JPH03216357A - Edge-emitting EL printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic edge-emitting EL printer equipped with a line head in which edge-emitting EL elements are arranged in series.

2. Description of the Related Art Line printers are one type of printers that have been developed using electrophotography in recent years. This line printer consists of a charger, a line head,
A system in which devices such as a developing device and a transfer device are arranged facing each other, and the peripheral surface of a latent image carrier charged by a voltage applied by a charger is exposed to light by selective light emission from a light emitting element connected to a line head. This latent image is developed with toner, which is a developer supplied from a developing device, and then transferred onto printing paper by a transfer device.

The light emitting element of the above-mentioned line head is generally an LED (Light Emitting Diode).
However, this has problems such as the difficulty of correcting the difference in light emission intensity between each element, so currently edge-emitting type E
L (Electro Luminescence)
It is considered to use elements. Therefore, a line head using this edge-emitting type EL element will be explained based on FIGS. 2 and 3. As illustrated in FIG. 3, the edge-emitting EL element 2 of this line head 1 has a thin active layer 3 made of zinc sulfide or the like containing an active element surrounded by dielectric layers 4 and 5 from above and below. Flat plate electrodes 6 and 7 are formed on the upper and lower surfaces of the dielectric layers 4 and 5, and extremely flat light is emitted from the end surface of the active layer 3, unlike the conventional E in which the upper surface emits light.
It is possible to obtain a luminescence intensity about 100 times that of L. Then, as illustrated in FIG. 2, the edge-emitting EL elements 2 having the above-mentioned structure are successively arranged on a substrate 8 using thin film technology, etc., and a rod lens array (not shown) or the like is attached to the line head. 1 is formed.

Therefore, for example, a line head 1, in which an AC power source 9 is connected to each edge-emitting EL element 2 via a switching element, is connected to the scanned surface of the latent image carrier together with a charger, a developer, a transfer device, etc. By arranging them facing each other, an edge-emitting EL printer (not shown), which is one type of line printer, can be manufactured. However, such edge-emitting EL
When used as a printer, the edge-emitting type EL element 2 has an extremely large aspect ratio of the beam shape of the emitted light and is flat, so a means for correcting this is required.

Accordingly, as a device that solves the above-mentioned problems, there is a device proposed by the present applicant in Japanese Patent Application No. 1-97081. Therefore, this device will be explained as a prior art of an edge-emitting type EL printer with reference to FIGS. 4 to 6.

In the illustrated edge-emitting EL printer 1o, a timing controller is connected to an interface 12 to which a printer controller 11 such as another device is connected, through a control circuit 16 to which two address counters 13, 14 and a reference clock 15 are connected. 17 are connected. Further, each of the interfaces 12 is a three-state 1
8 to 2l are connected via a first data processing circuit 24 to two RAMs 22.23 which are line memories connected to the input/output section, and the RAM 22.23 is connected to the control circuit 16 and the address counter. 13 and 14 are connected via the selector 25. Furthermore, the R
AM22, 23 is connected via the three states 20, 2l to the second data processing circuit 26 to which the timing controller l7 is connected. The data processing circuit 26 also includes latches 27, -27q and drivers 28. -28q are connected in parallel to shift registers 31, -31q connected to block electrodes 30, -30n of line head 29. moreover,
The timing controller 17 has a common electrode 32 . of the line head 29 . .about.32m, and the latches 27, .about.27q and shift registers 31, .about.31q.

Note that mXn edge-emitting type EL elements 2 are arranged in series in the line head 29.

In this configuration, in this edge-emitting EL printer 10, print data including a Glock signal inputted from the printer controller 11 via the interface l2 is sent to the first data processing circuit 24 for each main scanning line.
It is compressed by processing such as sorting.

Therefore, this compressed print data is stored in RAM22.2.
The print data is temporarily stored in one of the RAMs 23 and 3 during the printing time of one main scanning line, and at the same time, the print data temporarily stored in advance is outputted from the other RAM 23 and 22 at high speed.

Here, the selection of the RAMs 22 and 23 for temporarily storing print data is performed by the selector 25, which operates according to the timing input from the printer controller 11 to the address counter 13. Further, the output of print data from the RAMs 23 and 22 is performed according to the control circuit 16 and address counter 14, which operate in synchronization with a reference clock signal for high-speed output generated from the reference clock 15.

Therefore, this output print data is reprocessed by the second data processing circuit 26 into a format suitable for printing, and is sequentially output to the shift registers 31, 31q, and latches 27, 2
Retained by 7q. And these members 31.27
and the common driver 33 are the timing controller 17
The block electrode 30. ~30n and common electrode 32. .about.32m, low voltage and high voltage drive pulses are repeatedly applied to the line head 29 a predetermined number of times.

Therefore, in this edge-emitting type EL printer 10, as shown in the time chart shown in FIG. 5, the time T. During this period, multiple driving pulses are applied to the line head 29, and the above-described operation continues for a time T. The line light emission from the line head 29 is repeated four times in the width of the scanning line.

By doing this, the flat pixel components formed by one device light emission of the edge-emitting type EL element 2 are arranged consecutively in the sub-scanning direction. Even if the beam shape of the EL element 2 is flat, substantially square pixels are obtained, jagged deviations at the edges of the main scanning line are minimized, white spots are prevented from occurring in the pixels, and printing quality is high.

In other words, the above-mentioned edge-emitting type EL printer [O] can form substantially square pixels even if the beam shape is flat by repeating the device light emission of the edge-emitting type EL element 2. Therefore,
The present applicant has proposed an edge-emitting EL printer (not shown) capable of expressing halftones by applying the above operation in patent application No. 1-9.
I proposed No. 7085.

The structure of this device is almost the same as the edge-emitting type EL printer 1o illustrated in FIG. Halftones are expressed by arbitrarily reducing the number of elements. In other words, for example, if one pixel is formed by four times of device light emission of the edge-emitting type EL element 2, the number of times of operation of this edge-emitting type ET-element 2 is controlled to control the number of times of device light emission in one pixel area. 4 times or less to reduce the amount of toner adhering to one pixel area of the latent image carrier to form a pixel with an intermediate density.

Problems to be Solved by the Invention The above-mentioned edge-emitting EL printer is capable of expressing gradation on a pixel-by-pixel basis by varying the number of times the element emits light, so it is different from general electrophotography, which expresses halftones based on pixel density, etc. It is possible to express halftones at a higher resolution than other printers.

Here, in current printers, the resolution K is K =
A performance of about 25 (dots/mm) is required. In this case, the area of one pixel is 1/K = 4. O
X IQ-" (mm), and the average particle size D = 2.2 X 10-' for currently used toners.
(mm).

However, since the aforementioned edge-emitting EL printer expresses halftones by adjusting the amount of toner in each pixel, it is not possible to achieve both resolution and intermediate density reproducibility using toner with the above-mentioned average particle size. Have difficulty.

In other words, as illustrated in FIG. 7, if the number of operations S of the edge-emitting type EL element 2 for one pixel is four, the width in the sub-scanning direction of the pixel component formed by one element light emission is Become. Therefore, the average particle size is D = 2.2X 10-"
(mm) of toner, the development area is too large compared to the width of the pixel component in the sub-scanning direction. However, the printing is equivalent to that of a fully emitting pixel, and the reproducibility of halftones is inhibited.

Therefore, in order to achieve high-quality gradation printing with an edge-emitting EL printer that expresses gradation in units of one pixel by varying the number of times the edge-emitting EL element 2 emits light as described above, it is necessary to It is necessary to define certain conditions between the number of repetitions S of the operation, the resolution K, and the average particle diameter D of the toner.

Means for Solving the Problem A line head in which edge-emitting EL elements are arranged in a longitudinal direction on a light-emitting end face is provided, and this line head is moved along with a charger and a developer at least on a surface to be scanned in a sub-scanning direction on a latent image carrier. Pixels are formed by arranging flat pixel components in the sub-scanning direction, which are formed by one light emission of each edge-emitting EL element of the line head, on the scanned surface of the latent image carrier. A pixel forming means is provided to form pixels, and the resolution of image printing is K,
When the number of repetitions of the light emitting operation of the edge-emitting EL element for forming one pixel is S times, and the average particle size of the developer supplied from the developing device to the scanned surface of the latent image carrier is D, then l1 D< Make sure that the relationship xx2 KS is satisfied.

The resolution of the working image printing is K, the number of repetitions of the light emitting operation of the edge-emitting EL element for forming one pixel is S times, and the average particle size of the developer supplied from the developing device to the scanned surface of the latent image carrier is By satisfying the relationship D (X - It is possible to develop only parts of the pixel components in the area.

Example An embodiment of the present invention will be described based on FIG.

First, the edge-emitting EL printer of this example (not shown)
has approximately the same structure as the edge-emitting type EL printer 10 illustrated in FIG.
(dots/mm) and toner average particle diameter D (mm)
is designed to satisfy the relationship 11 D<-XX2 KS.

In this configuration, in the edge-emitting type EL printer of this embodiment, the number of times of element light emission of each edge-emitting type EL element 2 for one pixel is varied, similar to the edge-emitting type El-Plink described above. Performs gradation expression in pixel units. At this time, in the edge-emitting type EL printer of this embodiment, the number of repetitions of the light emitting operation of the edge-emitting type EL element 2 for forming one pixel is S=4, and the resolution K=25 (dots
/ mm), then based on the above conditions, the toner has an average particle size D = 1.2 x 10-
' (nun) is used. Here, as mentioned above, the width in the sub-scanning direction of the pixel component formed by one device emission of the edge-emitting type EL element 2 is as follows. Therefore, this is the average particle diameter of the toner D=], 2XI0(m
m) is approximately equivalent.

Therefore, under the above-mentioned conditions, for example, if you print a pixel with an intermediate density in which the device emits light twice and then does not emit light twice, as shown in the figure, only the light-receiving area in one pixel area will be developed and the intermediate density will be printed. Tonal expression can be realized with good reproducibility.

In this embodiment, an edge-emitting EL printer is illustrated which is provided with a halftone expression means that reduces the number of pixel constituent elements of one pixel area value to form a pixel with an intermediate density. For example, the present invention is not limited to, and can also be applied to, for example, an edge-emitting EL printer (not shown) that forms an image using black and white binary pixels. Even in this case, an edge-emitting EL printer that satisfies the above conditions has an average particle size of toner that is smaller than the pixel area, so the shape of each pixel is clearly formed, the resolution is extremely high, and it is easy to develop. Even the black spots that tend to occur on the white portion of paper due to defects are small enough to be difficult to see, resulting in beautiful images.

Effects of the Invention As described above, the present invention provides a line head in which edge-emitting EL elements are successively arranged in the longitudinal direction of the light-emitting end surface, and at least the surface to be scanned moves in the sub-scanning direction along with the charger and the developer. Flat pixel components are arranged facing the latent image carrier and formed by one device light emission of each edge-emitting type EL element of the line head on the scanned surface of the latent image carrier, and are arranged in the sub-scanning direction. a pixel forming means for forming a pixel;
The resolution of image printing is K, the number of repetitions of the light emitting operation of the edge-emitting EL element for forming one pixel is S, and the average particle size of the developer supplied from the developing device to the scanned surface of the latent image carrier is D. By satisfying the relationship 11 D (-X - X 2 KS when It is possible to develop only the pixel constituent parts in the area, and it has effects such as being able to realize high-quality black-and-white printing and halftone printing with good reproducibility at high resolution.

[Brief explanation of drawings]

Figure 1 is a front view of a printed image showing an embodiment of the present invention, Figure 2 is a front view of a printed image showing an embodiment of the invention;
The figure is a perspective view of an edge-emitting type EL element array, Figure 3 is a perspective view of an edge-emitting type EL element, and Figure 4 is an edge-emitting type EL element filed by the present applicant as [Patent Application No. 1-97081]. FIG. 5 is a block diagram showing the circuit structure of the printer, FIG. 5 is a time chart, FIG. 6 is a front view of a printed image, and FIG. 7 is an enlarged front view of main parts. 1... Line head, 2... Edge emitting type EL element =
IY-1ymon E-11

Claims (1)

[Scope of Claims] A line head in which edge-emitting EL elements are arranged in a longitudinal direction on a light-emitting end surface is provided, and this line head, together with a charger and a developer, is attached to a latent image carrier whose scanned surface at least moves in a sub-scanning direction. Pixels are formed by arranging flat pixel components in the sub-scanning direction on the scanned surface of the latent image carrier, which are formed by one light emission of each edge-emitting type EL element of the line head. A pixel forming means is provided to form a pixel, the resolution of image printing is K, the number of repetitions of the light emitting operation of the edge-emitting EL element for forming one pixel is S times, and the pixel is supplied from a developing device to the scanned surface of the latent image carrier. When the average particle size of the developer is D, D<(1/K)×(1/S)×2