JPH085474Y2 - Liquid crystal printer process setting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a process setting device of a liquid crystal printer using a liquid crystal shutter as an optical writing head.

[Prior art]

A liquid crystal printer controls the opening and closing of a number of micro shutters provided on a liquid crystal shutter panel according to image information to be optically written, and irradiates light onto a photoconductor from a light source that has passed through the micro shutters in an open state. A device that prints an image on paper according to a process.

In such a liquid crystal printer, a large number of micro shutters provided on the liquid crystal shutter panel cause light leakage even when the light from the light source is irradiated even in the closed state. The amount of the leaked light varies depending on the liquid crystal shutter panel, depending on the material of the liquid crystal agent in the panel. Normally, when showing the variation in the amount of light leakage for each liquid crystal shutter panel, the ratio of the light amount when the micro shutter is open (on light amount) and the light amount when it is closed (off light amount), that is, the on light amount / off light amount is expressed by contrast (CR) Show. For example, the ON light intensity is 1.0 μJ / cm ² and the OFF light intensity is 0.3 μJ / c.
The CR is 3.3 when m ² is set, and the CR is 2.38 when the ON light amount is 1.0 μJ / cm ² and the OFF light amount is 0.42 μJ / cm ² .

Conventionally, in order to prevent such variations in CR among liquid crystal shutter panels from causing variations in the photoreceptor surface potential V _H formed on the photoreceptor due to light leakage when the micro shutter is closed, the following process settings are performed. Is being done.

This process setting will be described with reference to the light attenuation characteristic and the developing characteristic shown in FIG. First, the liquid shutter panel is irradiated with light, the micro shutter is turned on, and the light amount of the light source is set so that the on light amount becomes 1.0 μJ / cm ² while measuring the on light amount. Next, the micro shutter is turned off and the amount of off light is measured. Further, the photoconductor potential V _{H with} respect to the amount of off light described above.
In order to set the target value of 400V to 400V, if the OFF light intensity is 0.3μJ / cm ² (LCD shutter panel with CR 3.3),
From the figure, an initial charging voltage V _S 650V at which the surface potential V _H of the photoconductor is 400 V with respect to the amount of off light 0.3 μJ / cm ² is set (light attenuation curve A).

Similarly, when CR is 2.38 as described above, similarly, the corresponding ON light amount is set to 1.0 μV / cm ² and the OFF light amount is measured, and for example, the OFF light amount is 0.42 μJ / cm ^{2 from} the value of the photoconductor. 750 V is set as the initial charging voltage V _S such that the surface potential V _{H of the above} becomes 400 V (light attenuation curve B).

[Problems of conventional technology]

In the conventional initial charging voltage V _S setting process for the photoconductor as described above, the surface potential V _H of the photoconductor corresponding to the OFF state is 4
Although it is set to 00V, there is a variation in CR between liquid crystal shutter panels, which causes a variation in the photoreceptor surface potential V _L when the micro shutter is in the open state. That is, as shown in FIG. 5, the values of V _L differ from the light attenuation curves A and B for the ON light amount of 1.0 μJ / cm ² . Further, the print density (PD) differs when the photoconductor potential _VL is different.

FIG. 5 shows the development characteristics in the case of reversal development, and the bias voltage has a relationship of a <b <c. As shown at the intersections of the developing characteristics a, b, and c and the surface potential V _L of the photoconductor shown in the figure, there is a difference in print density. Particularly in this example, it can be seen that there is a difference in print density at the intersection points a'and a "between the developing characteristic a and the surface potential V _L of the photosensitive member. Therefore, the ON light amount is set to a constant value, for example, 1 μJ / cm ^2. Even if the initial charging potential V _S is set so that the surface potential V _H according to the off-light amount becomes constant,
In the case of liquid crystal shutter panels having different CRs, the surface potential _VL is not constant and the print density varies.

[Purpose of device]

In view of the above-mentioned conventional drawbacks, the present invention provides a photoconductor surface potential V _H corresponding to the opening of the micro shutter and a photo-sensing corresponding to the closing of the micro shutter with respect to the variation of the contrast (CR) of the liquid crystal shutter panel as the optical writing head. It is an object of the present invention to provide a process setting device for a liquid crystal printer, which enables the body surface potential V _L to be set constant.

[Key points of device]

In order to achieve the above-mentioned object, the present invention selects the light of the light source by exposing the photoconductor, a charging means for charging the surface of the photoconductor, a light source for exposure, and opening or closing according to a print signal. A liquid crystal shutter that transmits the light to form an electrostatic latent image on the photoconductor, a developing unit that adheres toner to a low potential portion of the electrostatic latent image to perform reversal development, and a toner image formed by the developing unit. In a process setting device of a liquid crystal printer including a transfer unit that transfers to a sheet, a light amount measuring unit that measures the transmitted light amount when open and the transmitted light amount when closed by driving the liquid crystal shutter to open and close the liquid crystal shutter,
Calculation means for calculating the contrast between the open light quantity and the closed light quantity based on the output of the light quantity measuring means, and data of the storage means for storing the light quantity and the initial charging voltage corresponding to the contrast based on the calculation result of the calculation means. According to the setting means for setting the emitted light amount of the light source and the charging ability of the charging means, the surface potential of the photoconductor when the liquid crystal shutter is opened and closed regardless of the variation in the contrast of the liquid crystal shutter. It is characterized in that each is made constant.

[Example of device]

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

FIG. 2 is a schematic configuration diagram showing an example of a liquid crystal printer including a process setting device according to the present invention. In the figure,
The photoconductor drum 1 is rotatably supported at a substantially central portion and is rotationally driven in a direction of an arrow at a peripheral speed of 5 cm / sec. In the vicinity of the peripheral surface of the photoconductor drum 1, light from the charger 2 and the lamp 3a that uniformly charges the peripheral surface of the photoconductor drum 1 to a predetermined polarity to the initial charging voltage V _S along the rotation direction thereof. The micro shutter in the liquid crystal shutter panel 3b is opened / closed to transmit or block, and the transmitted light is radiated to the surface of the photosensitive drum 1 through the imaging lens 3c, so that the surface of the photosensitive drum 1 has a surface potential V _H or V _L ( A print head 3 for forming an electrostatic latent image), a developing device 4 for rubbing the developing roller 4a on the formed electrostatic latent image to form a toner image, a transfer device 5 for transferring the toner image to the sheet P, and A cleaner 6 and the like for removing the toner not transferred and remaining are provided. The charger 2 is a discharge wire.
The discharge wire 2a is connected to the high-voltage generator 7, and the grid 2c is connected to the grid voltage adjusting circuit 8. The high voltage generator 7 is a device for supplying a predetermined high voltage to the discharge wire 2a, and the discharge wire 2a supplies a corona discharge current to the surface of the photosensitive drum 1 by this voltage. The grid voltage adjusting circuit 8 is a circuit that adjusts the voltage supplied to the grid 2c according to the output signal of the potential setting unit described later.

FIG. 1 is a block diagram of a process setting device of this embodiment including the grid 2c and the grid voltage adjusting circuit 8 described above. In the figure, 3b is a liquid crystal shutter panel in which the above-mentioned many micro shutters are arranged, and 3a is the above-mentioned lamp that irradiates the liquid crystal shutter panel 3b with light.
Reference numeral 11 denotes a head drive circuit that opens and closes a large number of micro shutters provided on the liquid crystal shutter panel 3b.
Reference numeral 12 denotes an optical sensor such as a phototransistor, which is configured to turn on the above-mentioned lamp 3a and detect the amount of transmitted light or the amount of leaked light of a micro shutter which is arranged immediately above the optical sensor 12 and is driven to be opened or closed. The light amount detected by the above-mentioned optical sensor 12 is converted into a voltage value and input to the data processing circuit 13,
The circuit calculates the contrast (CR) by comparing the light amount when the micro shutter is opened and the light amount when the micro shutter is closed based on this voltage value data. Further, in the data processing circuit 13, as will be described later, data for setting a predetermined light amount and an initial charging voltage V _S corresponding to CR data is stored.
The light amount data corresponding to the CR data calculated from the above calculation result is output to the light control circuit 14, and the control data of the initial charging voltage is output to the grid voltage adjustment circuit 8 described above. The optical sensor 12 and the data processing circuit 13 form a potential setting section 16. The dimming circuit 14 outputs a light amount control signal to the ballast 15 based on the above light amount data,
15 adjusts the amount of light emitted from the lamp 3a based on this control signal.

Further, the grid voltage adjustment circuit 8, based on the control data of the initial charging voltage of the above, the initial charge voltage of the photosensitive drum 1 is configured to output the such voltage becomes a predetermined V _S to the grid 2c.

In the process setting device of the liquid crystal printer having the above-mentioned configuration, the setting operation using the light amount data and the charging voltage adjustment data for the CR stored in the data processing circuit 13 will be described.

FIG. 3 is a diagram showing a part (first quadrant, second quadrant) of the quaternary chart for explaining the above-described operation, and the horizontal axis of the first quadrant is from the print head 3 to the photosensitive drum 1. Shows the amount of exposure to the surface of. However, in this embodiment, the head drive circuit 11
Is driven, the micro shutter is opened, and the lamp 3a is turned on, the light intensity on the surface of the photosensitive drum 1 is the maximum value.
It is 500 μw / cm ² . Therefore, as described above, the photosensitive drum 1
The peripheral speed due to the rotation of is 5 cm / sec, and if the length of the micro-shutter in the sub-scanning direction is 100 μm, the exposure amount irradiated on the photoconductor drum 1 is The maximum is 1 μJ / cm ² .

Further, development characteristics H, I, and J are development characteristics when the development bias voltage (V _B ) is 380V, 300V, and 220V, respectively. The photoconductor surface potential V _H is, for example, a voltage indicating that the potential is attenuated when light (light leakage) that has passed through the closed micro shutter is applied to the photoconductor drum 1 having the initial charging voltage V _S. , V _L is a voltage indicating that the potential is attenuated when the light (exposure) transmitted through the open micro shutter is irradiated.

First, using the liquid crystal shutter panel 3b (print head 3) in which the amount of light leakage is maximum, that is, the head contrast CR is minimum (for example, CR = 2.38), the initial charging voltage V _S and the photoconductor surface potentials V _H and V _{L are used.} To set. For this setting, for example, the ON light amount is set to 1.0 μJ / cm ² , the grid voltage is gradually increased, and the surface potential of the photosensitive drum 1 is measured using a surface electrometer. As a result, V _H is 40 when the charging voltage V _S is 750V.
It is assumed that 0V and _VL are 60V. The optical attenuation curve C in FIG. 3 shows V _H and V _L when CR is 2.38, when the initial charging potential is 750 V and the ON light amount is set to 1.0 μJ / cm ² which is the maximum.
Indicates that they become 400V and 60V, respectively. This was based on V _H = 400V, the on light quantity set value corresponding to the other of the CR values which become V _L = 60V, obtains the V _S value. For example, when the light decay curve D in the figure of the liquid crystal shutter panel CR = 3.0, V _S set value
700V, ON light intensity setting value is 0.9μJ / cm ² .
Further, when the light attenuation curve E in the same figure of the liquid crystal shutter panel CR = 3.64, V _S set value 650V, the on light quantity set value 0.8MyuJ /
It shows that it is cm ² .

In this way, the photoconductor surface voltage V _H, V _L is constant V _H = 400V, V _L = ON light quantity set value to become 60V, obtained relation V _S set value for each head contrast CR The figure is FIG.

However, F shown in the same figure shows the light amount characteristic, and G shows the initial charging voltage characteristic. When the CR data is calculated in the data processing circuit 13, the light amount characteristic F as described above, the light amount as shown in the initial charging voltage characteristic G, or the data for setting the charging voltage is supplied to the light control circuit. 14 and to the grid voltage adjusting circuit 8.

Hereinafter, a specific light amount or initial charging voltage setting operation will be described.

First, by using the print head 3 having the liquid crystal shutter unit 3b having a certain CR value, the head drive circuit 11 is driven, the lamp 3a is turned on with an appropriate amount of light, and the micro shutter is driven to open. A voltage value corresponding to the detected light amount is supplied to the data processing circuit 13. Next, the micro shutter is driven to close while the lamp 3a is turned on, and the voltage value corresponding to the amount of light detected by the optical sensor 12 at this time is supplied to the data processing circuit 13. From the voltage value thus obtained, the CR of the print head 3 measured by the data processing circuit 13 is measured.
To measure.

The data processing circuit 13 stores the light amount data for CR and the initial charging voltage adjustment data shown in FIG. 4, which are obtained in advance as described above, and the light amount data is sent to the dimming circuit 14 according to the CR value. Then, the initial charging voltage adjustment data is output to the grid voltage adjusting circuit 8. For example, data processing circuit
When the CR calculated in 13 is 3.0, as shown in FIG. 4, the light amount data (voltage value) is adjusted so that the light amount of 450 μw / cm ² is applied to the light control circuit 14 to the photoconductor drum 1. Output to the optical circuit 14. The dimming circuit 14 outputs a light amount control signal according to the input light amount data to the ballast 15. This makes the lamp 3a
When the micro shutter is open, the light transmitted through the micro shutter can irradiate the photosensitive drum 1 with a light amount of 450 μw per 1 cm 2. This light intensity 450
Since μw / cm ² is 1 .mu.J / cm ² at the maximum value 500μw / cm ² of light quantity corresponds to 0.9μJ / cm ^2.

On the other hand, in the grid voltage adjusting circuit 8, a voltage corresponding to the grid 2c is applied according to the input initial charging voltage control data, and the high voltage supplied from the high voltage unit 7 supplies the voltage from the discharge wire 2a to the photosensitive drum 1. The discharge current is controlled so that the photosensitive drum 1 is charged to the initial charging voltage of 700V. Therefore, the light transmitted through the micro shutter in the open state has the photoreceptor surface potential V _{L set} to 60 V as shown by the curve D in FIG.

The above operation is performed by the liquid crystal shutter panel 3b (print head 3).
And the CR value calculated by the data processing circuit 13 is different from the above, the light amount data and charging voltage control data corresponding to the CR value are output to the dimming circuit 14 and the grid voltage adjusting circuit 8. And can be controlled in the same way.

In this way, the relationship between the CR and the initial charging voltage and the relationship between the CR and the exposure amount to the photosensitive drum 1 which are obtained in advance as shown in FIG. 4 are stored in the data processing circuit 13, and the lamp is based on this data. By setting the light amount of 3a and the initial charging voltage V _S , it is possible to always obtain the surface potentials (V _H , V _L ) of the photoconductor which are free from variations. Then, for example, if the above-mentioned adjustment is performed for each liquid crystal printer at the time of factory shipment, it will be different for each.
Appropriate initial charging potential V for print head 3 with CR
_It is possible to set _{S and} the amount of exposure to the photosensitive drum 1.

[Effect of device]

As described in detail above, according to the present invention, the light amount and the initial charging voltage can be adjusted based on the preset data corresponding to the different CR for each print head, and the light is formed by the light leakage from the print head. The photoconductor potential V _H and the photoconductor potential V _L formed by exposure can be set to be constant, and it is possible to always obtain a reproduced image of good quality in each liquid crystal printer.

[Brief description of drawings]

FIG. 1 is a block diagram of a process setting device of this embodiment, FIG. 2 is a schematic configuration diagram of a liquid crystal printer including the process setting device of this embodiment, and FIG. 3 is a quaternary chart of the process setting device of this embodiment. FIG. 4 is a characteristic diagram of light amount and initial charging voltage with respect to CR, and FIG. 5 is a partial diagram of a quaternary chart of a conventional process setting device. 1 ... Photosensitive drum, 2 ... Charger, 2a ... Discharge wire, 3 ... Print head, 3a ... Lamp, 3b ... Liquid crystal shutter panel, 8 ... Grid voltage adjustment circuit, 11 ... Head drive Circuit, 12 ... Optical sensor, 13 ... Data processing circuit,
14 …… dimming circuit, 15 …… ballast.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI G03G 15/043 (56) References JP-A-54-3546 (JP, A) JP-A-61-53670 (JP) , A) JP 56-156841 (JP, A) JP 60-22134 (JP, A) JP 60-260066 (JP, A) JP 54-21847 (JP, A) JP 60-119580 (JP, A) JP 53-93030 (JP, A) JP 60-22134 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A photoconductor, a charging means for charging the surface of the photoconductor, a light source for exposure, and an open or close drive according to a print signal to selectively transmit the light of the light source so that the light on the photoconductor is transmitted. A liquid crystal shutter for forming an electrostatic latent image on the surface, developing means for adhering toner to a low potential portion of the electrostatic latent image for reversal development, and transfer means for transferring the toner image formed by the developing means onto a sheet. In a process setting device of a liquid crystal printer comprising: a light amount measuring means for measuring the open transmitted light amount and the closed transmitted light amount by driving the light source to open and close the liquid crystal shutter, and an output of the light amount measuring means. Based on the calculation means for calculating the contrast between the light quantity at opening and the light quantity at closing, and the data of the storage means for storing the light quantity and the initial charging voltage corresponding to the contrast based on the calculation result of the calculating means. Setting means for setting the amount of light emitted from the light source and the charging ability of the charging means, and the surface potentials of the photoconductors when the liquid crystal shutter is opened and closed are constant regardless of the variation in the contrast of the liquid crystal shutter. A process setting device for a liquid crystal printer, characterized by: