JP2008126471A - Printer head inspection apparatus, printer head inspection method, and printer head manufacturing method - Google Patents

Abstract

A printer head inspection apparatus capable of inspecting light emission luminance characteristics and light emission wavelength characteristics of a printer head by a simplified method.
A printer head inspection apparatus CA according to the present invention includes a plurality of light emitting elements 9 arranged in one direction, and an electrostatic latent image is formed on an image carrier by light emitted from the plurality of light emitting elements 9. A bandpass filter 55 that transmits only light having a wavelength that matches the photosensitive characteristic of the image carrier, and light having a wavelength that matches the photosensitive characteristic of the image carrier. The imaging device 53 having sensitivity, the band-pass filter 55 and the image of the light emitting state of the light emitting element 9 imaged using the imaging device 53 are processed, and the image carrier within the wavelength range that is exposed to light. And an image processing device 58 for detecting the light emission luminance of the light emitting element 9.
[Selection] Figure 1

Description

  The present invention relates to a printer head inspection apparatus used in a line printer, a printer head inspection method, and a printer head manufacturing method.

  Conventionally, a line printer (image forming apparatus) is known as a printer using an electrophotographic system. In this line printer, devices such as a charger, a line-shaped printer head, a developing device, and a transfer device are arranged close to an image carrier (for example, a photosensitive drum) serving as an exposed portion. In other words, an electrostatic latent image (image formation) is formed on the image carrier charged by the charger by performing selective light emission operation of a light emitting element provided in the printer head, and this electrostatic latent image is formed. Is developed with toner supplied from a developing device, and the toner image is transferred onto a sheet by a transfer device.

  As a light emitting element provided in a line-shaped printer head, an LED element or an EL element is used. If necessary, a lens array in which a plurality of gradient index lenses are arranged is disposed between the light emitting element and the image carrier. In the printer head configured as described above, the light emitted from the light emitting element passes through the lens array and forms an equal-magnification image on the image carrier so that an electrostatic latent image is formed on the image carrier. It is formed (for example, see Patent Document 1).

  In such a line printer, research aimed at mass production has been conducted, and research on a measurement apparatus and a measurement method for measuring necessary characteristics more precisely and efficiently has been actively conducted. Since the configuration and method of the printer head are diverse, there are various items to be measured and evaluated according to each configuration and method. In particular, from an optical point of view, IVL characteristics (current voltage luminance characteristics), light emission luminance characteristics, light emission wavelength characteristics, and the like are emphasized.

  Here, in a line printer, it is necessary to uniformly control the characteristics of hundreds to thousands of light emitting elements formed on the printer head. In the development and process management of the printer head, various characteristics are measured and evaluated. Is an indispensable matter. For example, in a printer head using an organic EL element, it is known that the peak of the emission wavelength shifts due to manufacturing variations of layers that contribute to light emission, which deviates from the photosensitive characteristics (light reception wavelength characteristics) of the image carrier. In such a case, there is a problem that sufficient latent image forming power cannot be obtained on the image carrier. Therefore, it is necessary to inspect the light emission luminance and the light emission wavelength of the light emitting elements formed on the printer head one by one, and the time and cost required for the inspection process have been enormous.

On the other hand, with respect to printer heads using organic EL elements or the like, mass production technology has not yet been established, and the inspection method is also referred to the existing inspection method for organic EL displays as disclosed in Patent Document 2. This is what is being done. For example, when inspecting the light emission luminance and light emission wavelength of a printer head, first, the printer head is scanned with a CCD camera, and the light emission luminance characteristics of each light emitting element formed on the printer head are inspected. Subsequently, the printer head is scanned again with a CCD camera provided in the spectroscope, and the characteristics of the emission wavelength of each light emitting element are inspected.
JP-A-9-226171 JP 2006-266750 A

  However, in this method, since it is necessary to scan a light emitting element of several thousand dots twice, there is a problem that the time and cost required for the measurement become enormous. On the other hand, in the printer head, unlike the case of the display, it is not necessary to inspect the detailed light emission wavelength characteristics including chromaticity for each light emitting element. That is, in the printer head, if the emission wavelength of the light emitting element is within a range suitable for the photosensitive characteristics of the image carrier, and the amount of light obtained within that range is within a predetermined range, a sufficient latent image is obtained. The forming power can be obtained, and therefore it can be determined as a non-defective product. For this reason, applying the method applied to the display to the printer head as it is is wasteful in the process and increases the manufacturing cost. From the above background, a method for inspecting a printer head by a more simplified method has been demanded.

  The present invention has been made in view of such circumstances, and provides a printer head inspection apparatus and inspection method capable of inspecting light emission luminance characteristics and light emission wavelength characteristics of a printer head by a simplified method. For the purpose. It is another object of the present invention to provide a printer head manufacturing method that can reduce the manufacturing cost by using such an inspection method.

  In order to solve the above-described problems, a printer head inspection apparatus according to the present invention includes a plurality of light emitting elements arranged in one direction, and electrostatic latent images are formed on an image carrier by light emitted from the plurality of light emitting elements. A printer head inspection apparatus for forming an image, wherein a band-pass filter that transmits only light having a wavelength that matches the photosensitive characteristics of the image carrier and sensitivity to light having a wavelength that matches the photosensitive characteristics of the image carrier. A light emitting luminance of the light emitting element within a wavelength range that the image carrier is exposed to, and processing an image of a light emitting state of the light emitting element imaged using the bandpass filter and the imaging device And an image processing device for detecting the image. According to this configuration, since the emission wavelength can be inspected only by introducing an inexpensive bandpass filter compared to the spectroscope, the cost required for the inspection process can be reduced compared to the case of using the spectroscope. . In addition, since the inspection of the emission luminance and the inspection of the emission wavelength can be performed at the same time, the inspection time can be significantly shortened compared to the case where the light emitting element is scanned twice using a spectroscope.

  A printer head inspection method according to the present invention includes a plurality of light emitting elements arranged in one direction, and forms an electrostatic latent image on an image carrier by light emitted from the plurality of light emitting elements. A bandpass filter that transmits only light having a wavelength that matches the photosensitive characteristic of the image carrier and an imaging device that is sensitive to light having a wavelength that matches the photosensitive characteristic of the image carrier. Imaging a light emitting state of the light emitting element, processing an image of the light emitting state of the light emitting element, detecting a light emission luminance of the light emitting element within a wavelength range in which the image carrier has sensitivity, and the light emission And a step of determining the quality of the light emitting element based on the light emission luminance of the element. According to this method, since the emission wavelength can be inspected only by introducing an inexpensive bandpass filter compared to the spectroscope, the cost required for the inspection process can be reduced compared to the case of using the spectroscope. . In addition, since the inspection of the emission luminance and the inspection of the emission wavelength can be performed at the same time, the inspection time can be significantly shortened compared to the case where the light emitting element is scanned twice using a spectroscope.

  In the present invention, in the step of imaging the light emitting element, it is desirable to divide the plurality of light emitting elements into a plurality of measurement sections and to image the plurality of light emitting elements for each of the measurement sections. According to this method, since a plurality of light emitting elements included in one measurement section are collectively imaged and image processed, the inspection efficiency is improved as compared with the case where each light emitting element is imaged and image processed. Can do.

  The printer head manufacturing method of the present invention includes a step of forming a plurality of light emitting elements on a substrate, and an inspection step of inspecting light emission luminance and light emission wavelength of the plurality of light emitting elements. This is performed by the printer head inspection method of the present invention. According to this method, since the inspection process of the printer head is performed by the above-described inspection method of the present invention, the manufacturing time of the printer head can be shortened and the manufacturing cost can be reduced.

  In the present invention, the light-emitting element includes a functional layer including one or more layers including a light-emitting layer between the reflective film and the semi-transmissive reflective film, and between the reflective film and the semi-transmissive reflective film. It is desirable that only light having a resonance wavelength corresponding to the optical distance is amplified and extracted. According to this method, a printer head having high emission luminance and a sharp spectrum can be provided. In this case, the peak wavelength may shift due to an abnormal thickness of the functional layer, but such a shift in the peak wavelength can be recognized as an abnormal luminance by the bandpass filter. The inspection time can be greatly shortened.

  In the present invention, in the step of forming the light emitting element, it is desirable to set conditions for forming the functional layer based on the inspection results of the light emitting elements of other printer heads that have been inspected previously. For example, in the step of forming the light emitting element, one or more layers constituting the functional layer are formed by a wet film forming method, and the viscosity of the liquid material for forming the layer is first inspected It is desirable to set based on the inspection result of the light emitting element of the printer head. In this way, the inspection process and the manufacturing process are performed in parallel, and the latest inspection data is fed back to the manufacturing conditions of the functional layer of the next lot, thereby enabling efficient manufacturing and improving the manufacturing yield. it can.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an inspection apparatus of the present invention. The inspection apparatus CA images the line-shaped printer head 1 and inspects display unevenness and pixel defects of the printer head 1 based on the captured image data. The printer head 1 includes a plurality of light emitting elements 9 arranged in one direction as pixels, and forms an electrostatic latent image on a photosensitive drum as an image carrier by light emitted from the plurality of light emitting elements 9. To do. In the following description, “line printer head” is simply abbreviated as “line head”.

  The light emitting element 9 is, for example, an organic electroluminescence element (hereinafter, “electroluminescence” is abbreviated as “EL”), and includes a functional layer including one or more layers including a light emitting layer between a pair of electrodes. Yes. The functional layer is disposed between the reflective film and the semi-transmissive reflective film, and only the light having the resonance wavelength corresponding to the optical distance between the reflective film and the semi-transmissive reflective film is amplified and extracted. ing. In this type of light-emitting element 9, it is known that the peak of the emission wavelength shifts due to manufacturing variations of layers that contribute to light emission. The light-emitting characteristic of the light-emitting element and the photosensitive characteristic of the photosensitive drum (light-receiving wavelength characteristic) Is substantially affected by the latent image forming power on the photosensitive drum. Therefore, in the inspection apparatus CA, it is important to inspect the light emission characteristics of the light emitting element 9, particularly the emission wavelength within the range of the peak wavelength and the half width of the light emitting element 9 and the wavelength at which the photosensitive drum is sensitive.

  The inspection apparatus CA includes a stage 51 as a support that supports the line head 1, a stage control device 52 that controls the position of the stage 51, a CCD camera 53 as an imaging device that images the line head 1, and a CCD camera 53. A camera control device 54 that controls the driving of the CCD, a band-pass filter 55 as an optical filter attached to the CCD camera 52, a head control device 56 that controls the lighting state of the line head 1, a stage control device 52, and a camera control And a control device 57 for controlling the device 54 and the head control device 56 in an integrated manner.

  The stage 51 is movable with respect to the arrangement direction of the light emitting elements 9 and the rotation direction with the arrangement direction as a central axis. The stage 51 is moved in each direction by a control signal from the stage control device 52 and The position is adjusted. The stage control device 52 is configured to transmit a control signal to the stage 51 based on a command from the control device 57.

The CCD camera 53 includes an image sensor that is sensitive to light having a wavelength that matches the photosensitive characteristics of the photosensitive drum. In the CCD camera 53, a band pass filter 55 having a center wavelength λ ₀ and a half-value width W ₀ matching the photosensitive characteristics (light receiving wavelength characteristics) of the photosensitive drum as shown in FIG. It has been. The band-pass filter 55 transmits only light having a wavelength that matches the photosensitive characteristics of the photosensitive drum, and absorbs or reflects light in other wavelength ranges. In the present embodiment, the center wavelength λ ₀ of the bandpass filter 55 is 660 nm, and the half-value width W ₀ is 60 nm. Accordingly, only red light in the range of 630 nm to 690 nm, which is the light receiving wavelength range of the photosensitive drum, is transmitted through the band pass filter 55. In the CCD camera 53, the light emission state of the light emitting element 9 observed through the band pass filter 55 is imaged, and the distribution of light emission luminance within the transmission wavelength range of the band pass filter 55 is transmitted to the control device 57 as image data. It is like that. The CCD camera 53 is equipped with a microscope (not shown) so that the light emission luminance can be individually measured for each of the plurality of light emitting elements 9.

  The head control device 56 receives a control signal from the control device 57 and controls lighting / extinguishing of each light emitting element 9 of the line head 1 based on the control signal. A power supply device (not shown) is connected to the head control device 56. The power supply device is controlled by the control device 57 and outputs a driving voltage corresponding to each light emitting element 9 of the line head 1.

  The control device 57 includes a computer 58 and a monitor 59. The computer 58 includes a CPU, a ROM, a RAM, a disk device, and the like. The computer 58 controls the stage 51, the camera control device 54, and the head control device 56 in an integrated manner, and captures an image of the light emitting element 9 captured by the CCD camera 53. It functions as an image processing apparatus for processing. The computer 58 performs an averaging process, a binarization process, etc. on the image data from the CCD camera 53, detects the position of each light emitting element 9 of the line head 1 based on the calculation result, 9 defects (non-light emission, etc.) and display irregularities are detected. The ROM and RAM of the computer 58 store programs and various data (the size of the line head 1, the pixel pitch, the light emission luminance in the light receiving wavelength range of the photosensitive drum, the light emission threshold value, etc.) for executing calculations. Has been.

  Next, a method for inspecting the line head 1 by the inspection apparatus CA and a method for manufacturing a line head using the same will be described. First, the line head 1 manufactured in the first lot is placed on the stage 2, and control signals are output from the computer 58 to the stage control device 52, the camera control device 54, and the head control device 56, the stage 51, and the CCD camera. 53 and the lighting state of the line head 1 are initialized. Then, the computer 58 instructs the head control device 56 to turn on the light emitting elements 9 in all or a predetermined section of the line head 1 and move the stage 51 so that a predetermined portion of the line head 1 is within the field of view of the CCD camera 53. Position to enter.

Next, divide the line head 1 to a plurality of measurement sections measurement sections S _1, S 2, _... imaging the line head 1 for each S _n. In this case, the measurement field _{S 1,} S 2, ... the size of _{S n} is set by the resolution and viewing angle of the CCD camera 53. The light emission state of the light emitting element 9 in the measurement section is imaged by the CCD camera 53 while sequentially moving the stage 51 by the size of the set measurement section. Image data of each measurement section S ₁ , S ₂ ,... S _n is stored in the RAM of the computer 58 via the camera control device 54.

  In the computer 58, image processing such as averaging processing and binarization processing is performed on the image of the light emitting element 9 in each measurement section. Then, the light emission luminance, the light emission area, and the like of each light emitting element 9 are detected by this image processing. This emission luminance is the emission luminance within the wavelength range transmitted through the bandpass filter 55, and is an effective emission luminance that can contribute to the formation of an electrostatic latent image on the photosensitive drum. The computer 58 calculates the light emission luminance of one pixel based on the detected light emission luminance, the light emission area, and the like, and the light emission luminance of this one pixel and the threshold value of the light emission luminance stored in the ROM of the computer 58 (the upper limit of the light emission luminance). And the lower limit). When the emission luminance of one pixel falls within the range defined by the upper limit and the lower limit, the pixel is determined as a normal pixel, and when out of the range, the pixel is determined as a defective pixel. .

3 and 4 is an example of the image data of the measuring compartment S _m which is displayed on the monitor 59. FIG. 3 is an example of image data when light is normally emitted, and FIG. 4 is an example of image data when a defective pixel is included. 3A and 4A, the shaded area indicates the overlap between the emission spectrum of the light emitting element and the transmission spectrum of the bandpass filter, and the area of the shaded area is the transmission wavelength range of the bandpass filter. The magnitude of the light emission luminance of the light emitting element is shown within (that is, within a wavelength range that can contribute to formation of an electrostatic latent image on the photosensitive drum).

As shown in FIG. 3A, when the center wavelength λ ₁ and half-value width W ₁ of the light-emitting element coincide with the center wavelength λ ₀ and half-value width W _{0 of the} bandpass filter, the emission spectrum and band of the light-emitting element are obtained. The overlap with the transmission spectrum of the pass filter is the largest, and the emission luminance detected by the computer is the largest. If this condition is obtained in all the pixels (light emitting elements 9) is displayed all the pixels brighter in the measurement compartment S _m as shown in FIG. 3 (b), the light emitting luminance of each pixel in advance It falls within the threshold range of the set emission brightness. Therefore, all the pixels are determined as normal pixels, and the entire line head is determined as a non-defective product.

On the other hand, as shown in FIG. 4A, when the center wavelength λ ₂ of the light emitting element is shifted to a shorter wavelength side than the center wavelength λ _{0 of the} bandpass filter due to an abnormal film thickness of the functional layer, The overlap between the emission spectrum and the transmission spectrum of the bandpass filter is reduced, and the emission luminance detected by the computer is also reduced. If this condition occurs in all the pixels (light emitting elements 9), all the pixels of the measuring compartment S _m as shown in FIG. 4 (b) is displayed dark, light-emitting luminance of each pixel is set in advance Thus, the light emission luminance is out of the threshold range. Therefore, all the pixels are determined to be abnormal pixels, and the entire line head is also determined to be defective.

On the other hand, the state when generated in some pixels, only a subset of the pixels in the measurement compartment S _m as shown in FIG. 4 (c) is displayed dark and the other pixels are brightly displayed. In this case, only some pixels are determined to be abnormal pixels, and other pixels are determined to be normal pixels. However, if an abnormality is detected in some pixels, the line head is defective in displaying a line defect. Therefore, the entire line head is determined as a defective product.

  Note that FIG. 4B illustrates the case where the center wavelengths of all the light emitting elements are shifted, but the center wavelength of the light emitting elements is not necessarily shifted uniformly in all the light emitting elements. Since the number of light emitting elements formed on the line head ranges from several hundred to several thousand, there is a difference in the film thickness of the functional layer due to differences in manufacturing conditions between the center of the line head and both ends of the line head. Because there is. For example, when the light emitting element has an optical resonator structure and only light having a resonance wavelength corresponding to the film thickness of the functional layer is amplified and extracted, the variation in the film thickness of the functional layer is the peak wavelength of the light emitting element. It is directly related to the variation, and the variation of the peak wavelength is detected as the variation of the emission luminance through the band pass filter.

  For example, when the functional layer is formed by a wet film forming method such as an ink jet method or a spin coat method, depending on the viscosity of the liquid material for forming the functional layer, local variations in the thickness of the functional layer may occur. There is. In particular, when the functional layer is formed by the ink jet method, the discharge amount of the liquid material may change due to variations in the viscosity of the functional layer, and the film thickness of the functional layer may be non-uniform throughout the line head. In addition, when the concentration of the solvent in the drying atmosphere when the functional layer is dried is greatly different between the center and both ends of the line head, the film thickness at the center of the line head is larger than the film thickness at both ends of the line head. As a result, the light emission luminance of the light emitting element detected through the band pass filter increases at the center of the line head and decreases at both ends of the line head.

  In such a line head, the light emission luminance of the light emitting element through the band pass filter locally changes according to the position of the line head. In this case, the pixel is partially determined to be a normal pixel, but the entire line head is determined to be defective unless all the light emitting elements are determined to be normal pixels.

In FIG. 4, although the central wavelength lambda ₂ of the light emitting element has been described as being shifted to the shorter wavelength side than the center wavelength lambda ₀ of the bandpass filter, the above-described circumstances, the central wavelength lambda ₂ band of the light emitting element The same applies to the case where the center wavelength λ ₀ of the pass filter is shifted to the longer wavelength side.

  When the inspection process of the line head 1 of the first lot is completed as described above, the manufacturing conditions of the light emitting elements of the line head of the second lot are set based on the inspection result. Specifically, when one or more layers constituting the functional layer of the light-emitting element are formed by a wet film formation method such as an ink jet method, the light emission luminance of the light-emitting element as a whole is low or high as the line head. In the case of shifting to the side, the light emission of each light emitting element is adjusted by adjusting the discharge amount, the number of discharges of the liquid material for forming the layer, the viscosity of the liquid material for forming the layer, or the like. The brightness is set to fall within a threshold range stored in the ROM of the computer. Further, when the light emission luminance varies greatly over the entire line head, the viscosity of the liquid material is adjusted so that a uniform film thickness can be obtained over the entire line head. In addition, if there is a difference in luminance between the center and both ends of the line head depending on the drying conditions of the functional layer, in order to bring the drying speed of the functional layer at the center close to the drying speed of the functional layers at both ends, Take measures such as increasing the concentration of the solvent atmosphere during drying.

  In this way, the inspection process and the manufacturing process are performed in parallel, and the latest inspection data is fed back to the manufacturing conditions of the functional layer of the next lot, thereby enabling efficient manufacturing and improving the manufacturing yield. it can. Then, by repeating the manufacturing process and the inspection process of the line head in this way, a plurality of lots of line heads are sequentially manufactured.

  As described above, in the inspection apparatus CA of the present embodiment, when inspecting the light emission state of the light emitting element 9, only the wavelength that matches the photosensitive characteristic (light receiving wavelength characteristic) of the photosensitive drum is transmitted to the CCD camera 53. The band-pass filter 55 is attached to image the light emitting element 9. For this reason, the emission wavelength can be inspected only by introducing an inexpensive bandpass filter compared to the spectroscope, and the cost required for the inspection process can be reduced as compared with the case of using the spectroscope. In addition, since the inspection of the emission luminance and the inspection of the emission wavelength can be performed at the same time, the inspection time can be significantly shortened compared to the case where the light emitting element is scanned twice using a spectroscope.

Further, in the step of imaging the light emitting element, a plurality of light emitting elements 9 a plurality of measurement sections S _1, S 2, _... is divided into S _n, and imaging the plurality of light emitting elements 9 for each respective said measuring compartment Therefore, the plurality of light emitting elements 9 included in one measurement section can be collectively imaged and processed, and the inspection efficiency can be improved as compared with the case where each light emitting element 9 is imaged and image processed one by one.

[Image forming apparatus]
Next, an embodiment of an image forming apparatus provided with the printer head of the present invention will be described. FIG. 5 is a schematic configuration diagram of an image forming apparatus 100 including the line head 1 which is an embodiment of the printer head of the present invention. The line head 1 is manufactured by using the above-described printer head inspection method of the present invention.

  The image forming apparatus 100 includes a photosensitive drum 16 as an image carrier in the vicinity of the travel path of the transfer medium 22. Around the photosensitive drum 16, an exposure device 15, a developing device 18, and a transfer roller 21 are sequentially arranged along the rotation direction of the photosensitive drum 16 (indicated by an arrow in the drawing). The photosensitive drum 16 is rotatably provided around the rotation shaft 17, and a photosensitive surface 16 </ b> A is formed on the outer peripheral surface of the photosensitive drum 16 at the central portion in the rotation axis direction. The exposure device 15 and the developing device 18 are arranged in a long axis shape along the rotation shaft 17 of the photosensitive drum 16, and the width in the long axis direction substantially coincides with the width of the photosensitive surface 16A.

  In this image forming apparatus 100, first, in the process of rotating the photosensitive drum 16, the surface of the photosensitive drum 16 (photosensitive surface 16 </ b> A) is positive (for example, positive) by a charging device (not shown) provided on the upstream side of the exposure device 15. Then, the surface of the photosensitive drum 16 is exposed by the exposure device 15 to form a negative (−) electrostatic latent image LA on the surface. Further, the toner (developer) 20 is applied to the surface of the photosensitive drum 16 by the developing roller 19 of the developing device 18, and the toner image corresponding to the electrostatic latent image LA is formed by the electric attractive force of the electrostatic latent image LA. It is formed. The toner particles are positively (+) charged.

  After the toner image is formed by the developing device 18, the toner image comes into contact with the transfer medium 22 by further rotation of the photosensitive drum 16, and the transfer roller 21 has a polarity opposite to that of the toner particles of the toner image from the back surface of the transfer medium 22. Charge (here, negative (−) charge) is applied, and accordingly, toner particles forming a toner image are attracted from the surface of the photosensitive drum 16 to the transfer medium 22, and the toner image is transferred to the surface of the transfer medium 22. Is transcribed.

  The exposure apparatus 15 includes a line head 1 having a plurality of organic EL elements 9 and an imaging optical element 12 having a plurality of lens elements 13 for imaging the light L emitted from the line head 1 at an erecting equal magnification. I have. The line head 1 and the imaging optical element 12 are held by a head case (not shown) while being aligned with each other, and are fixed on the photosensitive drum 16.

  The line head 1 includes a light emitting element array 10 in which a plurality of organic EL elements 9 are arranged along the rotation axis 17 of the photosensitive drum 16, and a drive element group including a drive element (not shown) that drives the organic EL elements 9. And a control circuit group 11 for controlling driving of these drive elements (drive element group). The organic EL element 9, the drive element group, and the control circuit group 11 are integrally formed on a long and thin element substrate (base) 2.

  The imaging optical element 12 is arranged (arranged) in a zigzag pattern in which the lens elements 13 having the same configuration as the SELFOC (registered trademark) lens element manufactured by Nippon Sheet Glass Co., Ltd. are arranged along the rotation axis 17 of the photosensitive drum 16. A lens element array 14 is provided.

  FIG. 6 is a schematic configuration diagram of one pixel of the line head 1. The line head 1 includes a reflection film 5, an interlayer insulating film 6, an anode 3 as a first electrode, a light emitting unit 4, and a cathode 8 as a second electrode on an element substrate 2. The light emitting unit 4 includes a functional layer 7 laminated on the anode 3 and a partition wall B that insulates pixels and defines a boundary portion of the pixels.

The functional layer 7 includes one or more layers including at least a light emitting layer. As the light emitting layer, a known light emitting material capable of emitting fluorescence or phosphorescence is used. Specifically, (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinylcarbazole (PVK), polythiophene derivative, polymethyl Polysilanes such as phenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as. Alternatively, a low molecular material such as carbazole (CBP) can be doped with these low molecular dyes to form a light emitting layer. Tris-8-quinolinolato aluminum complex (Alq ₃ ) can also be added as an electron transporting layer as part of the light emitting layer.

  The functional layer 7 includes a light emitting material capable of emitting red light, and is configured to emit red light. The functional layer 7 is formed so as to cover the entire effective pixel region where a plurality of light emitting pixels are arranged, and is a layer common to each light emitting pixel. A layer other than the light emitting layer may be formed in the functional layer 7. For example, a hole injection layer that is disposed between the anode 3 and the light emitting layer and injects / transports holes supplied from the anode 3 to the light emitting layer may be formed. Further, an electron injection layer that is disposed between the cathode 8 and the light emitting layer and injects / transports electrons supplied from the cathode 8 to the light emitting layer may be formed.

  As the partition wall B, an inorganic insulating material such as silicon oxide or an organic insulating material such as an acrylic resin is used. In addition to such inorganic materials or organic materials, insulating materials made of organic / inorganic hybrid materials can also be used. The partition wall B has an opening H on the anode 3 and is formed so as to run on the peripheral edge of the anode 3. The functional layer 7 is formed inside the opening H of the partition wall B, whereby the light emitting unit 4 is formed. The functional layer 7 is sandwiched between the anode 3 and the cathode 8, and the anode 3, the functional layer 7, and the cathode 8 form an organic EL element 9 that is a light emitting element.

  The cathode 8 functions as a transflective film that transmits part of the light emitted by the light emitting unit 4 and reflects the remaining light to the reflective film 5 side. In general, a translucent conductive film such as ITO has a reflectivity of about 10% to 50% at the interface with the functional layer 7, and such a translucent conductive film is provided unless special measures are taken. The cathode 8 using the above has a function as a transflective film as described above.

  The optical distance between the reflective film 5 and the cathode 8 is designed to be the same as the wavelength of light emitted from the light emitting element 9 or an integral multiple thereof. As a result, the reflective film 5 and the cathode 8 constitute an optical resonator with respect to light desired to be extracted from the light emitting element 9. In the present embodiment, the light extracted from the light emitting element 9 is red light. Therefore, the optical distance between the reflective film 5 and the cathode 8 is designed to be the same as the red wavelength (for example, 660 nm) or an integral multiple thereof. The light emitted from the light emitting section 4 reciprocates between the reflective film 5 and the cathode 8, and only the light having the resonance wavelength corresponding to the optical distance is amplified and extracted. For this reason, light with high emission luminance and sharp spectrum can be extracted.

  The light emitted from the light emitting element 9 is light having a wavelength corresponding to the resonance wavelength of the optical resonator structure formed in the pixel, that is, the optical distance between the reflective film 5 and the cathode 8. This optical distance is obtained as the sum of the optical distances of the respective layers (interlayer insulating film 6, anode 3 and functional layer 7) disposed between the reflective film 5 and the cathode 8. The optical distance of each layer is determined by the product of its film thickness and refractive index.

  Here, one or more layers constituting the functional layer 7 are formed by a wet film forming method. That is, the functional layer forming material is dissolved or dispersed in a solvent and then applied onto the substrate 2 to form an organic film layer by a drying process and a baking process. And the functional layer 7 is formed by laminating | stacking such a layer one by one. The manufacturing conditions of these layers, particularly the viscosity of the liquid material, is set using the inspection results of the inspection process of the previously manufactured line head. For example, if the layer thickness is thin due to the previous inspection result and the peak wavelength of the emission spectrum is shifted to the short wavelength side, the viscosity of the liquid material is increased so that a predetermined film thickness can be obtained. ing.

  According to the image forming apparatus 100, since the line head 1 is manufactured using the printer head inspection method of the present invention described above, the manufacturing process is simplified and an inexpensive image forming apparatus is provided. Further, since the line head 1 has an optical resonator structure, the line head 1 has high emission luminance and a sharp spectrum. As a result, the life of the image forming apparatus 100 is improved and the power consumption can be reduced. In this case, the peak wavelength may shift due to an abnormality in the thickness of the functional layer of the light emitting element 9, but such a shift in the peak wavelength can be recognized as an abnormality in the emission luminance by the bandpass filter described above. The abnormality and the peak wavelength abnormality can be performed at the same time, and the inspection time does not increase.

It is a schematic structure figure showing one embodiment of an inspection device. It is explanatory drawing of the optical characteristic of the band pass filter applied to the inspection apparatus. It is explanatory drawing which shows the relationship between the emission spectrum of a normal pixel, and the image of a CCD camera. It is explanatory drawing which shows the relationship between the emission spectrum of an abnormal pixel, and the image of a CCD camera. 1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus. FIG. 2 is a schematic configuration diagram of one pixel of a line head provided in the image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Line head (printer head), 2 ... Base | substrate, 3 ... 1st electrode (1st electrode), 5 ... Reflective film, 7 ... Functional layer, 8 ... 2nd electrode (semi-transmissive reflective film), 9 ... Light emitting element 16 ... photosensitive drum (image carrier), 53 ... CCD camera (imaging device), 55 ... bandpass filter, 58 ... computer (image processing device), CA ... inspection device, L ... light, LA ... electrostatic latent Image, S ₁ , S ₂ , S _m , S _n ... Measurement section

Claims (7)

A printer head inspection apparatus comprising a plurality of light emitting elements arranged in one direction and forming an electrostatic latent image on an image carrier by light emitted from the plurality of light emitting elements,
A bandpass filter that transmits only light having a wavelength that matches the photosensitive characteristics of the image carrier;
An imaging device having sensitivity to light having a wavelength matching the photosensitive characteristics of the image carrier;
An image processing apparatus that processes an image of a light emitting state of the light emitting element imaged using the bandpass filter and the imaging device, and detects light emission luminance of the light emitting element within a wavelength range that the image carrier is exposed to. And a printer head inspection apparatus. A printer head inspection method comprising a plurality of light emitting elements arranged in one direction and forming an electrostatic latent image on an image carrier by light emitted from the plurality of light emitting elements,
The light emitting state of the light emitting element using a bandpass filter that transmits only light having a wavelength that matches the photosensitive characteristic of the image carrier and an imaging device that is sensitive to light having a wavelength that matches the photosensitive characteristic of the image carrier A step of imaging
Processing an image of a light emitting state of the light emitting element, and detecting light emission luminance of the light emitting element within a wavelength range in which the image carrier has sensitivity;
And a step of determining pass / fail of the light emitting element based on light emission luminance of the light emitting element.   3. The printer according to claim 2, wherein in the step of imaging the light emitting element, the plurality of light emitting elements are divided into a plurality of measurement sections, and the plurality of light emitting elements are imaged for each of the measurement sections. Head inspection method. Forming a plurality of light emitting elements on a substrate;
An inspection step of inspecting light emission luminance and light emission wavelength of the plurality of light emitting elements,
The method for manufacturing a printer head according to claim 2, wherein the inspection step is performed by the printer head inspection method according to claim 2.   The light-emitting element includes a functional layer including one or more layers including a light-emitting layer between a reflective film and a semi-transmissive reflective film, and an optical distance between the reflective film and the semi-transmissive reflective film. 5. The method of manufacturing a printer head according to claim 4, wherein only light having a corresponding resonance wavelength is amplified and extracted.   6. The step of forming the light emitting element sets a condition for forming the functional layer based on a test result of a light emitting element of another printer head that has been previously tested. A method for manufacturing a printer head.   In the step of forming the light emitting element, another printer in which one or more layers constituting the functional layer are formed by a wet film forming method, and the viscosity of the liquid material for forming the layer is first inspected. The method of manufacturing a printer head according to claim 6, wherein the setting is made based on a test result of the light emitting element of the head.

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