FR2482736A3 - Photothermoplastic recording process giving half tone picture - uses photoconductor and thermoplastic layer, which are heated, charged, exposed and cooled - Google Patents

Abstract

Photothermoplastic recording process for optical information uses an information carrier with a semiconductor sensitive to actinic radiation and a thermoplastic storage layer. The process involves charging, exposure, thermal development and cooling of the carrier to fix a visible image. The thermoplastic layer is preheated to a temp. between its Tg and flow temp., which is maintained until the end of thermal development, then the carrier is charged to potentials ensuring an electric field strength producing pondermotive forces in the thermoplastic layer ca. 5-10% below the shear modulus of this material at the recording temp. At the same time, the optical information is exposed at a strength of illumination which changes the resistance of the semiconductor layer by 10-15 times at the points with max. exposure. The charging and exposure times are determined from the formula ts=tm(tau)(In k)/(k-1) (in which ts is the charging time and tm the exposure time. tau is the dark relaxation time for a charge on a carrier. k is a multiple of a photosignal on a semiconductor layer at a max. exposure point). Half tone pictures can be produced without special rastering with a great signal-to-noise ratio for small exposure times.

Description

Electrophotographic recording method on thermoplastic support of optical information and itinformation support
For the implementation of the process.

The present invention relates to recording
optical information, and, more particularly, the
electrophotographic recording on thermoplas support
optical information and the information media for carrying out such methods.

 The invention is particularly applicable in photographic and cinematographic apparatus.

We know a method of recording images
optics on a photosemiconductive-thermoplastic system.

According to this method, one forms on a plate of the kind
used in the "Xerox" process, called xerographic, by
conventional methods, a latent electrostatic image. Then, the photoconductive layer of the xerographic plate is brought into contact with a dielectric thermoplastic film that an electro-discharge device has previously brought to an electrical charge opposite to that of the xerographic plate. After application of the load the surfaces are spread
layers. When the value of the air gap is appro-
In the critical area, there is an electric discharge in the image area accompanied by the transfer of the image.
electrostatic on the dielectric thermoplastic film.

There are various versions of this process which is called the method of transferring the relief of charges via an air space.

But these methods allow to have on the thermoplastic layers that the images reflected. In addition, it is difficult
to maintain constant and regular air space over the entire
area to be exhibited; resolution decreases with increasing
the air space, and a noticeable level of visibility appears.

In order to reduce the level of sail,
recharging, that is, forming an image of charges
electrostatic charges and then compensate the charges
on the bottom areas.

 There is also known a method of recording on a photoconductive thermoplastic material according to which a transparent photoconductive film with thermoplastic properties deposited on an electroconductive transparent support is loaded and exposed to an image projected onto this film.

The photoconductor is then brought to a softening temperature at which the image transmitting regions are deformed, and the electrostatic image develops into visible relief. By cooling to room temperature, the image is fixed.

 This process has a low photo sensitivity due to the need to combine in the same layer the properties of photosensitivity and thermoplasticity, a reduced number of work cycles due to the nonstability of the photographic layers, and a side effect considerable when the deformation takes place on the border between light and shadow, the transmission of halves requiring additional screening of the projected image.

 Methods are known for recording optical images on an information carrier comprising a semiconductive photosensitive layer and a memory thermoplastic layer successively deposited on a current-conducting support.

Recording methods are still known whose essential characteristics are as follows. On the free surface of a thermoplastic layer, an electrostatic charge is regularly distributed. This surface is then illuminated by actinic light with respect to the semiconductor layer and comprising information distributed in a useful manner in intensity. Under the action of lighting an electrostatic charge regularly distributed according to the surface of transforms into a relief of potentials modulated in space, translating the information contained in the optical image. After exposure, one can develop the relief of potentials immediately in a visible image, or develop it after a second uniform charge. This development is done by quickly bringing the thermoplastic layer to a temperature exceeding that of loss of rigidity so
to soften the diaper for a short time on the
heated thermoplastic layer appear under the action
driving forces, deformations or corresponding folds
the potential relief modulated in space.

The main defects of such a succession of steps
charge, exposure and development reside in a
lengthy process due to staged registration
low photographic sensitivity (as a result of the fall
significant intensity of the electrostatic field due to a relaxa
darkness of charges during the interval between
the step of charging the softening moment of the layer
thermoplastic) and low signal-to-noise ratios
the appearance of deformations on the unlit portions
of the thermoplastic layer.

In order to improve photosensitivity,
performs an additional charge of the thermoplastic layer after exposure and immediately before development.

This measure, by improving the sensitivity,
increase in the value of noise. Without eliminating others
defects above it further increases the duration of the process
recording.

The edge effect is avoided thanks to the charging steps
and recharge in regiMes ensuring the action, on a portion
of the surface, electrical forces during a period of
enough time to form an embossed relief from the
deformed thermoplastic layer. The embossed images accused
allow to reproduce large illuminated portions
constant optical images having a constant background, as with
silver halide photographic materials, but do not remedy other defects in the process.

To increase the signal-to-noise ratio is added to the above process steps of regular illumination of
the photosensitive layer after preload charge
secondary after regular illumination up to a potential
having the same sign as the prior charge, and charging
by a sign potential opposite to the first two after exposure and immediately before development.

 The large number of operations performed on the support during registration complicates the recording equipment, imposes more stringent requirements on the resistivities of the thermoplastic and conductive layers of the support. The values 1013 to 1015ohms.cm are the lower limits for the resistivities conditionnaAt the ability of these layers to a subsequent record, and most importantly, including additional charging and recharging steps.In order to avoid the field effects increasing the conductivity of layers, the layers are given a great thickness, cc which decreases the limiting resolution, and does not allow the use of inorganic semiconductor materials on a flexible support Large values of the resistances and the absence of leakage currents suppose a circuit capacitor equivalent of the information carrier. During illumination, the capacitor corresponding to the illuminated portion of the photosemiconductive layer is short-circuited. Such a representation of the support is rather approximate, and it can not characterize the optimal recording conditions.

 A defect common to all previous recording methods is also the lack of correlation between the values characterizing the recording process, such as, for example, charge potentials; the duration of the loading, exposure, recharge and development stages; and the parameters of the layers composing the support. It is impossible, if no such correlations have been established, to obtain the optimum recording conditions ensuring the maximum sensitivity, a high signal-to-noise ratio, the necessary values of the contrast and dynamics factor.

 Another known method of recording on a thermoplastic layer undergoing an embossed deformation deposited on a photoconductive layer having a conductive support comprising the already mentioned operations of charging the free surface of the thermoplastic layer to a first potential, exposure , second charge to a second potential and softening of the thermoplastic layer to create the conditions of formation of an accused relief image. The method consists in using the correlation between the load parameters (potential values) and recharge to arrive at the desired value of the contrast factor.

où VR et Vo sont tels que la soit suffisant # RE soit suffisante pour obtenir une valeur prédéterminée du facteur de contraste après apparition d'une déformation en relief accusé sur la couche thermoplastique à la suite d'un développement rapide.This method is implemented on an information carrier comprising a conductive substrate on which are successively deposited a photoconductive layer of thickness d5 and absolute dielectric constant 2 O 8 s and a thermoplastic layer of thickness dp and absolute dielectric constant o 8 p. This support is loaded to a first potential
op VO, and is then exposed in order to lower the potential up to the VE value on the illuminated portions and recharged to the charging potential VR, with which the distribution of the charge on the surfaces (T -RR can be expressed as follows:

where VR and Vo are such that the sufficient # RE is sufficient to obtain a predetermined value of the contrast factor after occurrence of an embossed deformation on the thermoplastic layer as a result of rapid development.

 To obtain low values of the contrast factor, the information carrier is first loaded at a relatively low initial potential; for recharging, a higher and sufficient voltage is applied to improve the contrast factor according to the relationship above.

 To obtain high values of the contrast factor, relatively high potentials are used for the first charge and corresponding potentials for recharging.

This process is based on two considerations
1) In any recognized relief image formation process, a predetermined minimum value of the charge density must be obtained before the appearance of the relief
2) there is a predetermined maximum value of the
density of charge above which the density of the relief charged does not increase noticeably.

Without taking into account the leakage currents, the method provides for using as information carrier materials
semiconductors and thermoplastics with enough resistivity
high, these carriers having to operate with relatively low intensities of the electric field -which can not
cause significant leakage currents.

The process considered, avoiding the presence of current
of escape and therefore the relaxation of darkness potentials on
the thermoplastic and semiconductive layers, does not comprise
no time correlations defining the periods of
charge, exposure, recharge and heating time
therefore, registration regimes can not be recommended
on the supports composed of semiconducting layers
and thin thermoplastics, especially with low resistivity materials (less than 1013 ohm.cm).

To implement this recording process
information, a support having a dielectric layer
deformable stick on which an image appears in form
of a chaotic array of peaks and valleys
regular spacing on an area 1 to 5 times higher
at the thickness of the layer, the height from the top
up to the trough on this chart depending on the value of the
electrostatic forces. The support has a structure
comprising a base, a conductive coating and layers
photosensitive semiconductor and thermoplastic materials
high resistivity.

The base is made of metal as in xerography
classical, for example aluminum, brass or glass
having a conductive coating.

it is known to use, as a basis for
information carriers, flexible substrates, for example,
polyethylene terephthalate containing
silicon, or cellulose triacetate, or polyterephthalate
ethylene.

 The use of such bases for information media comprising a thermoplastic layer and a photosensitive layer of a semiconductive inorganic material makes it more difficult to produce information carriers of unlimited length, since the flexible substrate used softens at low temperatures ( on the order of 60-80 ° C) and has significant transverse and longitudinal shrinkage, which degrades the quality of the image.

The actinic radiation-sensitive layer forming part of the carrier for the known information recording process may be made of photosensitive materials ordinarily used in electrophotography, such as, for example, amorphous selenium, Se-As mixtures,
Se-Te, and trisulphide - diarsenic triselenide; however, it is necessary to produce in these materials layers of intrinsic resistivity greater than 14 ohm.cm at the recording temperature.

 it is more advantageous to use layers of materials ordinarily applied to the production of vidicon targets, especially diarsenic triselenide with addition of Sb2S3, Sb2Se3 and heterostructures based on these compounds and materials A3.

 Glassy selenium, whose quantum yield is close to unity and the spectral range of sensitivity is greater than that of other materials, thanks to additions, has good photosensitivity, but it crystallizes rapidly during heating, which changes its characteristics and it gets older. As a result, it is not suitable for extended storage and multiple recordings.

The other materials have a significantly lower quantum efficiency than Se, which reduces the response time and the darkness / resistance ratio under illumination.

The thermoplastic layer is usually based on polymers, for example based on a copolymer of styrene and butyl methacrylate with the following molar composition, in%:
styrene from 30 to 60
butyl methacrylate 40 to 70
These carriers have low processing, recording, and information collection rates due to high melt temperatures (above 1000C) of the thermoplastic layer, which results in high recording temperatures and leads accordingly. use of high power development devices.

The high fluidity temperatures do not make it possible to develop and fix the electrostatic image rapidly, because they require prolonged cooling of the support during the successive charging, exposure and development processes and degrade the photographic sensitivity of the support in the process. case of simultaneous charge, exposure and development processes as a result of photoconductivity decay with the temperature of the semiconductor layer.

 It is known that the development temperature of the electrostatic image formed on the thermoplastic layer is close to the fluidity temperature of the thermoplastic material; as a result, high casting temperatures require the application of high power development devices, which decreases the performance of the information recording apparatus. heating the thermoplastic layer to high development temperatures and cooling to vitrification temperatures require a long time, which reduces the speed of recording and collecting information.

 The photographic sensitivity of most semiconductor materials used for the manufacture of multilayer photothermoplastic media decreases with increasing temperature; as a result, the high fluidity temperatures of the thermoplastic material corresponding to the optimal recording regimes cause a decrease in the general photographic sensitivity of such media.

 According to the process just defined, it is possible to use for recording the optical information, only thermoplastic materials with high resistivity keeping high potential values for a long time, because only these materials with high resistivity load up to at potentials higher than 300 V and suitable for recording1 while materials only accepting a load of less than 300 V, do not lend themselves to the formation of relief images in relief.This restriction, added to the The requirement for thermoplastic materials to keep the electrostatic charge in the softened state, considerably reduce the range of materials applicable for recording on thermoplastics, they require a high purity of the starting materials and a synthesis technology which increases the cost. the support; they do not make it possible to add thermomechanical and adhesive properties to the thermoplastic layer, since an overwhelming majority of these additions reduce the resistivity of the thermoplastic material.

 In accordance with the conventional xerographic practice, a potential is applied to the support distributed between the photosensitive and thermoplastic layers, in inverse proportion to the ratio of their capacities per unit area. Most of the potential is for the photoconductive layer because it has a larger dielectric constant than the thermoplastic layer, has a greater thickness and a smaller capacitance per unit area. During the exposure, the photoconductive layer becomes electroconductive and allows the charges at the interface between the photoconductive layer and the substrate to move at the boundary of the thermoplastic layer.

 During the temporary softening of the thermoplastic material, the mechanical forces due to the electrostatic charge of the latter deform the surface until the appearance of an accused relief structure, the height to the relief being proportional to the illumination received by the various portions .

 The specific features of an accused relief recording medium, as well as the large resistivity values of the conductive and thermoplastic photo layers, allow separate recording with charge transfer from the first layer to the second layer and subsequent recording when the loading, exposure and development operations are separated in time and succeed one another. These media have a considerable charge memory, which prevents rapid re-registration on the same image, reduces the range of semiconductors to be used to conventional xerographic materials, and requires large thicknesses of photosemiconductive inorganic layers (10 μm). which does not allow to realize them on a soft basis.

 A deformation with a pronounced relief appears on both the illuminated portions and those not illuminated, which naturally degrades the quality of the images obtained as a result of low signal / noise ratios.

 The high resistivity of the layers used to obtain pronounced relief deformation leads to a slow redistribution of the charge on exposure. As a result, optimal conditions require a large time interval between the development stage and the start of exposure (eg, low light recording and high exposure time). The law of commutativity not being respected on such systems, short exposure times abruptly reduce the photosensitivity of the recording method with relief structure accused. This virtually eliminates the possibility of applying the medium and the recording processes just described to the photography of moving objects. In addition, the high duration of load distribution makes it difficult to produce recording devices on moving media.

The embossed deformation occurs at developing temperatures that soften the thermoplastic layer at a temperature above the fluidity temperature. The development must castre the fastest possible, so that the electrostatic image formed does not have time to disappear. These development temperatures
high demands fast cooling for forces
due to surface tension do not have the time to
destroy the formed image.

This process, if it achieves a correspondence between
contrast factor and load potential values, do not
does not take into account the relationship between other parameters of the
registration process and the characteristics of the support
used; therefore we can not optimize the conditions
recording.

The aim of the invention is to provide a method of recording
electrophotographic optical information on thermo media
plastic and a support for its implementation, allowing
to obtain halftone images without special dithering and
high signal-to-noise ratio, for short exposure times.

For this purpose, the invention proposes an energetic process
electrophotographic recording of optical information on
thermoplastic support, in particular on an information carrier comprising a semiconductor layer sensitive to light
actinic and a thermoplastic storage layer; this
process comprises the steps of charging, exposing,
thermal development and cooling of the support for
fix the visible image; the process is particularly characterized
in that the storage layer is preheated
thermoplastic information carrier up to a temperature
chosen in the temperature range from
vitrification stage at the flow temperature or casting,
in that it maintains this temperature throughout the period
thermal development of the image, in that
then the support to potentials for which the intensity
of the electric field generates ponderomotive forces or
gravity in the unlit areas of the thermoplastic storage layer which are 5 to 1 OXb less than the
value of the shear modulus of the material of the layer
thermoplastic storage at the recording temperature
in the same way, and at the same time
optical to an illumination that varies from 10 to 15 times the
resistivity of the semiconductor layer on the maximum illumination portion, the charge and the exposure being effected for periods defined by the formula
ts = tm = k-1 lnX where: t5 is the charging time,
t is the exposure time,
m
is the dark relaxation time of the
load on the support,
k is the ratio resistance of darkness / resistance
under illumination of the semiconductor layer on the
portion with maximum illumination.

où : a, ss et X, sont des facteurs, tenant compte de la
diminution dans le temps de la conductibilité résiduelle
de la couche semiconductrice.We can reduce the time (tm) of exposure of N times compared to that of load (ts), the value N being defined by the formula given below.

where: a, ss and X, are factors, taking into account the
decrease in the time of the residual conductivity
of the semiconductor layer.

 An information carrier according to another aspect of the invention, making it possible to implement the method above, comprises a semiconductor layer that is sensitive to actinic light, a thermoplastic storage layer deposited on the first and an electroconductive layer, according to the invention. the actinic light-sensitive layer is made of an inorganic semiconductor material whose effective resistivity is equal to 10 h 10 ohm.cm at the recording temperature, and said storage thermoplastic layer is electrically bonded to the sensitive layer to actinic light, is made of a material whose resistivity is less than 1013 ohms.cm and during the recording, becomes greater than more than 10 times the resistivity of the semiconductor layer, the overall thickness of the semiconductor layers and storage thermoplastic being less than 5 μm.

In order to shift the spectral sensitivity towards the long wavelength domain, it is advantageous to constitute the actinic light sensitive semiconductor layer in amorphous arsenic chalcogenide alloyed with 1 to 7% by weight of thallium.
The spectral range of sensitivity of the support can be further enlarged by forming the actinic light sensitive semiconductor layer in amorphous arsenic chalcogenide alloyed with 3 to 10% by weight of bismuth.

 To improve the photosensitivity of the support, it is possible to produce the actinic light-sensitive semiconductor layer in monoclinic selenium. The amorphous gallium chalcogenide actinic light-sensitive semiconductor layer can also be formed by employing trisulfide, gallium triselenide, and solid solutions.

 The actinic light-sensitive layer is advantageously Ga2 S3, Ga2Se3; an actinic light-sensitive layer of residual conductivity semiconducting inorganic material appears to be advantageous.

 The actinic radiation-sensitive semiconductor layer may be constituted by a structure with at least two layers composed of materials whose resistivity is less than 108 ohm.cm, the resistivity of the two layers being between 1010 and 1012 ohm.cm.

In order to extend the functional possibilities of a thermoplastic storage layer based on vinylaromatic hydrocarbon and alkyl methacrylate copolymers, this layer may contain chemically active derivatives of styrene in an amount of X to 10 mol.C . To improve the adhesion of the thermoplastic storage layer to the semiconductor layer and to provide a multiple pull of the information directly from the thermoplastic layer, the thermoplastic storage layer may comprise vinylphenylisocyanate; the molecular proportions of the starting materials can be
styrene 34 to 38%
Butylmethacrylate 56 to 60c, of
Vinylphenylisocyanate 2 to 6%
it is further advantageous that the thermoplastic storage layer comprises vinylphenylamine in an amount of 5 to 10 mol.p with a styrene content of 30 to 40 mol.p and butyl methacrylate of 55 to 60 mol., fO, which allows to extend the storage time of the recorded information without degradation of its quality.

To lower the flow temperature of the thermoplastic layer, accelerate the process of recording the information and improve the sensitivity of the infomation medium, the thermoplastic storage layer may comprise vinylphenylisotiocyanate with the molecular proportion below starting products
styrene 30 to 40 ç
butylmethacrylate 50 to 60 fio
vinylphenylisotiocyanate 5 to 10, o
The sensitivity of the support having a thermoplastic layer obtained based on copolymers of alkyl methacrylate and chemically active derivative of styrene is improved, and the strength of the thermoplastic layer increased when the latter comprises halogenated styrene, the proportion of the starting materials being (in mol.ss:
alkyl methacrylate from 30 to 50
halogenated styrene from 35 to 65
chemically active derivative of styrene 5 to 15.

 Chemically active derivatives of styrene can be vinylphenylisocyanate, vinylphenylamine, vinylphenylisotiocyanate.

it is advantageous, in order to improve the extent of an information medium having a thermoplastic layer based on alkyl methacrylate copolymers with chemically active derivatives of styrene, that the thermoplastic storage layer comprises vinylnaphthalene, the proportion of the starting materials. being (mol)
octylmethacrylate from 50 to 55
chemically active derivative of the
styrene 5 to 10
vinylnaphthalene 40 to 45
As chemically active derivatives of styrene, it is possible to use vinylphenyl isocyanate, vinylphenylamine, vinylphenylisotiocyanate,
To improve the workability of the information carrier, it may have a flexible substrate based on polyethylene terephthalate containing 1,1-diacetyl ferrocene in a proportion of 0.05 to 0.5 parts by weight. Such a substrate has a higher heat resistance and elasticity than known flexible substrates.

 The invention will be better understood on reading the following description of examples of its embodiment, with reference to the single figure which shows the surface of a support after recording information on it.

 The method of recording the proposed information, based on the simultaneous realization of the steps of electric charge and exposure of a previously heated information carrier, is carried out using a support comprising an electroconductive coating. in electrical contact with a semiconductor layer sensitive to actinic radiation (hereinafter referred to as a photosemiconductive layer) and a thermoplastic storage layer, the two layers being interconnected electrically.

 The electrophysical and thermomechanical parameters of the support layers define the recording parameters (illumination, exposure time, charging time, potential of the electro-discharge electrode).

avec la condition initiale

dans lesquelles
# s, p ; ds, p ; # o # s,p sont respectivement les résistivi- tés, les épaisseurs et les constantes diélectriques absolues des couches semiconductrice (s) et thermoplastique (p).The process of redistribution of the voltages V between the layers as a result of an exposure of the portions of the support is defined by the system of equations (

with the initial condition

in which
# s, p; ds, p; # o # s, p are respectively the resistivities, the thicknesses and the absolute dielectric constants of the semiconductor (s) and thermoplastic (p) layers.

The indices d, 1 correspond to the dark and illuminated portions of the support k is the ratio of dark resistance / resistance to illumination of the semiconductor layer on the portion with maximum illumination.

the distribution of the potentials leads to the formation of a latent electrostatic image characterized by its electrostatic contrast ss V, defined as the difference between the tensions, on the thermoplastic layer, of illuminated portions VI and Vd of the support
pp
\ V - V 1 ~ V d (2)
PP
The recording of the images on the thermoplastic layer always assumes the deformation thereof under the action of ponderomotive forces (or gravity) corresponding to the electrostatic image. Therefore, to obtain a good quality image with a high signal-to-noise ratio, it is necessary to find a maximum difference between the electric fields in the thermoplastic layer on the illuminated and unlit portions of the support. The proposed support, designed for fast recording. images, is made of materials with specific resistance between 1 10 and 1012 ohm.cm, and it ensures the distribution of loads, even on the unlit portions of the support, in a time interval of 10-2 to 1 s. Therefore, it is useful to complete the recording of an image towards the moment of appearance of large intensities of the field in the thermoplastic layer on the unlit portions of the support.

In the preheated media recording method, the potential relief formation process is accompanied by simultaneous deformation of the surface of the thermoplastic layer. The maximum values of the signal / noise ratio are then obtained at the moment of action of the charging means at which the difference in voltage drops in the thermoplastic layer between the portions of the support having undergone illumination and those of unlitness reaches its maximum. .

The solution of the system of equations (1) makes it possible to study the electrostatic contrast formation kinetics ss V given by formula (2) as a function of the ratio of the parameters of the layers forming part of the support; in particular, the time tm for obtaining the maximum of LaV, V, chosen as the optimum exposure time, is written:

est le temps de relaxation
d'obscurité de la charge
sur le support.In the case of using semiconducting layers of low resistivity, when at least one order of magnitude, expression (3) can be written H
tm = ln K (4)
K-1

is the relaxation time
darkness of the charge
on the support.

Expression (3) shows that in order to reduce the exposure time (i.e., to increase the rate of electrostatic contrast formation) semiconductor layers of lower resistivity must be applied and / or larger of the ratio E dark resistance / resistance under K illumination (intense illuminations or high photosensitive semiconductor materials) .The maximum value of the electrostatic contrast corresponding to the exposure time is written

 Expression (6) shows that to obtain high contrast, it suffices to adopt a value of the ratio k ranging from 10 to 15, since f (10-15) tJ 1; an increase in the darkness / illumination resistance ratio beyond the range of 10 to 15 does not bring about significant contrast enhancement.

The case we have just analyzed assumes the formation of a latent electrostatic image only under the action of light. The required exposure time t to t 'of N times can be reduced compared to the charging time t5
mo during which the desired contrast must be obtained in
m using a photosensitive layer of a semiconductor material having a residual conductivity. The reduction in exposure time is explained by the fact that the electrostatic contrast increases in such a system for a certain time interval after the end of the exposure, thanks to the residual conductivity.

when the ratio of residual conductivity / dark conductivity varies after the end of the exposure due to an almost immediate (short time) and slow (long time, corresponding to ass 1) fall as a function of time according to the hyperbolic law K '= y K (1 + at) -ss, where y <1 (7) where a, ss, y are the residual conductivity parameters, we can reduce the exposure time by a duration of the order of
t5 - t = .----- (8) keeping then the sufficiently large values of k '.

Expression (8) shows that the exposure time can be reduced by N times, where

 The sensitivity of the thermoplastic layer to the deformation is proportional to the power four of the intensity of the electric field applied to this mouth.

Therefore, it is useful to use thermoplastic layers 0.1 to 3 Wm thick. This makes it possible to arrive relatively easily (with low potential values on the electric-glow device) at high intensities of the electric field and to obtain high resolutions because the deformation decreases with the increase in the thickness of the thermoplastic layer. Decreasing the thickness of the semiconductor layer improves the resolution of the medium, the projected optical image becoming less fuzzy for small drift lengths of the majority charge carriers across the thickness of the photosemiconductor. The small thickness of the sheets used makes it simpler to manufacture a substrate with a flexible substrate that can be used in rolls.

 The information medium does not maintain the electrostatic contrast for a long time; as a result, a subsequent recording in the impossible time can not occur when the loading, exposure and development steps are separated. Given this feature, the loading and exposure steps are performed simultaneously on a thermoplastic layer previously heated to the recording temperature. In this specific case, the proposed photothermoplastic support must be brought to a temperature above the vitrification point of the thermoplastic material used, but lower than the fluidity temperature of this material. The simplest method for achieving this purpose is to place the support on a flat furnace heated to the desired temperature and having dimensions greater than the size to heat the edges of the support regularly. When the thermoplastic layer reaches the predetermined temperature, the device is started up and the image is projected at the same time.

The projection of the image can be permanent because the support does not react to the lighting in the absence of potential on the surface of the thermoplastic layer.

 A repartition of the charges under the action of the light and the electric field creates the electrostatic contrast mentioned. On clear parts, the critical electric field strengths for the thermoplastic layer are reached more rapidly. As a result of a variable distribution of the electric charge and possible local irregularities in the thickness of the thermoplastic layer, depressions are formed in the latter.

 As the depth of a dip increases, the capacity of such a portion increases, and the potential decreases, causing the flow of the charges to the zone of minimal thickness of the thermoplastic layer. Thus, a self-accelerating process is established: a charge flowing in the hollow forms it in an intense way on the heated thermoplastic layer. The hollow formation process ends when it becomes possible for the load to pass through the remaining portion of the thermoplastic layer.

Thus, the high intensities, close to the critical values, of the electric field lead to a reduction in the charge on the surface of the thermoplastic layer, this being due to the chaotic appearance of micro-channels of current along which hollows are formed. the thermoplastic layer.

For a high degree of unevenness of the thickness of the thermoplastic layer the depressions formed along a current channel are all of identical circular shape and of approximately equal diameter, as shown in the figure.

The size of these recesses is a function of the viscosity of the material of the thermoplastic layer. The displacement of the thermoplastic material is more easily effected on a less viscous material by reducing the amount of material in the center of the channel and pushing it back towards the edges so that a bead is formed. As a result, an increase in the recording temperature leads to an increase in the diameter of the local deformations of the thermoplastic layer. The diameter also increases with the speed of obtaining critical intensity of the electric field on the thermoplastic layer.

 The self-accelerating process of trough formation along the current channel results in rapid deformation generation and allows the recording of the electrostatic contrast arising on a medium having a photosemiconductive layer with a resistance of less than 1012 ohm.cm, which significantly extends the range. materials suitable for producing photothermoplastic supports and making it possible to shift the sensitivity thereof towards the long wave domain of the spectrum.

 Such a recording method excludes the edge effect. The portions of the regularly charged thermoplastic photosemiconductor support undergo a deformation at the same statistical mean density. An increase in the charge on the surface of the thermoplastic layer brings that of the statistical average density of the number of current channels. This latter factor makes it possible to transmit halftone images at various densities of the deformation, similar to the number of centers of darkening in silver halide photography, and avoids the need for dithering to record d halftone images.

 Another advantage of the subject recording method, compared to the recognized relief recording method, is the possibility of achieving good signal-to-noise ratios by virtue of a noise attenuation on the unlit portions of the semiconductor photothermoplastic carrier. This is made possible because at low recording temperatures (slightly above the vitrification temperature) the thermoplastic materials have a high shear modulus. This last fact is at the origin of the existence of a load threshold from which the deformation of the thermoplastic layer begins. Therefore, if the electric-emitter device is disconnected at the moment when the electric field forces have already exceeded this threshold on the illuminated beaches of the thermoplastic layer and have not yet reached on the dark beaches, one only gets the deformation on the portions of the photothermoplastic semiconductor medium subjected to illumination. The signal-to-noise ratio then reaches its maximum value.

 The main aims of the invention are obtained, in particular the improvement of the photosensitivity, the intensification of the recording process and the obtaining of high resolutions thanks to the use in the support of thin semiconducting and thermoplastic layers. the thin layers being more elastic, it has proved very convenient to make this support having a layer of inorganic semiconductor material on a flexible substrate.

 The realization of the support on a flexible base is advantageous in the photographic equipment and cinema for the recording of electrical signals using an analyzer beam. The essential requirement then to be imposed on the support is its resistance to heat, enabling it to withstand, without tensile deformation, the influence of temperature during the application of the metal and semiconductor layers by thermal evaporation, as well as for the recording and erasing information.

One possibility has been to use the polyethylene terephthalate carriers generally used for thermoplastic recording.

 To improve the elasticity and heat resistance of the flexible substrate, it is then a copolymer based on polyethylene terephthalate containing from 0.05 to 0.5 by weight of 1,1-diacetylferrocene. The presence of the latter makes it possible to raise the softening temperature of the support to 90.degree. The thickness of the support will usually be in the range of 40 to 200 μm.

 the support material is obtained by synthesis according to a known method, without catalyst application.

The film is formed from the molten copolymer by extrusion or spinning it through a slot to create a layer of regular thickness along a flat solid surface and subsequent cooling of this layer.

 Thus, the support now becomes applicable, under the same practical conditions as the conventional film. In addition to its practical advantage, the flexible substrate based on polyethylene terephthalate containing diacetylferrocene in the above-mentioned proportions has made it possible to improve the thermomechanical characteristics of all the information medium.

 By providing the information carriers with the proposed structural substrate, their heat resistance is improved and the risk of warping is reduced by decreasing the longitudinal and transverse shrinkage up to 1-2fo.

 An increase in the softening temperature of the support makes it possible to raise the operating temperature during the recording of the information, and thus to adjust certain characteristics of the support, such as, for example, the ratio of dark resistance / resistance under illumination and the resistivity of darkness. The use of the proposed substrate enhances the contrast of the image on media when the information is read in reflected light of brown color. The transparency of the carrier in question is 35 to 45 μs at a wavelength of 4,000 to 11,000.

 On the flexible substrate is directly deposited an electroconductive layer having an ohmic resistance or a stop resistance with respect to the photosemiconductive layer. The electroconductive layer with high injection power of the majority charge carriers lowers the photosensitivity of the support due to high dark currents. In the proposed recording method, supports having electroconductive layers of different metals such as Ni, Cr, Al, Bi, Sb are used.

The severity of the requirements to be imposed on superficial conductivity. of the electroconductive layer increases when the resistance of the photoconductors used in the support decreases and the area of 1 image to be exposed increases
On the substrate to the conductive layer is deposited a semiconductor layer sensitive to actinic light.

According to the invention, this layer must fulfill an essential requirement: it must have a relatively low effective resistivity, compared to the values used in known optical image recording processes (xerography and thermoplastic recording), typically from 10 to 1012 ohm. cm at the recording temperature.

This fact makes it possible to extend the range of materials applicable for the manufacture of the supports implementing the process in question. Thus, all the materials usually applicable in xerography (for example, selenium, selenium-telaure and selenium-arsenic mixtures, inorganic semiconductors in binders associated with thermoplastic materials with a high softening temperature make it possible to According to the invention, the process of recording at high temperature then makes it possible to implement the method when the resistance of the semiconductor layer drops to the necessary values.

 Strong electric fields generating the field effects in the semiconductor material also allow the implementation of the method; the recording is then performed with the extreme intensities of the electric field reducing the resistance of the semiconductor layer to the desired value.

 For the majority of the conducting materials, an increase of the temperature or the intensity of the electric field provoke a decrease of sensitivity by fall of the photoconductibility under the influence of the temperature and / or the field. To obtain high photosensitivity it is advantageous to use semiconductor compounds with 10O ohm.cm specific resistivities at low recording temperatures.

 among these materials it is possible to mention first of all the group of semiconductor compounds that can be used for the production of vidicon targets, for example Zb2S3, Sb2Se3, As2S3, As2Se3 and others.

 It is advantageous, in order to improve the thermal stability of the support having selenium as a semiconductor layer, to use it in its monoclinic form.

The recording dynamics of the images is defined in the recording method proposed by the illumination values for which the ratio darkness resistance / resistance to illumination reaches values of 10 to 15. Therefore, the best Results when recording dimly lit objects are obtained on media having a semiconductor layer of As2Se3, i.e., the most sensitive layer. By modifying the As 2Se3 layer fabrication technology, a wide range of resistivities and sensitivities ratios are obtained which make it possible to produce versatile supports combining various combinations of these layers and thermoplastic materials.

 It is advantageous to apply, for the manufacture of the supports carry out the proposed recording method, solutions of compounds of the form (As2S3) 1 x- (As2Se3) x, which make it possible to adjust, by adjustment of the value x, the limit of the sensitivity wavelengths and the position of the maximum sensitivity in the visible range of the spectrum.

 It is advantageous, in order to widen the spectral range of sensitivity towards long waves, to combine the diarsenic chalcogenides with additions. Thus, the addition, at the diarsenic triselenide and / or the arsenic trisulphide, of thalium at a rate of 1 to 7% by weight decreases the resistivity and displaces the spectral range of sensitivity.

 To broaden the spectral range of sensitivity, the actinic light-sensitive semiconductor layer can be formed from amorphous arsenic chalcogenide doped with bismuth in a proportion of 3 to 10% by weight.

 In order to improve the photosensitivity, the actinic light-sensitive layer is formed of selenium in monoclinic form.

 It is also possible to use even lower resistivity materials, for example Ga2S3 and Ga2Se3. In the amorphous state, these materials have a specific resistance of 1010 to 1011 ohms.cm and make it possible to form a maximum contrast electrostatic image on the thermoplastic layer in a time of 10 to 10 seconds.

 The simultaneity of deformation and electrostatic contrast formation processes in the proposed recording method determines a recording regime on the medium where varying increases in electric field intensity in the thermoplastic layer create local deformations along microchannels current.

The presence of such microchannels of current results in autotramming of the image to be projected and avoids the blurring of the electrostatic image. It therefore becomes possible to use, as the actinic light-sensitive layer, a semiconductor heterostructure layer, even made from low-resistivity materials, of less than 108 ohms.cm, when the effective resistivity due to stop layer provides a value of 10 to 1012 ohm.cm, taking into account the overall thickness of the heterostructure.A similar constitution of the actinic light-sensitive layer extends the spectral range of sensitivity through the resistance ratio d darkness / resistance to illumination of the two materials applied in the heterostructure; it improves photosensitivity through a more complete application of the incident integral radiation energy and the temporal response of the medium in case of shooting with high levels of illumination.

 To reduce the exposure time, the actinic light-sensitive layer may be made of a residual photoconductivity semiconductor material (hereinafter referred to as the photoconductive layer). The exposure time is then reduced by a value equal to the residual photoconductivity time, because the electrostatic contrast reaches the value necessary for the deformation under the action of the charging current.

 A thermoplastic layer is deposited on the photoconductive layer so that the two layers are in electrical contact. The thermoplastic layer is made of a deformable material in a range of temperatures from its vitrification temperature to that of its fluidity in an electric field having an intensity greater than 106 V / cm.

 In said range of temperatures, only portions of the surface of the thermoplastic layer influenced by actinic light are deformed with formation of funnel-shaped depressions. The deformation of the unlit portions of the surface decreases, and thereby the sensitivity of the information medium and the contrast of the recorded image are improved.

In the practical implementation, the thermoplastic layer can have a considerable fluidity at the ambient temperature (for example, when recording on the continuously moving strip of the support) or undergo a crosslinking during the deformation in order to prolonged storage of the recorded information. The thermoplastic layer may have any color. However, either the layer or the substrate provided for each concrete example of the use of the support is transparent to the spectral range defining the sensitivity of the semiconductor. -
The information carrier is made so that the thickness of the thermoplastic layer is less than that of the photoconductive layer, their overall thickness not exceeding 5 .mu.m. Therefore, during the recording of the information is obtained on the unlit portions of the support an intensity of the electric field generating in the thermoplastic layer of ponderomotive forces 5 to 1 less than the shear modulus at the recording temperature. Thus, there is no deformation on the unlit portions of the medium and the recorded image is high contrast.

 The proposed method uses, for the recording of information, a carrier having a resistivity storage thermoplastic layer of less than 1013 ohms.cm at the recording temperature and a thickness of 0.1 to 3 μm.

This makes it possible to increase the resolution of supports having a thermoplastic, made both of known materials (for example, butylmethacrylate-acrylonitrile copolymers, styrene-butadiene and butyl methacrylate copolymers, copolymers of unsaturated resinates) and of copolymers having the proposed composition. .

 the electrostatic charge of such layers creates intense electric fields, of the order of 106 V / cm, and increases the conductivity of the thermoplastic layer. It then becomes possible to apply, for the manufacture of the support, copolymers containing polar groups easily polarizable in the electric field. It also becomes possible to give the supports predetermined properties E modifying the composition of the thermoplastic layer, while maintaining a satisfactory resolution.

où : R est le phényl, le naphtyl, le chlorphényl ou le
fluorphényl,
R1 est le butyl ou l'octyl,
x est l'hydrogène, l'alkoyl, l'alcoxygroupe ou un
halogène,
y est un-groupe amine, isocyanate ou isothiocyanate.A material proposed for the manufacture of the thermoplastic layer is a triple copolymer containing chemically active styrene, butyl methacrylate and chemically active styrene derivatives having the formula

where: R is phenyl, naphthyl, chlorphenyl or
fluorphényl,
R1 is butyl or octyl,
x is hydrogen, alkoyl, alkoxygroup or a
halogen,
y is an amine, isocyanate or isothiocyanate group.

This material for the manufacture of the thermoplastic layer is obtained by radical copolymerization of the monomers in the presence of an initiator. the proportions of the monomers in the starting mixture are chosen so as to obtain thermoplastic materials capable of forming a film and transparencies whose optimal parameters are
intrinsic viscosity of 0.14 to 0.21
glass transition polnt from 32 to 600C
casting temperature from 70 to 860C
The thermoplastic layer is deposited by spraying the photoconductive layer with the copolymer solution in an organic solvent, for example toluene. The thickness of the thermoplastic layer is of the order of 1 to 3 μm.

 As chemically active derivatives of styrene, vinyphenylisocyanate, vinylphenylamine, vinylphenylisothiocyanate and other derivatives can be used.

An information carrier whose thermoplastic storage layer is based on triple styrene, butylmethacrylate and vinylphenylisocyanate copolymer with the proportions (mol%)
styrene from 34 to 38
butylmethacrylate from 56 to 60
vinylphenylisocyanate of 2 to 6 'keeps the recorded image up to the casting temperature of the thermoplastic layer. This result is obtained by the addition in the copolymer of groups - NCO -, bridging the macromolecules during the recording, pais during the storage of the recorded information.

 At the same time, the adhesion of the thermoplastic layer to the semiconductor is improved, which makes it possible to use the information carrier to make a large quantity of copies.

 The use of the support described avoids auxiliary technological operations, such as, for example, the manufacture of nickel matrices or the irradiation of the thermoplastic layer by ultraviolet rays to fix the image by crosslinking the polymer.

An extension of the storage time of the recorded information without degradation of the contrast is also obtained by using an information carrier in which the thermoplastic layer is based on a triple copolymer of styrene, butyl methacrylate and vinylphenylamine in the proportions
styrene 30 to 40 (<p molecular)
butylmethacrylate from 55 to 60 (dO)
vinylphenylamine from 5 to 10 (dO
the images reproduced on the media can be stored for a very long time. The stability of the recorded images makes it possible to use the support proposed for the print, as a photographic snapshot.

using an information carrier in which the thermoplastic storage layer is based on styrene, butylmethacrylate and vinylphenylisothiocyanate triple copolymer in the molecular po proportions)
styrene 30 to 40
butyl methacrylate from 50 to 60
vinylphenylisothiocyanate from 5 to 10
higher photosensitivity of the support is obtained than that of the support, the thermoplastic layer of which is of styrene-butyl methacrylate copolymer, and an extension of the storage time of the recorded information.

 Cold flow is almost completely eliminated by adding crosslinking NCO groups to the copolymer.

The casting temperature of the thermoplastic layer is lowered, improving the overall photosensitivity of the information carrier by increasing the content of butyl methacrylate chains in the copolymer. Lowering the flow temperature of the thermoplastic layer also increases the speed of development and fixing of the recorded information.

In order to improve the photosensitivity, retaining other favorable characteristics of the support (image fixing, wear resistance during the print, improved adhesion, etc.) in the triple copolymer containing alkyl methacrylate units and of vinylphenylisothiocyanate (or vinylphenylisocyanate, or vinylphenylamine), the styrene units are filled with halogenated styrene units, in the following proportions (#, molecular o)
alkylmethacrylate from 30 to 50
styrene derivatives
chemically active from 5 to 15
halogen from 35 to 65
When it becomes necessary to increase the range, the copolymer should contain vinylnaphthalene units with the following proportions of components (molecular%)
alkyl methacrylate from 50 to 55
styrene derivatives
chemically active from 5 to 10
vinylnaphthalene 40 to 45
This effect is obtained by increasing the conjugation chain by substituting naphthalic nuclei for benzene rings.

Concrete examples of implementation of the invention confirming the possibility of implementing the claimed process, will now be given
EXAMPLE 1 A photothermoplastic support is used comprising a polyethylene terephthalate-based flexible substrate with a thin chromium coating, a 3 m thick As2 Se3 photoconductive layer and a thermoplastic butyl methacrylate copolymer layer of 8 μm. thicker. The glass transition point of the thermoplastic layer is 45 ° C., its flow temperature is 920 ° C.
The recording temperature is chosen to be 650 C. The resistivity of the photoconductive layer at this temperature is 3.10 ohm.cm and that of the thermoplastic layer is 7.1012 ohm.cm. The media is placed in the recording apparatus and is heated to the recording temperature of 550C. The diaphragm of the objective is adjusted according to the illumination of the object, so that the ratio of variation of the resistance-of the photoconductive layer on the portions with maximum illumination does not exceed 10, that is to say The illuminance of the corona charged body and the potential of the electro-corona wire are selected so that during simultaneous exposure and charging the light emitted will be 17 lux. the intensity of the electric field on the portions of the unlit support is 5 to 10 5 O less than the value causing a ponderomotive force of 0.8 kg / cm 2, equal in value to the size of the shear modulus of the layer thermoplastic at a temperature of 65 OC.

 Having thus adjusted the diaphragm to 4, for example, to provide on the most illuminated portions a darkness / resistance ratio under illumination equal to 10 and with a potential of the corona electrode of 6 kV, the image on the support heated for a time t5 = 0.2 s. the shutter function is here fulfilled by the switching-on time of the corona charging device.

 An image formed by microdeformations whose size is of the order of 3 μm and whose distribution density increases with illumination, from 10 to 10 4 / mm 2, is obtained.

The dynamic range of recorded illumination is from 2 to 17 lux.

Example 2. A support is used. photothermoplastic according to Example 1. The recording temperature is 800C.

The resistivity of the photoconductive layer at this temperature is 1.4.1010 ohms.cm. the shear modulus is lowered to 0.11 kg / cm 2; the photosensitivity of the photoconductive layer is also lowered and a darkness / resistance ratio under illumination of 10 is obtained and for an illumination of 25 lux. The diaphragm is set to 3.5, the corona electrode voltage is 4.5 V, the charging and exposure time is 0.01 seconds.

 An image formed by separate micro-deformations, the size of which is 5 in, is obtained with a good reproduction of half-tones without edge effects. the dynamics is from 1 to 25 lux.

EXAMPLE 3 A photothermal plastic carrier having a flexible polyethylene terephthalate substrate with a thin chromium coating, a photoconductive layer of arsenic trisulphide and a thermoplastic butyl methacrylate-styrene copolymer layer of 1 μm thickness was used. having a glass transition point of 450C and a flow temperature of 920C. The effective resistivity is 1.2 × 10 12 ohm.cm for a thickness of 1.5 μm. The recording temperature is 840C. The shear modulus is 0.105 kg / cm 2 at this temperature. The resistivity of the photoconductive layer is 1.4 × 10 11 nm / cm at the recording temperature. A ratio of darkness / resistance under illumination equal to 10 is obtained under illumination of 200 lux. The charging time and the exposure time are 0.1 s and the potential is 3 kV.

 An image formed by deformations having a dimension of 3 μm is obtained, reproducing the halftones in the range of illuminations from 27 to 200 lux.

Example 4. A support according to Example 3 is used, in which the photoconductive layer is in arsenic triselenide. The recording temperature is 700C, at which the shear modulus is 0.6 kg / cm.

The effective resistivity of the thermoplastic layer is 7.1012 ohm.cm for the thickness of 0.3 μm and that for the photoconductive layer of 3.1010 ohm.cm. Under 1 lux lighting, the ratio of darkness to resistance under illumination is 8. For an exposure of 0.1 s and a potential of 6 kV an image is obtained which reproduces the halftones in the range of illumination. from 0.13 to 1 lux.

Example 5. An information carrier comprising a flexible substrate 50 μm thick based on polyethylene terephthalate with 0.5 weight part of 1,1-diacetylferrocene is used. On the substrate is deposited by vacuum evaporation, a photosensitive layer of amorphous arsenic selenide of 2 microns thick. On the photosensitive layer is deposited, by watering in toluene solution, a thermoplastic layer based on triple styrene-butylmethacrylate-vinylphenylisocyanate copolymer 1.5 microns thick with the following proportions (o molecular)
styrene 38
butyl methacrylate 60
vinylphenylisocyanate 2
Such a thermoplastic layer has a glass transition point of 330C and a flow temperature of 580C. The recording temperature is 480C.

The effective resistivity of the photosensitive layer is 10 ohms.cm at this temperature. The ratio of darkness resistance / resistance under illumination is equal to 10 for an illumination of 16 lux. The charging voltage adopted is 4.5 kV. An image formed by local deformations, the dimensions of which are approximately 2 μm, is obtained and reproduces the halftones in the illumination range of 6 to 20 lux.

During recording there is a bridging of macromolecules to keep the image reproduced for a long time at high temperature. No erasure of the image was observed by keeping the sample at the fluid temperature for 5 hours.

Example 5. The information medium contains the same layers as that described in Example 5.

The thermoplastic layer, 3.2 μm thick, is based on triple styrene-butylmethacrylate-vinylphenylisothiocyanate copolymer with the proportions of the following components (molecular)
styrene 30
butyl methacrylate 60
vinylphenylisothiocyanate 10
The glass transition point is 550C, the casting temperature is 700C. The recording temperature adopted is 60 C. At this temperature, the effective resistivity of the photoconductive layer is 10-11 ohms.cm, the ratio of darkness resistance / resistance under illumination is 9 at illumination of 28 lux. obtains an image formed by local deformations with a size of 2.5 μm, reproducing half-tones in the range of illuminations from 2 to 25 lux.

 Example 7. The information medium contains the same layers as that described in Example 5.

the thermoplastic layer is 2 μm thick; it is based on triple styrene-butylmethacrylatevinylphenylamine copolymer with the proportions of the components indicated below (molecular)
styrene 32
butyl methacrylate 60
vinylphenylamine 8
the glass transition point of this thermoplastic material is 450C, its casting temperature is 820C. the recording temperature adopted is 68 ° C.

At this temperature the effective resistivity of the photoconductive layer is equal to 2.5 × 10 ohm.cm, the ratio of darkness resistance / resistance under illumination is equal to 10 at illumination of 35 lux. An image formed by.

deformations whose dimension is 1 Fm, reproducing halftones in the range of illuminations from 10 to 40 lux.

the reproduced images can be stored for practically infinite time. The stability of the recorded images makes it possible to use the support for the print.

8. The information carrier contains the same layers as that described in Example 5. The thermoplastic layer is 3.5 μm thick. It is based on octylmethacrylate-vinylnaphthalene-vinylphenylisothioc copolymer, yanate, with the composition below (% molecular)
octylmethacrylate 50
vinylnaphthalene 40
vinylphenylisothiocyanate 10
This thermoplastic material has a glass transition point equal to 54 C, a casting temperature equal to 670C.

The recording temperature adopted is 600C. The effective resistivity of the photoconductive layer is 5.8 0.10 11 ohm.cm at 600C, and the ratio of dark strength / resistance under illumination is 9 at illumination of 28 lux. The potential of the corona wire is 5 kV, the charging and exposure time is 0.4 s. An image formed by local deformations whose dimension is of the order of 2 μm is obtained. The range of illuminations recorded on the support ranges from 0.2 to 26 lux.

Example 9. The information carrier contains the same layers as described in Example 5. The 1.5 μm thick thermoplastic layer is based on octyl methacrylate fluoromyrene-vinylphenylamine copolymer with composition below (molecular) :
octylmethacrylate - 50
fluorostyrene 35
vinylphenylamine 15
The glass transition point of the thermoplastic material is 35 C, the casting temperature of 640C.

The recording temperature is 50 ° C. At this temperature the effective resistivity of the photoconductive layer is 9.1 ohm.cm, the darkness / resistance ratio under illumination of 16 lux under illumination. The image recorded on the medium is formed by local deformations with a size of 2.5 Fm, and reproduces halftones in the illumination range of 0.2 to 26 lux.

Example 10 A photothermoplastic carrier is used comprising a flexible polyethylene terephthalate substrate, a chromium conductive coating and photoconductive and thermoplastic layers.

The photoconductive layer is deposited on a conductive electrode by vacuum evaporation. It contains arsenic triselenide alloyed with 5% by weight of thallium. The thickness of the photoconductive layer is 2 μm. The dark resistivity is 5.10 ohm.cm at the recording temperature. the darkness / resistance ratio under illumination of the photoconductive layer is equal to 15 for an incident energy of 5 × 10 7 J / cm 2, the wavelength of the radiation being 0.7 μm. the thermoplastic layer based on triple copolymer contains 30 mol%. styrene elements, 6059 butyl methacrylate elements and 10% vinylphenyl isothiocyanate elements. It is deposited by spraying on the photoconductive layer. the thickness of the thermoplastic layer is 1.5 μm. The glass transition point is 550C, the casting temperature is 700C. the modulus of elasticity is equal to 0.12 kg / cm2 at the recording temperature
The recording of an image on the photothermoplastic support is done in a recording cell, having previously brought the support to 600C and adjusted the voltage of the corona electrode to 4.5 kV. The charging time, equal to the exposure time, is 0.2 s. The exposure is carried out in light, with various spectral compositions in the incident energy range of 3.10 8 to 10.6 J / cm.

An image formed by local deformations of the thermoplastic layer whose size is of the order of 1 μm in the wave range of 0.5 to 1 μm is obtained. Thus, the spectral sensitivity of the support is shifted towards the long wave domain by 0.2 μm relative to that of a non-alloyed arsenic triselenide support.
Example 11. A photothermoplastic support comprising the same layers as in Example 10 is used.

 The photoconductive layer, 2 μm thick is in arsenic selenide alloyed with 7% by weight of bismuth.

The dark resistivity of the photoconductive layer is 7.10 ohms.cm at the recording temperature.

 An image is recorded on the photothermoplast carrier preheated to 600C and a voltage of the 4.5kV corona electrode. The charging and exposure times are 0.05 s. Exposure is by radiation to various spectral compositions in the range of 0.6 to 1 μm, at energies of 10 5 to 10 7 J / cm. An image on the support is obtained by forming a partition of local deformations of the thermoplastic layer in a range of lengths from 0.6 to 1.0 μm. The spectral sensitivity range obtained exceeds the spectral range of sensitivity of the arsenic triselenide support by 0.2 μm.

Example 12 A thermoplastic support containing the same layers as in Example 10 is used.

The 1.5 μm thick thermoplastic layer is based on a triple styrene-butylmethacrylatevinylphenylisocyanate copolymer, the molecular composition being
styrene 38%
butyl methacrylate 60%
vinylphenylisocyanate 2 ss
The glass transition point of the thermoplastic material is 33 ° C; its casting temperature is 580C.

 The photoconductive layer, 2.5 μm thick, is based on selenium, in monoclinic form. The dark resistivity of the semiconductor is 1010 ohms.cm.

The ratio of darkness resistance / resistance under illumination is equal to 15 for an illumination of 2 lux.

 To record an image, the media is first heated to 480C. Then the surface of the support is loaded, applying a voltage of 4.5 kV on the corona electrode.

At the same time the support is exposed for 0.1 s. The projected image is materialized on the support by local deformations of the thermoplastic layer reproducing the halftones in a range of illuminations of 0.1 to 2 lux. The low level of recorded illumination indicates a significant increase in the sensitivity of the single application medium, compared to supports based on other semiconductor layers.

Example 17. A photothermoplastic support containing the same layers as in Example 10 is used.

 The photoconductive layer, 2 μm thick, is based on amorphous gallium triselenide amorphous actinic light. The dark resistivity of the photoconductive layer is 1010 ohm.cm at the recording temperature. The ratio of darkness strength / resistance under illumination is 15 for an illumination of 12 lux.

 An image is recorded on the media previously heated to 600C. The load of the support is carried out by applying a voltage of 4.5 kV on the electric corona electrode.

The exposure is for 0.01 s. An image reproducing the halftones in an illuminance range of 5 to 12 lux with a short charge and exposure time is obtained.

 EXAMPLE 14 A photothermoplastic support containing the same layers as in Example 10 is used. The photoconductive layer 2.5 μm thick is in cadmium selenide having a residual conductivity. The dark resistivity of the semiconductor is 1010 ohm.cm at the recording temperature. The resistance-darkness / resistance under illumination ratio is 10 for an illumination of 6 lux. The value of the residual conductivity is 80% of the photoconductivity value, 1 s after the cessation of exposure.

 An image is recorded on the support previously heated up to 60 C. Simultaneously a voltage of 4.5 kV is applied to the corona electrode and the exposure occurs.

The exposure time is 0.01 s. After this time the exposure ceases, while the support load continues for 0.5 s. The contrast of the image is increased after cessation of the exposure due to the residual conductivity. Example 15. The information medium contains the same layers as in Example 10. The actinic light-sensitive photoconductive layer is constituted by a heterojunction based on cadmium sulphide and arsenic selenide alloyed with 5% by weight of thallium. The thickness of the cadmium sulphide layer is 1 μm, the ratio of darkness strength / resistance under illumination is equal to 10 for an illumination of 1 lux. The dark resistivity is 1010 ohms.cm.

 The thickness of the thallium-alloyed arsenic selenide layer is 1.5 μm. The effective resistivity of the photoconductive layer is 1011 ohms.cm.

 An image is recorded on the support previously brought to 6O0C. The charge of the support is effected by electrical corona discharge created by application of a voltage of 4.5 kV on the corona electrode. The charging time, equal to the exposure time, is 0.5 s. An image is obtained by repartitioning local deformation densities of the thermoplastine layer between the portions at various levels of illumination.

The recording of the image is possible in a wide spectral range, from 0.4 to 1 pa.

16. The information carrier comprises a flexible substrate of 50 .mu.m thick, based on polyethylene terephthalate containing 0.5. by weight of 1,1-diacetylferrocene. On this substrate is deposited, by vacuum evaporation, an amorphous gallium selenide photosensitive layer of 3 microns thick. On this is deposited, by watering from a solution in an organic solvent, such as toluene, a thermoplastic layer of styrene, butylmethacrylate and vinylphenylisocyanate triple copolymer of 2 Fm thick. The molecular composition of this layer is
styrene 38 fie
butyl methacrylate 60%
vinylphenylisocyanate 2 fo
Such a thermoplastic layer has the following rustic characteristics: characteristic viscosity: 0.21 glass transition point: 3300; flow temperature: 580C; media temperature at recording: 48 C, corona wire potential: 4.5 kV media sensitivity: 107 cm2 / d. The image storage time at 20 C is virtually unlimited.

Example 17. The information carrier contains the same layers as that of Example 16, and its manufacturing technology is analogous.

The 3 m thick thermoplastic layer is based on triple styrene-butylmethacrylatevinylphenylamine copolymer with the molecular proportion of components below
styrene 32 ço
butylmethacrylate 60 i0
vinylphenylamine 8%
The characteristic viscosity of the thermoplastic layer is 0.17; its glass transition point is 450C; and its casting temperature is 820C. An image is recorded at 650G, with a potential of the 4.5 kV corona wire. The sensitivity of the support is equal to 107 cm 2 / J.

Example 18. The information carrier has the same layers as that of Example 16, and its manufacturing technology is similar.

The thermoplastic layer, 2 μm thick, is based on triple styrene-butylmethacrylatevinylphenylamine copolymer with the molecular proportion of components below
styrene 35 He
butyl methacrylate 60%
vinylphenylamine 5%
The characteristic discom mity of the continuous thermoplastic layer is 0.18; the glass transition point is 430C; the casting temperature is 790C; the recording temperature is 620C; the potential of the corona wire is 4.2 kV. The sensitivity of the support is 107 cm2 / J.

Example 19. The information carrier has the same layers as that of Example 16, and its manufacturing technology is analogous.

The thermoplastic layer, 2 μm thick, is based on triple styrene-butylmethacrylatevinylphenylisothiocyanate copolymer with the molecular proportion of components below
styrene 30%
butyl methacrylate 60%
vinylphenylisothiocyanate 10%
The characteristic viscosity of the thermoplastic layer is 0.2; the glass transition point is 550C; the casting temperature is 700C; the recording temperature is 670C; the potential of the corona wire is 4.5 kV. The sensitivity is 2.107 cm2 / day.

Example 20.- The information carrier contains the same layers as that of. Example 16, and its manufacturing technology is analogous.

The thermoplastic layer, 2 μm thick, is based on triple styrene-butylmethacrylate vinylphenylisothiocyanate copolymer with the molecular composition below
styrene 32 ep
butylmethacrylate 60 fo
vinylphenylisothiocyanate 8?, o
The characteristic viscosity of the thermoplastic layer is 0.20; the glass transition point is 480C; the casting temperature is 800C; the recording temperature of the information is 620C; the potential of the corona wire is 4.5 kV. The sensitivity of the support is equal to 2.107 cm 2 / J.

 Example 21. The information carrier has the same layers as that of Example 16, and its manufacturing technology is analogous.

The thermoplastic layer, 2 μm thick, is based on triple styrene-butylmethacrylatevinylphenylisothiocyanate copolymer, the molecular proportion of the components being
styrene 35 fD
butylmethacrylate 60 ffi
vinylphenylisothiocyanate 5%
The characteristic viscosity of the thermoplastic layer is 0.16; the glass transition point is 440C; the casting temperature is 76 C; the recording temperature is 600C; the potential of the corona wire is 4.2 kV. The sensitivity of the support is 3.107 cm 2 / J.

Example 22 The information carrier comprises a thermoplastic layer based on chemically active vinyl naphthalene-derived alkyl methacrylate copolymer of styrene.

 The thermoplastic material is obtained by heating 3.96 g (50% molecular weight) of octyl methacrylate, 2.77 g (45 mol%) of 1-vinyl naphthalene, 0.24 g (5 mol%) of styrene derivatives, 0, 13 g (2% molecular) of biocrystalline azodiiso acid dinitrile in a sealed ampule, from which oxygen was removed from the air for 15 hours at 80.degree. C.

 The resulting copolymer is dissolved in 40 ml of benzene and reprecipitated by pouring it dropwise and stirring in 60 ml of methanol. The polymer is filtered, washed with methanol and dried in vacuo at room temperature.

For the various styrene derivatives, the following characteristics of the thermoplastic layer are obtained
1. Copolymer of octyl methacrylate (50 molecular weight), vinyl naphthalene (40 molecular weight) and vinyl phenyl isothiocyanate (10 molecular weight): glass transition point 540C; casting temperature 66 to 67 ° C; characteristic viscosity of 0.10.

 2. Copolymer of octylmethacrylate (50% molecular), vinylnaphthalene (45% molecular) and vinylphenylisothiocyanate (5% molecular): the glass transition point of 540C; casting temperature of 700C; characteristic viscosity of 0.13.

 3. Copolymer of octyl methacrylate (50% molecular 9), vinyl naphthalene (40% molecular) and vinyl phenylamine (10% molecular): glass transition point 54-560C; casting temperature of 750C; and characteristic viscosity of 0.13.

Example 23 The information carrier comprises a thermoplastic layer based on chemically active styrene-derived alkylmethacrylate halogenide-styrene copolymer.

the thermoplastic layer comprises
1. 50% molecular octylmethacrylate
4-fluorostyrene 35 ss
n-vinylphenylamine 15%
The glass transition point is 55-36 C, the casting temperature 64-65 C, the characteristic viscosity 0.32.

2. n-fluorostyrene 50% molecular octyl methacrylate 40%
n-vinylphenylisothiocyanate 10%
The glass transition point is 48-50 C, the casting temperature 74-76 C and the characteristic viscosity 0.21
3. n-Fluoro-styrene 65% Molecular
octylmethacrylate 30? / o "
n-vinylphenyl isocyanate 5%
the glass transition point is 48-50 C, the casting temperature is 74-750C, and the typical viscosity is 0.32.

4. n-Chlor-styrene 40 7, Molecular
octylmethacrylate 50 fi
n-vinylphenylamine 7 ',
The glass transition point is 49-50 C, the casting temperature 75-77 C and the characteristic viscosity 0.32.

 It goes without saying and as it follows already from the foregoing, the invention is not limited to that of its modes of application nor to those of the embodiments of its various parts, having been more particularly considered; it embraces, on the contrary, all variants.

Claims (18)

 A method of electrophotographic recording on a thermoplastic carrier of optical information on an information carrier having a semiconductor layer responsive to actinic light and a thermoplastic storage layer, comprising the steps of charging, exposing, developing thermal and cooling of the support for fixing a visible image, characterized in that the thermoplastic layer of storage of the information medium is previously carried at a temperature chosen in the range from its glass transition point to its casting temperature. and it is maintained until the end of the thermal development of the image, in that the support is then charged to potentials ensuring an intensity of the electric field generating, in the unlit areas of the thermoplastic memory layer, forces 5 to 10% lower than the value of the shear modulus of the material of the layer moplastic at the recording temperature, and simultaneously exposing the optical information to an illumination varying from 10 to 15 times the resistance of the semiconductor layer to the maximum illumination exposure portion, the charge and theposition taking place during periods defined by the formula  t ~~~~~  m In K, where  3; 2-1 ts is the charging time, tm the exposure time, the dark relaxation time of the charge on the support, K the darkness / resistance resistance in illumination of the semiconductor layer where it undergoes maximum illumination.  2. Method according to claim 1, characterized in that the exposure time (tm) is N times lower than the charging time (tu), the value N being defined by the formula

 are factors that take into account the decay with time of the residual conductivity of the semiconductor layer.  An information carrier for carrying out the method according to claim 1, comprising a semiconductor layer responsive to actinic light, a thermoplastic storage layer and an electroconductive layer deposited thereon, characterized in that the sensitive layer to actinic light is an inorganic semiconductor material whose effective resistivity is equal to 1010 to 1012 ohms-cm at the recording temperature, while the thermoplastic storage layer, which is electrically connected to the light-sensitive layer actinic, is in a material whose resistivity at the recording temperature is less than 1013 ohms-cm during the recording and exceeds by more than 10 faiths the resistivity of the semiconductor layer, the total thickness of the semiconductor layers and storage thermoplastic being less than 5 em.  4. Information carrier according to claim 3, characterized in that the actinic light-sensitive semiconductor layer is made of a semiconductive inorganic material having a residual conductivity.  An information carrier according to claim 3 or 4, characterized in that the actinic light sensitive semiconductor layer is either amorphous arsenic chalcogenide alloyed with 1 to 7% by weight thallium or 3 to 10% by weight. weight of bismuth, an amorphous gallium chalcogenide.  6. An information carrier according to claim 3, or 4, characterized in that the actinic light-sensitive semiconductor layer is monoclinically modified selenium.  7. Information carrier according to claim 3 or 4, characterized in that the actinic light-sensitive semiconductor layer is constituted by an at least two-layer structure, composed of materials whose resistivity is less than 108 ohms. .cm; and the effective value of the resistor is between 101 and 1012 ohms.cm.  8. Information carrier according to any one of claims 3 to 7, wherein the thermoplastic layer is based on vinylaromatic hydrocarbon copolymers and alkylmethacrylate, characterized in that the thermoplastic memory layer contains 2 to 10% G chemically active derivatives of styrene (molecular proportion).  Information carrier according to claim 8, characterized in that the thermoplastic storage layer contains vinylphenylisocyanate, the molecular proportion of the components being  styrene 34 to 38%  butylmethacrylate 56 to 60 #jo  vinylphenylisocyanate 2 to 6  10. An information carrier according to claim 8, characterized in that the thermoplastic storage layer contains 5 to 10% molecular vinylphenylamine, the molecular proportion of the other components being either 30 to 40% styrene and 50 to 60% butyl methacrylate or 50 to 55% octylmethacrylate and 40 to 45 phenylnaphthalene.  11. An information carrier according to claim 8, characterized in that the thermoplastic storage layer contains a molecular proportion of 5 to 10% of vinylphenyl isothiocyanate, the molecular proportion of the other components being either 55 to 600% of butyl methacrylate and 30 to 40% of styrene, 50 to 55% octyl methacrylate and 40 to 45% vinyl naphthalene.  12. The information carrier according to any one of claims 3 to 7 wherein the thermoplastic or storage layer contains an alkyl methacrylate polymer, characterized in that the thermoplastic storage layer also comprises chemically active derivatives of styrene and vinylnaphthalene, the molecular proportion of the components being  alkyl methacrylate 50 to 55 99  chemically derived  styrene assets 5 to 10 ffi  vinylnaphthalene 40 to 45%.  vinylnaphthalene 43 to 47%.  vinylphenylisocyanate S at 7%  octylmethacrylate 50 to 55%  13. Information carrier according to any one of claims 3 to 7, characterized in that the thermoplastic storage layer comprises vinylphenyl isocyanate, the molecular proportion of the components being:  An information carrier according to any one of claims 3 to 9, wherein the thermoplastic storage layer contains alkyl methacrylate polymer, characterized in that the thermoplastic memory layer also contains chemically active derivatives of styrene. and halogenated styrene the molecular proportion of the components being:  alkylimethacrylate 30 to 50%  chemically derived  styrene actives 5 to 15 0  halogenated styrene 35 to 65 °.  15. Information carrier according to any one of claims 3 to 9, characterized in that the thermoplastic storage layer contains vinylphenylisocyanate the molecular proportion of the components being  octylmethacrylate 30 to 50 '  vinylphenyl isocyanate 5-7;  halogenated styrene 35 to 63.  halogenated styrene 35 to 65%.  vinylphenylamine 5 to 15 fo  octylmethacrylate 30 to 50 O ', o  16. Information carrier according to any one of claims 3 to 9, characterized in that the thermoplastic storage layer contains vinylphenylamine, the molecular proportion of the components being  Information carrier according to one of Claims 3 to 9, characterized in that the thermoplastic memory layer contains vinylphenyl isothiocyanate, the molecular proportion of the components being  octylmethacrylate 30 to 35 0  vinylphenylisothiocyanate 5 to 10  halogenated styrene 35 to 60%.  18. Information carrier according to any one of claims 3 17, characterized in that it comprises a flexible substrate based on polyethylene terephthalate containing 0.05 to 0.5 parts by weight of 1,1-diacetyl-ferrocene.