JPS63280665A - Liquid crystal printer head - Google Patents

Abstract

PURPOSE:To realize gradation without use of a small-area microshutter by providing a plurality of liquid crystal optical shutter arrays and allowing exposure at the same position on a photosensitive element to occur a plurality of times with the help of the liquid crystal optical shutter arrays. CONSTITUTION:When a static latent image is formed on a charged photosensitive element 19 through exposure in the process of an electrophotographic system, a final print density can be adjusted by controlling an exposure dose, because the potential of the photosensitive element 19 varies according to an exposure dose. That is, a gradation can be expressed. Therefore, liquid crystal optical arrays 15, 16 are provided at printer heads 11, 12 respectively, and exposure is performed a plurality of times at the same position on the photosensitive element 19 to express a gradation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic liquid crystal printer head, and particularly to a printer head that expresses gradations.

[Conventional technology]

Liquid crystal elements have been actively researched and developed as direct-view display elements, and are now widely used. On the other hand, light modulation elements using liquid crystals are also used. For example, the intensity of the light irradiated onto the photoreceptor is modulated using a light modulation element,
An electrophotographic printer is known in which the resulting latent image on a photoreceptor is developed on plain paper using toner. In such a printer, a portion including a light source, a light modulation element, an imaging optical system, etc. of the printer is called a printer head. The liquid crystal light modulation element used in this printer head functions as a liquid crystal light shutter.

In addition, liquid crystal light modulation elements are widely applied to optical logic elements and the like, but all of them use a function of spatially modulating the intensity of incident light.

In recent years, demands for printers such as high speed, high resolution, low price, low noise, and compactness have been increasing, and in response to these demands, non-impact printers such as laser beam printers are becoming widely used.

Under these circumstances, large demand is expected for liquid crystal printers that use liquid crystal shutter arrays, especially due to their low cost, and active development is progressing, and liquid crystal printers that use dual-frequency drive liquid crystals have been developed. . Furthermore, in recent years, ferroelectric liquid crystals have been developed as liquid crystals with high response speeds, and efforts are being made to increase the speed.

Generally, the liquid crystal printer head has the following characteristics as shown in FIG.
Light source lamp 41. It consists of a liquid crystal optical shutter array 42° and a SELFOC lens array 43.

Light from a light source lamp 41 is turned on and off by a liquid crystal light shutter array 42 to form an electrostatic latent image on a photoreceptor 44. However, with such a configuration, only binary values of on and off, that is, white and black, can be expressed in printing.

On the other hand, in order to reproduce shading or gradation in an electrophotographic printer, it is sufficient to apply density modulation or area modulation to the light modulation system, and for example, halftone dot method, which is a type of area modulation, is known.

[Problem that the invention seeks to solve]

Ferroelectric liquid crystal is used as a liquid crystal material for liquid crystal shutters, and its high-speed response has expanded the range of applications of liquid crystal shutters, and they are now being used not only in printers but also, for example, in electrophotographic facsimiles. When considering facsimile applications, it is necessary to reproduce gradations, but if area modulation is to be used, a micro-shutter with a small area that corresponds to the required gradations must be formed.
Technically it will be very difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a liquid crystal printer head using a liquid crystal shutter that can realize gradation without using a small-area micro shutter.

[Means for solving problems]

The present invention is a liquid crystal printer head used in an electrophotographic printing apparatus that exposes a photoreceptor to write an image, and is equipped with a plurality of liquid crystal light shutter arrays to expose the same position on the photoreceptor. It is characterized in that it is performed multiple times using a liquid crystal light shutter array.

[Effect]

In the electrophotographic process, when exposing a charged photoconductor to form an electrostatic latent image, the potential on the photoconductor changes depending on the amount of exposure, so the amount of exposure must be adjusted. This makes it possible to adjust the final print density and express so-called gradations.

In the present invention, gradation can be expressed by providing a plurality of liquid crystal light shutter arrays and exposing the same position on a photoreceptor multiple times.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 is a diagram showing an embodiment of a liquid crystal printer head, which includes two printer heads 11 and 12 having the printer head output structure shown in FIG. Each printer head has a light source lamp 13.14, a liquid crystal light shutter array 1
5.16 and SELFOC lens arrays 17.18, and the light transmitted through the liquid crystal light shutter array 15.16 exposes the same position on the photoreceptor 19.

Usually, the relationship between the exposure amount and the surface potential of a photoreceptor can be represented by a graph as shown in FIG. That is, as the exposure amount increases, the surface potential decreases. The amount of toner adhering to the photoreceptor differs depending on the value of the surface potential of the photoreceptor, and printing can be expressed with shading or gradation.

For example, the exposure amount of the printer heads 11 and 12 in FIG. 1 may be adjusted as shown in FIG. If the amount of light from the lamp is increased, the exposure amounts a0 to a3 shown in FIG. 2 can be obtained by combinations of printer head on and off as shown in Table 1 below.

Table 1 You can select four types of surface potential of the photoreceptor using the combinations shown in Table 1. For example, in the printing state, the exposure amount a0 is black and the exposure amount a
It is possible to express four gradations, such as whitening in the order of In aR+''3.

FIG. 4 is a diagram showing an example of the configuration of a liquid crystal optical shutter array, and a specific example will be further explained. In this liquid crystal light shutter array, a substrate 22 on which a signal electrode 21 is formed and a substrate 24 on which a scanning electrode 23 is formed are arranged to face each other with a spacer interposed therebetween, and a liquid crystal material 25 made by Chisso Corporation is used as a liquid crystal material 25 between them. Filled with ferroelectric liquid crystal C5-1014. Furthermore, polarizing plates 26.27 are bonded to each substrate 22.24. Sixteen scanning electrodes 23 are formed per 1 mm and driven by time-division driving with a 1/4 duty, so that one signal electrode 21 faces four scanning electrodes 23. The signal electrode 21 is connected to a signal electrode drive circuit 28, and the scan electrode 23 is connected to a scan electrode drive circuit 29.
It is connected to the.

Two printer heads having the configuration shown in FIG. 1 were manufactured using such a liquid crystal light shutter array and a LOW and 15W monochromatic fluorescent lamp as a light source lamp, respectively. When each liquid crystal light shutter array was turned on and off to achieve the combinations shown in Table 1 and the surface potential of the photoreceptor was measured, the results were 400V, 300V, 2
00V and 100V, and if these are used for printing, four gradations can be expressed.

In the above embodiment, two printer heads each having a light source lamp are used, but one light source lamp may be shared. FIG. 5 shows an example of such a printer head. This printer head 31 is composed of one common light source lamp 32, two liquid crystal light shutter arrays 33 and 34 shown in FIG. 4, and two selfoc lens arrays 35 and 36. . In such a printer head 31, a liquid crystal light shutter array 33.
Four gradations can be expressed by changing the amount of light transmitted through these liquid crystal light shutter arrays by, for example, changing the liquid crystal material of 34. If the amount of transmitted light is the same, three gradations can be expressed.

In this example, the printer head is configured with two liquid crystal light shutter arrays, but two rows of shutter arrays are formed on one substrate and the amount of light is adjusted using, for example, a neutral density filter. It is also possible to express four gradations.

In the above two embodiments, ferroelectric liquid crystal is used, but TN
A liquid crystal may also be used.

Further, in the above two embodiments, the case where two liquid crystal light shutter arrays are used has been described, but in general, 2n gradations can be expressed by using n liquid crystal light shutter arrays.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a liquid crystal printer head that can express gradations without forming a small-area micro-shutter.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an embodiment of the liquid crystal printer head of the present invention, Fig. 2 is a graph showing the relationship between the exposure amount and surface potential of the photoreceptor, and Fig. 3 is the on/off state of the two printer heads. FIG. 4 is a diagram showing an example of the configuration of a liquid crystal optical shutter array. FIG. 5 is a diagram showing the configuration of another embodiment of the present invention. FIG. 6 is a diagram showing the configuration of a printer head. It is a diagram. 11, 12.31...printer heads 13, 14.
32...Light source lamp 15, 16.33.34...Liquid crystal light shutter array 17
, 1B, 35.36... SELFOC lens array 1
9...Photoreceptor 21...Signal electrodes 22, 24...Substrate 23...Scanning electrode 25... ...Liquid crystal material 26, 27...Polarizing plate representative Patent attorney Yoshiyuki Iwasa Figure 1 aOa1a2 aS Q Light intensity Figure 2 Off Off Off Off To printer 71'11 To printer 12 Figure 3 4 - 32 □1 Fig. 5 41 light 1 42'a 43 sets 44 Fig. 6 To printer 71'' Window Kokyu

Claims (1)

[Claims] (1) A liquid crystal printer head used in an electrophotographic printing device that exposes a photoreceptor to write an image, and is equipped with a plurality of liquid crystal light shutter arrays and exposes the same position on the photoreceptor using the liquid crystal printer head. A liquid crystal printer head characterized in that a light shutter array is used to print multiple times.