JPH03180870A - LCD shutter 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 [Field of Industrial Application] The present invention relates to the structure of a liquid crystal shutter device in which a plurality of microshutters are arranged using liquid crystal characteristics in an exposure device used in an electrophotographic process.

[Conventional technology]

An example of the prior art using liquid crystal will be explained with reference to FIG. 1
1 is a photosensitive drum which rotates in the direction 1b or vice versa, and is exposed to light in the main scanning direction indicated by the dotted line 1b to form a latent image of charge.

A liquid crystal shutter 3 composed of a plurality of micro-shutters is used to control the light from a light source 4 covered by a light shielding plate 5, and is opened and closed by an external data signal to control the passage of light by $1. 2 is a lens array that forms an image formed by the liquid crystal shutter 3 onto the photosensitive drum 1; 6a.

Arrow lines 6b and 6c indicate the direction of light.

Although not shown, the latent image on the photosensitive drum is developed with charged toner. This developed image is transferred and fixed onto recording paper.

Although not shown, the temperature of the liquid crystal shutter 3 is controlled within a range of approximately 35 degrees to 60 degrees in order to stabilize the shutter speed and the ON-OFF ratio of light.

Conventionally, the light source 4 is a fluorescent lamp or a halogen lamp. Fluorescent lamps cannot provide stable brightness unless the vapor pressure of mercury inside the tube is stabilized, so temperature control is required. Additionally, fluorescent lamps require large ballasts that include transformers.

Halogen lamps have sufficient brightness, but since they are basically filament lamps, they generate heat of several hundred watts, so
This makes it difficult to control the temperature of the liquid crystal shutter 3 mentioned above.

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, when the light source is a fluorescent lamp, temperature control and a large ballast are required, which hinders miniaturization and cost reduction of the device.

Halogen lamps have large power consumption, which increases costs due to the power source housing, and has major problems in thermal design.

The present invention is intended to solve these problems, and its purpose is to obtain a light source with stable brightness that excites a phosphor by accelerating electrons in a hot cathode that generates little heat.

[Means to solve the problem]

In order to solve the above problems, in a liquid crystal shutter device in which a plurality of micro-shutters are arranged in a predetermined manner in the main scanning direction, a light source emitting light to the liquid crystal shutter device has a width (]) larger than the shutter width of the liquid crystal shutter device. a transparent substrate having a phosphor shaped like a phosphor, a thin metal film covering at least the entire surface of the phosphor, and a cathode heated at a voltage sufficiently lower than an applied voltage for accelerating electrons between the metal and the phosphor; , the phosphor, the metal, and the cathode are held in vacuum in cooperation with the transparent base material; preferably, the inside is treated to reflect light and the outside is treated to prevent light transmission; The device is characterized in that it enables a compact configuration, reduces power consumption, and reduces costs at the same time.

Furthermore, a separation means for separating the light from the light source into polarized light whose phase differs by 901 from the effective polarization of the liquid crystal shutter device, a phase rotation means for bringing the polarized light of 90°51 into phase with the effective polarization, and a combining means Another major feature is that the effective polarization is almost doubled.

[Effect]

According to the above configuration of the present invention, the heating of the cathode is only a few watts to facilitate electron emission, and the temperature rise is small.
Therefore, the liquid crystal shutter and the light source can be brought into close contact with each other. Therefore, miniaturization, lower power consumption, and cost reduction are possible.

〔Example〕

FIG. 1 is a perspective view of a configuration in an embodiment of the present invention.

10 is a shutter device, which includes a shutter section 10a and a light source section 10.
Consists of b.

The shutter section 10a is constructed by sandwiching a liquid crystal 15 between a transparent common base material 12 on which a common electrode is disposed, and a transparent segment base material 11 on which segment electrodes are disposed, facing each other with a substrate 13 interposed therebetween. Polarizing plates 14 facing each other at a predetermined polarization angle are arranged on both sides.

The segment base material 11 is equipped with a driver 18 that extends and drives the segment electrodes 17. This is also a feature of the present invention, which simplifies the interface.

16 represents a common electrode terminal from a common base material.

Although the common electrode terminals 16 are shown as four in the figure,
Generally, the number of common electrode terminals×the number of segment electrode terminals=the number of main scanning pixels.

However, if the number of common electrode terminals or the number of multiplexes is increased too much, the ON-OFF ratio of light will deteriorate, resulting in characters and figures of poor quality. Currently, the number of multiplexes is 16.
The following are appropriate.

The number of main scanning pixels mentioned above differs depending on the pixel density for A4 size, but it is 1
It is about 700-4000.

l9 is a signal terminal and is common to driver 1B f! The data signal and clock are given in synchronization with the pole signal.

Next, the light source section 10b of the present invention will be explained with reference to FIGS. 2(a) and 2(b). FIG. 2(a) shows the structure of one transparent base material 25, and FIG. 2(b) shows the other M base material, 3F! nJ
] Base material 25 Lid M material 26 Real MN'? -26a and 2
6b and near the dotted line frame 26c, and the exhaust port 3
Make it more vacuum than 1.

Reference numeral 27 is a phosphor placed on the transparent substrate 25, and its emission wavelength is matched to the sensitivity wavelength of the photoreceptor. - In the crotch area, red to near-infrared light is desirable, and 28 is a thin metal film that is arranged so as to cover at least the entire surface of the fluorescent body 27. This metal 28 functions as an anode for accelerating electrons, and also prevents secondary electrons from forming a negative charge on the streetcar due to collision of electrons with the phosphor 27.

Furthermore, it has the effect of reflecting the light emitted by the fluorescent body 27 and increasing the amount of light emitted to the outside.

Reference numeral 29 denotes a cathode made of tungsten wire or the like, which is led to cathode terminals 29a and 29b led out to the outside via pillars 30a and 30b provided on the transparent base material 25.

An alternating voltage of several volts or lI! is applied to the cathode terminals 29a and 29b. A current is applied to heat the cathode 29 to the extent that it does not become red hot. The purpose of making the cathode 29 non-red-hot is to ensure the life of the cathode, and it is better to make it red-hot in terms of electron emission.Therefore, an auxiliary material of Ear (barium oxide) Mi, which has a small work function, is applied to the cathode 29.

Here, the cathode terminal 29a applies a DC voltage of 30 to 200 volts between the cathode 29 and the metal 28 via the cathode terminal 29b. The electrons at the cathode 29 are accelerated and collide with the phosphor 27.

The phosphor 27 is excited over its entire length and emits light with a predetermined brightness.

Here, the reason why the heating voltage of the cathode is set to several volts in the above is to reduce the difference in acceleration voltage over the entire length to obtain uniformity of electron acceleration and to prevent unevenness in brightness.

Therefore, since the temperature distribution of the cathode 29 is required to be uniform, the resistance per unit length of the cathode is also made to be uniform over the effective width.

Incidentally, since light that does not pass through the shutter portion 10a will be harmful, the inner surface of the swallow substrate 26 is configured to reflect light toward the transparent substrate 25, and the outer surface is configured not to transmit light.

Here, the values of various quantities will be explained. The sensitivity of the photoreceptor is 5-10μ
J (microjoule)/am".

Since the liquid crystal shutter uses only specific polarized light, the transmittance is 5.
0% or less, the brightness of the light source section 10b needs to be at least twice the sensitivity of the photoreceptor. For example, 20 μJ/cm
', then the light emitting area of the phosphor is 0. 5x 20c
m”, the required total luminous energy is 20uJ/cm
"xO, 5X20cm" = 200AZJ. If this is repeated at IKHz in the sub-scanning direction, 200 mW (
milliwatt〉.

Since the luminous efficiency of the phosphor is 50% or more, the light source section 10b
The required luminous energy is 200 mW x 2=40
0mW is enough.

Here, if the voltage between the metal 28 that accelerates electrons and the cathode 29 is LOOV (volt), the current of the cathode 29 is 4 m
A (milliampere).

The cathode 29 needs to emit electrons equivalent to this 4 mA. Electron emission of cathode 29・1 is emission area, material specification S)
[Function, related to the temperature of the material.

Calculation of these relationships is troublesome, but in reality, in this case, the heating of the cathode 29 may be less than IW.

Therefore, the power consumption of the light source section 10b is 2W or less. With this level of power consumption, sufficient heat can be dissipated from the volume of the components, and heat generation does not become a problem.

Therefore, even if it comes into close contact with the shutter portion 10a, there is no effect, and the device can be made smaller.

Next, in Figure 3, it is assumed that the liquid crystal shutter mentioned earlier uses only predetermined polarized light. If this is the effective polarization for the liquid crystal shutter, then the one marked with a double-headed arrow S is the ineffective polarization.

All light can be decomposed into these P and S components.

The light emitted from the light fi 40 is separated into P polarized light and S polarized light by a half mirror 41. The P-polarized light is reflected by the half mirror 41, guided to the combining means 44 by the mirrors 42 and 43, and reflected and radiated to the left on the AA' plane of the first combining means 44.

On the other hand, the S-polarized light that has passed through the half mirror 41 is reflected by the mirror 45 and passes through the beam splitter 46. When this S-polarized light passes through a quarter-wave plate, it becomes Z-polarized light (4
5°). Reflected by Mira 48 and 1/4 again
The light passes through a wave plate and is further oriented at 45° to become P-polarized light.

The beam splitter 46 reflects the P-polarized light at a surface 46a.

This P-polarized light passes through the mirror 49 to the combining means 44.
It is reflected at the BB' plane and combined with the original P polarized light mentioned above. Although there is some intermediate absorption, the effective P-polarized light is approximately doubled.

The power consumption of the light source section 10b can be halved by applying the configuration shown in FIG. Also, the cross section of the optical path is 0°5cm x 20
Since it is approximately cm, the volume of the light source section 10b is not a problem either.

Next, FIG. 4 illustrates an example of a liquid crystal shutter used in the present invention. FIG. 4 shows the arrangement of four common electrodes arranged on a common base material 60 when the number of multiplexes is four.1.
2. 3. The portion marked 4 constitutes a micro shutter. A segment 71X pole is provided on the segment base plate (not shown) opposite to this one set. 61, 62,
Reference numerals 83 and 64 represent common electrodes, and in order to reduce electrode resistance, the portions that do not constitute the micro-shutter portion are covered with nickel or the like so as not to short-circuit each other. This also acts as a mask to prevent unnecessary light transmission. The shutter part is a transparent electrode with relatively high sheet resistance.

61 a, 62 a, 63 a, 64 a
Is it common? IE1! This is a terminal for externally leading Ii.

Incidentally, in FIG. 4, if the micro shutters are arranged vertically and the pixel pitch is W, then the pitch is shifted by (1+1/4)W. If this is not done, the required size of the microshutter is W x W, and therefore it will be impossible to arrange the electrodes with a predetermined resistance.

If the micro shutter section is made smaller by shifting by 1/4W, the ruled line becomes a dotted line, for example.

Furthermore, the reason for the shift of at least 1/4 W is to prevent the straight line in the main scanning direction from becoming sawtooth since the micro-shutter is driven in four time divisions.

Furthermore, the electrode arrangement pattern of the shutter section can be variously modified depending on the number of multiplexes. Of course, the liquid crystal shutter device unit including the light source section can be modified in various ways.

〔Effect of the invention〕

As described above, according to the present invention, the light source section is a 4R rule in which metal is arranged on the heated cathode and the phosphor, and the liquid crystal micro-shutter array is appropriately arranged, resulting in a small size, low power consumption, and low cost. The effect of obtaining a reduced liquid crystal shutter device is significant.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a configuration in an embodiment of the present invention. FIGS. 2(a) and 2(b) are perspective views showing an example of the structure of the light source section of the present invention, in which (a) shows a transparent base material having a phosphor;
b) The figure shows the lid base material that maintains the vacuum. FIG. 3 is a configuration diagram showing an example of a configuration for doubling the effective polarization of light from the light source section of the present invention. FIG. 4 is a cross-sectional view showing an example of the configuration of the common electrode of the micro shutter of the shutter section used in the present invention. FIG. 5 is an exploded view showing an embodiment and an application example of the prior art according to the present invention. Thank you for your understanding Seiko Epson Corporation

Claims (2)

[Claims] (1) In a liquid crystal shutter device in which a plurality of micro-shutters are arranged in a predetermined manner in the main scanning direction, a light source projecting light to the liquid crystal shutter device includes a band-shaped phosphor having a width equal to or larger than the shutter width of the liquid crystal shutter device, and at least the phosphor. a transparent base material on which a thin metal film covering the entire surface of the body is disposed; a cathode heated at a voltage sufficiently lower than the applied voltage that accelerates electrons between the material and the metal; the phosphor, the metal, and the cathode. a lid base material that cooperates with the transparent base material to hold the transparent base material in a vacuum, and preferably has a light reflection treatment on the inside and a light transmission prevention treatment on the outside. . (2) In the liquid crystal shutter device according to claim 1, the effective polarization and phase of the light from the light source to the liquid crystal shutter device are 90°.
A liquid crystal shutter device characterized in that the effective polarized light is almost doubled by a separating means for separating into different polarized light, a phase rotation means for making the 90° different polarized light in phase with the effective polarized light, and a combining means.