JP2007279369A - Optical writing type display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical writing type display medium which uses an optical switching layer to improve driving power, display characteristics, and further stability of repetition in AC drive. <P>SOLUTION: The optical writing type display medium includes at least a display layer and the optical switching layer between a pair of electrodes, wherein the optical switching layer has a single layered bipolar photosensitive body containing a charge generation material, a hole transport material, and an electron transport material as the optical switching layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical writable display medium having an optical switching layer using an organic photoconductor (OPC).

  An optical writing display device drives a display element by applying a predetermined voltage to the element, changing the impedance of the optical switching element according to the amount of received light, and controlling the voltage or current applied to the display element. The image is displayed. In particular, an optical writable display medium in which a display element having a memory property and a photoconductive switching element are stacked, a voltage is applied to the display element, and an optical image is incident thereon to perform writing is separated from the writing device. It is attracting attention as an electronic paper medium that can be carried around.

  Examples of the display element of the optically writable display medium include a liquid crystal display element such as a nematic liquid crystal, a cholesteric liquid crystal, and a ferroelectric liquid crystal dispersed in a polymer and imparting a memory property, an electrophoretic element, an electric field rotating element, and a toner electric field movement. Mold elements, elements encapsulating these elements, and the like have been studied.

As these optical switching elements that can control the voltage or current depending on the amount of received light, for example, amorphous silicon elements used in the field of electrophotography, OPC elements having a function-separated two-layer structure using organic photoconductors, Further, an OPC element having a structure (hereinafter referred to as a dual CGL structure) in which a charge generation layer (hereinafter also referred to as “CGL”) is formed above and below a charge transport layer (hereinafter also referred to as “CTL”). (For example, refer to Patent Document 1). In particular, since the OPC element does not require high-temperature heat treatment in the manufacturing process, it can be applied to a flexible substrate such as a PET film, and has an advantage that it can be manufactured at a low cost because a vacuum process is unnecessary. .
In particular, the dual CGL structure is particularly effective because it can be driven by alternating current, and even when a liquid crystal element is used as a display element, an image burn-in phenomenon that is a problem with direct current drive is less likely to occur.

  There are two methods for producing a charge generation layer of an OPC element used for this optical switching element: a method using a vacuum process such as vapor deposition and sputtering, and a method of applying a dispersion liquid in which a charge generation material is dispersed. In the method using the process, since the device is expensive, it is difficult to manufacture a low-priced medium. On the other hand, in the coating method, mass production is possible at low cost and the cost is superior. As a method, a coating method has attracted attention.

  In order to fabricate the dual CGL structure by a coating method, an ester-based or ketone-based solvent generally used as a solvent for the charge generating material dispersion is formed in the charge transporting layer when the upper charge generating layer is formed. In order to avoid the problem of damaging, an alcohol-based solvent that does not dissolve or swell the charge transport layer has been used as a solvent for forming the upper charge generation layer (for example, patent document) 2).

  However, in general, when a charge generation layer-forming coating solution is prepared using an alcohol solvent and a binder resin restricted thereby, the dispersibility of the charge generation material is poor, and the photosensitivity of the OPC having a CGL film formed thereon is low. Defects such as a decrease, a large amount of dark charge, and a low repetition stability often occur.

In addition, in some cases, the optical switching element manufactured by this method has a problem that the symmetry of the response voltage waveform during AC driving is not sufficient. When such an optical switching element with poor symmetry of the response waveform is used as a switching element for driving a display element, for example, even if a sufficient voltage is applied in one polarity to the display element during light irradiation, In the opposite polarity, sufficient voltage application cannot be obtained, and as a result, a desired display image cannot be obtained.
Thus, when the dual CGL structure is formed by the coating method, a photo-writing display medium having satisfactory characteristics has not been obtained.
JP 2000-180888 A JP 2002-196291 A

Accordingly, an object of the present invention is to solve the conventional problems and achieve the following object.
That is, an object of the present invention is to provide an optical writable display medium using an optical switching element capable of improving display characteristics and driving capability in alternating current driving, and further repetitive stability.

  In order to solve the above problems, the present inventors have studied a photoconductor other than the dual CGL structure, specifically, a bipolar photoconductor as an optical switching layer that can handle AC driving. Further, the photoconductive characteristics necessary for driving the optically writable display medium are further clarified, and a single-layer ambipolar photoconductor capable of handling the photoconductive display medium, in particular, a combination of an electron transporting material and a hole transporting material, and further charge As a result of examination from the viewpoint of optimization with the generated material, it was found that good dispersibility and high AC drive characteristics can be obtained by using specific materials mixed together, and the present invention has been conceived. That is, the present invention

<1> An optically writable display medium including at least a display layer and an optical switching layer between a pair of electrodes,
The optical switching layer is an optically writable display medium having a single ambipolar photosensitive layer containing a charge generating material, a hole transporting material and an electron transporting material.

<2> The optically writable display medium according to <1>, wherein the electron transporting material is a low-molecular electron transporting material, and the hole transporting material is a hole transporting polymer.

<3> The optical writing according to <2>, wherein the hole transporting polymer is at least one of charge transporting polymers represented by the following general formulas (I-1) and (I-2). Type display medium.

In general formulas (I-1) and (I-2), Y and Z each independently represent an arbitrary organic group, A represents an organic group represented by the following general formula (II-1), and B and B Each independently represents —O— (Y—O) _m —H or —O— (Y—O) _m —CO—Z—CO—OR ′ (where R ′ represents a hydrogen atom, substituted or unsubstituted Represents an alkyl group, a substituted or unsubstituted aryl group, Y and Z each independently represents an arbitrary organic group.), M represents an integer of 1 to 5, and p represents an integer of 5 to 5000. .

  In general formula (II-1), Ar represents a substituted or unsubstituted aromatic group, X represents a substituted or unsubstituted aromatic group, T represents a hydrocarbon group, k and n are each independently An integer of 0 or 1 is represented.

<4> The optically writable display medium according to <3>, wherein Ar in the organic group represented by the general formula (II-1) is a substituted or unsubstituted aromatic group having 2 or more aromatic rings.

<5> X in the organic group represented by the general formula (II-1) is any one of organic groups represented by the following structural formulas (III-1), (III-2) and (III-3) <4> is the optically writable display medium.

<6> The optically writable display medium according to any one of <1> to <5>, wherein the display layer is a liquid crystal display layer having a memory property.

  ADVANTAGE OF THE INVENTION According to this invention, the optical writing type display medium using the optical switching layer which can improve the drive capability in AC drive, a display characteristic, and also repetitive stability can be provided.

Hereinafter, the present invention will be described in detail. In the description with reference to the drawings, members having substantially the same function will be described by giving the same reference numerals throughout the drawings.
The optical writing type display medium of the present invention is an optical writing type display medium including at least a display layer and an optical switching layer between a pair of electrodes, wherein the optical switching layer includes a charge generation material, a hole transport property. It has a single-layered bipolar photosensitive layer containing a material and an electron transporting material.

  As will be described later, since the optically writable display medium of the present invention uses a single-layered bipolar photoconductor as an optical switching layer, an alternating current can be obtained without forming an upper charge generation layer as in the dual CGL structure. It can be driven. For this reason, the problem of damaging the charge transport layer associated with the formation of the upper charge generation layer does not occur, and it has a single-layer structure, so that the optical switching layer can be more easily produced.

In addition, since it is not necessary to prepare a coating solution for forming a charge generation layer with an alcohol solvent, the dispersibility and dispersion stability of the charge generation material are improved, and the content of the charge generation material can be set very low. The dark resistance of the optical switching layer can be increased, and the light-to-dark ratio of the optical switching layer and the repetition stability can be improved. Therefore, even in the optical writable display medium using this, the AC drive characteristics (drive margin, etc.) And stable writing and display.
The bipolar photoconductor is a photoconductor that can transport both electrons and holes with a certain mobility or more and can operate in a positive polarity and a negative polarity under an electric field.

The bipolar photoconductor can be easily produced by using a material having an ambipolar charge transport ability as a charge transport material, but no single material having the ambipolar charge transport ability is known at present.
Therefore, the present inventors have examined in more detail an ambipolar charge transport material obtained by mixing a conventional electron transport material and a hole transport material, in particular, a specific material having a large positive and negative charge mobility or In addition, a low molecular weight electron transport material dispersed in a hole transport polymer having a specific structure has excellent mixing and dispersion characteristics of the charge generation material, and by using these, the AC drive characteristics are excellent. A new single-layer bipolar photoconductor for an optical switching layer was obtained, and it was found that an optically writable display medium capable of solving the above problems could be constructed, thereby completing the present invention.

  FIG. 1 is a conceptual diagram showing an example of the optically writable display medium of the present invention using an optical switching layer having the above-mentioned bipolar photoconductor. The optical writing type display medium 20 includes an optical switching layer 30, a display element 40, and a functional layer 50 sandwiched between the optical switching layer 30 and the display element 40. The optical switching layer 30 includes a substrate 31 and an electrode 32. The display element 40 includes a substrate 41, an electrode 42, and a display layer (liquid crystal layer or the like) 43.

In the optical writing type display medium 20, it is necessary to make the substrate and the electrode of the light incident side element light transmissive depending on whether the optical writing is performed from the optical switching layer side or the display element side. An AC electric field is applied between the electrodes 32 and 42.
The optically writable display medium of the present invention will be described below for each of the above configurations.

<Optical switching layer>
FIG. 2 shows an enlarged portion of the optical switching layer in the optical writable display medium shown in FIG. The optical switching layer in this invention is demonstrated using this.
An optical switching layer 30 (an optical switching layer having a bipolar photosensitive member) shown in FIG. 2 is a single-layer bipolar electrode as an optical switching layer (photoconductive layer) on a substrate 31 on which an electrode 32 (conductive film) is formed. The photosensitive photoconductor layer 34 is provided. In the figure, an arrow indicates a light incident direction (however, the light incident direction is not limited to this).

As the substrate 31, a substrate such as glass, PET (polyethylene terephthalate), PC (polycarbonate), PEN (polyethylene aphthalate), polyethylene, polystyrene, polyimide, PES (polyethersulfone), SUS, Ni, Al, or the like is used. In addition, when an organic material is used for the photoconductive layer (bipolar photoreceptor layer), there is no heat treatment step at a high temperature, so that a flexible substrate can be obtained, molding is easy, and light transmission is possible due to cost. It is advantageous to use a flexible plastic substrate.
The thickness of the substrate 31 is preferably in the range of 50 to 500 μm.

As the electrode 32, an ITO film, Au, SnO ₂ , Al, Cu or the like is used.
The substrate 31 and the electrode 32 do not necessarily have to be light transmissive. That is, as shown in Japanese Patent Laid-Open No. 2001-1000066, the display element of the optically writable display medium has a memory property and selectively reflects or reflects back a wavelength necessary for display. In this case, writing can be performed from the display side. In this case, at least the substrate 31 and the electrode 32 on the display element side need only be light transmissive. Therefore, when optical writing is performed from the display element side, the substrate 31 or the electrode 32 of the optical switching element 30 does not need to be light transmissive, and an opaque Al layer or the like can be used as the electrode 32.

  In addition, any functional layer can be provided in the optical switching layer. For example, it is possible to form a layer or an adhesive layer that prevents charge from entering between the electrode and the bipolar photosensitive 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 the flow of current is not significantly disturbed.

(Bipolar photoreceptor)
The bipolar photoconductor in the present invention is a single layer, and includes a charge generation material, a hole transport material, and an electron transport material.
Examples of the charge generating material contained in the bipolar photoreceptor layer 34 include metal or metal-free phthalocyanine pigments, squarium pigments, azulenium pigments, perylene pigments, indigo pigments, bisazo pigments, trisazo pigments, quinacridone pigments, pyrrolopyrrole pigments, dibromoanthanthrone. A polycyclic quinone pigment such as chlorogallium phthalocyanine, hydroxygallium phthalocyanine, or titanyl phthalocyanine, which is a phthalocyanine pigment, is preferably used as a main component.

  As hydroxygallium phthalocyanine, the black angle (2θ ± 0.2 °) of the X-ray diffraction spectrum is i) 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25 1 ° and 28.3 °, ii) 7.7 °, 16.5 °, 25.1 ° and 26.6 °, iii) 7.9 °, 16.5 °, 24.4 ° and 27. 6 °, iv) 7.0 °, 7.5 °, 10.5 °, 11.7 °, 12.7 °, 17.3 °, 18.1 °, 24.5 °, 26.2 ° and 27.1 °, v) 6.8 °, 12.8 °, 15.8 ° and 26.0 ° or vi) 7.4 °, 9.9 °, 25.0 °, 26.2 ° and 28 A crystal structure having a strong diffraction peak at .2 ° is particularly preferable because of high charge generation efficiency.

As chlorogallium phthalocyanine, in the X-ray diffraction spectrum, the Bragg angle (2θ ± 0.2 °) is at least 7.4 °, 16.6 °, 25.5 ° and 28.3 °, or 6.8 °, Strong diffraction peaks at 17.3 °, 23.6 ° and 26.9 °, or 8.7 ° to 9.2 °, 17.6 °, 24.0 °, 27.4 ° and 28.8 ° A crystal structure having a high charge generation efficiency is particularly preferable.
Further, as titanyl phthalocyanine, the black angle (2θ ± 0.2 °) of the X-ray diffraction spectrum is 9.5 °, 9.7 °, 11.7 °, 15.0 °, 23.5 °, 24 A crystal structure having diffraction peaks at 1 ° and 27.3 ° is particularly preferable because of high charge generation efficiency.

The content of the charge generating material in the bipolar photoreceptor layer is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.5 to 5% by mass.
If the content is less than 0.1% by mass, the photosensitivity is not sufficient, and good display characteristics for optical writing may not be obtained when used in an optical writing type display medium. If it exceeds 20 mass%, the dark resistance of the photosensitive layer cannot be sufficiently increased, and the drive margin during AC driving may be reduced.

  In addition, the bipolar photoreceptor layer 34 further includes at least an electron transporting material and a hole transporting material. In this case, as a combination of materials, any of three forms of low molecular charge transport materials, low molecular charge transport materials, charge transport polymers, and charge transport polymers can be used.

As the charge transporting material contained in the bipolar photosensitive layer 34, any known material can be used, but the following materials can be exemplified.
Examples of the hole transporting material include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, and the like. Pyrazoline derivatives, triphenylamine, tri (p-methyl) phenylamine, N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine, dibenzylaniline, 9,9-dimethyl-N, N-di Aromatic tertiary amino compounds such as (p-tolyl) fluoren-2-amine, N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1-biphenyl] -4, Aromatic tertiary diamino compounds such as 4′-diamine, and 1, such as 3- (p-dimethylaminophenyl) -5,6-di- (p-methoxyphenyl) -1,2,4-triazine , 4-triazine derivatives, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4-diphenylaminobenzaldehyde-1,1-diphenylhydrazone, [p- (diethylamino) phenyl] (1-naphthyl) phenylhydrazone, and other hydrazone derivatives Quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p- (2,2-diphenylvinyl) -N, An α-stilbene derivative such as N-diphenylaniline, an enamine derivative, a carbazole derivative such as N-ethylcarbazole, or a polymer having a group consisting of the above compounds in the main chain or side chain can be exemplified. .

  Examples of the electron transporting material include quinone compounds such as chloranil, bromoanil and anthraquinone, tetracyanoquinodimethane compounds, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro. Fluorenone compounds such as -9-fluorenone, 2- (4-biphenyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole and 2,5-bis (4-naphthyl) -1 , 3,4-oxadiazole, oxadiazole compounds such as 2,5-bis (4-diethylaminophenyl) -1,3,4-oxadiazole, xanthone compounds, thiophene compounds, 3,3 ′, Diphenoquinone compounds such as 5,5 ′ tetra-t-butyldiphenoquinone and 3,3′-dimethyl-5,5′-dicyclohexyldiphenoquinone , Or the like polymer having a group consisting of the compounds shown above in the main or side chain.

In particular, it is difficult to obtain an electron transporting material having high transportability due to an essential problem of an organic compound. However, in recent years, vigorous research has been conducted on electron transporting materials in the field of electrophotographic photoreceptors. These compounds can also be preferably used.
For example, trinitrofluorenone described in JP-B-50-10964, dicyanomethylenefluorenone derivative described in JP-A-61-143764, anthraquinone derivative described in JP-A-61-2225151, The thiopyran derivatives described in JP-A-60-222477, the fluorenone derivatives described in JP-A-5-279582, JP-A-7-233134, JP-A-7-258189, etc. Benzoxazole or benzothiazole derivatives described in JP-A No. 245601, JP-A-8-283249, JP-A-8-301858, JP-A-8-286402, etc., and JP-A-8-15878 Benzoquinone derivatives, Journal of Electrophotographic Society, Volume 30 3 266 (1991), JP-A-5-25136, JP-A-5-25174, JP-A-5-117274, JP-A-5-125043, JP-A-5-132464. The imide compound derivatives described in Japanese Patent Publication No. 5 or the like, or electron transporting groups described in JP-A Nos. 52-12153, 52-12154, Macromolecules, 22, 2266 (1989), etc. An electron transporting polymer introduced into the polymer can be used.

  Furthermore, for example, JP-A-8-248656, JP-A-8-240921, JP-A-8-157476, JP-A-8-151534, JP-A-8-151532, JP-A-151533, 8- Various acceptor compounds described in JP-A Nos. 245601, 8-245518, 8-231502, 8-113565, 8-21635, and the like are also preferably used.

  When these hole transporting materials and electron transporting materials are used in combination, if the hole transporting material and the electron transporting material form a charge transfer (CT) complex, they are colored or moved. The degree may decrease. Since the CT complex is more likely to be formed as the π electron orbit of the hole transporting material and the electron transporting material becomes closer spatially, it is preferable to use a CT complex having a bulky substituent that inhibits spatial access. .

From the above viewpoint, as a combination of the low-molecular charge transporting materials, an aromatic tertiary amino compound or an aromatic tertiary diamino compound having a bulky substituent is used as the hole transporting material. In contrast, it is preferable to use a combination of a fluorenone derivative having a bulky substituent or a diphenoquinone derivative as a low molecular weight electron transporting material.
Further, the mixing mass ratio (A / B) of the hole transporting material A and the electron transporting material B is preferably in the range of 9/1 to 1/9, and in the range of 7/3 to 3/7. More preferably.

In the bipolar photoreceptor layer 34, when both the hole transporting material and the electron transporting material are low molecular materials, various binder resins can be used to improve the film forming property. As the binder resin, polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polystyrene resin, phenol-formaldehyde resin and the like are applicable.
In particular, when a polycarbonate resin is used as a binder, it is very effective because it improves the characteristics of the charge transport material.

The content of the low-molecular charge transporting material combined with the hole transporting material and the electron transporting material in the bipolar photoreceptor layer is preferably in the range of 20 to 90% by mass, and 40 to 70% by mass. % Is more preferable.
When the content is less than 20% by mass, the photosensitivity is not sufficient and good display characteristics for optical writing may not be obtained when used for an optical writing type display medium. If it exceeds 90% by mass, the entire photosensitive layer may become brittle and the durability of the optical writable display medium may be reduced.

  In the present invention, it is preferable to use a combination of a low molecular electron transport material as the electron transport material and a hole transport polymer as the hole transport material for the bipolar photoreceptor layer 34. When a bipolar photoconductor layer is produced by combining the low molecular weight hole transporting material and the electron transporting material described above and dispersing in a binder resin, obtain a certain degree of mobility for both positive and negative charges. In this case, the bipolar photoconductor layer 34 must be formed by mixing a considerable amount of charge transporting materials, and not only the mixing property of the two is bad, but also the formed film becomes brittle and durable in actual use. Sex etc. may be a problem.

  In particular, when the present inventors dispersed a low molecular electron transport material in a hole transport polymer, uniformity was maintained even when a considerable amount of the electron transport material was mixed, and the charge generation material The present inventors have found that even when a bipolar photosensitive layer is formed by mixing, the mobility of positive and negative charges can be improved in a well-balanced manner without deterioration in film quality.

  The hole transporting polymer is preferably at least one of hole transporting polymers represented by the following general formulas (I-1) and (I-2). Such a hole transporting polymer has an excellent triphenylamine structure as a basic unit of hole transport, and thus has a high hole transporting property and a flexible connection structure, so that it is a low molecular compound. Excellent dispersibility.

In general formulas (I-1) and (I-2), Y and Z each independently represent an arbitrary organic group, A represents an organic group represented by the following general formula (II-1), and B and B Each independently represents —O— (Y—O) _m —H or —O— (Y—O) _m —CO—Z—CO—OR ′ (where R ′ represents a hydrogen atom, substituted or unsubstituted Represents an alkyl group, a substituted or unsubstituted aryl group, Y and Z each independently represents an arbitrary organic group.), M represents an integer of 1 to 5, and p represents an integer of 5 to 5000. .

  In General Formula (II-1), Ar represents a substituted or unsubstituted aromatic group, X represents a substituted or unsubstituted aromatic group, T represents —O— or any organic group, k, n represents an integer of 0 or 1 each independently.

Specific examples of X, Y, Z, Ar, and T in the general formulas (I-1), (I-2), and (II-1) include the following organic groups.
First, X is preferably an organic group selected from the following groups (IV-1) to (IV-2).

In the organic groups (IV-1) to (IV-2), R ₁₀ and R ₁₁ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, substituted or unsubstituted. A phenyl group, a substituted or unsubstituted aralkyl group, or a halogen atom, a represents 0 or 1, and V represents any one selected from the following organic groups (V-1) to (V-10): To express. However, in organic group (V-1)-(V-10), b represents the integer of 1-10, c represents the integer of 1-3, respectively.

  Suitable examples of Y and Z include groups independently selected from the following organic groups (VI-1) to (VI-7).

In the organic groups (VI-1) to (VI-7), R ₁₂ and R ₁₃ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, substituted or unsubstituted. A phenyl group, a substituted or unsubstituted aralkyl group, or a halogen atom, d and e each independently represents an integer of 1 to 10, f and g each independently represents an integer of 0, 1 or 2, h And i each independently represents 0 or 1. Moreover, V is synonymous with V in organic group (IV-1)-(IV-2).

  Ar represents a substituted or unsubstituted aromatic group, preferably a substituted or unsubstituted aromatic group having 2 or more aromatic rings, more preferably a polynuclear aromatic ring having 2 to 10 aromatic rings, or a substituted or unsubstituted group It is a condensed aromatic ring having 2 to 10 aromatic rings. Specifically, for example, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted phenanthrenyl group, or a substituted Alternatively, an unsubstituted pyrenyl group is preferred.

  Here, examples of the substituent of the polynuclear aromatic ring or condensed aromatic ring include a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a substituted amino group, and a halogen atom. As said alkyl group, a C1-C10 thing is preferable, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group etc. are mentioned. As said alkoxy group, a C1-C10 thing is preferable, for example, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group etc. are mentioned. As said aryl group, a C6-C20 thing is preferable, for example, a phenyl group, a toluyl group, etc. are mention | raise | lifted. As said aralkyl group, a C7-C20 thing is preferable, For example, a benzyl group, a phenethyl group, etc. are mentioned. Examples of the substituent of the substituted amino group include an alkyl group, an aryl group, and an aralkyl group, and specific examples are as described above.

  T is —O— or an arbitrary organic group, preferably a hydrocarbon group, more preferably a divalent linear hydrocarbon group having 1 to 6 carbon atoms or a divalent hydrocarbon group having 2 to 10 carbon atoms. It is a branched hydrocarbon group. The specific structure of T is shown below.

  In the hole transporting polymer in the present invention, X in the general formula (II-1) is an organic group represented by the following general formulas (III-1), (III-2) and (III-3). It is particularly preferable that either one is used. This is because a polymer having such a biphenyl structure or terphenyl structure has high charge mobility and high practicality.

  The degree of polymerization (p) of the hole transporting polymer in the present invention is 5 to 5000, but is preferably in the range of 10 to 1000 for reasons such as film formability and device stability. The weight average molecular weight Mw is preferably in the range of 10,000 to 300,000.

  Specific examples of the compound having a structure represented by the general formula (I-1) for the hole transporting polymer in the present invention are shown below, but are not limited thereto. In addition, the thing whose column of Z is "-" shows the specific example of the hole transportable polymer shown by general formula (I-1), and others show the hole transport shown by general formula (I-2). Specific examples of functional polymers are shown. Hereinafter, a specific example given each compound number, for example, a specific example given number 15 is referred to as a hole transporting polymer (15).

Next, a method for synthesizing the hole transporting polymer in the present invention will be described, but the present invention is not limited thereto.
First, the monomer having a hole transporting structure used for the synthesis of the hole transporting polymer in the present invention will be described. For example, a compound represented by the following general formula (VII-1) reacts with a corresponding diarylamine derivative and a bishalogenated biphenyl derivative (when X is a biphenyl structure) as a charge transporting active monomer, or a corresponding halogen. Can be easily synthesized by reacting a fluorinated benzene derivative with a diarylbenzidine derivative (when X has a biphenyl structure).

Next, the hole transport active monomer represented by the following general formula (VII-1) is polymerized by a known method described in, for example, the 4th edition, Experimental Science Course Vol. Functional polymers can be synthesized. In general formula (VII-1), Ar, X, T, k, and n are the same as Ar, X, T, k, and n in general formula (II-1). A ′ represents a hydroxyl group, a halogen atom, or a group —O—R ₁₄ . Here, R ₁₄ represents an alkyl group, a substituted or unsubstituted aryl group, or an aralkyl group.

That is, the hole transporting polymer in the present invention can be synthesized, for example, as follows.
(1) When A ′ is a hydroxyl group When A ′ is a hydroxyl group, for example, an equivalent amount of dihydric alcohols represented by HO— (YO) _m —H are mixed, and dehydration condensation is performed using an acid catalyst. Polymerize by esterification reaction. As the acid catalyst, those used for usual esterification reaction such as sulfuric acid, toluenesulfonic acid, trifluoroacetic acid and the like can be used, and 1/10000 to 1/10 parts by weight, preferably 1 part by weight of the hole transporting active monomer. Is used in the range of 1/1000 to 1/50 parts by mass. In order to remove water generated during the synthesis, it is preferable to use a solvent that can be azeotroped with water, and toluene, chlorobenzene, nitrobenzene, 1-chloronaphthalene and the like are effective, and 1 part by mass of the hole transporting active monomer On the other hand, it is used in the range of 1 to 100 parts by mass, preferably 2 to 50 parts by mass. The reaction temperature can be arbitrarily set, but it is preferable to carry out the reaction at the boiling point of the solvent in order to remove water generated during the polymerization. After completion of the reaction, if no solvent is used, dissolve in a soluble solvent. If a solvent is used, the reaction solution is left as it is, with alcohols such as methanol and ethanol, and polymers such as acetone. The solution is dropped in a poor solvent that is difficult to dissolve, and a hole transporting polymer is precipitated, and after separating the hole transporting polymer, it is sufficiently washed with water or an organic solvent and dried. Furthermore, if necessary, the reprecipitation treatment may be repeated in which it is dissolved in a suitable organic solvent, dropped into a poor solvent, and the hole transporting polymer is precipitated. The reprecipitation treatment is preferably carried out with efficient stirring with a mechanical stirrer or the like. The solvent for dissolving the hole transporting polymer in the reprecipitation treatment is used in the range of 1 to 100 parts by weight, preferably 2 to 50 parts by weight, with respect to 1 part by weight of the hole transporting polymer. The poor solvent is used in an amount of 1 to 1000 parts by mass, preferably 10 to 500 parts by mass with respect to 1 part by mass of the hole transporting polymer.

(2) When A ′ is a halogen When A ′ is a halogen, for example, an equivalent amount of a dihydric alcohol represented by HO— (YO) _m —H is mixed, and an organic base such as pyridine or triethylamine is used. Polymerization is performed using a neutral catalyst. An organic basic catalyst is used in 1-10 equivalent with respect to 1 mass part of positive hole transport monomers, Preferably it is 2-5 equivalent. As the solvent, methylene chloride, tetrahydrofuran (THF), toluene, chlorobenzene, 1-chloronaphthalene and the like are effective, and 1 to 100 parts by weight, preferably 2 to 50 parts by weight with respect to 1 part by weight of the hole transporting monomer. Used in the range of parts. The reaction temperature can be arbitrarily set. After the polymerization, reprecipitation treatment is performed as described above, and purification is performed. Further, when the divalent alcohol is a divalent alcohol having a high acidity such as bisphenol, an interfacial polymerization method can also be used. That is, polymerization can be carried out by adding water to a dihydric alcohol, adding an equivalent base and dissolving it, and then adding the bivalent alcohol and an equivalent hole transporting active monomer solution with vigorous stirring. Under the present circumstances, water is used in 1-1000 mass parts with respect to 1 mass part of dihydric alcohols, Preferably it is 2-500 mass parts. As the solvent for dissolving the hole transporting active monomer, methylene chloride, dichloroethane, trichloroethane, toluene, chlorobenzene, 1-chloronaphthalene and the like are effective. The reaction temperature can be arbitrarily set, and in order to promote the reaction, it is effective to use a phase transfer catalyst such as an ammonium salt or a sulfonium salt. The phase transfer catalyst is used in the range of 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, with respect to 1 part by mass of the hole transporting active monomer.

(3) When A ′ is —O—R ₁₄ When A ′ is —O—R ₁₄ , first, an excessive amount of a dihydric alcohol represented by HO— (YO) _m —H is added, and sulfuric acid is added. Inorganic acid such as phosphoric acid, titanium alkoxide, acetate or carbonate such as calcium and cobalt, and oxide of zinc are heated as a catalyst, and A ′ is converted to —O— (YO) _m by transesterification. -H and then polymerized by de-HO- (YO) _m -H condensation esterification reaction. The dihydric alcohol is used in the range of 2 to 100 equivalents, preferably 3 to 50 equivalents with respect to 1 equivalent of the hole transporting monomer. A catalyst is used in 1 / 1000-1 mass part with respect to 1 mass part of positive hole transport monomers, Preferably it is the range of 1 / 100-1 / 2 mass part. The reaction is carried out at a reaction temperature of 200 to 300 [° C., from _{-O-R 14 -O- (Y-} O-) transesterification after the end of the _m -H is HO- of (Y-O-) _m -H de In order to accelerate the polymerization reaction due to separation, the reaction is preferably carried out under reduced pressure. Also, HO- (YO-) _m- H is removed azeotropically under reduced pressure using a high-boiling solvent such as 1-chloronaphthalene that can be azeotroped with HO- (YO-) _m- H. Can also be reacted.

As described above, the hole transporting polymer in the present invention can be easily synthesized.
In addition to the hole transporting polymer, the bipolar photoconductor layer 34 is mixed with other low-molecular electron transporting materials. As the electron transporting material, any of the low molecular weight materials among the electron transporting materials exemplified above can be used. As with the low molecular charge transporting materials, a hole transporting polymer and an electron are used. It is preferable not to form a CT complex with the transport material. Similarly, it is preferable to use a material having a bulky substituent as the electron transport material.

From the above viewpoint, as the hole transporting polymer, it is preferable to use a polymer in which Ar in the general formula (II-1) is a bulky aromatic group having 2 or more substituted or unsubstituted aromatic rings. In contrast, it is preferable to use a combination of a fluorenone derivative having a bulky substituent or a diphenoquinone derivative as a low molecular weight electron transporting material.
Further, the mixing mass ratio (C / D) of the hole transporting polymer C and the electron transporting material D is preferably in the range of 9/1 to 1/9, and is preferably 7/3 to 3/7. It is more preferable to set the range.

  As a method for producing the bipolar photosensitive layer 34, a dry film forming method such as a vacuum deposition method or a sputtering method, or a wet coating method such as a spin coating method or a dip method using a solution or a dispersion liquid can be applied. In the case of the wet coating method, aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene, ketones such as acetone, 2-butanone and cyclopentanone, and halogenated fats such as methylene chloride, chloroform and ethylene chloride Ordinary organic solvents such as aromatic hydrocarbons, cyclic ethers such as tetrahydrofuran and ethyl ether, or straight-chain ethers can be used alone or in admixture of two or more.

As a method for preparing the coating solution, a charge generating material and a charge transporting material may be mixed with the above solvent at the same time, but only the charge generating material (in combination with a binder resin if necessary) in advance is ball milled. In order to obtain a coating liquid having good dispersibility, it is preferable to disperse in a solvent with ultrasonic waves or the like and then add the charge transporting material.
In addition, the dispersed particle diameter of the charge generating material in the coating solution is preferably in the range of 0.01 to 0.2 μm in terms of volume average particle diameter from the viewpoint of increasing sensitivity.

  The film thickness of the ambipolar photoreceptor layer 34 is generally in the range of 1 to 100 μm, and more preferably in the range of 1 to 10 μm. If the thickness is less than 1 μm, the withstand voltage may be lowered and it may be difficult to ensure reliability. If the thickness is greater than 10 μm, impedance matching with a functional element may be difficult and design may be difficult.

  The mobility is measured accurately by measuring the film thickness of the bipolar charge transport layer formed on the ITO substrate to about 5 μm, Au is provided on the upper part by sputtering, and an electric field of 10 V / μm is applied to the film. In this state, the transient photocurrent that flows when a nitrogen gas laser (pulse width: 10 nsec) is irradiated is observed by a normal TOF method (Time-of-flight method), and the Transit Time is measured. The measurement was performed in an environment of 20 ° C.

  The optical switching layer according to the present invention has an excellent response symmetry when an AC electric field is applied to the optical switching layer and irradiated with light, and an upper charge generation layer such as a dual CGL structure is applied. The optical switching layer can be manufactured at a high quality and at a low cost, and the charge transport layer is not damaged during the formation of the upper charge generation layer. No photosensitivity degradation occurs.

(Display layer)
As shown in FIG. 1, a display element 40 is electrically connected to the optical switching layer. The optical switching layer 30 and the display element 40 may be connected in series, in parallel, or a combination thereof. Furthermore, it may be connected to other elements.

  The optical writing type display medium 20 can be used as an optical writing type liquid crystal spatial modulation element when a liquid crystal element is used as the display element 40. In particular, since the liquid crystal element is basically driven by alternating current and dislikes the direct current component, the application of the optical switching layer is effective. The liquid crystal that can be used is nematic, smectic, discotic, cholesteric, and the like.

Further, it is preferable to use a display layer 43 having a memory property as the display element 40. Examples of the display layer 43 having a memory property include a liquid crystal display layer 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, it is a ferroelectric liquid crystal such as a polymer dispersed liquid crystal (PDLC) or a chiral smectic C phase, or a cholesteric liquid crystal. Further, a liquid crystal layer encapsulating them can also be applied. The liquid crystal having a memory property does not require power for holding an image display due to the memory property, and the display medium can be used separately from the optical writing device.
Note that examples of the display element 40 including the display layer 43 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.

Further, in the present invention, when the optical switching layer 30 and the display element 40 as described above are connected, it is preferable to integrate them into the optical writing type display medium 20. By integrating, the connection between the optical switching layer 30 and the display element 40 can be stabilized.
In particular, it is effective to integrate the display element 40 having a memory property and the optical switching layer 30. The optical writing type display medium 20 in which these are integrated can be separated from the main body (optical writing device) that drives the device. Therefore, for example, a display medium separated from the main body can be distributed. Moreover, the user can browse in a free posture in a free place.

  Of course, the present invention can also be applied to separating only the image display on the display unit. However, since it may be difficult to ensure reliability when the display element 40 and the optical switching layer 30 are connected again, it is more effective to integrate the display element 40 and the optical switching layer 30. is there.

  As the integration method, it is advantageous from the viewpoint of ease of manufacturing and stabilization of the display function that the optical switching layer 30, the functional layer 50, and the display element 40 are sequentially stacked and integrated. It is. Examples of the functional layer 50 include an isolation layer for isolating the optical switching layer 30 and the display element 40, a DC component removing functional film, and the like. In the case of a device provided with the functional film for removing a direct current component, the response symmetry when driven by an alternating electric field is further improved.

  As the optical writable display medium 20 of the present invention, a device (image display medium) in which a liquid crystal element having a memory property and an optical switching layer are integrated is particularly effective. Among the liquid crystal elements having the above memory properties, cholesteric liquid crystal has high reflectivity and excellent display performance. Therefore, a device in which a cholesteric liquid crystal display element and an optical switching layer are integrated is particularly an optical writable display. Desirable as a medium.

<Writing to optically writable display media>
The optically writable display medium according to the present invention has, for example, an image-like light from the transparent substrate side when an alternating voltage is applied to a pair of electrodes, at least one of which is a transparent electrode, and one is a non-transparent substrate. It is possible to write by irradiating.

  Although the applied voltage is an AC voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be applied as a waveform, and a combination of these may be used or an arbitrary waveform may be used. Of course, depending on the configuration of the display element layer and the like, a slight DC component application may be effective, but this may be applied.

  FIG. 3 shows an example of the concept of a system for writing on the optically writable display medium of the present invention. In FIG. 3, on a light incident side substrate 31 such as glass or plastic, a transparent electrode 32, a light switching layer comprising an ambipolar photoreceptor layer 34, a display layer 43, a transparent electrode 42, and a display side substrate 41. The system which writes in the optical writable display medium 20 of this invention comprised from these is shown.

The upper and lower transparent electrodes 32 and 42 of the optical writable display medium 20 are connected to the connector 14 so that a voltage can be applied by the voltage applying means 16. The optical writing device is configured by the connector 14, the voltage applying means 16, the optical writing means 12, and the control means 18 for controlling the voltage applying means 16 and the optical writing means 12. The optical writing devices may be combined into one or separated.
The connector 14 is a connector for connecting to the transparent electrode 32 and the transparent electrode 42, and has a contact on each side. Of course, this can be removed freely.

  The voltage application means 16 applies a voltage pulse for display in synchronization with optical writing by the optical writing means, and has means for generating an applied pulse and means 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 applying a DA conversion to a waveform read from the ROM when a voltage is applied and applying it to the optically writable display medium is applied. A means for generating a pulse by an electric circuit method such as a pulse generation circuit instead of a ROM is applicable, but there is no particular limitation as long as it is a means for applying a drive pulse. Can be used.

The optical writing unit 12 includes a unit that generates a light pattern to be irradiated on the light incident side of the optical writing type display medium 20 and a light irradiation unit that irradiates the optical writing type display medium 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, a fluorescent light, a halogen lamp, an electroluminescence (EL) light, or the like is applicable. Further, 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 applicable. In addition to the above, any means that can control the amount of light to be irradiated, the wavelength, and the irradiation pattern can be applied without any problem.
The control means 18 is constituted by means for controlling the operation of the above means in addition to converting the image data sent to display data.

  The optically writable display medium of the present invention can write an image by the optical writing device having the above-described configuration, and the image once written on the optically writable display medium 20 is retained even after being removed from the connector 14. Can be used for browsing, circulation, distribution, etc. Further, by connecting to the connector 14 again and applying a voltage, the written image can be erased and another image can be written again, so that it can meet the demand for resource saving. .

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention.

<Example 1>
(Production of optical writable display medium)
-Optical switching layer-
An ambipolar photoreceptor layer was formed on the ITO film of a polyethylene terephthalate (PET) substrate (thickness: 125 μm) on which an ITO film (thickness: 800 mm) was formed as an electrode. Specifically, first, hydroxygallium phthalocyanine as a charge generation material (X-ray diffraction spectrum black angle (2θ ± 0.2 °) is 7.0 °, 7.5 °, 10.5 °, 11. 7), 12.7 °, 17.3 °, 18.1 °, 24.5 °, 26.2 °, and 27.1 ° having strong diffraction peaks) are dispersed by dynomill using monochlorobenzene. Thus, a charge generation material dispersion liquid (CG liquid) having a concentration of 5% by mass was prepared.

On the other hand, 10 parts by mass of 3,3′-dimethyl-5,5′-dicyclohexyldiphenoquinone, which is a low-molecular electron transporting material, and 10 parts by mass of the hole-transporting polymer (32) exemplified above, A charge transporting material solution (CT solution) 1 was prepared by dissolving in 80 parts by mass of chlorobenzene.
The CG solution and the CT solution 1 were mixed so that the mass ratio (CG / CT) of the charge generating material CG and the charge transporting material CT as a solid content was 2/98 to obtain a coating solution. This was applied by a spin coating method and dried to form a bipolar photoreceptor layer having a thickness of 5 μm on the ITO film.

-Optically writable display medium-
Using the produced optical switching layer, a 3% by weight aqueous solution of polyvinyl alcohol was applied as a separating layer on the bipolar photosensitive layer by spin coating, and a polyvinyl alcohol film (film thickness: 0.2 μm) was applied. Formed. Further, a light shielding film, a display element layer made of capsule liquid crystal, a transparent electrode layer, and a transparent substrate were formed on the isolation layer as follows.

  74.8 parts by mass of nematic liquid crystal E8 (manufactured by Merck) having positive dielectric anisotropy, 21 parts by mass of chiral agent CB15 (manufactured by BDH), and 4.2 parts by mass of chiral agent R1011 (manufactured by Merck) Was heated and dissolved, and then returned to room temperature to obtain a chiral nematic liquid crystal that selectively reflects blue-green color light. To 10 parts by mass of this blue-green chiral nematic liquid crystal, 3 parts by mass of an adduct of 3 molecules of xylene diisocyanate and 1 molecule of trimethylolpropane (D-110, manufactured by Takeda Pharmaceutical Co., Ltd.) and 100 parts by mass of ethyl acetate are added to obtain a uniform solution. And a liquid to be an oil phase was prepared. On the other hand, 10 parts by weight of polyvinyl alcohol (PVA 217EE manufactured by Kuraray Co., Ltd.) was added to 1000 parts by weight of heated ion-exchanged water, stirred, and then allowed to cool to prepare a liquid that became an aqueous phase.

  Next, 10 parts by mass of the oil phase was emulsified and dispersed in 100 parts by mass of the aqueous phase for 1 minute by a household mixer to which an alternating current of 30 V was applied by a slidac, and oil phase droplets were dispersed in the aqueous phase. An oil-in-water emulsion was prepared. The oil-in-water emulsion was stirred for 2 hours while being heated in a 60 ° C. water bath to cause interfacial polymerization to form liquid crystal microcapsules. When the average particle diameter of the obtained liquid crystal microcapsule was measured by a laser particle size distribution meter, it was estimated to be about 12 μm. The obtained liquid crystal microcapsule dispersion was filtered through a stainless steel mesh having a mesh size of 38 μm, and allowed to stand for a whole day and night, and the milky white supernatant was removed to obtain a slurry having a solid component of about 40% by mass consisting of liquid crystal microcapsules. A coating liquid B was prepared by adding an aqueous solution of 10% by mass of polyvinyl alcohol containing polyvinyl alcohol in an amount of 2/3 to the mass of the solid component to the obtained slurry.

By applying the coating liquid B on the ITO film surface of the PET film with the ITO film by a wire bar method, a display layer containing liquid crystal was formed to produce a display element.
On the other hand, after applying a black polyimide BKR-105 (manufactured by Nippon Kayaku) on the isolation layer surface of the PET film on which the optical switching layer and the isolation layer are formed in advance, a light shielding film (thickness: 1 μm) is formed. Further, Dick Dry WS-321A / LD-55 (Dainippon Ink Chemical Co., Ltd.), which is a dry laminate adhesive, was applied and dried to form an adhesive layer having a thickness of 1 μm. A PET film having a display layer formed thereon was adhered onto the adhesive layer so that the display layer and the adhesive layer were in contact with each other, and was laminated at 70 ° C. to obtain a monochrome display photo-writing display medium.

(Evaluation of optical writable display media)
The produced display medium was evaluated as follows, and it was verified that it functions effectively as an optically writable display medium.
-Initial display characteristics-
For the light irradiation, an LED light source having a peak at 660 nm was used. The amount of light at the time of light (Photo) was 500 μW / cm ² . The drive voltage was changed from 0 to 600 V at 50 Hz and 8 pulses. The voltage pulse was a rectangular wave, the first pulse was a positive pulse, and the second pulse was a negative pulse. In addition, the case where the transparent electrode of the light irradiation side substrate is positively applied is defined as positive polarity. Similarly, the reflectance at dark time (Dark) was examined. In addition, the change of the reflectance accompanying voltage application was measured by X-rite 404 (made by X-rite) as a reflection optical density.

  As a result, the maximum contrast (the maximum value of the light / dark ratio of the display layer reflectivity when the voltage is fixed) is 13, and the drive margin (the voltage width at which a contrast of 50% or more of the maximum light / dark ratio is obtained) is 300V. A value was obtained.

-Durability-
Using the optical writing device shown in FIG. 3, a voltage was applied to the produced optical writing type display medium to attempt monochrome image display. A rectangular wave, 50 Hz, 8 pulses, and 300 V were applied as writing pulses. As the drive pulse, the first pulse was a negative pulse, the second pulse was a positive pulse, and this was sequentially applied up to the eighth pulse, and the final eighth pulse was a positive 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.
When this operation was repeated, image deterioration such as color unevenness due to unerased residue did not occur even after 1000 times or more.

<Example 2>
In the production of the optical switching element of Example 1, the optical switching element was produced in the same manner except that the hole transporting polymer (64) was used instead of the hole transporting polymer (32) in the CT solution 1. Further, an optical writable display medium was obtained in the same manner as in Example 1.

Evaluation similar to Example 1 was performed using this optical writing type display medium. As a result, good values of maximum contrast of 12 and drive margin of 250V were obtained. Further, the durability was not deteriorated by 1000 times or more, and image deterioration such as color unevenness did not occur.
In addition, compared with the optical switching layer of Example 1, the optical switching layer of Example 2 was excellent in resistance to mechanical stresses such as bending and cutting. This is because the hole transporting polymer used in Example 2 is a copolymer type of a hole transporting active monomer represented by the general formula (I-2) and a low molecular weight monomer. The charge mobility is inferior to that of the type represented by the formula (I-1), but is presumed to be excellent in mechanical properties such as flexibility.

<Comparative Example 1>
A lower charge generation layer was formed on the ITO film of a polyethylene terephthalate (PET) substrate (thickness: 125 μm) on which an ITO film (thickness: 800 mm) was formed as an electrode. Specifically, first, hydroxygallium phthalocyanine (X-ray diffraction spectrum black angle (2θ ± 0.2 °) is 7.0 °, 7.5 °, 10.5 °, 11.7 °, 12. 7), 17.3 [deg.], 18.1 [deg.], 24.5 [deg.], 26.2 [deg.] And 27.1 [deg.] Having a strong diffraction peak) and a carboxyl-modified vinyl chloride-acetic acid as a binder resin A vinyl copolymer (manufactured by Union Carbide Co., Ltd., VMCH) was used, and the mass ratio was set to 1: 1, and monochlorobenzene was used and dispersed with a dyno mill to prepare a dispersion having a solid content concentration of 4% by mass. This was applied to a substrate by spin coating and then dried to form a lower charge generation layer having a thickness of about 0.1 μm.

  N, N-bis (3,4-dimethylphenyl) bisphenyl-4-amine (CTM A) as the hole transport material and poly (4,4′-cyclohexylidene diphenylene carbonate) (bisphenol-Z) as the binder resin , Manufactured by Mitsubishi Gas Chemical Co., Ltd., weight average molecular weight: 30,000), were mixed at a mass ratio of 1: 1, and then dissolved in monochlorobenzene to prepare a 20% by mass solution.

By applying and drying this by spin coating, a charge transport layer having a thickness of 5 μm is formed on the lower charge generation layer, and a film having a thickness of about 0.3 μm is formed thereon using the charge generation material dispersion liquid. An upper charge generation layer was formed to produce an optical switching layer having a dual CGL structure.
In this case, when the upper charge generation layer is formed, a remarkable coating defect that may be caused by dissolution or swelling of the charge transport layer occurs, and it cannot be applied to the optical switching layer for the optical writable display medium. Met.

<Comparative example 2>
An optical switching layer was prepared in the same manner as in Example 1 except that no electron transport material was used in Example 1, and an optical writable display medium was prepared in the same manner as in Example 1 using the optical switching layer. The same evaluation was performed.
As a result of the evaluation, the maximum contrast was 5 or less, the drive margin was as narrow as 50 V or less, and the contrast was remarkably lowered after several repetitions, so that it was not practical for an optical writing type display medium.

As described above, in the optical writing type display medium in the example, good optical writing characteristics and repeated stability were obtained.
On the other hand, in Comparative Example 1, a fatal coating defect occurred when the upper charge generation layer was applied. In Comparative Example 2, the AC drive suitability was insufficient, and it did not function effectively as an optical switching layer. As a medium, it could not withstand practical use.

It is a schematic block diagram which shows one form of the optical writable display medium of this invention. It is a schematic block diagram which shows one form of the optical switching element in this invention. It is a schematic block diagram which shows an example of the concept of the system which writes in the optical writable recording medium of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Optical writing means 14 Connector 16 Voltage application means 18 Control means 20 Optical writing type display medium 30 Optical switching layer 31, 41 Substrate 32, 42 Electrode 34 Bipolar photosensitive layer 40 Display element 43 Display layer 50 Functional layer

Claims (6)

An optically writable display medium including at least a display layer and an optical switching layer between a pair of electrodes,
The optical writing type display medium, wherein the optical switching layer has a single-layer ambipolar photosensitive layer containing a charge generating material, a hole transporting material and an electron transporting material.   2. The optically writable display medium according to claim 1, wherein the electron transporting material is a low molecular weight electron transporting material, and the hole transporting material is a hole transporting polymer. The hole transporting polymer is at least one of hole transporting polymers represented by the following general formulas (I-1) and (I-2). Optically writable display medium.

(In General Formulas (I-1) and (I-2), Y and Z each independently represent an arbitrary organic group, A represents an organic group represented by the following General Formula (II-1), and B and B ′ is independently —O— (YO) _m —H or —O— (YO) _m —CO—Z—CO—OR ′ (where R ′ is a hydrogen atom, substituted or unsubstituted Represents an alkyl group, a substituted or unsubstituted aryl group, Y and Z each independently represent an arbitrary organic group.), M represents an integer of 1 to 5, and p represents an integer of 5 to 5000. To express.)

(In the general formula (II-1), Ar represents a substituted or unsubstituted aromatic group having 2 or more aromatic rings, X represents a substituted or unsubstituted aromatic group, and T represents —O— or an arbitrary group. Represents an organic group, and k and n each independently represents an integer of 0 or 1.)   The optical writable display medium according to claim 3, wherein Ar in the organic group represented by the general formula (II-1) is a substituted or unsubstituted aromatic group having 2 or more aromatic rings. X in the organic group represented by the general formula (II-1) is any one of organic groups represented by the following structural formulas (III-1), (III-2), and (III-3). The optically writable display medium according to claim 4.

  6. The optically writable display medium according to claim 1, wherein the display layer is a liquid crystal display layer having a memory property.

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