Exposure head and image forming apparatus

Abstract

The invention relates to an exposure head and an image forming apparatus. There is provided an exposure head including an organic light emitting element including a first electrode, a second electrode, an organic compound layer disposed between the first electrode and the second electrode, and a protective layer covering the second electrode. The organic compound layer includes a light-emitting layer, and a number of peaks in an exposure spectrum emitted from the exposure head is greater than a number of peaks in a PL spectrum of a light-emitting material included in the light-emitting layer.

Description

Technical Field

[0001] The present disclosure relates to an exposure head and an image forming apparatus. Background Art

[0002] Photosensitive drums (hereinafter also referred to as "drum-shaped electrophotographic photoreceptors" or "photoreceptors") used in image forming devices employing an electrophotographic system are widely used in copiers, fax machines, and printers. Such electrophotographic devices are image forming devices equipped with an exposure head (print head) and include multiple light-emitting elements. These light-emitting elements may be LEDs (light-emitting diodes) or organic light-emitting diodes (OLEDs). The photosensitive drum is exposed to light emitted from these multiple light-emitting elements, and an image corresponding to the latent image formed on the photosensitive drum is printed on recording paper.

[0003] Japanese Patent Laid-Open No. 2022-100479 discloses an exposure head using an organic light emitting element.

[0004] However, the exposure head described in Japanese Patent Laid-Open No. 2022-100479 has a bottom emission structure, and further improvement in efficiency is required. Summary of the Invention

[0005] The present disclosure provides an exposure head that can efficiently generate charges at a photoreceptor by exposing with an exposure head using an organic light emitting element, and an image forming apparatus.

[0006] The exposure head disclosed herein is an exposure head including an organic light emitting element, wherein

[0007] The organic light emitting element includes a first electrode, a second electrode, an organic compound layer disposed between the first electrode and the second electrode, and a protective layer covering the second electrode;

[0008] The organic compound layer includes a light emitting layer, and

[0009] The number of peaks in the exposure spectrum emitted from the exposure head is greater than the number of peaks in the PL spectrum of the light-emitting material included in the light-emitting layer.

[0010] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figures 1A to 1C is a diagram illustrating one example of the image forming apparatus of the present disclosure.

[0012] Figure 2is a diagram illustrating another example of the image forming apparatus of the present disclosure.

[0013] Figure 3 is a longitudinal cross-sectional view illustrating an example of the structure of an organic light-emitting element.

[0014] Figure 4A and Figure 4B : is a graph showing an example of the spectrum of the exposure head of the present disclosure.

[0015] Figure 5 This is a schematic diagram showing one form of a light emitting device that can be used in the exposure head of this embodiment.

[0016] Figure 6A is a schematic perspective view of a head substrate, Figure 6B is a diagram showing the arrangement of a plurality of light emitting elements provided on a head substrate, Figure 6C yes Figure 6B An enlarged view of a portion of .

[0017] Figure 7 1 is a diagram illustrating an example of a layer configuration of a photoreceptor of the present disclosure. DETAILED DESCRIPTION

[0018] The image forming apparatus of the present disclosure includes a photoreceptor (photoreceptor drum) and an exposure head (print head) for exposing the photoreceptor to light. The exposure head of the present disclosure includes an organic light emitting element (OLED: Organic Light Emitting Diode).

[0019] Figures 1A to 1C An example of the image forming apparatus of the present disclosure is shown. Figure 1A : is a schematic diagram illustrating an example of an image forming apparatus according to one embodiment of the present disclosure. Image forming apparatus 400 is an image forming apparatus of an electrophotographic system and includes a photoreceptor 27, an exposure head 28, a charging unit 30, a developing unit 31, a transfer unit 32, a conveying roller 33, and a fixing unit 35. The photoreceptor 27 is irradiated with light 29 from the exposure head 28 to form an electrostatic latent image on the surface of the photoreceptor 27. The exposure head 28 includes an organic light emitting element. The developing unit 31 includes a toner, etc. The charging unit 30 charges the photoreceptor 27. The transfer unit 32 transfers the developed image to a recording medium 34. The conveying roller 33 conveys the recording medium 34. The recording medium 34 is, for example, paper. The fixing unit 35 fixes the image formed on the recording medium 34.

[0020] Figure 1B and Figure 1CEach of the figures shows an exposure head 28, and a schematic diagram shows a state where multiple light-emitting units 36 are arranged on a long substrate. Arrow 37 indicates a direction parallel to the axis of the photoreceptor and represents the row direction in which the organic light-emitting elements are arranged. This row direction is the same as the direction of the axis about which the photoreceptor 27 rotates. This direction can be referred to as the long axis direction of the photoreceptor 27.

[0021] Figure 1B The embodiment in which the light emitting sections 36 are arranged along the longitudinal direction of the photoreceptor 27 is shown. Figure 1C Shown with Figure 1B A different method is to alternately arrange the light emitting sections 36 in the first and second columns in the column direction. The first and second columns are arranged at different positions in the row direction. In the first column, the plurality of light emitting sections 36 are arranged at intervals.

[0022] The second column includes light emitting sections 36 at positions corresponding to the intervals between the light emitting sections 36 in the first column. That is, the plurality of light emitting sections 36 are also arranged at intervals in the row direction. Figure 1C The configuration may also be expressed as, for example, a lattice configuration, a zigzag configuration, or a staggered lattice pattern configuration.

[0023] Figure 2 Another example of the image forming apparatus of the present disclosure is shown. Figure 2 The image forming apparatus is an electrophotographic system image forming apparatus and is composed of a scanner section 100, an image forming section 103, a fixing section 104, a feeding / transporting section 105, and a printer controller (not shown) for controlling them.

[0024] In the scanner unit 100, an original document placed on a document tray is illuminated to optically read the original document image, and the image is converted into an electrical signal to generate image data. In the image forming unit 103, the photosensitive drum 102 is driven to rotate, and the charging unit 107 charges the photosensitive drum 102. The exposure head 106 (in the figure, 106a, 106b, 106c, and 106d represent the configuration of four exposure heads corresponding to four-color full-color) emits light according to the image data, and the light emitted from the chip surface of the set light-emitting element group is focused on the photosensitive drum 102 through the rod lens array to form an electrostatic latent image. The developing unit 108 develops the electrostatic latent image formed on the photosensitive drum 102 with colorant. The developed colorant image is transferred to the paper transported on the transfer belt 111. Image forming section 103 includes four sets of image forming units for performing a series of electrophotographic processes (charging, exposure, development, and transfer). Each unit forms a full-color image with cyan (C), magenta (M), yellow (Y), and black (K) arranged in sequence. The four sets of image forming units sequentially perform image formation operations for magenta, yellow, and black after a predetermined time has passed since image formation began at the cyan station. In feed / conveying section 105, paper is fed from a predetermined paper feed unit, including internal paper feed units 109a and 109b, external paper feed unit 109c, and manual paper feed unit 109d, and is conveyed to resist rollers 110. Resist rollers 110 convey the paper on a transfer belt 111 at the time the toner image formed on image forming section 103 is transferred to the paper. An optical sensor 113 is positioned opposite transfer belt 111 and detects the position of a test pattern printed on transfer belt 111 to determine the amount of color deviation between each station. The amount of color deviation obtained here is communicated to an image controller (not shown) to correct the image position of each color. This control allows a full-color toner image to be transferred to paper without causing color deviation. The fixing unit 104 is composed of a combination of rollers and includes a built-in heat source such as a halogen heater. Using heat and pressure, it dissolves and fixes the toner on the paper to which the toner image has been transferred from the transfer belt 111. The paper is then discharged to the outside of the image forming apparatus by paper discharge rollers 112.

[0025] The printer controller (not shown) communicates with the MFP controller (not shown) for controlling the entire MFP to perform control according to instructions of the controller and issues instructions so as to maintain overall harmony and ensure smooth operation while controlling the conditions of each of the scanner section 100, the image forming section 103, the fixing section 104 and the feeding / conveying section 105.

[0026] Exposure head

[0027] An example of an exposure head configuration suitable for an image forming apparatus according to this embodiment will be described. The image forming apparatus includes a photoreceptor and an exposure head as part of its configuration. The photoreceptor and the exposure head are arranged facing each other. The exposure head is composed of a plurality of organic light-emitting elements and a lens array. The exposure head may include multiple light-emitting element arrays, or may include a single light-emitting element array.

[0028] organic light-emitting diodes

[0029] The organic light-emitting element includes a first electrode, a second electrode, an organic compound layer disposed between the first and second electrodes, and a protective layer covering the second electrode, wherein the organic compound layer includes a light-emitting layer. The organic compound layer may further include a first organic compound layer disposed between the first electrode and the light-emitting layer, and a second organic compound layer disposed between the light-emitting layer and the second electrode. In this case, the first electrode is a reflective electrode, the second electrode is a light extraction electrode, and the thickness of the first organic compound layer may be smaller than that of the second organic compound layer.

[0030] Figure 3 is a longitudinal cross-sectional view illustrating an example of the structure of an organic light-emitting element. Figure 3 The light-emitting element includes an anode (reflective electrode) 2, a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, a first electron transport layer 6, a second electron transport layer 7, an electron injection layer 8, and a cathode (light extraction electrode) 9 in the stacking direction on an opaque, light-proof substrate 1. In addition, the light-emitting element includes a first protective layer 10, a second protective layer 11, and a third protective layer 12 as a sealing film, and in some cases includes a microlens (not shown). Applying a voltage between the two electrodes causes holes to be injected from the anode 2 side and electrons to be injected from the cathode 9 side. The injected holes and electrons recombine in the light-emitting layer 5 to form an excited state, and emit light when they return to the ground state. The emitted light is reflected by the reflective electrode 2 and output from the light extraction electrode 9 side.

[0031] exist Figure 3 In the example of , the anode (reflective electrode) 2 is the first electrode; the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the first electron transport layer 6, the second electron transport layer 7, and the electron injection layer 8 are organic compound layers; and the cathode (light extraction electrode) 9 is the second electrode. The hole injection layer 3 and the hole transport layer 4 are the first organic compound layers; and the first electron transport layer 6, the second electron transport layer 7, and the electron injection layer 8 are the second organic compound layers.

[0032] In the present disclosure, the exposure spectrum emitted from the exposure head is a spectrum with multiple peaks, and can be a spectrum with multiple peaks over a wide wavelength range with slightly stronger light. The present inventors conducted research and inferred the following. Specifically, it is inferred that a light emission spectrum with multiple peaks effectively excites the photosensitive layer of the photoreceptor and is excellent in a series of mechanisms for quickly transferring charge to the charge transport material, and is therefore one of the factors that can reduce residual charge without reducing image quality. In particular, a spectrum with multiple peaks over a wide wavelength range has a wide range in terms of light energy, so it can be irradiated as excitation light with a variety of excitation energies. Therefore, it is inferred that since the excitation of the photosensitive material present in the photosensitive layer causes charge separation in various energy states, charge transfer becomes easier, resulting in a reduction in residual charge. In contrast, with strong excitation light of a single wavelength, it is inferred that since charge separation occurs in the same energy state, it is likely that excess charge that is difficult to transfer will be generated and become residual charge.

[0033] The present inventors have found that in order to realize light with multiple peaks, especially strong light with multiple peaks in a wide wavelength range, Figure 3 The organic light-emitting element with a top-emitting element structure that can be used for light interference shown is effective when a non-transparent substrate is used. In such a structure, the luminescence spectrum inherent to the light-emitting material can be extracted as a spectrum with multiple peaks in a wider wavelength band. Specifically, the film thickness between the light-emitting layer 5 and the reflective electrode 2, the film thickness between the light-emitting layer 5 and the light extraction electrode 9, and the total organic film thickness can be interference thicknesses that enhance the emission wavelength. In order to further improve the effect, the film thickness of the first protective layer 10, the film thickness of the second protective layer 11, and the film thickness of the third protective layer 12, as well as the light reflectivity of the second protective layer 11, can be optimized separately. This optimization of the film thickness and reflectivity of the protective layer allows the generation of a short-period light interference structure, and the luminescence spectrum inherent to the light-emitting material can be extracted as a spectrum with multiple peaks.

[0034] In an organic light-emitting element, the anode 2 and cathode 9 can form an optical resonator structure. For example, the optical resonator structure can be formed between the electrodes so that the optical distance enhances the light emitted from the light-emitting layer. In one example of this structure, the distance from the light-emitting layer to the reflective layer on the substrate side is an odd multiple of λ / 4, where λ is the wavelength of the light emitted from the light-emitting layer.

[0035] If manufacturing errors and the like are acceptable, the optical distance L1 may satisfy the following formula 1. The optical distance L1 may be the distance from the light-emitting layer to the reflective layer on the substrate side, the distance from the light-emitting layer to the reflective layer on the light extraction side, or the distance from the reflective layer on the substrate side to the reflective layer on the light extraction side.

[0036] 0.7(-Φ1 / (2π)+m1)×λ≤2×L1≤1.2(-Φ1 / (2π)+m1)×λ Equation 1.

[0037] In Formula 1, λ is the wavelength of light emitted from the light emitting layer, Φ1 is the phase shift on the reflection surface, and m1 is an integer. When there are two reflection surfaces, Φ1 is the sum of the phase shifts.

[0038] The cathode 9 may be a semi-transmissive reflective layer having a property of transmitting a portion of the light reaching the surface and reflecting the rest of the light (i.e., semi-transmissive reflectivity). The semi-transmissive reflective electrode is formed, for example, of simple metals such as magnesium and silver, alloys mainly composed of magnesium or silver, or alloy materials containing alkali metals or alkaline earth metals. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, and zinc-silver can be used. These electrode materials can be used alone or in combination of two or more. The cathode 9 may have a single-layer structure or a multi-layer structure. In particular, silver can be used, and in order to reduce the aggregation of silver, a silver alloy can be used. The ratio of the alloy is not important as long as the aggregation of silver can be reduced. For example, the ratio of silver: other metal can be, for example, 1:1 or 3:1. The other metal can be magnesium.

[0039] To obtain an optimal spectral shape, the thickness of the first protective layer 10 is preferably 100 nm to 3000 nm, more preferably 500 nm to 2000 nm, the thickness of the second protective layer 11 is preferably 10 nm to 500 nm, more preferably 50 nm to 300 nm, and the thickness of the third protective layer 12 is preferably 100 nm to 2000 nm, more preferably 200 nm to 1000 nm. The protective layer is not limited to a three-layer structure and may have a multilayer structure with four or more layers. In a multilayer structure, the interference period is easily optimized. The protective layer may include silicon nitride and may include a layer including aluminum oxide on a layer including silicon nitride.

[0040] In order to effectively illuminate the photoreceptor with the high-brightness luminescence spectrum emitted from the luminescent layer 5, it is necessary to reduce absorption losses occurring along the optical path from the luminescent layer 5 to the photoreceptor surface. First, it is desirable that the light is not absorbed by carrier transport layers other than the luminescent layer 5. In particular, since the luminescent spectrum passes through the hole transport layer 4 between the reflective electrode (anode) 2 and the luminescent layer 5 at least twice, absorption is not required. Second, it is desirable that the light is not absorbed by the protective layer and microlenses present on the light extraction electrode 9. Third, it is also desirable that the light is not absorbed by the lens array provided between the organic light-emitting element and the photoreceptor.

[0041] Exposure head spectrum

[0042] The photoreceptor is composed of various functional layers. In particular, the layer that plays a role in forming a charge separation state by exposure to light is the charge generation layer. In the charge generation layer, the charge generating material is an important material that plays a role in photoelectron conversion. Examples of charge generating materials include azo pigments, perylene pigments, anthraquinone derivatives, anthraquinone derivatives, dibenzopyrenequinone derivatives, pyranthrone derivatives, quinone pigments, indigo pigments, phthalocyanine pigments, and pyrenone pigments. Among them, the charge generating material can be a phthalocyanine pigment. The phthalocyanine pigment can be oxytitanium phthalocyanine, chlorogallium phthalocyanine, or hydroxygallium phthalocyanine.

[0043] Recently, an organic light-emitting element has been proposed as an exposure light source for a photoreceptor. A common organic light-emitting element is a bottom-emission organic light-emitting element, and its manufacturing process is considered to be relatively simple. In this case, the luminescence spectrum is extracted from the transparent substrate side where the pixel circuit for driving is present, which leads to the risk of reduced light utilization efficiency. In addition, since it is difficult for a bottom-emission organic light-emitting element to have an interference thickness structure that enhances luminescence, the exposure efficiency as an exposure light source may not be very high. As described above, one method for solving this problem is an organic light-emitting element that emits strong light with a wide wavelength range. The organic light-emitting element may be a top-emission organic light-emitting element that can use interference of light. If the light is within a wide wavelength range, the light energy has a certain range. In this case, it is believed that the specific excitation energy will not be concentrated in the charge generating material that absorbs the light, which leads to a reduction in excess charge. It is believed that not only a certain conductive path but also various conductive paths appear, which effectively separates the charge.

[0044] Figure 4A and Figure 4B : is a diagram showing an example of the spectrum of the exposure head of the present disclosure. Figure 4A and Figure 4B 40 represents the PL spectrum of the light-emitting material included in the light-emitting layer, 41 represents the exposure spectrum emitted from the exposure head, 42 represents the light absorption spectrum of the photoreceptor, 43 represents the light absorption spectrum of the first organic compound layer, and 44 represents the light absorption spectrum of the second organic compound layer.

[0045] like Figure 4A As shown, the number of peaks in the exposure spectrum 41 is greater than the number of peaks in the PL spectrum 40 of the luminescent material. Figure 4A In FIG, the PL spectrum 40 of the light-emitting material has two peaks, and the exposure spectrum 41 has five or more peaks.

[0046] like Figure 4A As shown, all peaks of exposure spectrum 41 may overlap with the light absorption spectrum 42 of the photoreceptor. When the multiple peaks of exposure spectrum 41 overlap less with the light absorption spectrum 42 of the photoreceptor, the charge separation efficiency decreases, and a higher intensity of light may be required. As a result, the electrical load on the organic light-emitting element may increase.

[0047] like Figure 4A and Figure 4B As shown, the longest peak wavelength in the light absorption spectrum 44 of the second organic compound layer can be farther away from the maximum emission peak wavelength of the PL spectrum 40 of the light emitting material than the longest peak wavelength in the light absorption spectrum 43 of the first organic compound layer.

[0048] like Figure 4A and Figure 4B As shown, the maximum emission peak wavelength in the PL spectrum 40 of the light-emitting material can be closer to the maximum absorption peak wavelength in the visible light region in the light absorption spectrum 42 of the photoreceptor than the longest peak wavelength in the light absorption spectrum 43 of the first organic compound layer or the longest peak wavelength in the light absorption spectrum 44 of the second organic compound layer. Figure 4B As shown, the maximum luminescence peak wavelength of the exposure spectrum 41 can be closer to the maximum absorption peak wavelength in the visible light region in the light absorption spectrum of the photoreceptor than the longest peak wavelength in the light absorption spectrum 43 of the first organic compound layer or the longest peak wavelength in the light absorption spectrum 44 of the second organic compound layer.

[0049] Furthermore, it is desirable to have as little overlap as possible between the exposure spectrum 41 and the absorption spectrum of the protective layer. When the overlap with the absorption spectrum of the protective layer is large, the exposure spectrum 41 is greatly affected by the interference of light generated in the protective layer, which may significantly reduce the spectral intensity.

[0050] Similarly, it is desirable to have as little overlap as possible between the exposure spectrum 41 and the absorption spectrum of each layer constituting the organic compound layer.

[0051] Layer structure of organic light-emitting element

[0052] Specifically, examples of the element structure of the organic light-emitting element of the present embodiment include a multilayer type element structure in which any electrode layer and an organic compound layer shown below (1) to (6) are sequentially stacked on a substrate.

[0053] In each element configuration, the organic compound layer always includes a light-emitting layer containing a light-emitting material.

[0054] (1) anode / luminescent layer / cathode;

[0055] (2) anode / hole transport layer / luminescent layer / electron transport layer / cathode;

[0056] (3) anode / hole transport layer / luminescent layer / electron transport layer / electron injection layer / cathode;

[0057] (4) anode / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / cathode;

[0058] (5) anode / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / cathode; and

[0059] (6) Anode / hole transport layer / electron blocking layer / light-emitting layer / hole blocking layer / electron transport layer / cathode.

[0060] However, these examples of element configurations are only very basic element configurations and are not limited thereto. For example, various layer configurations may be employed, such as providing an insulating layer, a binder layer, or an interference layer at the interface between the electrode and the organic compound layer, configuring the electron transport layer or the hole transport layer to consist of two layers having different ionization potentials, or configuring the light-emitting layer to consist of two layers of different light-emitting materials.

[0061] Compounds for organic light-emitting devices

[0062] In the organic light-emitting element according to this embodiment, conventionally known low-molecular-weight and high-molecular-weight hole-injection compounds or hole-transport compounds, compounds serving as hosts, light-emitting compounds, and electron-injection compounds or electron-transport compounds may be used as needed. Examples of these compounds are described below.

[0063] The hole injection or transport material can be a material with high hole mobility, so that it is easy to inject holes from the anode, and the injected holes can be transported to the light-emitting layer. In addition, in order to reduce the degradation of film quality such as crystallization in the organic light-emitting element, a material with a high glass transition temperature can be used. Examples of low-molecular and high-molecular materials with hole injection or transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly (vinylcarbazole), poly (thiophene) and other conductive polymers. In addition, the above-mentioned hole injection or transport materials can also be appropriately used in the electron blocking layer. Examples of compounds used as hole injection or transport materials are shown below, but are not limited to this.

[0064]

[0065] Examples of luminescent materials primarily related to luminescent functions include fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, and rubrene), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organic aluminum complexes such as tris(8-hydroxyquinoline)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylene vinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives. Examples of compounds used as luminescent materials are shown below, but are not limited thereto.

[0066]

[0067]

[0068] Examples of the host or auxiliary agent included in the light-emitting layer include, but are not limited to, aromatic hydrocarbon compounds and their derivatives, carbazole derivatives, azine derivatives, xanthone derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organic aluminum complexes such as tris(8-hydroxyquinoline)aluminum, and organic beryllium complexes. Specific examples are shown below.

[0069]

[0070] The electron transport material can be arbitrarily selected from materials capable of transporting electrons injected from the cathode to the light-emitting layer, and is selected in consideration of the balance with the hole mobility of the hole transport material, etc. Examples of materials having electron transport properties include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organoaluminum complexes, and fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, In addition, the above-mentioned electron transporting materials are also suitable for use in the hole blocking layer.

[0071] Examples of compounds used as electron transport materials are shown below, but are of course not limited thereto.

[0072]

[0073] The electron injection material can be arbitrarily selected from materials that can easily inject electrons from the cathode, and is selected in consideration of the balance with hole injection performance, etc. As organic compounds, n-type dopants and reductive dopants are also included, and examples thereof include alkali metal compounds such as lithium fluoride, lithium complexes such as lithium hydroxyquinoline, benzimidazolidene derivatives, imidazolidene derivatives, fulvalene derivatives, and acridine derivatives. The electron injection material can also be used in combination with the above-mentioned electron transport material.

[0074] Structure of organic light-emitting elements

[0075] An organic light-emitting element is provided by forming a first electrode, an organic compound layer, and a second electrode on a substrate. An insulating layer may be provided on the substrate. A protective layer, a color filter, a microlens, and the like may be provided on the second electrode. When a color filter is provided, a planarization layer may be provided between the color filter and the protective layer. The planarization layer may be made of, for example, an acrylic resin. The same applies when the planarization layer is provided between the color filter and the microlens. One of the first electrode and the second electrode may be an anode, and the other may be a cathode.

[0076] substrate

[0077] Examples of substrates include quartz, glass, silicon wafers, resins, and metals. Switching elements such as transistors and wiring may also be provided on the substrate, and an insulating layer may be provided thereon. The insulating layer may be made of any material in which contact holes can be formed so that wiring can be formed between the insulating layer and the first electrode and which can ensure insulation from unconnected wiring. For example, resins such as polyimide, silicon oxide, or silicon nitride may be used.

[0078] electrode

[0079] As the electrodes, a pair of electrodes may be used, and the pair of electrodes may be an anode and a cathode.

[0080] When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode at a higher potential is the anode, and the other is the cathode. It can also be said that the electrode that supplies holes to the light-emitting layer is the anode, and the electrode that supplies electrons is the cathode.

[0081] The material constituting the anode should have a work function as large as possible. For example, simple metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, and tungsten, mixtures thereof, or alloys formed by combining these metals, or metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide can be used. In addition, conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used.

[0082] These electrode materials may be used alone or in combination of two or more thereof. The anode may be composed of one layer, or may be composed of multiple layers.

[0083] When the electrode is used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, alloys thereof, or laminates thereof can be used. These materials can also function as a reflective film without functioning as an electrode. When the electrode is used as a transparent electrode, for example, a transparent conductive layer of an oxide such as indium tin oxide (ITO) or indium zinc oxide can be used, but is not limited thereto.

[0084] The electrodes can be formed by photolithography.

[0085] The material constituting the cathode may have a small work function, and examples thereof include alkali metals such as lithium, alkaline earth metals such as calcium, simple metals such as aluminum, titanium, manganese, silver, lead and chromium, and mixtures thereof. Alloys formed by combining these simple metals may also be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper and zinc-silver may be used. Metal oxides such as indium tin oxide (ITO) may also be used. These electrode materials may be used alone or in combination of two or more thereof. The cathode may have a single-layer structure, or may have a multilayer structure. In particular, silver may be used, and in order to reduce the aggregation of silver, a silver alloy may be used. The ratio of the alloy is not important as long as the aggregation of silver can be reduced. For example, the ratio of silver to other metals may be, for example, 1:1 or 3:1.

[0086] The cathode may be a top emission type element using a conductive layer of an oxide such as ITO, or may be a bottom emission type element using a reflective electrode such as aluminum (Al), and there are no particular limitations. Although there are no particular limitations on the method for forming the cathode, DC or AC sputtering can be used because it provides good film coverage and easily reduces resistance.

[0087] Organic compound layer

[0088] The organic compound layer may be formed of a single layer or may be formed of multiple layers. When the organic compound layer includes multiple layers, these layers may be referred to as a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, or an electron injection layer, depending on their function. The organic compound layer is mainly composed of an organic compound and may include inorganic atoms and inorganic compounds. For example, it may include copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, or zinc. The organic compound layer may be disposed between the first electrode and the second electrode, or may be arranged to contact the first electrode and the second electrode.

[0089] The organic compound layers (eg, hole injection layer, hole transport layer, electron blocking layer, light emitting layer, hole blocking layer, electron transport layer, and electron injection layer) constituting the organic light emitting element according to one embodiment of the present disclosure are formed by the following method.

[0090] The organic compound layer constituting the organic light-emitting element according to one embodiment of the present disclosure can be formed using a dry method such as a vacuum deposition method, an ionization deposition method, a sputtering method, or a plasma method. Instead of a dry method, a wet method in which a layer is dissolved in an appropriate solvent and formed by a known coating method (such as spin coating, casting, micro-gravure coating, gravure coating, rod coating, roller coating, wire rod coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, inkjet printing, capillary coating, nozzle coating, or LB method) can also be used. In particular, vacuum deposition, ionization deposition, inkjet printing, and nozzle coating are suitable for manufacturing large-area organic light-emitting elements.

[0091] Here, when the layer is formed by vacuum deposition or solution coating, crystallization is less likely to occur and the stability over time is excellent. When the film is formed by coating, it can also be formed in combination with an appropriate binder resin.

[0092] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, and urea resin.

[0093] These binder resins may be used alone as a homopolymer or a copolymer, or as a mixture of two or more thereof. In addition, known additives such as a plasticizer, an oxidation inhibitor, and an ultraviolet absorber may be used in combination as needed.

[0094] The thickness of each layer in the organic light-emitting element is generally 1 nm to 10 μm. In particular, the thickness of the light-emitting layer of the organic compound layer can be 10 nm to 100 nm to obtain efficient light-emitting characteristics.

[0095] Charge generation layer

[0096] When an n / p junction is formed by a p layer and an n layer or using a p-doped layer and an n-doped layer, a charge generation layer is formed. For example, when the layer is formed only by a p / n junction, an electron injection layer can be provided so that electrons extracted from the p layer are further injected into the electron transport layer. The charge generation layer can be an n-doped layer / p-doped layer. The present disclosure is not limited to any combination as the charge generation layer.

[0097] The p-doped layer can include, for example, a mixture of highly electron-attracting HAT-CN or a Lewis acid (such as molybdenum trioxide) and an aromatic amine compound. HAT-CN and molybdenum trioxide are n-type materials, meaning they can extract electrons to form a stacked structure. The p-doped layer or the np junction formed by the stack of n-type and p-type materials is processed into a p-charge generation layer.

[0098] The n-doped layer can be, for example, a layer having a low work function that facilitates electron doping, such as an alkali metal or alkaline earth metal. In the present disclosure, the n-doped layer is treated as an n-charge generation layer. Alternatively, the electron injection layer can be formed by combining LiF or the like with a reducing metal thin film, and an n-type layer / p-type layer can be formed to generate charge.

[0099] As n-dopants, for example, alkali metals such as Li, Na, K, Rb and Cs, alkaline earth metals such as Mg, Ca, Sr and Ba, rare earth metals such as Yb, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides and carbonates) and rare earth metal compounds (including oxides, halides and carbonates)) can be used.

[0100] protective layer

[0101] A protective layer can be provided on the second electrode. For example, by attaching a glass provided with a desiccant to the second electrode to reduce the infiltration of water and the like into the organic compound layer, the occurrence of display defects can be reduced. In another embodiment, the infiltration of water and the like into the organic compound layer can be reduced by providing a passivation film of silicon nitride and the like on the second electrode. For example, a second electrode is formed, and then the second electrode is transported to another chamber without breaking the vacuum, and a silicon nitride film with a thickness of 2 μm can be formed as a protective layer by a CVD method. After the film is formed by the CVD method, an atomic layer deposition method (ALD method) can be used to provide a protective layer. The material of the film formed by the ALD method is not limited, but can be silicon nitride, silicon oxide or aluminum oxide and the like. Silicon nitride can also be formed by a CVD method on a film formed by the ALD method. The film thickness of the film formed by the ALD method can be less than the film thickness of the film formed by the CVD method. Specifically, it can be less than 50% or less than 10%.

[0102] Color Filters

[0103] The color filter can be placed on the protective layer. For example, depending on the size of the organic light-emitting element, the color filter can be placed on a separate substrate and attached to the substrate on which the organic light-emitting element is placed. The color filter can be patterned on the protective layer using photographic techniques. The color filter can be made of a polymer.

[0104] planarization layer

[0105] A planarization layer can be provided between the color filter and the protective layer. The planarization layer is provided to reduce the unevenness of the underlying layer. The material of the planarization layer can be referred to as a resin layer, regardless of its purpose. The planarization layer can be composed of an organic compound that can be either low-molecular-weight or high-molecular-weight, and can be a high-molecular-weight organic compound.

[0106] The planarization layer may be provided above and below the color filter, and the materials constituting them may be the same or different. Specifically, examples thereof include polyvinyl carbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenolic resin, epoxy resin, silicone resin, and urea-formaldehyde resin.

[0107] microlenses

[0108] The organic light-emitting element may include an optical component, such as a microlens, on its light-emitting side. The microlens may be made of an acrylic resin, an epoxy resin, or the like. The purpose of the microlens may be to increase the amount of light extracted from the organic light-emitting element and to control the direction of the extracted light. The microlens may have a hemispherical shape. When the microlens has a hemispherical shape, among the tangents in contact with the hemisphere, there is a tangent parallel to the insulating layer, and the contact point between the tangent and the hemisphere is the vertex of the microlens. The vertex of the microlens can be similarly determined in any cross-sectional view. That is, among the tangents in contact with the semicircle of the microlens in the cross-sectional view, there is a tangent parallel to the insulating layer, and the contact point of the tangent with the semicircle is the vertex of the microlens.

[0109] The midpoint of a microlens can also be defined. In a cross-section of a microlens, a line segment is drawn from a point where an arc ends to a point where another arc ends, and the midpoint of this line segment can be referred to as the midpoint of the microlens. The cross-section that distinguishes the vertex and the midpoint can be a cross-section perpendicular to the insulating layer.

[0110] Opposite substrate

[0111] The counter substrate may be disposed on the planarization layer. The counter substrate is so-called because it is disposed at a position corresponding to the aforementioned substrate. The counter substrate may be made of the same material as the aforementioned substrate. When the aforementioned substrate is defined as the first substrate, the counter substrate may be the second substrate.

[0112] Specific examples of exposure heads

[0113] Figure 5 This is a schematic diagram illustrating one embodiment of a light-emitting device that can be used in the exposure head of this embodiment. The light-emitting device of this embodiment can be used as a light source in an image forming apparatus. The light-emitting device of this embodiment has a rectangular shape having long sides parallel to a first direction and short sides intersecting the first direction. For example, the first direction can be along the rotational axis of a photoreceptor in the image forming apparatus.

[0114] Substrate 1701 has a polygonal shape, and rectangular substrate 1701 will be described here as an example. In this specification, the long side direction of rectangular substrate 1701 is referred to as the first direction, and the short side direction perpendicular to the long side direction is referred to as the second direction. Polygonal shapes in this specification include shapes with rounded corners. A moisture-resistant ring 1700 is arranged on rectangular substrate 1701. This moisture-resistant ring 1700 serves to reduce and prevent water from entering the interior of the light-emitting device. Moisture-resistant ring 1700 can be, for example, a protective ring composed of a wiring layer.

[0115] Light-emitting region 1702, contact region 1703, pads 1704, and circuit 1706 are disposed within moisture-proof ring 1700. In this embodiment, contact region 1703 includes a first contact region 1703_1, a second contact region 1703_2, a third contact region 1703_3, a fourth contact region 1703_4, and a fifth contact region 1703_5. Pads 1704 include a first pad 1704_1, a second pad 1704_2, and a third pad 1704_3.

[0116] Circuit 1706 is a circuit that is part of a circuit for driving light-emitting devices, and includes circuit 1706_1 and circuit 1706_2. Examples of circuits 1706_1 and 1706_2 include, but are not limited to, input protection circuits, input circuits for inputting data for each driver, and logic circuits for processing data.

[0117] In the light-emitting region 1702, the light-emitting elements EL are arranged in a matrix. The contact region 1703 is a region where wiring electrically connected to the common electrode of the light-emitting elements EL is arranged. The pad 1704_1 electrically connects the contact region 1703 to an external element.

[0118] The outer peripheral shape of the moisture-proof ring 1700 may include a plurality of recessed portions (recesses 1705 ), which can be used as abutment areas against ribs that are part of a deposition mask in a film formation step, for example.

[0119] As described above, each of the plurality of light-emitting elements EL arranged in a matrix in the light-emitting region 1702 includes a light-emitting layer and a first electrode and a second electrode sandwiching the light-emitting layer. This embodiment shows an example in which the first electrode is an independent electrode provided for each light-emitting element EL and the second electrode is a common electrode provided in common with the respective light-emitting elements EL.

[0120] For example, when the light-emitting elements EL are arranged in four rows in the light-emitting region 1702, as shown in FIG. Figure 5As shown, the initial positions of the light-emitting elements EL in the first row may be offset in the X direction (first direction) from the initial positions of the light-emitting elements EL in the second row by 1 / 4 of the size of the light-emitting elements EL in the X direction. When n rows are configured, where n is an integer greater than or equal to 2, the initial positions of the light-emitting elements EL in the first row may be offset in the X direction from the initial positions of the light-emitting elements EL in the second row by 1 / n of the size of the light-emitting elements EL in the X direction.

[0121] Such a structure is beneficial for improving resolution.

[0122] Contact region 1703 is adjacent to light-emitting region 1702 of substrate 1701 and is disposed within moisture-proof ring 1700. At least one of contact region 1703, pad 1704, and circuit 1706 may be disposed between light-emitting region 1702 and one end of a long side of substrate 1701, along with recess 1705 of moisture-proof ring 1700, and arranged in series along the long side.

[0123] Therefore, by arranging the contact region 1703, the pad 1704, the circuit 1706, etc. at the same position in the short side direction, the length of the light emitting device in the short side direction is reduced, thereby reducing the size of the light emitting device.

[0124] The light-emitting device of this exemplary embodiment includes a common electrode of the light-emitting element EL and a plurality of contact regions 1703 of power supply wiring along the long side ends of the light-emitting device. When the common electrode is composed of, for example, a transparent electrode material with relatively high resistance, the amount of voltage drop in the long side direction can be increased. Therefore, the voltage applied to each light-emitting element EL varies depending on the distance from the contact region 1703 to which the voltage is applied. Therefore, the actual brightness is different between the light-emitting elements EL to which a voltage for emitting light with the same brightness is applied, and shadows, etc. may occur. As in the present embodiment, by providing a plurality of contact regions 1703 in the long side direction, the voltage drop of the common electrode in the long side direction is reduced, and the occurrence of shadows, etc. can be reduced.

[0125] In this embodiment, we will use Figures 6A to 6C An example in which a light emitting device is used in the head substrate 1800 of the exposure head of the image forming apparatus is described. Figure 6A is a schematic perspective view of the head substrate 1800 . Figure 6B shows the configuration of a plurality of light emitting elements EL provided on the head substrate 1800, and Figure 6C yes Figure 6B An enlarged view of a portion of .

[0126] The LED chip 1803 is mounted on the head substrate 1800. As the LED chip 1803, for example, Figure 5 The light emitting device shown.

[0127] like Figure 6A As shown, an LED chip 1803 is provided on one surface of a head substrate 1800, and a long flexible flat cable (FFC) connector 1807 is provided on the other surface. Here, one surface of the head substrate 1800 is the surface (top surface, front surface) on the side where the LED chip 1803 is provided. The other surface of the head substrate 1800 is the surface opposite to the side where the LED chip 1803 is provided (bottom surface, back surface).

[0128] The FFC connector 1807 is attached to the other side (bottom, back) of the head substrate 1800 so that its length direction is along the length direction of the head substrate 1800. The long strip-shaped FFC connector 1807 is provided so that a control signal (driving signal) is input from the control circuit portion of the image forming apparatus body and the control signal is transmitted to each LED chip 1803.

[0129] The LED chip 1803 is driven (operated to emit light or turn off) by a control signal input to the head substrate 1800 .

[0130] The LED chip 1803 mounted to the head substrate 1800 will be described. Figure 6B and Figure 6C As shown, a plurality of LED chips 1803 are arranged on one surface of the head substrate 1800. For example, LED chips 1803_1 to 1803_29 (29 chips) are provided. Figure 6B In the embodiment, LED chips 1803_1, 1803_13, 1803_14, 1803_15, 1803_16, and 1803_29 are exemplified. A plurality of light emitting elements EL, for example, 516 light emitting elements EL, are provided on each of the LED chips 1803_1 to 1803_29 in the longitudinal direction thereof.

[0131] The distance k2 between the centers of adjacent light-emitting elements EL along the length of LED chip 1803 corresponds to the resolution of the image forming apparatus. For example, if the resolution of the image forming apparatus of this exemplary embodiment is defined as 1200 dpi, the light-emitting elements EL are arranged along the length of LED chips 1803_1 to 1803_29 so that the distance k2 between the centers of adjacent light-emitting elements EL is 21.16 μm. Therefore, the exposure range of the exposure head of this exemplary embodiment is approximately 314 mm.

[0132] The photosensitive layer of the photosensitive drum is formed to a width of 314 mm or more. Since the length of the long side of A4-sized recording paper and the length of the short side of A3-sized recording paper are both 297 mm, the exposure head of this embodiment has an exposure range that can form images on A4-sized recording paper and A3-sized recording paper. Figure 6BAn example is shown in which the plurality of light emitting elements EL are arranged in the long side direction, but the light emitting elements EL may be arranged in the short side direction in addition to the long side direction.

[0133] The LED chips 1803_1 to 1803_29 are arranged in a plurality of rows in the axial direction of the photosensitive drum. Specifically, the LED chips 1803_1 to 1803_29 are alternately arranged in two rows along the axial direction of the photosensitive drum. Figure 6B As shown, odd-numbered LED chips 1803_1, 1803_3, ..., 1803_29, counted from the left, are mounted in a line in the longitudinal direction on the head substrate 1800. Furthermore, even-numbered LED chips 1803_2, 1803_4, ..., 1803_28, counted from the left, are mounted in a line in the longitudinal direction on the head substrate 1800. The LED chips 1803 are arranged in this manner.

[0134] Therefore, if Figure 6C As shown, in the longitudinal direction of LED chip 1803, the distance k1 between the centers of the light-emitting elements EL and the distance k2 between the centers of the light-emitting elements EL can be equal to each other. Here, the distance k1 between the centers of the light-emitting elements EL represents the distance between the centers of the light-emitting elements EL arranged at one end of LED chip 1803_13 and the other end of LED chip 1803_14. The distance k2 between the centers of the light-emitting elements EL represents the distance k2 between the centers of adjacent light-emitting elements EL in LED chip 1803_14. That is, the distance k1 between the centers of adjacent light-emitting elements EL arranged at one end of one LED chip 1803 and the other end of another LED chip 1803 can be the same as the distance k2 between the centers of adjacent light-emitting elements EL on one LED chip 1803.

[0135] In this embodiment, the light-emitting element EL is an organic light-emitting element and is a current-driven light-emitting element. The organic light-emitting elements are arranged in a line on a TFT (thin film transistor) substrate, for example, along the main scanning direction (the axial direction of the photosensitive drum), and are electrically connected in parallel via power supply wiring arranged along the same main scanning direction.

[0136] When a light-emitting device is used in the exposure head, linear exposure is performed. Therefore, the ratio of the long side direction (first direction X) to the short side direction (second direction Y) of the shape of the light-emitting area 1702 is greater than the ratio when the light-emitting device is used in a display or the like. The shape of the substrate of the LED chip also has a larger ratio of the long side direction (first direction X) to the short side direction (second direction Y). Specifically, for example, the length of the long side of the LED chip 1803 (or the light-emitting area 1702) is more than 5 times the length of the short side of the LED chip 1803 (or the light-emitting area 1702), or can be more than 10 times. For example, the length of the long side of the LED chip 1803 (or the light-emitting area 1702) can be more than 20 times the length of the short side of the LED chip 1803 (or the light-emitting area 1702).

[0137] The length of the long side of the LED chip 1803 is determined by the length of the photosensitive drum in the axial direction, the number of LED chips arranged in the axial direction, and the arrangement of the LED chips 1803. The length of the short side of the LED chip 1803 is determined by whether the light-emitting element EL is arranged in the light-emitting region 1702 in a direction perpendicular to the axis of the photosensitive drum or by the arrangement of the pads 1704 and the contact region 1703.

[0138] In consideration of the wavelength dependency of the photosensitivity of the photosensitive drum, the organic compound layer of the light emitting element EL may be configured to have a light emitting layer that emits red light.

[0139] The LED chip 1803 may have a color filter. The LED chip with the color filter can absorb stray light from unintended directions without reducing the amount of normal light entering the photosensitive drum, thereby improving print quality.

[0140] photoreceptor

[0141] Figure 7 An example of the layer structure of the photoreceptor of the present disclosure is shown. Figure 7 In the embodiment, a base layer 122, a charge generating layer 123, a charge transporting layer 124 and a protective layer 125 are stacked on a supporting member 121. The photosensitive layer may be configured as follows. Figure 7 The photosensitive layer shown may be a stacked layer including the charge generating layer 123 and the charge transporting layer 124, or may be a single layer photosensitive layer including a charge generating material and a charge transporting material.

[0142] Examples of methods for producing the photoreceptor disclosed herein include methods in which coating solutions for the various layers described below are prepared, the desired layers are sequentially applied, and the layers are dried. Examples of methods for applying the coating solution include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these methods, dip coating can be used from the perspectives of efficiency and productivity.

[0143] The configuration of the photoreceptor of the present disclosure will now be described.

[0144] Support member 121

[0145] The photoconductor supporting member 121 may be made of a conductive material (conductive supporting member).

[0146] The support member of the present disclosure has a drum-like (cylindrical) shape. The surface of the support member may be subjected to electrochemical treatment such as anodizing, sandblasting or cutting.

[0147] The material of the support member 121 can be metal, resin, or glass. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. In particular, an aluminum support member can be used. Resin and glass can be made conductive by, for example, mixing with a conductive material or coating with a conductive material.

[0148] Ground floor 122

[0149] In the present disclosure, a base layer 122 may be provided on the support member 121. The base layer 122 is provided for the purpose of improving the adhesion of the photosensitive layer, improving the coating property, improving the charge injection from the support member 121, protecting the photosensitive layer from electrical breakdown, and reducing interference fringes caused by scattering of image exposure light. The base layer 122 may be composed of a single base layer containing the materials shown below, or may be provided by laminating two or more different base layers containing the materials shown below.

[0150] Examples of metal oxide particles include particles of indium tin oxide, tin oxide, indium oxide, titanium oxide, strontium titanate, zinc oxide, and aluminum oxide. Silica particles may also be used. Examples of metal particles include particles of gold, silver, and aluminum. From the perspective of the dispersibility of the coating liquid for the base layer and the electrical properties of the photoreceptor, the primary particle size of the metal oxide particles may be 0.1 μm or less as a number average particle size. In the present disclosure, the metal oxide particles may be a mixture of two or more different types of metal oxides, different types of surface treatments, or particles having different particle sizes or specific surface areas.

[0151] The metal oxide particles contained in the base layer 122 may be particles having a surface treated with a surface treatment agent such as a silane coupling agent to reduce black spot image defects caused by charge injection from the support member 121 to the photosensitive layer side. As a method for treating the surface of the metal oxide particles, a general method is used, and examples thereof include a dry method and a wet method.

[0152] In the dry method, while metal oxide particles are stirred in a high-speed mixing mixer such as a Henschel mixer, an alcohol aqueous solution, an organic solvent solution, or an aqueous solution containing a surface treatment agent is added thereto, and drying is performed after uniform dispersion.

[0153] In the wet method, the metal oxide particles and the surface treatment agent are stirred in a solvent or dispersed using a sand mill, for example, using glass beads, and the solvent is removed by filtration or reduced pressure distillation. After the solvent is removed, calcination at 100°C or above may be further performed.

[0154] The base layer 122 may include a resin. The base layer may be formed into a cured film by polymerizing a composition including a monomer having a polymerizable functional group.

[0155] Examples of the resin include acrylic resins, allyl resins, alkyd resins, ethyl cellulose resins, ethylene-acrylic acid copolymers, epoxy resins, casein resins, and silicone resins. Examples also include gelatin resins, phenolic resins, urethane resins, butyral resins, polyacrylate resins, polyacetal resins, polyamide-imide resins, polyamide resins, polyallyl ethers, polyimide resins, polyester resins, and polyethylene resins.

[0156] Examples also include polycarbonate resins, polystyrene resins, polysulfone resins, polyvinyl alcohol resins, polybutadiene resins, and polypropylene resins. Among these resins, urethane resins with low hygroscopicity can be used from the viewpoint of reducing potential fluctuations under high-temperature and high-humidity environments.

[0157] Examples of the polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic anhydride group, and a carbon-carbon double bond group.

[0158] The mass ratio (P / B) of the metal oxide particles (P) to the binder resin (B) in the base layer 122 may be 1.0 / 1.0 or more and 3.0 / 1.0 or less.

[0159] In order to improve electrical properties, the bottom layer 122 may further include an electron transport material, metal particles, or a conductive polymer, etc. Among them, the electron transport material can be used.

[0160] Examples of the electron transport material include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, oxadiazole compounds, diphenoquinone compounds, xanthone compounds, alizarin compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, and boron-containing compounds.

[0161] The base layer can be formed as a cured film by using an electron transport material having a polymerizable functional group as the electron transport material and copolymerizing it with a monomer having the above-mentioned polymerizable functional group.

[0162] In order to adjust the surface roughness, improve light scattering or reduce cracks, the bottom layer 122 may further contain, for example, organic resin particles or a leveling agent. As the organic resin particles, hydrophobic organic resin particles such as silicone particles and hydrophilic organic resin particles such as cross-linked polymethacrylate resin (PMMA) particles can be used.

[0163] The base layer 122 may further include additives, for example, known materials such as conductive material particles (eg, carbon black), charge transport materials, metal chelates, and organic metal compounds.

[0164] The bottom layer 122 can be formed by preparing a bottom layer coating liquid comprising the above-mentioned materials and a solvent, forming a coating film of the liquid on the supporting member 121 or the conductive layer, and drying and / or curing the film. Examples of solvents used in the bottom layer coating liquid include organic solvents such as alcohols, sulfoxides, ketones, ethers, esters, aliphatic halogenated hydrocarbons and aromatic compounds. In the present disclosure, alcohols or ketone solvents can be used. Examples of dispersion methods for preparing the bottom layer coating liquid include methods using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roller mill, a vibration mill, a grinder or a liquid collision high-speed disperser.

[0165] The thickness of the base layer 122 is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.3 μm or more. The thickness of the base layer 122 is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0166] Photosensitive layer

[0167] The photosensitive layer of a photoreceptor is mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) A laminated photosensitive layer is a photosensitive layer comprising a charge generating layer 123 containing a charge generating material and a charge transporting layer 124 containing a charge transporting material. (2) A single-layer photosensitive layer is a photosensitive layer comprising both a charge generating material and a charge transporting material.

[0168] (1) Laminated photosensitive layer

[0169] The stacked photosensitive layer includes a charge generating layer 123 and a charge transporting layer 124 .

[0170] (1-1) Charge Generation Layer 123

[0171] The charge generating layer 123 may include a charge generating material and a resin.

[0172] Examples of charge generating materials include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these pigments, azo pigments and phthalocyanine pigments can be used. As phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments can be used.

[0173] The content of the charge generating material in the charge generating layer 123 is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less, based on the total mass of the charge generating layer 123 .

[0174] Examples of the resin include polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, polyvinyl acetate resins, and polyvinyl chloride resins. Among these resins, polyvinyl butyral resin can be used.

[0175] The charge generation layer 123 may further contain additives such as an oxidation inhibitor and an ultraviolet absorber. Specifically, examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0176] The charge generation layer 123 can be formed by preparing a charge generation layer coating liquid containing the above-mentioned materials and a solvent, forming a coating film of the liquid on the base layer 122, and drying the film. Examples of the solvent used in the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

[0177] The film thickness of the charge generation layer 123 is preferably 0.1 μm or more and 1 μm or less, and more preferably 0.15 μm or more and 0.4 μm or less.

[0178] (1-2) Charge Transport Layer 124

[0179] The charge transport layer 124 may contain a charge transport material and a binder material. When the protective layer 125 described later is not provided, the charge transport layer 124 functions as a surface layer of the photoreceptor.

[0180] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these materials, triarylamine compounds can be used.

[0181] The content of the charge transport material in the charge transport layer 124 is preferably 25% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer.

[0182] As the binder material, a thermoplastic resin (hereinafter also referred to as "resin") is used. Examples of thermoplastic resins include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among these resins, polycarbonate resins or polyester resins can be used. The polyester resin can be a polyacrylate resin.

[0183] The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, more preferably 5:10 to 12:10.

[0184] The charge transport layer 124 may contain additives such as an oxidation inhibitor, an ultraviolet absorber, a plasticizer, and a leveling agent. Specifically, examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, polystyrene resin particles, polyethylene resin particles, and boron nitride particles.

[0185] The charge transport layer 124 can be formed by preparing a charge transport layer coating liquid containing the above-mentioned materials and a solvent, forming a coating film of the liquid on the charge generating layer 123, and drying the film. Examples of the solvent used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents or aromatic hydrocarbon solvents can be used.

[0186] The film thickness of the charge transport layer 124 is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

[0187] (2) Single-layer photosensitive layer

[0188] The single-layer photosensitive layer can be formed by preparing a photosensitive layer coating liquid containing a charge generating material, a charge transporting material, a resin, and a solvent, forming a coating film of the liquid on the base layer 122, and drying the film. Examples of the charge generating material, the charge transporting material, and the resin are the same as those exemplified in the above-mentioned "(1) Laminated photosensitive layer".

[0189] Protective layer 125

[0190] In the present disclosure, a protective layer 125 may be provided on the photosensitive layer. Providing the protective layer 125 can improve durability. When the protective layer 125 is provided, the protective layer 125 functions as a surface layer of the photoreceptor.

[0191] The protective layer 125 can be formed into a cured film by polymerizing a composition of a raw material containing a binder material, such as a monomer having a polymerizable functional group. Examples of reactions in this case include thermal polymerization, photopolymerization, and radiation polymerization. Examples of polymerizable functional groups of monomers having polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic anhydride groups, and groups containing carbon-carbon double bonds. Examples of groups containing carbon-carbon double bonds include acryloyl groups and methacryloyl groups. The monomer having a polymerizable functional group can be a monomer having charge transport capability. Here, the cured product of the monomer having a polymerizable functional group is the binder material of the protective layer 125.

[0192] As the monomer having a polymerizable functional group, a hole transport compound having a chain polymerizable functional group can be used. The hole transport compound having a chain polymerizable functional group can be a compound represented by the following formula (CT-1) or (CT-2):

[0193]

[0194] In formula (CT-1), Ar 11 to Ar 13 Each independently represents a substituted or unsubstituted aryl group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms or a monovalent functional group represented by any one of the following formulas (P-1) to (P-3). However, the compound represented by formula (CT-1) contains at least one monovalent functional group represented by any one of the following formulas (P-1) to (P-3).

[0195]

[0196] In formula (CT-2), Ar 21 to Ar 24 Each independently represents a substituted or unsubstituted aryl group, Ar 25 Represents a substituted or unsubstituted arylene group. The substituent that the substituted aryl group may have is an alkyl group having 1 to 6 carbon atoms or a monovalent functional group represented by any one of the following formulas (P-1) to (P-3). The substituent that the substituted arylene group may have is an alkyl group having 1 to 6 carbon atoms or a monovalent functional group represented by any one of the following formulas (P-1) to (P-3). However, the compound represented by formula (CT-2) contains at least one monovalent functional group represented by any one of the following formulas (P-1) to (P-3).

[0197]

[0198] In formula (P-1), Z 11represents a single bond or an alkylene group having 1 to 6 carbon atoms, X 11 represents a hydrogen atom or a methyl group.

[0199]

[0200] In formula (P-2), Z 21 It represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0201]

[0202] In formula (P-3), Z 31 It represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0203] The protective layer 125 may contain resin particles containing fluorine atoms. By containing the resin particles containing fluorine atoms, the wear resistance of the protective layer can be improved.

[0204] The example of the resin contained in the resin particle containing fluorine atoms comprises polytetrafluoroethylene resin, polychlorotrifluoroethylene resin, polytetrafluoroethylene propylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin and polydichloroethylene difluoride resin. Particles comprising a variety of these resins can be used. In particular, from the viewpoint of improving dispersibility, the resin particle containing fluorine atoms can be polytetrafluoroethylene (PTFE) resin.

[0205] In cross-sectional observation of the protective layer 125, from the perspective of improving dispersibility and reducing potential fluctuations, the fluorine-containing resin particles may have an average primary particle size of 150 nm or more and 300 nm or less, where the average primary particle size is the arithmetic mean of the major diameters of the primary particles measured from a secondary electron image using a scanning electron microscope. Furthermore, the fluorine-containing resin particles may have an average primary particle size of 180 nm or more and 250 nm or less.

[0206] The content of the fluorine atom-containing resin particles in the protective layer 125 is preferably 5% by mass or more and 40% by mass or less, and more preferably 25% by mass or more and 35% by mass or less, based on the total mass of the protective layer.

[0207] The protective layer 125 may contain additives such as an oxidation inhibitor, an ultraviolet absorber, a plasticizer, and a leveling agent. Specifically, examples of the additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, silicone modified resins, silicone oils, polystyrene resin particles, polyethylene resin particles, and boron nitride particles.

[0208] The protective layer 125 can be formed by preparing a protective layer coating liquid containing the above-mentioned materials and a solvent, forming a coating film of the liquid on the photosensitive layer, and drying and / or curing the film. Examples of the solvent used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.

[0209] The film thickness of the protective layer 125 is preferably 0.50 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

[0210] Surface treatment of photoreceptor

[0211] In the present disclosure, the surface of the photoreceptor can be treated. By performing the surface treatment, the behavior of the cleaning means (cleaning blade) in contact with the photoreceptor can be made more stable. Examples of surface treatment methods include a method of transferring a shape by pressing a mold having a convex portion against the surface of the photoreceptor, a method of providing a concave-convex shape by mechanical grinding, and a method of roughening the surface by causing particles to collide with the surface of the photoreceptor. Therefore, by providing concave or convex portions on the surface layer of the photoreceptor, the behavior of the cleaning means in contact with the photoreceptor can be made more stable.

[0212] The concave or convex portion may be formed on the entire surface of the photoreceptor, or may be formed on a portion of the photoreceptor surface. When the concave or convex portion is formed on a portion of the photoreceptor surface, the concave or convex portion may be formed over at least the entire area that contacts the cleaning means (cleaning blade). When forming the concave portion, the concave portion may be formed on the photoreceptor surface by pressing a mold having convex portions corresponding to the concave portion against the photoreceptor surface to transfer the shape.

[0213] Example

[0214] Example 1

[0215] organic light-emitting diodes

[0216] In this embodiment, the production Figure 3 The organic EL element shown is shown. Specifically, a top-emission stacked organic EL element is produced, in which an anode (reflective electrode) 2, a hole injection layer 3, a hole transport layer 4, a light-emitting layer 5, a first electron transport layer 6, a second electron transport layer 7, an electron injection layer 8, a cathode (light extraction electrode) 9, a first protective layer 10, a second protective layer 11, and a third protective layer 12 are sequentially formed on a substrate 1. The light-emitting layer 5 is formed of a red light-emitting material and a host material.

[0217] A 40nm thick titanium (Ti) film was sputtered onto a substrate 1 with a wiring layer stacked on a silicon substrate as an anode 2, and patterned using photolithography to form a Ti pixel array with square pixel holes and wiring. The pixel holes were 20μm on a side.

[0218] Subsequently, the vacuum deposition equipment was attached to the silicon substrate and material cleaned with UV / ozone and evacuated to 1.0×10 -4 Pa(1×10 -6 ). Subsequently, the thickness of the hole injection layer 3 and the hole transport layer 4 is adjusted to a film thickness that imparts an interference structure that increases the emission wavelength. Then, a light-emitting layer 5 containing a red light-emitting material is formed. Then, a first electron transport layer 6, a second electron transport layer 7, and an electron injection layer 8 are sequentially formed with a thickness that imparts an interference structure that increases the emission wavelength. Subsequently, a cathode 9 is formed. Further, a silicon oxide film is sequentially formed by a CVD method as a first protective layer 10, an aluminum oxide film is formed by an ALD method as a second protective layer 11, and a silicon oxide film is formed by a CVD method as a third protective layer 12. Thus, an organic light-emitting element is produced. It was confirmed that the emission spectrum of the organic light-emitting element is a strong light with multiple peaks in a wide wavelength range of 500nm to 800nm.

[0219] Exposure head and image forming device

[0220] Organic light-emitting diode (OLED) chips produced on a silicon substrate were cut and 17 chips were attached to a PCB substrate. The PCB substrate loaded with OLED chips was provided and installed in a housing with a lens array attached to produce an exposure head. Image evaluation was performed using a copier incorporating this exposure head. The results showed that the evaluation images could be stably output, and image defects were visually confirmed to be reduced. Therefore, the present disclosure was judged to be significantly effective.

[0221] like Figure 4A As shown, the PL spectrum 40 of the luminescent material of the luminescent layer shows that the exposure spectrum 41 for exposing the photosensitive drum has many peaks. In addition, all the peaks of the exposure spectrum 41 overlap with the absorption spectrum 42 of the photosensitive body.

[0222] Example 2

[0223] The exposure spectrum of the exposure head produced by the method described in Example 1, the absorption spectrum of the first organic compound layer (hole injection layer 3 and hole transport layer 4) between the anode 2 as the first electrode and the light emitting layer 5, the absorption spectrum of the second organic compound layer (first electron transport layer 6, second electron transport layer 7 and electron injection layer 8) between the cathode 9 as the second electrode and the light emitting layer 5, and the absorption spectrum of the charge generating material used in the photoreceptor as the absorption spectrum of the photoreceptor were measured respectively. Figure 4A and Figure 4BAs shown, it is confirmed that the maximum emission peak wavelength of the PL spectrum 40 of the luminescent material and the exposure spectrum 41 is closer to the maximum absorption peak wavelength of the light absorption spectrum 42 of the photoreceptor in the visible light region than the longest peak wavelength of both the absorption spectrum 43 of the first organic compound layer and the absorption spectrum 44 of the second organic compound layer.

[0224] According to the present disclosure, the photoreceptor can efficiently generate charges.

[0225] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An exposure head comprising an organic light emitting element, wherein The organic light emitting element includes a first electrode, a second electrode, an organic compound layer disposed between the first electrode and the second electrode, and a protective layer covering the second electrode. The organic compound layer includes a light emitting layer, and The number of peaks in an exposure spectrum emitted from the exposure head is greater than the number of peaks in a PL spectrum of a light-emitting material included in the light-emitting layer. 2 . The exposure head according to claim 1 , wherein the organic light emitting element has an optical resonator structure formed by the first electrode and the second electrode. The exposure head according to claim 1 , wherein the PL spectrum includes two peaks. The exposure head according to claim 3 , wherein the exposure spectrum includes five or more peaks.

5. The exposure head according to claim 1, wherein The organic compound layer further includes a first organic compound layer located between the first electrode and the light emitting layer and a second organic compound layer located between the light emitting layer and the second electrode. The first electrode is a reflective electrode, and the second electrode is a light extraction electrode, and The thickness of the first organic compound layer is smaller than the thickness of the second organic compound layer. 6 . The exposure head according to claim 5 , wherein the longest peak wavelength in the light absorption spectrum of the second organic compound layer is farther away from the maximum light emission peak wavelength of the PL spectrum than the longest peak wavelength in the light absorption spectrum of the first organic compound layer. The exposure head according to claim 1 , wherein the protective layer comprises silicon nitride. 8 . The exposure head according to claim 1 , wherein the protective layer comprises a layer comprising aluminum oxide on a layer comprising silicon nitride. 9 . The exposure head according to claim 1 , wherein the organic light emitting element has a top emission type element structure disposed on a light-impermeable substrate.

10. An image forming apparatus comprising a photoreceptor and an exposure head for exposing the photoreceptor to light, wherein The exposure head is the exposure head according to claim 1. 11 . The image forming apparatus according to claim 10 , wherein all peaks of the exposure spectrum overlap with a light absorption spectrum of the photoreceptor.

12. The image forming apparatus according to claim 10, wherein The organic compound layer further includes a first organic compound layer located between the first electrode and the light emitting layer and a second organic compound layer located between the light emitting layer and the second electrode, and The maximum emission peak wavelength of the PL spectrum is closer to the maximum absorption peak wavelength in the visible light region in the light absorption spectrum of the photoreceptor than the longest peak wavelength in the light absorption spectrum of the first organic compound layer or the longest peak wavelength in the light absorption spectrum of the second organic compound layer.

13. An image forming device according to claim 12, wherein the maximum luminescence peak wavelength of the exposure spectrum is closer to the maximum absorption peak wavelength in the visible light region in the light absorption spectrum of the photoreceptor than the longest peak wavelength in the light absorption spectrum of the first organic compound layer and the longest peak wavelength in the light absorption spectrum of the second organic compound layer.

Images