JP2527394Y2 - LCD printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention particularly relates to a liquid crystal printer that performs optical writing on a photoconductor in accordance with print data.

[Conventional technology]

The liquid crystal printer controls the opening and closing of a large number of micro shutters according to print data, so that the light of the light source is transmitted through the open micro shutter to irradiate the photoreceptor, and the liquid crystal shutter performs exposure to the photoreceptor in accordance with the print data. Have. A photoreceptor exposed by such a liquid crystal shutter usually needs a constant light amount (optimal light amount).

However, due to the variation of the micro shutter (liquid crystal shutter) that transmits the light of the light source, the amount of light emitted to the photoconductor is different even with the same light source. Therefore, in order to output the optimal light quantity to the photoconductor, conventionally, the voltage applied to the light source is varied, the light output quantity from the light source is controlled, and the optimal light quantity is output to the photoconductor. As a light source, an incandescent light source is excellent in various aspects.

[Problems of the prior art]

In a conventional liquid crystal printer, as described above, the amount of light emitted to the photoconductor is adjusted only by controlling the voltage applied to the light source. However, the applied voltage may be lower than the rated value of the light source. In such a case, the color temperature is lower than when the light source is used at the rated value. Cannot be emitted to the photoconductor. Further, since the temperature of the light source is lowered, a so-called blackening phenomenon in which tungsten vapor adheres to the inner wall of the light source is caused, and the amount of light emitted from the light source or the life is shortened.

Further, even when the voltage applied to the light source is higher than the rated value, there is a problem that the life of the light source is shortened.

[Purpose of the invention]

An object of the present invention is to provide a liquid crystal printer capable of irradiating a photoreceptor with an optimal amount of light and preventing a light source from being blackened in view of the above-mentioned conventional disadvantages.

[Points of the invention]

In order to achieve the above object, the present invention provides a liquid crystal printer which selectively transmits light from a light source by opening and closing a micro shutter and writes light on a photosensitive member, and a light receiving element for detecting an amount of light transmitted through the micro shutter. A drive voltage control unit that controls a drive voltage of the light source according to the amount of light detected by the light receiving element, and a determination unit that determines that the drive voltage of the light source has reached an upper limit or a lower limit of a predetermined range.
The opening / closing control voltage level to be applied to the micro-shutter when the drive voltage is detected to be the upper limit value or the lower limit value of the predetermined range by the determination means is higher when the upper limit value, and lower when the lower limit value. Voltage level changing means for changing the voltage level.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a sectional view of the liquid crystal printer of one embodiment. The liquid crystal printer feeds a photosensitive drum 1, a charger 2, a print head 3, a developing unit 4, a transfer unit 5, a cleaner 6, which are sequentially arranged near the peripheral surface of the photosensitive drum 1, and a paper feed cassette 7. It is configured by a paper transport mechanism such as a slip roll 9, a standby roll 10, and a fixing roll 11 for transporting the paper P carried out by the rollers 8. The charger 2 is a device that applies an initial charging voltage to the photosensitive surface of the photosensitive drum 1 that rotates in the direction of arrow A. The print head 3 is a device that performs exposure based on print data to the photosensitive surface. Is a device for converting the electrostatic latent image formed on the photosensitive surface by the above-described exposure into a toner image,
The transfer device 5 is a device that transfers the toner image onto a sheet P conveyed in the direction of arrow B. The cleaner 6 is a device that removes toner remaining on the photosensitive surface, and the fixing roll 11 is a device that conveys the sheet on which the toner image has been transferred and thermally fixes the toner image on the sheet.

Inside the print head 3, there are disposed an optical transmission rod 3a, a liquid crystal shutter 3b composed of two glass substrates 12, 13 and the like, and an imaging lens array 3c, and the optical transmission rod 3a and the like are long in the direction perpendicular to the paper surface. It has been extended. A halogen lamp (light source) to be described later is provided at one end of the light transmission rod 3a, and light from the halogen lamp is applied to the liquid crystal shutter 3b from above through the light transmission rod 3a. The liquid crystal shutter 3b is
It has a large number of micro shutters arranged in a row, and the micro shutters are driven to open and close according to a selection signal and a recording signal described later, and light transmitted through the open micro shutter is transmitted to the photosensitive surface via the imaging lens array 3c. Irradiation (exposure).
The liquid crystal shutter 3b is provided with a heater 3d for heating the liquid crystal shutter to a predetermined temperature, and a light receiving element 22, which will be described later, is provided at one end of the imaging lens array 3c.

FIG. 3 is an enlarged view of a part of the liquid crystal shutter 3b. The liquid crystal shutter 3b has a structure in which a liquid crystal agent (not shown) is sealed between two transparent glass substrates. Two common electrodes C ₁ and C ₂ are formed on the substrate 12 (see FIG. 2), and many signal electrodes S ₁ , S ₂ ,... Are formed on the lower glass substrate 13 (also see FIG. 2). _Sn is formed. Common electrodes C _1, C _2, the signal electrodes _{S 1, S 2, ...... S} n is configured by forming a metal film to leave a portion of the transparent conductive film on the transparent conductive film (hatched portion) is , two electrodes _{C 1, C 2, S 1} , S 2, a transparent conductive film only overlapping portions of the ...... S _n micro shutter 14a, is used as 14b. Although not shown in FIG. 3, a micro shutter which is set to a normally open state is formed at an end of the liquid crystal shutter 3b. The common electrode C ₁ 4
Selection signal waveform shown in FIG. (A) is output for each write period Tw, the common electrode C ₂ is output selection signal (not shown) shifted the 1/2 Tw phase of the waveform of FIG. (A). Also signal electrode
S _1, S _2, the ...... S _n on the recording signal or off the recording signal shown in FIG. 4 (b) or (c) is output. Then, for example, the selection period of the in order to set the micro-shutter 14a in the open state FIG. (A) (Tw / 2 time period of the first half), and outputs a selection signal of FIG (a) to the common electrode C _1, the outputs an oN recording signal shown in FIG. (b) to the signal electrodes S _1, the micro-shutter 14a
In order to set the micro-shutter 14a to the open state by applying a signal (FIG. 10 (d)) in which both signals are superimposed on each other, for example, to set the micro-shutter 14a 'to the closed state, as shown in FIG. selection period (Tw / 2 time period of the first half), and outputs a selection signal of FIG (a) to the common electrode C _1, and outputs an oFF recording signal shown in (c) to the signal electrodes S _2, the micro-shutter 14
The micro-shutter 14a 'can be set to the closed state by applying a signal (FIG. 9 (e)) in which both signals are superimposed on a'. As for the micro-shutter 14b, and outputs a different selection signal drawing to the common electrode C ₂ and (a) of 180 ° phase, a superimposed signal of on or off the recording signal is output for example to the signal electrodes S ₁ micro By applying the voltage to the shutter 14b, the micro shutter 14b can be set to the open or closed state. In addition, only the above-described selection signal and ON recording signal are output to a micro shutter (not shown) provided at the end of the liquid crystal shutter 3b and always set to the open state. Incidentally, f _H contained in the signal of FIG. (A) ~ (e) shows a high-frequency portion, f _H 'represents the f _H and phase difference of 180 ° radio frequency unit, f _L
Indicates a low frequency part. And this micro shutter 14a
(14a ') and 14b are emitted light amounts shown in FIGS.
Signal level (voltage level) of the selection signal and the on or off the recording signal shown in (c) can be varied by changing the V _D. That is, the emission light intensity I from the micro shutter in the open state shown in the characteristic curve D by increasing the voltage level V _D as shown in FIG. 5 increases, the amount of light emitted from the micro-shutter closed state shown in characteristic curve E is reduced I do.

Also, quite counteracts the above by reducing the voltage level V _D.

FIG. 1 shows the common electrodes C ₁ , C ₂ and the signal electrodes S ₁ , S ₂ ,
...... a drive control circuit for outputting a selection signal and a recording signal to S _n, is a circuit block diagram showing a drive voltage control circuit for outputting a driving voltage to the halogen lamp (light source) 19 described above. The common electrodes C ₁ and C _{2 of the} liquid crystal shutter 3b and the signal electrodes S ₁ , S ₂ ,.
... selection signal and the on recording signals by the LCS driving circuit 16 to S _n, off the recording signal is output. LCS driving circuit 16 is a common electrode C ₁ at the voltage level V _D output on or off the recording signal outputted from the drive signal generating circuit 17 from the driving power source circuit 18, C _2, the signal electrodes S _1, S _2, ... ... it is a circuit to output to S _n. Further, the output level of the drive power supply circuit 18 is variable as described later.

The halogen lamp 19 that irradiates the light transmission rod 3a with light is driven by a lamp drive circuit 20. The lamp drive circuit 20 is controlled by a dimming signal from the lamp dimming circuit 21. Further, the amount of light emitted from the halogen lamp 19 is transmitted through the micro-shutter set in the above-described normally open state via the light transmission rod 3a, and is configured by a phototransistor provided at a side end of the imaging lens array 3c. The light is detected by the light receiving element 22. The light detected by the light receiving element 22 is output from the light receiving element 22 to the sensor amplifier circuit 23 as a change in current. The sensor amplifier circuit 23 outputs a control signal to the lamp dimming circuit 21 according to the supplied current value.

In the liquid crystal printer 3b configured as described above, the control operation for giving the optimum amount of emitted light to the photosensitive drum 1 will be described below with reference to the flowchart of FIG. 6 and the characteristic diagram of FIG.

Seventh characteristic H ₁ to H ₃ shown in figure shows the be applied to the emission light intensity is different in the halogen lamp 19 to the same voltage by the variation of the light transmittance of the liquid crystal shutter 3b. That is,
Conversely, in order to obtain the optimum output light amount I _0, as shown in FIG. 3, V ₁ , V ₂ ,
It must be applied to the halogen lamp 19 a voltage different from each of V _3. However, V ₁ to the halogen lamp 19
Add applied voltage ~V ₃ If for this voltage V ₁ ~V ₃ is a conventional problem occurs when (in the example, the present embodiment 19V～21V) rated value of the halogen lamp 19 is outside, in the present embodiment The processing according to the flowchart of FIG. 6 is performed.

First, an initial setting process such as setting the liquid crystal shutter 3b to a predetermined temperature by the heater 3d (step (hereinafter referred to as S) 1)
I do. At this time, the initial applied voltage of the halogen lamp 19 is
Set to 20V. Optimum light amount I makes a determination of whether are the same and the optimum amount of light I ₀ (S2). This determination is made by the lamp dimming circuit 21 based on data on the amount of received light obtained by irradiating the light receiving element 22 with the light emitted from the halogen lamp 19 through the micro shutter (not shown) set in the open state described above. Done. Then, if different from the amount of emitted light I is optimum light emission amount I ₀ of the light receiving element 22, performs the (I = unless I _0), further emission light intensity I is best quantity I ₀ is less than determines whether or not (S3 ). If I <I _{0 according} to this determination (S3), a dimming signal is output from the lamp dimming circuit 21 to the lamp drive circuit 20, and the voltage V _L0 applied to the halogen lamp 19 is output.
Is increased every 0.1 V (S3 is Y, S4). Characteristics H ₃ of FIG. 7 and shows the case may be when the increase to continue for example applied voltage V ₃ the voltage applied sequentially halogen lamp 19 to obtain an optimum amount of light I ₀ from the liquid crystal shutter 3b. But,
If the applied voltage V _L0 exceeds the above-mentioned upper limit of 21 V before obtaining the optimum light quantity I ₀ (S5 is Y), the voltage applied to the halogen lamp 19 is not further increased, and thereafter, An instruction signal (not shown) is output to the drive power supply circuit 18 to increase the voltage output level output from the drive power supply circuit 18,
The voltage level V _D of the above selection signal and the recording signal from the S driving circuit 16 is output to the liquid crystal shutter 3b is increased by 0.1 V (S6). When the output voltage of the selection signal and the recording signal is increased while the voltage applied to the halogen lamp 19 is kept constant, the voltage changes as shown by the characteristic D in FIG. Therefore, increasing the amount of light emitted from the liquid crystal shutter 3b by gradually increasing the voltage level V _D of the selection signal and the recording signal outputted from further LCS driving circuit 16, the optimum light intensity I to the photosensitive surface of the photosensitive drum 1 _It can be set to emit ₀ .

On the other hand, if the output light amount I is larger than the optimum light amount I ₀ in the determination (S ₃ ) (I> I ₀ ), a dimming signal is output from the lamp dimming circuit 21 to the lamp drive circuit 20 and the halogen lamp 19
The voltage V _L0 applied to is reduced by 0.1 V (S3 is N, S
7). An example of this case is the seventh case of the characteristic H ₁ or H ₂ when Shimese in FIG reduces the voltage applied to the halogen lamp 19, for example, when the applied voltages V ₁ or V ₂ crystal shutter 3b
It is possible to obtain an optimum amount of light I ₀ from. However, also in this case, if the applied voltage V _L0 (V ₁ , V ₂ ) becomes smaller than the above-mentioned lower limit of 19 V (S8 is Y) before obtaining the optimum light amount I ₀ , the halogen lamp 19 is no longer used. without lowering the voltage applied to perform control to reduce the voltage level V _D output from the driving power source circuit 18 sends an instruction signal to the drive power supply circuit 18, the aforementioned output from the LCS driving circuit 16 to the liquid crystal shutter 3b the voltage level V _D of the selection signal and the recording signal is decreased by 0.1 V (S9).

Therefore, the amount of light emitted from the liquid crystal shutter 3b as shown in Fig. 5 can be gradually obtain optimum light intensity I ₀ of the reduced to the photosensitive drum 1.

As described above, in this embodiment, the optimum light amount I ₀ to the photosensitive drum 1 is
First, the applied voltage V _L0 to the halogen lamp 19 is varied. When the applied voltage V _L0 matches the upper limit or the lower limit of the rated value which does not cause a problem in the characteristics of the halogen lamp 19, the micro shutter is operated. By changing the drive voltage for driving the micro shutters 14a and 14b (the liquid crystal shutter 3
from b) is intended to obtain light of optimum quantity I ₀ to the photosensitive surface.

In the present embodiment, the drive voltage V _L0 of the halogen lamp 19 and the voltage level V _D of the selection signal and the recording signal are applied by increasing or decreasing by 0.1 V, but the variation width must be limited to every 0.1 V. However, it may be changed continuously. Further, the light source is not limited to the halogen lamp 19.

[Effect of the invention]

As described above in detail, according to the present invention, it is possible to perform the optimal output control of the amount of emitted light to the photoconductor within the range of the rated value of the voltage applied to the light source, thereby preventing blackening of the light source and lowering of the color temperature. .

Further, since the photoreceptor can obtain light having an appropriate wavelength, an electrostatic latent image having a predetermined potential can be reliably formed.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram in a liquid crystal printer of one embodiment, FIG. 2 is a cross-sectional view of the liquid crystal printer of one embodiment, and FIG. 3 is a configuration diagram of a part of a liquid crystal shutter in the liquid crystal printer of one embodiment. 4 (a) to 4 (e) are explanatory diagrams of signals for driving a micro shutter, FIG. 5 is a view showing emission light characteristic of a liquid crystal shutter, and FIG. 6 is a flowchart showing an operation of the liquid crystal printer of one embodiment. FIG. 7 is a graph showing emission light amount characteristics with respect to a voltage applied to a halogen lamp. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Charger, 3 ... Print head, 3a ... Optical transmission rod, 3b ... Liquid crystal shutter, 4 ...
Developing device, 5 ... Transfer device, 11 ... Fixing roll, 14a, 14b ...
... micro shutter, 16 ... LCS drive circuit, 18 ... drive voltage circuit, 19 ... halogen lamp, 20 ... lamp drive circuit, 21 ... lamp dimming circuit, 22 ... light receiving element.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-96637 (JP, A) JP-A-58-115412 (JP, A) JP-A-63-5970 (JP, A) JP-A-63-966 289570 (JP, A) JP-A-58-78120 (JP, A) Jpn.

Claims (1)

(57) [Scope of request for utility model registration] 1. A liquid crystal printer for selectively transmitting light from a light source by opening and closing a micro shutter and writing light on a photosensitive member, wherein: a light receiving element for detecting the amount of light transmitted through the micro shutter; Drive voltage control means for controlling the drive voltage of the light source in accordance with the amount of light to be emitted; determining means for determining that the drive voltage of the light source has reached an upper limit value or a lower limit value in a predetermined range; Voltage level changing means for changing an open / close control voltage level applied to the micro-shutter when the voltage is detected to be the upper limit value or the lower limit value of the predetermined range, when the upper limit value is high, and when the lower limit value, the open / close control voltage level is low. A liquid crystal printer comprising: