JPS63280278A - Liquid crystal printer head - Google Patents

Abstract

PURPOSE:To express gradation without forming a microshutter with a small area by providing a liquid crystal printer head with plural liquid crystal optical shutter arrays including color filters having respectively different quantities of transmitted light. CONSTITUTION:The printer head is provided with plural liquid crystal optical shutter arrays 11, 12 including the color filters having respectively different quantities of transmitted light. The spectral sensitivity of a photosensitive body 13 is different in accordance with the wavelength of light, even when light with the same intensity is radiated, the surface potential of the photosensitive body is different in accordance with the wavelength of the radiated light. The surface potential of the photosensitive body can be selected and gradation can be expressed by changing the wavelength of radiated light. Thereby, the gradation can be expressed by using a multiple color emitting light source lamp 14 and arranging plural liquid crystal optical shutter arrays 11, 12 provided with color filters.

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 31. It consists of a liquid crystal light shutter array 32° and a SELFOC lens array 33.

Light from a light source lamp 31 is turned on and off by a liquid crystal light shutter array 32 to form an electrostatic latent image on a photoreceptor 34. 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 to be solved by the invention 3 Ferroelectric liquid crystal is used as the liquid crystal material of the liquid crystal shutter, and its high-speed response has expanded the range of applications of the liquid crystal shutter, and it has been used not only for printers but also for example for electrophotographic facsimiles. I'm about to be killed. 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 characterized by comprising a plurality of liquid crystal light shutter arrays each having a color filter that transmits a different amount of light. It is said that

[Effect]

In the electrophotographic process, a charged photoreceptor is exposed to light to form an electrostatic latent image, but the final print density can be adjusted by adjusting the surface potential of the photoreceptor, and the so-called gradation It will be possible to express. As shown in Figure 5, the spectral sensitivity of a photoreceptor differs depending on the wavelength of light, and even if the same intensity of light is irradiated, the surface potential of the photoreceptor will differ depending on the wavelength of the irradiated light. By changing the wavelength of the irradiated light, the surface potential of the photoreceptor can be selected and gradations can be expressed.

The present invention uses a multicolor light source lamp and provides a plurality of liquid crystal light shutter arrays equipped with color filters, thereby making it possible to express gradations.

〔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 a multicolor light source lamp 14, two liquid crystal light shutter arrays 11, 12 each having separate color filters,
It is equipped with SELFOC lens arrays 15 and 16.

Note that in the figure, 13 is a photoreceptor.

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 varies depending on the value of the surface potential of the photoreceptor, resulting in printing with shading or gradation.

When the photoreceptor 13 shown in FIG. 1 has the spectral sensitivity shown in FIG. 450 nm for the optical shutter array 12
Attach a color filter with maximum transmittance nearby.

The liquid crystal light shutter array 11 calculates an effective exposure amount that takes into account the spectral characteristics of the photoreceptor after passing through the liquid crystal light shutter array.
．． 12 on.

The OFF state is expressed in a graph as shown in FIG. Therefore, the exposure amounts shown by a, to a in FIG. 2 can be obtained by the combinations of ON and OFF of the liquid crystal optical shack array as shown in Table 1.

Table 1 Four types of surface potentials of the photoreceptor can be selected using the combinations shown in Table 1. For example, in the printing state, the exposure amount, a.

It is possible to express four gradations, such as black and white in the order of exposure amount aIn aRr a2.

In the above, four gradations are expressed using the spectral sensitivity of the photoconductor, but even if the spectral sensitivity of the photoconductor is almost equal at 450nm and 590nm, the emission intensity of the light source is 450nm and 590nm.
The transmittance of the filter is 450nm and 59nm.
If the difference is 0 nm, four gradations can be expressed.

FIG. 4 is a diagram showing an example of the configuration of a liquid crystal light shutter array, in which FIG. 4(a) is a partially cutaway perspective view, and FIG. 4(b) is a cross section taken along line A-A' in FIG. 4(a). It is a diagram. A specific example will be further explained with reference to FIG.

In this liquid crystal light shunter array, the scanning electrode 25 is 1 mm thick.
There are 16 electrodes per signal electrode 24, and each signal electrode 24 is shaped to face four scanning electrodes because it is driven by time-division driving with a 1/4 duty.

The signal electrode 24 is connected to a signal electrode drive circuit 26, and the scan electrode 25 is connected to a scan electrode drive circuit 27.

On the signal electrode 24, a color filter 30 is coated and an electrode substrate coated with polyimide is rubbed as an alignment film 29. Substrates 20 and 21 are bonded at intervals of 2 μm through spacers 28, and nitrogen is used as a liquid crystal material 23. It is filled with ferroelectric liquid crystal C5-1014 manufactured by Kogyo Corporation. moreover,
This liquid crystal light shutter array is sandwiched between two polarizing plates 22.

In the liquid crystal light shutter array having the above-described configuration, one of the color filters 30 contains Lanyl Red CG (Lanyl RedGG), which is a red filter pigment.
(manufactured by Sumitomo Chemical Co., Ltd.), and the other side is coated with Kayanolcyanine 6B (Kaya
nol cyanine 6B) (manufactured by Nippon Tohokusha)
By using a fluorescent lamp that emits two wavelengths of blue and red as a light source,
A liquid crystal printer head having the configuration shown in FIG. 1 was manufactured. It is also assumed that the spectral sensitivity of the photoreceptor 13 is as shown in FIG. When the surface potential of the photoreceptor was measured by combining the on and off states of the two liquid crystal optical shutter arrays, it was 400V.

It became 300V, 200V, and 100V. If this is used for printing, four gradations can be expressed.

In this embodiment, the liquid crystal printer head is formed by two liquid crystal light shutter arrays, but two rows of liquid crystal light shutter arrays may be formed on one substrate. It goes without saying that dyes other than those shown in this example can also be used.
Furthermore, although ferroelectric liquid crystal is used in this example,
The printer head may be manufactured using a liquid crystal optical shutter array using TN liquid crystal.

In the above embodiment, the case where two liquid crystal light shutter arrays are used has been described, but in general, 2'' gradation 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 microshaft.

[Brief explanation of the drawing]

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 a diagram showing the configuration of two liquid crystal light shutter arrays. . Graph showing the amount of transmitted light in the off state, Figure 4 is a diagram showing an example of the configuration of a liquid crystal optical shutter array, Figure 5 is a graph showing the spectral sensitivity of the photoreceptor, and Figure 6 is a diagram showing the configuration of the printer head. . 11, 12...Liquid crystal light shutter array 13...
Photoreceptor 14...Light source lamps 15, 16...Selfoc lens arrays 20, 21
... Substrate 22 ... Polarizing plate 23 ... Liquid crystal material 24 ... Signal electrode 25 ... Scanning electrode 30 ... Color filter

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 characterized by being equipped with a plurality of liquid crystal light shutter arrays each having a color filter with a different amount of transmitted light. LCD printer head.