JPH1048604A - Advertizement medium which can be repeatedly used - Google Patents

Abstract

PROBLEM TO BE SOLVED: To write a new advertizement information in a same medium by using characteristics of a smectic liquid crystal so that writing information by either heat or an electric field and erasing information by the other can be repeated. SOLUTION: A transparent electrode 12 and a liquid crystal/polymer composite film (PDLC film) 13 having dispersion of a smectic liquid crystal in a polymer matrix are formed on the surface of a base film 11 such as a polyester film. A transparent electrode 14 may be formed on the surface of the PDLC film 13 or a protective layer 15 may be directly formed. In the obtd. PDLC film, information can be written by either heat or an electric field and information can be erased by the other, and these processes can be repeated. Writing (recording)/erasing visible information in the PDLC film 13 is based on such a principle that transmission and diffusion of light is caused in an oriented state and random orientation state of liquid crystal molecules, respectively, by heat and electric field (heat-electric field mode).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an advertising medium which is suitable for advertisements in vehicles such as trains and buses, advertisement panels in station yards and other places, and which can be used repeatedly.

[0002]

2. Description of the Related Art Conventionally, as a medium for advertisement, a glass or plastic panel on which an image or the like is printed is housed in a case, and an advertisement panel in a station yard or the like in which an image or the like is raised by irradiating a fluorescent lamp or the like from the back. In addition, printed materials for advertisements and the like, which are displayed from the wall surface of a company such as a train or a bus to the ceiling or suspended from the ceiling, are used.

[0003]

The above-mentioned advertisements are usually exchanged for new advertisements on a regular basis, and the work at the time of the exchange is troublesome, and a large amount of used advertisement printed matter is used. The waste is incinerated or regenerated as a disposal, but in any case, it is a great waste of resources and energy, which is not preferable in terms of environmental conservation. Therefore, an object of the present invention is to provide an advertising medium that can repeatedly display necessary information without requiring the above-described incineration and reproduction processing.

[0004]

The above object is achieved by the present invention described below. That is, the present invention comprises a liquid crystal / polymer composite film (hereinafter simply referred to as a PDLC film) in which a smectic liquid crystal is dispersed in a polymer matrix, and the film writes information by either heat or electric field. On the other hand, it is a reusable advertising medium characterized in that information can be repeatedly erased.

[0005] The advertising medium of the present invention is capable of repeatedly writing information in one of heat and electric field and erasing information in the other, due to the characteristics of the smectic liquid crystal. In doing so, it does not require a new recording medium such as paper, erases the information of the removed advertising medium, writes new advertising information on the same medium,
It can be posted again at a predetermined place. Therefore, it is not necessary to prepare a new medium or printing material such as printing paper, printing ink, printing plate or the like as in the prior art, and there is no need to incinerate or recycle used advertising media. Further, the energy required for erasing and writing information is extremely small compared to the energy required for incineration and reproduction.

[0006]

Next, the present invention will be described in more detail with reference to preferred embodiments. FIG. 1 is a diagram schematically illustrating a cross section of an advertising medium of the present invention which can be replaced with a normal size, for example, a B4 size cardboard advertising paper. In the figure, reference numeral 11 denotes a base film such as a polyester film, and a PDL is provided on the surface thereof via an electrode 12.
A C film 13 is formed. The transparent electrode 14 may be formed on the surface of this PDLC film.
The protective layer 15 may be formed directly on the surface of the film 13 without providing the layer. The details of each layer will be described later. Such a PDLC film can write information in one of heat and electric field and erase information in the other, and the writing and erasing can be repeated.

Writing (recording) of visible information on the PDLC film
The principle of / erasing uses light transmission and light scattering in an alignment state and a random alignment state of liquid crystal molecules by heat and an electric field (heat-electric field mode). Therefore, the recorded information is displayed as white turbid light due to light scattering (when dichroic dye is used, colored light due to the dye), and when erasing is performed by transparency through light transmission, printing (writing) is performed. ) Is performed by a heating means such as a thermal head, which can be heated in a spot manner, and the erasing is performed, for example, while heating as necessary.
This can be performed by applying an electric field to the DLC film that is equal to or more than the threshold value of the liquid crystal alignment.

In the PDLC film, the liquid crystal is μs by applying an electric field.
ec. Because it is oriented in the order, high-speed rewriting process can be performed compared to various reversible display devices in the conventional heat-heat mode,
It is suitable as the advertising medium of the present invention. The number of rewrites is sufficient, and the visibility of the displayed image is improved by using a dichroic dye in combination, the memory is excellent in a natural environment, and the displayed image is not unintentionally erased.

The liquid crystal material used in the present invention is a smectic liquid crystal, and any conventionally known smectic liquid crystal can be used. It is preferable that these smectic liquid crystals have a wide temperature range exhibiting a nematic phase. In the present invention, by using a smectic liquid crystal material having a temperature range exhibiting a nematic phase of 1 ° C. or more, P is reduced.
The driving voltage when the DLC film is made transparent can be reduced.

A dichroic dye may be mixed in the smectic liquid crystal at a ratio of, for example, 1 to 10 parts by weight per 100 parts by weight of the smectic liquid crystal for the purpose of improving the contrast ratio and coloring. In this case, the dichroic dye to be contained in the liquid crystal is not particularly limited, and any of an azo type, a perylene type, an anthraquinone type, and the like can be used, and the color tone required for display of an advertising medium can be used. Suitable dichroic dyes are used in combination with liquid crystals, matrix materials, capsule wall materials and the like.

The polymer material forming the polymer matrix for dispersing the liquid crystal or the liquid crystal containing a dichroic dye (hereinafter simply referred to as liquid crystal) is not compatible with the liquid crystal, and is excellent in transparency and film forming ability. Any polymer material can be used. Specifically, an appropriate polymer material, for example, a polyvinyl alcohol resin, a fumarate-based resin, an epoxy resin, a polycarbonate resin, a UV-curable resin of polythiol, or the like is used according to the method of forming the PDLC film.

Further, the liquid crystal may be microencapsulated, and the microencapsulation method is not particularly limited, and a conventionally known method is used. For example, a liquid crystal or a liquid crystal in which a radical-reactive monomer is dissolved in an aqueous medium is mixed with a radical-reactive surfactant, a water-soluble protective colloid, or a radical-reactive protective colloid, or a mixture of two or more of these. By emulsifying and dispersing, dissolving or dispersing the radical initiator in water or liquid crystal, and raising the temperature to the decomposition temperature of the initiator, a capsule wall film surrounding the liquid crystal particles can be produced. As the radical polymerizable monomer to be dissolved in the liquid crystal, one having compatibility with the liquid crystal, such as styrene, vinyl acetate, and (meth) acrylate, can be used. Preferably, a mixture of two or more functional monomers is preferred. As the radical initiator, a water-soluble, oil-soluble or redox-based initiator can be used. It is also possible to initiate polymerization using ionizing radiation such as gamma rays or electron beams.

In the microencapsulated liquid crystal having the above structure, the polymer material used as the wall material is preferably used in a range of 5 to 25 parts by weight per 100 parts by weight of the core material smectic liquid crystal. If the amount of the wall material used is less than the above range, problems such as oozing of liquid crystal cannot be sufficiently solved because the wall is thin. On the other hand, if the amount used exceeds the above range, the thickness of the wall is large, so that when the dichroic dye is used, the amount of the dichroic dye incorporated into the wall increases, and the wall is colored. This is not preferable because the reflection density at the time of application does not become sufficiently low. The thickness of the wall in the encapsulated state varies depending on the liquid crystal material, polymer material, encapsulation method, and the like used, but is generally about 10 to 100 nm.

As a method of dispersing the liquid crystal in the polymer matrix, any of conventionally known methods such as a phase separation method and an emulsion method can be used. The emulsion method will be briefly described below as a typical example. However, the present invention is not limited to the emulsion method. In the emulsion method, the liquid crystal is emulsified and dispersed in a medium mainly composed of water containing a surfactant or a protective colloid as necessary, and polyvinyl alcohol, gelatin, an acrylic acid copolymer, a water-soluble alkyd resin A method of applying a water-soluble or water-dispersible polymer material such as, for example, on a suitable substrate and drying to form a film having a suitable thickness. PDLC with liquid crystal uniformly dispersed in it
A film is formed.

As a method of emulsifying and dispersing the liquid crystal in an aqueous solution or aqueous dispersion of the molecular matrix, a mixing method using various stirring devices such as an ultrasonic dispersion method and a mechanical dispersion method, and a film emulsification method [Tadao Nakajima, Masataka Shimizu, PHARMTEC
H JAPAN Vol. 4, No. 10, No. (1988)] is effective. The particle size of the obtained liquid crystal emulsion particles has a diameter of 1 in the volume distribution so that the liquid crystal molecules are easily oriented in the matrix or the capsule.
It is desirable that the proportion of the liquid crystal particles having a size of μm or less be 10% or less in all the particles. For example, when an O / W emulsion of a liquid crystal is obtained by a porous glass (MPG) film emulsification system, the volume distribution of the liquid crystal to be emulsified and dispersed is adjusted by setting the average pore diameter of the MPG to be used to 0.3 μm (diameter) or more. Can be in the above range. Also, using a mechanical dispersion method, for example, the condition of the mechanical dispersion is set to a rotational speed of 1,000 r.
A liquid crystal emulsion containing a liquid crystal having a volume distribution within the above range can be obtained by setting it to pm and 1 minute or more.

Using the thus obtained liquid crystal dispersion, PD
As a method of forming an LC film, a method of applying and drying the liquid crystal dispersion on a substrate is preferable. Examples of the coating method include an electrodeposition method, a screen coating, a blade coating, a knife coating, a slide coating, an intrusion coating, and a fountain coating. The P obtained in this way
The thickness of the DLC film is preferably about 3 to 23 μm. If the film thickness is too small, light scattering (turbidity) at the time of heating becomes insufficient, and if the film thickness is too large, a large driving voltage is required for the alignment of the liquid crystal.

The amount of the liquid crystal used is usually such that the mixing ratio (weight ratio) of the polymer matrix forming material / liquid crystal is 65/3.
The range of 5-35 / 65 is desirable. If the amount of liquid crystal used is too small, not only is the transparency of light when a voltage is applied insufficient, but it is also insufficient in that a large voltage is required to make the film transparent. If the amount of the liquid crystal used is too large, not only is light scattering (turbidity) at the time of heating insufficient, but also the strength of the film is undesirably reduced.

As described above, the advertising medium of the present invention comprises at least a PDLC film and electrodes for applying an electric field to the film. This electrode may sandwich both surfaces of the PDLC film, or may be provided only on the back surface. The application of the voltage when the electrode is provided only on the back surface is performed by, for example, corona discharge. When information is written using a thermal head or the like, P
It is preferable to form a protective layer on the surface of the DLC film.

The conductive substrate on which the PDLC film is formed by coating is a substrate generally used for a conventionally known liquid crystal display device. For example, a transparent conductive substrate such as ITO, SnO ₂ or ZnO is used. An electrode substrate in which a material is attached to a transparent substrate such as a polymer film such as PET (polyethylene terephthalate). On the other hand, in the case of an opaque conductive substrate,
Since the electrode is also required to function as a reflection plate, for example, a substrate provided with an aluminum reflection electrode is preferable. The substrate itself may be a polymer film or other. Further, a transparent conductive material such as ITO, SnO ₂ or ZnO may be attached to a reflection plate such as a white PET film. Further, a reflection plate formed by forming a reflection layer made of Al ₂ O ₃ , TiO ₂ , ZnO or the like on a polymer film may be bonded to the surface of the transparent conductive substrate opposite to the PDLC film.

P formed on a transparent or reflective conductive substrate
When the DLC film is sandwiched between the conductive substrate and the conductive substrate, the conductive substrate is generally used for a conventionally known liquid crystal display device. For example, a transparent substrate such as ITO, SnO ₂ , and ZnO is used. An electrode substrate in which a conductive material is adhered to a transparent substrate such as a polymer film such as PET is used.

P formed on a transparent or reflective conductive substrate
When a protective layer is formed on the surface of the DLC film, the polymer material for forming the protective layer has excellent adhesiveness to the PDLC film and can form a transparent film, and its refractive index is PDLC. Any polymer material can be used as long as the difference is 0.05 or less as compared with the refractive index of the matrix forming polymer material of the film. For example, when polyvinyl alcohol is used as the matrix-forming polymer material, a preferable protective layer-forming polymer material is
A crosslinked polymer composed of a polyfunctional monomer such as trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and pentaerythritol tetra (meth) acrylate is exemplified. These monomers can be used alone or as a mixture of two or more kinds, and further mixed with other monomers.

It is desirable that the protective layer formed on the surface of the PDLC film has a smooth surface and that the difference between the refractive index of the protective layer and the refractive index of the polymer matrix is 0.05 or less. If the difference exceeds 0.05, the difference between the refractive index of the liquid crystal and the refractive index of the protective layer when a voltage is applied increases,
Light scattering is increased and the contrast is reduced. More preferably, it is 0.03 or less. Further, the average roughness (Ra) of the obtained protective layer is preferably less than 0.1 μm. If the average roughness is 0.1 μm or more, light is scattered on the surface of the protective layer, and the contrast is reduced.

As a method for forming the protective layer, for example, PD
PDL as a solution in which the polymer material for forming the protective layer is dissolved in a solvent that does not dissolve the LC film, or as an emulsion of an appropriate medium
After applying the above-mentioned monomer which forms a film by polymerization in the same manner as the formation of the C film onto the PDLC film surface, the monomer is converted into a polymer by an appropriate means (heating, electron beam irradiation, etc.). A protective layer or a monomer layer is separately formed on the release sheet surface by the above method, and the protective layer or the monomer layer is transferred and laminated on the PDLC film surface (in the case of a monomer layer, Polymerization and curing at the time of transfer or after transfer). The thickness of the formed protective layer is preferably in the range of 1 to 5 μm.

The advertisement-like medium of the present invention as described above can be used in the same state as cardboard used for ordinary advertisement. For example, in FIG. 1, the PDLC layer is heated to a predetermined temperature as needed, and in this state, the surface of the protective layer 15 is charged by a corona discharger or the like, and a predetermined voltage is applied between the protective layer and the electrode 12. When the voltage is applied, the liquid crystal in the PDLC layer is oriented, the PDLC layer becomes transparent, and the transparent state is maintained by cooling and charge removal. In this state, the PDLC layer is heated in an image shape by a thermal head, a hot pen, or the like, whereby the alignment state of the liquid crystal of the PDLC layer is eliminated, and the portion to which heat is applied becomes a light scattering state, and information is recorded and recorded. The information is not erased unless the PDLC layer is reheated. The information to be written can be improved in contrast ratio by using a dichroic dye, and the liquid crystal layer is formed of a YMC matrix by using a liquid crystal to which a dichroic dye of three primary colors of yellow, magenta and cyan is added. Thus, various color displays and full-color image displays are also possible.

The advertising medium of the present invention on which the information is recorded as described above is displayed at a predetermined position in a train or the like, or used by hanging it. When exchanging these advertisements, it is possible to remove the advertisement, repeat the above-mentioned operation, write another information, post it again at a predetermined position, or hang it. This writing and erasing can be repeated almost infinitely many times.

FIG. 2 is a schematic view showing a hanging advertisement board which is another example of the advertisement medium of the present invention. In the figure, reference numeral 21 denotes an advertisement medium winding device, which is an advertisement medium 22 of the present invention.
Is wound around the winding device 21 and can be freely pulled out. Below the winding device 21, an erasing unit 24 incorporating a heating device and a corona charger and a writing unit 23 having a thermal head such as a small printer are provided. Now, it is assumed that information in a predetermined state is recorded in the advertisement medium and the medium is being advertised. When the content of the advertisement is changed, the erasing unit 24 is operated to wind the advertising medium 22 into the winding device 21 and erase the displayed information. Next, while operating the writing unit 23, the advertising medium 2 is driven at a predetermined speed.
By pulling out 2, the advertisement medium 22 on which other information is displayed is suspended. The above operation can be repeated semi-permanently.

FIG. 3 shows another example. The display device of FIG. 3 is an example in which a writing unit 33 is provided near the entrance of one winding unit 31 and an erasing unit 34 is provided near the entrance of the other winding unit 31 ′. Writing unit 3 near the entrance of the part 31 or 31 '
3 and the erase unit 34 may be provided.
As described above, the mounting positions of the units 33 and 34 are not particularly limited.

In FIG. 3, in order to write information on the advertisement medium 32, the take-up section 31 or 31 'roller (not shown) is rotated by a drive motor (not shown) to thereby move the advertisement medium 32 to the take-up section. When the information has already been written on the advertising medium 32, the erasing unit 34 is operated to erase the written information and perform the winding. In order to newly write information, printing is performed on the right half of the advertising medium 32 by synchronizing the rotation of the rollers (not shown) of the winding units 31 and 31 ′ with the operation of the writing unit. Next, the rotation of the rollers (not shown) of the winding units 31 and 31 ′ is synchronized with the operation of the writing unit 33 to print on the left half of the advertising medium 32. In the writing unit 33, for example,
A thermal head is installed, and desired information is recorded and displayed on the advertisement medium 32 by the heating. FIG.
FIG. 1 shows a schematic configuration diagram of an example of a writing unit and an erasing unit when writing and erasing an advertisement medium made of a PDLC film. In FIG. 4, the writing unit 43 and the erasing unit 44 are shown integrally, but these means that they can be separated into units indicated by broken lines.

The writing unit 43 is provided with a thermal head 46 facing the platen roller 45.
The thermal head 45 receives a predetermined signal and receives the advertisement medium 4.
2 is written with desired information. The erasing unit 44
A power supply 48 for supplying a predetermined voltage to the charger 47 and a platen roller 45 for reliably bringing the processing surface into contact with the ground roller 49 are disposed opposite to the ground roller 49. The advertisement medium 42 erases recorded information by applying a voltage while heating as necessary, and records information by heating with a thermal head 46. The charger 48 is a corona charger having a tungsten wire connected to the power supply 48 inside. Further, the ground roller 49 and the power supply 42 are grounded, and a potential difference is generated between the surface of the advertising medium 42 charged by the charger 47 and the contact surface with the ground roller 49. An electric field is applied to the.

As the charger 47, a conventionally known corotron charger, scorotron charger and the like can be used. As the ground roller 49, a plastic or rubber roller or the like containing a conductive material such as metal or conductive carbon black can be used. Particularly preferred is a roller made of an elastic material such as rubber. Both the electric field applying means 47 (charging device) and the thermal head 46 can be used for writing and erasing information. However, by using the electric field applying means for erasing, the display is not erased at a temperature under a natural environment, and the display reliability is reduced. This makes it possible to provide an excellent display.

The electric field applying means of the erasing unit 44 is not limited to the above method.
Any of electric field applying means such as a charging method described in JP-A No. 03249 and Japanese Patent Application No. 6-302701 and an electrode method described in Japanese Patent Application No. 6-30270 can be used. As the writing unit 43, a thermal head used for a thermal printer is used. A heating means using a laser can be used instead of the thermal head.

As the advertising medium in the present invention, for example, a roll-up display may be placed on a wall such as an advertising board or a passageway of a station, which is posted from a wall or a ceiling of a company such as a train or a bus or suspended from the ceiling. An advertising board or the like which is installed so as to expose only the advertising medium portion may be used.

[0033]

Next, the present invention will be described more specifically with reference to examples. Example 1 Smectic liquid crystal: SCE-9 (manufactured by Merck Limited, temperature range showing a nematic phase: 91.0 to 11)
(5.0 ° C.), 100 parts of dichroic dye: S-428 (black color / transparent dichroism) (manufactured by Mitsui Toatsu Chemicals) was added, and the mixture was stirred at 120 ° C. for 30 minutes. To this mixed solution, polyvinyl alcohol: EG-05 (manufactured by Nippon Synthetic Chemical Industry,
(Polymerization degree: 500, saponification degree: 86.5 to 89.0) 252.8 parts of a 5% by weight aqueous solution was added, and a porous glass membrane tube (manufactured by Ise Chemical Industry) having a pore diameter of 1.10 μm (diameter) was used. It was dispersed by a membrane emulsification method.

The particle size distribution of the liquid crystal was measured using Microtrack MK.
-IISPA particle size distribution analyzer (LEED & NORTHRUUP
As a result, the average particle diameter (diameter) in the volume distribution was 7.7 μm, and the ratio of particles having a diameter of 1 μm or less was 1.5%. PVA: KH-20 (manufactured by Nippon Synthetic Chemical Industry, degree of polymerization: 2,000, degree of saponification: 78.5 to 81.5) was added to this dispersion as a thickener,
CE-9 / (KP-06 + KH-20) = 50/50
(W / w) and stirred. Using this dispersion, I-deposited ITO deposited white PET film (Toray)
It was applied on the TO surface using a doctor blade and dried to form a film. The thickness of the obtained PDLC film was 10.3.
μm. The refractive index of polyvinyl alcohol (EG-05 and KH-20) forming the matrix of the PDLC film was 1.51. To measure the refractive index, use a refractometer:
The measurement was performed using DVA-36L (manufactured by Mizojiri Optical Industry).

Trimethylolpropane triacrylate: EXG-40-8 (manufactured by Dainichi Seika) was applied to a release film made of PET: MC-19 (manufactured by Reiko) using a doctor blade, and dried. A film was formed to a thickness of 8 μm. After laminating the film surface with the PDLC film surface facing each other, irradiating it with 4 Mrad electron beam to polymerize and dry the acrylate, and then peeling off the release film, the film was smooth (average roughness: Ra). = 0.01 μm). The refractive index of the cured polymer film of trimethylolpropane triacrylate having the same film thickness was 1.50 (the refractive index was measured using the refractometer described above).

The advertising medium made of the PDLC film thus obtained was cut into A4 size, and used as an advertising medium of the present invention for displaying from a wall surface to a ceiling in a room such as a railway car or a bus. For writing the information on the advertising medium, a thermal head (head resolution: 6 dots / m) used in a thermal printer as a writing unit
m and a heating amount of 0.8 mJ / dot). A corona charger was used as the erasing unit. A thermal head was connected to the microcomputer, and the character information input to the microcomputer was output to the above-mentioned advertising medium. As a result, clear black characters were displayed. This advertising medium was fitted in a fitting type bulletin board in a train room and used as an advertisement. Next, the entire surface of the advertising medium is
When an electric field was applied by a corona charger while heating to ° C., all surfaces became transparent and the displayed image was completely erased. This erased advertising medium could be written and erased any number of times.

Example 2 The PDLC film obtained in Example 1 was incorporated into a hanging display device shown in FIG. 2 and used as an advertising medium for hanging inside a bus room. To write the information on the advertising medium, a thermal head (head resolution: 6 dot / mm,
A heating amount of 0.8 mJ / dot) was used. A corona charger was used as the erasing unit. A thermal head was connected to the microcomputer, and the character information input to the microcomputer was output to the above-mentioned advertising medium. As a result, clear black characters were displayed. This advertising medium was used as an advertisement by hanging it on a ceiling in a bus room. next,
When an electric field was applied by a corona charger while heating the entire surface of the advertising medium to about 75 to 95 ° C., all surfaces became transparent and the displayed image was completely erased. This erased advertising medium could be written and erased any number of times.

Example 3 The PDLC film obtained in Example 1 was incorporated into a roll-in type display device shown in FIG. 3 and used as an advertising medium of the present invention. Thermal head used in a thermal printer as a writing unit (head resolution: 6 dots / mm,
A heating amount of 0.8 mJ / dot) was used. A corona charger was used as the erasing unit. A thermal head was connected to the microcomputer, and the character information input to the microcomputer was output to the above-mentioned advertising medium. As a result, clear black characters were displayed. Next, when an electric field was applied by a corona charger while the entire surface of the advertising medium was heated to about 75 to 95 ° C., all surfaces became transparent and the displayed image was completely erased. This erased advertising medium could be written and erased any number of times.

[0039]

According to the present invention, as described above, it is possible to repeatedly write information in one of heat and electric field and erase information in the other due to the characteristics of the smectic liquid crystal. When exchanging advertisements, do not need a new recording medium such as paper, erase information on the removed advertising medium, write new advertising information on the same medium, and post it again at a predetermined place Can be. Therefore, it is not necessary to prepare a new medium or printing material such as printing paper, printing ink, printing plate or the like as in the prior art, and there is no need to incinerate or recycle used advertising media. Further, the energy required for erasing and writing information is extremely small compared to the energy required for incineration and reproduction.

[0040]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an advertising medium of the present invention.

FIG. 2 is a schematic view showing an example of an advertising medium of the present invention.

FIG. 3 is a schematic diagram showing an example of an advertisement medium of the present invention.

FIG. 4 is a writing unit for displaying and erasing information;
FIG. 3 is a schematic diagram illustrating an example of an erasing unit.

[Explanation of symbols]

 11: Base film 12: Electrode 13: PDLC film 14: Transparent electrode 15: Protective layer 21: Winding device 22, 32, 42: Advertising medium 23, 33, 43: Writing unit 24, 34, 44: Erasing unit 31, 31 ': Winding unit 45: Platen roller 46: Thermal head 47: Charger 48: Power supply 49: Ground roller

Claims (3)

[Claims] 1. A liquid crystal / polymer composite film comprising a smectic liquid crystal dispersed in a polymer matrix, wherein the film comprises:
A reusable advertising medium characterized in that writing of information in one of heat and electric field and erasing of information in the other is reproducible. 2. The advertising medium according to claim 1, wherein the liquid crystal is microencapsulated. 3. The advertising medium according to claim 1, which is incorporated in a writing and erasing unit.