JPS59168484A - Image element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a thermal writing type recording/display element.

Devices capable of high-density recording and display include laser thermal writing liquid crystal devices, which write images by irradiating a laser beam onto a liquid crystal cell with a structure in which a liquid crystal material is sandwiched between two substrates, and liquid crystal cells. A Joule heat writing liquid crystal element is known, which writes an image using the Zeel heat generated by passing a current through a heater electrode provided on a substrate. All of these utilize the electrothermo-optic effect of liquid crystal. That is, when a thin layer of cholesteric liquid crystal or smectic liquid crystal exhibiting a transparent liquid crystal structure is partially heated and rapidly cooled, that portion generally transitions to an opaque liquid crystal structure that scatters light. A laser thermal writing liquid crystal element utilizes this phenomenon to write an image by irradiating and scanning a laser beam to shift the liquid crystal material in the irradiated area to a light scattering state. The written image can be erased by uniformly applying an electric field to the liquid crystal cell. Also,
Electrodes with an XY-IJ configuration are formed in a liquid crystal cell, and a current is applied to one electrode (for example, the At least the Joule thermal writing liquid crystal element is used to write images. In this case, the electrode on the opposing substrate side (here,
After the liquid crystal material has been heated, the electrodes are used to selectively apply an electric field between the X electrodes during the cooling process. By such driving, the liquid crystal material in the pixel formed at the intersection of the X electrode and the X electrode can be selectively shifted to a light scattering state. This is because a thin liquid crystal layer that is heated and rapidly cooled becomes a light-scattering state, but if an electric field is applied during cooling, the liquid crystal molecule alignment effect caused by the electric field causes it to become transparent instead of becoming a light-scattering state. It is. In this Joule thermal writing liquid crystal element, images can be sequentially rewritten. These laser thermal writing liquid crystal elements and Joule thermal writing liquid crystal elements are used as image recording elements or direct-view display elements that directly display written images. It is also used as a projection type display element that uses a system to project images for viewing. The above is a conventional example of a thermal writing type recording/display element using liquid crystal, but examples using substances other than liquid crystal are also known. For example, using a head lined with heating resistors,
Ag2Hg1. There are thermal recording/display elements that write images by applying temperature changes to inorganic materials such as. Furthermore, some recording/display elements using writing methods other than the thermal writing method are also known. An example of this is to form a photoconductive film on one side of the substrate of a liquid crystal cell, project a display screen such as a CRT (cathode beam) onto the photoconductive film, and convert the optical image into a voltage distribution image. This is an optical writing liquid crystal element that writes an image on a liquid crystal thin film by applying a voltage distributed according to the image to the liquid crystal thin film. As mentioned above, several devices for recording and displaying images are known, but no device has been found that satisfies both the high-density writing and high-speed writing performance required of recording and display devices. The current situation is that this is not the case. In other words, although laser thermal writing liquid crystal elements can perform high-density writing, they cannot perform high-speed writing due to scanning laser light, and Joule thermal writing liquid crystal elements have a large recording/display area in order to increase the speed. In this case, there is a limit to the electrode density and it is not possible to increase the density. Furthermore, in the thermal writing method using an inorganic material, high-speed writing is not possible because the heating resistor head is mechanically scanned for writing. On the other hand, in an optical writing liquid crystal element, high-density writing is not possible because the image is limited to the CR1 screen. As described above, conventional image elements cannot satisfy both high-density writing and high-speed writing performance. However, high-density and high-speed writing is possible if an image is written by scanning an electron beam and irradiating the material to cause a partial temperature rise in the material. High-speed operation is possible, just as in a CRT. Furthermore, C)! , T display or the optically written liquid crystal element using a CRT requires high energy, that is, a large electron flow, in order to make the phosphor of the CRT emit light. On the other hand, when using an electron beam as a heat source, the diameter of the electron beam can be narrowed to a small size, making it possible to perform high-density writing. This means that one electron is
This can be understood from the fact that when the energy 1 eV that an electron obtains when accelerated by a potential difference of , is converted into temperature, it reaches 11,605 K. This method of writing images by scanning and irradiating a material with an electron beam and causing a partial temperature rise in the material is capable of high-density and high-speed writing; As the material to be subjected to the irradiation, the materials used in the recording/display elements of the conventional thermal writing method mentioned above, ie, liquid crystal materials, mercury halide-based inorganic materials, etc. are used.

In particular, since the temperature at which liquid crystal materials change state is low, the temperature rise necessary for writing is small, and they are excellent in terms of high-density writing and high-speed writing, but because of their fluidity, It must be used while being held between two substrates, which is disadvantageous to a thermal writing method that utilizes heat generated by electron beam irradiation, that is, collision of electrons. This is because in the aforementioned laser thermal writing method and Ziehl thermal writing method, the surface of the substrate in contact with the liquid crystal material becomes the heat generating part, so there is no problem, but in the method of generating heat by colliding electrons with the substrate, the heat generating part is on the substrate. The presence of the substrate is disadvantageous in terms of heat utilization efficiency since it is on the opposite side of the surface that comes into contact with the liquid crystal. As a result, the high-density writing and high-speed writing features of the thermal writing method using electron beam scanning are reduced. The inventor of the present invention has studied many materials and structures of substrates that are irradiated with electrons, and has found a substrate with a structure that effectively conducts heat generated by collision of electrons. The present invention has been achieved by realizing a $ writing type image element using an electron beam scanning method that allows extremely high-density and high-speed image writing even when using a certain material.

An object of the present invention is to provide an image element that has particularly excellent performance in two aspects: high-density writing and high-speed writing.

The image element of the present invention uses heat generated by electron collisions to cause a local increase in humidity in a substance, and displays or records an image by using the temperature of the substance and the state change that occurs in the area that has undergone the increase. The image element is an image element having a structure in which the substance subject to the temperature increase is sandwiched between two substrates, and one of the two substrates on the electron irradiation side is arranged so that the substance subjected to the temperature increase is It is characterized in that it has a multilayer structure consisting of at least two layers: a conductive thin layer and a layer of an insulating material whose thermal conductivity in the film thickness direction is higher than that in the direction in which the film extends.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the image element of the present invention. In Figure 1, ■ is a glass tube, the inside of which is 1O
The vacuum is about -6 TOrr. Furthermore, an alignment treatment film 2 is formed on the inner surface of the front surface portion 1' of the glass tube 1. 3 is a substrate that holds the liquid crystal substance 7 together with the front part 1' of the glass tube 1, and has an M thin layer 15 with about 1000 holes on one side of a crystalline Be0 layer 13 with a thickness of about 0.3 fins; An alignment treatment film 14 is formed on the other surface. The alignment treatment films 2 and ]4 are both thin films of dimethyloctadecylaminoprobyltrimethoxysilyl chloride formed to a thickness of about 50 OA. This substrate 3 faces the front part 1' of the glass tube 1 via a spacer 6, and the gap therebetween is maintained at about 16 μm. 8 is a cathode, and the electrons that jump out from here are extracted by the anode 9, and the electron flow 1
0, which collides with the M thin layer -15 of the substrate 3.

The strength of this electron flow 10 is controlled by a grid electrode 11 and its direction by a deflection coil 12. An image element with such a structure is used as a liquid crystal vlJ7, and dichroic dye G202 (manufactured by Nippon Photosensitive Research Institute) is added to normal pentyl cyanobiphenyl (hereinafter referred to as 5CB).
When observed from the front of the glass tube 1 by scanning the electron flow by intensity modulating the electron flow, a purple color was observed on the transparent background (mirror surface by Adi!H1i'i15). Images could be displayed at a speed that sufficiently followed the TV screen. This is based on the following principle.

Figure 2 is a diagram showing the display principle of the image element of this example, showing the diopter change of the liquid crystal material at the point (pixel) irradiated with the electron flow and the reflected light intensity observed through the M thin layer. It shows the change. The temperature of the liquid crystal material is -C under the irradiation of the electron stream.
During this period, the temperature continues to rise due to heat generation due to electron collisions, and in the middle of this period, the temperature exceeds the liquid crystal-liquid transition temperature Tc of the liquid crystal material (35° C. in the case of 5CB in this example). That is, that pixel portion of the liquid crystal material is temporarily in a liquid state. Next, when the electron current irradiation stops, the temperature begins to drop, and when the temperature drops below TC, the liquid crystal material in the pixel portion that was in the liquid state returns to the liquid crystal state again. In this manner, the image element of this embodiment utilizes the fact that the liquid crystal material is heated by irradiation with an electron stream and instantaneously changes into a liquid state. That is, when the liquid crystal material is in a liquid crystal state, the dichroic dye is uniformly aligned, and in this embodiment, the dichroic dye G202 is aligned perpendicular to the surface of the substrate 3 due to the effects of the alignment treatment films 2 and 14. When oriented in the direction of 2, the dichroic pigment does not absorb light, so it appears transparent (highly reflected light). However, when the liquid crystal substance becomes liquid, the orientation of the liquid crystal molecules is disturbed, and as a result, the orientation of the dichroic dye becomes distorted, resulting in the original absorption of a specific wavelength, and the area appears colored (reflected light intensity decrease). When the temperature drops again and returns to the liquid crystal state, the absorption of light by the dichroic pigment becomes lS< and returns to transparency, but when the temperature drops, the change is gradual and 1
．． As a result, reorientation of liquid crystal molecules also occurs gradually, and therefore the transition from a colored state to a transparent state occurs gradually. In terms of driving, it is preferable that the temperature of the liquid crystal substance immediately before being irradiated with the electron current is constant, so in this embodiment, the time required for the liquid crystal temperature to return to the temperature before being irradiated with the electron current is defined as the frame time.
The time required for the temperature to return to TC is defined as the field time, and the intensity of the electron flow is controlled so that the field time is about half of the frame time. In this way, so-called interlaced scanning was performed to display a moving image. The frame time was about 25 m5, and the display density was about 1200 lines on a 16-meter high-Q display surface. The writing speed is the same as that of CRT, but high-density writing is possible because CRT requires a large beam current for the phosphor to emit light, and as a result, the beam diameter of the electron flow is approximately 0. In contrast, in the image element of this example, the liquid crystal material is heated to a temperature of only 40°C.
This is because the temperature can be raised to a sufficient extent, so that writing can be performed using an electron stream with a very narrow beam diameter. This can be understood from the fact that when one electron is accelerated by a potential difference of 1 sq., the energy leV obtained by the electron reaches 11605 K when converted into temperature. In addition, in the image element of this embodiment, the use of a substrate having a structure in which the M thin layer 15 is formed on the electron irradiation side of the crystalline Be0 layer 13 is used as the substrate 3, which has the advantages of the thermal writing method using electron beam scanning. This is an important element to fully utilize the characteristics of density writing. That is, heat generation due to electron irradiation occurs in the M thin layer 15,
This conducts through the substrate 3 and partially raises the temperature of the liquid crystal substance 7, so even if the temperature rise occurs in a minute area on the electron irradiated surface, while the heat is conducted through the substrate, only in the thickness direction of the substrate. In addition, the heat is also conducted in the direction in which the substrate spreads, and when the heat is transferred to the liquid crystal material, there is generally a problem that the area where the temperature increases is larger than the diameter of the irradiated electron beam. However, as in this example, crystalline B
In an image element using eO as a substrate, an image could be displayed with a spot having a diameter of about 10 μtn without such a problem. In other words, approximately 120
It was possible to display with a density of 0 lines. This is crystalline Be
As a result of the fact that the 0 layer has a characteristic that the thermal conductivity in the layer thickness direction is about 4 times larger than the thermal conductivity in the spreading direction of the layer,
This is because almost no heat is transferred in the direction of expansion of the substrate, and heat is efficiently transferred in the thickness direction of the substrate, that is, from the heat generating portion due to electron irradiation to the liquid crystal material. In addition, the crystalline Be used
The thermal conductivity of 0rfii is 0.63 cal/in the layer thickness direction.
In CCm-5-de, the layer spreading direction was 0.14 Ca ray·s-deg. The conductive M thin layer provided on the surface of the crystalline Be0 layer is necessary to prevent the deposition of irradiated electrons, and in an image element with a structure without this layer, sufficient heat generation due to electron beam irradiation is not generated. The image could not be displayed. This conductive thin layer also allows the displayed image to be transferred to the glass surface 1.
It is desirable that it be as thin as possible within a range that forms a mirror surface sufficient for viewing from the side . In addition, in order to confirm that using a material for the substrate whose thermal conductivity is lower in the film thickness direction than in the film spreading direction is a necessary element to realize high-speed, high-density writing. As a comparative example, an image element with a structure using a glass layer instead of the crystalline Be0 layer in the above example was created, and the frame time was about 3 Qms, and the display density was about 1000 lines on the high Q display surface of 16. However, the results were not as good as those of the above examples. In addition, as another comparative example, an image element with a single-layer structure of an M substrate instead of the two-layer structure of the crystalline Be0 layer and the thin M layer in the previous example was created. Although the display density was the same, the display density was approximately 600 lines on a display surface of 15 m1 high, which was significantly inferior to the previous example. The thermal conductivities of the glass layer and M substrate used in these comparative examples are Q and Q, respectively.
Q 15 ca I /can s * deg and 0.65 ca 17 cm·s ·deg, and there was no difference between the spread direction and the thickness direction of the substrate. Furthermore, compared to the crystalline Be0 layer used in the above example, the glass layer has a lower thermal conductivity than the crystalline Be0 layer, and the M substrate has a higher thermal conductivity than the crystalline Be0 layer. In this way, it is not possible to achieve both high-speed writing and high-density writing simply by changing the thermal conductivity of the substrate. It was confirmed for the first time that particularly excellent performance in two aspects of high-speed writing and high-density writing can be obtained by using a substrate composed of a layer of a material whose thermal conductivity is higher than that in the spreading direction.

Note that it is not essentially necessary for a substance whose thermal conductivity in the film thickness direction is larger than that in the film spreading direction to be insulating, and if the material is conductive, there is no need to Although it is thought that there is no need to form a thin layer, no such substance has been found so far. Furthermore, the image element of this embodiment can be used not only as a direct-view display in which the display surface is viewed directly, but also as a projection-type display in which the display surface is enlarged and viewed using a projection light source and an optical system. It has been confirmed that when used as a projection display, an extremely bright screen can be obtained compared to a method that projects the display surface of a CRT. The displayed color was purple because G202 with a maximum absorption wavelength of S 548 nm was used as the dichroic dye, but the selection and mixing of dichroic dyes made it possible to display any color including black. It goes without saying that fJj is possible. In addition, it is limited to the reflation and Soche type display as in this embodiment, and the change in state that occurs before and after the temperature rise persists unless intentionally manipulated, so-called storage type liquid crystal material is used to display the storage type display or image recording. Needless to say, etc. are also possible.

In the above, the image element of the present invention has been described with reference to an embodiment using a liquid crystal substance, but even when using a so-called thermochromic substance that changes color when heated, it may be necessary to use it by sandwiching it between two substrates. Needless to say, the image element having the structure of the present invention is effective if such an object exists.

As described above, according to the present invention, an image element having particularly excellent performance in two aspects of high-density writing and high-speed writing can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the image element of the present invention,
1 is a glass tube, 1' is a front part of the glass tube, 2 is an alignment film, 3 is a substrate consisting of a crystalline Be0 layer 13, an alignment film 14, and an M thin layer 15, 6 is a spacer, 7 is a liquid crystal material, 8
is a cathode, 9 is an anode, 10 is an electron current, 11 is a grid electrode, and 12 is a deflection coil. FIG. 2 is a diagram illustrating the display principle in one embodiment of the image element of the present invention.

Claims (1)

[Claims] A vacuum having a display element between two substrates with a substance that generates heat due to collision of electrons, a cathode that emits electrons, an anode, and a grid electrode provided between the cathode and the anode. The display element includes a container and a deflector ♂ for changing the direction of electron flow, one substrate of the display element is made of the wall surface of the vacuum container, and the other substrate is made of a conductive thin film and a material having a thermal conductivity in the film thickness direction. 1. An image element comprising a multilayer structure in which at least an insulating thin film is laminated with a thermal conductivity higher than the thermal conductivity in the film surface direction, and the conductive thin film is disposed on the side receiving electron irradiation.