JP2566576B2 - Organic long thin film color reading device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reading element, and more particularly to a novel RGB color reading element for an image in an apparatus that reads an image and processes information, such as a facsimile or a printer. Is.

[Conventional technology]

Conventionally, semiconductor image sensors such as CCDs and photodiode arrays such as MOS photodiode arrays have been widely used as reading devices used in facsimiles, printers and the like. Since it is customary to use a reduction optical system for these image sensors, a lens or the like is required, and the optical path length becomes long, resulting in a serious problem in downsizing the apparatus.

On the other hand, recently, a contact type thin film reader having the same size as the document width has been proposed (Mamoru Mizuguchi; Journal of Image Electronics Engineers of Japan,
Vol. 15, No. 1, pp. 17-26, Yoshio Tate; Journal of the Television Society, Vol. 38, No. 6, pp. 512-519). This device is called a planar type, and a device in which a photoconductive layer is provided on a substrate and an electrode pair is further provided thereon is an element corresponding to one pit. The above-mentioned reading device forms a plurality of these elements in a line and sequentially measures the photocurrent corresponding to the light irradiation of these element portions to perform reading.

Also, as an application from a solar cell, many of a sandwich type structure in which amorphous silicon is used for a photoelectric conversion layer and electrodes are provided above and below have been proposed. In the case where the amorphous silicon is of the pin type, the specific resistance of the n-type amorphous silicon layer is as low as 10 ⁴ to 10 ⁶ Ω · cm.
If the divided pits are not completely separated using a lithography technique such as photoresist coating and etching, a current will flow between the pits, making it difficult to read an image. This situation is the same in the above-mentioned planar type structure, and the separation between pits becomes a big problem.

Recently, many structures using a high resistance amorphous silicon layer have been proposed and structured, but leakage of current between adjacent pits has not been solved.

On the other hand, as a color sensor for reading colors, RGB that combines color filters of three colors of red (R) green (G) blue (B)
System color sensor has been put to practical use (Kunano Kuwano; Electronics, September 1982 issue, pp.53-56), and a color image reading element combined with the above reading element has been proposed. Three independent photoelectric conversion elements corresponding to three color filters are required, and the pixel density is reduced to 1/3 in the conventional integration degree. In addition, a color filter must be separately created and combined, which complicates the manufacturing process and increases the cost.

[Problems to be solved by the invention]

As described above, the leakage of the signal between the pits which are the respective image elements is a problem that must be eliminated in order to reproduce a sharp image. Complete separation of pits by the lithographic technique complicates the process, increases variability among pits, and even when high-resistance amorphous silicon is used, the leak is still eliminated.

In addition, in a device that combines RGB color filters to achieve colorization, it is necessary to triple the degree of integration to maintain the conventional pixel density, and signal leakage between pits becomes an even greater problem. In addition, a complicated and highly miniaturized manufacturing process is required, resulting in high cost.

The present invention has been made in order to solve the above-mentioned problems, and there is no leak between pits, a color filter and three independent photoelectric conversion elements are not required, and an effective 1
It is an object of the present invention to provide an RGB long organic thin film color reading element that can extract RGB three color components in the area of an element and is advantageous even in miniaturization.

[Means for solving problems]

In the organic long thin film color reading device according to the present invention, first to fourth electrodes are sequentially arranged, and a photoelectric conversion capability is provided between the respective electrodes, and p-type, n-type, and p-type or n-type is provided. Vintage p
Type and n-type, the first, second, and third organic dye layers having portions where their respective photovoltaic spectra do not overlap each other are inserted, and the first to fourth electrode materials are added to the above A reading element made of a conductive material having a work function that forms an anisotropic junction with the surface of each organic dye layer on which light is incident,
It is provided on an insulating substrate.

[Action]

In the present invention, by using an organic dye as the photoelectric conversion material, the impedance of the photoelectric conversion layer is high and carriers do not diffuse in the inner surface direction of the layer, so that signal leakage does not occur between adjacent image elements. , P of this organic dye
Type or n-type characteristics and the size of the work function of the electrode material are conveniently selected and combined to form an anisotropic junction on the light-incident side of each organic dye layer. It is possible to stack three types of photoelectric conversion layers having different photovoltaic spectra that absorb only the above to generate a photovoltaic and transmit light other than the wavelength region.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a reading element according to an embodiment of the present invention per pixel, in which 1 is a first electrode, 2 is a first organic dye layer, 3 is a second electrode, 4 is the second
Is an organic dye layer, 5 is a third electrode, 6 is a third organic dye layer, and 7 is a fourth electrode.

In this device, the first, second, and third organic dye layers 2, 4, and 6 are p-type, n-type, and p-type, respectively, and have portions where their respective photovoltaic spectra do not overlap with each other, First and third electrodes
The 1,5 material is a conductive material having a small work function that forms an anisotropic junction with the p-type material and an isotropic junction with the n-type material. The materials of the second and fourth electrodes 3,7 Is a conductive material having a large work function that forms an isotropic junction with a p-type material and an anisotropic junction with an n-type material. When the first, second, and third organic dye layers 2, 4, and 6 are n-type, p-type, and n-type, respectively, the materials of the first and third electrodes 1 and 5 are p-type materials. Is a conductive material having a large work function that forms an isotropic junction and an anisotropic junction with an n-type material, and the second and fourth electrodes 3 and 7 are anisotropic from the p-type material. The n-type material that forms a junction is an electrically conductive material having a low work function that forms an isotropic junction.

More specifically, in the device of this example, the electrodes and the organic dye layers are alternately laminated,
Light is incident from the first electrode 1 side, but the first, second, and third organic dye layers 2, 4, and 6 are the electrodes on the side on which the respective light is incident, that is, the first, second, and third electrodes. Form an anisotropic junction with electrodes 1,3,5 to generate a photovoltaic, and also form an isotropic junction with the electrodes on the opposite side, that is, second, third and fourth electrodes 3,5,7 Is what you are doing. Furthermore, when the photosensitive wavelength range for generating the photoelectromotive force of the first, second and third organic dye layers 2, 4 and 6 is selected as the three color range of red (R) green (G) blue (B) , Between the organic dye layers 2, 4, 6 and the respective electrodes 1, 3, 5 forming an anisotropic junction with each of them, three RGB type outputs are obtained. At this time,
Any combination of the second, third organic dye layers 2, 4, and 6 and the RGB three colors can be used, because each dye transmits light other than the photosensitive wavelength range, and there is no problem.

In order to have the above structure, the organic dye layer is the second organic dye layer 4 if the first and third organic dye layers 2 and 6 are p-type.
Is n-type, or if the first and third organic dye layers 2 and 6 are n-type, the second organic dye layer 4 needs to be p-type. Examples of organic dyes include merocyanine, phthalocyanine, ferosafranine, methylene blue, and chlorophyll. Also,
Examples of n-type organic dyes include porphyrin, rhodamine B, malachite green, and crystal violet. These organic dyes are formed into a thin film, and the formation method is a usual solvent casting method (spinner coat,
Spray coating method and the like) and vacuum deposition method may be used, but they may be used individually or in combination by being trapped in a polymer matrix by a chemical or physical method.

In the electrode material, as a conductive material having a small work function that forms an anisotropic junction with the p-type organic dye and forms an isotropic junction with the n-type organic dye, metals such as A1 and In, SnO ₂ ,
Metal oxides such as ITO and ZnO are used. A conductive material having a large work function that forms an anisotropic junction with an n-type organic dye and an isotropic junction with a p-type organic dye is A
Conductive polymers doped with metals such as u, Cr, Pt, Ni, Tl and acceptors, such as polyacetylene, polypyrrole,
It is used alone or in combination from polythiophene and the like.

Further, in the device having the above structure, a π-conjugated polymer layer may be inserted between the p-type organic dye layer and the lower electrode of the layer. However, when the π-conjugated polymer layer is inserted between the fourth electrode 7 and the third organic dye layer 6, any layer may be used, but when it is inserted on the second or third electrode. The π-conjugated polymer layer should be transparent. The π-conjugated polymer has a conjugated double bond in the skeleton,
It becomes conductive by the doping process. P-type and n-types by doping with electron acceptors (eg, bromine, iodine, bromine iodide, arsenic pentafluoride, and perchloric acid) and electron donors (eg, Na, K, Li, and amines), respectively. It can be a mold material, and its conductivity can be widely controlled from the semiconductor region to the metal region. Also, π
The conjugated conductive polymer layer may of course be formed by another method, but it is advantageous to form it by an electrolytic polymerization method. Membrane synthesized by electrolytic polymerization method is formed only on multiple electrodes,
It is very convenient for element isolation. In the case of forming the π-conjugated conductive polymer layer by another method, for example, a vapor deposition method, an insulating thin film which is not doped is formed once, and then only the portion on the metal electrode is selectively doped. It is then necessary to make it conductive. However, according to the electrolytic polymerization method, this step can be simplified, and the distance between the elements can be reduced to the limit where the polymerized film on the electrodes goes around, which is advantageous for miniaturization and integration.

In order to form the element having the above structure as an organic long thin film color reading element divided into pits, it suffices to simply form all the elements, but one electrode is always used as a common electrode in a circuit for extracting an output. Therefore, any one of the first to fourth electrodes may be formed as a common electrode. Therefore, the organic long thin film color reading device according to the present embodiment is configured by dividing one electrode among the first to fourth electrodes into a common electrode and the other electrode for each pit.
A cross-sectional view of the element is shown in FIG. In this example, the fourth electrode 7
Is used as a common electrode. At this time, the first, second, and third organic dye layers 2, 4, and 6 are formed in a flat plate shape, but even if they are created in this way, they are formed between adjacent pits due to the high impedance of the organic dye. No signal is leaked, and the first and second organic dye layers 2, 4 and the second and third organic dye layers 4, 6 are in contact with each other, but no signal is leaked during this period. For this reason, a lithographic technique is not required at the time of manufacturing, and since it can be manufactured by a casting method or a vapor deposition method, it is easy to increase the area.

Next, the operation principle of the color reading element according to the present embodiment will be described. The first, second, and third organic dyes are n-type, p-type, respectively.
Type, n-type is the case of p-type, n-type, and p-type with opposite polarities and the operating principle is the same, so here is the case of p-type, n-type, and p-type I will describe.

Now, the first, second, and third organic dyes are p-type, n-type, and p-type, respectively, and their photovoltaic spectra are wavelengths λ ₁ and λ, respectively.
_It has a maximum at ₂ and λ ₃ , and corresponds to the wavelength regions of red, green, and blue, respectively. That is, λ ₁ is in the region of 600 to 680 nm,
₂ is in the region of 500 to 600 nm, and λ ₃ is in the region of 400 to 500 nm. The state at this time is shown in FIG. In addition,
Any combination of wavelengths λ ₁ , λ ₂ , λ ₃ and their photovoltaic generation wavelength regions may be used, and this example does not limit the present invention.

It can be seen that when the present element is configured in this manner, the present element is a series of organic photoelectric conversion elements that have been conventionally proposed. That is, the first, second, first, third and first
The portion formed of the organic dye layer 2 produces a negative photoelectromotive force on the side of the first electrode 1 with respect to the light having the wavelength λ ₁ (red). In addition, the portion composed of the second and third electrodes 3 and 5 and the second organic dye layer 4 generates a positive photovoltaic force on the side of the second electrode 3 with respect to light of wavelength λ ₂ (green). . Further, the portion composed of the third and fourth electrodes 5 and 7 and the third organic dye layer 6 has a wavelength of λ ₃ (blue)
Negative light is generated on the side of the third electrode 5 with respect to the light.
This state is shown in FIG. 4 in a schematic view in which each photoelectric conversion element is replaced with a diode.

A case where light including various wavelengths is incident on the device from the first electrode 1 side will be described. The light (red) in the region near the wavelength λ ₁ of the incident light is absorbed by the first organic dye layer 2 and the first light is absorbed between the first electrode 1 and the second electrode 3.
A negative photovoltaic force V ₁ (V ₁ > 0) is generated on the electrode 1 side of the. At this time, light other than the region of wavelength λ ₁ passes through the first organic dye layer 2 and reaches the second organic dye layer 4 with almost no dimming. Of the light reaching the second organic dye layer 4, the light (green) in the region near the wavelength λ ₂ is absorbed by the second organic dye layer 4, and is absorbed between the second electrode 3 and the third electrode 5. A positive photovoltaic voltage V ₂ (V ₂ > 0) is generated on the second electrode 3 side. At this time, the light other than the region of the wavelength λ ₂ passes through the second organic dye layer 4 and reaches the third organic dye layer 6 with almost no dimming. The light that has reached the third organic dye layer 6 is almost the light (blue) in the region near the wavelength λ ₃ except for the ultraviolet light and the infrared light, and is absorbed by the third organic dye layer 6 to generate the third light. Between the third electrode 5 and the fourth electrode 7 of
Side negative photovoltaic power V ₃ (V ₃ > 0) is generated. In this way, the incident light is divided into three (red (R) green (G) blue (B))
It becomes possible to obtain the respective outputs V ₁ , V ₂ and V ₃ by decomposing into RGB components.

Next, an example of a circuit for extracting the outputs V ₁ , V ₂ , V ₃ corresponding to the RGB components to the outside will be described. Various methods are conceivable for the circuit for extracting the output, and the example shown in FIG. 5 below does not limit the present invention. In FIG. 5, the fourth electrode 7 is grounded and used as a common electrode. It is desirable that the common electrode is not divided into pits in terms of element formation, but a flat electrode is used. The first, second, and third electrodes 1, 3, and 5 are input to operational amplifiers 81, 82, and 83, respectively, and the output voltage between the fourth electrode 7 is amplified and output. If the amplification factor of the operational amplifier is omitted, the outputs of the operational amplifier 81, operational amplifier 82, and operational amplifier 83 are (−V ₁ + V ₂ −V ₃ ), (V ₂ −
V ₃ ), (−V ₃ ), and from this we can easily calculate V ₁ , V
₂ and V ₃ can be taken as output. This element is the second
By arranging a plurality of lines as shown in the figure, a full-color organic long thin film reading device capable of reading a one-line color image by the RGB system has become possible.

Further, the reading element according to the present embodiment has the following features as compared with the conventional reading element. Conventionally, an inorganic substance such as amorphous silicon has been used for the layer having a photoelectric conversion function, but in the present embodiment, the use of the organic dye layer simplifies the manufacture. Furthermore, due to its high impedance, the movement of carriers in the in-plane direction of the film is small, and even if a flat plate-shaped film is used, electrical isolation from the adjacent element can be effectively performed and a large screen can be easily obtained. . In addition, since three photoelectric conversion elements corresponding to the three RGB colors are used in a stacked type and also have a color filter effect, the element area is 1/3 compared to the conventional planar RGB method, and the color filter is unnecessary. is there. That is, it is possible to realize colorization at the same pit pitch as that of the conventional black-and-white type long thin film element without reducing the pixel density. Further, by inserting a π-conjugated conductive polymer layer between the p-type organic dye layer and the electrode therebelow, the photoelectric conversion ability of the organic dye layer can be increased.

 Hereinafter, a specific example will be described in more detail.

Example 1 Vacuum deposition using Cr-Au as a common electrode (thickness 800
Å, 1000 Å) on a blue plate glass substrate with a merocyanine dye (NK-2045, manufactured by Japan Photosensitive Dye Company) by vacuum evaporation.
It is provided as a flat plate with a thickness of 00Å, and a SnO ₂ film (surface resistance of about 200 Ω / □) is divided into pits by sputtering, and 5,10,15,20- Tetra (4
-Pyridyl) porphyrin Zn complex is vacuum-deposited in a plate shape with a thickness of about 700Å, and Au is further applied on it with a transmittance of about 70%.
(At 550nm) divided into pits and vacuum-deposited, then vacuum-deposited Ni complex of phthalocyanine with a thickness of about 1000Å into a flat plate and finally making Al semitransparent and pitted. It was divided into pieces and vacuum-deposited to obtain an organic long thin film color reading element 1.

Example 2 Thickness of 4cm x 5.5cm glass substrate by vacuum evaporation method
A 1000 Å Cr layer is provided, and an Au layer is further formed thereon to a thickness of 2000 Å by a vacuum vapor deposition method as a working electrode.
The effective working electrode area is 1 mm x 3 mm, and 10 effective working electrode portions are arranged side by side by 5 μm. Next, 0.07 g of pyrrole, 0.35 g of N-methylpyrrole, and 0.7 g of tetraethylammonium perchlorate are dissolved in 100 ml of acetonitrile to prepare a reaction solution. Using a platinum (Pt) electrode as the counter electrode and SCE (saturated calomel electrode) as the reference electrode, dip it in the above reaction solution together with the working electrode, and then, under a nitrogen gas atmosphere, use the working electrode as the anode and maintain a constant gap between the electrode and the counter electrode. Apply a current (0.15mA) for 90 minutes to form a π-conjugated polymer layer on the working electrode to a thickness of about 2000Å, wash it with acetonitrile and vacuum dry it to obtain a π-conjugated polymer layer sample. obtain. Next, a merocyanine dye (NK-2045 manufactured by Nippon Senso Dye Co., Ltd.) was further deposited on the π-conjugated polymer layer sample by vacuum deposition.
It is formed to a thickness of 00Å, and then a SnO ₂ film (surface resistance of about 200Ω / □) is formed on the plate as a common electrode by sputtering, and 5,10,15,20-tetra ( 4-
Pyridyl) porphyrin Zn complex is vacuum-deposited in a plate shape with a thickness of about 700Å, and Au is further transmitted on it with a transmittance of about 70%.
(At 550 nm) divided into pits and vacuum-deposited, then vacuum-deposited Ni complex of phthalocyanine to a thickness of about 1000 Å, and finally made Al semitransparent and pitted. Each was vacuum-deposited to obtain an organic long thin film color reading element 2.

Example 3 With polyvinyl chloride on an ITO substrate (surface resistance 50Ω / □)
A solution of 5,10,15,20-tetra (4-pyridyl) porphyrin (37:70 in weight ratio) in tetrahydrofuran was formed by a spin coating method to a film thickness of about 2000Å, on which Au was transmitted by about 70% ( at 550 nm) divided into pits and vacuum-deposited, and then metal-free phthalocyanine is added to about 10
It is vacuum-deposited into a flat plate with a thickness of 00Å, and also has an Al transmittance of about
It is divided into pits so as to be 60% (at 550nm), vacuum-deposited, and then a chloroform solution of Rhodamine B is formed on it by spin coating to a film thickness of about 1000Å, and then Au is transmitted therethrough. The organic long thin film color reading element 3 was obtained by dividing each pit so as to have a rate of about 70% (at 550 nm) and performing vacuum evaporation.

Each of the color reading elements 1 to 3 obtained in the above specific examples 1 to 3 was read as shown in FIG. 5, and light irradiation was performed from above the reading element. Light irradiation is standard color chart (JIS Z8721
-1964) was irradiated with a tungsten lamp and the reflected light was used. When the gain of the operational amplifier shown in FIG. 5 was adjusted for each reading element, three readings with good reproducibility were obtained for all reading elements.

The electrical isolation between the devices was tested as follows. The entire reading element is fixed on the micro stage, and the element is irradiated with light. The light is arranged so that the focal point of monochromatic light emitted from the spectroscope is on the device. At this time, the boundary between the light-irradiated portion and the light-shielded portion is sharp. And
The microstage was operated to examine the difference in photovoltaic power between adjacent elements. At this time, it was found that even if a certain element is irradiated with light, the adjacent element to which no light is irradiated does not generate a photoelectromotive force. Further, even when light is irradiated onto the gap between two adjacent elements, the element not irradiated with light does not generate a photoelectromotive force, and the photocarriers generated in the organic dye layer diffuse in the in-plane direction of the layer. It can be seen that the photoelectromotive force is generated without being efficiently separated only in the vertical direction.

Further, each of the color reading elements 1 to 3 was molded with a silicone-based resin, and changes in the above characteristics with time were measured. Almost no change with time was observed in any of the color reading elements for at least 4 months.

〔The invention's effect〕

As described above, according to the present invention, the first to fourth electrodes are sequentially arranged, and the p-type, n-type, p-type or n-type, p-type Surface of n-type, where the first, second, and third organic dye layers having the portions where the respective photovoltaic spectra do not overlap with each other are inserted, and each electrode material is on the light incident side of each organic dye layer Since a reading element made of a material having a work function that forms an anisotropic junction with is provided on an insulating substrate, there are three types of photoelectric conversion layers having different filter characteristics and high impedance and different photovoltaic spectra. Can be stacked, and an organic long thin film color reading element that does not require a color filter and can correspond to three RGB colors can be obtained at low cost without lowering the pixel density.

[Brief description of drawings]

FIG. 1 is a sectional view of a color reading element per pixel of a color reading element according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a color reading element divided into pits according to an embodiment of the present invention.
FIG. 3 is a schematic diagram showing a photovoltaic spectrum of an organic dye,
FIG. 4 is an equivalent circuit diagram of the color reading device according to the present invention, and FIG. 5 is a circuit diagram of RGB output of the color reading device according to an embodiment of the present invention. 1,11,12,13 …… First electrode, 2 …… First organic dye layer, 3,3
1,32,33 …… Second electrode, 4 …… Second organic dye layer, 5,51,5
2,53 ... third electrode, 6 ... third organic dye layer, 7 ... fourth
electrode. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Torahiko Ando 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Material Research Laboratory (56) Reference JP-A-59-227171 (JP, A) 59-227172 (JP, A) JP 59-229863 (JP, A)

Claims (6)

(57) [Claims] 1. A flat plate-shaped light-transmitting first, second, and third electrode and at least three electrodes of a flat plate-shaped fourth electrode are composed of a plurality of parts divided for each pit. , The second
A reading element in which first, second, third, and fourth electrodes are arranged in sequence, and first, second, and third organic dye layers having photoelectric conversion capability are inserted between the electrodes. , The first, second, and third organic dye layers are p-type, n-type,
Type and p-type, or n-type, p-type, and n-type, and have portions where their respective photovoltaic spectra do not overlap with each other, and the first to fourth electrode materials are the organic dye layers described above. A reading element which is a conductive material having a work function so as to form an anisotropic junction with a surface on which light is incident and an isotropic junction with a surface on the opposite side of the light incident surface. An organic long thin-film color reading device, characterized in that it is provided on an insulating substrate with the fourth electrode facing downward. 2. The organic long thin film color reading device according to claim 1, wherein the insulating substrate is made of a transparent material. 3. The first organic dye layer contains at least a phthalocyanine skeleton, the second organic dye layer contains at least a tetra (4-pyridyl) porphyrin skeleton, and the third organic dye layer has at least a merocyanine structure. The organic long thin film color reading device according to claim 1 or 2, further comprising: 4. The π-conjugated polymer layer is inserted between the p-type organic dye layer and the electrode below the layer, and the π-conjugated polymer layer is inserted. 5. The organic long thin film color reading device described in any one of 1. 5. The organic long thin film color reading device according to claim 4, wherein the π-conjugated polymer layer is formed by an electric field polymerization method. 6. The π-conjugated polymer layer is polypyrrole,
The poly-N-substituted pyrrole, a copolymer of pyrrole and an N-substituted pyrrole, polythiophene, polyaniline, polyfuran, and polyazulene are formed at least one kind, Claim 4 or 5 characterized by the above-mentioned. The organic long thin film color reading device described in the item.