JPH075418A - Electrostatic recording sheet and electrostatic recording method - Google Patents

Abstract

PURPOSE:To enable recording and erasing which are thermally reversible with a high recording sensitivity and high-speed recording by incorporating a liquid crystalline polymer for executing reversible electrostatic recording into a recording layer. CONSTITUTION:The recording layer 2 contg. the liquid crystalline polymer is formed on a base material 1. This base material 1 may have the recording layer 2 and a conductive layer 3 thereon as well. An electric discharge is generated from a recording electrode and the recording layer side surface of an electrostatic recording sheet 1 is electrostatically charged when a voltage above a certain value is applied between the recording electrode and resistance electrode. The recording layer 2 is uniformly oriented and the domain expansion of the liquid crystal takes place if the recording layer 2 attains or exceeds the temp. at which the liquid crystal layer is formed. The parts where the light corresponding to the electrostatically charged parts is not diffused are formed and are thereafter immobilized by allowing the layer to cool and cooling the layer down to the glass transition point or below. The recording electrode is of a needle type and may be formed as a multineedle electrode head by lining up many needles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible electrostatic recording sheet on which information can be recorded, stored and erased and which can be repeatedly used, and a recording method thereof.

[0002]

2. Description of the Related Art Conventionally, as a recording method for a facsimile or the like, there has been an electrostatic recording method in which toner is attached to a charged portion of a non-recording material. Further, there are an electrostatic recording sheet that develops color by heating and a thermal transfer recording technology that transfers ink by heating, which have been used for recording documents and images.

On the other hand, Japanese Patent Laid-Open No. 1-184640 has been proposed as an optical recording medium capable of recording and erasing in the photothermal mode recording. Further, as repetitive thermal recording materials capable of recording and erasing visible information, JP-A-2-175280, JP-A-2-236518, and JP-A-3-159785.
No. Gazette is proposed.

[0004]

However, in the conventional electrostatic recording or thermal recording, it is not possible to delete the transfer toner, the color-developed portion or the transferred ink, so that it is difficult to reuse the recorded recording paper. There was a problem of being there.

Further, in the above-mentioned optical recording medium and repetitive thermal recording material, there is a problem that energy efficiency is not high and recording speed is slow because an optical head or a thermal head using a laser light source is used as a recording means. It was

In order to solve the above problems, the present invention provides an electrostatic recording sheet having high recording sensitivity and capable of thermally reversible recording and erasing, and an electrostatic recording method using the same, which enables high-speed recording. With the goal.

[0007]

In order to achieve the above object, the electrostatic recording sheet of the present invention is an electrostatic recording sheet having a recording layer on a substrate directly or via another layer,
The recording layer contains a liquid crystalline polymer for reversible electrostatic recording.

In the above structure, the liquid crystalline polymer is preferably a thermotropic liquid crystal polymer. Further, in the above structure, it is preferable to have a conductive layer between the base material and the recording layer.

In the above structure, it is preferable that the conductive layer is colored. Further, in the above structure, the conductive layer is preferably formed of a transparent conductive material.

In the above structure, the resistance value of the conductive layer is preferably 10 ⁶ to 10 ⁹ Ω / □. Further, in the above structure, it is preferable to have a heat resistant layer on the recording layer.

In the above structure, the surface roughness of the heat-resistant layer is preferably 1 to 15 μm in terms of center line surface roughness. Further, in the above structure, the heat resistant layer preferably contains particles having a particle diameter of 3 to 20 μm.

Further, in the above constitution, it is preferable that the heat resistant layer is selected from a curable resin and a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher. Further, in the above configuration,
The electrostatic recording sheet according to claim 1, which has an alignment film between the substrate or the conductive layer and the recording layer.

In the above construction, the base material is preferably selected from a curable resin and a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher. Next, the electrostatic recording method of the present invention comprises a stylus installed on the recording layer side of an electrostatic recording sheet having a recording layer containing a liquid crystalline polymer and a counter electrode or an electrostatic recording sheet installed on the other side of the electrostatic recording sheet. A voltage is applied between the conductive layers to cause discharge, and the recording layer side of the electrostatic recording sheet is charged, and before or after charging, heated to a temperature at which the liquid crystalline polymer forming the recording layer exhibits a liquid crystal phase or higher. ,
It is characterized in that the domain of the liquid crystal phase generated in the recording layer is expanded.

In the above structure, the domain size is uniformly reduced and the recording is erased by heating the liquid crystalline polymer to a temperature higher than the temperature at which the liquid crystalline polymer forms an isotropic phase and then allowing it to cool without applying an external electric field. It is preferable.

In the above structure, it is preferable that the stylus is a monostylus or a multistylus.

[0016]

According to the above-mentioned constitution of the present invention, since the recording layer contains the liquid crystalline polymer for performing reversible electrostatic recording, the electrostatic recording sheet having high recording sensitivity and capable of thermally reversible recording and erasing. In addition, an electrostatic recording method using this can be performed at high speed. That is, the light-scattering property of the recording layer composed of the liquid crystalline polymer can be controlled by the size of the domain formed in the liquid crystal phase.

The operation will be described in detail below. When the electrostatic recording sheet does not have a colored substrate, a conductive layer, or a light absorption layer, it is possible to observe the light incident on the electrostatic recording sheet from the direction opposite to the observer. The case is called "transmitted light observation", and the case of observing the light incident on the electrostatic recording sheet from the same direction as the observer is "reflected light observation".
Say.

When the size of the domain is about 10 μm or less, light scattering occurs due to the optical anisotropy between the domains. Therefore, when the reflected light is observed, the light is incident from the recording layer side. Most of the light is scattered and becomes diffuse reflected light before it reaches a colored object on the opposite side of the observer to the colored substrate, conductive layer, light absorbing layer or electrostatic recording sheet and is absorbed. , Bright white areas. In the case of observation of transmitted light, the transmitted light that goes straight due to scattering is reduced, so that a dark black portion can be obtained.

When the size of the domain is larger than the thickness of the recording layer, light incident on the recording layer does not scatter during transmission, so that the colored substrate, conductive layer, light absorbing layer or If there is a colored object on the side opposite to the observer with respect to the electrostatic recording sheet, it can be a dark black or colored portion in the observation of reflected light, a colored substrate or conductive layer,
When the electrostatic recording sheet does not have a light absorption layer, it can be a bright white portion for transmitted light observation.

Further, since the recording layer contains a liquid crystalline polymer, it is possible to record by partially expanding the domain size by applying an external electric field to the recording layer in a temperature range exhibiting a liquid crystal phase. Furthermore, when the liquid crystalline polymer is heated to a temperature above the temperature at which an isotropic phase is formed in the state where no external electric field is applied, the domain size can be uniformly reduced by allowing it to cool, so that it is possible to erase recording. is there. Further, since an external electric field can be applied by charging the surface of the electrostatic recording sheet with a multi-stylus head or the like, a sufficiently high recording speed can be obtained. Therefore, the electrostatic recording sheet of the present invention can be repeatedly recorded and erased, and can be used as a high-speed recording means.

According to the preferable constitution of the present invention in which the liquid crystalline polymer is a thermotropic liquid crystal polymer,
There is a liquid crystal phase that appears above the glass transition temperature and an isotropic phase that appears above the temperature at which the liquid crystal phase appears, and the liquid crystal phase also has a homogeneous monodomain state and a polydomain state composed of multiple domains. Exists. Light scattering strongly occurs in the liquid crystal phase of the polydomain, and almost no light scattering occurs in the liquid crystal phase or the isotropic phase of the monodomain.

When a conductive layer is provided between the base material and the recording layer, if charging is performed so that the surface potential is the same,
Since a larger electric field can be applied to the recording layer as compared with the case where the conductive layer is not provided, higher speed recording becomes possible.

Further, when the conductive layer is a transparent conductive material, it can be used for observation of transmitted light. Further, it is preferable in terms of conductivity that the resistance value of the conductive layer is in the range of 10 ⁶ to 10 ⁹ Ω / □.

When a heat-resistant layer is provided on the recording layer, heating by contact with a heating roller or the like can be performed from the recording layer side, and the efficiency of heating the recording layer can be increased. Furthermore, when the surface roughness of the heat-resistant layer is 1 to 15 μm in terms of the center line average roughness, first, the discharge start voltage becomes small in the gap between the recording needle electrode and the recording layer (or the heat-resistant layer). Since it is easy to set the thickness to about 15 μm, recording can be stably performed, and secondly, repulsion between charges in the charged portion is unlikely to occur, and charging is likely to be uniform, so that recording with high contrast can be performed.

Further, when the heat resistant layer contains particles having a particle size of 3 to 20 μm, the surface roughness of the heat resistant layer can be easily made to be about 1 to 15 μm in terms of center line average roughness.
The heat-resistant layer is a curable resin or has a heat distortion temperature of 100 ° C.
When the above thermoplastic resin is used, it is possible to prevent the recording layer from being deformed due to recording and erasing accompanied by heating, and the welding to a heating device. In the above, the curable resin includes a thermosetting resin and a photocurable resin.

If an alignment film is provided between the substrate or the conductive layer and the recording layer, the liquid crystalline polymer can be effectively operated. As the alignment film, a rubbing-processed or stretched film can be used in the case of a polymer film, and an oblique vapor deposition film can be used in the case of an inorganic compound.

When the base material is a curable resin or a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher, a material excellent in mass productivity and heat resistance can be obtained. In the above, the curable resin includes a thermosetting resin and a photocurable resin.

Further, in the electrostatic recording method of the present invention, since it is not necessary to selectively heat the recording portion, it is possible to provide a faster and reversible recording method. Further, according to a preferable configuration in which the domain size is uniformly reduced and recording is erased by heating the liquid crystalline polymer to a temperature at which the liquid crystalline polymer forms an isotropic phase or more and then allowing it to cool in a state where no external electric field is applied. , Can be easily erased.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The electrostatic recording sheet of the present invention has a recording layer containing a liquid crystalline polymer on a base material. Examples of the constitution of the electrostatic recording sheet of the present invention are shown in FIGS. 1, 2, 3, 4, 5, 6 and 7. 1 to 7, 1 is a base material, 2 is a recording layer, 3 is a conductive layer, 4 is a base material that also serves as a conductive layer, 5 is a heat-resistant layer, 6 is a transparent conductive layer, 7 is a light absorbing layer, and 8 is orientation. It is a film. When the electrode facing the head in recording is installed on the base material side of the electrostatic recording sheet, the recording layer 2 is directly formed on the base material 1 as shown in FIG. In this case, the conductive layer may not be formed.

As shown in FIG. 2, a recording layer 2 and a conductive layer 3 may be provided on the base material 1. In this case, the conductive layer is grounded or the like to serve as a counter electrode for the head. Further, as shown in FIG. 3, the base material 1 may also serve as the conductive layer 4. Furthermore, as shown in FIG. 4, a heat resistant layer 5 may be provided on the recording layer 2 on the opposite side of the conductive layer 3.

As a more preferable structure, a structure having a transparent conductive layer 6 and a light absorbing layer 7 between the recording layer 2 and the substrate 1 as shown in FIG. 5 can be mentioned. In this structure, the transparent conductive layer 6 made of a transparent conductive material usually has a higher refractive index than the recording layer, so that Fresnel reflection on the back surface of the recording layer is increased and the contrast is improved.

As a structure having the same effect, a structure having a high refractive index layer 9 and a conductive layer 3 between the recording layer 2 and the substrate 1 as shown in FIG. 6 can be mentioned. Further, when the recording layer 2 has the alignment film 8 on the side of the substrate 1 as shown in FIG. 7, the formation of the domains of the liquid crystalline polymer and the expansion of the domain size are promoted, so that the recording speed is improved. This is a more preferable configuration.

As the base material 1 for supporting each layer, a film formed of various thermoplastic resins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polysulfone, acrylic resin, polyethylene, polypropylene and various synthetic papers can be used. it can.

The recording layer 2 contains a liquid crystalline polymer. The liquid crystal polymer can control the domain size of the liquid crystal by an external electric field, has a specific temperature range in which the liquid crystal phase is exhibited, and can be fixed by placing it below the glass transition temperature of the liquid crystal polymer after recording, so that electrostatic recording is possible. It is possible.

Also in terms of contrast depending on the degree of light scattering property, there is a crystallization of low-molecular-weight compounds added between a small amount and between polymers, which is observed in a composition used for a recording layer of a reversible thermosensitive recording sheet. In contrast to a phase-separated polymer that induces light scattering due to the formation of amorphous domains by phase separation, a liquid crystalline polymer has a large light scattering effect because each liquid crystal phase is a set of domains and each domain has birefringence. Liquid crystalline polymers are superior.

In this embodiment, Japanese Patent Laid-Open No. 1-1846 is used.
40 gazette, the same 2-236518 gazette, the same 3-122.
The liquid crystalline polymers described in JP-A No. 623, JP-A No. 3-13887, JP-A No. 0478052, EP-A-044740 and the like can be used.
Examples of these liquid crystal polymers include the following (Chemical formula 1) to
(Chemical formula 11)

[0037]

[Chemical 1]

[0038]

[Chemical 2]

[0039]

[Chemical 3]

[0040]

[Chemical 4]

[0041]

[Chemical 5]

[0042]

[Chemical 6]

[0043]

[Chemical 7]

[0044]

[Chemical 8]

[0045]

[Chemical 9]

[0046]

[Chemical 10]

[0047]

[Chemical 11]

In the above (formula 1 to 11), n is 2 to
12 is a natural number, and m is a natural number of 2 to 100. ) Of course, other than this, a ferroelectric liquid crystal polymer or an antiferroelectric liquid crystal polymer can also be used.

The liquid crystalline polymer used in the present invention is preferably a thermotropic liquid crystal, and the mesophase may be any type of nematic, smectic and cholesteric. These liquid crystalline polymers include a main chain type liquid crystalline polymer in which a mesogenic group or a rigid atomic group is bonded by a flexible molecular chain and a side chain type liquid crystalline polymer having a mesogenic group or a rigid atomic group in the side chain. However, it is not particularly limited for use in the present invention, and a mixture of plural kinds or a mixture of low molecular weight liquid crystals may be used.

These liquid crystalline polymers have a liquid crystal phase that appears above the glass transition temperature and an isotropic phase that appears above the temperature at which the liquid crystal phase appears, and the liquid crystal phase also has a monodomain state and a plurality of homogeneously configured monodomains. There is a polydomain state consisting of Light scattering strongly occurs in the liquid crystal phase of the polydomain, and almost no light scattering occurs in the liquid crystal phase or the isotropic phase of the monodomain.

When there is no externally applied electric field, it is usually a polydomain, but when an electric field is applied, it becomes a monodomain state. Therefore, depending on whether or not the electric field is applied at the temperature which presents the liquid crystal layer, light scattering occurs. A state and a state free of light scattering can be formed.

Further, as the property of the liquid crystalline polymer used, it is preferable that the glass transition temperature is 60 ° C. or higher and 120 ° C. or lower in view of storage stability of recording and appropriate heating conditions during recording.

Specific examples of such a liquid crystalline polymer include liquid crystalline polymers represented by (Chemical formula 12) to (Chemical formula 19), but are not limited thereto.

[0054]

[Chemical 12]

[0055]

[Chemical 13]

[0056]

[Chemical 14]

[0057]

[Chemical 15]

[0058]

[Chemical 16]

[0059]

[Chemical 17]

[0060]

[Chemical 18]

[0061]

[Chemical 19]

Further, the recording layer may of course contain various additives such as an ultraviolet absorber and an antioxidant in addition to the liquid crystalline polymer. Further, it may contain a polymer that is not compatible with the liquid crystalline polymer. The polymer used in such a case preferably has the same refractive index as the principal axis refractive index of the liquid crystalline polymer in order to improve the contrast.

The resistance value of the conductive layer is preferably in the range of 10 ⁶ to 10 ⁹ Ω / □ from the viewpoint of conductive characteristics. It can be conveniently composed of a resin containing an electronically conductive or ionically conductive compound. Specifically, electron conductive compounds such as various metals, alkali metal salts, quaternary ammonium salts,
Ion-conducting compounds such as polyelectrolytes such as polystyrene sulfonate, gelatin, (modified or unmodified) cellulose, (completely or partially saponified) polyvinyl alcohol, polyvinyl acetal, polyvinyl formal,
It is configured by being dissolved or dispersed in various resins such as polyvinyl butyral, various acrylic resins, epoxy resins and urethane resins.

The conductive layer can also serve as a light absorbing layer described later by containing a colored conductive compound such as carbon black or a non-conductive dye or pigment. Specific examples of the structure of the transparent conductive layer include thin films of zinc oxide, tin oxide, indium tin oxide and the like. Since these materials not only have electronic conductivity but also have a high refractive index, they have the effect of increasing the scattering reflectance when the recording layer is in the light scattering state, and as a result, the contrast can be improved.

As the high refractive index layer, JP-A-2-1752 is used.
WO ₃ , Fe ₂ as listed in Japanese Patent Publication No. 80, etc.
O ₃ , PbO, ZnSc, Bi ₂ O ₃ , TiO ₂ , Si
Materials such as O can be used.

The light absorbing layer contains a material that absorbs light in the visible light region. Specific examples of the material that absorbs light in the visible light region include various dyes and pigments, but carbon black that can absorb the entire visible light region is relatively inexpensive and easy to use. For example, the light absorbing layer can be easily formed by dispersing these light absorbing materials in various resins.

Further, the light absorption layer itself may be a base material. It suffices that a material that absorbs light in the visible light region is dissolved or dispersed in the material for various base materials as described above.
Further, a metal layer having periodical unevenness also functions as a light absorbing layer. In the case of a metal layer having periodic unevenness, when the metal forming the metal layer has some absorption at the wavelength, it can efficiently absorb a wavelength equal to or longer than the unevenness cycle and can also serve as a conductive layer.

An example of the constitution of the electrostatic recording sheet in the case where such a metal layer having periodic unevenness is provided as a light absorbing layer and a conductive layer is as shown in FIG. That is, the metal layer 10 having periodic irregularities is provided on the base material 1, and the recording layer 2 is provided thereon.

The period of the irregularities is preferably equal to or shorter than the wavelength to be absorbed, and for example, the period is preferably 400 nm or less because it is necessary to absorb the entire visible light region in order to color black. The larger the amplitude of the irregularities, the higher the absorption efficiency, but it is preferably one third or more of the cycle.

The metal layer having periodic irregularities can be simply produced by providing various metals on a base material having periodic irregularities. Examples of the base material having periodic unevenness include various thermoplastic resins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polysulfone, acrylic resin, polyvinyl alcohol, urethane resin, phenol resin, urea resin, epoxy resin, and various curable resins. Can be used. In order to prevent the periodic unevenness from being deformed during recording and erasing of the electrostatic recording sheet,
Various curable resins or thermoplastic resins having a heat distortion temperature of 100 ° C. or higher are preferable.

As a method for forming the periodic unevenness on the substrate, (A) a stamper having the periodic unevenness is used to form the entire substrate having the periodic unevenness by an injection molding method, a compression molding method, an embossing method or the like. Forming method, and (B) curing is performed in a state where a heat-curable or photo-curable resin is present between the stamper having the periodic unevenness and the base material, and the periodic uneven shape is transferred and formed on the base material together with the curable resin. There is a method (so-called 2P method).

An example of the construction of the electrostatic recording paper in the case of the method (B) is shown in FIG. That is, the curable resin layer 11 having periodic irregularities is provided on the base material 1, the metal layer 10 having periodic irregularities is provided thereon, and the recording layer 2 is provided thereon.
To provide.

In terms of mass productivity, the method (A), particularly the embossing method using a roll stamper, is excellent, but in these methods for thermoplastic resins, the original flat surface is restored by stress relaxation. Therefore, the molding conditions should be selected so that the residual stress is small. On the other hand, since the method (B) is intended for heat-curable or photo-curable resin, the periodic unevenness once formed does not easily deform even if the recording layer is heated. However, the adhesiveness of the curable resin layer having a periodic uneven shape to the substrate is required sufficiently. If not, it can be improved by providing an adhesive layer on the surface of the substrate.

The stamper having periodic unevenness can be formed by a photolithography technique for photoresist. Specifically, interference fringes are recorded by an interference exposure method using two or more light fluxes, and the interference fringes are developed to obtain a developed photoresist having periodic unevenness. The period of the interference fringes is determined by the incident angle of each light beam on the photoresist and the crossing angle between the light beams, but the depth and shape of the unevenness can be changed by the exposure amount and the developing conditions.

When unevenness is formed by interference fringes, it is preferable that the lattice vectors in which the directions of the lattice vectors do not match be folded in order to reduce the dependence of light absorption on the polarized light. In brief, the two-beam interference may be performed by rotating the photoresist 180 degrees in the photoresist surface and exposing again. It is not necessary to dare to interfere with three or more light beams in which the vector of the incident light does not exist in the same plane.

A metal stamper having periodic irregularities is formed by depositing metal such as chromium on the surface of the developed photoresist to impart conductivity, electroforming nickel or the like, and then removing the remaining photoresist. Can be obtained.

A plastic stamper can be obtained by replicating the periodic irregularities with a curable resin instead of electroforming metal, but these are not suitable for the method (A) because they do not have sufficient heat resistance. Used for the method of (B). However, by using a silicone-based or fluorine-based resin as the curable resin, it is possible to obtain a stamper that can be easily peeled from the curable resin in the method (B).

The metal to be used is not particularly limited, but those whose optical properties are not largely changed by oxidation etc. are preferable, and various metals such as gold, platinum, palladium, silver, nickel, aluminum and chromium can be mentioned.

A metal layer having periodic irregularities can be formed by forming these metals on a substrate having periodic irregularities by a method such as vapor deposition. When a metal layer is formed on the recording layer itself having periodic irregularities to form a reflective layer having periodic irregularities, the recording layer is cross-linked within a range that does not interfere with the property that the light scattering property is changed by heating. It is necessary to introduce a structure so that the periodic unevenness does not change even when recording and erasing with heating.

Further, a heat-resistant layer may be provided on the recording layer so that the recording layer is not deformed or welded to a heating device due to recording or erasing accompanied by heating. As the heat-resistant layer, a curable resin containing a lubricant such as silicone oil or fine particles such as silica, or a thermoplastic resin modified with silicone or fluorine can be used.

The surface roughness of the heat-resistant layer is preferably 1 to 15 μm in terms of center line average roughness. This specified surface roughness keeps the distance between the recording electrode and the surface of the electrostatic recording sheet at a distance at which gas discharge easily occurs, and at the same time,
Since the repulsion between the charged charges is reduced, a more uniform charged state can be obtained, and a recorded image with high contrast can be obtained.

Further, in order to obtain a heat-resistant layer having such a surface roughness, it is preferable that the heat-resistant layer contains particles having a particle size of 3 to 20 μm. The particle material is not particularly limited, but in order to reduce light scattering in the heat resistant layer, it is desirable that the difference in refractive index from other materials such as a curable resin forming the heat resistant layer is small.

Next, two typical methods for producing the electrostatic recording sheet of the present invention when the light absorption layer is formed of a metal layer having periodic unevenness will be described. The first method is (1) an unevenness forming step of transferring the periodic unevenness to the surface of the base material by pressurizing the stamper having the periodic unevenness and the base material in close contact with each other, and (2) the periodic unevenness of the base material. The metal layer forming step of forming a metal film on the surface having (3) and the recording layer forming step of (3) applying a solution containing a liquid crystalline polymer on the metal layer and drying the same are performed.

When the heat-resistant layer is provided on the recording layer,
(4) A heat-resistant layer forming step of applying a solution of a material forming the heat-resistant layer on the recording layer and drying (further curing depending on the case) may be added.

When the substrate is composed of a thermosetting resin, it can be cured by heating in the pressing step, and the transferred unevenness can be prevented from flattening. When the base material is made of a photo-curable resin, it is possible to prevent flattening similarly by performing light irradiation in the pressing step.

When the base material is a thermoplastic resin, the unevenness can be transferred by heating to a proper temperature in the pressing step. When the heat distortion temperature of the resin is close to the heating temperature for recording and erasing, the unevenness is likely to be flattened, but the mass productivity is the highest.

The application of the solution of the polymer composition of (3) and (4) can be performed by using various ordinary coating methods such as blade coating and gravure coating.

Further, in the drying, by changing the conditions such as the drying temperature and the drying air amount, it is possible to select the state of the electrostatic recording sheet immediately after the production, that is, whether it is the whole transparent or colored state or the white state. can do.

The second method is as follows: (1) The stamper having the periodic unevenness and the base material are brought into close contact with each other in the state where the photocurable resin is present, light irradiation is performed to cause photopolymerization, and then the stamper is peeled off. A step of transferring the periodic unevenness to the surface of the base material by adhering a photo-curable resin layer having the periodic unevenness to the surface of the base material, and (2) making a metal on the surface of the base material having the periodic unevenness. The above three steps of the metal layer forming step for filming, (3) the recording layer forming step of applying a solution containing a liquid crystalline polymer on the metal layer and drying the solution are performed.

A heat-resistant layer forming step may be added as in the first method. (2) and (3) are the same as the first,
Since the amount of the photo-curable resin that must be photo-cured in the unevenness forming step (1) is small, there is an advantage that the time required for curing can be shortened.

The above-mentioned two methods are manufacturing methods relating to the electrostatic recording sheet of the present invention in which the light absorbing layer is formed of a metal layer having periodic unevenness, and the unevenness process of (1) and the unevenness process of (2) By substituting the light absorbing layer forming step of applying a solution containing a light absorbing material on a base material in the light absorbing layer forming step of the present invention, the light absorbing layer of the light absorbing material of the present invention and the liquid crystalline polymer are included. An electrostatic recording sheet having a recording layer can be manufactured.

The alignment film may be the same as the alignment film used in a general liquid crystal element. That is, it is an oblique vapor deposition film of an inorganic compound or a film obtained by rubbing a polymer compound film. As the polymer compound that can be used as the alignment film, various compounds such as polyimide, polyamide, polyester, polyvinyl alcohol, or fluororesin such as polyvinylidene fluoride can be used.

The rubbing treatment is a treatment in which the film of the polymer compound is rubbed in a certain direction with a cloth or the like. Although the effect of the alignment film thus prepared on the alignment of the liquid crystal forming compound has not been completely clarified, the surface of the polymer compound film is aligned due to shear stress due to the rubbing treatment. It is believed that the orientation of the liquid crystal forming compound is affected.

In the case of a structure having no conductive layer or light absorbing layer between the recording layer and the base material, the same effect can be obtained if the base material itself is a stretched film composed of an oriented polymer compound. Can be obtained.

Next, the electrostatic recording method of the present invention will be described. FIGS. 10 to 11 show recording principle diagrams in which heating is performed before or after charging. 10 to 11, 12 is an electrostatic recording sheet, 13 is a heating roller, 14 is a recording electrode (stylus), 15 is a counter electrode, and 16 is a high-voltage power supply. Before or after charging, the electrostatic recording sheet 12 contacts the counter electrode 15 with the recording layer side facing the recording electrode 14 between the recording electrode and the counter electrode 15, and has a gap of several μm from the recording electrode 14. Have and pass. At this time, if a voltage higher than a certain value is applied between the recording electrode 14 and the counter electrode 15, the recording electrode 14
Discharge occurs, and the surface of the electrostatic recording sheet 12 on the recording layer side is charged.

In this state, if the temperature of the recording layer reaches or exceeds the temperature for forming the liquid crystal layer, the recording layer is uniformly aligned and the domain of the liquid crystal is expanded, so that the light corresponding to the charged portion is not scattered. A part is formed.

After that, it is fixed by cooling and cooling to below the glass transition temperature. The recording electrode is needle-shaped, and a large number of needles can be arranged to form a multi-needle electrode head.

The counter electrode does not necessarily have to be on the opposite side of the electrostatic recording sheet from the recording electrode. That is, FIG.
If the cross-sectional area of the counter electrode is sufficiently larger than that of the recording electrode as in 2, the conductive layer can be set to a potential close to that of the counter electrode without the counter electrode contacting the conductive layer. From this, discharge to the conductive layer becomes possible, and recording can be performed. FIG. 13 shows an example of a recording method when the electrostatic recording head as shown in FIG. 12 is used. 12 to 1
3, reference numeral 1 is a substrate, 2 is a recording layer, 3 is a conductive layer, and 12
Is an electrostatic recording sheet, 13 is a heating roller, 14 is a recording electrode, 16 and 16 'are high-voltage power supplies, 17 is an electrostatic recording head,
Reference numeral 18 is a counter electrode, and 19 is a platen for ensuring contact between the electrostatic recording head and the electrostatic recording sheet.

Further, a circuit diagram which can be used in the recording method of FIG. 13 will be described with reference to an equivalent circuit diagram of FIG.
VR is the voltage applied to the recording electrode, VC is the voltage applied to the counter electrode, C1 is the capacitance of the gap between the recording electrode and the recording layer, C2 is the capacitance of the recording layer below the recording electrode, and C3 is C4 is the capacitance between the counter electrode and the conductive layer, C4 is the capacitance between the heating roller and the conductive layer, R1 is the resistance of the conductive layer between the recording electrode and the counter electrode, and R2 is the electrode under the heating roller below the counter electrode. Resistance.

If the cross-sectional area of the counter electrode is sufficiently larger than that of the recording electrode as described above, the relationship of 1 <C2 << C3 is established and the applied voltage VR + VC is C1 to C.
As a result of capacity division by 3, almost all the voltage is applied to C1 and gas discharge occurs.

Specific examples will be described below. Example 1 Poly (5- (4-4′-cyanobiphenoxy) pentylmethacrylate) which is a liquid crystalline polymer) (Poly
30 parts by weight of (5- (4-4'-cyanobiphenoxy) penthylmethacrylate)) was dissolved in 70 parts by weight of dichloroethane to prepare a liquid crystalline polymer solution 1.

Carbon black: butyral resin (Sekisui Chemical Co., Ltd. S-REC BX-1) on a 100 μm thick polyethylene terephthalate (PET) film: polyfunctional isocyanate solution (Nippon Polyurethane Co., Ltd. Coronate L) = 7: 2.5: 0.5 was dispersed and mixed in a mixed solvent of toluene: methyl ethyl ketone = 2: 1, and the dissolved coating material was applied by a gravure coater and dried to provide a conductive layer / light absorbing layer of about 2 μm. Then, it was put in a constant temperature oven at 70 ° C. for 24 hours to accelerate the curing reaction.

A solution of the above-mentioned liquid crystalline polymer was applied onto the light absorbing layer by a gravure coater and dried to form a recording layer of about 10 μm, and electrostatic recording sheet A was obtained. (Example 2) A 2-propanol solution of a photocurable resin (Showa Polymer Co., Ltd. Lipoxy SP-1509) was applied onto the recording layer of the electrostatic recording sheet 1 prepared in the same manner as in Example 1 and dried. After forming a heat-resistant layer having a thickness of about 0.5 μm, a mercury lamp was irradiated to cure the heat-resistant layer to obtain an electrostatic recording sheet B.

(Example 3) 7 parts by weight of a photo-curable resin (Showa Polymer Co., Ltd. Lipoxy SP-1509) and a particle size of about 1 μm were formed on the recording layer of the electrostatic recording sheet 1 prepared in the same manner as in Example 1. 1
A 2-propanol solution containing 3 parts by weight of 0 .mu.m silica particles was applied and dried to form a heat resistant layer of about 2.3 g / m.sup.2, which was then irradiated with a mercury lamp to cure it, and electrostatic recording sheet C Got

(Example 4) 2- [4- (4-
A liquid crystalline polymer solution 2 was prepared by dissolving 30 parts by weight of cyanophenylcarbonyloxy) phenoxy) ethylacrylate polymer in 70 parts by weight of dichloroethane.

Carbon black: Butyral resin (Sekisui Chemical Co., Ltd. S-REC BX-1): Polyfunctional isocyanate solution (Nippon Polyurethane Co., Ltd. Coronate L) = 7: 2.5: 0.5 on a PET film having a thickness of 100 μm. Was dispersed in a mixed solvent of toluene: methyl ethyl ketone = 2: 1, and the dissolved coating material was applied by a gravure coater and dried to form a conductive layer of about 4 μm. Then, it was put in a constant temperature oven at 70 ° C. for 24 hours to accelerate the curing reaction.

WO ₃ is vapor-deposited on this, and a thickness of about 20 nm (2
00 angstrom) was attached to form a high refractive index layer.
Further, a solution of the liquid crystalline polymer 2 was applied onto this and dried to form a recording layer of 10 μm. This was designated as electrostatic recording sheet D.

(Example 5) Carbon black-containing 10
A PET film having a thickness of 0 μm was used as a light absorbing layer and a base material, and ZnO was used as a transparent conductive layer by a sputtering method.

Further, a liquid crystal polymer solution 1 was applied on this and dried to form a recording layer having a thickness of 10 μm. This was designated as an electrostatic recording sheet E. Example 6 ITO was vapor-deposited on a PET film having a thickness of 75 μm to form a transparent conductive layer, on which a polyvinyl alcohol aqueous solution was applied with a wire bar and dried. Further, the surface of the polyvinyl alcohol film was rubbed with a rayon cloth to form an alignment film.

Liquid crystal polymer solution 1 was applied onto this alignment film and dried to form a recording layer having a thickness of 10 μm. Furthermore, a photo-curable resin (Showa Polymer Co., Ltd. Lipoxy SP-15)
09) A 2-propanol solution containing 8 parts by weight and 2 parts by weight of benzoguanamine particles having a particle size of about 10 μm was applied and dried to form a heat-resistant layer of about 2.3 g / m ² , and then a mercury lamp was irradiated. This was cured to obtain an electrostatic recording sheet F.

(Embodiment 7) A glass substrate having a diameter of 40 cm was coated with a photoresist in a thickness of 300 nm and dried well, and then a 488 nm argon ion laser beam split into two light beams was collimated on the surface coated with the photoresist. Then, interference exposure was performed by making the incident angles 54.4 degrees and -54.4 degrees, respectively. Further, the glass substrate with the photoresist was rotated 90 degrees in the plane, and then interference exposure was performed again, and then development was performed.

After depositing chromium on the developed photoresist surface, plating was performed in a nickel bath using the chromium layer as an electrode to obtain a nickel plate having a thickness of 500 μm.
The nickel plate was peeled from the glass substrate, and the photoresist remaining on the peeled surface of the nickel plate was removed to obtain a mother stamper. Similarly, nickel plating is performed using this mother stamper as an electrode, and a daughter stamper (stamper 1)
Got Each surface has a period of about 300 nm and a depth of about 150.
Concavities and convexities intersecting nm were formed.

The stamper 1 is cut into a rectangular shape and has a diameter of 10c.
It was wound around a steel cylinder of m to obtain an embossing roll. Attach this to a roll-type press machine and
A m-thick polycarbonate film was supplied, and the film on the supply side was continuously embossed while being heated with a hot-air dryer to obtain a substrate 1 having periodic irregularities.

For the base material 1 having periodic unevenness, aluminum was formed into a metal layer with a thickness of 7 nm (70 angstrom) using a continuous sputtering apparatus to form a metal layer.
Further, the liquid crystal polymer solution 1 is applied to the base material 1 using a continuous microgravure coater and dried to about 1
An electrostatic recording sheet G was obtained by providing a recording layer of 0 μm.

(Embodiment 8) Recording and erasing of electrostatic recording sheet Electrostatic recording sheets A, B, C, D obtained by the above method
E was white and opaque. These were installed in a recording device in which a heating roller having a surface of a steel roller with a heater coated with a silicone resin, a 6-dot / mm multi-needle electrode head, and a high voltage power source of 1 kV were combined. The positive electrode of the high-voltage power supply was connected to the conductive layer of the electrostatic recording sheet, and the multi-needle electrode head side recorded a stripe at a 1 cm interval with a line period of 500 microseconds as a cathode. The recording layer of each printed portion became transparent and turned black.

Example 9 Contrast Measurement The reflection optical densities of the recorded and unrecorded portions of the samples of the electrostatic recording sheets A to G recorded in Example 8 at the light wavelength of 550 nm were measured with an integrating sphere type spectrophotometer. It was measured. For the electrostatic recording sheet F, a black paper was placed on the back surface of the base material for measurement. The results are shown in Table 1.

[0117]

[Table 1]

(Embodiment 10) Erasure of recording and new recording In the same manner as in Embodiment 8, the electrode needle for applying the voltage of the head is replaced with the case of Embodiment 8 to obtain the sample recorded in Embodiment 8. Recorded.

The recording layer in the portion recorded in Example 8 was erased due to the light scattering state, and the newly recorded portion was in the same colored state as in Example 8. According to this method, it was found that the non-recorded portion can be erased at the same time as the recording without separately erasing the recording.

[0120]

As described above, according to the present invention, since the recording layer contains a liquid crystalline polymer for performing reversible electrostatic recording, electrostatic recording with high recording sensitivity and thermally reversible recording and erasing is possible. A recording sheet and an electrostatic recording method capable of high-speed recording using the recording sheet can be provided. Further, it is possible to provide an electrostatic recording sheet having high contrast and capable of reversible recording and erasing.

Further, according to the electrostatic recording method of the present invention, high speed recording can be performed by using the electrostatic recording sheet which can reversibly erase and erase the recording.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electrostatic recording sheet according to an embodiment of the present invention, in which a recording layer 2 is formed on a base material 1.

FIG. 2 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which a conductive layer 3 is provided on a base material 1 and a recording layer 2 is formed thereon.

FIG. 3 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which a recording layer 2 is formed on a base material 4 which also serves as a conductive layer.
The example which formed.

FIG. 4 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which a conductive layer 3 is provided on a substrate 1, a recording layer 2 is provided thereon, and a heat-resistant layer is provided thereon. The example which formed 5.

FIG. 5 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which a light absorbing layer 7 is provided on a base material 1, a transparent conductive layer is provided on the light absorbing layer 7, and recording is performed thereon. The example which formed the layer 2.

FIG. 6 is a schematic cross-sectional view of an electrostatic recording sheet of another embodiment of the present invention, in which a conductive layer 3 is provided on a base material 1, a high refractive index layer 9 is provided thereon, and a conductive layer 3 is provided on the conductive layer 3. An example of forming the recording layer 2.

FIG. 7 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which an alignment film 8 is provided on a substrate 1 and a recording layer 2 is formed thereon.

FIG. 8 is a schematic cross-sectional view of an electrostatic recording sheet of another example of the present invention, in which a metal layer 10 having periodic unevenness is provided on a base material 1, and a recording layer 2 is formed thereon. Example.

FIG. 9 is a schematic cross-sectional view of an electrostatic recording sheet according to another embodiment of the present invention, in which a curable resin layer 11 having periodic unevenness is provided on a base material 1, and the periodic unevenness is formed thereon. The example which provided the metal layer 10 which has, and formed the recording layer 2 on it.

FIG. 10 is a principle diagram of an electrostatic recording method according to an embodiment of the present invention.

FIG. 11 is a principle diagram of an electrostatic recording method according to another embodiment of the present invention.

FIG. 12 shows another embodiment of the present invention and is a schematic cross-sectional view of an electrostatic recording head in the case where the cross-sectional area of the counter electrode has a sufficiently larger area than the cross-sectional area of the recording electrode.

FIG. 13 is a schematic view showing an example of a recording method when the electrostatic recording head shown in FIG. 12 is used.

FIG. 14 is a circuit diagram that can be used in the recording method of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Recording layer 3 Conductive layer 4 Base material also serving as a conductive layer 5 Heat-resistant layer 6 Transparent conductive layer 7 Light absorbing layer 8 Alignment film 9 High refractive index layer 10 Metal layer having periodic irregularities 11 Curing having periodic irregularities Resin layer 12 Electrostatic recording sheet 13 Heating roller 14 Recording electrode (stylus) 15 Counter electrode 16,16 'High voltage power supply 17 Electrostatic recording head 18 Counter electrode 19 Platen VR Voltage applied to recording electrode VC Applied to counter electrode Voltage C1 Capacitance of air gap between recording electrode and recording layer C2 Capacitance of recording layer below recording electrode C3 Capacitance between counter electrode and conductive layer C4 Capacitance between heating roller and conductive layer R1 Below recording electrode Resistance of the conductive layer between the counter electrode and under the counter electrode R2 Resistance of the electrode under the heating roller under the counter electrode

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[Procedure amendment]

[Submission date] May 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Further, in the above constitution, it is preferable that the heat resistant layer is selected from a curable resin and a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher. Further, in the above configuration,
Having a substrate or a conductive layer, an alignment layer between the recording layer
Is preferred.

Front page continuation (72) Inventor Keizo Nakajima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. An electrostatic recording sheet having a recording layer on a substrate directly or through another layer, wherein the recording layer contains a liquid crystalline polymer for performing reversible electrostatic recording. Electrostatic recording sheet. 2. The electrostatic recording sheet according to claim 1, wherein the liquid crystalline polymer is a thermotropic liquid crystal polymer. 3. The electrostatic recording sheet according to claim 1, further comprising a conductive layer between the base material and the recording layer. 4. The electrostatic recording sheet according to claim 3, wherein the conductive layer is colored. 5. The electrostatic recording sheet according to claim 3, wherein the conductive layer is made of a transparent conductive material. 6. The resistance value of the conductive layer is 10 ⁶ to 10 ⁹ Ω / □.
The electrostatic recording sheet according to claim 3, wherein 7. The electrostatic recording sheet according to claim 1, further comprising a heat-resistant layer on the recording layer. 8. The electrostatic recording sheet according to claim 7, wherein the heat-resistant layer has a center line surface roughness of 1 to 15 μm. 9. The electrostatic recording sheet according to claim 7, wherein the heat-resistant layer contains particles having a particle size of 3 to 20 μm. 10. The electrostatic recording sheet according to claim 7, wherein the heat resistant layer is selected from a curable resin and a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher. 11. The electrostatic recording sheet according to claim 1, which has an alignment film between the substrate or the conductive layer and the recording layer. 12. The electrostatic recording sheet according to claim 1, wherein the base material is selected from a curable resin and a thermoplastic resin having a heat distortion temperature of 100 ° C. or higher. 13. A voltage is applied between a stylus installed on the recording layer side of an electrostatic recording sheet having a recording layer containing a liquid crystalline polymer and a counter electrode installed on the other side of the electrostatic recording sheet or a conductive layer of the electrostatic recording sheet. Is applied and discharged to charge the recording layer side of the electrostatic recording sheet, and before or after charging,
An electrostatic recording method characterized in that a liquid crystal polymer constituting a recording layer is heated to a temperature at which it exhibits a liquid crystal phase or higher to expand domains of the liquid crystal phase generated in the recording layer. 14. A domain size is uniformly reduced by heating the liquid crystal polymer to a temperature at which it forms an isotropic phase or higher in an absence of an external electric field and then allowing it to cool.
The electrostatic recording method according to claim 13, wherein the record is erased. 15. The electrostatic recording method according to claim 13, wherein the stylus is a monostylus or a multistylus.