JP2006337456A - Light emitting device and checking method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide light emitting elements that have light emission areas smaller than the smallest areas measurable by an optical measurement device and to provide a suitable configuration for checking the light emission characteristics of the light emitting elements. <P>SOLUTION: The light emitting elements Er, Eg and Eb emitting R(red), G(green) and B(blue) light rays respectively are formed in lines on a substrate 1. Light emitting elements ER, EG, and EB for monitoring are formed on both longitudinal ends of the array pattern. The light emitting elements for monitoring are formed to have larger areas that are far larger than those of the light emitting elements Er, Eg, and Eb forming light emitting areas. The light emission characteristics of the respective light emitting elements Er, Eg, and Eb are measured using the light emitting elements ER, EG, and EB for monitoring, which have the larger formation areas. Thus, whether the light emitting elements Er, Eg, and Eb arrayed on one and the same substrate are within specific standard or not is checked. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting device that forms a light-emitting region by arranging a plurality of light-emitting elements on a substrate surface and uses the light-emitting elements arranged in the light-emitting region to perform exposure or image display on a photoreceptor, for example. In particular, the present invention relates to a light emitting device having a suitable structure in the case of inspecting the light emission characteristics of the light emitting element in the manufacturing process and a method for inspecting the light emission characteristics.

  For example, as an exposure method for writing a latent image on a photoconductor, an LED array method has been frequently used from the viewpoint of speeding up, downsizing, and high reliability. As an exposure device used in this LED array system, a configuration in which a large number of minute light emitting diodes are linearly arranged on a substrate is used. In this case, since it is impossible to pattern a large number of minute light emitting diodes on a single substrate at a time, it is necessary to accurately arrange the minute light emitting diodes formed in advance on the substrate. For this reason, a highly accurate mounting technique for reducing the arrangement error of each LED chip is required, and this causes problems such as an increase in manufacturing cost.

Accordingly, in the above-described exposure apparatus, examples in which an organic EL (electroluminescence) element is used as an exposure device instead of the LED are disclosed in Patent Documents 1 and 2 shown below. According to this, it is set as the structure by which the light emitting element by organic EL was linearly arranged on the substrate surface, and it is possible to pattern the said light emitting element on one board | substrate. For this reason, the difficulty in mounting when arranging a large number of LED chips as described above can be avoided, and the cost can be reduced.
JP-A-9-226171 JP-A-9-226172

  FIG. 1 shows a configuration example in which an organic EL element is employed as an exposure device used in the exposure apparatus described above. That is, organic EL elements Er, Eg, and Eb that emit light of R (red), G (green), and B (blue) are linearly arranged on the substrate 1 and are adjacent to each other. Has been placed. That is, a color light emitting element is constituted by adjacent EL elements of R, G, and B, and the color light emitting elements are arranged in a straight line.

  FIG. 2 shows an example of the laminated structure of one organic EL element described above. In this organic EL element, a transparent electrode (anode) 2 made of, for example, ITO, a light emitting functional layer 3, and a metal electrode (cathode) 4 made of aluminum alloy or the like are sequentially laminated on a transparent substrate 1 such as glass. Is made up of.

  The light emitting functional layer 3 may be a single light emitting layer 3a made of an organic compound, or a two-layer structure composed of an organic hole transport layer 3b and a light emitting layer 3a, or an organic hole transport layer 3b, a light emitting layer 3a, and an organic electron transport layer. A three-layer structure composed of 3c, a hole injection layer 3d between the transparent electrode 2 and the hole transport layer 3b, and an electron injection layer 3e between the metal electrode 4 and the electron transport layer 3c In some cases, a multilayered structure is used. The light generated in the light emitting functional layer 3 is led to the outside through the transparent electrode 2 and the transparent substrate 1 as indicated by arrows.

  By the way, in the exposure apparatus having the configuration shown in FIG. 1, in the inspection process in the manufacturing process, a measurement process for measuring the light emission characteristics of each of the EL elements Er, Eg, Eb that emit light of R, G, B is executed. Is done. As the measurement process, for example, using an optical measuring instrument such as a color measuring instrument, it is verified whether the chromaticity, luminance, color temperature, etc. of the R, G, B EL elements are within a predetermined range. The

  FIG. 3 illustrates an example in which the light emission characteristics of the element are measured by the above-described color measuring instrument. In other words, the light from the surface to be measured (light emitting surface by the EL element) 11 has an emission solid angle Ω set through the objective lens 12 and the fixed aperture 13. Then, the light passing through the fixed diaphragm 13 is made into a parallel light beam by the relay lens 14 and is incident on the photoelectric converter 16 through the visibility correction filter 15. The visibility correction filter 15 is configured to be selected by, for example, turret rotation corresponding to the measurement of the EL elements of R, G, and B colors.

  By the way, in the exposure apparatus described above, there is an increasing demand for higher resolution, and accordingly, the light emission area of the organic EL element alone as an exposure device is further miniaturized, and a configuration in which the light emission area is arranged at high density is required. It is like that. Therefore, when the area of the single light emitting element to be measured is smaller than the minimum area of the surface to be measured that can be measured by the color measuring instrument or the like shown in FIG. Becomes impossible.

  That is, the symbol A shown in FIG. 1 shows an example of the minimum area that can be measured by the optical measuring instrument. On the other hand, the light emission area of a single element divided by a square is measurable as indicated by the symbol A. The area is smaller than the minimum area. In order to deal with such a technical problem, it is conceivable to create a lighting region corresponding to the measurable area A by simultaneously lighting a plurality of elements, but as shown in FIG. In the light emitting device used in the above-described exposure apparatus having a different emission color, it is impossible to adopt the above-described means.

  The present invention has been made paying attention to the above-described problems, and in a light emitting device applied to, for example, an exposure apparatus provided with a light emitting element having a light emitting area smaller than the minimum area measurable by an optical measuring instrument, It is an object of the present invention to provide a light emitting device having a suitable configuration and a method for inspecting the light emission characteristics when inspecting the light emission characteristics.

  In a preferred embodiment of the light emitting device according to the present invention made to solve the above-described problems, a light emitting region is formed by arranging a plurality of light emitting elements, and the light emitting device is arranged in the light emitting region. A light-emitting device that performs exposure or image display on a photoreceptor using the light-emitting element, and includes at least one monitor light-emitting element that does not contribute to exposure or image display on the photoreceptor outside the light-emitting area, The light emitting area of the light emitting element for use is characterized in that it is formed larger than the light emitting area of the individual light emitting elements arranged in the light emitting region.

  The inspection method according to the present invention, which has been made to solve the above-described problem, inspects the light emission characteristics of the light emitting elements arranged in the light emitting region in the light emitting device having the above structure, as set forth in claim 9. A light emission driving step of supplying a driving current to the monitor light emitting element to drive light emission, and taking in light from the monitor light emitting element in a light emission state to obtain a light emission characteristic by an optical measuring unit. And performing a measurement process to measure.

  Hereinafter, a light emitting device and an inspection method thereof according to the present invention will be described based on embodiments shown in the drawings. In the embodiments described below, portions that perform the same functions as the constituent elements shown in the drawings described above are denoted by the same reference numerals.

  In the embodiment shown in FIG. 4, the light emitting elements Er, Eg, and Eb by organic EL that emit each color of R, G, and B are formed on the substrate 1 in a straight line and adjacent to each other. Has been. That is, a light emitting region is formed by the light emitting elements Er, Eg, Eb, and these function as an exposure device for the photosensitive member as described above.

  On the other hand, monitor light-emitting elements are also formed on the substrate 1 at both ends in the longitudinal direction of the arrangement pattern of the elements Er, Eg, and Eb that form the light-emitting regions. In the embodiment shown in FIG. 4, ER, EG, and EB are laminated on the substrate 1 as monitor light emitting elements corresponding to the respective colors R, G, and B, and these elements form a light emitting region. It has the same layer structure as Er, Eg, and Eb.

  That is, the light emitting elements ER, EG, EB for monitoring and the light emitting elements Er, Eg, Eb forming the light emitting region are composed of organic EL elements, and are simultaneously formed on the substrate 1 in the same film forming process. . Therefore, the light emitting element for monitoring and the light emitting element forming the light emitting region can have the same electrical characteristics for each color of R, G, B, and the luminance characteristics and the forward voltage with respect to the light emission driving current, respectively. It is possible to have substantially the same temperature-dependent characteristics and aging characteristics.

  In addition, the monitor light emitting elements ER, EG, and EB are configured so that their film-forming areas are much larger than the individual light emitting elements Er, Eg, and Eb that form the light emitting region. Yes. As a result, the light emitting element for monitoring has a light emitting area larger than the minimum area A measurable by the optical measuring instrument described with reference to FIG. In order to measure the optical characteristics of the light emitting elements, the light emitting elements ER, EG, and EB for monitoring and the light emitting elements Er, Eg, and Eb arranged in the light emitting region are individually controlled to emit light. It is desirable to be able to configure.

  In order to measure the optical characteristics of the light emitting element using the above-described configuration, the monitor light emitting element for each color of R, G, and B is individually supplied with a driving current to drive light emission. The light from the monitor light emitting element is taken in, and the light emission characteristics (for example, the chromaticity, luminance, color temperature, etc. described above) are set for each color of R, G, B by the light measuring means of the form shown in FIG. The step of measuring is performed. Thereby, it is possible to verify whether or not the light emission characteristics of the light emitting elements Er, Eg, and Eb arranged on the same substrate are within a predetermined standard.

  The monitor light emitting elements ER, EG, and EB can be used not only for verifying the optical characteristics of the light emitting elements as described above, but also when a predetermined constant current is supplied to each of the monitor light emitting elements. By using the forward voltage to be used, it can be used to compensate for the temperature dependence of each light emitting element Er, Eg, Eb and the luminance characteristics based on the change over time. FIG. 5 illustrates an example for realizing this.

  Reference numeral 1 denotes a substrate that constitutes the light-emitting device already described. As described above, the monitor light-emitting elements ER, EG, and EB are arranged on the substrate. In addition, n light emitting elements Er, Eg, and Eb that form the light emitting region are arranged, and for convenience of explanation, these are denoted by reference numerals 1 to n.

  On the other hand, constant current sources IR, IG, and IB for supplying constant currents to the monitor light emitting elements ER, EG, and EB, respectively, are provided, and are generated when constant currents are supplied from the constant current sources to the monitor light emitting elements. The forward voltages VfR, VfG, and VfB are configured to be supplied to the sample and hold circuits 8R, 8G, and 8B, respectively. The forward voltages VfR, VfG, and VfB held by the sample and hold circuits 8R, 8G, and 8B are respectively supplied to the DC-DC converters 9R, 9G, and 9B as control voltages. ing.

  Each of the DC-DC converters 9R, 9G, and 9B is based on the forward voltages VfR, VfG, and VfB held by the sample and hold circuits 8R, 8G, and 8B, and the light emitting elements Er1 to Ern and Eg1 to Egn. , Eb1 to Ebn function to control the value of the drive voltage supplied to them. That is, the converter 9R outputs the drive voltage VHR based on the VfR, the converter 9G outputs the drive voltage VHG based on the VfG, and similarly the converter 9B outputs the drive voltage VHB based on the VfB. Is done. Each DC-DC converter constitutes a boost converter using a battery as a primary power source.

  According to the above-described configuration, each light emitting element Er1 corresponding to R, G, B is also based on the forward voltage VfR, VfG, VfB in each monitor light emitting element ER, EG, EB corresponding to R, G, B. Since the drive voltage values VHR, VHG, and VHB supplied to Ern, Eg1 to Egn, and Eb1 to Ebn are individually controlled, each of R, G, and B can be appropriately adapted to the operating temperature and changes with time. Compensation operation can be realized.

  By the way, the light emitting device using the organic EL element having the configuration shown in FIG. 4 has a problem that the EL element itself is easily oxidized by receiving moisture in the atmosphere and deteriorates the light emission characteristics. Therefore, this type of light-emitting device employs a configuration in which the EL element is sealed with a sealing member between the substrate and the substrate.

  FIG. 6 is a cross-sectional view of the configuration, which is shown in a vertical cross-sectional view in a state where the top surface of the light-emitting device shown in FIG. 4 is sealed with a sealing member and cut at the center. . In the configuration shown in FIG. 6, the monitor light emitting elements already described are indicated as ER, G, and B, and the light emitting elements arranged in the light emitting region are indicated as Er, g, and b. In the configuration shown in FIG. 6, the monitoring light emitting elements and the light emitting elements arranged in the light emitting region are sealed between the substrate 1 and the sealing member 5 having independent sealing spaces. Yes. Reference numeral 5a indicates a partition wall that partitions the light emitting element for monitoring and the light emitting region, and reference numeral 6 schematically indicates an adhesive interposed between the sealing member 5 and the substrate 1. .

  Then, in the light emitting device configured to use the monitor light emitting element for luminance compensation based on temperature and changes with time as shown in FIG. 5, the monitoring light emitting element is used as it is in the sealed configuration shown in FIG. be able to. Further, in the case where the monitor light emitting element is used only for measuring the light emission characteristics in the manufacturing process, a part of the substrate 1 and the sealing member 5 on which the monitor light emitting element is formed is cut off after the measurement process is performed. To be made.

  The arrow shown in FIG. 6 indicates the cut-out portion, and can be used as the light-emitting device shown in FIG. 7 in which the light-emitting area is left by cutting out the arrangement region of the monitor light-emitting element from the portion indicated by the arrow. it can. According to the configuration shown in FIG. 7, the partition wall 5a formed on the sealing member 5 acts so as to perform sealing after excision of the arrangement region of the monitor light emitting element.

  In the embodiment described above, the monitor light emitting elements are formed at both ends in the longitudinal direction of the array pattern of the light emitting elements, but may be formed on only one of them. The monitor light emitting elements are formed corresponding to R, G, and B, respectively, which are configured to include at least two types according to the light emission colors of the light emitting elements arranged in the light emitting region. There is also a case. Furthermore, in the embodiment described above, the light emitting device used for the exposure apparatus is described, but the above-described configuration can also be used as a display device.

It is a top view explaining the structural example which employ | adopted the organic EL element as an exposure device used for exposure apparatus. It is sectional drawing explaining the example of the laminated structure of an organic EL element. It is a schematic diagram explaining the example which measures the light emission characteristic of a light emitting element. It is a top view which shows embodiment of the light-emitting device concerning this invention. FIG. 5 is a block diagram illustrating an example of a drive circuit using the light emitting device illustrated in FIG. 4. It is sectional drawing of the state which mounted | wore the light-emitting device shown in FIG. 4 with the sealing member. It is sectional drawing which shows the structure of the light-emitting device which excised the light emitting element part for monitoring from the structure shown in FIG.

Explanation of symbols

1 Substrate 2 Transparent electrode (anode)
3 Light emitting functional layer 4 Metal electrode (cathode)
5 Sealing member 5a Partition wall 6 Adhesive ER, EG, EB Monitor light emitting element (organic EL element)
Er, Eg, Eb Light emitting element (organic EL element)

Claims (11)

A light-emitting device that forms a light-emitting region by arranging a plurality of light-emitting elements, and performs exposure or image display on a photoconductor using the light-emitting elements arranged in the light-emitting region,
At least one monitor light emitting element that does not contribute to exposure or image display on the photoreceptor outside the light emitting area, and the light emitting area of the monitor light emitting element is larger than the light emitting area of each light emitting element arranged in the light emitting area. The light emitting device is characterized in that it is formed to be large.   The light emitting device according to claim 1, wherein the light emitting element for monitoring is configured in the same layer structure as the light emitting elements arranged in the light emitting region.   3. The light emitting device according to claim 1, wherein at least two types of the monitor light emitting elements are provided according to the light emission colors of the light emitting elements arranged in the light emitting region.   The light-emitting element for monitoring and the light-emitting elements arranged in the light-emitting region are configured to be able to individually control light emission. Light emitting device.   The voltage corresponding to the forward voltage in the light emitting elements arranged in the light emitting region can be obtained by supplying a predetermined current to the monitoring light emitting element. The light emitting device according to any one of claims 1 to 4.   6. The monitor light-emitting element and the light-emitting elements arranged in the light-emitting region are sealed by a sealing member having an independent sealing space, respectively. A light-emitting device according to claim 1.   7. The light-emitting element arranged in the light-emitting region includes elements that emit R (red), G (green), and B (blue). The light-emitting device described in item 1.   The light-emitting device according to claim 1, wherein the light-emitting element for monitoring and the light-emitting elements arranged in the light-emitting region are configured by organic EL elements. An inspection method for inspecting light emission characteristics of light emitting elements arranged in the light emitting region in the light emitting device according to any one of claims 1 to 8,
A light emission drive step of driving the light emission by supplying a drive current to the monitor light emitting element;
A measurement step of taking light from the monitor light emitting element in a light emitting state and measuring the light emission characteristics by the light measuring means;
A method for inspecting a light emitting device, comprising:   The light-emitting device inspection method according to claim 9, wherein the light emission driving step and the measurement step are individually performed for each monitor light-emitting element in the plurality of monitor light-emitting elements.   The light emission according to claim 9 or 10, further comprising a cutting step of cutting the substrate on which the light emitting element for monitoring is formed from the substrate on which the light emitting region is formed after the measurement step is completed. Device inspection method.

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