JPH08278513A - Optical sensor for liquid crystal mdium recording - Google Patents

Abstract

PURPOSE: To make it possible to execute image recording with recording characteristics meeting purposes by specifying the value of a base current when a specific voltage is impressed on an optical sensor to a specific vague. CONSTITUTION: A liquid crystal recording medium 20 successively formed with transparent electrodes 22 and a high polymer-liquid crystal composite layer 23 on a transparent base 21 and the optical sensor 10 successively laminated with transparent electrodes 12 and a photoconductive layer 13 on a transparent support-base 11 are arranged to face each other via an air gap. The optical sensor 10 is subjected to image exposing in the state of impressing the voltage between both electrodes. The electric field acting on liquid crystals changes according to the exposing light intensity and the liquid crystals are oriented according to the electric field. The image information meeting the exposing light intensity is thus recorded. The base current at the time of impressing 100V on the optical sensor 10 is specified to 1×10<-7> to 2×10<-5> A/cm<2> . The optical sensor current of the exposed parts when impressed with the voltage under such a condition under which the optical sensor current of the unexposed parts attains 2×10<-6> to 4×10<-6> A/cm<2> is preferably 0.5×10<-6> to 1.5×10<-6> A/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor for recording a liquid crystal medium, and more particularly to an optical sensor for a base current which can cope with characteristics of an image to be recorded.

[0002]

2. Description of the Related Art A polymer-liquid crystal composite is formed, for example, by mixing a liquid crystal and a resin, dissolving them in a common solvent, coating the solution with a spinner or the like, and then evaporating and drying the solvent to form a liquid crystal phase. It is known that the resin phase can be produced by phase separation. As another method for producing a polymer-liquid crystal composite, a liquid crystal and a monomer or oligomer of an ultraviolet curable resin are dissolved in a common solvent, and the mixture of the liquid crystal and the monomer is dried at a temperature at which it becomes an isotropic phase, It can also be produced by subjecting a resin phase and a liquid crystal phase to phase separation by irradiating with ultraviolet rays and polymerizing a monomer.

The state of the phase separation of the liquid crystal phase and the resin phase is such that the liquid crystal phase having a spherical or other shape is dispersed in the resin,
There is a liquid crystal phase in which resin spheres are dispersed. The refractive index in the alignment direction of the liquid crystal phase is adjusted to be substantially equal to the refractive index of the resin. Since the refractive index in the non-aligned state is different from the refractive index of the resin, light is scattered at the interface between the liquid crystal phase and the resin in the non-aligned state immediately after manufacturing the liquid crystal medium, and the transmittance of the medium is lowered. When an electric field is applied to the liquid crystal medium to orient the liquid crystal in the direction perpendicular to the plane of the medium, light is transmitted without scattering.

When a smectic liquid crystal having a memory property is used as the liquid crystal, the alignment state is maintained even if the electric field is removed after the liquid crystal is aligned by applying an electric field. The orientation state is that after cooling by heating to a temperature at which the liquid crystal phase becomes an isotropic phase,
It can be returned to the non-oriented state.

As a method of recording image information on a liquid crystal medium, as shown in FIG. 1, a liquid crystal recording medium 20 in which a transparent electrode 22 and a polymer-liquid crystal composite layer 23 are sequentially formed on a transparent support 21. And a photosensor 10 in which a transparent electrode 12 and a photoconductive layer 13 are sequentially laminated on the transparent support 11 so as to face each other via an air gap, and a voltage is applied between both electrodes using a power supply 30. By performing image exposure on the optical sensor 10 by using, the electric field applied to the liquid crystal changes according to the exposure intensity, and by aligning the liquid crystal according to the electric field, image information corresponding to the image exposure can be recorded.

As another method of recording an image on a liquid crystal recording medium using an optical sensor, as shown in FIG. 2A, a transparent electrode 12, a photoconductive layer 13 and a polymer are formed on a transparent support 11. An integrated recording medium in which a liquid crystal composite layer 23 and an upper electrode 22 are sequentially laminated, or as shown in FIG. 2B, a transparent electrode 12, a photoconductive layer 13, and a dielectric intermediate layer on a transparent support 11. By using the integrated recording medium in which the layer 14, the polymer-liquid crystal composite layer 23, and the upper electrode 22 are sequentially laminated, the sensor is imagewise exposed in the same manner as described above, and a voltage is applied between the electrodes by the power source 30. Image information can be recorded on the liquid crystal layer.

The image information recorded on the liquid crystal medium can be converted into an electric signal by an image reading device as shown in FIG. In FIG. 3, the liquid crystal recording medium 20 is irradiated with illumination light having an appropriate wavelength selected by an optical system including a light source 40, an IR cut filter 41, a bandpass filter 42, and an illumination lens 43. The light transmitted through the liquid crystal medium is adjusted by the imaging lens 44 so as to form an image on the CCD line sensor 50. The liquid crystal recording medium is installed on a movable stage (not shown), which is controlled by a stepping motor, and the transmitted light is converted into an electric signal by a CCD sensor according to the movement of the stage to read image information. Be seen. The image signal converted into an electrical signal is
It is output to a CRT or printer as needed.

[0008]

When recording an image by the above method, depending on the characteristics of the optical sensor used,
The characteristics (latitude) of the recorded image change, and for example, when trying to record a wide exposure range, if the recording latitude is narrow, the desired range cannot be recorded and the highlights and shadows are crushed. There is a problem that ends up. On the contrary, when recording an image of a narrow exposure range such as character information, if the recording is performed under the condition that the wide exposure range can be recorded, there is a problem that the S / N of the portion to be recorded is lowered. As described above, if the photosensors having different recording characteristics are used for the purpose, it is impossible to obtain good image information satisfying the purpose. The present invention has been made in view of the above points, and an object of the present invention is to provide an optical sensor for recording a liquid crystal medium capable of recording an image with recording characteristics according to the purpose.

[0009]

According to the present invention, an optical sensor having a photoconductive layer formed on a transparent electrode and a liquid crystal recording medium having a polymer-liquid crystal complex formed of a liquid crystal and a resin on an electrode are provided with an air gap. In the optical sensor for recording the image information by aligning the liquid crystal by imagewise exposing the optical sensor of the separation-type information recording medium opposed to each other through the voltage application between both electrodes, the base when 100V is applied. Current is 1 × 10 ^-7
It is characterized in that it is ˜2 × 10 ⁻⁵ A / cm ² . Further, according to the present invention, the upper limit applied voltage V1 determined by the capacitance of the liquid crystal medium and the optical sensor, and the lower limit applied voltage V2 determined by the threshold voltage of the liquid crystal medium, the saturation voltage of the liquid crystal medium, the resistance of the liquid crystal medium, and the resistance of the optical sensor. Then, the film thickness and the base current satisfy V1> V2. Further, according to the present invention, the photosensor current ( _BD current) in the unexposed portion is 2 × 1 between the upper limit applied voltage V1 and the lower limit applied voltage V2.
There is an applied voltage condition of 0 ⁻⁶ to 4 × 10 ⁻⁶ A / cm ² , and the photosensor current ( _BL current) of the exposed portion when voltage is applied under such voltage application condition is 0.5
It is characterized in that it is x10 ^{-6 to} 1.5 x 10 ^-6 A / cm ² . Further, according to the present invention, the photosensor current ( _BD current) in the unexposed portion is 2 × 10 ⁻⁶ to 4 × 10 ⁻⁶ A / cm ² between the upper limit applied voltage V1 and the lower limit applied voltage V2. It is characterized in that there are various applied voltage conditions, and the photosensor current (B _L current) in the exposed portion when a voltage is applied under this voltage application condition is larger than 1.5 × 10 ⁻⁶ A / cm ² .

[0010]

The present invention focuses on the fact that the image recording characteristic changes due to the difference in the base current of the optical sensor, and simulates the time change of the voltage applied to the optical sensor to determine the optimum base current light according to the purpose. It is possible to select a sensor and perform image recording with characteristics according to the purpose.

[0011]

EXAMPLE An image recording method using the photosensor of the present invention will be described below with reference to the drawings. 4 to 6 show the results of measuring the current during light irradiation by changing the voltage for the photosensors A to C having different base current values. The horizontal axis of the figure shows the exposure intensity (logarithmic display), and the vertical axis shows the total current (A / cm ² ) of the base current and the photocurrent. The current flowing through the optical sensor can be measured, for example, by forming a gold electrode 15 on the surface of the optical sensor as shown in FIG. 7 and applying a voltage between the gold electrode 15 and the transparent electrode 12 by the power supply 30. In this case, the measurement result obtained when the light source 51 and the optical shutter 52 radiate light of constant intensity for a certain period of time from the transparent electrode side of the optical sensor is as shown in FIG. The photosensor was irradiated with light for 33 msec while a constant voltage was applied. The time on the horizontal axis of the graph is t = 0 when the light irradiation is started.
And Further, the current at t = 0 is a dark current (base current) value, and the current value in the graph is a value per unit area (1 cm ² ). After the light irradiation is started, the current value increases with time during the light irradiation, and gradually decreases after the light irradiation is completed. As described above, the photocurrent constantly changes during the voltage application, but when the light irradiation time is 33 msec, the photocurrent becomes maximum after 33 msec and is gradually attenuated after the light irradiation is completed. Thus, the photocurrent is constantly changing and not constant,
Hereinafter, the value of the photocurrent at t = 33 msec (when the voltage application is stopped) is referred to as the photocurrent value. The photocurrent depends on the intensity of the applied light and increases as the intensity increases.

9 to 11 show the results of simulating the voltage applied to the liquid crystal medium when the optical sensors A to C are used. FIG. 9 shows the result of simulation for the optical sensor A. A characteristic L1 shows a voltage change applied to the liquid crystal medium during light irradiation, and a characteristic L2 shows a time change of the voltage of the liquid crystal medium in an unexposed portion. Similarly, the characteristic M
Reference numerals 1 and M2 respectively show changes with time in voltage applied to the photosensor during exposure and during non-exposure. Since the voltage application is stopped at the moment when the voltage of the liquid crystal medium in the unexposed portion reaches the threshold voltage, in the simulation, when the voltage of the liquid crystal medium in the unexposed portion is 200V, the voltage of the liquid crystal medium in the exposed portion becomes 240V. The exposure amount is adjusted so that

Similarly, FIGS. 10 and 11 show simulation results for the optical sensors B and C, respectively. The simulation results of FIGS. 9 to 11 are summarized in Table 1. S: Photosensor A, B, C B current: Base current when 100V is applied to the photosensor (A / cm ² ) (constant value for each photosensor) Applied voltage: Applied between the photosensor and the electrode of the liquid crystal medium Voltage (V) S _D voltage: voltage applied to the photosensor during non-exposure (V) S _L voltage: voltage applied to the photosensor during exposure (V) B _L current: base current at voltage S _L (A / cm ² ) The behavior of each layer of the optical sensor and the liquid crystal medium is expressed by the following equation. I _PS + C _PS (dV _PS / dt) = V _LC / R _LC + d (CV) _LC / dt (1) C _LC ∝1 / d (2) V _LC ∝d ... (3) R _LC ∝d ... (4) The left side of the equation (1) shows the current of the photosensor layer, and the right side shows the current of the liquid crystal layer. To align the liquid crystal,
When the applied voltage is stopped, it is necessary for the optical sensor to supply the current value represented by the right side of the equation (1). Since the capacitance of the liquid crystal medium is inversely proportional to the film thickness (equation (2)), the saturation voltage is proportional to the film thickness (equation (3)), and the resistance is proportional to the film thickness (equation (4)), the film of the liquid crystal medium is Even if the thickness changes, the current value on the right side of the equation (1) does not change. Therefore, in order to align the liquid crystal and perform image recording, it is necessary to supply a similar current to the liquid crystal medium of any thickness from the optical sensor.

In general, the capacity of the optical sensor is not large and the amount of change in voltage is not large as compared with the liquid crystal medium.
The left side of the equation largely depends on the current value I _PS of the optical sensor.
I _PS is the sum of the base current and the photocurrent, but the photocurrent depends on the base current.

From the equation (1), in order to make the orientation of the liquid crystal medium the same, it is necessary to equalize the currents of the photosensors in the unexposed portion when the voltage application is stopped. Therefore, the simulation shows the applied voltage. Adjusted as 1. In this case, the resistivity of the liquid crystal medium is 2 × as the photosensor current value ( _BD current) of the unexposed portion obtained from the equation (1).
When 10 ¹¹ Ωcm, 2 × 10 ⁻⁶ to 4 × 10 ⁻⁶ A / c
The condition of m ² is suitable for image recording. Here, suppose B
_{The case where the D} current is 2 × 10 ⁻⁶ A / cm ² will be described as an example.

In the present invention, it is assumed that a discharge breakdown voltage is applied to the air gap layer of about 400V, and a voltage obtained by subtracting 400V from the applied voltage is distributed to the liquid crystal medium and the photosensor. For example, the optical sensor A in Table 1
, The optical sensor current ( _BD current) is 2 × 10 ⁻⁶ A
The S _D voltage that is equal to / cm ² is 70 V, and therefore the applied voltage is: applied voltage = 70 + 200 + 400 = 670 (V) and S _L voltage = 670-400-240 = 30 (V). The value of the base current B _L indicates the value of the base current that flows when the voltage of the photosensor obtained in this way is S _L. The current value when a voltage of 30 V is applied to the sensor is shown. Similarly, the optical sensors B and C were obtained and Table 1 was prepared.

Returning to FIGS. 4 to 6, for example,
Assuming that the current value of the photosensor required to completely orient the liquid crystal medium is 4 × 10 ⁻⁶ A / cm ² (see FIG. 4).
(Values indicated by broken lines in FIG. 6), in the optical sensor A (FIG. 4),
It can be seen from Table 1 that the photosensor voltage during exposure is 30 V, and therefore the exposure intensity is 100 lux as the intersection of the characteristic curve corresponding to this voltage and the broken line. Also, the optical sensor B
In Fig. 5, from Table 1, the optical sensor voltage during exposure is 80V.
Therefore, the exposure intensity of 50 lux is the intersection of the characteristic curve corresponding to this voltage and the broken line, and in the optical sensor C (FIG. 6), from Table 1, the optical sensor voltage at the time of exposure is 310 V, so it corresponds to this voltage. 1 as the intersection of the characteristic curve and the broken line
It can be seen that the exposure intensity is 5 lux. in this way,
Since the photosensors having different base currents (B currents) have different exposure amounts for generating the same photosensor current, the characteristics (latitude) of the image to be recorded can be changed by changing the base current of the photosensors. You can That is, the optical sensor A can obtain an image with a wide exposure range (soft contrast), and the optical sensor C can obtain an image with a relatively narrow exposure range (hard contrast).

The photocurrent of the photosensor (current flowing upon exposure) depends on the base current. The larger the base current, the larger the photocurrent, and the larger the total current with the base current. As a method of changing the base current of the photosensor, there is a method of changing the film thickness of the photosensor. Since the charge generation layer of the optical sensor is extremely thin, the thickness of the charge transport layer is actually changed. FIG. 12 shows the relationship between the base current and the applied voltage when the thickness of the charge transport layer of the photosensor is changed within the range of 4.5 to 21 μm. In the figure, ○ is 4.5 μm, ● is 8 μm, □ is 12 μm, and ■ is 21 μm.
Is the case. As shown in the figure, the base current decreases as the thickness of the charge transport layer increases. Also, for example,
Optical sensor 1 (for example, optical sensor A in FIG. 4), optical sensor 2
13 (for example, the optical sensor C in FIG. 6), if a voltage is selected so that the exposure intensity-current characteristics are substantially the same as in FIG.
The relationship as shown in (a) is obtained. That is, if the applied voltage is set so that the base currents become equal, the photocurrent with respect to the exposure intensity becomes the same. Therefore, the relationship between the applied voltage and the base current as shown in FIG. If the characteristics shown in FIGS. 4 to 6 are measured for one photosensor, the exposure intensity-current characteristics of the photosensors having different base currents can be obtained.

Note that when different photosensors, for example, different charge generating substances and charge transporting agents, the photocurrents are compared by changing the light amount under a voltage condition such that the base currents are the same. ), The photocurrent value may be different. Even in this case, when the logarithm of the photocurrent is plotted against the logarithm of the exposure intensity (exposure amount), it becomes a parallel translation form as shown in the figure. The difference between these two photosensors is the difference in sensitivity and the latitude. The (image characteristic) can be controlled by selecting the B current (base current when 100 V is applied) of the photosensor, as in the methods described above.

As a method of changing the base current of the photosensor, a method of changing the resistance value by using a charge transport material of the charge transport layer, for example, a charge transport agent having a different mobility, and a charge transport of the charge transport layer are used. A method of changing the resistance value by changing the mixing ratio of the agent and the binder resin, changing the binder of the charge generation layer or the film thickness of the charge generation layer, adding an additive to the charge generation layer, or a mixing ratio of the additives. May be changed to change the barrier of charge injection, or by combining these, the value of the base current of the photosensor can be changed.

The relationship between the base current of the photosensor and the gradation characteristic will be described in more detail. In the system of the present invention,
The applied voltage during image recording is set by the threshold voltage of the liquid crystal medium, the saturation voltage, the resistance value of the liquid crystal medium, and the base current value of the optical sensor. First, the threshold voltage and the saturation voltage related to setting the applied voltage will be described. FIG. 14 shows an apparatus for measuring the alignment state (transmittance) of the liquid crystal by changing the voltage applied to the liquid crystal medium. A gold electrode (semitransparent) 24 is attached to the surface of the liquid crystal medium, and a voltage generator 5 is provided between the transparent electrode 22 and the gold electrode 24.
Voltage is applied at 1 and argon laser (488 nm) 40
Laser light is emitted from the sensor and transmitted light is detected by the sensor 50,
The detection result was monitored using the oscilloscope 52. The measurement result is as shown in FIG. In FIG.
The horizontal axis represents voltage and the vertical axis represents modulation factor, which is defined by the following equation. Modulation Degree = (T-Toff) / (Ton-Toff) Ton: Signal value in oriented state Toff: Signal value in non-oriented state In this way, when the measurement result is normalized, the modulation degree is 0.
The voltage V _th of the liquid crystal medium when it becomes 1 is the threshold voltage, and the voltage V _{LC (sa)} of the liquid crystal medium when the degree of modulation is 0.9 is the saturation voltage.

Next, the method of setting the applied voltage will be described by taking as an example the separation type medium (the one in which the optical sensor and the liquid crystal medium are opposed to each other with a gap) which is the simplest system of the system of the present invention. . The upper and lower limits of the applied voltage of the system of the present invention are set as follows, and an appropriate voltage within that range is applied to perform image recording.

(A) Setting of lower limit of applied voltage The lower limit of the applied voltage is a voltage whichever is higher of the following two conditions. [Condition: Sum of saturation voltage and discharge breakdown voltage] For example,
If the discharge breakdown voltage is 400V and the saturation voltage is 250V, the lower limit applied voltage is 650V. In order for the liquid crystal medium to reach the saturation voltage and be completely aligned, the voltage of the photosensor is not zero or less at this time, and therefore it is necessary to apply at least a voltage obtained by adding the saturation voltage and the discharge breakdown voltage. That is, when the voltage applied to the optical sensor is zero, no current flows, so it is necessary to apply a voltage higher than this.

[Condition: minimum voltage required for the voltage of the liquid crystal medium in the unexposed portion to reach the threshold voltage] With the photosensor and the liquid crystal medium facing each other with an air gap in between, When a voltage is applied between both electrodes at the place,
When a sufficient time has elapsed, the current value of the photosensor and the current value of the liquid crystal medium become equal, and the equilibrium state in which the voltage does not change is reached. When the voltages of the optical sensor and the liquid crystal medium at this time are respectively V _{LC (eq)} and V _{PS (eq)} , the following equation holds.

V _{PS (eq)} / R _PS = V _{LC (eq)} / R _LC (5) V _{PS (eq)} + V _{LC (eq)} = V _AP −V _AIR (6) Image by the system of the present invention In order to perform recording, the voltage of the liquid crystal medium needs to be higher than the threshold voltage in the equilibrium state. _{That, V LC (eq) = V} AP -V AIR -V PS (eq) ≧ V th V AP ≧ V th + V AIR + V PS (eq) ... (7) Therefore, the threshold voltage of the liquid crystal medium, the resistance value If the current-voltage characteristics of the optical sensor are known in advance,
The lower limit of the applied voltage can be obtained from the equations (5) to (7).

(B) Setting of Upper Limit of Applied Voltage In the system of the present invention, a voltage corresponding to each capacitance is distributed to each layer of the liquid crystal medium and the photosensor within a short time of several milliseconds after the voltage is applied. V _LC (0) = (V _AP −V _AIR ) · C _PS / (C _LC + C _PS ) ... (8) In order to be able to record an image, the voltage V _LC initially distributed.
It is necessary that (0) is equal to or lower than the threshold voltage, preferably about 1/2 or less of the threshold voltage. _{That, (V AP -V AIR) ·} C PS / (C LC + C PS) ≦ V th / 2 V AP ≦ (V th / 2) {(C LC + C PS) / C PS} + V AIR ... (9) Becomes Since the voltage initially distributed to the liquid crystal medium is expressed by the equation (8), it is determined by the capacities of the liquid crystal medium and the optical sensor, that is, the film thickness and the threshold voltage, and the upper limit of the applied voltage is set by the equation (9). be able to.

Incidentally, these physical property values (voltage of the optical sensor-
The current characteristics, the resistance of the liquid crystal medium, and the capacitance) may be measured at the time of actual image recording by preparing a measuring device inside the recording device.

In this way, when the applied voltage is set within the upper and lower limits, the image characteristics to be recorded differ depending on the value of the base current (B current) of the photosensor. In the system of the present invention, the applied voltage is stopped at the timing when the voltage of the liquid crystal medium corresponding to the unexposed portion reaches the threshold voltage and the liquid crystal medium starts alignment. When image recording is performed using optical sensors having different B currents, the applied voltage is set to each optical sensor so as to satisfy the above conditions. At this time,
The applied voltage is adjusted so that the base currents of the photosensors in the unexposed portion are almost equal when the applied voltage is stopped. This adjustment is to make the rise of the alignment of the liquid crystal the same. When the applied voltage is adjusted in this manner, the applied voltage is low for the photosensor having a large B current, and the applied voltage is high for the photosensor having a small B current.

In the system of the present invention, in order to record an image in a desired exposure range, the applied voltage is set so that the current value of the photosensor when the applied voltage is stopped becomes a predetermined value. The good thing is that the applied voltage depends on the base current value of the photosensor, the threshold value of the liquid crystal medium,
The voltage is set based on the resistance, and the voltage thus set is not always suitable for recording a desired exposure range.

For example, when an attempt is made to obtain a photocurrent value of 4 × 10 ^-6 A / cm ² for an exposure intensity of 100 lux, the photosensor A is 30 V, and the photosensors B and C are It suffices if the voltages of 60 V and 240 V are applied to the optical sensor, respectively. However, for an appropriate applied voltage (set based on the threshold value and resistance of the liquid crystal medium), such a voltage is applied to the optical sensor. It does not always mean that

As described above, the applied voltage is such that the photosensor current value ( _BD current) in the unexposed portion when the voltage of the liquid crystal medium in the unexposed portion reaches the threshold voltage is 2 × 10 ^-6 . 4x
The applied voltage condition is preferably 10 ⁻⁶ A / cm ² . This value does not change so much even if the resistivity of the liquid crystal medium increases, but it changes when the resistivity of the liquid crystal medium decreases. However, even in that case, the range of the B _D current may be set by correcting that amount. Further, the _BD current does not change with the change in the film thickness of the liquid crystal medium.

An optical sensor suitable for photographing a landscape image, a portrait image, etc., can be used when such an applied voltage is set.
When the applied voltage is stopped, that is, when the voltage of the liquid crystal medium in the unexposed portion reaches the threshold voltage, the voltage of the photosensor corresponding to the saturation voltage portion (voltage S _L ) is Base current component of sensor is 1 × 10 ^-6 A / cm
^The optical sensor is about ² and has a density of 0.5 to 1.5 × 10 ⁻⁶ A / cm ² .

This will be schematically described with reference to FIG. In the figure, the horizontal axis is the voltage, and the vertical axis is the base current component. For three types of photosensors with different B currents a, b, and c (B current is a>b> c), the applied voltage is Is set as follows. For example, in the optical sensor b, if the voltage at which the base current value is 2.0 × 10 ⁻⁶ A / cm ² is S _D (S _D ″ in the optical sensor a, S _D ′ in the optical sensor c), The threshold voltage of the liquid crystal medium used at this time is V
_{When th} , the applied voltage is set as in the following equation, considering that the equation (7) is derived.

V _AP = S _D + V _th + V _AIR (10) The voltages of the liquid crystal medium and each layer of the photosensor in the unexposed portion when the voltage application is stopped are V _th and S _D , respectively, and at this time, the voltage of the liquid crystal medium Is S _L (S _L ″ for photo sensor a, S _L ′ for photo sensor c ₎ corresponding to the saturation voltage V _{LC (sa)} portion, S _L = V _AP −V _AIR −V _{LC (sa)} That is, S _L = S _D − (V _{LC (sa)} −V _th ) ... (11) Difference between saturation voltage and threshold voltage of liquid crystal medium V _{LC (sa)} −V _th
Since is a constant value regardless of the optical sensor, an _{S L -S D = S L '} -S D' = S L "-S D" = constant, as the B current is large as shown in FIG, S _L percentage decreases for the _{S D, S L, S L} ', the base current component of the S _L "is small.

As shown so far, the current value (the total of the base current and the photocurrent) required for aligning the liquid crystal medium is almost the same regardless of the film thickness, and if the base current component is small, the photocurrent component is large. Therefore, it is necessary to increase the exposure intensity. Therefore, a, b, c in the figure
It is necessary to irradiate extra light in the order of. In order to record an image in an appropriate exposure range, the base current with respect to the S _L voltage is in an appropriate range, 0.5 to 1.5 × 10 ⁻⁶ A / cm ^2.
It must be of the order of magnitude, which also limits the value of the base current of the photosensor.

17 and 18 show a liquid crystal medium
It shows a method of limiting the optical sensor of the base current suitable for image recording. FIG. 17A shows a film thickness of the liquid crystal medium of 6 μm (threshold voltage 200 V, saturation voltage 250
V) and the film thickness of the optical sensor of 10 μm,
This is the result of calculating the appropriate value of the applied voltage when the B current (when 100 V is applied) of the photosensor was changed (here, the calculation was performed assuming that the current value of the photosensor is proportional to the voltage). ). In the figure, ◯ is the lower limit of the applied voltage calculated from the resistance of the liquid crystal medium and the threshold voltage according to the equation (7). Further, since the lower limit of the applied voltage calculated from the saturation voltage is 650V (broken line in the figure), it is necessary to set the applied voltage to a voltage higher than the voltage of ◯ or 650V, whichever is higher.

The upper limit of the applied voltage is preferably such that the initial voltage applied to the liquid crystal medium is not more than half the threshold voltage, and in FIG. 17A, the upper limit of the applied voltage is 820V. (Broken line in the figure). In FIG. 17 (a), in the photosensor with B current of 7 to 8 × 10 ⁻⁷ A / cm ² or less, ○ (lower limit voltage) exceeds 820 V (upper limit voltage), and an appropriate applied voltage is set. I can't
Such an optical sensor cannot be used. Also,
If the B current is too large, the applied voltage will be lower than 650 V (lower limit voltage), so that it cannot be used. Also, in FIG. 17A, ● and ◆ indicate that the base current ( _BD current) of the photosensor in the unexposed portion when the voltage of the liquid crystal medium reaches the threshold voltage is 2 × 10, respectively. ^-6 A / cm ² , 4 × 10 ^-6 A / cm ^{2 under} applied voltage conditions.
It is desirable to adjust the applied voltage so that it is between the and ◆, and a part of such applied voltage condition is included in the range limited by the upper limit voltage and the lower limit voltage. Can be used for Therefore, in the method of specifying the range of the base current of such an optical sensor, the upper limit of the base current is the intersection of ♦ and the lower limit applied voltage, which is about 1.0 × 10 ⁻⁵ A / cm ² . Further, the lower limit of the base current is the intersection point of the ● and the upper applied voltage, and is about 8.0 × 1.
It is 0 ⁻⁷ A / cm ² . That is, the B current is 8.0 × 1
An optical sensor of 0 ⁻⁷ A / cm ^{2 to} 1.0 × 10 ⁻⁵ A / cm ² is suitable.

FIG. 17B shows that when the image recording is performed under the voltage application conditions shown in FIG.
It is a plot of the relationship between the voltage (S _L voltage) applied to the photosensor in the exposed portion and the B current. In FIG. 17B, ◯ indicates the lower limit of the applied voltage (condition that the equilibrium voltage becomes equal to the threshold voltage), and ● and ◆ indicate _BD current of 2 × 10, respectively.
⁶ is a result of calculation in the case of applying a voltage under an applied voltage condition of ⁻⁶ A / cm ² , 4 × 10 ⁻⁶ A / cm ² . In an optical sensor with a large base current, the S _L voltage has a negative value, but this does not actually occur.

FIG. 18 is a plot of the photosensor current (B _L current) corresponding to the S _L voltage shown in FIG. 17B. In this system, an optical sensor suitable for photographing a subject such as a landscape image or a portrait image with an appropriate latitude has a _BL current of about 0.5 to 1.5 × 10 ⁻⁶ A / cm ^2.
An optical sensor (hatched area in the figure) is suitable. From FIG. 18, it can be seen that the optical sensors satisfying such conditions are indicated by ● and 1.5.
× 10 ^-6 intersection of the A / cm ^2, ◆ and 0.5 × 10 ^-6 A /
B current is 7 × 10 ⁻⁷ to 8 obtained from the intersection with cm ^2.
It is an optical sensor of × 10 ⁻⁶ A / cm ² (range indicated by an arrow in the figure). Further, the optical sensor needs to satisfy the conditions shown in FIG. 17, and as an optical sensor suitable for recording a landscape image, a B current satisfying both conditions is 8.0 × 10 ⁻⁷ A.
It can be said that it is an optical sensor of / cm ² to 8 × 10 ^-6 A / cm ² .

Next, the case where the film thickness of the liquid crystal medium or the optical sensor is changed will be described. When the film thickness of the optical sensor or the liquid crystal medium changes, the capacitance of each layer and the threshold voltage of the liquid crystal medium change, so that the upper limit of the applied voltage changes. FIG.
Shows the relationship between the upper limit of the applied voltage and the upper limit of the applied voltage when the film thickness of the optical sensor was changed for the cases where the film thickness of the liquid crystal medium was 6 μm (◯) and 9 μm (). The thickness of the optical sensor is 10μ
m, 15 μm, and 20 μm, the upper limit of the applied voltage is approximately 850 V, 1010 V, and 1200 V. The thicker the film thickness of the optical sensor, the higher the upper limit voltage of the applied voltage becomes. The range of base current is widened. The lower limit of the applied voltage is determined by the threshold value of the liquid crystal and the saturation voltage, and these values depend on the film thickness of the liquid crystal and not the film thickness of the optical sensor.

Next, FIGS. 20 and 21 show the appropriate value of the applied voltage and the range of the base current of the photosensor suitable for image recording when the film thickness of the liquid crystal medium is 9 μm. FIG. 20A shows the relationship between the B current and the applied voltage of the optical sensor. FIG. 17
Similar to (a), ○, ●, and ◆ represent the lower limit voltage of the applied voltage and the _BD current of 2 × 10 ⁻⁶ A / cm ² , 4 × 1 respectively.
The applied voltage conditions at 0 ⁻⁶ A / cm ² are shown, and the lower limit of the applied voltage is 780 V which is the discharge breakdown voltage saturation voltage, whichever is larger. The upper limit of the applied voltage depends on the film thickness of the photosensor (film thickness of the charge transport layer), and as the film thickness of the photosensor increases, the upper limit voltage also increases (at film thicknesses of 20 μm, 15 μm, and 10 μm, respectively). 1200V, 1010V, 870V), the range of the base current of the photosensor that can be used is determined from the intersection of the upper limit of ◆ and 780V, the lower limit of the intersection of ● and each upper voltage, and the range of B current is the lower current together with the upper limit voltage. Spread to the side. The upper limit of the B current is 6 × 10 ⁻⁶ A / cm regardless of the film thickness of the optical sensor.
² Similarly, FIG. 20B shows the value of the S _L voltage under these voltage application conditions.

FIG. 21 is a plot of the relationship between the base current (B _L current) and the B current with respect to the S _L voltage shown in FIG. 20 (b). As in the case of FIG. 18, the appropriate value of the _BL current for a landscape image or the like is 0.5 to 1.5 × 10.
^{Since it is −6} A / cm ² , the range of the base current of such an optical sensor is the intersection of ● and 1.5 × 10 ⁻⁶ A / cm ^2, and ◆ and 0.5 × 10 ⁻⁶ AA / cm ^2. It is an optical sensor having a B current of 4 × 10 ^{−7 to} 5 × 10 ⁻⁶ A / cm ² (range indicated by an arrow in the figure), which is obtained from the intersection with cm ² .

An optical sensor suitable for this system is an optical sensor which simultaneously satisfies the conditions of FIGS. 20 and 21, and for example,
When the film thickness of the optical sensor is 15 μm, the B current is 6 × 1
It is an optical sensor of 0 ^{−7 to} 5 × 10 ⁻⁶ A / cm ² . If the film thickness of the optical sensor is about 20 μm, 4 × 10 ⁻⁷ A / cm
² optical sensors can also be used.

An optical sensor that simultaneously satisfies the conditions thus obtained is suitable for image recording. in this way,
An optical sensor that can be used for image recording can be manufactured by designing a film thickness of the optical sensor suitable for the characteristics of the liquid crystal medium not only from the base current value but also from the relationship between the film thickness of the optical sensor and the B current. . Here, the change in film thickness of the photosensor will be described. The relationship between the voltage and the base current when only the film thickness of the charge transport layer is changed with the same composition of the photosensor (charge generation material, charge transport material, etc.) As shown in 12. In general, when the film thickness of the photosensor (film thickness of the charge transport layer) is changed, the base current of the photosensor decreases according to the film thickness change. For example, when the thickness of the liquid crystal medium is 6 μm and the thickness of the optical sensor is 10 μm, the B current is 2 × 10 ⁻⁶ A / cm 2.
The optical sensor No. ² can be used to satisfy the conditions shown in FIGS. 17 and 18. However, for a liquid crystal medium of 9 μm, the condition of FIG. 21 is not satisfied, and thus it cannot be said to be a suitable optical sensor. In this way, for example, when the film thickness of the liquid crystal medium becomes thick, the range of the suitable B current shifts to the low current side, so that it may not be possible to use even the same optical sensor. In such a case, by increasing the film thickness of the optical sensor, the B current of the optical sensor decreases, and the condition shown in FIG. 21 can be satisfied. In FIG. 20, the usable condition of the optical sensor is low. Since it spreads to the current side (the upper limit of the applied voltage increases), it is possible to manufacture an optical sensor that satisfies these two conditions. In this way, the film thickness of the optical sensor suitable for the characteristics of the liquid crystal medium can be designed and manufactured from the relationship between the film thickness of the optical sensor and the B current.

By selecting an optical sensor suitable for image recording (landscape, person, etc.) by the method described above,
A good image can be recorded. Further, in the case of recording information such as characters which does not require gradation, an optical sensor larger than the above B _L current range of 0.5 to 1.5 A / cm ² (small in terms of B current), That is, by using an optical sensor having a B _L current of more than 1.5 A / cm ^2, it is possible to record good S / N information.

[Image Reading Method] The outline of the reading device will be described with reference to FIGS. 22 and 23. FIG. 22 shows an image reading apparatus for a transmissive liquid crystal medium.
An optical system portion including a cut filter 41, a bandpass filter 42, an illumination lens 43, and an imaging lens 44, a sensor portion 50 for converting a change in transmittance of the medium into an electric signal, and a stage portion (not shown) for moving the liquid crystal medium. No)). From the spectral transmittance characteristics of the liquid crystal medium, it is possible to obtain a good image signal by using the reading light having an appropriate wavelength. Therefore, as the light source, a white light source such as a xenon lamp, a mercury lamp, a halogen lamp, a tungsten lamp or a laser beam can be used, but the blue and ultraviolet light components are strong and close to a point light source, so the xenon lamp is used as a light source. It is desirable to do. As such a light source,
L2274 xenon lamp manufactured by Hamamatsu Photonics KK can be used. The bandpass filter is used to emit light of a specific wavelength and has a central wavelength of 340 nm to 550 n.
m, and the half width of 10 to 40 nm can be used. As such a filter, 40 manufactured by Andover
0FS-25-50 (center wavelength 400 nm, half width 25)
nm) makes it possible to obtain a good image. A normal scanner lens can be used as the imaging lens, but when ultraviolet light is used as the reading light, it is desirable to use the ultraviolet light lens. As such a lens, there is UV Nicole 105 mm, F4.5 manufactured by Nikon Corporation. A CCD line sensor can be used as the sensor 50, and a pixel size of about 7 × 7 μm / pixel and a size of about 5000 pixels / 6 lines can be used. The liquid crystal medium is installed on a stage (not shown) that is movable in one axis direction, and a stepping motor is used to convert an electric signal for each line every time it moves a distance corresponding to one pixel on the medium. While reading.

FIG. 23 shows an image reading apparatus for a reflection type liquid crystal medium. An optical system is installed using a half mirror 45 as shown in FIG.
The optical system is adjusted so as to form an image at. in this way,
When reading with reflected light, it is necessary to form a reflective layer on a part of the recording medium. In the figure, A1 is formed on the electrode layer of the liquid crystal medium.
The case where the vapor-deposited film was used as both the electrode and the reflective layer was shown. Besides, a dielectric mirror layer may be separately provided.

[Image Recording Method] Next, an image recording method will be described. As shown in FIG. 24, in a state where the photosensor 10 and the liquid crystal recording medium 20 are opposed to each other with an air gap of about 10 μm, the gray scale 60 is projected and exposed on the charge generation layer of the photosensor for 33 msec, and both electrodes are exposed. After applying a voltage of 720 V for 45 msec, the optical sensor and the liquid crystal recording medium were separated from each other, and the liquid crystal medium was observed. As a result, it was confirmed that the transmittance of the liquid crystal medium was changed according to the grayscale transmittance. . The gray scale of the integrated medium was projected for 33 msec in the same manner as above, and after applying a voltage of 400 V and 40 msec between both electrodes, the medium was observed. Similarly, the transmission of the integrated medium was determined according to the transmittance of the gray scale. It was confirmed that the rate was changing.

[Method 1 for producing optical sensor] Fluorenone azo pigment 3 having the following structure [Chemical formula 1] as a charge generating substance
Parts and 1 part of polyester resin were mixed with 196 parts of a mixed solvent of dioxane: cyclohexane = 1: 1, and sufficiently kneaded with a mixer to prepare a coating liquid.

[0050]

Embedded image

This solution was applied to an ITO transparent electrode (film thickness of about 500).
Å, resistance; 80Ω / □) is applied thinly on the ITO side surface of the glass substrate and dried at 100 ° C for 1 hour to give a film thickness of 0.3μ
m charge generating layer was formed. Next, as a charge-transporting substance, 3 parts of parazylmethylstilbene having the following structure [Chemical formula 2] and 1 part of a polystyrene resin were added to dichloromethane:
170 parts of a mixed solvent of 1,1,2-trichloroethane = 68: 102 was mixed and dissolved to prepare a coating liquid. This solution was applied on the charge generation layer and dried at 80 ° C. for 2 hours to form a charge transport layer having a film thickness of 10 μm.

[0052]

Embedded image

[Manufacturing Method 2 of Optical Sensor] An IT film having a thickness of 100 nm is formed on a glass substrate having a thickness of 1.1 mm that has been thoroughly washed.
An O film was formed by sputtering to obtain an electrode layer. 3 parts by weight of a bisazo pigment (DPDD-3: manufactured by Dainichiseika Kogyo KK) having the following structure [Chemical Formula 3] as a charge generating agent on the electrode, 1 part by weight of polyvinyl butyral 1,4-
98 parts by weight of dioxane and 98 parts by weight of cyclohexane were mixed and dispersed for 6 hours with a paint shaker to obtain a coating solution, which was then dried at 100 ° C. for 1 hour to laminate a charge generation layer having a film thickness of 300 nm.

[0054]

Embedded image

On this charge generation layer, as a charge transfer agent,
3 parts by weight of a compound having the following structure [Chemical Formula 4] (DPDT-3: manufactured by Dainichiseika Kogyo Co., Ltd.), 2 parts by weight of polystyrene resin (HRM-3 manufactured by Denki Kagaku Kogyo Co., Ltd.), 1, 1 , 2-
A coating solution prepared by mixing 22 parts by weight of trichloroethane and 14 parts by weight of dichloromethane was spun at 400 rpm,
After coating for 0.4 seconds, the coating is dried at 80 ° C. for 2 hours to stack a charge transport layer, and a photosensor of the present invention having a 20 μm-thick photoconductive layer including a charge generation layer and a charge transport layer is obtained. It was

[0056]

[Chemical 4]

[Production of Integrated Medium] An optical sensor is formed on the transparent electrode by the same method as the optical sensor manufacturing method 2. Polyvinyl alcohol (AH-26: Nippon Synthetic Chemical Industry Co., Ltd.)
A solution in which 5% by weight of pure water was dissolved in pure water was applied onto the charge transport layer of the photosensor using a spinner and dried at 80 ° C. for 1 hour to give a film having a thickness of 1.3 μm. An intermediate layer was formed. A liquid crystal recording layer having a thickness of 6 μm was formed on the intermediate layer, and an ITO electrode was formed on the liquid crystal recording layer by a sputtering method in the same manner as the method for producing the liquid crystal recording medium, to produce an integrated medium.

[Method for producing liquid crystal recording medium] 4 parts of dipentaerythritol hexaacrylate, smectic liquid crystal S
6 (trade name; manufactured by Merck) 6 parts, fluorine-based activator Florard FC-430 (trade name; manufactured by 3M Company) 0.2 part, photopolymerization initiator “Darocur 1173” (trade name; manufactured by Merck) 0 .2 parts of the mixture was adjusted to 30% solids with xylene. This solution was applied to an ITO transparent electrode (film thickness about 500Å,
Resistance; 80 Ω / □) is applied to the surface of the glass substrate having ITO with a gap thickness of 50 μm with a blade coater, and this is held at 50 ° C. and irradiated with UV light of 0.3 J / cm ² , An information recording medium having an information recording layer having a film thickness of about 6 μm was produced. A liquid crystal was extracted from the cross section of the information recording medium using hot methanol and dried, and then a scanning electron microscope (manufactured by Hitachi, Ltd., S-800, 10000).
When observing the internal structure, the surface of the layer is 0.6μ.
The inside of the layer is covered with a UV curable resin having a thickness of m.
It was found to have a structure in which resin particles of 1 μm were filled. A cross section of this liquid crystal recording medium is schematically shown in FIG.
Shown in In the figure, 21 is a glass substrate, 22 is an ITO transparent electrode, and 23 is a liquid crystal recording layer. The surface of the liquid crystal recording layer is covered with the skin layer 23-a, which serves to prevent the liquid crystal from seeping out from the surface. The inside of the liquid crystal layer is filled with polymer balls 23-b, and the space between them is filled with a liquid crystal phase 23-c.

[Specific Example] Image recording (gray scale) for three types of optical sensors D, E, and F having different base currents
FIG. 26 shows the result of plotting the relationship between each step of gray scale and the read signal by the dedicated image reading device. The base current value and voltage application condition of each photosensor are as follows. The image of optical sensor D (large resistance) has an exposure range of about 1.0.
It is narrow and is not suitable for recording landscape images, etc., but is suitable for recording characters and the like. The image of the optical sensor E has an exposure range of 2.
It is as wide as 0 or more, and the liquid crystal medium is almost completely aligned in the high-exposure region, so that a reproduced image with a good S / N can be obtained. The optical sensor F (low resistance) cannot be said to be suitable for image recording because the liquid crystal is only incompletely aligned even in the high exposure area.

[0060]

As described above, according to the present invention, by selecting the base current value of the optical sensor, it becomes possible to perform image recording with the characteristics according to the purpose.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of recording an image on a separation type liquid crystal medium.

FIG. 2 is a diagram illustrating an image recording method on an integrated liquid crystal medium.

FIG. 3 is a diagram illustrating an image reading method.

FIG. 4 is a diagram showing a photosensor current measurement result when a voltage is changed.

FIG. 5 is a diagram showing a photosensor current measurement result when a voltage is changed.

FIG. 6 is a diagram showing a photosensor current measurement result when a voltage is changed.

FIG. 7 is a diagram showing an optical sensor current measuring method.

FIG. 8 is a diagram showing a photocurrent measurement result when light having a constant intensity is irradiated for a predetermined time.

FIG. 9 is a diagram showing simulation results of voltage applied to a liquid crystal medium and an optical sensor.

FIG. 10 is a diagram showing simulation results of voltage applied to a liquid crystal medium and an optical sensor.

FIG. 11 is a diagram showing a simulation result of a voltage applied to a liquid crystal medium and an optical sensor.

FIG. 12 is a diagram showing a relationship between an applied voltage and a base current when the film thickness is changed.

FIG. 13 is a diagram showing a relationship of photocurrent with respect to exposure intensity.

FIG. 14 is a diagram showing an apparatus for measuring a threshold voltage and a saturation voltage of liquid crystal.

FIG. 15 is a diagram showing measurement results.

FIG. 16 is a diagram showing a relationship between a voltage of an optical sensor and a base current.

FIG. 17 is a diagram showing a relationship between an optical sensor base current and a voltage applied to the optical sensor.

FIG. 18 is a diagram showing a relationship between an optical sensor B current and a base current component.

FIG. 19 is a diagram showing a relationship between an optical sensor film thickness and an applied voltage upper limit.

FIG. 20 is a diagram showing a relationship between an optical sensor B current and a base current component.

FIG. 21 is a diagram showing a relationship between an optical sensor base current and a voltage applied to the optical sensor.

FIG. 22 is a diagram illustrating a reading device of a transmissive liquid crystal medium.

FIG. 23 is a diagram illustrating a reading device for a reflective liquid crystal medium.

FIG. 24 is a diagram illustrating grayscale recording.

FIG. 25 is an explanatory diagram of a liquid crystal medium.

FIG. 26 is a diagram showing a relationship between transmitted light density and a read signal.

[Explanation of symbols]

10 ... Optical sensor, 20 ... Liquid crystal medium, 30 ... Power supply, 40 ...
Light source, 50 ... CCD sensor.

Claims (4)

[Claims] 1. A separation type information in which a photosensor having a photoconductive layer formed on a transparent electrode and a liquid crystal recording medium having a polymer-liquid crystal complex formed of a liquid crystal and a resin on the electrode are opposed to each other through an air gap. In an optical sensor for recording image information by aligning liquid crystal by imagewise exposing an optical sensor of a recording medium and applying a voltage between both electrodes, a base current (B current) when 100 V is applied is 1 ×. 10 ^-7 ~
An optical sensor for recording a liquid crystal medium, wherein the optical sensor has a density of 2 × 10 ⁻⁵ A / cm ² . 2. A separation type information in which an optical sensor having a photoconductive layer formed on a transparent electrode and a liquid crystal recording medium having a polymer-liquid crystal complex formed of a liquid crystal and a resin on the electrode are opposed to each other through an air gap. An optical sensor for aligning liquid crystal to record image information by image-exposing an optical sensor of a recording medium and applying a voltage between the both electrodes. An upper limit applied voltage V1 determined by a capacity of the liquid crystal medium and the optical sensor. And the threshold voltage of the liquid crystal medium, the saturation voltage of the liquid crystal medium, the resistance of the liquid crystal medium, and the lower limit applied voltage V2 determined by the resistance of the optical sensor, the film thickness and the base current satisfy V1> V2. An optical sensor for recording liquid crystal media. 3. The photosensor according to claim 2, wherein the photosensor current ( _BD current) in the unexposed portion is 2 × 10 ⁻⁶ to 4 × 10 ⁻ between the upper limit applied voltage V1 and the lower limit applied voltage V2. ⁶ A
/ Cm ² to become such applied voltage condition exists, and the optical sensor current (B _L current) 0.5 × 10 ^-6 to 1 of the exposed portion at the time of voltage application in such a voltage application condition. 5x
An optical sensor for recording a liquid crystal medium, characterized in that it is 10 ⁻⁶ A / cm ² . 4. The photosensor according to claim 2, wherein the photosensor current ( _BD current) in the unexposed portion is 2 × 10 ⁻⁶ to 4 × 10 ⁻ between the upper limit applied voltage V1 and the lower limit applied voltage V2. ⁶ A
There is an applied voltage condition that results in / cm ² and the photosensor current (B _L current) in the exposed portion when a voltage is applied under this voltage application condition is 1.5 × 10 ^-6 A / cm ² Optical sensor for recording liquid crystal media characterized by being large.