JPH0419640A - Optical record and display material - Google Patents

Abstract

PURPOSE:To stabilize the optical record and display material against external light and to enable high-speed writing and erasing by forming said material comprising a twisted nematic liquid crystal layer, outer and inner electrode layers, outer and inner light-polarizing layer, and a recording layer, and applying voltage to both electrode layers from a light supply. CONSTITUTION:The optical record and display material is formed by arranging successively from the incident side of light the outer light-polarizing layer 1, the electrode layer 2, the liquid crystal layer 3, the electrode layer 2, the inner light-polarizing layer 4, and the recording layer 5, and voltage is applied to both electrode layers from the power supply, and the light-polarizing layers 1, 4 are set on both sides of the twisted nematic liquid crystal layer 3 subjected to treatment for arranging the liquid crystal in parallel, and the external incident light can be freely shielded or transmitted by applying voltage to the liquid crystals, thus permitting the external light to be shielded and record to be stably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to recording and display materials controlled by light.

[Prior Art] There are three types of functionality of recording and display materials controlled by light: read-only, write and read, and write, read and erase. Among these, what will become mainstream in the future are recording and display materials of the type that can be written, read and erased. This type of optical recording display material uses a technique using so-called photochromism, or a technique that combines phase change of liquid crystal and photochromism.

The technique using photochromism utilizes the fact that the absorption spectrum unique to a substance is changed by photoexcitation to develop a new absorption spectrum.

For example, if the spectrum shown in FIG. 6(a) becomes the spectrum shown in FIG. 6(b) due to optical excitation, then λ
1, it is on before optical excitation (FIG. 6(a)) and off after optical excitation (FIG. 6 [present]), and can be used for recording and display. If the write operation is to optically excite the spectrum shown in FIG. 6(a) to the spectrum shown in FIG. 6(b), then from the spectrum shown in FIG. 6(b) to the spectrum shown in FIG.
The erasing operation is performed by optically excitation to the spectrum shown in Figure (a).

Conventionally, compounds with such characteristics are shown in Figure 7 (
a) There were compounds such as stilbene, fulgide and diallylethenic anhydride shown in (b) and (C), and azobenzene and stilbene shown in Figure 8 (a) and 8).

The technology that combines liquid crystal and photochromism utilizes the fact that a change in the three-dimensional structure caused by light irradiation is transmitted to the liquid crystal to destroy its inherent performance as a liquid crystal.

For example, suppose that azobenzene shown in FIG. 8(a) is mixed or bonded to the liquid crystal phase. At this time, when the azobenzene is not irradiated with the excitation light, the monitor light g is in a light transmitting state because the structure of the azobenzene 31 is similar to the liquid crystal 32, as shown in FIG. 9(a). ing. In addition, when azobenzene 31 was irradiated with excitation light, Fig. 9(b)
As shown in FIG. 2, since the azobenzene 31 undergoes a structural change and destroys the structure of the liquid crystal 32, the monitor light g is scattered at the destroyed portion and is in a light-opaque state.

In this case, when the light-transmitting state is turned on, the light-impermeable state is turned off, and the erasing operation is to return the azobenzene that has undergone a structural change to its original structure using a different wavelength.

[Problem to be solved by the invention]

The above-mentioned conventional optical recording and display materials had the following drawbacks.

The first drawback is that it is unstable against external light and requires considerable effort to maintain records.

In other words, if the irradiation light for writing is ultraviolet light, the erasing light is visible light (if the irradiation light for writing is visible light, the erasing light is ultraviolet light), so external light is needed to maintain records. must be completely blocked. In particular, when using a floppy disk as a recording medium, it seems possible to block external light with a 3.5-inch disk, but since the shutter for recording operations can be easily opened, it is difficult to use such a device under external light. If you do this, your records will be easily erased. Although such drawbacks are unique to this technology, the reality is that the problem has not been solved from the disk case.

Furthermore, with the recent advances in FA,
It cannot be used for recording and display materials, such as so-called programmable tags, which are used in environments where they are constantly exposed to external light.

The second drawback is a lack of thermal stability.

That is, azobenzene and stilbene shown in FIGS. 8(a) and 8(b) return from the cis state to the original trans state within several hours to several days at room temperature.

Therefore, in the photochromism method, fulgide and diallylethenic anhydride shown in FIG. 7(b) (C) have been proposed as photochromic compounds.

In addition, with technology that combines photochromism and liquid crystal,
Liquid crystal surrounds the cis pair to prevent it from returning to the trans form, but the fact that this effect is sufficient means that structural changes such as azobenzene are less likely to occur due to light irradiation. Erasing could not be performed quickly.

Furthermore, in order to facilitate photoisomerization from the trans form to the cis form, it was necessary to heat the liquid crystal in advance to the temperature at which it would become isotropic.

Furthermore, if for some reason it was placed in an environment at a temperature higher than that at which it becomes isotropic, the previous records would disappear.

An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide an optical recording and display material that is stable against external light and that can be written and erased at high speed.

[Means to solve the problem]

The present invention has been made to achieve the above objects,
Polarizing layers are provided on both sides of the liquid crystal phase, and the liquid crystal state is changed by charging the liquid crystal layer, so that external light can be freely blocked or transmitted.

That is, the optical recording display material of the present invention includes a twisted non-machining liquid crystal layer subjected to a parallel alignment process, electrode layers arranged on both sides of the liquid crystal layer, and a layer laminated on each of the electrode layers to make it opaque to light. It has outer and inner polarizing layers arranged to adjust the polarization direction in a similar manner, and a recording layer made of a photochromic compound arranged on the input side of the inner polarizing layer, and the electrode layers are connected via a power source. It is structured with the following characteristics:

The basic layer structure of the optical recording and display material of the present invention will be explained based on FIG.

In this figure, the upper side of the figure is the incident side of light, the lower side of the figure is the reflection and transmission side of light, and from the upper side of the figure, outer polarizing layer 1, electrode layer 2, liquid crystal layer 3, electrode layer 2, inner polarizing layer 4 and recording layer 5
are arranged sequentially.

The outer polarizing layer and the inner polarizing layer are arranged so as to have the same polarization direction, that is, only light having the same polarization plane is transmitted. A polarizing film, a polarizing plate, etc. are used for this polarizing layer.

Further, the polarizing layer may be formed integrally with the liquid crystal cell. Furthermore, a protective layer can be provided on the outside of the outer polarizing layer (on the light incident side).

The liquid crystal layer is formed of twisted nematic liquid crystal subjected to parallel alignment processing, and rotates the incident light by a predetermined angle and emits it. Therefore, when the twisted liquid crystal state is maintained, the light incident from the outer polarizing layer is rotated, so that the light transmitted through the liquid crystal layer is blocked by the inner polarizing layer. This rotation angle is preferably 90 degrees.

Moreover, this liquid crystal layer is oriented along the optical axis by being charged. Therefore, at this time, the light incident from the outer polarizing layer is passed through once without rotating the optical plane by m times, so that the light emitted from the liquid crystal layer passes through the inner polarizing layer and reaches the recording layer.

In other words, the liquid crystal layer does not become isotropic under the environmental temperature in which it is used, and rotates the incident light in an uncharged state before emitting it.
Any device that emits light that enters in a charged state without being rotated may be used.

The time during which the liquid crystal layer is charged, ie, the time during which external light can be transmitted, can be arbitrarily set using a condenser or the like, and the irradiation light may be continuously irradiated for the necessary time.

In such a liquid crystal layer, for example, 4-cyano-4 shown in FIG.
- Pentoxybiphenyl is mentioned.

The electrode layer is used to charge the liquid crystal layer and change its orientation so that it aligns along the optical axis. For example, if a so-called transparent electrode such as indium tin oxide (hereinafter referred to as ITO) is used, good.

The electrode layer can be connected via a light sensor that is activated when a particular wavelength or light intensity is applied.

The recording layer may be any type of photon chromink compound as long as it is thermally stable, it may be made into a polymer and coated and fixed onto the substrate, or it may be sealed in another binder.

To read the records on the recording layer, either transmitted light or reflected light may be used.

That is, when using transmitted light, the substrate itself coated with a recording layer made of a photochromic compound is made of a light-transmitting material, such as glass or polycarbonate, and
It is made of a material that can transmit the monitor light for reading, and the transmitted monitor light is read by a light receiver placed below.

In addition, when using reflected light, the substrate coated with a recording layer made of a photochromic compound is made of a material that reflects light, or a reflective layer is provided at the bottom of the substrate that can transmit light, and the reflected light is is read by a receiver placed above.

[Function] In the optical recording display material of the present invention, the outer polarizing layer converts external light into coherent light and makes it incident on the liquid crystal layer, and the liquid crystal layer rotates the coherent light incident from the outer polarizing layer by a predetermined angle. Or let it pass through as is. The inner polarizing layer blocks light that has entered from the liquid crystal layer and has been rotated by a predetermined angle, or allows light that has entered from the liquid crystal layer to pass therethrough. Recording or erasing of recording is performed on the recording layer by light incident from the inner polarizing layer. Further, the electrode layer and the power source charge the liquid crystal layer to orient the liquid crystal layer so that the listening direction is along the optical axis, and the light incident from the outer polarizing layer is transmitted as it is without being rotated.

[Example] An example of the optical recording and display material of the present invention will be described based on FIGS. 2 to 6(a) and FIG. 7(b).

Figure 2 is a cross-sectional view of the optical recording display material with each layer separated, Figures 3 (a), (b), (C), and (d) are cross-sectional views showing the same operation as above, and Figure 7 (b) is an example. This is a structural formula of a photochromic compound used in the same recording layer.

In FIG. 2, 11 is a liquid crystal layer, and on both sides of this liquid crystal layer 11, a polyimide film 12 for liquid crystal alignment, a 170 layer 13 as an electrode layer, and a cell layer 4 for liquid crystal are arranged, respectively. An outer polarizing layer 15 is laminated on the liquid crystal cell 14 on the light incident side (upper side in the figure), and an inner polarizing layer 16 is laminated on the liquid crystal cell 14 on the anti-light incident side (lower side in the figure). There is.

Furthermore, a recording layer 17 , a recording layer substrate 18 , and a reflective layer 19 are arranged on the inner polarizing layer 16 .

The liquid crystal layer 11, the polyimide film for liquid crystal alignment 12.
The 170 layer 13 and the liquid crystal cell 14 contain a compound shown in FIG.
-cyano-4'-pentoxybiphenyl) is sealed in a liquid crystal state. Liquid crystal cell 14
The thickness was 10μ.

The outer and inner polarizing layers 15,16 are made of polarizing films (HN-428E manufactured by Japan Polaroid Co., Ltd.) with a thickness of 0.5 mm, and these polarizing layers 15,16 are arranged so as to polarize light in the same direction. There is.

The recording layer 17 and the recording layer substrate 18 are prepared by dissolving 10 parts of a thermally stable compound shown in FIG. 7(b) as a photochromic compound in 100 parts of MMA (methyl methacrylate) and 30 parts of styrene. 0.5 part MEKP
After mixing well with O (methyl ethyl ketone peroxide), it was coated on a quartz plate to a thickness of 3 to 5 μm using a spin coater, and left in an oven at 50° for 5 hours to form an MMA copolymer film. It is formed as.

The reflective layer 19 is formed by depositing Ag on a glass plate.

Further, the 170 layers 13 are connected via a battery 2o as a power source and a photoelectric sensor 21.

Next, the operation will be explained based on FIGS. 3(a), (b), (c) and (d).

The operation of blocking external light will be explained.

When the optical recording and display material is left in a state where nothing special is done, as shown in FIG.
The light enters the liquid crystal layer 11 through the layer 13 and the polyimide film 12 for liquid crystal alignment. The external light a that has entered the liquid crystal layer 11 is emitted with its polarization direction rotated by a predetermined angle, and is emitted from the liquid crystal alignment polyimide film 12.170 layer 13.
The light passes through the liquid crystal cell 14 and reaches the inner polarizing layer 16. However, this external light a has a polarization direction of the inner polarizing layer 1.
Since the polarization direction of light is different from that of light 6, it cannot enter the inner polarizing layer 16 and is blocked. Therefore, the external light a does not reach the recording layer 17.

The transmission operation of external light will be explained.

First, as shown in FIG. 3(b), the photoelectric sensor 21 is irradiated with light having a specific wavelength or intensity.

Then, the photoelectric sensor 21 closes the electric circuit and the battery 10
Power is supplied to the 170 layer 13, and the liquid crystal layer 11 is charged. As a result, the liquid crystal layer 11 loses its previous orientation and is rearranged in the charging direction. Therefore, the coherent light incident from the outer polarizing layer 15 passes through the liquid crystal layer 11 without being rotated, so that it matches the polarization direction of the inner polarizing layer 16, passes through the inner polarizing layer 16, and passes through the recording layer 17. can reach up to.

Then, in a state where external light can pass through as described above,
Performs recording, erasing, and reading operations.

To perform recording, as shown in FIG. 3(b), a recording laser beam C that excites the photochromic compound is irradiated to form a recording portion 22 in the recording layer 17.

At this time, if the absorption vector of the photochromic compound is as shown in Figure 6(a), the recording laser beam C
is the wavelength of λ1.

To erase, similarly to recording, the recording portion 22 formed on the recording layer 17 is erased by irradiating light with a wavelength of λ2.

To perform reading, as shown in FIG. 3(C), a weak laser beam d having a wavelength of either λ1 or λ2 is irradiated so as not to change the photochromic compound in the recording layer 17. For example, in the case of a wavelength of λ1, the laser beam d passes through the recording section 22, is reflected by the reflective layer 19, and is taken into the detector 23, so that the presence or absence of recording becomes clear. Furthermore, in the case of the wavelength λ2, the laser beam d is absorbed by the recording section 22, so if the reflection intensity is measured,
This time, on the other hand, the reflection decreases, making it clear whether there is a record or not.

FIG. 3(d) is a cross-sectional view when reading is performed by measuring transmitted light; in this case, no reflective layer is provided;
A detector 23 detects the laser beam d emitted from the recording layer substrate to the outside.
The process is the same as when using reflected light, except that the measurement is performed using .

FIG. 5 is an exploded sectional view of another embodiment of the optical recording and display material of the present invention.

The optical recording and display material shown in this figure is similar to the embodiment shown in FIG. 2, except that the outer and inner polarizing layers also serve as liquid crystal cells.

That is, in this figure, the upper side of the figure is the light incident side, the lower side of the figure is the anti-light incident side, and the upper polarizing layer 15 is from the upper side of the figure.
, ITO113, polyimide film for liquid crystal alignment 12,
Liquid crystal layer 11, polyimide film for liquid crystal alignment 12.17
The zero layer 13, the inner polarizing layer 16, the recording layer 17, the recording layer substrate 18, and the reflective layer 19 are arranged in this order. The ITO layers 13 are connected via a battery 20 and a photoelectric sensor 21.

The results of testing the performance of the above-mentioned optical recording and display materials will be explained.

Test I When the optical recording and displaying material obtained by removing the reflective layer 19 from the optical recording and displaying material shown in FIG. I confirmed that there is.

Next, the sensor is irradiated with 100-xenon light to charge the liquid crystal, making it isotropic and allowing external light to be introduced. During this time, a 20 mW dye laser is irradiated for 0.5 seconds, and after 1 minute, 100-xenon light is applied to the sensor. A monochromator (set to λ = 355 nm) installed at the rear of the cell was irradiated with -xenon light and a 0.1 m- dye laser (λ-335r+m).
When the light was received by the photocell through the laser, the transmitted intensity was 95% of the transmitted intensity of the 0.1 mW dye laser measured in a blank state. Therefore, it was confirmed that the photochromic compound was recorded by the 20 mW laser.

Next, in the same manner, the recorded data was erased using 100-xenon light and a 20 mW dye laser (λ-450 nm), and after 1 minute, 100-xenon light and 0.1 mW Dye laser (λ=335r+
When the photocell received the light through a monochromator (λ = 335 nm) installed at the rear of the cell, the transmitted intensity was equal to that of the mW that blocked 0 and 1 external light measured in a blank state. It was 30% of the transmitted intensity of the dye laser. Therefore, it was confirmed that the records were erased.

Test ① After exposing the optical recording and display material according to Test 1 under the sun for 100 hours, the same inspection as in Test 1 was conducted, and it was confirmed that the material operated without any abnormality.

Test ■ A glass plate coated with Ag evaporation was used as the head of the cell similar to Test I as a reflective layer as shown in Figure 2, and the same light irradiation as Test I was applied at an angle of 60° to the recording medium. When the reflected light was received by a photocell via a monochromator, it was possible to detect the presence or absence of recording sufficiently, although it was found to be about 20% lower than the transmitted light.

〔Effect of the invention〕

As described above, according to the present invention, by sandwiching the twisted nematic liquid crystal layer between two polarizing layers, external light is blocked,
By charging the liquid crystal layer and making the liquid crystal phase isotropic only when necessary, various optical recording and display materials related to recording etc. can be transmitted, so recording can be prevented from disappearing at undesirable times, and the recording can be held stably.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the basic layer structure of the optical recording and display material of the present invention, FIG. 2 is an exploded sectional view of one embodiment of the optical recording and display material of the present invention, and FIGS. 2(a) and (b) (c) and (d) are cross-sectional views showing the same operation as above, FIG. 4 is a structural formula showing the structure of liquid crystal, FIG. 5 is an exploded cross-sectional view of another embodiment of the optical recording display material of the present invention, and FIG. (a) (b) are spectrum diagrams showing the principle of optical recording, Figure 7 (a) (b) (C) are structural formulas showing the structure of photochromic compounds, and Figure 8 is also structural formulas showing the structure of photochromic compounds. , Figure 9 (a) (b
) is a schematic diagram showing the principle of technology that combines photochromism and liquid crystal phase change. 1.15...Outer polarizing layer 2.13...Electrode layer 3
．． 11...Liquid crystal layer 4.16...Inner polarizing layer 5.17...Recording layer

Claims (4)

[Claims] (1) A twisted nematic liquid crystal layer processed in parallel alignment, electrode layers placed on both sides of the liquid crystal layer, and laminated on each electrode layer, arranged with the polarization direction adjusted so as not to transmit light. an optical recording display comprising: outer and inner polarizing layers, and a recording layer made of a photochromic compound disposed inside the inner polarizing layer, the electrode layers being connected via a power supply. material (2) The optical recording and display material according to claim light (1), wherein an optical sensor is disposed between the electrode layer and the power source, and the liquid crystal layer is charged when the optical sensor receives light. (3) The optical recording display material according to claim (2), wherein a reflective layer is disposed inside the recording layer. (4) The optical recording display material according to claim (2), wherein a transparent layer is disposed inside the recording layer.