JPH029651A - Method for driving liquid crystal printing head - Google Patents

Abstract

PURPOSE:To obtain recording of good quality by preventing the generation of printing irregularity by performing the emission of light from a light source in synchronous relation to the driving of a liquid crystal. CONSTITUTION:A capillary tube having He sealed therein is used as a light source lamp to be driven at frequency of 5kHz. Polyimide is respectively applied to a substrate 20 having a signal electrode 24 formed thereto and a substrate 21 having a scanning electrode formed thereto to be subjected to rubbing treatment and said substrates 20, 21 are laminated mutually at an interval of 2mum while a ferroelectric liquid crystal is injected to prepare a liquid crystal element. A liquid crystal printing head is constituted using said liquid crystal element to drive the liquid crystal element. Timing is taken so that the quantity of the light transmitting through the liquid crystal element becomes max. while said quantity of light is measured by a photodiode using the driving clock of a capillary tube to determine the driving condition of the liquid crystal element and the timewise irregulality of the quantity of the transmitted light through the liquid crystal element is measured and the quantity of light free from irregularity is obtained while the output of the photodiode is made constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal printer head used in an electrophotographic printer.

[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.
A printer is known that uses toner to develop the resulting latent image on a photoreceptor onto plain paper. The parts of the printer including the light source, light modulation element, and imaging optical system are
It is called a printer head. A liquid crystal light modulation element used in a printer head is used as a liquid crystal light shutter. In addition, liquid crystal light modulation elements are widely applied to optical logic elements, etc., but all of them have the function of spatially modulating the intensity of incident light. This will be explained using an example.

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, liquid crystal printers using liquid crystal elements are expected to be in great demand, especially due to their low cost, and active development is progressing, and liquid crystal printers using dual-frequency drive liquid crystals have been put into practical use. There is. Furthermore, ferroelectric liquid crystals have been developed as liquid crystals with short response times, and high speeds are being achieved.

A liquid crystal printer head usually includes a light source lamp 31, a liquid crystal element 32, and a rod lens array 33, as shown in FIG. As a light source lamp, a monochromatic fluorescent lamp is often used to prevent out-of-focus printing due to chromatic aberration of the rod lens array. However, in order to make LCD printers thinner, recently, instead of fluorescent lamps, light emitting light by discharge of rare gases such as Ne gas, which can provide the same amount of light as fluorescent lamps and require a smaller tube diameter, has been used. Discharge light sources have come into use. This discharge light emitting type light source is usually called a capillary tube, so it will be referred to as such in the following.

Conventionally, the capillary tube and the liquid crystal element have no particular correlation and are driven independently.

[Problem to be solved by the invention]

Capillary tubes are driven by alternating current discharge rather than direct current discharge in order to prevent damage to the electrodes due to discharge and extend their lifespan. In addition, while fluorescent lamps use the light emitted from the phosphor, capillary tubes excite rare gases etc. to an electronically excited state through electric discharge and directly utilize the emitted light. The luminescence time is determined by the lifetime of the electronic excited state. Normally, the lifetime of the electronically excited state of atoms is on the order of nanoseconds, so when the discharge ends, the light emission also ends on the order of nanoseconds. In the case of AC drive with a voltage waveform as shown in Figure 2(a), Figure 2(b)
As shown in , there is a time period during which no light is emitted while the polarity is reversed, so if the drive of the liquid crystal element is not synchronized, the second
As shown in Figure (C), the transmittance of the liquid crystal element (curve (B))
The timing of the change in the capillary tube and the emission of light from the capillary tube (curve (A)) is not synchronized, and the liquid crystal element becomes transparent when the capillary tube is not emitting light, or the liquid crystal element becomes blocked when the capillary tube emits light. As a result, the light from the capillary tube is not used efficiently, resulting in a wasted amount of light and uneven printing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for driving a small-sized liquid crystal printer head that eliminates the above-mentioned drawbacks, does not cause whiplash in printing even when a capillary tube is used, and can efficiently utilize the amount of light.

[Means to solve the problem]

The driving method of the present invention provides a liquid crystal printer head for an electrophotographic printing apparatus that includes a liquid crystal element that transmits and blocks light emitted from a light source and uses a discharge light emitting type light source as the light source. The configuration is such that the drive is synchronized with the drive of the

[Effect]

Graphs of the drive waveform of the capillary tube and the emission intensity are shown in FIGS. 2(a) and 2(b).

The frequency of this drive waveform is usually fixed. On the other hand, printers print at arbitrary times, but shifting the time to actually start driving the liquid crystal element so that it is synchronized with the driving of the capillary tube is a way of synchronizing it with the driving clock of the capillary tube. It's possible if you just take it. When the drive of the capillary tube and the drive of the liquid crystal element are synchronized, as shown in Figure 1, the light emission of the capillary tube (curve (a)) and the switching of the liquid crystal element (transmittance (curve (b)) ) changes at the same time, when the liquid crystal element transmits light, it is possible to irradiate the photoreceptor with the maximum amount of light without causing any unevenness over time.Therefore, the printed image will be even and uniform. You can get something.

〔Example〕

Hereinafter, the present invention will be explained in detail by giving examples.

A capillary tube filled with He is used as a light source lamp for the liquid crystal printer head shown in Figure 3, and the frequency is 5KHz.
It was driven by. The diameter of the capillary tube is 8 mm, which is half the diameter of a fluorescent lamp that can provide the same amount of light. Further, as a liquid crystal element, a 1/4 duty time division drive type ferroelectric liquid crystal element having a configuration as shown in FIG. Each of the substrates 21 was coated with polyimide, subjected to a rubbing treatment, and bonded together at intervals of 2 μm, and ferroelectric liquid crystal C5-1018 (trade name, manufactured by Chisso Corporation) was injected to create a liquid crystal element. Using such a liquid crystal element,
A liquid crystal printer head is constructed as shown in Fig. 3, and the fourth
The liquid crystal element was driven with the drive waveform shown in the figure. The liquid crystal printer head could be made 8mm thinner. The voltage actually used is Vo"IOV, t=75μs, to"
The time was set to 5 μs.

Using the clock for driving the capillary tube, the amount of light transmitted through the liquid crystal element is measured with a photodiode, and the driving conditions for the liquid crystal element are determined by adjusting the timing to maximize the amount of light transmitted through the liquid crystal element. When measured, the output of the photodiode was constant and a uniform amount of light was obtained. Printing was performed using the obtained capillary tube and the driving conditions of the liquid crystal element, and even printing was obtained.

Although a ferroelectric liquid crystal element is used in this example, a liquid crystal element using nematic liquid crystal may also be used, and the driving frequency of the capillary tube is not fixed at 5 HKz, but can be set under the optimum timing conditions for each frequency. All that is required is to drive the liquid crystal element. [Effects of the Invention] As described above, according to the present invention, it is possible to obtain high-quality records that are caused by uneven printing.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the emission intensity of the capillary tube and the transmittance of the liquid crystal element according to the present invention, and FIGS. 2(a) and (b) are graphs showing the driving voltage of the capillary tube and the emission intensity. Figure 2 (C) is a diagram showing the relationship between the transmittance of the liquid crystal element and the emission intensity of the capillary tube using the conventional driving method.
4 is a diagram showing an example of a drive waveform of a liquid crystal element, and FIG. 5 is a partial perspective view showing an example of a liquid crystal element. 31... Light source lamp, 32... Liquid crystal element, 33...
・Rod lens array.

Claims (1)

[Claims] In a liquid crystal printer head for an electrophotographic printing apparatus, which includes a liquid crystal element that transmits and blocks light emitted from a light source and uses a discharge light emitting type light source as the light source, the light emission of the light source and driving of the liquid crystal element are synchronized. A method for driving a liquid crystal printer head, characterized in that: