JPH03165171A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To attain a close contact image sensor with small size, light weight and low power consumption and a close contact type color image sensor with high resolution, small size and light weight by forming a thin film EL element to a base end face at an angle so that its radiating light reflected once is made incident in a photodetection face of a photodetector. CONSTITUTION:A thin film EL element 5 of end face lighting type is formed to a tilted end face of a base 1. The light radiating from the end face is made incident in an original 7 via a cover glass 6. Since the directivity of the light by the end face radiation is much strong, the function is attained sufficiently by designing the tilt angle of the base end face properly, and in order to improve the resolution and the lighting efficiency furthermore, a light shield layer 8 having a light intake window 9 or 10 relating to a reflected light is formed to the cover glass 6. Thus, a small sized light weight close contact image sensor with small power consumption and a color image sensor with excellent resolution and fast operation are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a contact type image sensor using a thin film EL element as a light source, which can be used as an image input device for facsimiles, digital copies, etc.

[Prior Art] As OA terminals become more compact, even image scanners used for reading documents such as facsimiles are becoming smaller than several LOc! In place of the optical reduction type image sensor which requires an optical path length of 1, there is an increasing demand for a contact type image sensor.

A contact image sensor is characterized by being extremely compact because the sensor unit, which is approximately 1 cm thick, is pressed against the surface of the document for reading.

In order to make even more use of this feature, a so-called complete contact type has been devised by removing the lens array and phi-no-kuichi array that were conventionally placed in front of the light-receiving section. However, in both cases, the illumination light source, such as a xenon lamp, halogen lamp, or LED1 phosphor, is attached externally to the sensor body, which is a major obstacle to compact design. In addition, these light sources are installed at a distance from the document surface, and only a small portion of the light beams extracted from the lighting window, which has an area comparable to the light-receiving surface, is used. Therefore, an extremely large light source is required, which not only becomes an obstacle to miniaturization, but also causes problems of power consumption and heat generation depending on the type of light source. In order to improve this drawback, it is known that a method using a thin film EL element as a light source and providing it very close to a light receiving element is promising. However, the light emitted by the thin-film EL element is of a surface-emitting type with extremely strong diffusivity, and blurring occurs unless the light-emitting surface is brought close to the document surface or a lens array is attached in front to focus the light. As described in JP-A-59-210664, a method was also proposed in which a thin film EL element was laminated on a light receiving element, but according to this method, the uppermost surface of the light emitting surface was a transparent conductive film, and the damage to it was extremely severe. In addition, a new drawback arises in that the element isolation between the light emitting part and the light receiving part is incomplete and the SN is also deteriorated.

On the other hand, scanners have been realized in which a color original reading function is added to these contact-type image sensors. In general, the following three types of methods have been proposed for reading color originals.

(1) Parallel color separation by directly attaching color separation filters to each pixel (2) Serial color separation of illumination light by sequentially switching color separation filters (3) Serial color separation of one illumination light by sequentially switching multiple light sources Generally speaking, in these color separation methods, (1) is a reduction in resolution and the number of driving elements is increased by an integer, (2) is the response speed and reliability of the filter switching mechanism, and (3) is a shift in the optical path. Problems such as the response speed of light emission have been pointed out. but,
At least for contact type image sensors, multiple light sources are used (
The adaptability of the method 3) is extremely low, and this is a major constraint in expanding the diversification of color image sensors.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the conventional technology and provides a compact, lightweight, low power consumption contact type image sensor-1. The aim is to provide a sensor.

[Means for Solving the Problems] The structure of the present invention for solving the above problems is (1) having a light receiving element on the surface or inner surface of the substrate and a thin film EL element on the end surface, and this thin film EL element Light is emitted from the end face of a thin film EL layer sandwiched between reflective electrode layers, and a close contact formed on the end face of the substrate at an angle such that the emitted light enters the light receiving surface of the light receiving element after being reflected. It is a type image sensor.

(2) The contact type image sensor according to item (1) above, wherein the thin film EL element is a multicolor thin film EL element having a plurality of thin film EL layers each sandwiched between light reflective electrodes and emitting light of different colors. .

One aspect of the present invention is a contact type image sensor that uses a thin film EL element as a light source, which is formed on the end face of a substrate on which a light receiving element is formed, and emits light from the end face of a thin film EL layer sandwiched between light reflective electrode layers. Ru.

Also, in the above-mentioned contact type image sensor,
It is constructed by making the end face of the substrate on which the thin film EL element is formed tilt with respect to the substrate surface so that it is at least less than 90''.

FIG. 1 is a sectional view of an array for explaining an example of a contact type image sensor according to the present invention. In the figure, 1 is a substrate, 2 is a thin film light receiving element, 3 is its lower electrode, and 4
is its upper electrode. An edge-emitting thin film EL element 5 is formed on one inclined end surface of the substrate l. The light emitted from the end surface enters the document 7 via the cover glass 6. The arrows roughly indicate the incidence of light on the document surface and its reflection. The light emitted from the edge is extremely directional, so the function can be achieved by appropriately designing the angle of inclination of the edge of the substrate, but in order to further improve the resolution and lighting efficiency, it is necessary to A light shielding layer 8 having a daylight window 9 or a daylight window 1O corresponding to the above is formed on the cover glass 6.

The present invention relates to a thin film EL element used as a light source, and does not specify the structure or material of the light receiving element. Thin film photodetector 2
The photoelectric conversion material is amorphous 5iSCdSSC.
dSe, Cd5-CdSe solid solution, chalcogen mixture, etc. can be used, and both sandwich type and Brehner type electrode structures can be used.

Further, although a thin film light receiving element is used in FIG. 1, a close contact type using a CCD chip can also be applied.

The light receiving element can be provided not only on the top surface of the substrate but also inside the substrate if the substrate is transparent. This allows for a thinner contact image sensor.

FIG. 2 is a diagram showing the structure of the thin film EL element 5. As shown in FIG. Glass, ceramics, etc. can be used for the substrate l. A light reflective electrode layer 11. Thin film E
The L layer 12 and the light reflective electrode layer 13 are formed in this order. A commonly known metal electrode such as AlSCrSAg can be used for the light reflective electrode layer 11.13. The light emitting layer of the thin film EL layer 12 is made of ZnS, which is generally well known.
:Mn (orange), ZnS:Tb (green), etc. can be used, but in terms of panchromatic, ZnS:Pr single layer, SrS:Pr single layer, SrS:Ce
, Eu single layer, S rS : Ce and S rS : Eu
Lamination of SrS:Ce and CaS:Eu, SrS
rs: Ce and Zn S: Mn stack, etc.
It is better if the luminescent color is white. The reliability of the device is improved by providing an insulating layer on both sides or one side of these light emitting layers. The material for the insulating layer is
Nitride such as Si 3N4, AIN, BN, Ta205
, Al2O3, Y2O3, 5i02, or a ferroelectric material having a tungsten bronze structure or a perovskite structure. Further, these materials may be mixed and used, or different types of thin films may be laminated.

Due to this configuration, the thin film EL layer 12 has a kind of waveguide effect, and the light generated inside is guided to the end face, and light that is parallel to the end face of the substrate and has extremely strong directionality is emitted from the end face. By adjusting the thickness and width of the thin film EL layer 12, this type of light emission can be made 1 to 2 times larger than that of normal surface light emission.
An orderly high illumination intensity can be obtained, and line emission corresponding to the thickness of the thin film EL layer 12 (approximately 1 μm layer) can be obtained. In order to further increase the illuminance and reduce flare light, a light reflecting layer may be provided on the other end surface of the thin film EL layer 12.

A well-known blackened film or the like can be used as the light shielding film 8.

The substrate 1 and the cover glass 6 are pasted together with a predetermined gap therebetween. In order not to reduce the resolution, the thickness of the cover glass 6 should be as thin as possible, and the gap space should be narrow.

In general, thin-film EL elements emit light stably when driven by alternating current, but the time for one light emission is approximately several tens of microseconds for a short device such as S rS:Ce, and several hundred microseconds for a long device such as S:Mn. . Therefore, if the sensor array uses an accumulation-type reading method, even if the sensor array has a short emission time, the light emission waveform will be a burst wave with no problem due to the light emission by AC drive of about several kHz, but in the case of a real-time photoconductive reading method, It is necessary to improve the temporal uniformity of light emission by increasing the frequency even further.

Another example of the present invention is formed on the end face of a substrate on which a light receiving element is formed, and in which light reflective electrode layers and thin film EL layers of at least 2FIi type or higher and different emission colors are laminated alternately. A contact type color image sensor whose light source is a multicolor thin film EL element that emits light from the edge of a thin film EL layer.
It is composed of multiple EL layers that emit light of different colors, and emit light in sequence at a certain period, and in synchronization with this, a single light-receiving element performs a time-division light-receiving operation, thereby producing serially color-separated image information. It is for reading.

Another reason is that in the above-mentioned contact type color image sensor, the edge surface of the substrate on which the edge-emitting multicolor thin film EL element is formed is inclined at least 90'' with respect to the substrate surface. configured.

Another aspect is that the multi-color thin film EL element is constructed by laminating three thin film EL layers, each of which emits light in the three primary colors of RGB.

FIG. 3 is a sectional view of an array for explaining the contact type color image sensor according to the present invention. In the figure, 14 is a substrate, 15 is a thin film light receiving element, 1B is its lower electrode, and 17 is its upper electrode. 18A, 18B,
18C are multi-color thin film EL elements each emitting light of a different color from each other and emitting light from the edge thereof, and are formed on one inclined end surface of the substrate 14. The light emitted from the end surface enters the document 20 via the cover glass 19. The arrows roughly indicate the incidence of light on the document surface and its reflection. The light emitted from the edge is extremely directional, so the function can be achieved by appropriately designing the angle of inclination of the edge of the substrate, but in order to further improve the resolution and lighting efficiency, it is necessary to The cover glass 19 covers the light shielding layer 21 having the lighting window 22 or the lighting window 23 corresponding to the
1; Form.

The substrate 14 can be made of glass, ceramics, etc., and the photoelectric conversion material of the thin film light receiving element 15 can be amorphous S t -, CdS 5CdSe, Cd5
A -CdSe solid solution, a chalcogen mixture, etc. can be used, and both a sandwich type and a Brenna type can be used as the electrode structure. Further, although a thin film light receiving element is shown in FIG. 3, a close contact type using a CCD chip can also be applied. However, compared to the emitted light color of a multicolor thin film EL element,
It must have a corresponding spectral sensitivity.

FIG. 4 shows the detailed structure of the multicolor thin film EL device. On the substrate 14, a light reflective electrode layer 24A1 thin film EL layer 25A1 light reflective electrode layer 24B1 thin II! EL layer 25B1 light reflective electrode layer 24C1 thin film EL layer 25C1 light reflective electrode layer 24D are formed in this order.

A switching element is connected to each electrode layer, and each thin film EL element sequentially emits light by operating the switching element. light reflective electrode layers 24A, 24B,
Al5Cr for 24C and 24D.

A commonly known metal electrode such as Ag can be used.

The effects of the present invention can be achieved if the light-emitting layers of the thin film EL layers 25A, 25B, and 25C are a plurality of layers that emit light of different colors, but in order to accurately reproduce color images, RG
There must be three types that emit the three primary colors of B. Generally well-known red materials include ZnS: Sm, C
aS: ZnS:Tm5Sr for blue materials such as Eu
Se:Ce5SrS:Ce, etc., and ZnS for green materials
:Tb, CaS:Ce, etc.

The order of stacking is not particularly limited. The reliability of the device is improved by providing an insulating layer on both sides or one side of the light emitting layer. Materials for the insulating layer include Si3N4, nitrides such as AlN5BN, Ta2es,
Oxides such as Al2O3, Y2O3, 5i02, or ferroelectric materials having a tungsten bronze structure or perovskite structure can be used. Furthermore, these materials may be mixed and used, or different types of thin films may be laminated.

With such a configuration, each thin film EL layer has a kind of waveguide effect, and the light emitted inside is guided to the end face, and light that is parallel to the end face of the substrate and has extremely strong directionality is emitted from the end face.

In this type of light emission, by adjusting the thickness and width of each thin film EL layer, an illumination intensity that is 1 to 2 orders of magnitude higher than that of normal surface light emission can be obtained. Line light emission can be obtained according to the In order to further increase the illuminance and reduce flare light, a light reflecting layer may be provided on the other end surface of the thin film EL layer.

A well-known blackened film or the like can be used as the light shielding film 21.

The substrate 14 and the cover glass 19 are pasted together with a predetermined gap therebetween. In order to avoid deteriorating the resolution, it is better that the thickness of the cover glass 6 is as thin as possible and that the gap space is narrow.

The EL light emission becomes continuous line light emission parallel to the sensor array. In the case of this multicolor thin film EL element, the optical axes from the end faces of the respective thin film EL layers almost coincide with each other. This is an important feature for the present invention.

FIG. 5 is a schematic diagram of a timing chart of operations in one particular pixel, and the reading method is an accumulation method.

In general, thin-film EL elements emit light stably when driven by alternating current, but the time for one light emission is several tens of microseconds for a short device such as S rS ;Ce, and several hundred microseconds for a long device such as ZnS:Mn. be. Therefore, if the sensor array uses a cumulative reading method,
Even if the light emission time is short, the light emission waveform will be a burst wave with no problem when the light is emitted by AC drive of about several kHz, but
In the case of a real-time photoconductive method, it is necessary to achieve temporal uniformity of light emission by increasing the frequency even higher.

With the contact type color image sensor according to the present invention,
High resolution, high speed, small size, and light weight can be achieved.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 In this example, the element configuration shown in FIG. 1 is used.

A quartz substrate with a thickness of 1.21 mm was used as the substrate 1, and the end face on which the thin film EL element was to be formed was polished in advance so as to have a predetermined inclination angle. The light receiving element 2 had a one-side insulating element structure using amorphous Si2H as a photoelectric conversion material. Lower electrode 3
For the upper electrode 4, Cr was used, and for the upper electrode 4, AI was used. The light receiving width was set to 70μ. For the reasons mentioned above, the driving method was an accumulation/reading type, and polySL type TFTs formed on the same substrate were used as driving switching elements.

On the end face of the quartz substrate 1, Cr is coated as a light reflective electrode layer 11.
, ZnS:Mn with a thickness of 0.8 μl sandwiched on both sides by Y2O:l insulating layers as the thin film EL layer 12.

AI was sequentially formed as the light reflective electrode layer 13.

The thickness of the cover glass 6 is 50t1m, a blackened film 8 is formed on the inside of the cover glass 6, and a lighting window 9 is formed roughly along the arrow in the figure.
．． 10 were provided for each. This effect greatly improved resolution. The gap between the quartz substrate 1 and the cover glass 6 was sealed and fixed with polyimide, and they were bonded together with an epoxy-based transparent adhesive. The gap space was 30 μl.

Example 2 In this example, the substrate 14 was a quartz substrate with a thickness of 1.21 mm, and the end face on which the thin film EL element was to be formed was polished in advance to a predetermined inclination angle. Thin film photodetector 1
No. 5 had a one-sided insulating element structure using amorphous St 2 :H as a photoelectric conversion material.

This photodetector showed highly panchromatic spectral sensitivity to visible light. Cr was used for the lower electrode 16, and AI was used for the upper electrode 17. The light receiving width was 70 μm.

For the reasons mentioned above, the driving method was an accumulation/reading type, and a polySt-based TPT formed on the same substrate was used as a driving switching element.

On the other hand, the light reflective electrode layers 24A, 24B, 24C, 2
A Cr metal electrode is used as the 4D, and a thin film EL layer 25A,
5rSe:Ce (blue), CaS:Eu (red) with a thickness of around 1.2μ with AIN insulating layers sandwiched on both sides as 25B and 25C, respectively s Z n S :T
b (green) was used.

The thickness of the cover glass 19 was 50 μm, a blackening film 21 was formed on the inside thereof, and lighting windows 22 and 23 were provided roughly along the arrows in the figure. The gap between the quartz substrate 14 and the cover glass 19 is sealed and fixed with polyimide,
It was attached using a transparent epoxy adhesive. The gap space was 30 μm.

[Effects of the Invention] As explained above, the fixed image sensor of the present invention
It is small, lightweight, and consumes little power.Furthermore, the color image sensor has a high resolution and can work at high speed.

[Brief explanation of the drawing]

FIG. 1 and FIG. 3 show an image sensor according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional diagram illustrating the operation. 2 and 4 are partially enlarged sectional views of the above embodiment, and FIG. 5 is a graph explaining the operation of the multi-color image sensor of the present invention. 1 and 14...substrate, 2 and 15...thin film light receiving element, 3 and 1B...lower electrode, 4 and 17...upper electrode, 5 and 11-C...thin film EL element, B and 19...-cover glass, 7 and 20... original, 8 and 2I... light shielding layer, 9.10.22.23...
- Lighting window, 11.13 and 24A-D...Light reflective electrode, 12 and 25A-C...Thin film EL layer. Figure Figure

Claims (2)

[Claims] (1) Light-receiving element on the surface or inner surface of the substrate, thin film E on the end surface
This thin-film EL element has an L element, and this thin-film EL element emits light from the end face of a thin-film EL layer sandwiched between light-reflecting electrode layers. After the emitted light is reflected, it enters the light-receiving surface of the light-receiving element. A contact image sensor is characterized by being formed on the edge of a substrate at an angle that (2) The close-contact type according to claim (1), wherein the thin film EL device is a multicolor thin film EL device having a plurality of thin film EL layers each sandwiched between light reflective electrodes and emitting light of different colors. image sensor.