Image forming device

Abstract

To provide an image forming device with high image formation efficiency.SOLUTION: The present disclosure provides an image forming device including an organic light-emitting element having an optical resonator structure on a first surface of a substrate, and a photosensitive body that receives light from the organic light-emitting element, and the organic light-emitting element includes, in this order from the first surface, a first electrode, an organic compound layer containing an emitting material, and a second electrode, and the maximum peak wavelength in the visible light region of the emission spectrum of the organic light-emitting element resonated by the optical resonator structure is closer to the wavelength of the maximum absorption value in the visible light region of the absorption spectrum of the photosensitive body than the maximum peak wavelength in the visible light region of the PL spectrum of the emitting material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] An image forming apparatus using an electrophotographic system forms an image by exposing a photosensitive member (hereinafter also referred to as a "drum-shaped electrophotographic photosensitive member" or "photosensitive drum") to positionally controlled light. Such image forming apparatuses are widely used as printers. The image forming apparatus has an exposure unit equipped with a light-emitting unit. Known light-emitting elements in the exposure unit include light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), and vertical cavity surface-emitting lasers (VCSELs). The photosensitive member is exposed to light emitted from these light-emitting elements, and an image corresponding to the latent image formed on the photosensitive member is printed on a recording medium such as recording paper.

[0003] Patent Document 1 describes an image forming apparatus that uses an organic light-emitting element in an exposure section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-100479 Summary of the Invention [Problem to be solved by the invention]

[0005] The image forming apparatus described in Patent Document 1 includes an exposure unit having organic light-emitting elements. This exposure unit has a so-called bottom emission configuration in which light emitted from the organic light-emitting elements is emitted toward a photoconductor through a transparent substrate. For organic light-emitting elements, a technique is known for enhancing the emission intensity of a specific wavelength by using an optical resonator structure, and this technique can also be applied to the exposure unit of the image forming apparatus.

[0006] The emission of organic light-emitting devices with an optical resonator structure can have a different peak from the emission obtained from organic compounds alone, known as PL. When the maximum emission peak wavelength of the emission obtained by the optical resonator structure shifts away from the absorption spectrum of the photoconductor, the light may be less easily absorbed by the photoconductor than PL.

[0007] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that can form images with high efficiency. [Means for solving the problem]

[0008] The present invention provides an image forming device comprising: an organic light-emitting element having an optical resonator structure on a first surface of a substrate; and a photosensitive member that receives light from the organic light-emitting element, wherein the organic light-emitting element has, in this order from the first surface, a first electrode, a light-emitting layer containing a light-emitting material, and a second electrode; and the maximum peak wavelength in the visible light region of the emission spectrum of the organic light-emitting element resonated by the optical resonator structure is closer to the wavelength of the maximum absorption value in the visible light region of the absorption spectrum of the photosensitive member than to the maximum peak wavelength in the visible light region of the PL spectrum of the light-emitting material. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an image forming apparatus that can form images with high efficiency. [Brief explanation of the drawings]

[0010] [Figure 1]1(a) and 1(b) show the emission spectrum of an organic light-emitting device according to one embodiment of the present invention, the PL spectrum of a light-emitting material, and the light absorption spectrum of a photoreceptor. [Figure 2] 1(a) and 1(b) show the emission spectrum of an organic light-emitting element according to one embodiment of the present invention, the light absorption spectrum of an organic compound layer of the organic light-emitting element, and the light absorption spectrum of a photoreceptor. [Figure 3] 1(a) and 1(b) show the emission spectrum of an organic light-emitting element according to one embodiment of the present invention, the light absorption spectrum of an organic compound layer of the organic light-emitting element, and the light absorption spectrum of a photoreceptor. [Figure 4] 1 is a cross-sectional view schematically illustrating an organic light-emitting device according to one embodiment of the present invention. [Figure 5] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 6] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention. [Figure 7] FIG. 2 is a schematic diagram of an exposure unit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An image capturing device according to one embodiment of the present invention includes an organic light-emitting element having an optical resonator structure on a first surface of a substrate, and a photoreceptor for receiving light from the organic light-emitting element, the organic light-emitting element including a first electrode, a light-emitting layer including a light-emitting material, and a second electrode in this order from the first surface; The image forming apparatus is characterized in that the maximum peak wavelength in the visible light region of the emission spectrum of the organic light-emitting element resonated by the optical resonator structure is closer to the wavelength of the maximum absorption value in the visible light region of the absorption spectrum of the photoreceptor than to the maximum peak wavelength in the visible light region of the PL spectrum of the light-emitting material.

[0012] An image forming apparatus according to one embodiment of the present invention has a configuration in which the emission spectrum emitted by the light-emitting element is made closer to the wavelength of the maximum absorption value in the visible light region of the light absorption spectrum of the photosensitive material by using an optical resonator structure, rather than the PL that represents the emission of the light-emitting material itself.

[0013] The PL spectrum refers to the light emitted by photoexciting a light-emitting material. The light-emitting material can be dissolved in a solvent such as toluene. It does not have to be dissolved as long as it is doped into PMMA and is less susceptible to the influence of other compounds. The PL spectrum of a light-emitting element and the PL spectrum of a light-emitting material are used separately. The PL spectrum of a light-emitting element differs from the PL spectrum of a light-emitting material due to the influence of reflective surfaces such as electrodes and protective layers. In particular, the optical resonator structure shifts the emission wavelength peak to shorter or longer wavelengths. On the other hand, the PL spectrum is the emission spectrum of the light-emitting material itself, and therefore exhibits a unique shape for each material, and the emission peak wavelength is constant, excluding measurement errors.

[0014] In one embodiment of the present invention, the peak with the longest wavelength may be considered during energy transfer, because when energy transfer occurs according to the Förster mechanism, the amount of energy transfer is estimated as proportional to the fourth power of the wavelength.

[0015] An organic light-emitting device according to one embodiment of the present invention is a device having a first electrode, a second electrode, and an organic compound layer disposed between the first and second electrodes on a substrate, and emits light when electric charges are supplied from these electrodes. The organic compound layer may be composed of multiple layers, specifically, a hole injection layer, a hole transport layer, an emitting layer, an electron transport layer, and an electron injection layer. Each layer may be further divided into multiple layers. For example, the hole transport layer may have a first hole transport layer and a second hole transport layer. Each layer may be named differently depending on its role. For example, if the electron transport layer has the role of reducing hole leakage from the emitting layer, it may be called a hole blocking layer. In this specification, a first organic compound layer is disposed between the first electrode and the emitting layer, and a second organic compound layer is disposed between the emitting layer and the second electrode. A third organic compound layer may be disposed between the first organic compound layer and the first electrode. A fourth organic compound layer may be disposed between the second organic compound layer and the second electrode.

[0016] The organic light-emitting device according to one embodiment of the present invention may have a so-called top-emission configuration, in which the first electrode is a reflective electrode and the second electrode is a light-extraction electrode. The first electrode may be located closer to the substrate than the second electrode.

[0017] The wavelength of the maximum emission peak in the emission spectrum of the organic light-emitting element according to one embodiment of the present invention is closer to the wavelength of the maximum absorption value in the visible light region of the photoconductor of the image forming device than the maximum emission peak in the PL spectrum of the light-emitting material contained in the light-emitting material. By using an optical resonator structure to shift the position of the maximum emission peak wavelength, the light emitted from the organic light-emitting element can be more efficiently absorbed by the photoconductor.

[0018] In an image forming apparatus according to one embodiment of the present invention, the organic compound layer of the organic light-emitting element may include a first organic compound layer between a first electrode and an emitting layer containing a light-emitting material, and a second organic compound layer between the emitting layer and the second electrode. Preferably, the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is closer to the maximum absorption peak wavelength in the visible light region of 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.

[0019] The light emitted from the organic light-emitting element can also be absorbed in the organic compound layer, and the above-mentioned configuration allows the light to be efficiently absorbed by the photoreceptor. In other words, this configuration provides high image formation efficiency. When the organic compound layer has a first organic compound layer and a second organic compound layer, the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element may be closer to the wavelength of the maximum absorption value in the visible light region of the photoreceptor of the image forming device than the wavelength of the longest peak in the absorption spectrum of the first organic compound layer or the second organic compound layer.

[0020] An image forming apparatus according to one embodiment of the present invention may be configured such that the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from the longest peak wavelength in the light absorption spectrum of the first organic compound layer than is the PL spectrum of the light-emitting material.

[0021] Similarly, the maximum emission peak wavelength in the emission spectrum of the organic light-emitting device may be farther from the longest peak wavelength in the light absorption spectrum of the second organic compound layer than the PL spectrum of the light-emitting material, which can be expressed as having a maximum emission peak wavelength in the PL spectrum between the maximum emission peak wavelength in the emission spectrum and the longest peak wavelength in the light absorption spectrum of the organic compound layer.

[0022] The light emitted from the organic light-emitting element can also be absorbed in the organic compound layer, and the above-mentioned configuration allows the light to be efficiently absorbed by the photoconductor. In other words, this configuration provides high image formation efficiency. The emission spectrum influenced by the optical resonator structure can be more efficiently absorbed by the photoconductor than the PL spectrum state.

[0023] In an image forming apparatus according to one embodiment of the present invention, the organic light-emitting element may have a configuration in which the first electrode is a reflective electrode, the second electrode is a light extraction electrode, and the thickness of the second organic compound layer is greater than the thickness of the first organic compound layer. The first electrode may be disposed closer to the substrate than the second electrode. It can also be said that the substrate, first electrode, organic compound layer, and second electrode are disposed in this order.

[0024] When the thickness of the second organic compound layer is greater than that of the first organic compound layer, it is preferable that the longest wavelength peak of the light absorption spectrum of the second organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the first organic compound layer. Since a thick organic compound layer absorbs a large amount of light, increasing the distance from this light absorption spectrum can reduce the amount of light absorbed.

[0025] On the other hand, in an image forming apparatus according to one embodiment of the present invention, the organic light-emitting element may be configured such that the first electrode is a reflective electrode, the second electrode is a light extraction electrode, and the thickness of the first organic compound layer is greater than the thickness of the second organic compound layer.

[0026] When the thickness of the first organic compound layer is greater than that of the second organic compound layer, it is preferable that the longest wavelength peak of the light absorption spectrum of the first organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the second organic compound layer. Since a thick organic compound layer absorbs a large amount of light, increasing the distance from this light absorption spectrum can reduce the amount of light absorbed by the organic compound layer.

[0027] In order to avoid a reduction in the amount of light absorbed by the photoreceptor, the longest wavelength peak of the light absorption spectrum of the organic compound layer having the larger light absorption coefficient out of the first organic compound layer and the second organic compound layer may be configured to be far from the maximum peak wavelength of the emission spectrum. Since an organic compound layer having a larger light absorption coefficient absorbs a large amount of light, increasing the distance from this light absorption spectrum can reduce the amount of light absorbed by the organic compound layer.

[0028] In the image forming apparatus according to one embodiment of the present invention, the organic light emitting element may further include a third organic compound layer between the first organic compound layer and the first electrode, and a fourth organic compound layer between the second organic compound layer and the second electrode.

[0029] In the image-forming apparatus according to one embodiment of the present invention, the organic light-emitting element may further include a first protective layer covering the second electrode.

[0030] In the image forming apparatus according to one embodiment of the present invention, the organic light-emitting element may have a first protective layer made of a first inorganic material, a second protective layer covering the first protective layer made of a second inorganic material, and a resin protective layer.

[0031] An organic light-emitting device according to one embodiment of the present invention may have an optical resonator structure formed by a first electrode and a second electrode. The optical resonator structure is configured such that the optical distance between the first electrode and the second electrode is a distance that reinforces the light emitted from the light-emitting layer, thereby enhancing the intensity of light emitted at a specific wavelength. At least one of the first electrode and the second electrode is a reflective electrode, and the reflective electrode is an electrode that reflects at least a portion of the incident light. A semi-transparent electrode that transmits a portion of the light may be used as the electrode. On the other hand, either the first electrode or the second electrode is a light extraction electrode that transmits light. One of the first electrode and the second electrode may be a reflective electrode, and the other may be a semi-transparent electrode.

[0032] The optical resonator structure of an organic light-emitting device is based on the optical distance between the first and second electrodes, but it can also be calculated by taking into account the typical refractive index and the physical distance between the first and second electrodes. For example, in the case of an organic compound layer, the typical refractive index can be estimated by multiplying the physical distance by 1.8. The typical refractive index may vary depending on the materials that make up the organic compound layer and protective layer. The same applies to other optical interference formations.

[0033] In an organic light-emitting device according to one embodiment of the present invention, when the first electrode is a reflective layer, optical interference may be formed between the first electrode and the light-emitting layer. Forming optical interference means that the distance between the first electrode and the light-emitting layer enhances the intensity of light emitted at a specific wavelength. The specific wavelength here may be light emitted from the light-emitting layer. The same applies to other optical resonator structures and optical interference configurations.

[0034] When an organic light-emitting device according to one embodiment of the present invention has a reflective layer, a first electrode, an organic compound layer including an emitting layer, and a second electrode on a substrate, optical interference may be formed between the reflective layer and the emitting layer. Alternatively, optical interference may be formed between the reflective layer and the second electrode. Either one may be formed, or both may be formed simultaneously. The same applies to other optical resonator structures and other optical interference structures.

[0035] The optical resonator structure is configured so that the optical distance between the electrodes is such that the light emitted from the light-emitting layer is intensified. For example, 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.

[0036] Assuming that manufacturing errors and the like are allowed, the optical distance L1 satisfies 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. 0.7(-Φ1 / (2π)+m1)×λ≦2×L1≦1.2(-Φ1 / (2π)+m1)×λ (Formula 1)

[0037] where λ is the wavelength of light emitted from the light-emitting layer, Φ1 is the phase shift at the reflecting surface, and m1 is an integer. When there are two reflecting surfaces, Φ1 is the sum of the phase shifts.

[0038] An insulating layer may be provided between the reflective layer and the first electrode. The insulating layer may be a layer that adjusts the optical distance depending on its thickness. A conductor may be provided between the reflective layer and the first electrode. The conductor may be a layer that adjusts the optical distance depending on its thickness. It is preferable to have an insulating layer between the reflective layer and the first electrode. The insulating layer may be made of silicon oxide, silicon nitride, or the like.

[0039] In an exposure unit of an image forming apparatus according to one embodiment of the present invention, a light-emitting element is formed on a first surface of a substrate. The substrate may be a light-opaque substrate such as a silicon substrate. A transistor may be provided on the silicon substrate and connected to the organic light-emitting element. The transistor controls the light emission brightness and timing of the organic light-emitting element.

[0040] The present invention will be described in more detail below with reference to the following embodiments, which can be used in combination with one another.

[0041] [First embodiment] FIG. 1 shows the emission spectrum of an organic light-emitting element, the PL spectrum of a light-emitting material, and the light absorption spectrum of a photoreceptor in an exposed area of ​​an image forming apparatus according to this embodiment. In this embodiment, an organic light-emitting element is used in which a first electrode, an organic compound layer including a light-emitting layer, and a second electrode are formed in this order on a first surface of a substrate. In this embodiment, the first electrode and the second electrode form an optical resonator structure. The image forming apparatus according to this embodiment is an example in which the maximum emission peak wavelength of the emission spectrum is shifted to a longer wavelength in order to approach the maximum value of the light absorption spectrum of the photoreceptor.

[0042] In Figure 1(a), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the optical absorption spectrum. Emission spectrum 1 is the emission spectrum reaching the surface of the photoconductor. The position of the maximum emission peak in emission spectrum 1 is shifted by the optical resonator structure. Emission spectrum 1 is drawn to scale in Figure 1, but the units are arbitrary. PL spectrum 2 is the spectrum emitted by the luminescent material contained in the light-emitting layer. Optical absorption spectrum 3 of the photoconductor represents the spectrum of light absorbed by the photoconductor. The maximum emission peak wavelength of emission spectrum 1 is closer to the maximum wavelength in the visible light range of optical absorption spectrum 3 of the photoconductor than the maximum emission peak wavelength of PL spectrum 2. The optical resonator structure is adjusted by the layer thickness of the organic compound layer disposed between the first and second electrodes. Because the maximum emission peak wavelength of emission spectrum 1 is shifted by the optical resonator structure, the amount of light absorbed by the photoconductor is greater than that of PL spectrum 2.

[0043] Emission spectrum 1 has a maximum emission peak wavelength near 620 nm. PL spectrum 2 has a maximum emission peak wavelength near 610 nm. The wavelength at which the absorptance of the photoreceptor's light absorption spectrum 2 is at its maximum is the range at around 700 nm where the absorptance is highest. When the range at which the maximum value is reached is wide, extending beyond 100 nm, the wavelength closest to the emission spectrum is used for comparison.

[0044] By comparing the peaks of each spectrum, it is possible to estimate the amount of light absorbed by the first organic compound layer from the emission spectrum, because the emission spectrum and light absorption spectrum of an organic compound have a broadening in the wavelength direction.

[0045] The emission spectrum and light absorption spectrum are determined by the materials constituting the organic light-emitting element and the photosensitive member, and the image forming apparatus according to this embodiment can be configured by appropriately selecting the materials. The wavelength enhanced by the optical resonator structure can be adjusted by appropriately selecting the first electrode, the organic compound layer, and the second electrode.

[0046] The image forming apparatus according to this embodiment is configured such that the maximum emission peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive member than the maximum emission peak wavelength of the PL spectrum, and therefore is an image forming apparatus with high image formation efficiency.

[0047] [Second embodiment] The image forming apparatus according to this embodiment is the same as that according to the first embodiment, except that the maximum value of the absorption spectrum 3 of the photoreceptor is at a shorter wavelength than the PL spectrum 2. In FIG. 1(b), like FIG. 1(a), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the light absorption spectrum. The emission spectrum 1, PL spectrum 2, and light absorption spectrum 3 of the photoreceptor are the same as those according to the first embodiment. The emission spectrum 1 has a maximum emission peak wavelength near 410 nm. The PL spectrum 2 has a maximum emission peak wavelength near 440 nm. The light absorption spectrum 3 of the photoreceptor has a maximum value near 390 nm.

[0048] The image forming apparatus according to this embodiment is an example in which the maximum emission peak wavelength of the emission spectrum is shifted to a shorter wavelength in order to approach the maximum value of the light absorption spectrum of the photosensitive member.

[0049] By comparing the peaks of each spectrum, it is possible to estimate the amount of light absorbed by the first organic compound layer from the emission spectrum, because the emission spectrum and light absorption spectrum of an organic compound have a broadening in the wavelength direction.

[0050] The image forming apparatus according to this embodiment is configured such that the maximum emission peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive member than the maximum emission peak wavelength of the PL spectrum, and therefore is an image forming apparatus with high image formation efficiency.

[0051] [Third embodiment] The image forming apparatus according to this embodiment is the same as that according to the first embodiment, except that the organic light-emitting element has a first organic compound layer between the first electrode and the light-emitting layer, and a second organic compound layer between the light-emitting layer and the second electrode. Figure 2 shows the emission spectrum of the organic light-emitting element, the PL spectrum of the light-emitting material, the light absorption spectrum of the photoreceptor, and the light absorption spectrum of the organic compound layer in the exposure unit of the image forming apparatus according to this embodiment.

[0052] In Figure 2(a), like Figure 1(a), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the light absorption spectrum. The emission spectrum 1, PL spectrum 2, and light absorption spectrum 3 of the photoreceptor are the same as those in the first embodiment. The light absorption spectrum 4 of the first organic compound layer is the absorption spectrum of light absorbed by the first organic compound layer. This represents the absorption spectrum of light absorbed by the organic compounds contained in the first organic compound layer. When the first organic compound layer contains multiple organic compounds, the absorption spectrum can also be estimated taking into account the weight ratio of the organic compounds contained therein. The absorption spectrum 5 of the second organic compound layer is the absorption spectrum of light absorbed by the second organic compound layer.

[0053] The light absorption spectrum 4 of the first organic compound layer has a longest wavelength peak around 380 nm. By comparing the longest wavelength peak with the peak of the emission spectrum, the amount of light in the emission spectrum absorbed by the first organic compound layer can be estimated. This is because the emission spectrum and light absorption spectrum of organic compounds have a broad wavelength range. The light absorption spectrum 5 of the second organic compound layer has a longest wavelength peak around 350 nm.

[0054] The maximum emission peak wavelength of the emission spectrum 1 is farther from the longest peak wavelength in the light absorption spectrum of the first organic compound layer than the maximum emission peak wavelength of the PL spectrum. Also, the maximum emission peak wavelength of the emission spectrum 1 is farther from the longest peak wavelength in the light absorption spectrum of the second organic compound layer than the maximum emission peak wavelength of the PL spectrum. In other words, the emission spectrum is less susceptible to light absorption by the first or second organic compound layer than the PL spectrum.

[0055] The image forming apparatus according to this embodiment is an image forming apparatus having high image formation efficiency because the maximum peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive body than the longest peak wavelength of the light absorption spectrum of the first organic compound layer and the longest peak wavelength of the light absorption spectrum of the second organic compound layer.

[0056] In this embodiment, the maximum peak wavelength of the emission spectrum of both the first organic compound layer and the second organic compound layer is closer to the wavelength of the maximum value of the light absorption spectrum of the photoconductor. Alternatively, the maximum peak wavelength of the emission spectrum of the second organic compound layer may be closer to the wavelength of the maximum value of the light absorption spectrum of the photoconductor than either the first organic compound layer or the second organic compound layer.

[0057] [Fourth embodiment] The image forming apparatus according to this embodiment is the same as that according to the second embodiment, except that the organic light-emitting element has a first organic compound layer between the first electrode and the light-emitting layer, and a second organic compound layer between the light-emitting layer and the second electrode.

[0058] In Figure 2(b), as in Figure 1(b), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the light absorption spectrum. The emission spectrum 1, PL spectrum 2, and light absorption spectrum 3 of the photoreceptor are the same as those in the second embodiment. The absorption spectrum 4 of the first organic compound layer and the absorption spectrum 5 of the second organic compound layer are the same as those in the third embodiment. The light absorption spectrum 4 of the first organic compound layer is shown by a solid line, the light absorption spectrum 5 of the second organic compound layer is shown by a dashed line, and the light absorption spectrum 3 of the photoreceptor is shown by a dashed line.

[0059] The emission spectrum 1 has a maximum emission peak wavelength near 410 nm. The PL spectrum 2 has a maximum emission peak wavelength near 440 nm. The photoreceptor's light absorption spectrum 3 has a maximum value near 390 nm.

[0060] The image forming apparatus according to this embodiment is an example in which the maximum emission peak wavelength of the emission spectrum is shifted to a shorter wavelength in order to approach the maximum value of the light absorption spectrum of the photosensitive member.

[0061] The light absorption spectrum 4 of the first organic compound layer has a longest wavelength peak around 380 nm. By comparing the longest wavelength peak with the peak of the emission spectrum, the amount of light in the emission spectrum absorbed by the first organic compound layer can be estimated. This is because the emission spectrum and light absorption spectrum of organic compounds have a broad wavelength range. The light absorption spectrum 5 of the second organic compound layer has a longest wavelength peak around 350 nm.

[0062] The image forming apparatus according to this embodiment is an image forming apparatus having high image formation efficiency because the maximum peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive body than the longest peak wavelength of the light absorption spectrum of the first organic compound layer and the longest peak wavelength of the light absorption spectrum of the second organic compound layer.

[0063] In this embodiment, the maximum peak wavelength of the emission spectrum of both the first organic compound layer and the second organic compound layer is closer to the wavelength of the maximum value of the light absorption spectrum of the photoconductor. Alternatively, the maximum peak wavelength of the emission spectrum of the second organic compound layer may be closer to the wavelength of the maximum value of the light absorption spectrum of the photoconductor than either the first organic compound layer or the second organic compound layer.

[0064] [Fifth embodiment] The image forming apparatus according to this embodiment is the same as that according to the first embodiment, except that the organic light-emitting element has a second organic compound layer between the light-emitting layer and the second electrode. The material of the second organic compound layer is different from that according to the third and fourth embodiments. Figure 3 shows the emission spectrum of the organic light-emitting element, the PL spectrum of the light-emitting material, the light absorption spectrum of the photoreceptor, and the light absorption spectrum of the organic compound layer in the exposure section of the image forming apparatus according to this embodiment.

[0065] In Figure 3(a), like Figure 1(a), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the light absorption spectrum. The emission spectrum 1, PL spectrum 2, and light absorption spectrum 3 of the photoreceptor are the same as those in the first embodiment. The light absorption spectrum 6 of the second organic compound layer is the absorption spectrum of light absorbed by the second organic compound layer. The light absorption spectrum 6 of the second organic compound layer has a maximum absorption peak around 350 nm.

[0066] When the peak of the light absorption spectrum of the organic compound layer overlaps with the light absorption spectrum of the photoreceptor, the light absorptance of the organic compound layer is preferably 1 / 5 or less of the light absorptance of the light absorption spectrum of the photoreceptor, in order to reduce the light absorption by the organic compound layer and allow the photoreceptor to absorb light.

[0067] The image forming apparatus according to this embodiment is an image forming apparatus having high image formation efficiency because the maximum peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive body than to the peak wavelength of the light absorption spectrum of the second organic compound layer.

[0068] The maximum emission peak wavelength of the emission spectrum 1 is farther from the wavelength of the maximum absorption value of the light absorption spectrum 6 of the second organic compound layer than the maximum emission peak wavelength of the PL spectrum, so that the image forming device has high image formation efficiency.

[0069] [Sixth embodiment] The image forming apparatus according to this embodiment is the same as that according to the second embodiment, except that the organic light-emitting element has a second organic compound layer between the light-emitting layer and the second electrode, and the material of the second organic compound layer is different from that according to the third and fourth embodiments.

[0070] In FIG. 3(b), like FIG. 1(b), the horizontal axis represents wavelength, and the vertical axis represents intensity for the emission spectrum and absorptance for the light absorption spectrum. The emission spectrum 1, PL spectrum 2, and light absorption spectrum 3 of the photoreceptor are the same as those in the second embodiment. The light absorption spectrum 6 of the second organic compound layer is the absorption spectrum of light absorbed by the second organic compound layer. The light absorption spectrum 6 of the second organic compound layer has a maximum absorption peak around 350 nm.

[0071] When the peak of the light absorption spectrum of the organic compound layer overlaps with the light absorption spectrum of the photoreceptor, the light absorptance of the organic compound layer is preferably 1 / 5 or less of the light absorptance of the light absorption spectrum of the photoreceptor, in order to reduce the light absorption by the organic compound layer and allow the photoreceptor to absorb light.

[0072] The image forming apparatus according to this embodiment is an image forming apparatus having high image formation efficiency because the maximum peak wavelength of the emission spectrum is closer to the wavelength of the maximum value of the light absorption spectrum of the photosensitive body than to the peak wavelength of the light absorption spectrum of the second organic compound layer.

[0073] The maximum emission peak wavelength of the emission spectrum 1 is farther from the wavelength of the maximum absorption value of the light absorption spectrum 6 of the second organic compound layer than the maximum emission peak wavelength of the PL spectrum, so that the image forming device has high image formation efficiency.

[0074] [Configuration of organic light-emitting element] An organic light-emitting element is an electronic element having a first electrode, an organic compound layer, and a second electrode. It emits light by charge injection from these electrodes. As described above, the organic compound layer may be composed of multiple layers, such as a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer. Examples of organic compounds that can be contained in these layers are listed below.

[0075] In the organic light-emitting device according to this embodiment, conventionally known low-molecular-weight and high-molecular-weight hole-injecting or hole-transporting compounds, host compounds, light-emitting compounds, electron-injecting or electron-transporting compounds, etc. may be used together as needed. Examples of these compounds are listed below.

[0076] As the hole injection transport material, a material with high hole mobility is preferred, which facilitates the injection of holes from the anode and transports the injected holes to the light-emitting layer. Furthermore, a material with a high glass transition temperature is preferred to suppress deterioration of film quality, such as crystallization, in the organic light-emitting device. Examples of low-molecular-weight and high-molecular-weight materials with hole injection transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene), and other conductive polymers. Furthermore, the above-mentioned hole injection transport materials are also suitable for use in electron blocking layers. Specific examples of compounds usable as hole injection transport materials are listed below, but the present invention is not limited to these.

[0077] [ka]

[0078] Examples of light-emitting materials that are primarily involved in light-emitting function include fused ring compounds (e.g., fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives, rubrene, etc.), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organoaluminum complexes such as tris(8-quinolinolato)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylenevinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives. Specific examples of compounds that can be used as light-emitting materials are shown below, but are not limited to these.

[0079] [ka]

[0080] [ka]

[0081] Specific examples of the host or assist contained in the light-emitting layer include, but are not limited to, aromatic hydrocarbon compounds or derivatives thereof, carbazole derivatives, azine derivatives, xanthone derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organic aluminum complexes such as tris(8-quinolinolato)aluminum, and organic beryllium complexes. Specific examples are shown below.

[0082] [ka]

[0083] The electron transport material can be arbitrarily selected from those capable of transporting electrons injected from the cathode to the light-emitting layer, and is selected taking into consideration the balance with the hole mobility of the hole transport material. 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, chrysene derivatives, anthracene derivatives, etc.). Furthermore, the above electron transport materials are also suitable for use in hole-blocking layers. Specific examples of compounds used as electron transport materials are listed below, but of course, the present invention is not limited to these. Specific examples are listed below.

[0084] [ka]

[0085] The electron injection material can be selected from those that allow easy electron injection from the cathode, taking into consideration the balance with hole injection properties, etc. Examples of organic compounds include n-type dopants and reducing dopants. Examples include compounds containing alkali metals such as lithium fluoride, lithium complexes such as lithium quinolinol, benzimidazolidene derivatives, imidazolidene derivatives, fulvalene derivatives, and acridine derivatives. They can also be used in combination with the above-mentioned electron transport materials.

[0086] [Other configurations of organic light-emitting devices] The organic light-emitting element is provided by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode on a first surface of a substrate. A protective layer, a color filter, a microlens, etc. may be provided on the second electrode. When a color filter is provided, a planarizing layer may be provided between the protective layer and the color filter. The planarizing layer may be made of an acrylic resin or the like. The same applies when a planarizing layer is provided between the color filter and the microlens.

[0087] [substrate] Examples of the substrate include quartz, glass, a silicon wafer, a resin, and a metal. Furthermore, the substrate may be provided with a switching element such as a transistor and wiring, and an insulating layer thereon. Any material can be used for the insulating layer, as long as it can form contact holes so that wiring can be formed between the first electrode and the insulating layer, and can ensure insulation from wiring that is not connected. For example, resins such as polyimide, silicon oxide, silicon nitride, etc. can be used.

[0088] [electrode] A pair of electrodes can be used. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode with 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.

[0089] The anode material should have as high a work function as possible. Examples include simple metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, and tungsten, mixtures containing these metals, alloys of these metals, and metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and zinc indium oxide. Conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used.

[0090] These electrode materials may be used alone or in combination of two or more. The anode may be composed of one layer or multiple layers.

[0091] When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys or laminates thereof can be used. The above materials can also function as a reflective film without functioning as an electrode. When used as a transparent electrode, transparent conductive oxide layers such as indium tin oxide (ITO) and indium zinc oxide can be used, but are not limited to these. Photolithography techniques can be used to form the electrode.

[0092] On the other hand, materials with a low work function are preferred for the cathode. Examples include alkali metals such as lithium, alkaline earth metals such as calcium, and metals such as aluminum, titanium, manganese, silver, lead, and chromium, as well as mixtures containing these metals. Alternatively, alloys combining these metals can be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, and zinc-silver can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials can be used alone or in combination. The cathode can have either a single-layer or multi-layer structure. Among these, silver is preferred, and a silver alloy is even more preferred to reduce silver aggregation. The alloy ratio is not critical as long as silver aggregation can be reduced. For example, the silver:other metal ratio can be 1:1, 3:1, or the like.

[0093] The cathode may be a top-emission element using an oxide conductive layer such as ITO, or a bottom-emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. The method for forming the cathode is not particularly limited, but DC and AC sputtering methods are more preferred because they provide good film coverage and make it easier to reduce resistance.

[0094] [Organic compound layer] The organic compound layer constituting the organic light-emitting device according to one embodiment of the present invention can be formed by dry processes such as vacuum deposition, ionization deposition, sputtering, plasma, etc. Alternatively to the dry process, a wet process can be used in which the compound is dissolved in an appropriate solvent and a layer is formed by a known coating method (for example, spin coating, dipping, casting, LB method, inkjet method, etc.).

[0095] Here, when a layer is formed by a vacuum deposition method or a solution coating method, crystallization is unlikely to occur and the layer has excellent stability over time. When a film is formed by a coating method, the film can be formed by combining with an appropriate binder resin.

[0096] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0097] These binder resins may be used singly or in combination as homopolymers or copolymers, and may further contain known additives such as plasticizers, antioxidants, and ultraviolet absorbers, if necessary.

[0098] [Charge generation layer] The charge generation layer may be formed by forming an n / p junction with a p layer and an n layer, or by using a p-doped layer or an n-doped layer. For example, when only a P / N junction is formed, it is preferable to provide an electron injection layer to further inject electrons extracted by the P layer into the electron transport layer. An n-doped layer / p-doped layer may also be used. The present invention is not limited to any particular combination of charge generation layers.

[0099] The p-doped layer may be made by mixing Lewis acids such as HAT-CN and molybdenum oxide, which have high electron-withdrawing properties, with aromatic amine compounds. HAT-CN and molybdenum oxide are n-type materials, which means that they can be stacked by withdrawing electrons. The p-doped layer or the np junction consisting of a stack of n-type material and p-type material is treated as a p-charge generation layer.

[0100] The n-doped layer is preferably made of a material with a low work function, such as an alkali metal or alkaline earth metal, which is easy to dope with electrons. In this invention, the n-doped layer is treated as an n-charge generation layer. Alternatively, an electron injection layer may be formed by combining a thin film of a reducing metal such as LiF, forming an n-type layer and a p-type layer to generate charges.

[0101] Examples of n dopants that can be used include alkali metals such as Li, Na, K, Rb, and Cs, alkaline earth metals such as Mg, Ca, Sr, and Ba, and rare earth metals such as Yb, as well as 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).

[0102] [Protective layer] A protective layer may be provided on the second electrode. For example, by adhering glass with a moisture absorbent on the second electrode, the infiltration of water and other contaminants into the organic compound layer can be reduced, thereby reducing the occurrence of display defects. In another embodiment, a passivation film such as silicon nitride may be provided on the second electrode to reduce the infiltration of water and other contaminants into the organic compound layer. For example, after forming the second electrode, the second electrode may be transferred to another chamber without breaking the vacuum, and a 2 μm-thick silicon nitride film may be formed by CVD to serve as a protective layer. A protective layer may be provided using atomic layer deposition (ALD) after the CVD film formation. The material of the film formed by ALD is not limited, and may be silicon nitride, silicon oxide, aluminum oxide, or the like. Silicon nitride may be further formed on the film formed by ALD by CVD. The film formed by ALD may have a thickness smaller than that of the film formed by CVD. Specifically, the thickness may be 50% or less, or even 10% or less.

[0103] [Planarization layer] A planarizing layer may be provided on the protective layer. The planarizing layer is provided for the purpose of reducing the unevenness of the layer below. It may also be called a material resin layer without limiting its purpose. The planarizing layer may be composed of an organic compound, and may be either a low molecular weight or a high molecular weight, but a high molecular weight is preferred.

[0104] The planarizing layer may be provided above or below the color filter, and may be made of the same or different materials, such as polyvinyl carbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0105] [Microlens] An organic light-emitting element or a light-emitting device having an organic light-emitting element may have an optical component such as a microlens on its light-emitting side. The microlens may be made of acrylic resin, epoxy resin, or the like. The microlens may be intended to increase the amount of light extracted from the organic light-emitting element or light-emitting device or 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 to the hemisphere, there is a tangent that is parallel to the insulating layer, and the point of contact between this tangent and the hemisphere is the vertex of the microlens. The vertex of the microlens can be determined in the same way in any cross-sectional view. In other words, among the tangents to the semicircle of the microlens in the cross-sectional view, there is a tangent that is parallel to the insulating layer, and the point of contact between this tangent and the semicircle is the vertex of the microlens.

[0106] It is also possible to define the midpoint of a microlens. In the cross section of the microlens, a line segment is imagined from the point where an arc shape ends to the point where another arc shape ends, and the midpoint of this line segment can be called the midpoint of the microlens. The cross section for determining the vertex and midpoint may be a cross section perpendicular to the insulating layer.

[0107] [Counter substrate] An opposing substrate may be provided on the planarization layer. The opposing substrate is called an opposing substrate because it is provided at a position corresponding to the aforementioned substrate. The constituent material of the opposing substrate may be the same as that of the aforementioned substrate. When the aforementioned substrate is defined as a first substrate, the opposing substrate may be a second substrate.

[0108] [Pixel circuit] A light-emitting device having organic light-emitting elements may have a pixel circuit connected to the organic light-emitting elements. The pixel circuit may be an active matrix type that controls the emission of a plurality of organic light-emitting elements independently. The active matrix type circuit may be voltage-programmed or current-programmed. The drive circuit has a pixel circuit for each pixel. The pixel circuit may have an organic light-emitting element, a transistor that controls the emission luminance of the organic light-emitting element, a transistor that controls the emission timing, a capacitor that holds the gate voltage of the transistor that controls the emission luminance, and a transistor for connecting to GND without going through the light-emitting element.

[0109] The light-emitting device has a display area and a peripheral area arranged around the display area. The display area has a pixel circuit, and the peripheral area has a display control circuit. The mobility of a transistor constituting the pixel circuit may be smaller than the mobility of a transistor constituting the display control circuit. The slope of the current-voltage characteristics of the transistor constituting the pixel circuit may be smaller than the slope of the current-voltage characteristics of the transistor constituting the display control circuit. The slope of the current-voltage characteristics can be measured by the so-called Vg-Ig characteristics. The transistor constituting the pixel circuit is a transistor connected to an organic light-emitting element.

[0110] The drive circuit may control the light-emitting points of the exposed portions, and may have a transistor that controls the amount of current flowing through the organic light-emitting element and the timing at which the organic light-emitting element emits light.

[0111] [Configuration of image forming device] The image forming apparatus according to the present invention has a photoconductor and an exposure unit, and the exposure unit has the organic light-emitting element described above. The photoconductor and the photoconductor drum will be described below.

[0112] [Photoreceptor] The photoreceptor has a support on which an undercoat layer, a charge generation layer, a charge transport layer, and a surface layer are laminated. The photosensitive layer may be a laminated type photosensitive layer having a charge generation layer and a charge transport layer, or may be a single-layer type photosensitive layer containing a charge generation material and a charge transport material.

[0113] A method for manufacturing the photosensitive drum of the present disclosure includes preparing a coating liquid for each layer described below, coating the desired layers in order, and drying the coating liquid. Examples of methods for applying the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.

[0114] The configuration of the photosensitive drum of the present disclosure will be described below.

[0115] [Support] The support of the photosensitive drum is preferably conductive (conductive support). The support of the present disclosure has a drum (cylindrical) shape. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like.

[0116] The support material is preferably a metal, a resin, a glass, etc. Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support using aluminum is preferred.

[0117] It is also preferable to impart electrical conductivity to the resin or glass by processing such as mixing or coating with an electrically conductive material.

[0118] [Undercoat layer] In the present disclosure, an undercoat layer may be provided on the support. The undercoat layer is provided for the purposes of improving the adhesion of the photosensitive layer, improving coating properties, improving charge injection from the support, protecting the photosensitive layer from electrical breakdown, and suppressing interference fringes due to scattering of image exposure. The undercoat layer may be a single undercoat layer containing one of the materials listed below, or two or more different undercoat layers containing the materials listed below may be laminated together.

[0119] Examples of metal oxide particles include particles of indium tin oxide, tin oxide, indium oxide, titanium oxide, strontium titanate, zinc oxide, and aluminum oxide. Silicon dioxide particles can also be used. Examples of metal particles include particles of gold, silver, and aluminum.

[0120] The primary particle size of the metal oxide particles is preferably 0.1 μm or less in number average particle size from the viewpoint of dispersibility in the coating liquid for the undercoat layer and electrical properties of the photosensitive drum.

[0121] In the present disclosure, the metal oxide particles may be a mixture of two or more types of metal oxide particles, such as particles of different types of metal oxide, particles with different types of surface treatment, particles with different particle sizes or specific surface areas, etc.

[0122] The metal oxide particles contained in the undercoat layer may be particles whose surfaces have been treated with a surface treatment agent such as a silane coupling agent in order to suppress black dot-like image defects caused by charge injection from the support to the photosensitive layer.

[0123] The surface treatment of the metal oxide particles can be carried out by a common method, such as a dry method or a wet method.

[0124] In the dry method, metal oxide particles are stirred in a mixer capable of high-speed stirring, such as a Henschel mixer, and an alcohol aqueous solution, organic solvent solution, or aqueous solution containing a surface treatment agent is added to the metal oxide particles to uniformly disperse them, followed by drying.

[0125] In the wet method, metal oxide particles and a surface treatment agent are stirred in a solvent or dispersed in a sand mill using glass beads or the like, and after dispersion, the solvent is removed by filtration or vacuum distillation. After solvent removal, it is preferable to further bake the mixture at 100°C or higher.

[0126] The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

[0127] Examples of resins include acrylic resins, allyl resins, alkyd resins, ethyl cellulose resins, ethylene-acrylic acid copolymers, epoxy resins, casein resins, and silicone resins. Examples 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. Other examples include polycarbonate resins, polystyrene resins, polysulfone resins, polyvinyl alcohol resins, polybutadiene resins, and polypropylene resins. Among these, urethane resins with low hygroscopicity are preferred from the viewpoint of suppressing potential fluctuations in high-temperature, high-humidity environments.

[0128] 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 hydroxy group, an amino group, a carboxy group, a thiol group, a carboxylic anhydride group, and a carbon-carbon double bond group.

[0129] The mass ratio (P / B) of the metal oxide particles (P) to the binder resin (B) in the undercoat layer is preferably 1.0 / 1.0 or more and 3.0 / 1.0 or less.

[0130] Furthermore, for the purpose of improving electrical properties, the undercoat layer may further contain an electron transporting substance, metal particles, a conductive polymer, etc. Among these, it is preferable to use an electron transporting substance.

[0131] Examples of electron transport substances include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, oxadiazole compounds, diphenoquinone compounds, xanthone compounds, alizarin compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silole compounds, and boron-containing compounds.

[0132] The undercoat layer may be formed as a cured film by using an electron transporting substance having a polymerizable functional group as the electron transporting substance and copolymerizing it with the above-mentioned monomer having a polymerizable functional group.

[0133] The undercoat layer may further contain organic resin particles or a leveling agent for the purposes of, for example, adjusting surface roughness, promoting light scattering, or reducing cracking. The organic resin particles may be hydrophobic organic resin particles such as silicone particles or hydrophilic organic resin particles such as crosslinked polymethacrylate resin (PMMA) particles.

[0134] The undercoat layer may further contain additives, such as particles of conductive materials such as carbon black, charge transport materials, metal chelate compounds, organometallic compounds, and other known materials.

[0135] The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming a coating film of this on the support or the conductive layer, and drying and / or curing it.

[0136] Examples of solvents used in the coating liquid for the undercoat layer include organic solvents such as alcohols, sulfoxides, ketones, ethers, esters, halogenated aliphatic hydrocarbons, aromatic compounds, etc. In the present disclosure, it is preferable to use alcohol-based and ketone-based solvents.

[0137] Dispersion methods for preparing the coating liquid for the undercoat layer include methods using a homogenizer, ultrasonic disperser, ball mill, sand mill, roll mill, vibration mill, attritor, and liquid collision type high-speed disperser.

[0138] The thickness of the undercoat layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.3 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0139] [Photosensitive layer] The photosensitive layer of a photosensitive drum is mainly classified into (1) a multi-layer type photosensitive layer and (2) a single-layer type photosensitive layer. (1) A multi-layer type photosensitive layer is a photosensitive layer having a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. (2) A single-layer type photosensitive layer is a photosensitive layer containing both a charge generation material and a charge transport material.

[0140] (1) Laminated photosensitive layer The laminated photosensitive layer has a charge generating layer and a charge transport layer.

[0141] (1-1) Charge generation layer The charge generating layer preferably contains a charge generating material and a resin.

[0142] Examples of charge-generating materials include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.

[0143] The content of the charge generating material in the charge generating layer 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.

[0144] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferred.

[0145] The charge generating layer may further contain additives such as antioxidants and ultraviolet absorbers, etc. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0146] The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming a coating film of this on the undercoat layer, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0147] The thickness of the charge generating layer 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.

[0148] (1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a binder material.

[0149] When a protective layer, which will be described later, is not provided, the charge transport layer becomes the surface layer of the photosensitive drum.

[0150] 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 materials. Among these, triarylamine compounds are preferred.

[0151] The content of the charge transport material in the charge transport layer is preferably 25% by mass to 70% by mass, and more preferably 30% by mass to 55% by mass, based on the total mass of the charge transport layer.

[0152] As the binding material, a thermoplastic resin (hereinafter also referred to as "resin") is used.

[0153] Examples of thermoplastic resins include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among these, polycarbonate resins and polyester resins are preferred. As the polyester resin, polyarylate resins are particularly preferred.

[0154] The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.

[0155] The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, etc. Specific examples of such 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.

[0156] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming a coating film of this on the charge generation layer, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents and aromatic hydrocarbon-based solvents are preferred.

[0157] The thickness of the charge transport layer is preferably from 5 μm to 50 μm, more preferably from 8 μm to 40 μm, and particularly preferably from 10 μm to 30 μm.

[0158] (2) Single-layer photosensitive layer The single-layer photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating material, a charge transport material, a resin, and a solvent, forming the coating on the undercoat layer, and drying the coating. The charge generating material, charge transport material, and resin are the same as those exemplified in "(1) Multilayer Photosensitive Layer" above.

[0159] [Protective layer] In the present disclosure, a protective layer may be provided on the photosensitive layer. Providing a protective layer can improve durability. When a protective layer is provided, the protective layer serves as the surface layer of the photosensitive drum. The protective layer may be formed as a cured film by polymerizing a composition containing, for example, a monomer having a polymerizable functional group, which is a raw material for the binder material. Examples of the reaction include thermal polymerization, photopolymerization, and radiation-induced polymerization. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylmethylol group, an epoxy group, a metal alkoxyl group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic anhydride group, and a group containing a carbon-carbon double bond. Examples of the group containing a carbon-carbon double bond include an acryloyl group and a methacryloyl group. A monomer having charge transport capability may be used as the monomer having a polymerizable functional group.

[0160] Here, the cured product of the monomer having a polymerizable functional group is the binder material of the protective layer. As the monomer having a polymerizable functional group, it is preferable to use a hole transporting compound having a chain-polymerizable functional group.

[0161] The hole transporting compound having a chain-polymerizable functional group is more preferably a compound represented by the following formula (CT-1) or (CT-2).

[0162] [ka]

[0163] In the formula (CT-1), Ar11 to Ar13 each independently represent a substituted aryl group or an 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 formulae (P-1) to (P-3). However, the compound represented by the formula (CT-1) has at least one monovalent functional group represented by any one of the following formulae (P-1) to (P-3).

[0164] [ka]

[0165] In the formula (CT-2), Ar21 to Ar24 each independently represent a substituted aryl group or an unsubstituted aryl group, and Ar25 represents a substituted arylene group or an unsubstituted arylene group. The substituent that the substituted aryl group may have is an alkyl group having from 1 to 6 carbon atoms, or a monovalent functional group represented by any of the following formulae (P-1) to (P-3). The substituent that the substituted arylene group may have is an alkyl group having from 1 to 6 carbon atoms, or a monovalent functional group represented by any of the following formulae (P-1) to (P-3). However, the compound represented by the formula (CT-2) has at least one monovalent functional group represented by any of the following formulae (P-1) to (P-3).

[0166] [ka]

[0167] In the formula (P-1), Z11 represents a single bond or an alkylene group having 1 to 6 carbon atoms, and X11 represents a hydrogen atom or a methyl group.

[0168] [ka]

[0169] In the formula (P-2), Z21 represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0170] [ka]

[0171] In the formula (P-3), Z31 represents a single bond or an alkylene group having 1 to 6 carbon atoms.

[0172] The protective layer may contain fluorine atom-containing resin particles, which can improve the abrasion resistance of the protective layer.

[0173] Examples of resins contained in the fluorine atom-containing resin particles include polytetrafluoroethylene resin, polychlorotrifluoroethylene resin, polytetrafluoroethylenepropylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, and polydichlorodifluoroethylene resin. It is also preferable to use particles containing multiple types of the above resins. Among the above, from the viewpoint of improving dispersibility, it is more preferable that the fluorine atom-containing resin particles be polytetrafluoroethylene (PTFE) resin.

[0174] In cross-sectional observation of the surface layer, the fluorine atom-containing resin particles preferably have an arithmetic mean of the major axes of the primary particles (average primary particle size) measured from a secondary electron image taken with a scanning electron microscope of 150 nm to 300 nm, from the viewpoints of improving dispersibility and suppressing potential fluctuations.More preferably, the fluorine atom-containing resin particles have an average primary particle size of 180 nm to 250 nm.

[0175] The content of the fluorine atom-containing resin particles in the protective layer is preferably from 5 to 40% by mass, more preferably from 25 to 35% by mass, based on the total mass of the protective layer.

[0176] The protective layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, etc. Specific examples 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.

[0177] The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming a coating film of this on the photosensitive layer, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0178] The thickness of the protective layer is preferably 0.50 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

[0179] [Photosensitive drum surface treatment] In the present disclosure, the surface of the photosensitive drum may be processed. By performing the surface processing, the behavior of the cleaning means (cleaning blade) that comes into contact with the photosensitive drum can be further stabilized. Examples of surface processing methods include a method in which a mold having convex portions is pressed against the surface of the photosensitive drum to transfer the shape, a method in which an uneven shape is imparted by mechanical polishing, or a method in which powder is collided with the surface of the photosensitive drum to roughen the surface. In this way, by providing concave or convex portions on the surface layer of the photosensitive drum, the behavior of the cleaning means that comes into contact with the photosensitive drum can be further stabilized.

[0180] The recesses or protrusions may be formed over the entire surface of the photosensitive drum or may be formed on only a part of the surface of the photosensitive drum. When the recesses or protrusions are formed on only a part of the surface of the photosensitive drum, it is preferable that the recesses or protrusions are formed over at least the entire area of ​​contact with the cleaning means (cleaning blade).

[0181] When forming recesses, a mold having protrusions corresponding to the recesses is pressed against the surface of the photosensitive drum to transfer the shape, thereby forming the recesses on the surface of the photosensitive drum.

[0182] [Configuration example of organic light-emitting element and image forming device] Examples of the configuration of the organic light-emitting element and the image forming apparatus are shown below.

[0183] The display device 100 in Fig. 4 includes an organic light-emitting element 26 and a TFT 18 as an example of a transistor. A substrate 11 made of glass, silicon, or the like is provided with an insulating layer 12 on top of it. An active element 18 such as a TFT is disposed on the insulating layer, and a gate electrode 13, a gate insulating film 14, and a semiconductor layer 15 of the active element are disposed on top of it. The TFT 18 also includes the semiconductor layer 15, a drain electrode 16, and a source electrode 17. An insulating film 19 is disposed on top of the TFT 18. An anode 21 constituting the organic light-emitting element 26 and the source electrode 17 are connected via a contact hole 20 provided in the insulating film.

[0184] The electrical connection between the electrodes (anode, cathode) included in the organic light-emitting element 26 and the electrodes (source electrode, drain electrode) included in the TFT is not limited to the embodiment shown in Fig. 4. In other words, it is sufficient that either the anode or the cathode is electrically connected to either the TFT source electrode or the drain electrode. TFT stands for thin film transistor.

[0185] 4 shows the organic compound layer as a single layer in the display device 100, the organic compound layer 22 may be a multi-layer structure. A first protective layer 24 and a second protective layer 25 are provided on the cathode 23 to reduce deterioration of the organic light-emitting element.

[0186] In the display device 100 of FIG. 4, transistors are used as switching elements, but other switching elements may be used instead.

[0187] The transistors used in the display device 100 of Fig. 4 are not limited to transistors using single-crystal silicon wafers, but may also be thin-film transistors having an active layer on an insulating surface of a substrate. Examples of active layers include single-crystal silicon, amorphous silicon, microcrystalline silicon, and other non-single-crystal silicon, and non-single-crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. Thin-film transistors are also called TFT elements.

[0188] The transistors included in the display device 100 of Fig. 4 may be formed within a substrate such as a Si substrate. Here, "formed within a substrate" means that the substrate itself, such as a Si substrate, is processed to form the transistors. In other words, having a transistor within a substrate can be seen as the substrate and the transistor being formed integrally.

[0189] The organic light-emitting element according to this embodiment has its emission brightness controlled by a TFT, which is an example of a switching element. By providing multiple organic light-emitting elements on a surface, an image can be displayed based on the emission brightness of each element. Note that the switching element according to this embodiment is not limited to a TFT, and may be a transistor formed from low-temperature polysilicon or an active matrix driver formed on a substrate such as a Si substrate. "On the substrate" can also be referred to as "inside the substrate." Whether to provide a transistor in the substrate or to use a TFT is determined by the size of the display unit. For example, for a display size of about 0.5 inches, it is preferable to provide the organic light-emitting element on a Si substrate.

[0190] Figure 5 shows an image forming apparatus according to one embodiment of the present invention. Figure 5(a) is a schematic diagram of an image forming apparatus 36 according to one embodiment of the present invention. The image forming apparatus has a photoconductor, an exposure light source, a developing unit, a charging unit, a transfer unit, a transport roller, and a fixing unit.

[0191] Light 29 is irradiated from an exposure light source 28, and an electrostatic latent image is formed on the surface of the photosensitive member 27. This exposure light source has an organic light-emitting element according to the present invention. A developing unit 31 has toner and the like. A charging unit 30 charges the photosensitive member. A transfer device 32 transfers the developed image to a recording medium 34. A transport unit 33 transports the recording medium 34. The recording medium 34 is, for example, paper. A fixing unit 35 fixes the image formed on the recording medium.

[0192] 5(b) and 5(c) are schematic diagrams showing the exposure light source 28 with a plurality of light-emitting units 38 arranged on a long substrate. 37 is a direction parallel to the axis of the photoconductor, and represents the column direction in which the organic light-emitting elements are arranged. This column direction is the same as the axis direction about which the photoconductor 27 rotates. This direction can also be called the long axis direction of the photoconductor.

[0193] Figure 5(b) shows a configuration in which the light-emitting units are arranged along the longitudinal axis of the photoconductor. Figure 5(c) shows a different configuration from (b), in which the light-emitting units are arranged alternately in the column direction in the first and second columns. The first and second columns are arranged at different positions in the row direction.

[0194] The first column has a plurality of light-emitting units arranged at intervals. The second column has light-emitting units at positions corresponding to the intervals between the light-emitting units in the first column. That is, the plurality of light-emitting units are also arranged at intervals in the row direction.

[0195] The arrangement in FIG. 5(c) can also be described as a grid arrangement, a houndstooth arrangement, or a checkerboard pattern.

[0196] 6 is a schematic diagram showing one form of a light-emitting device according to this embodiment. The light-emitting device according to this embodiment can be used, for example, as a light source for an image forming apparatus. The light-emitting device according to this embodiment has a rectangular shape with long sides parallel to a first direction and short sides parallel to a direction intersecting the first direction. For example, the first direction may be a direction along the rotation axis of a photosensitive member of the image forming apparatus.

[0197] The substrate 1701 has a polygonal shape, and an example of a rectangular substrate 1701 will be described here. In this specification, the direction of the long sides of the rectangular substrate 1701 is referred to as the first direction, and the direction of the short sides perpendicular to the long side is referred to as the second direction. In addition, the polygon in this specification also includes shapes with rounded corners. A moisture-resistant ring 1700 is disposed on the rectangular substrate 1701, and serves to suppress and prevent moisture from penetrating into the light-emitting device. The moisture-resistant ring 1700 can be, for example, a guard ring formed of a wiring layer.

[0198] A light-emitting region 1702, a contact region 1703, pads 1704, and a circuit 1706 are arranged inside the moisture-resistant ring 1700. In this embodiment, the contact region 1703 includes a first contact region 1703_1, a second contact region 1703_2, and a third contact region 1703_3. The pads 1704 include a first pad 1704_1, a second pad 1704_2, and a third pad 1704_3.

[0199] Circuit 1706 is a part of the circuitry for driving each light-emitting device, and specific examples include, but are not limited to, an input protection circuit, an input circuit into which data for each drive is input, and a logic circuit for processing data.

[0200] Light-emitting elements EL are arranged in rows and columns in the light-emitting region 1702. Wiring that electrically connects to a common electrode of the light-emitting elements EL is arranged in the contact region 1703. The pad 104_1 electrically connects the contact region 1703 to an external element.

[0201] The outer periphery of the moisture-resistant ring 1700 may include a plurality of recessed portions, which can be used as contact areas for contacting ribs that are part of a mask for vapor deposition in a film-forming process, for example.

[0202] As described above, each of the plurality of light-emitting elements EL arranged in a matrix in the light-emitting region 1702 is composed of a light-emitting layer and a first electrode and a second electrode that sandwich the light-emitting layer. In this embodiment, an example is shown 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 to all the light-emitting elements EL.

[0203] For example, in the case where light-emitting region 1702 has four rows of light-emitting elements EL, the initial positions of the light-emitting elements EL in the first row and the second row may be shifted in the X direction by ¼ of the X-direction dimension of the light-emitting elements EL, as illustrated in Fig. 6. In the case of n rows, where n is an integer of 2 or greater, the initial positions of the light-emitting elements EL in the first row and the second row may be shifted in the X direction by 1 / n of the X-direction dimension of the light-emitting elements EL. Such a configuration is advantageous for improving resolution.

[0204] The contact region 1703 is an area adjacent to the light emitting region 1702 of the substrate 1701, and is disposed inside the moisture-resistant ring 1700. At least one of the first contact region 1703, the pad 104, and the circuit 1706, together with the recess of the moisture-resistant ring 1700, may be disposed between the light emitting region 102 and one long side end of the substrate 1701, and may be disposed in series in the long side direction.

[0205] In this way, by providing the contact region 1703, the pad region 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 can be reduced, making it possible to miniaturize the light emitting device.

[0206] The light-emitting device of this embodiment has multiple contact regions 1703 between the common electrode of the light-emitting element EL and the power supply wiring along the long side edge of the light-emitting device. If the common electrode is made of, for example, a transparent electrode material with relatively high electrical resistance, the amount of voltage drop in the long axis direction may be large. Therefore, the voltage applied to each OLED varies depending on the distance from the contact region to which the potential is supplied. This may result in differences in actual emission brightness between OLEDs to which a voltage is applied to emit light with the same brightness, resulting in shading and other issues. By having multiple contact regions 1703 in the long axis direction as in this embodiment, the voltage drop in the common electrode in the long axis direction can be suppressed, reducing the occurrence of shading and other issues.

[0207] In this embodiment, an example in which a light emitting device is used in a head substrate 1800 of an exposure head of an image forming apparatus will be described with reference to FIG.

[0208] Fig. 7(a) is a schematic perspective view of the head substrate 1800. Fig. 7(b) shows the arrangement of a plurality of light-emitting elements EL provided on the head substrate 1800, and Fig. 7(c) shows an enlarged view of a portion of Fig. 7(b).

[0209] An LED chip 1803 is mounted on the head substrate 1800. As the LED chip 1803, for example, the light emitting device described in the A embodiment can be used.

[0210] 7(a), 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. The one surface of the head substrate 1800 here refers to the surface (upper surface, front surface) on which the LED chip 1803 is provided. The other surface of the substrate refers to the surface (lower surface, back surface) opposite to the side on which the LED chip 1803 is provided.

[0211] The FFC connector 1807 is attached to the other surface (bottom surface, back surface) of the head substrate 1800 so that its longitudinal direction follows the longitudinal direction of the head substrate 1800. The long FFC connector 1807 is provided to input a control signal (drive signal) from a control circuit section of the main body of the image forming apparatus, and the control signal is transferred to each LED chip 1803. The LED chips 1803 are driven (to emit light or turn off) by the control signal input to the head substrate 1800.

[0212] The LED chips 1803 mounted on the head substrate 1800 will now be described. As shown in FIGS. 7(b) and 7(c), a plurality of light-emitting elements EL are arranged on one surface of the head substrate 1800. For example, LED chips 1803-1 to 1803-29 (29 pieces) are arranged. FIG. 7(b) shows LED chips 1803_1, 1803_13, 1803_14, 1803_15, 1803_16, and 1803_29 as examples. Each of the LED chips 1803-1 to 1803-29 has a plurality of light-emitting elements EL arranged in its longitudinal direction, and for example, 516 light-emitting elements EL are arranged.

[0213] The center-to-center distance k2 between adjacent light-emitting elements EL in the longitudinal direction of the LED chip 1803 corresponds to the resolution of the image forming device. For example, when the resolution of the image forming device in this embodiment is 1200 dpi, the light-emitting elements EL are arranged so that the center-to-center distance k2 between adjacent light-emitting elements EL in the longitudinal direction of the LED chips 1803-1 to 1803-29 is 21.16 μm. Therefore, the exposure range of the exposure head in this embodiment is approximately 314 mm.

[0214] The photosensitive layer of the photosensitive drum is formed with a width of 314 mm or more. Since the long side of A4 size recording paper and the short side of A3 size recording paper are 297 mm, the exposure head of this embodiment has an exposure range that can form images on A4 size recording paper and A3 size recording paper. Note that while Figure 7 shows an example in which multiple light-emitting elements EL are arranged in the longitudinal direction, light-emitting elements EL may be arranged in the lateral direction as well as the longitudinal direction.

[0215] A plurality of LED chips 1803-1 to 1803-29 are arranged 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. That is, as shown in FIG. 7(b), counting from the left, odd-numbered LED chips 1803-1, 1803-3, ..., 1803-29 are mounted in a row in the longitudinal direction of the substrate 1800. Also, counting from the left, even-numbered LED chips 1803-2, 1803-4, ..., 1803-28 are mounted in a row in the longitudinal direction of the substrate 1800. The LED chips 1803 are arranged in this manner.

[0216] 7(c), the center-to-center distance k1 of the light-emitting elements EL can be made equal to the center-to-center distance k2 of the light-emitting elements EL in the longitudinal direction of the LED chip 1803. Here, the center-to-center distance k1 of the light-emitting elements EL refers to the center-to-center distance between the light-emitting elements EL arranged at one end of the LED chip 1803_13 and the other end of the LED chip 1803_14. The center-to-center distance k2 of the light-emitting elements EL refers to the center-to-center distance k2 between adjacent light-emitting elements EL in the LED chip 1803_14.

[0217] In other words, the center-to-center distance k1 between adjacent light-emitting elements EL arranged on one end of an LED chip 1803 and the other end of another LED chip 1803 can be made equal to the center-to-center distance k2 between adjacent light-emitting elements EL on one LED chip 1803.

[0218] 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 the substrate along the main scanning direction (the axial direction of the photosensitive drum 2), and are electrically connected in parallel by power supply wiring also arranged along the main scanning direction. A circuit for driving the organic light-emitting elements may be formed on a silicon substrate, and the organic light-emitting elements may be arranged on top of that, or TFTs (Thin Film Transistors) may be formed on a glass substrate, and the organic light-emitting elements may be arranged on top of that.

[0219] When the light-emitting device is used in an exposure head, linear exposure is performed, and therefore the ratio of the longitudinal direction (first direction X) to the lateral direction (second direction Y) of the shape of the light-emitting region 1702 is larger than when the light-emitting device is used in a display device, etc. Similarly, the ratio of the longitudinal direction (first direction X) to the lateral direction (third direction Y) of the shape of the LED chip substrate is also larger.

[0220] Specifically, for example, the length of the long side of the LED chip (or light-emitting region 1702) is at least 5 times the length of the short side of the LED chip (or light-emitting region 1702), and may be at least 10 times the length. For example, the length of the long side of the LED chip (or light-emitting region 1702) can be at least 20 times the length of the short side of the LED chip (or light-emitting region 1702).

[0221] The length of the long side of the LED chip is determined by the axial length of the photosensitive drum 2, 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 in the direction perpendicular to the axis of the photosensitive drum by whether the light-emitting element EL is arranged in the light-emitting region 1702 and the arrangement of the pads 1704 and contact region 1703.

[0222] Furthermore, the organic layer 66 may be configured to have a light-emitting layer that emits red light in consideration of the wavelength dependency of the photosensitivity of the photosensitive drum 2.

[0223] The LED chip 1803 may have a color filter, which can improve print quality by absorbing stray light from unintended directions without reducing the amount of normal light incident on the photosensitive drum.

[0224] As described above, by using a device using the organic light-emitting element according to this embodiment, it is possible to provide a stable display with good image quality even over a long period of time.

[0225] As described above, the image forming apparatus according to the embodiment of the present invention includes the following configuration.

[0226] [composition] [Configuration 1] an organic light-emitting element having an optical resonator structure on a first surface of a substrate; and a photoreceptor that receives light from the organic light-emitting element; the organic light-emitting element has a first electrode, a light-emitting layer containing a light-emitting material, and a second electrode in this order from the first surface; an emission spectrum of the organic light-emitting element resonated by the optical resonator structure has a maximum peak wavelength in the visible light region that is closer to a wavelength of a maximum absorption value in the visible light region of an absorption spectrum of the photoreceptor than to a maximum peak wavelength in the visible light region of a PL spectrum of the light-emitting material.

[0227] [Configuration 2] the organic light-emitting element has a first organic compound layer between the first electrode and a light-emitting layer containing the light-emitting material, and a second organic compound layer between the light-emitting layer and the second electrode, The image forming apparatus according to configuration 1, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is closer to the maximum absorption peak wavelength in the visible light region of 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.

[0228] [Configuration 3] the organic light-emitting element has a first organic compound layer between the first electrode and a light-emitting layer containing the light-emitting material, and a second organic compound layer between the light-emitting layer and the second electrode, The image forming apparatus according to configuration 1, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is closer to the maximum absorption peak wavelength in the visible light region of 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.

[0229] [Configuration 4] The image forming apparatus according to configuration 2, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from the longest peak wavelength in the light absorption spectrum of the first organic compound layer than from the PL spectrum of the light-emitting material.

[0230] [Configuration 5] The image forming apparatus according to configuration 2, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from the longest peak wavelength in the light absorption spectrum of the second organic compound layer than from the PL spectrum of the light-emitting material.

[0231] [Configuration 6] The image forming apparatus according to Configuration 3, wherein a maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from 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 than from the PL spectrum of the light-emitting material.

[0232] [Configuration 7] the first electrode is a reflective electrode, and the second electrode is a light extraction electrode; 3. The image forming apparatus according to configuration 2, wherein the second organic compound layer has a thickness greater than that of the first organic compound layer.

[0233] [Configuration 8] The image forming apparatus according to Configuration 7, wherein the longest wavelength peak of the light absorption spectrum of the second organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the first organic compound layer.

[0234] [Configuration 9] the first electrode is a reflective electrode, and the second electrode is a light extraction electrode; 3. The image forming apparatus according to configuration 2, wherein the thickness of the first organic compound layer is greater than the thickness of the second organic compound layer.

[0235] [Configuration 10] The image forming apparatus according to configuration 9, wherein the longest wavelength peak of the light absorption spectrum of the first organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the second organic compound layer.

[0236] [Configuration 11] 3. The image forming apparatus according to configuration 2, further comprising a third organic compound layer between the first organic compound layer and the first electrode.

[0237] [Configuration 12] 12. The image forming apparatus according to claim 11, further comprising a fourth organic compound layer between the second organic compound layer and the second electrode.

[0238] [Configuration 13] 13. The image forming apparatus according to any one of Structures 1 to 12, further comprising a first protective layer covering the second electrode, the first protective layer being made of a first inorganic material.

[0239] [Configuration 14] 14. The image forming apparatus according to Structure 13, further comprising a second protective layer covering the first protective layer, the second protective layer being made of a second inorganic material.

[0240] [Configuration 15] 15. The image forming apparatus according to Configuration 14, further comprising a second protective layer covering the first protective layer, the second protective layer being made of resin.

[0241] [Configuration 16] 16. The image forming apparatus according to any one of structures 1 to 15, wherein the light-emitting layer comprises at least one of a fluorene derivative, a naphthalene derivative, a pyrene derivative, a perylene derivative, a tetracene derivative, an anthracene derivative, a rubrene derivative, a fluoranthene derivative, a quinacridone derivative, a coumarin derivative, a stilbene derivative, an organoaluminum complex, an iridium complex, a platinum complex, a rhenium complex, a copper complex, a europium complex, a ruthenium complex, a poly(phenylenevinylene) derivative, a poly(fluorene) derivative, and a poly(phenylene) derivative.

[0242] [Configuration 17] 17. The image forming apparatus according to any one of structures 1 to 16, wherein the photoreceptor has at least one of a perylene derivative, an anthraquinone derivative, an anthanthrone derivative, a dibenzpyrenequinone derivative, a pyranthrone derivative, an indigoid derivative, a phthalocyanine derivative, and a perinone derivative.

[0243] [Configuration 18] 3. The image-forming apparatus according to claim 2, wherein the first organic compound layer is made of only an arylamine compound.

[0244] [Configuration 19] 3. The image forming apparatus according to claim 2, wherein the second organic compound layer is made of only an aromatic hydrocarbon compound.

[0245] [Configuration 20] 20. The image forming apparatus according to any one of configurations 1 to 19, wherein the first electrode and the second electrode form the optical resonator structure.

[0246] [Configuration 21] a reflective layer between the substrate and the first electrode; 20. The image-forming apparatus according to any one of Structures 1 to 19, wherein the reflective layer and the second electrode constitute the optical resonator structure.

[0247] [Configuration 22] 20. The image forming apparatus according to any one of configurations 1 to 19, wherein the substrate is a light-opaque substrate.

[0248] [Configuration 23] 20. The image forming apparatus according to any one of configurations 1 to 19, wherein the substrate is a silicon substrate.

[0249] [Configuration 24] 24. The image forming apparatus according to configuration 23, wherein a transistor is provided on the silicon substrate, and the transistor is connected to the organic light-emitting element. [Explanation of symbols]

[0250] 1. Emission spectrum 2. PL Spectrum 3. Optical absorption spectrum of photoreceptor 4. Optical absorption spectrum of the first organic compound layer 5. Optical absorption spectrum of the second organic compound layer 21 First electrode 22 Organic compound layer 23 Second electrode 26 Organic light-emitting devices

Claims

1. an organic light-emitting element having an optical resonator structure on a first surface of a substrate; and a photoreceptor that receives light from the organic light-emitting element; the organic light-emitting element has a first electrode, a light-emitting layer containing a light-emitting material, and a second electrode in this order from the first surface; an emission spectrum of the organic light-emitting element resonated by the optical resonator structure has a maximum peak wavelength in the visible light region that is closer to a wavelength of a maximum absorption value in the visible light region of an absorption spectrum of the photoreceptor than to a maximum peak wavelength in the visible light region of a PL spectrum of the light-emitting material.

2. the organic light-emitting element has a first organic compound layer between the first electrode and a light-emitting layer containing the light-emitting material, and a second organic compound layer between the light-emitting layer and the second electrode, 2. The image forming apparatus according to claim 1, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is closer to the maximum absorption peak wavelength in the visible light region of 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.

3. the organic light-emitting element has a first organic compound layer between the first electrode and a light-emitting layer containing the light-emitting material, and a second organic compound layer between the light-emitting layer and the second electrode, 2. The image forming apparatus according to claim 1, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is closer to the maximum absorption peak wavelength in the visible light region of the light absorption spectrum of the photosensitive member than the longest wavelength peak wavelength in the light absorption spectrum of the first organic compound layer and the longest wavelength peak wavelength in the light absorption spectrum of the second organic compound layer.

4. 3. The image forming apparatus according to claim 2, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from the longest peak wavelength in the light absorption spectrum of the first organic compound layer than from the PL spectrum of the light-emitting material.

5. 3. The image forming apparatus according to claim 2, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from the longest peak wavelength in the light absorption spectrum of the second organic compound layer than from the PL spectrum of the light-emitting material.

6. 4. The image forming apparatus according to claim 3, wherein the maximum emission peak wavelength in the emission spectrum of the organic light-emitting element is farther from 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 than from the PL spectrum of the light-emitting material.

7. the first electrode is a reflective electrode, and the second electrode is a light extraction electrode; 3. The image forming apparatus according to claim 2, wherein the thickness of the second organic compound layer is greater than the thickness of the first organic compound layer.

8. 8. The image forming apparatus according to claim 7, wherein the longest wavelength peak of the light absorption spectrum of the second organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the first organic compound layer.

9. the first electrode is a reflective electrode, and the second electrode is a light extraction electrode; 3. The image forming apparatus according to claim 2, wherein the thickness of the first organic compound layer is greater than the thickness of the second organic compound layer.

10. 10. The image forming apparatus according to claim 9, wherein the longest wavelength peak of the light absorption spectrum of the first organic compound layer is farther from the maximum emission peak wavelength of the emission spectrum than the longest wavelength peak of the light absorption spectrum of the second organic compound layer.

11. 3. The image forming apparatus according to claim 2, further comprising a third organic compound layer between the first organic compound layer and the first electrode.

12. 12. The image forming apparatus according to claim 11, further comprising a fourth organic compound layer between the second organic compound layer and the second electrode.

13. 2. The image forming apparatus according to claim 1, further comprising a first protective layer covering the second electrode, the first protective layer being made of a first inorganic material.

14. 14. The image forming apparatus according to claim 13, further comprising a second protective layer covering the first protective layer, the second protective layer being made of a second inorganic material.

15. 15. The image forming apparatus according to claim 14, further comprising a second protective layer covering the first protective layer, the second protective layer being made of resin.

16. 2. The image forming apparatus according to claim 1, wherein the light-emitting layer comprises at least one of a fluorene derivative, a naphthalene derivative, a pyrene derivative, a perylene derivative, a tetracene derivative, an anthracene derivative, a rubrene derivative, a fluoranthene derivative, a quinacridone derivative, a coumarin derivative, a stilbene derivative, an organoaluminum complex, an iridium complex, a platinum complex, a rhenium complex, a copper complex, a europium complex, a ruthenium complex, a poly(phenylenevinylene) derivative, a poly(fluorene) derivative, and a poly(phenylene) derivative.

17. 2. The image forming apparatus according to claim 1, wherein the photoreceptor comprises at least one of a perylene derivative, an anthraquinone derivative, an anthanthrone derivative, a dibenzpyrenequinone derivative, a pyranthrone derivative, an indigoid derivative, a phthalocyanine derivative, and a perinone derivative.

18. 3. The image-forming apparatus according to claim 2, wherein the first organic compound layer is made of only an arylamine compound.

19. 3. The image forming apparatus according to claim 2, wherein the second organic compound layer is made of only an aromatic hydrocarbon compound.

20. 20. The image forming apparatus according to claim 1, wherein the first electrode and the second electrode form the optical resonator structure.

21. a reflective layer between the substrate and the first electrode; 20. The image forming apparatus according to claim 1, wherein the reflective layer and the second electrode form the optical resonator structure.

22. 20. The image forming apparatus according to claim 1, wherein the substrate is a light-opaque substrate.

23. 20. The image forming apparatus according to claim 1, wherein the substrate is a silicon substrate.

24. 24. The image forming apparatus according to claim 23, wherein a transistor is provided on the silicon substrate, and the transistor is connected to the organic light-emitting element.

Images