) 12, and an upper charge generation layer (CGL) on a light incident side substrate 28 such as glass or plastic. An organic photoconductive switching element composed of 10, a display element 26 formed thereon, a transparent electrode 18b, and a display-side substrate 30, an optical writing spatial modulation device, and upper and lower electrodes 18a and 18b of the optical writing spatial modulation device A connector 34 for connection, a voltage applying means 36 for applying a voltage to the electrode, an optical writing means 32, and a control means 38 for controlling the voltage applying means and the optical writing means are provided.
A connector 34 for connecting to the upper and lower electrodes of the optical writing spatial modulation device is a connector for connecting to the transparent electrode on the light incident substrate side and the transparent electrode on the display side substrate side, and has a contact on each side. Of course, this can be removed freely.
[0034]
The voltage application unit 36 applies a drive pulse for display in synchronization with optical writing by the optical writing unit, and includes a generation unit for generating an applied pulse and a unit for detecting a trigger input for output. For example, the pulse generation means includes a waveform storage means such as a ROM, a DA conversion means, and a control means, and a means for DA-converting the waveform read from the ROM when a voltage is applied and applying it to the spatial modulation device can be applied. In addition, a means for generating a pulse by an electric circuit method such as a pulse generation circuit instead of a ROM can be applied, but any other means for applying a drive pulse can be used without particular limitation. be able to.
The light writing means 32 includes means for generating a light pattern to be irradiated on the light incident side of the spatial modulation device, and light irradiation means for irradiating the spatial modulation device with the pattern. For the generation of the pattern, for example, a transmissive display such as a liquid crystal display using TFT or a simple matrix liquid crystal display can be applied. As the light irradiation means, any light irradiation means that can irradiate a spatial modulation device such as a fluorescent light, a halogen lamp, and an electroluminescence (EL) light is applicable. Needless to say, an EL display, a CRT, a field emission display (FED), or the like having both a pattern generation unit and a light irradiation unit is also applicable. In addition to the above, any other means may be used as long as it can control the light amount, wavelength, and irradiation pattern irradiated to the spatial modulation device.
The control means 38 is constituted by means for controlling the operation of the above means in addition to converting the received image data into display data.
Since the recording apparatus of the present invention uses a photoconductive switching element with improved voltage symmetry, a high reflectance of a display element, for example, a liquid crystal display element can be obtained when AC electric field driving is performed.
[0035]
Next, a recording apparatus and a recording method that effectively improve performance degradation based on the asymmetry of the photoconductive characteristics of the photoconductive switching element will be described. As described above, the voltage asymmetry is remarkably improved by the photoconductive switching element and device according to the present invention. However, based on the fact that light irradiation is performed from one side, the photoconductive switching element asymmetry is reduced. It cannot be lost at all. In the present invention, by providing a recording apparatus and a recording method as described below, it has become possible to effectively improve performance degradation based on the asymmetry of photoconductive characteristics in the recording apparatus and the recording method.
Hereinafter, a recording method for a recording apparatus including the spatial modulation device of the present invention will be described.
In the photoconductive switching element having asymmetry, the amount of change in the resistance component due to the photoconductive effect when receiving light irradiation is electrically different depending on the voltage application direction. FIG. 9 is a diagram showing an electrical equivalent circuit in which the photoconductive switching element and the display element are connected, and this is explained.
For this reason, in the display element and the photoconductive switching element, impedance matching cannot be obtained when a positive pulse is applied and a negative pulse is applied, and the voltage depends on the polarity of the last pulse (final pulse) applied to the device. Waveform rounding occurs when OFF. For example, FIG. 10B shows a case where the last pulse is a positive pulse, but when the last applied pulse is a positive pulse (a current flows from the light incident side to the display element side). Shows that the waveform is rounded when the applied voltage is turned off. On the other hand, FIG. 10A shows a case where the last applied pulse is a negative pulse, but in this case, the waveform is not rounded.
By the way, especially in the case of a display element that requires a steep voltage drop when the voltage is turned off, such as a cholesteric liquid crystal, when the waveform is rounded, the display is not turned on. Arise. In order to avoid this, it is necessary to irradiate a larger amount of light and make the resistance of both polarities significantly smaller than the resistance of the liquid crystal. Therefore, in the case of a display element that requires a steep voltage drop when the voltage is turned off, it is effective to set the final pulse as a negative pulse as described above.
[0036]
In addition, due to the time constants of the liquid crystal display element and the photoconductive switching element, the voltage applied to the liquid crystal is asymmetric when a drive pulse is applied. Compared to the time constant of the display element and the photoconductive switching element, the applied pulse time is the same or shorter, and the time constant of the liquid crystal element and the switching element is about 100 ms to 1 second, whereas the drive pulse width is This is because it is generally about 1 ms to 100 ms. Therefore, when the applied pulse is a positive / negative rectangular wave, the voltage obtained by the polarity applied first and the polarity when inverted is different, which causes waveform asymmetry (see FIG. 11).
In addition to this, when the above-described asymmetry due to the photoconductive action overlaps, whether the positive polarity pulse or the negative polarity pulse is applied affects the modulation. That is, when a display element and photoconductive switching are connected in series and driven, the mode obtained is determined depending on whether a positive pulse or a negative pulse is applied as the first pulse on the photoconductive switching element side. The duration changes. For example, in a display element that controls display ON / OFF by the product of voltage and time, such as nematic liquid crystal, in order to turn the display ON by applying the first pulse, a higher applied voltage or a longer pulse Application time is required. Therefore, in the case of such a type of display element, it is effective that the first pulse is a positive pulse.
[0037]
The recording apparatus and recording method for effectively improving performance degradation based on the asymmetry of the photoconductive property of the photoconductive switching element according to the present invention is characterized by controlling the direction of pulse application to the spatial modulation element device. Yes. As shown in FIG. 12, the pulses applied to the device are combined by a positive pulse and a negative pulse, and a desired number of pulses are sequentially applied to the first pulse and the second pulse. In the recording apparatus or the recording method of the present invention, the positive pulse is input at the first pulse, the negative pulse is input at the final pulse, or the positive pulse is used as the first pulse. A method of applying a negative pulse as the final pulse is adopted. By inputting a positive pulse as the first pulse, there is an effect that modulation can be obtained, and by inputting a negative polarity pulse as the final pulse, an impedance match is obtained and a steep voltage OFF characteristic is obtained. In addition, both effects can be obtained by applying a positive polarity pulse as the first pulse and a negative polarity as the final pulse.
[0038]
Therefore, the recording apparatus of the present invention includes a device in which the photoconductive switching element and the display element of the present invention are integrated, an optical writing unit that makes light incident on the photoconductive switching element, and a drive for driving the device. It has a pulse input means for inputting a positive pulse and a negative pulse as pulses into the device, and the pulse input means inputs a negative pulse as the final pulse or a positive pulse as the first pulse. Or a positive pulse as the first pulse and a negative pulse as the final pulse.
The device of the present invention described above can be used as a device used in this recording apparatus.
As the recording apparatus of the present invention, a light writing type spatial modulation device using a cholesteric liquid crystal display element is used as a device, and a negative pulse is applied as a final pulse (regardless of the polarity of the first pulse). A recording device having means is preferred.
[0039]
Further, as the optical writing type spatial modulation device used in the recording apparatus of the present invention, it is preferable to use a device provided with the DC component removing functional film. The reason is that when the photoconductive switching element having a plurality of charge generation layers is used like the photoconductive switching element having a dual CGL structure due to the presence of the functional film, the functional film is taken out from the display. This is because the asymmetry of the voltage applied to the element can be effectively prevented.
[0040]
Further, the recording method of the present invention is a recording method using the above-mentioned recording apparatus, and a positive electrode as a drive pulse is applied to the light-transmitting electrode layer of the photoconductive switching element and the light-transmitting electrode layer provided on the display element side. In addition to inputting a negative pulse and a negative pulse, optical writing is performed from the light-transmitting electrode layer side of the photoconductive switching element, and a positive pulse is input as the first pulse or a negative pulse as the final pulse. Or a positive pulse as a first pulse and a negative pulse as a final pulse.
[0041]
The applied voltage applied in the recording apparatus or the recording method of the present invention is an alternating voltage, but a sine wave, a rectangular wave, a triangular wave, or the like can be used as a waveform. Of course, a combination of these or any arbitrary waveform can be applied. Further, in order to improve display performance and the like, a sub pulse that cannot be switched by itself may be added to the drive pulse.
Depending on the display element, application of a slight bias component may be effective, but it is needless to say that it may be adopted in the device of the present invention.
[0042]
In the recording apparatus and the recording method of the present invention, a photo-writing type spatial modulation device using a structure having a plurality of charge generation layers as an organic photoconductive switching element is used, and voltage application means and method are as described above. By devising, the display performance in light irradiation is ensured, and multiple CGLs are sandwiched between the charge transport layers at high functionality and at low cost without applying high voltage, applying long-time pulses, or irradiating large amounts of light. It is possible to display on a device having an organic photoconductive switching element and a liquid crystal display element.
Of course, the recording apparatus of the present invention irradiates with a sufficient amount of light without using the voltage applying means as described above, and is approximately 30 mW / cm.²It goes without saying that recording is possible by irradiating the above light quantity.
[0043]
【Example】
  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following, “parts”, “%” and the like are based on weight.First, the organic photoconductive switching element used in the device of the present invention will be described.
referenceExample 1
  BookreferenceIn the example, after an organic photoconductive switching element was produced, an electrode was formed on the organic photoconductive switching element, and the waveform when an AC voltage was applied while irradiating the photoconductive switching element with light was evaluated.
Benzimidazole perylene (hereinafter referred to as “BZP”) as a lower charge generation layer was formed on a glass substrate (Dow Corning: 7059) on which an ITO film was formed by evaporation to a thickness of 0.08 μm. Next, 3,3′-dimethyl-N, N′-bis (4-ethylphenyl) -N, N′-bis (4-methylphenyl)-[1,1′-biphenyl] -4 as a charge transport layer , 4′-diamine (hereinafter referred to as “biphenyl-diamine-based material”) 7.2%, bisphenol (Z) polycarbonate (hereinafter referred to as “polycarbonate-Z”) 10.8%, and monochlorobenzene 82% The solution was further diluted 2-fold with monochlorobenzene and applied by spin coating to produce a 3 μm thick film. Further, BZP was formed thereon as an upper charge generation layer by vapor deposition to a thickness of 0.08 .mu.m to produce a photoconductive switching element.
  An Au electrode was formed on the upper charge generation layer of the photoconductive switching element by sputtering. (Hereinafter, a photoconductive switching element in which an Au electrode is formed may be referred to as an OPC cell.)
  In order to observe the waveform, a resistor of 1 MΩ was connected in series to the manufactured OPC cell, and under this light irradiation, an AC sine wave of 25 Hz 200 V was applied, and the voltage appearing at both ends of the resistor was observed. A halogen light source was used for light irradiation. The amount of light at the time of light is 20 mW / cm at 550 nm using an optical power meter.²It was.
[0044]
Comparative Example 1
  referenceA photoconductive switching element having a structure in which the upper charge generation layer is removed from the photoconductive switching element of Example 1 is manufactured, and an Au electrode is further formed on the charge transport layer of the photoconductive switching element by sputtering, did.
  Next, a 1M ohm resistor was connected in series to the fabricated cell.referenceThe same AC sine wave (25 Hz 200 V) was applied under light irradiation under the same conditions as in Example 1, and the voltage appearing across the resistor was measured.
[0045]
[Evaluation 1]
  In FIG.referenceThe waveform of the voltage that appears when an alternating sine wave is applied to the organic photoconductive switching element of Example 1 and to the organic photoconductive switching element of Comparative Example 1 is shown in FIG. As clearly shown in FIGS. 2 and 3, the symmetry centered at 0V (GND) is clearly the result of the organic photoconductive switching element of the present invention having the lower charge generation layer, the charge transport layer, and the upper charge generation layer. Is remarkably superior.
[0046]
referenceExample 2
  By using a dispersion liquid containing chlorogallium phthalocyanine and a binder as a material for the lower charge generation layer and the upper charge generation layer and using a spin coating method as a layer formation method, upper and lower charge generation each having a film thickness of 0.25 μm Other than making the layer,referenceIn the same manner as in Example 1, a photoconductive switching element and an OPC cell were produced.
Comparative Example 2
  A photoconductive switching element and an OPC were produced in the same manner as in Comparative Example 1 except that a charge generation layer having a film thickness of 0.25 μm was formed from a dispersion containing chlorogallium phthalocyanine and a binder by spin coating.
[Evaluation 2]
  In FIG.referenceFIG. 14 shows a waveform of a voltage that appears when an AC sine wave is applied to the organic photoconductive switching element of Example 2 and to the organic photoconductive switching element of Comparative Example 2. As shown in FIGS. 13 and 14, the symmetry centered on 0V (GND) is clearly the result of the organic photoconductive switching element of the present invention having the lower charge generation layer, the charge transport layer, and the upper charge generation layer. Is remarkably superior.
[0047]
referenceExample 3
  By using a dispersion containing an azo-based charge generation material and a binder as the material for the lower charge generation layer and the upper charge generation layer, and using a spin coating method as a layer formation method, the upper and lower layers each having a thickness of 0.73 μm Other than making the charge generation layer,referenceIn the same manner as in Example 1, a photoconductive switching element and an OPC cell were produced.
Comparative Example 3
  A photoconductive switching element and an OPC were produced in the same manner as in Comparative Example 1 except that a 0.73 μm-thick charge generation layer was formed from a dispersion containing an azo charge generation material and a binder by spin coating.
[Evaluation 3]
  In FIG.referenceFIG. 16 shows a waveform of a voltage that appears when an AC sine wave is applied to the organic photoconductive switching element of Example 3 and to the organic photoconductive switching element of Comparative Example 3. As shown in FIGS. 15 and 16, the symmetry centered on 0V (GND) clearly indicates that the organic photoconductive switching element of the present invention having a lower charge generation layer, a charge transport layer, and an upper charge generation layer is used. Is remarkably superior.
[0048]
referenceExample 4
  Other than producing titanyl phthalocyanine by a vapor deposition method to form upper and lower charge generation layers each having a thickness of 0.08 μm,referenceIn the same manner as in Example 1, a photoconductive switching element and an OPC cell were produced.
Comparative Example 4
  A photoconductive switching element and an OPC were prepared in the same manner as in Comparative Example 1 except that a charge generation layer having a thickness of 0.08 μm was formed by vapor deposition of titanyl phthalocyanine.
[Evaluation 4]
  In FIG.referenceFIG. 18 shows a waveform of a voltage that appears when an AC sine wave is applied to the organic photoconductive switching element of Example 4 and to the organic photoconductive switching element of Comparative Example 4. As clearly shown in FIGS. 17 and 18, the symmetry centered on 0V (GND) is the same as that of the organic photoconductive switching element of the present invention having the lower charge generation layer, the charge transport layer, and the upper charge generation layer. Is remarkably superior.
[0049]
referenceExample 5
  In this example, an OPC cell for evaluating photosensitivity as an organic photoconductive switching element was produced.
On a glass substrate on which an ITO film was formed (manufactured by Dow Corning: 7059), BZP was prepared as a lower charge generation layer by vapor deposition to a thickness of 0.08 μm. Next, as a charge transport layer, a solution composed of 7.2% biphenyl-diamine material, 10.8% polycarbonate-Z, and 82% monochlorobenzene was further diluted twice with monochlorobenzene and applied by spin coating. A 3 μm thick film was prepared. On top of this, 0.08 μm of BZP was formed as an upper charge generation layer in the same manner as described above to obtain a photoconductive switching element.
  An Au electrode was formed on the upper charge generation layer of the photoconductive switching element by sputtering to obtain an OPC cell. In order to observe the waveform, connect the fabricated cell to an impedance measurement device, apply an AC sine wave of 50 Hz to the impedance measurement device under light irradiation and dark conditions, and measure the contrast in light and darkness by the voltage to determine the optical switching characteristics. evaluated. A halogen light source was used for light irradiation. The amount of light at the time of light is 20 mW / cm at 550 nm using an optical power meter.²It was.
[0050]
[Evaluation 5]
FIG. 19 shows the characteristics of the photoconductive switching element of the present invention. The ratio of resistance during light irradiation and dark time was examined by changing the voltage. The voltage is 100: 1 at 10V and 1000: 1 at 40V. Even at a relatively low voltage of 10 V, the difference in resistance between light irradiation and darkness is large, indicating that the photoconductive switching element of the present invention can be sufficiently put into practical use.
[0051]
Example1
  Here, an organic photoconductive switching element was connected to an image display element (liquid crystal cell), and a device for evaluating the display characteristics was produced.
  referenceUsing the OPC cell produced in Example 1, the liquid crystal cell was voltage driven.referenceA cholesteric liquid crystal cell was connected in series to the OPC cell of Example 1, and operation during light irradiation and darkness was confirmed. For measurement, the cells of the cholesteric liquid crystal were made into a planar layer so that the entire surface was blue, and then rectangular waves of various voltages were applied as a pulse group, and the change in reflectance was examined.
  The liquid crystal cell is wet-sprayed with Haya beads L-25 (Hayakawa Rubber Co., Ltd.), a 5 μm diameter spherical spacer with adhesive, on a glass substrate with ITO (manufactured by Dow Corning: 7059). The ITO film was brought into close contact with the spacer. After performing the above process at room temperature, in order to adhere | attach a spacer and each glass substrate with ITO, it heated at 110 degreeC and hold | maintained for 30 minutes, and produced the cell. A cholesteric liquid crystal that selectively reflects blue color light was used as the liquid crystal. The liquid crystal is nematic liquid crystal with positive dielectric anisotropy ZLI4389 (Merck) 64.9%, right-handed chiral agent CB15 (Merck) 17.5% and right-handed chiral agent CE2 (Merck) 17.5% was obtained by mixing.
  This liquid crystal was injected into the cell and sealed to obtain a liquid crystal cell.
  referenceThe Au electrode of the OPC cell of Example 1 and the ITO electrode of the liquid crystal cell are connected in series, and a voltage is applied between the ITO electrode of the OPC cell and the ITO electrode of the liquid crystal cell under light irradiation to cholesteric liquid crystal. The reflectance of was examined. A halogen light source was used for light irradiation. The amount of light at the time of light is 20 mW / cm at 550 nm using an optical power meter.²It was. The voltage was changed from 0 to 300 V at 50 Hz and 4 pulses. The driving pulse was a rectangular wave, 50 Hz, the first pulse was a positive pulse, the second pulse was a negative pulse, and this was sequentially applied up to the eighth pulse, and the final eighth pulse was a negative pulse. A positive pulse was applied to the transparent electrode of the light irradiation side substrate. Similarly, the reflectance in the dark was examined. The results are shown in FIG.
[0052]
Comparative Example 5
  In this example, an OPC cell having the same structure as that prepared in Comparative Example 1 is used.1A cholesteric liquid crystal cell having the same structure as that prepared in Example 1 was connected in the same manner.1The change in reflectance was examined under the same conditions of light irradiation and voltage application.
[0053]
[Evaluation 6]
In FIG. 20, the result of the reflectance at the time of using the organic photoconductive switch element of this invention is shown. From FIG. 20, a high reflectance (10%) was obtained during exposure in the range of 150V to 200V, and a low reflectance (2%) was obtained during non-exposure. This experiment was repeated 1000 times, but could be reproduced stably. From this result, it was shown that optical switching is sufficiently possible with the photoconductive switching element of the present invention. On the other hand, in Comparative Example 5, blue and black could not be developed by the same light irradiation.
[0054]
Example2
  Other than using a glass substrate instead of polyethylene phthalate (PET), which is a flexible substrate,referenceExample 1 using the same photoconductive switching element as in Example 11The reflectance was measured by connecting to a liquid crystal cell in the same manner as described above. However, light irradiation is 10 mW / cm at 550 nm.²It was.
[Evaluation 7]
  As can be seen from FIG. 21, at a voltage of 200 to 300 V, a high reflectance (22%) was obtained during exposure and a low reflectance (2%) was obtained during non-exposure. This experiment was repeated 1000 times, but could be reproduced stably. From this result, it was shown that the photoconductive switching element using the plastic substrate as the substrate can sufficiently perform the optical switching similarly to the photoconductive switching element using the glass substrate.
[0055]
Example3
  In this example, a device in which an organic photoconductive switching element, a display element using a liquid crystal having a memory property, and a functional film for removing a direct current component were integrated was manufactured, and a change in reflectance due to application of an alternating voltage was evaluated. In addition, a device was fabricated in the same manner except that the DC component removing functional film was not provided, and the effect obtained by the DC component removing functional film was confirmed.
  On the glass substrate with ITO electrode (manufactured by Dow Corning: 7059), BZP was prepared as a lower charge generation layer by vapor deposition to a thickness of 0.08 μm. Next, a solution composed of 7.2% biphenyl-diamine based material, polycarbonate-Z 10.8%, and 82% monochlorobenzene as a charge transport layer is further diluted twice with monochlorobenzene and applied by spin coating. A 3 μm-thick film was prepared. On top of this, 0.08 μm of BZP was similarly formed as an upper charge generation layer, which was used as a photoconductive switching element.
[0056]
Furthermore, a polyvinyl alcohol aqueous solution was applied by spin coating and dried to form a functional film for removing a direct current component having a thickness of 1 μm. The capacity of this polyvinyl alcohol film cannot be measured directly, but from a separate measurement, 3 nF / cm²It has been found to be a degree.
On top of this, liquid crystal cells were connected in series. That is, Hayabies L-25 (Hayakawa Rubber Co., Ltd.), a 5μm diameter spherical spacer with adhesive, is wet-sprayed on the functional film for removing DC components, and the ITO film contacts the spacer with the glass substrate with ITO. It was made to adhere. After performing the above process at room temperature, in order to adhere | attach a spacer and each glass substrate with ITO, it heated at 110 degreeC and hold | maintained for 30 minutes, and produced the liquid crystal cell with a photoconductive switching element.
As the cholesteric liquid crystal of the display layer that selectively reflects green color light, the liquid crystal is nematic liquid crystal E186 (Merck) with a positive dielectric anisotropy 72.3%, right-handed chiral agent CB15 (Merck) 13.9 % And a dextrorotatory chiral agent CE2 (Merck) 13.9% were used.
This liquid crystal was injected and sealed in the cell to produce a desired optical writing type spatial modulation element.
[0057]
On the other hand, in order to evaluate the action of the functional film for removing the direct current component, an optical writable spatial modulator was manufactured in the same manner as the above optical writable spatial modulator except that the functional film for removing the direct current component was not provided.
[0058]
[Evaluation 8]
  Examples thus obtained3In order to input light, a monochrome liquid crystal panel was brought into close contact with the glass substrate of the photoconductive switching element of the optical writing type spatial modulation element (with or without the functional film for removing DC component). A halogen lamp light source was used as the light source. The light input to the photoconductive switching element is 130 mW / cm when the light irradiation from the liquid crystal panel is 550 nm.²I tried to become. A voltage was applied between the electrodes of the above-described optical writing type spatial modulation element, and the reflectance was measured. Voltage application is rectangular wave, 50Hz, 8 pulses as drive pulse, 1st pulse is positive pulse, 2nd pulse is negative pulse, this is applied up to 8th pulse sequentially, the last 8th pulse is negative Pulsed. A positive pulse was applied to the transparent electrode of the light irradiation side substrate. The change in reflectance with voltage application was measured with Xrite. The result is shown in FIG.
  Comparing the two graphs, even in the device in which the DC component removing functional film was not formed, the improvement of the reflectance was started at a low applied voltage, and the reflectance increased relatively rapidly as the voltage changed. . On the other hand, in a device provided with the functional film, a sharper increase in reflectance due to a voltage change can be obtained as compared with a device not provided with the functional film. This indicates that a device provided with a functional film for removing a direct current component enables better liquid crystal display. In addition, since the partial pressure to the functional film is generated by forming the functional film, there is a concern that the threshold voltage is increased, but there is no tendency to increase the voltage, and the characteristic deterioration caused by the functional film is not observed. I couldn't.
[0059]
Example4
  In this example, the example3It was confirmed that an image display was possible with a device in which the organic photoconductive switching element, the liquid crystal element having a memory property, and the functional film for removing a direct current component were integrated.
  Example3In addition, a transmissive TFT liquid crystal display was used as the optical writing means, and a halogen lamp was used as the light source. A monochrome liquid crystal panel and a halogen lamp light source were used. In this example, the liquid crystal display was used, and light was input to the photoconductive switching element like an image. The light from the LCD image is an example3As in, 130 mW / cm at 550 nm²I tried to become.
[0060]
[Evaluation 9]
  Example4A voltage was applied to the integrated device to display a monochrome color image. A rectangular wave, 50 Hz, 8 pulses, and 175 Vpp were applied as writing pulses. As the drive pulse, the first pulse was a positive pulse, the second pulse was a negative pulse, and this was sequentially applied up to the eighth pulse, and the final eighth pulse was a negative pulse. A positive pulse was applied to the transparent electrode of the light irradiation side substrate. As a result, in the dark part and the light irradiation part, a monochrome image was obtained in which the light irradiation part was green and the dark part was black. This was recorded 1000 times but was stable.
[0061]
Example5
  In this example, the effects of the recording apparatus and recording method for applying a specific voltage in the present invention were confirmed. FIG. 23 shows the configuration of the recording apparatus of this embodiment. In the figure, 28 is a transparent substrate on the light incident side, 18a is a transparent electrode, 14 is a lower charge generation layer, 12 is a charge transport layer, 10 is an upper charge generation layer, 44 is an Au electrode (hereinafter referred to as 28 to 44 above). 30 is a display-side substrate, 18c is a transparent electrode, 26 is a liquid crystal display element, 18b is a transparent electrode, 40 is a substrate, and 42 is a light-shielding film (hereinafter, composed of 30 to 42). This is referred to as a cell for enclosing liquid crystal.) 32 is an optical writing means, 34 is a connector, 36 is a voltage applying means, and 38 is a control means.
  The connectors 34 for connecting to the upper and lower electrodes of the optical writing spatial modulation device are connectors for connecting to the transparent electrode 18a adjacent to the light incident side transparent substrate and the transparent electrode 18c adjacent to the display side substrate, respectively. There is a contact on the side. Of course, this can be removed freely.
  The voltage applying means 36 has an EPROM storing a waveform and a DA conversion device as pulse generating means, and DA-converts the waveform read from the ROM when a voltage is applied and applies it to the spatial modulation device. The waveform of the driving pulse applied to the spatial modulation device was a rectangular wave combining a positive pulse and a negative pulse.
  As the optical writing means 32, a transmissive TFT liquid crystal display and a halogen lamp light source were used.
  A personal computer was used as the voltage application means 36 and the control means 38 for controlling the optical writing means 32.
[0062]
The OPC cell was produced as follows. That is, on the glass substrate (28) with ITO electrode (18a) (manufactured by Dow Corning: 7059), BZP as a lower charge generation layer (14) is formed to a thickness of 0.02 μm by vapor deposition, and then the charge transport layer (12) A solution of 7.2% biphenyl-diamine, 10.8% polycarbonate Z, and 82% monochlorobenzene was diluted twice with monochlorobenzene and applied by spin coating to produce a 3 μm thick film. did. Further, BZP was formed thereon as an upper charge generation layer (10) to a thickness of 0.15 μm, and this was used as a photoconductive switching element. An Au electrode (44) having a thickness of 50 mm was formed on the upper charge generation layer of this photoconductive switching element to form an OPC cell.
[0063]
Moreover, the cell for enclosing liquid crystal was produced as follows. That is, a light shielding layer (42) made of a black matrix resin for TFT (trade name BKR, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is formed on one side of a glass substrate (40) (manufactured by Dow Corning: 7059), and an ITO film is formed on the opposite side. A layer of the transparent electrode (18b) made of was formed to a thickness of 200 mm. On this ITO film, Haya beads L-25 (manufactured by Hayakawa Rubber Co., Ltd.), a 5 μm diameter spherical spacer with an adhesive, is wet-sprayed, and a glass substrate (30) with ITO (18c) is used as a spacer. It was made to adhere so that it may contact. After performing the above process at room temperature, in order to adhere | attach a spacer and each glass substrate with ITO, it heated at 110 degreeC and hold | maintained for 30 minutes, and produced the cell.
The liquid crystal injected into the cell is a cholesteric liquid crystal that selectively reflects green color light, nematic liquid crystal E186 with positive dielectric anisotropy (Merck) 72.3%, right-handed chiral agent CB15 (Merck) 13.9% and dextrorotatory chiral agent CE2 (Merck) 13.9% were mixed and used. This liquid crystal was injected into the cell to obtain a liquid crystal cell.
[0064]
Next, the Au electrode 44 of the OCP cell and the transparent electrode 18b of the liquid crystal cell were connected to produce a desired optical writing type spatial modulation element.
Further, as shown in FIG. 23, the transparent electrodes 18a and 18c of the optical writing type spatial modulation element are connected to the voltage applying means via the connector 34, and the control means 38 and the optical writing means 32 are also shown in FIG. The recording apparatus of the present invention was assembled by arranging and connecting the two.
In order to confirm the effect of the recording method of the present invention, the first pulse is a positive pulse and the second pulse is a negative pulse as a drive pulse, and this is applied in sequence up to the eighth pulse, and the final eighth pulse is a negative pulse. It was. Pulse width is 20 ms, 6 mW / cm at a wavelength of 550 nm²And the change in reflectance with respect to the applied voltage was evaluated. In order to evaluate the change in reflectance, the irradiation pattern was set so that all display elements were turned on.
[0065]
Comparative Example 6
  In this example, as the drive pulse, the first pulse is a negative pulse, the second pulse is a positive pulse, this is sequentially applied up to the eighth pulse, and the final eighth pulse is a positive pulse. Other examples5The reflectance was measured in the same manner as described above.
[0066]
[Evaluation 10]
  Example5The results of Comparative Example 6 are shown in FIG. The incident light is 6 mW / cm as in this example.²Even in such a small case, it was shown that when a negative pulse was applied to the light incident substrate side as the last drive pulse, the display element was turned on by applying a voltage of 220 Vpp or higher. On the other hand, in the comparative example in which a positive pulse is input as the last drive pulse, the amount of light is small, so it is difficult to turn on the display element depending on voltage application.
[0067]
Example6
  Example3The device provided with the functional film for removing the direct current component prepared in step 1 is used. The light input to the photoconductive switching element is 13 mW / cm when the light irradiation from the liquid crystal panel is 550 nm.²The first pulse is a positive pulse, 10 pulses are applied at 20 ms (final negative pulse), and then a 100 ms pause is applied, and this is repeated three times.3The reflectance was measured in the same manner as described above.
Comparative Example 7
  Example6Then, the reflectance was measured in the same manner except that 11 pulses having a positive pulse as the final pulse were applied.
[Evaluation 11]
  As shown in FIG. 25, when a voltage is applied to the device of the present invention so that the final pulse is a negative pulse, a high reflectance is obtained at a voltage of 300 V or more, and more sharp reflection due to a voltage change. An increase in rate is obtained. On the other hand, when the final pulse was a positive pulse, the reflectance was not increased even when a voltage of 350 V was applied, and optical switching could not be performed.
[0068]
Example7
  Example5The upper and lower charge generation layers of the dual CGL structure of the photoconductive switching element used in Example 1 were replaced with 0.08 μm thick titanium phthalocyanine.5An optical writing type spatial modulation device and a recording apparatus similar to the above are manufactured5The reflectance was measured by applying a pulse voltage in the same manner as described above.
[0069]
Comparative Example 8
  Example 1 except that the first pulse is applied to the transparent electrode on the display substrate side, that is, a negative pulse and the final pulse is a positive pulse7The change in reflectance was evaluated in the same manner as above.
[Evaluation 12]
  Examples thus obtained7A voltage was applied to the optical writing type spatial modulation element of Comparative Example 8 and the reflectance was measured. The pulse width was 20 ms, 6 mW of light was irradiated at a wavelength of 550 nm, and the change in reflectance with respect to the applied voltage was evaluated. In order to evaluate the change in reflectance, the irradiation pattern was set so that all display elements were turned on.
The result is shown in FIG.
  When comparing the two graphs, it was shown that when a negative pulse was applied to the light incident substrate side as the last drive pulse, the display element was turned on by applying a voltage of 320 Vpp or more. In the comparative example in which a pulse was input, it was difficult to turn on the display element by voltage application.
[0070]
【The invention's effect】
  Of the present inventionUse for devicesThe photoconductive switching element in which at least a charge generation layer, a charge transport layer, and a charge generation layer are laminated on a substrate does not require a particularly expensive material and uses a normal organic photoconductor (OPC). Therefore, it can be mass-produced at a low cost and can exhibit a high-performance optical switching function. That is, the photoconductive switching element of the present invention is substantially symmetrical on the plus side and minus side even when the polarity of the voltage waveform during light irradiation is reversed. It is suitable for driving a functional element that is normally based on AC driving, and the photoconductive switching element of the present invention has a large difference in resistance value and reflectance during light irradiation and darkness. This is excellent for optical switching of image display elements such as liquid crystal.
[0071]
In the present invention, the photoconductive switching element and the functional element can be made reliable by integrating the photoconductive switching element and the functional element into a device.
In particular, a device in which a functional element having a memory property and a photoconductive switching element are integrated can be separated from a main body that drives the device, and the device can be distributed. Further, the user can browse in a free posture at a free place.
In addition, the device provided with the functional film for removing the direct current component is further improved in voltage symmetry, and it is not necessary to apply a high voltage.
In the present invention, a device that exhibits various functions is manufactured by electrically connecting a drive mechanism for driving the device to the device in which the photoconductive switching element and the functional element are integrated as described above. be able to. In such an apparatus, a recording apparatus using a display element as a functional element can increase the reflectance of the display element, for example, a liquid crystal display element.
Furthermore, in the recording apparatus and recording method of the present invention, by performing a specific voltage application, to ensure display performance in light irradiation, without performing high voltage application or long-time pulse application and light irradiation of a large amount of light, A highly functional and inexpensive recording apparatus and recording method can be achieved. That is, in the recording apparatus and method of the present invention, a sharp voltage drop is required when the voltage is turned off to turn on the display like a cholesteric liquid crystal by setting the last pulse applied to the device to a negative pulse. Even in the display element, the display can be efficiently turned on. In addition, a modulation effect can be obtained by making the first pulse applied to the device a positive pulse.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a layer structure of a photoconductive switching element of the present invention.
[Figure 2]referenceIt is a figure which shows the response waveform at the time of light irradiation and alternating current sine wave application to the cell of the photoconductive switching element of Example 1.
3 is a diagram showing a response waveform when light is irradiated and an AC sine wave is applied to a cell of the photoconductive switching element of Comparative Example 1. FIG.
FIG. 4 is a diagram showing a response waveform when a non-light irradiation / AC sine wave is applied to a cell of the photoconductive switching element of the present invention.
FIG. 5 is a diagram showing response waveforms when a capacitor is connected to the photoconductive switching element of the present invention and light irradiation and an alternating sine wave are applied.
FIG. 6 is a diagram showing a response waveform when a light irradiation / AC sine wave is applied to the photoconductive switching element of the present invention (no DC component removal functional film is provided).
FIG. 7 is a schematic view showing an example of an optical writing modulation device including the photoconductive switching element of the present invention provided with a functional film for removing a direct current component.
FIG. 8 is a schematic diagram illustrating an example of a recording apparatus including the optical writing modulation device of the present invention.
FIG. 9 is a diagram showing an electrical equivalent circuit in which a photoconductive switching element and a display element are connected.
10 is a conceptual diagram showing voltage decay after the last pulse is turned off when a pulse voltage is applied to the photoconductive switching element. FIG. 10 (A) is a negative pulse, FIG. B) shows the case where the final pulse is a positive pulse.
FIG. 11 is a conceptual diagram showing the influence of a time constant on the applied voltage applied to the display element.
FIG. 12 is a conceptual diagram showing an example of a pattern of pulses applied to the device of the present invention.
FIG. 13reference10 is a diagram showing a response waveform of Example 2. FIG.
14 is a diagram showing a response waveform of Comparative Example 2. FIG.
FIG. 15reference10 is a diagram illustrating a response waveform of Example 3. FIG.
16 is a diagram showing a response waveform of Comparative Example 3. FIG.
FIG. 17reference10 is a diagram showing a response waveform of Example 4. FIG.
18 is a diagram showing a response waveform of Comparative Example 4. FIG.
FIG. 19referenceIt is a figure which shows the resistance which appears when an alternating current sine wave is applied to the cell of the photoconductive switching element of Example 5 at the time of light irradiation and non-irradiation.
FIG. 20 Example1It is a figure which shows the reflectance in.
FIG. 21 Example2It is a figure which shows the reflectance in.
FIG. 22 Example3It is a figure which shows the reflectance in.
FIG. 23 Example5It is the schematic which shows the recording device.
FIG. 24 Example5It is a figure which shows the reflectance in Comparative Example 6.
FIG. 25 Example6It is a figure which shows the reflectance in Comparative Example 7.
FIG. 26 Example7It is a figure which shows the reflectance in Comparative Example 8.
FIG. 27 is a diagram showing a layer structure of an electrophotographic photoreceptor using a conventional organic photoconductor.
FIG. 28 is a diagram showing a layer configuration of an optical semiconductor for a solar cell using a conventional organic photoconductor.
[Explanation of symbols]
10 Upper charge generation layer
12 Charge transport layer
14 Lower charge generation layer
18a, 18b, 18c electrode
19 Transparent substrate
20 functional layer (DC component removal functional film)
22 LCD
24 Spacer
26 Display elements
28 Light incident side substrate
30 Display side board
32 Optical writing means
34 Connector
36 Voltage application means
38 Control means

Claims (22)

An AC electric field or AC for driving the functional element , comprising: a functional element driven by an alternating electric field or alternating current; and a photoconductive switching element for switching the functional element electrically connected to the functional element. A current is a device applied to the functional element under light irradiation to the photoconductive switching element ,
The photoconductive switching element comprises at least a light transmissive electrode layer to which the alternating electric field or alternating current is applied, a charge generation layer composed of an organic charge generation material , and an organic charge transport material on a light transmissive substrate. device according to claim Rukoto configured constituted a charge transport layer, and by sequentially laminating a charge generation layer formed of an organic charge generating material. 2. The device according to claim 1, wherein the charge generation material and the charge transport material are mixed at the boundary between the charge generation layer and the charge transport layer, and the mixing ratio continuously changes in the stacking direction of each layer. . The device according to claim 1, wherein a plastic substrate is used as the substrate. The device according to claim 1, wherein the photoconductive switching element and the functional element are integrated. The device according to claim 1 , wherein the functional element is a functional element having a memory property. The device according to claim 1 , wherein the functional element is a display element. The device according to claim 6 , wherein the display element is a display element having a memory property. The device according to claim 6 , wherein the display element is a liquid crystal display element. The device according to claim 8 , wherein the liquid crystal display element is a liquid crystal display element having a memory property. The device according to claim 9 , wherein the liquid crystal display element having a memory property is a cholesteric liquid crystal display element. The device according to claim 1, wherein the photoconductive switching element according to claim 1 , the DC component removing functional film, and the functional element according to claim 1 are sequentially laminated and integrated. The device according to claim 11 , wherein the functional element is a display element. 13. The device according to claim 12 , wherein the functional film for removing a direct current component has a capacitance component larger than that of the display element. The functional film for removing a direct current component having a larger capacity component than the display element is mainly composed of an organic material selected from the group consisting of polyvinyl alcohol (PVA), polyvinyl carbazole, polyvinyl acetate, polyethylene oxide, and polybutyl alcohol. 14. The device according to claim 13 , wherein the device is made of a material. An inorganic film selected from the group consisting of Si-O, Ti-O, Al-O, Si-N, PZT, Ta-O, and Al-N, wherein the functional film for removing a DC component having a larger capacitance component than the display element The device according to claim 13 , wherein the device is made of a material mainly composed of a material. A light transmissive electrode layer to which at least an alternating electric field or alternating current is applied on a light transmissive substrate, a charge generation layer composed of an organic charge generation material, a charge transport layer composed of an organic charge transport material, and A photoconductive switching element in which charge generation layers composed of organic charge generation materials are sequentially stacked and a functional element having a memory characteristic, a display element, a display element having a memory characteristic, a liquid crystal display element, a liquid crystal display element having a memory characteristic, or a cholesteric A device having a liquid crystal display element integrated therein and a drive mechanism electrically connected to the device to drive the device , wherein the device is a functional element integrated with a photoconductive switching element or each display the element, have in the alternating electric field under light irradiation of the photoconductive switching element is a device that alternating current is applied is driven, the Kinematic mechanism unit which is a separable and the device.   14. An apparatus comprising: the device according to claim 13; and a drive mechanism electrically connected to the device to drive the device, wherein the drive mechanism is separable from the device. A light transmissive electrode layer to which at least an alternating electric field or alternating current is applied on a light transmissive substrate, a charge generation layer composed of an organic charge generation material, a charge transport layer composed of an organic charge transport material, and A device in which a photoconductive switching element and a display element in which charge generation layers composed of organic charge generation materials are sequentially stacked are integrated, an optical writing means for entering light into the photoconductive switching element, and for driving the device and a pulse input means for inputting a positive pulse and a negative pulse to the device as the driving pulse, the device to the display device, the positive electrode of the pulse and the negative polarity under light irradiation to the photoconductive switching element A recording device to which a pulse is applied . Pulse input means for inputting a negative pulse as a final pulse, a positive pulse as a first pulse, or a positive pulse as a first pulse and a negative pulse as a final pulse The recording apparatus according to claim 18 , wherein: 20. The recording apparatus according to claim 19 , wherein the display element is a cholesteric liquid crystal display element, and the pulse input means is a pulse input means for inputting a negative pulse as a final pulse. The recording apparatus according to claim 19 , wherein the device further includes a functional film for removing a direct current component. 20. A recording method using the recording apparatus according to claim 19 , wherein a positive pulse and a negative pulse are input to the device as drive pulses to drive the device, and light is incident on the photoconductive switching element. Write the light and input a negative pulse as the final pulse, input a positive pulse as the first pulse, or input a positive pulse as the first pulse and a negative pulse as the final pulse. A recording method characterized by the above.

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