JPH0367245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a printing device, and particularly to a printing device using a light valve.

[Background of the invention]

A printing apparatus using a conventional light valve is shown in FIG. 1a. A photosensitive drum 1 serving as a photosensitive section is connected to a charger 2
Due to corona discharge, it is uniformly charged with an electrostatic charge. When this is selectively irradiated with light by a liquid crystal light valve consisting of a light source 3, a liquid crystal element 4 having a plurality of light shutter parts, and an imaging element 5 provided as necessary, the irradiation of light is caused by the properties of the photoreceptor. Only the electrostatic charge of the pixel that has been removed disappears, and an electrostatic latent image is formed. Next, when electrically polarized toner is applied to the surface of the photoreceptor by the developing device 7, the electrostatic latent image becomes visible. Next, when the paper 8 sent from the cassette 100 is sent to the transfer device 9, the toner image is transferred onto the paper by the force of an electric field, and then the toner image is fixed to the paper by pressure and heat by the fixing device 10, making it a permanent image. Become. Toner and surface charges remaining on the photosensitive drum 1 are removed by a cleaner 11 and an erasing lamp 12, and the photosensitive drum returns to its initial state. FIG. 1b shows the optical shutter portion of the liquid crystal element 4 shown in FIG. 1a. A substrate 14 with a common electrode 13 formed on its surface and a substrate 16 with a plurality of signal electrodes 15 formed on its surface.
They are assembled one above the other with known liquid crystals of TN type, guest-host type, etc. sandwiched between them. The shaded area) is the optical shutter section. In the printing device, a specific signal electrode 15 is selected from a plurality of groups of signal electrodes 15 according to an information signal for printing, and a voltage is applied to it. The signal electrode 15 selected by this
Since the arrangement of liquid crystal molecules changes in the part, the light emitted from the light source 3 is transmitted through the light shutter part, enters the photosensitive part, and irradiates the corresponding pixel with light. Furthermore, since the liquid crystal molecule orientation does not change in the unselected signal electrode 15 portion, the light from the light source 3 is blocked by the light shutter portion, and the corresponding pixel is not irradiated with light. Note that hereinafter, transmitting or blocking the light from the light source 3 will be simply referred to as control.

FIG. 2a shows a cross-sectional view of the liquid crystal element 4 shown in FIG. 1b. Adjacent signal electrode 15a
and 15b is a constant distance l _e , (usually 6 to 10 μm)
It faces a common electrode 13 which is separated and held at a predetermined potential. Let the distance between the edges of the signal electrodes 15a and 15b be _lg . Now, when the same voltage is applied to the signal electrodes 15a and 15b, the optical shutter section is as shown in the plan view of FIG. 2b.
It extends not only to the width l _e of 5b but also to both sides l _s0 and l _s1 . The inventors have determined that l _s0 is approximately 10 μm, but
It has been confirmed that l _s1 is several times larger than l _s0 .
This is closely related to the electric field distribution within the liquid crystal layer 17. At the edge part A of the signal electrode 15a, the equipotential line 1
8 is largely curved toward the substrate 16, whereas the edge portion B on the side facing the adjacent signal electrode 15b
In this case, the equipotential line 18 is lowered toward the liquid crystal layer 17 side. This phenomenon is explained by the fact that the value of the distance l _g is the thickness of the liquid crystal layer 17, l _e
The closer you get, the more noticeable it becomes. Since the liquid crystal molecules 19 are aligned along the lines of electric force, that is, the normals to the equipotential lines 18, the region where the liquid crystal molecules 19 rise due to the voltage extends to the periphery of the signal electrodes 15a and 15b.

This problem is particularly noticeable in liquid crystals exhibiting a chiral smectic phase, as it is necessary to apply a higher electric field than in nematic liquid crystals.

In the printing device, the light transmitted through the optical shutter section must be separated for each signal electrode 15.

In Figure 3, as an example, the thickness l _e of the liquid crystal layer 17 is 10μ.
This figure shows the change in the spread width l _s1 of the light transmission region around the signal electrode when the distance l _g between adjacent electrodes is changed in the case of m. When l _s1 /l _g is 1/2, the light transmitting regions completely overlap. As can be seen from FIG. 3, when l _g becomes approximately 40 μm or less, a phenomenon occurs in which pixels on the surface of the photoreceptor corresponding to adjacent signal electrodes overlap with each other. However, this value varies depending on the liquid crystal material used and the element structure ( _LE, etc.). Therefore, the distance between adjacent signal electrodes should be set to a certain distance (approximately 40 μm if the liquid crystal layer thickness is 10 μm).
The above needs to be secured. On the other hand, resolution is a parameter that indicates the performance of a printing device, and increasing the distance between adjacent signal electrodes as described above will conversely reduce the pixel area that can be provided between predetermined dimensions, resulting in a decrease in resolution.

Furthermore, in order to perform high-quality printing, it is necessary to arrange the optical shutter portions at a high density, and the electrode pattern becomes dense, resulting in poor yield.

JP-A No. 57-120466 discloses that by time-divisionally driving the optical shutter section, the number of electrodes is significantly reduced and the electrode pattern is not made too tight. As a result, there is a problem that the printing speed becomes N times slower.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a high-quality printing device in which the pattern of electrodes constituting the optical shutter portion is not high-density, and the printing speed is high.

[Summary of the invention]

The present invention that achieves the above object is characterized by a light shutter portion formed by opposing portions of opposing transparent electrodes and a display body held on the opposing portion, and a plurality of light shutter portions formed by the above-mentioned light shutter portions. a light shutter group constituted by a light shutter group, a light valve constituted by a plurality of the light shutter groups, a light source, a photosensitive section, and the light from the light source is controlled by the plurality of light shutter sections; a plurality of pixels formed by the light being incident on the light source, the light from the light source is controlled by the light shutter section, and the direction in which the light is incident on the photosensitive section is determined by the plurality of light shutter groups. The different and adjacent pixels are controlled by light shutter sections of different light shutter groups.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on examples. The same reference numerals as in FIGS. 1 and 2 indicate the same or equivalent parts.

FIG. 4 is a diagram for explaining the principle of the present invention.

FIG. 4a is a schematic plan view of an example of a liquid crystal light valve used in the present invention, and the light valve 6 is composed of two light shutter groups SG1 and SG2. The optical shutter group SG1 includes optical shutter parts S ₁ , S ₃ ,
S ₅ ,...S _2o-1 , optical shutter group SG
2 is composed of optical shutter parts S ₂ , S ₄ , S ₆ , ...S _2o , and the optical shutter parts S 1 , S ₂ of the optical shutter group SG1,
During S ₃ ..., the optical shutter section of optical shutter group SG2
It is arranged so that S ₂ and S ₄ are included. Optical shutter section S ₁ ,
S ₂ ...S _2o are formed by opposing portions of opposing transparent electrodes (not shown) and a support (not shown) held on the opposing portions.

FIG. 4b is a schematic diagram of the entire printing device, and FIG. 4c is a photosensitive member 21 of the photosensitive drum 1 serving as a photosensitive section.
It is a diagram showing the arrangement of the upper pixels e ₁ , e ₂ , . . . e _o .

Light L1 from the light source 3 is controlled by the light shutter sections S ₁ , S ₃ ...S _2o-1 of the light shutter group SG1, and is incident on the photosensitive section to illuminate the pixels e ₁ , e ₃ , ... e _2o-1. form,
Also, the light L2 from the light source 3 is transmitted to the optical shutter group SG2.
are controlled by the optical shutter parts S ₂ , S ₄ ...S _2o ,
The light is incident on the photosensitive section to form pixels e ₂ , e ₄ , . . . e _2o . Light L1, L from the light source 3 incident on the photosensitive section
The direction of 2 is the optical shutter group SG1 and the optical shutter group
It is different from SG2. The drive circuit 20 drives the pixel _e1 ...
Voltage signals V 1 to V _2o that control opening and closing of each optical shutter section S ₁ ... S _2o corresponding to each pixel e ₁ ... e _2o based on an information signal that determines whether or not to irradiate light to _{e 2o .} occurs.

In Figure 4, adjacent pixels (e.g. e ₁ and
e ₂ ) have different optical shutter groups (SG1 and
Since it is controlled by the optical shutter parts (S ₁ and S ₂ ) of SG2), the distance between the optical shutter parts (for example, S ₁ and S ₃ ) becomes large, and the electrode pattern that makes up the optical shutter part is not dense. It disappears.

Furthermore, the light L from the light source that is incident on the photosensitive section
1, the direction of L2 is different between the optical shutter group SG1 and the optical shutter group SG2, so the optical shutter group SG
1 and optical shutter group SG2 can be driven at the same time, and the printing speed becomes faster than in time-division driving. (For example, twice as much as when driving SG1 and SG2 in two time divisions).

A first embodiment of the present invention will be described using FIG.

FIG. 4a shows an example in which a light valve is constructed by liquid crystal elements 4a and 4b that share one substrate.

The liquid crystal element 4a forms a light shutter group SG1,
The liquid crystal element 4b forms a light shutter group SG2.
One common substrate 14 is a plastic film such as a uniaxially stretched polyester film with a thickness of 0.1 mm, the other substrates 16a and 16b are glass plates with a thickness of 0.5 mm, the transparent electrode material is indium oxide, and the signal electrode 15 are formed alternately. However, the lead wire portion of the signal electrode 15 has a three-layer structure of indium nichrome oxide and gold in order to reduce resistance. Signal electrode 15 is 8 pieces/mm, electrode width
l _e is 40 μm, and the distance between adjacent electrodes l _g is 84 μm. Further, the lighting area dimension l _s was set to 2 mm. The display material used was a liquid crystal exhibiting a chiral smectic C phase (e.g.
DOBAMBC) and is sealed with a sealing material 30. Two polarizing plates are attached to both sides of the substrates 14, 16a, and 16b so that their polarization axes are perpendicular to each other. (Omitted in FIG. 5) Such a liquid crystal element 4a,
4b about the center line A-A'.
As shown in Figure b, green color fluorescent lights (10W) 3a, 3 serve as light sources behind the liquid crystal elements 4a, 4b.
b. A cylindrical lens 5, which is an optical coupling element, is provided in front of the liquid crystal elements 4a and 4b. Liquid crystal element 4
Between the signal electrode 15 and the common electrode 13 of a and 4b
The light shutter section applied with the negative voltage of DOBAMBC blocks the light from the light source, but when a positive voltage is applied to the light shutter section, the light passes through this light shutter section and the cylindrical lens 5 As shown in Figure 5c, the focused light is l _e ×l _e (for example, 4μ
m x 40 μm) pixels. The state of a liquid crystal exhibiting a chiral smectic phase such as DOBAMBC with respect to the applied voltage is as follows:
Submicrosecond bistable electro−optic
switching in liquid crystals”Appl.Phys.1
June 1980 etc., and the cylindrical lens 5 is located in the longitudinal direction of the area l _e x l _e of the optical shutter part.
It is provided to narrow down the l _s to the l _e and make the pixel l _{e le} .
Chiral smectic liquid crystals have a fast response speed and can reduce the on/off time of the optical shutter section to 2 msec or less, enabling high-speed printing of 1000 lines/minute. In addition, the pixel group on the photoreceptor surface is 16 dots/mm.
Therefore, the illuminance at each pixel is 15W/ ^m2 , and Se
The illuminance is sufficient to expose the photoconductor, and the resolution is 16.
It is possible to obtain a printing device with a printing speed of 1,000 lines/m and a printing speed of 1000 lines/min. Although this embodiment shows an example using a liquid crystal exhibiting a chiral smectic C phase, the present invention can also be applied to a thermal writing method using a nematic liquid crystal or a liquid crystal exhibiting a smectic A phase, and to displays such as PLZT. can. From the viewpoint of high speed, it is preferable to use a liquid crystal exhibiting a chiral smectic C phase.

In addition, in FIG. 5a, the substrate 14 on the common electrode 13 side
Although the two liquid crystal elements 4a and 4b are used as a common substrate, the substrate 16 on the signal electrode 15 side may be used as a common substrate for the two liquid crystal elements.

Alternatively, a plurality of liquid crystal elements may be attached to a flexible plate.

4 and 5 are examples in which the light valve is configured by two groups of light shutters, but the present invention is not limited to this, and the light valve of the present invention may be configured by three or more groups of light shutters. can also be applied. FIG. 6 is a schematic diagram of a light valve constructed of four optical shutter groups.

As shown in FIG. 6a, the light valve 6 is composed of four optical shutter groups SG1, SG2, SG3, and SG4. The optical shutter group SG1 is operated by optical shutter sections S ₁ , S ₅ , S ₉ , ...S _4o-3 , and the optical shutter group SG2 is operated by optical shutter sections S ₂ , S ₆ , S ₁₀ ...S _4o-2 . Therefore, the optical shutter group SG3 includes optical shutter parts S ₃ , S ₇ ,
The optical shutter group _SG4 is constituted by the optical shutter sections S ₄ , S ₈ , S _{12 ,} . . . S _4o , respectively. The directions of the lights L ₁ , L ₂ , and L ₄ from the light source 3 that are incident on the photosensitive section are different depending on the light shutter groups SG1, SG2, SG3, and SG4, as shown in FIG. 6b, but the angle of incidence is As the difference in the incident angle becomes larger, variations in the amount of light irradiated onto the pixels tend to occur, so it is preferable that the difference in the incident angle be small.

In this embodiment as well, the distance between the optical shutters is increased, there is no need to increase the density of the electrode pattern, and the printing speed is increased.

The optical shutter groups SG1, SG2, SG3, and SG4 are simultaneously driven by a drive circuit (not shown).

In addition, in FIG. 6a, the optical shutter parts S ₁ , S ₂ ,
S ₅ , S ₆ , S ₉ , S ₁₀ , ...S _4o-3 , S _4o-2 are considered as one optical shutter group, and the optical shutter parts S ₃ , S ₄ , S ₇ , S ₈ ,
S ₁₁ , S ₁₂ , ...S _4o-1 , S _4o are regarded as the other optical shutter group, and in each optical shutter group, the time shown in the conventionally known Japanese Patent Application Laid-Open No. 120466/1983 is applied. Divisional driving may also be performed. In this case, in the conventional example, 4
Although it is necessary to perform time-division driving, in this embodiment, two-time division driving is sufficient, and the printing speed becomes faster.

〔Effect of the invention〕

As described above, according to the present invention, the pattern of the electrodes constituting the optical shutter section is not dense;
Moreover, a high-quality printing device with high printing speed can be obtained.

[Brief explanation of drawings]

Figure 1 shows a printing device using a liquid crystal light valve, Figure 2 shows a cross section of a liquid crystal element, Figure 3 shows the relationship between the distance between signal electrodes and the spread of a light spot, and Figure 4. 6 to 6 are diagrams for explaining the main points and embodiments of the present invention. 1... Photosensitive drum, 3... Light source, 4... Liquid crystal element, 5... Imaging element, 6... Light valve, 13
...common electrode, 14...substrate having a common electrode,
15...Signal electrode, 16...Substrate having signal electrode, 17...Liquid crystal layer.

Claims (1)

[Scope of Claims] 1. A light shutter portion formed by opposing portions of opposing transparent electrodes and a display body held between the opposing portions, and a light shutter group constituted by a plurality of the above-mentioned light shutter portions. , a light valve constituted by a plurality of the light shutter groups, a light source disposed on one side of the light valve, a photosensitive section disposed on the other side of the light valve, and light from the light source is transmitted to the plurality of light shutters. a plurality of pixels formed by being controlled by a light shutter section of the light source and incident on the photosensitive section, wherein light from the light source is controlled by the light shutter section and incident on the photosensitive section. The printing apparatus is characterized in that the plurality of light shutter groups have different directions in which the plurality of light shutter groups move, and the adjacent pixels are controlled by the light shutter sections of the different light shutter groups that are driven simultaneously. 2. The printing device according to claim 1, wherein the display body is a liquid crystal exhibiting a chiral smectic C phase. 3. The printing apparatus according to claim 1, wherein one of the opposing transparent electrodes is an electrode held at a predetermined potential. 4. The printing apparatus according to claim 3, wherein the electrode held at a predetermined potential is a common electrode. 5. The printing apparatus according to claim 4, wherein the common electrode is formed on a plastic film substrate.