JPS61166523A - Image forming device - 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 an image forming device, and more specifically, relates to an image forming device that has a bistable smectic phase. The present invention relates to a color image forming device using dielectric liquid crystal.

11. Liquid crystal elements have been used in fields such as displays and optical shutters because devices can be made smaller, thinner, or have lower power consumption. In particular, dramatic advances have been made in the field of displays based on several outstanding inventions.

For example, M. 5chadt and W. Helfrich 15.
Applied, Puizix, Letters No. 1864 (”
Applied Pbvslcs Lsters'',
Vol, 18. No.

4') (1117+, 2.15), P, 127
~128 “Voltage-dependent optical behavior of twisted nematic liquid crystals J
(”Voltag@-Dependent 0p
tical Activity of a Twist
edNematic Liquid (:rygtal
The TN liquid crystal described in ``) is known.The X-Y matrix electrode structure is used to arrange the TN liquid crystals used in the field of displays in a matrix.

The driving method for this display element is a time-sharing method in which an address signal is selectively applied to the scanning electrode group in one cycle, and a predetermined information signal is selectively applied in parallel to the signal electrode group in synchronization with the address signal. However, with this display element and its driving method, as the number of pixels increases, the duty ratio decreases, resulting in problems such as a decrease in image contrast and the occurrence of crosstalk. In order to improve the image resolution by reducing the size of the matrix electrode, it is necessary to wire the matrix electrodes at a high density, which has the disadvantage that manufacturing is complicated. Also, Tee, Pee, Prodi, Shrith Knee.

Athers, G. Douglas Dixon “Iiiiiii Transactions on Electron”
Devices 995~1o01j [6 x 6 inches 2
0 line/inch LCD display spring 7L/J (T, P
,8rady,Juris A,^5ars,G,Do
uglas old won IEI! E Transac
tions on! Iectron Devi
c@s.

VOl, ED-20, (No, 11. Nov, 1873
), P2O3~1001″ A8X 8 Inc
h 20 Lines-per-Inch Li
quid Crystal Mouth 1spray Pan5
A display has been proposed in which a transistor (TPT) is provided for each pixel and switching is performed for each pixel.
Since the means of establishing a system are complicated, improvements are desired in terms of cost.

On the other hand, in order to eliminate the difficulty of wiring the electrodes and their lead wires at high density, which is common to the method of applying image signals to the liquid crystal using electrodes provided on the substrate as described above, one image value number is applied to the substrate. Several methods have also been proposed in which the power is provided externally. One method is a thermal scanning method using a long wavelength laser, but this method requires a high-power laser and takes a long time to write, so it is not suitable for direct display on a large screen, and is not suitable for projection-type displays. Applicable only to equipment. There is also a method of writing with an electron beam, but like CRT, this method has drawbacks such as not only being unable to obtain high resolution due to the spread of the electron beam, but also increasing the depth of the device.

In order to solve the problems of the conventional device described above, the present applicant has already proposed an image forming apparatus having a charge applying means outside the liquid crystal cell (Patent Application No. 598 of 1982).
This image forming apparatus is characterized by having a liquid crystal cell having a liquid crystal layer sandwiched between a pair of substrates, and means for applying an electric field exceeding a threshold value to the liquid crystal layer from outside the cell. The outline of this image forming apparatus will be explained with reference to FIG.

The liquid crystal element (cell) lot shown in FIG. 1 has a reflective structure, and a dielectric mirror 102 is disposed therein.

When a signal voltage corresponding to a digital image signal is applied to the ion generator 109, the charge receptor 104 is irradiated with image-like ions. For example, when the liquid crystal lO7, which has been brought into one stable state (first stable state*) of the bistable state, is irradiated with ions to the part indicated by txt, that part changes to a different stable state!
(second stable state).

Projection lights 112a, 112b, and 112c are irradiated onto the liquid crystal element 101 through the polarizing beam splitter 103, and the image recorded on the liquid crystal layer is projected onto the projection screen 113. The polarization direction of the polarization beam splitter 103 is
For example, the projected light 112a, 112b, 112c is set parallel or perpendicular to the alignment direction of the liquid crystal in a stable state.
Assuming that the components are polarized lights, these projected lights 112a and 112b
, 112c pass P through the polarizing beam splitter 103.
The liquid crystal element 101 is irradiated with the component polarized light. Of this P-component polarized light, 112a and 112C passed through the liquid crystal 110 arranged in the first stable state, were reflected by the dielectric mirror 102, and passed through the polarizing beam splitter as they were as P-component polarized light. Light 112aa and 112c
c. On the other hand, of the P-component polarized light, the projected light 112
b passes through the liquid crystal 111 arranged in the second stable state and is reflected by the dielectric mirror 102.

The polarized light containing the S component is modulated, and only the polarized light of the S component is reflected by the polarizing beam splitter 103 to become light 112bb, and this light is transmitted to the projection screen 113.
The image recorded on the liquid crystal element 101 is displayed on the projection screen 113.

The present invention relates to an improvement of the image forming apparatus described above, and particularly aims to provide an image forming apparatus suitable for forming multicolor images. That is, the image forming apparatus of the present invention includes a liquid crystal element having a cell structure in which a ferroelectric liquid crystal is sandwiched between an electric conductor and a charge acceptor, and a liquid crystal element that is movable along the charge acceptor and that is attached to the surface of the charge acceptor. An image forming apparatus comprising a charge applying means capable of applying a charge exceeding a threshold voltage of a liquid crystal,
Further, the present invention is characterized in that adjacent filter elements near the conductor are arranged with polychromatic optical filters having mutually different spectral characteristics, and the conductor is divided and arranged in correspondence with the filter elements.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to the drawings.

FIG. 2 is a partial schematic sectional view of an apparatus for explaining the action of an ion generator as a charge applying means used in the present invention.

! The ion generator 201 shown in FIG.
To :.

This is similar to the ion generation 'a109 shown.

For example, Japanese Patent Publication No. 54-78134 and Japanese Patent Publication No. 56-3
Those described in Japanese Patent No. 5874 and the like can be used.

In the ion generator 201 shown in FIG.

An AC high voltage is applied to the electrode 203, and this and the electrode 204
The insulating layer 205 is charged and discharged by generating a gas discharge due to the electric field generated between the two. That is, the insulating layer 205 is charged and discharged. Thus, a positive or negative ion source is created in the opening 208 of the electrode 204. electrode 20
4, an electrode 208 for selectively emitting ions is provided with an insulating member (spacer) 207 interposed therebetween.

By applying a DC voltage between the electrode 208 and the electrode 21O provided on the substrate 213 (glass, plastic, etc.) of the liquid crystal element 202, ions are generated from the opening 206 toward the charge receptor 209 of the liquid crystal element 202. irradiated. At this time, by selecting the direction of the electric field between the electrodes 204 and 208, either positive or negative ions can be directed toward the electrode 208. Between the electrode 208 and the electrode 210, only either positive or negative ions are irradiated toward the electrode 21O by a DC electric field. Therefore, by applying a signal voltage corresponding to the digital image signal to the electrode 204, the charge receptor 20
9 can be irradiated with imagewise ions to form a charge image.

The ion generator 201 shown in FIG. 2 has a large number of openings 206 arranged in a direction perpendicular to the paper surface to form an opening array, and when this opening array is scanned in the direction of an arrow 211, the entire surface of the liquid crystal element 202 is covered. It becomes possible to provide image-like charges. In other words, this method does not require the number of apertures corresponding to the number of pixels of the liquid crystal element and the number of drive elements, and the alternating voltage applied to the electrode 203 and the electrode 203 are not required.
By performing matrix driving between the image signal voltages of 4 and 4, the number of drive elements can be reduced.

The liquid crystal layer 212 includes electrostatic charges (
For example, an electric field is applied by the electric charge in the electrode 210 (for example, shown as e in the figure) and the electric charge in the electrode 210 that is introduced thereto (indicated as e in the figure), and this electric field causes a change in the alignment direction of the liquid crystal. let

Between the liquid crystal layer 212 and the charge receptor 209 or the liquid crystal layer 2
12 and the transparent electrode 210, an alignment control film 1 such as S
in, 5i02. Films of inorganic compounds such as TiO2 or organic compounds such as polyimide, polyamide, polyvinyl alcohol, polyester, etc. (not shown), and these films provided on the transparent electrode 210 also function as an insulating film.

The electric field strength that causes the alignment change varies depending on the type of liquid crystal, but is about 0.5 to 10XIO·V/m,
Expressed as the amount of charge to be provided, this varies depending on the dielectric constant of the liquid crystal layer 212 and the charge receptor 209, but is 1.5 to 44.
XIO → about 1 coulomb.

The thickness of the charge receiving layer 209 does not have much influence on the voltage distributed and applied to the liquid crystal layer 212, but as it becomes thicker, the resolution deteriorates due to the spread of the electric field, so the thickness should be approximately the size of one pixel. The thickness is preferably less than half that.For example, if the size of one pixel is 60 microns, the thickness is preferably less than half that, about 30 microns.Due to electrostatic charge, the thickness between the charge receptor 209 and the electrode 210 Since electrostatic attraction acts on the spacers 211, it is preferable to provide the spacers 211 with sufficient density so that the charge receptors 209 are not deformed.

The spacer 211 portion is made black or in a light scattering state depending on the display method so as not to adversely affect the image display contrast. If the ratio of the pitch of the spacer 211 and the pitch of the pixel approaches an integer, moiré may occur, so to avoid this, it is possible to select the pitch or angle of the spacer 211, or to arrange them randomly. It is.

The resistance value of the charge receptor 209 is 16 because when using a material with memory properties such as bistable smectic liquid crystal, it is sufficient to hold the charge only as long as necessary for orientation change.
A material having a low resistance of about 1Ω·am can be used. In this case, it is preferable to connect the end to ground or a low potential so that charges do not accumulate in the charge receiving layer.

When rewriting an image, the image can be erased using various methods depending on the liquid crystal phase used.For example, the written image can be erased by applying a uniform electric field to the entire surface. Although a corona discharger may be provided separately to charge or eliminate static electricity, the ion generator 201
It is also possible to apply an erasing signal instead of the image signal using .

Next, when effectively changing the alignment of liquid crystals using an electric field caused by a certain amount of charge externally applied, ferroelectric liquid crystals have a
Chiral smectic liquid crystals are the most suitable zero ferroelectric liquid crystals because they have an extremely high impedance of QI4Ω・cm or higher, and do not leak charge. , ++, 5. r'JIIL
<I'4'1': i 5-"'1)'(SmH"
) is suitable. In addition, this ferroelectric liquid crystal has bistability with respect to an electric field, and even after being aligned in one of the stable I islands due to the electric field effect, this stable state is maintained even if the electric field is removed. Therefore, it is particularly suitable for the image forming method of the present invention.

This kind of ferroelectric liquid crystal is called "L-all) +9?".
,.

5. “Ferroelectric liquid crystal” (“LE JOURNAL D
E PHYSIQUELETTER5' 3B (L-
89) 1975. rFerroelectricL
iquid Crystals J) ; 'Applied, Fizix, Letters' 3B (+1)
198G, ``Sub-microsecond bistable switching of liquid crystals'' (``APPlied Physics Let
ters” 3fl (II) 198G, r Sub
wicr.

5econd Bi-5table Electroa
ptic Switching 1nLiquid G
crystalsJ); “Solid State Physics” 1B (14
1) +1181 r liquid crystal" and the like, and the ferroelectric liquid crystal disclosed in these documents can be used in the present invention.

More specifically, as an example of the ferroelectric liquid crystal compound of ferroelectric specification 2 (with no change in content 1-) used in the method of the present invention, desyloxybenzylidene-
p'-amino-2-methylbutyl cinnamate (DOB
AMBC), hexyloxybenzylidene-p'-amino-2-chloroprovir cinname' (the following margins), HOBACPC and 4-o-(2-methyl)
-butylresolcylidene-4″-octylaniline (M
BRA8) and the like.

The behavior of this type of ferroelectric liquid crystal under an electric field is basically explained by Clark and Lagaval, for example, in US Pat. No. 4,367,992.
This is as disclosed in the specification of No. 4, and the point is that when an electric field acts on the calendar of these ferroelectric liquid crystals, only when the electric field exceeds a threshold determined by the liquid crystal layer, the liquid crystal molecules constituting the liquid crystal layer The dipole moment of is oriented in the direction of the electric field,
Depending on the direction of the electric field, the liquid crystal molecules assume a first or second stable state. This stable state is maintained until the next electric field greater than or equal to the threshold is applied in the opposite direction. Furthermore, since the polarization effect (birefringence effect) is different between the first and second stable states, this difference can be used as a display material. Ferroelectric liquid crystals are excellent display materials because of their high-speed response due to the interaction between the dipole moment and the electric field mentioned above, and their bistability that provides memory properties. In order for these characteristics to be effectively exhibited, it is preferable that the thickness of the liquid crystal layer be as thin as possible, and generally 0.5 to 20 μl, especially t.
A range from p to 5 is suitable.

According to the present invention, a filter element adjacent to the conductor (corresponding to 105 in FIG. 1 and 210 in FIG. 2) among the charge receptor and the conductor sandwiching the liquid crystal layer of the image forming apparatus as described above. A multicolor (herein used to mean two or more colors) optical filters (color filters) having different spectral characteristics are arranged, and conductors are divided and arranged in correspondence with the filter elements. , to form an image forming apparatus suitable for color image formation. FIG. 3(a) shows the overall configuration of an image forming apparatus according to the present invention.

The liquid crystal element 301 shown in FIG.
Color filter elements 314r and 314g are striped in parallel to 5.

A multicolor filter 31 formed by sequentially arranging 314b
4, and a substrate 306 made of glass or the like on which divided transparent electrodes 305 made of ITO or the like provided by vapor deposition or the like are arranged on one surface and a polarizing plate 312 is provided on the other surface corresponding to each of the filter elements, and a substrate 306 made of plastic or the like. A charge receptor 30 consisting of
The liquid crystal layer 7 has a cell structure in which a liquid crystal layer 307 is sandwiched between the spacers 308 and 4, and the thickness of the liquid crystal layer 7 is varied, for example, from 1 to 5 by the spacer 308.
is held constant at the end. An ion generating group 309 is arranged outside the charge receptor 304, and a polarizing plate 313 and an illumination light source 303 are further arranged outside the ion generating group 309. As the illumination light source 303, an incandescent lamp is conveniently used, and a fluorescent lamp, an LED array, etc. can also be used.

The operation of this device will be explained. First, prior to image formation, an ion generator 309 sends a negative ion beam to the charge receptor 3.
By irradiating the entire surface of the liquid crystal layer 04, a negative charge is uniformly applied, and the resulting voltage Eb is substantially applied to the liquid crystal layer. At this time, if the voltage Eb is made larger than the lll value voltage of the liquid crystal, for example, the liquid crystal molecules will be
A liquid crystal phase 310 arranged in the first stable state shown in FIG. 1 is uniformly produced.

The two polarizing plates 312 and 313 shown in FIG. 3(a) are arranged in a crossed nicol state.
are arranged so that incident light is polarized in the long direction of the liquid crystal molecules 310 arranged in the first state. Therefore, in this state, the incident light does not pass through, and the whole becomes in a "dark" state.

Next, the charge receptor 304 is irradiated with a positive ion beam from the ion generator 309 in the form of an image. At this time, the ion generator 3
09 or the liquid crystal element 301 can be moved to irradiate the surface of the charge receptor 304 with an ion beam while scanning (in this example, the ion generator 309 is directed to the liquid crystal element 301 as shown by symbol 315). (moved in the thickness direction of the drawing), the ion beam irradiation imparts charges to the charge receptor 304 in the form of an image (E).
An electric field Ea in the opposite direction to b is applied to the liquid crystal layer 307. When this voltage Ea exceeds the threshold voltage, the liquid crystal phase 310 arranged in the first stable state is changed to the liquid crystal phase 311 arranged in the second stable state. The charge applied to the charge receptor 304 leaks and disappears, and the voltage applied to the liquid crystal layer 307 also disappears. However, when the liquid crystal layer 307 is a ferroelectric liquid crystal as in this example, the memory property is Therefore, the recorded image is retained. In this liquid crystal phase 311, the long sleeve direction of the liquid crystal molecules is aligned with the polarizing plate 311.
．． In response to the deviation from the polarization direction of 312, the polarization direction of the incident light deviates from the polarization axis direction of these polarizing plates, which have a cross nicol relationship with each other, so that the incident light is transmitted and becomes a "bright" state. The image is displayed.

Here, in the present invention, since the color filter 314 is provided, the optical signal can be obtained as a color signal. This color filter 314 is shown in FIG. 3(a).
Alternatively, as shown in FIG. 4, for example, in the additive color method, three color filter elements of red (R), green (G), and blue (B) are arranged parallel to the scanning direction of the ion generator 309. , the substrate 30 is formed by a method such as photolithography.
6 may be formed in a stripe shape. Also, if it is a subtractive color method, it is cyan (C).

Magenta (M) and yellow (Y) are selected. If necessary, a color filter can also be formed by dyeing a monopolymer film.

FIG. 4 shows an example of the positional relationship between the opening of the ion generator 309 shown in FIG. 3 and the filter elements of each color in the color filter 314. The portion 401 is one-to-one with the color filter elements 314r, 314g, and 314b of each color.
It is not supported. The dot diameter of the image formed by ions irradiated from one opening of the ion generator is usually about 100 to 200 #L, and the width of each color filter element should be equal to or slightly smaller than this. By arranging the color filter elements in this manner, for example, nine dots in the shaded area 402 in FIG. 4 can be used as one pixel to perform color display. Of course, one pixel may be formed by one dot for each of the three colors, a total of three dots.

In addition, the application of signals for forming a color image is performed by controlling the electrical signals sent to the ion generator 309.
For example, as shown in FIG.
This is accomplished by selectively turning two dots into a "bright" state.

The meaning of correspondingly dividing the conductor 305 for each filter element according to the present invention will now be explained. In the case of a uniform conductor arrangement, the width of each color filter element is 150 m1!, as mentioned above! Therefore, in order to correspond to the dot formed by the ion and l to l,
When the ion generator scans, the dot deviation in the direction perpendicular to the scanning direction must be at least about ioom, otherwise the dot diameter will enter the adjacent color filter element, making it difficult to obtain a clear color image. Such mechanical precision can be alleviated by dividing and arranging the electrodes 305 and temporally dividing the electrodes on adjacent color filters. can be arranged in I! lI, electrode 3
Lead wires such as 05a, 305b, etc. are common for each color, and the three lead wires are connected to a power source 406. represents a power source that generates different voltages, and generates a voltage that attracts ions only while a pulse voltage is applied. Ion generator 3 showing how ions move toward selected electrodes according to FIG.
Ions are generated from the opening 401a of 09a in response to the image signal.

Now, when it is desired to impart an ionic charge to the charge receptor corresponding to the green filter element 314g, the corresponding electrode 314g
A pulse voltage of Vg is applied to 5g. When the ions exiting from the aperture 401a have e polarity, a voltage in a more negative direction is applied to the lead wire 512 than the voltages on the lead wires 511 and 513; tL6. Tatoe Jf511.513
A voltage of -200v is applied to 1*OV and L512. As a result, the equipotential surface in the space where the ions move becomes as shown by the broken line A, and the ions move as shown by the line B.
Even if the position of the ion aperture and the electrode are misaligned, the desired electrode 1
The I'IT function is to ensure that the charge is aged into the 2nd. As will be seen from now on, although Fig. 3 shows an example in which ion apertures exist for each electrode corresponding to a filter element of each color, one ion aperture is provided for one set of electrodes for three colors. It can be seen that it is possible to induce and write charges on any selected electrode by bending the ions as shown in Figure i5.

Note that in the drive method using an ion generator, a drive element with only a numerical aperture is not required, and the electrode 2 which is a scanning signal is not required.
AC applied voltage Vi (i-1, 2,
---) and to the electrode 204 (7) Image signal voltage Vsi (
Matrix driving can be performed between i=1.2 and eve). Here, when obtaining a color image, the image signal voltages to the electrodes 204 are temporally divided and applied for each color. The signal voltages Vr, Vg, and Wb given to each switching circuit are obtained by synchronizing them with the image signal voltage Vs corresponding to each color.
, . . . , thereby making it possible to form one image by imparting a charge to each charge receptor portion corresponding to each color filter element.

Figure 6 shows 1! Focusing on the pixel 402 (FIG. 4), an example of a timing chart is shown when image signals of all colors, for example, red, blue, and green, are applied to this pixel 402.

In FIGS. 3 to 6, an example of a transmissive liquid crystal display device with a built-in illumination light source is shown.
By arranging a 1M electric mirror in place of 13, it is also possible to provide a reflective display using external light.

Although not particularly shown, its configuration can be easily understood by comparing it with the device shown in FIG.

11. As explained above, in an image forming apparatus using a ferroelectric liquid crystal that is driven using an ion generator, a colored filter corresponding to the opening of the ion generator is disposed, and By dividing and arranging the conductors in correspondence with the filter main body, an image forming apparatus is provided which can reliably display a color image suitable for display on a large screen.

[Brief explanation of the drawing]

FIG. 1 shows an image forming apparatus at (
FIG. FIG. 2 is a partial schematic sectional view of an apparatus for explaining the charge application type used in the present invention. FIG. 3(a) is a sectional view schematically showing two embodiments of the present invention! be. FIG. 3(b) is a plan view showing changes in orientation of the liquid crystal layer. FIG. 4 is a conceptual diagram showing the positional relationship between the ion generator, the colored filter, and the divided electrodes. FIG. 5 is a conceptual cross-sectional view illustrating the state of ion induction by the divided electrodes. FIG. 6 shows an example of a timing chart when three color image signals are applied to one pixel. 109.201.309・9 Ion generator (with electric direction! L
means) 101.202.301-1 liquid crystal element J, 04.209.304...charge acceptor 107.2
12.307...Liquid crystal layer 312.313--Polarizing plate 314--Color 7 (Luther (314r, 31g, 314
3050-Transparent electrodes 303II11 arranged in a divided manner Light source 310--Liquid crystal 311 arranged in the first stable state...
Liquid crystal arranged in second stable state 211.315--Scanning direction υJ of ion generator--Figure 3 (a) Foot 1 □C Applicant's agent Monkey **轡i1. ．． /:. 1. Knee! Figure 1 of 21 Figure 2 Figure 3 (CI) Figure 5 Figure 6 Procedural amendment (method) May 1980 2L: Date

Claims (1)

[Claims] 1. A liquid crystal element having a cell structure in which a ferroelectric liquid crystal is sandwiched between a conductor and a charge receptor, and a liquid crystal element that is movable along the charge receptor and has a liquid crystal on the surface of the charge receptor. An image forming apparatus comprising a charge applying means capable of applying a charge exceeding a threshold voltage, further comprising a polychromatic optical filter in which adjacent filter elements have different spectral characteristics in the vicinity of the conductor; An image forming apparatus characterized in that conductors are divided and arranged in correspondence with elements. 2. Claim 1, wherein the charge applying means is capable of generating a charge pattern corresponding to different color signals sequentially, and switching the voltage applied to the divided array portion of the conductor in synchronization with the charge pattern. The image forming apparatus described above.