JPH03250580A - Electroluminescent element and driving method for it - Google Patents

Abstract

PURPOSE:To reduce the electric field induced noise generated by the impression voltage to an EL element by impressing AC voltages in opposite phases on the EL element back-face electrodes arranged in two rows, and thereby driving the EL element. CONSTITUTION:Two band-shaped back face electrode 14, 15 are formed on a glass base board 13, and thereupon are placed No.1 insulation layer 16, light emitting layer 17, and No.2 insulation layer 18 in the sequence as named. Over it a transparent electrode 19 is provided to constitute an EL element 22, which are composed of elements 20, 21 arranged in two rows. The transparent electrode 19 is grounded, and AC voltages having equal value and opposite phases to each other are impressed on the back face electrodes 14, 15. Induction voltages are generated in the electrodes 14, 15 simultaneously, but they set off each other, as the impressed voltages has the opposite phases to each other, and thus generation of electric field noise is precluded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electroluminescent device and a method for driving the same, and in particular is used as a surface light source for a contact image sensor, and is designed to prevent electric field noise from being imparted to the light receiving element of the sensor. Electroluminescent device (
Hereinafter, it will be simply referred to as an EL element.

and its driving method.

[Conventional technology]

) When reading an image with a facsimile, for example, a document is irradiated with light and the reflected light is projected onto a CCD placed a certain distance away via a reduction lens, and the image is read. According to the above method, a certain distance is required between the document and the CCD, which increases the size of the apparatus. Therefore, in recent years, as shown in FIG.
An LED array (3) formed by linearly integrating the LEDs emits light onto the original (1) from the vicinity thereof, and the reflected light is projected onto the light-receiving section (2) to directly read the image. A contact type image sensor (4) is known. As described above, the contact image sensor (4) includes a light receiving section (2) and an LED array (3), and as shown in FIG. Except for (6), the common electrode (7), the amorphous Si layer (8), the transparent conductive film (9), and the metal film (10) are integrated and formed and integrated with the protective glass (11) through a small distance. It is incorporated into
Light is projected from the LED array (3) onto the light guide window (6). Then, the original (1) is placed in close contact with the lower surface of the protective glass (11), and while being sent in the direction of the arrow by the roller (12), light (L) is emitted from the light guide window (6).

The reflected light (L2) is received by the transparent conductive film (9) and converted into an electrical signal, and the image of the original (1) is divided into dots and read.

Here, in the contact image sensor (4), the LED array (3) that is the light source is a linear arrangement of a large number of LEDs, and each LED is a point light source. Therefore, it is necessary to make all LEDs have the same light intensity characteristics, which leads to an increase in manufacturing cost and is expensive. Therefore, a contact type image sensor (not shown) is also known in which a relatively inexpensive electroluminescent lamp is formed into a light emitting pattern and used as a surface light source instead of the LED array (3). At this time, since the electroluminescent lamp is a surface light source, L
Unlike the ED array (3), an electroluminescent lamp is placed below the document, and while maintaining its horizontality, light is irradiated onto the bottom surface of the document, and the light is received by a light receiving element such as a photodiode. The positions of the light source and the document shown in FIG. 6 may be reversed upside down.

[Problem to be solved by the invention]

By the way, as mentioned above, when an electroluminescent lamp is used as a light source of a contact type image sensor, for example, 100V
AC power is applied to cause the electroluminescent lamp to emit light. In this case, the light-receiving element that receives the reflected light from the original is located close to the electroluminescent lamp and handles weak signals, so voltage induction occurs due to the unbalance of stray capacitance between the electroluminescent lamp and the light-receiving element. There was a problem in that a voltage was generated in the light-receiving element as a result of the interference. Conventionally, a shield plate was disposed between the electroluminescent lamp and the light receiving element, but this required a transparent shield that allowed light to pass through, and because a conductive thin film was used, it was not possible to provide sufficient shielding.

[Means to solve the problem]

In the present invention, two electroluminescent elements are arranged in two rows, each of which is formed by laminating and forming a strip-shaped back electrode, a first insulating layer, a light-emitting layer, a second insulating layer, and a transparent electrode facing the back electrode on a substrate. Proximity/
It is characterized in that it is arranged to form one element, and its driving method is that it is driven by applying voltages equivalent to mutually opposite phases to the two rows of back electrodes.

[Effect]

According to the above technical means, alternating current voltages equivalent to mutually opposite phases are applied to the back electrodes of the EL elements arranged in two rows, and the transparent electrodes are grounded, and alternating current voltages equivalent to mutually opposite phases are applied to the respective rear electrodes. Then, the induced voltage is canceled out, and the electric field induced noise generated by the voltage applied to the EL element can be reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. 1 and 2 are partial cross-sectional perspective views showing one embodiment of the EL element according to the present invention and waveform diagrams of its driving voltage, and FIGS. 3 and 4 are close contact diagrams using the EL element according to the present invention. FIG. 2 is a partial side cross-sectional view and a partial plan view of a type image sensor. First, in Fig. 1, (13) is a glass substrate, (14)
(15) are arranged close to each other in two parallel rows on the glass substrate (13).
Two strip-shaped first and second back electrodes arranged (16)
(17) (18) (19) The first insulating layer, the light emitting layer, the second insulating layer and the transparent electrode are laminated and formed on the first and 29th surface electrodes (14) (15) on the glass substrate (13). in,
Two first and second EL elements (20) (21) are separated by two first and second back electrodes (14) (15).
) to form - EL elements (22).

The operation of the present invention will be explained below based on the above configuration. First, the transparent electrode (19) is grounded, and as shown in FIG. 2, alternating current voltages (Vt) (vz) which are equivalent to opposite phases are applied to the first and second back electrodes (14) and (15). Then, the induced voltage will increase to each back electrode (14) (
15), but since the applied voltages are in opposite phases, they cancel each other out. Therefore, no voltage is induced in the outer periphery, and no electric field noise is generated.

Next, an example of an integrated device using the EL element (22) as a surface light source of a contact type image sensor will be shown with reference to FIGS. 3 and 4. In the figure, (13) is a glass substrate, (20
) (21) are the first and second EL elements, (23) is the light guide layer glass substrate, (24) is the light receiving element, (25) is the transparent film, (26) is the inert gas, and (27) is the original. It is. The first and second EL elements (20) (21) are mounted on a glass substrate (13) as one EL element (22) according to the present invention.
), the first EL element (20) is used for light emission, and the second EL element (20) is used for light emission.
Elements (21) are used for electric field cancellation.

A large number of light receiving elements (
24) are arranged facing the first EL element (20) at a constant pitch, and are protected with a transparent film (25),
It is integrally combined with the EL element (22) via an inert gas (26), and a light guide window (2) is provided in the center of each light receiving element (24).
day).

The operation will be explained below based on the above configuration. First, the manuscript (
27) in substantially close contact above the glass substrate (23).
, the second EL elements (20) (21) are fed substantially perpendicularly to the longitudinal direction, and the first and second EL elements (20) (2
1) Apply voltages with opposite phases to each other.

Then, from the first BL element (20) to the light guide window (28)
At the same time, the reflected light is sent to the light receiving element (
24) and reads the image of the document (27) by dividing it into dots. At this time, the electric field induced noise generated by the first EL element (20) is canceled by the opposite phase equivalent voltage applied to the second EL element (21), and the light receiving element (20)
4) Preventing electric field induced noise. In the above embodiment, the first and second EL elements (20) and (21) were formed on the same substrate, but they may be formed separately on two different substrates and disposed close to each other. , and only an electrode is provided instead of the second EL element (21) for noise cancellation,
A phase-adjusted voltage may be applied, or the first and second EL
The voltages applied to the elements (20) and (21) do not necessarily have to be the same.

〔Effect of the invention〕

According to the present invention, when an EL element is used as a light source of a contact type image sensor, electric field R11A noise applied to a light receiving element can be prevented.

[Brief explanation of drawings]

1 and 2 are partial cross-sectional views showing one embodiment of the EL element according to the present invention and waveform diagrams of its driving voltage, and Figures 3 and 4 are close-contact type using the EL element according to the present invention. 5, 6, and 7 are a perspective view, a side sectional view, and a plan view of the main parts of a conventional contact type image sensor. be. (13) --- One board, (14) (15)
- Back electrode, (16)--111 first insulating layer, (17)
-Light emitting layer, (18)--Second insulating layer, (19)--Transparent electrode, (20) (21)--Electroluminescent element.

Claims (2)

[Claims] (1) A strip-shaped back electrode, a first insulating layer, a light emitting layer, a second insulating layer, and a transparent electrode facing the back electrode are laminated on a substrate.
An electroluminescent device characterized in that one device is formed by arranging two formed electroluminescent devices close to each other in two rows. (2) The method for driving an electroluminescent device according to claim (1), characterized in that the two rows of back electrodes are driven by applying voltages equivalent to mutually opposite phases.