JP2012028305A - Organic electroluminescent element, exposure head, cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element in which distortion of a light emission profile is suppressed.SOLUTION: The organic electroluminescent element includes: a cathode 115; an anode 111; a light-emitting layer 114 provided between the cathode 115 and the anode 111; a hole injection layer 112 provided between the anode 111 and the light-emitting layer 114; and an insulating layer 113 which is provided between the cathode 115 and the hole injection layer 112 and has an opening 113A.

Description

  The present invention relates to an organic electroluminescent element, an exposure head, a cartridge, and an image forming apparatus.

  In an organic electroluminescent element, a light-emitting layer containing an organic light-emitting material is provided between electrodes, and by applying a voltage between the electrodes, holes and electrons are injected into the light-emitting layer, and these charges (carriers) recombine. This is a charge injection type light emitting element that emits light.

  For example, Patent Document 1 states that “after the anode electrode, the EL layer, and the metal layer are formed, the focused laser beam is focused while being positioned from the EL layer side boundary surface of the anode electrode to the outer boundary surface of the metal layer. Organic electroluminescence including a cathode electrode forming step of scanning a laser beam to cut at least a part of the EL layer and the metal layer to form a plurality of strip-like EL layers and strip-like cathode electrodes intersecting with the anode electrode in parallel with each other An element manufacturing method "is disclosed.

  Patent Document 2 states that “an upper electrode of a pair of electrodes formed after the formation of an EL light-emitting layer is patterned by an etching method using an etchant containing sulfate ions. The manufacturing method of the light emitting element "is disclosed.

  Patent Document 3 states that “a transparent electrode in which a transparent electrode material is formed in a predetermined pattern on a transparent substrate surface, an insulator in which another predetermined pattern is formed on the transparent electrode, and an organic EL material. An organic EL device comprising: a light emitting layer comprising: a light emitting layer; and a back electrode formed on the light emitting layer so as to face the transparent electrode and separated from each other on the insulator and insulated in a predetermined pattern. ing.

JP 05-003077 A Japanese Patent Laid-Open No. 08-236272 Japanese Patent Laid-Open No. 10-321366

  The subject of this invention is providing the organic electroluminescent element by which distortion of the light emission profile was suppressed compared with the case where a positive hole injection layer is provided in the said opening of the insulating layer which has an opening.

The above problem is solved by the following means. That is,
The invention according to claim 1
A cathode and an anode;
A light emitting layer provided between the cathode and the anode;
A hole injection layer provided between the anode and the light emitting layer;
An insulating layer provided between the cathode and the hole injection layer and having an opening;
An organic electroluminescent device comprising:

The invention according to claim 2
The organic electroluminescence device according to claim 1, wherein the specific resistance of the hole injection layer is 10,000 Ωcm or less.

The invention according to claim 3
The organic electroluminescent device according to claim 1, wherein the hole injection layer comprises 3,4-ethylenedioxy-polythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS).

The invention according to claim 4
The hole injection layer contains one or more of the structures represented by any one of the following general formulas (I-1) and (I-2) as a partial structure of a repeating unit, and the following general formulas (II), ( The organic electroluminescent device according to claim 1 or 2, comprising a charge transporting polymer represented by any one of III), (IV) and (V) and an electron accepting acceptor.

(In the general formulas (I-1) and (I-2), Ar represents a substituted or unsubstituted monovalent aromatic ring, a monovalent polynuclear aromatic ring having 2 to 10 substituted or unsubstituted aromatic rings, Or a substituted or unsubstituted monovalent fused aromatic ring having 2 to 10 aromatic rings, X represents a substituted or unsubstituted divalent aromatic group, k and l are each independently 0 or 1 represents T. T represents a linear divalent hydrocarbon group having 1 to 10 carbon atoms or a branched divalent hydrocarbon group having 1 to 10 carbon atoms.

(In the general formulas (II), (III), (IV) and (V), A represents the general formula (I-1) or (I-2). B represents —O— (Y′—O). ) m _'-, or Z' .Y representing a, Y ', Z, and Z' each independently represents a divalent hydrocarbon group .m, and m ', the 1 to 5 independently Represents an integer, n represents 0 or 1. p represents an integer of 5 to 500. q represents an integer of 1 to 5000. r represents an integer of 1 to 3500.)

The invention according to claim 5
The organic electroluminescent element of any one of Claims 1-4 in which the thickness of the said insulating layer is thinner than the said light emitting layer.

The invention according to claim 6
A light-emitting substrate having a light-emitting portion composed of the organic electroluminescent element according to any one of claims 1 to 5,
An image forming unit that causes light emitted from the light emitting unit to be incident from a light incident surface and emitted from the light emitting surface to form an image at a predetermined position;
An exposure head comprising:

The invention according to claim 7 provides:
An exposure head according to claim 6,
A cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 8 provides:
A latent image holding body for holding the latent image;
An exposure head for forming a latent image by irradiating the latent image holding member with light, wherein the exposure head according to claim 6;
A developing device for developing the latent image formed on the latent image holding member by the exposure head;
An image forming apparatus comprising:

According to the first aspect of the present invention, it is possible to provide an organic electroluminescent device in which the distortion of the light emission profile is suppressed as compared with the case where the hole injection layer is provided in the opening of the insulating layer having the opening.
According to the second, third, and fourth aspects of the invention, even when a hole injection layer having a characteristic or configuration that easily causes distortion of the light emission profile is applied, the hole injection layer is provided in the opening of the insulating layer having an opening. An organic electroluminescent element in which distortion of the light emission profile is suppressed as compared with the case where it is provided can be provided.
According to the invention which concerns on Claim 5, compared with the case where the thickness of an insulating layer is the same as a light emitting layer, the organic electroluminescent element which luminous efficiency improves can be provided.
According to the inventions according to claims 6, 7, and 8, exposure unevenness is suppressed as compared with the case where an organic electroluminescence device in which a hole injection layer is provided in an opening of an insulating layer having an opening is applied. A head, a cartridge, and an image forming apparatus can be provided.

It is a schematic sectional drawing which shows the organic electroluminescent element which concerns on this embodiment. It is a schematic diagram which shows the light emission profile of the organic electroluminescent element which concerns on this embodiment. It is a schematic diagram which shows the light emission profile of the conventional organic electroluminescent element. It is a schematic diagram which shows the light emission profile of another conventional organic electroluminescent element. It is a schematic sectional drawing which shows the organic electroluminescent element which concerns on other this embodiment. It is a schematic sectional drawing which shows the organic electroluminescent element which concerns on other this embodiment. It is a schematic sectional drawing which shows the organic electroluminescent element which concerns on other this embodiment. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment. It is a schematic perspective view which shows the structure of the exposure head which concerns on this embodiment. It is the schematic diagram which showed typically the state in which the light emission from an exposure head image-forms on a photoreceptor.

  Below, an example of an embodiment concerning the present invention is described based on a drawing.

(Organic electroluminescence device)
FIG. 1 is a schematic cross-sectional view showing an organic electroluminescent element according to this embodiment.

  For example, as shown in FIG. 1, the organic electroluminescent device 101 according to the present embodiment includes an anode 111, a hole injection layer 112, an insulating layer 113 having an opening 113 </ b> A, a light emitting layer 114, and a substrate 110. The cathode 115 is constituted by a laminate in which the cathode 115 is laminated in this order.

First, the substrate 110 will be described.
Examples of the substrate 110 include a glass substrate and a plastic film.
The substrate 110 is preferably transparent in the case where the light from the light emitting layer 114 is extracted from the substrate 110 side to the outside of the element. Further, the substrate 110 is preferably insulating.
Here, transparent means that the transmittance of light in the visible region is 10% or more. The insulating property means that the volume resistivity is 10 ¹³ Ωcm or more. The same applies hereinafter.

Next, the anode 111 and the cathode 115 will be described.
The anode 111 and the cathode 115 are electrodes to which a current for injecting holes and electrons into a light emitting layer provided therebetween is applied.

  Of the anode 111 and the cathode 115, when the light emitted from the light emitting layer 114 is extracted from the substrate 110 side to the outside of the element (in the case of the bottom emission method), the anode 111 is preferably transparent and is on the side opposite to the substrate 110. In the case of the method of taking out from the element to the outside (in the case of the top emission method), the cathode 115 is preferably transparent.

  The anode 111 preferably has a work function larger than the ionization potential of the light emitting material contained in the light emitting layer 114 in order to inject holes into the light emitting layer 114. For example, the anode 111 preferably has a work function of 4 eV or more.

The anode 111 is composed of, for example, an oxide film (for example, indium tin oxide (ITO), tin oxide (NESA), indium oxide, zinc oxide, or the like), or a metal film (for example, gold, platinum, or palladium).
The anode 111 is formed using a known method such as a vapor deposition method or a sputtering method.

  On the other hand, the cathode 115 preferably has a work function smaller than the LUMO level of the light emitting layer 114 in order to inject electrons into the light emitting layer 114. For example, the cathode 115 preferably has a work function of 3.0 eV or less.

The cathode 115 is made of, for example, aluminum, silver, indium, or an alloy thereof.
The cathode 115 is formed by using a known method such as a vapor deposition method or a sputtering method.

Next, the hole injection layer 112 will be described.
The hole injection layer 112 is provided between the anode 111 and the light emitting layer 114. Specifically, the hole injection layer 112 is, for example, the area of the region where the anode 111 and the cathode 115 overlap (projected in the thickness direction). Is provided on the substrate 110 so as to cover the anode 111 in a region larger than the area when it is formed (the same applies hereinafter).

The hole injection layer 112 includes a material having a function of injecting holes into the light emitting layer 114. In particular, the hole injection layer 112 preferably has a specific resistance of 10,000 Ωcm or less (preferably 0.01 Ωcm to 1000 Ωcm, more preferably 0.01 Ωcm to 100 Ωcm).
Here, the specific resistance is a value obtained by a four-terminal method.

Examples of the material constituting the hole injection layer 112 and having the function of injecting holes include conductive polymers, transition metal compounds, phthalocyanines (including CuPc), and indanthrene compounds. .
Examples of the conductive polymer include polyaniline, 3,4-ethylenedioxy-polythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS) [hereinafter sometimes referred to as “PEDOT-PSS”] and the like. It is done.
An example of the transition metal compound is molybdenum oxide.
Among these, a conductive polymer is preferable from the viewpoint of realizing the coating formation of the hole injection layer 112, and PEDOT-PSS is particularly preferable from the viewpoint of setting the specific resistance of the hole injection layer 112 in the above range.

  The hole injection layer 112 may include a charge transporting polymer and an electron accepting acceptor.

Examples of the charge transporting polymer include well-known charge transporting polymers, and in particular, one or more of the structures represented by any of the following general formulas (I-1) and (I-2) are repeated. A charge transporting polymer (hereinafter referred to as a specific charge transporting polymer) contained as a partial structure of a unit and represented by any one of the following general formulas (II), (III), (IV) and (V) Is good).
The specific charge transporting polymer is a compound corresponding to a hole transporting polyester or a hole transporting polycarbonate.

  First, the structure represented by either of the following general formulas (I-1) and (I-2) will be described.

In general formulas (I-1) and (I-2), Ar represents a substituted or unsubstituted monovalent aromatic ring, a substituted or unsubstituted monovalent polynuclear aromatic ring having 2 to 10 aromatic rings, or It represents a monovalent fused aromatic ring having 2 or more and 10 or less substituted or unsubstituted aromatic rings.
X represents a substituted or unsubstituted divalent aromatic group.
k and l each independently represents 0 or 1.
T represents a linear divalent hydrocarbon group having 1 to 10 carbon atoms or a branched divalent hydrocarbon group having 1 to 10 carbon atoms.

In general formulas (I-1) and (I-2), Ar represents a substituted or unsubstituted monovalent aromatic ring, a substituted or unsubstituted monovalent polynuclear aromatic ring having 2 to 10 aromatic rings, or A monovalent condensed aromatic ring having 2 or more and 10 or less substituted or unsubstituted aromatic rings is represented, and the polynuclear aromatic ring and the condensed aromatic ring are specifically aromatic hydrocarbons defined below. means.
An “aromatic ring” is an aromatic ring composed of carbon and hydrogen, specifically a phenyl group.
The “polynuclear aromatic ring” represents a hydrocarbon in which two or more aromatic rings composed of carbon and hydrogen are present and the aromatic rings are bonded to each other through a carbon-carbon bond. Specific examples of the “polynuclear aromatic ring” include biphenyl and terphenyl.
The “fused aromatic ring” represents a hydrocarbon in which two or more aromatic rings composed of carbon and hydrogen are present, and the aromatic rings share a pair of carbon atoms. Specific examples of the “fused aromatic ring” include naphthalene, anthracene, phenanthrene and fluorene.

Examples of the substituent of the aromatic ring, polynuclear aromatic ring and condensed aromatic ring include a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, a substituted amino group, and a halogen atom.
As an alkyl group, a C1-C10 thing is desirable, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group etc. are mentioned.
As an alkoxyl group, a C1-C10 thing is desirable, for example, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group etc. are mentioned.
As the aryl group, those having 6 to 20 carbon atoms are desirable, and examples thereof include a phenyl group and a toluyl group.
As the aralkyl group, those having 7 to 20 carbon atoms are desirable, and examples thereof include a benzyl group and a phenethyl group.
Examples of the substituent of the substituted amino group include an alkyl group, an aryl group, an aralkyl group, and the like, and specific examples are as described above.
Examples of the substituent for the substituted aryl group and the substituted aralkyl group include a hydrogen atom, an alkyl group, an alkoxy group, a substituted amino group, and a halogen atom.

  In general formulas (I-1) and (I-2), X represents a substituted or unsubstituted divalent aromatic group, specifically, a group selected from the following formulas (1) to (7): Can be mentioned.

In formulas (1) to (7), R ⁷ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted aralkyl group, and R ^{8 to} R ¹⁴ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group, or a halogen atom. A represents 0 or 1, and V represents a group selected from the following formulas (8) to (17).

  In the above formulas (8) to (17), b represents an integer of 1 to 10, and c represents an integer of 1 to 3.

In general formulas (I-1) and (I-2), T is a linear divalent hydrocarbon group having 1 to 10 carbon atoms or a branched divalent hydrocarbon group having 1 to 10 carbon atoms. Represents a hydrocarbon group.
In addition, when the divalent hydrocarbon group is linear, the carbon number is preferably in the range of 1 to 6, more preferably in the range of 2 to 6, and the divalent hydrocarbon group is branched. In some cases, the carbon number is preferably in the range of 2 to 10, and more preferably in the range of 3 to 7.
Examples of specific structures of the group represented by T (hydrocarbon group T-1 to hydrocarbon group T-32) are shown below.

  Hereinafter, specific examples of the partial structure represented by the general formula (I-1) are shown in Tables 1 to 8, and partial structures represented by the general formula (I-2) are shown in Tables 9 to 16. Although the specific example is shown, it is not necessarily limited to these specific examples.

In Tables 1 to 8, the structure described in the “X” column corresponding to each number described in the “Partial structure” column corresponds to X in the general formula (I-1). The structure described in the “Ar” column corresponds to Ar in the general formula (I-1), and the number described in the “k” column represents k in the general formula (I-1). means. Further, the value described in the column of “T” means T in the general formula (I-1), and is a number (T-1) attached to the structural formula of the hydrocarbon group specifically shown above. Means (T-32).
Moreover, in Tables 1 to 8, the value shown in “Binding position” indicates that the value is bonded to the numerical position described in the benzene ring in the general formula (I-1). Further, in the specific example of the structure represented by the general formula (I-1), when k is 1, the benzene ring in () is bonded to the same position as the benzene ring in which the number is described. Indicates.

In Tables 9 to 16, the structure described in the column “X” corresponding to each number described in the “partial structure” column corresponds to X in the general formula (I-2). , The structure described in the “Ar” column corresponds to Ar in the general formula (I-2), and the number described in the “k” column represents k in the general formula (I-2). means. Moreover, the value described in the column of “T” means T in the general formula (I-2) and corresponds to the compounds of the above general formulas (T-1) to (T-32) showing the same value. To do.
Further, in Tables 9 to 16, the value shown in “Binding position” indicates that the value is bonded to the numerical position described in the benzene ring in the general formula (I-2). Further, in the specific example of the structure represented by the general formula (I-2), when k is 1, the benzene ring in () is bonded to the same position as the benzene ring in which the number is described. Indicates.

  Next, one or more of the structures represented by any of the general formulas (I-1) and (I-2) are contained as a partial structure of the repeating unit, and the following general formulas (II), (III), ( The charge transporting polymer represented by either IV) or (V) will be described.

In general formulas (II), (III), (IV) and (V), A represents general formula (I-1) or (I-2).
B _{is, -O- (Y'-O) m} - represents a _', or Z'.
Y, Y ′, Z, and Z ′ each independently represent a divalent hydrocarbon group.
m and m ′ each independently represents an integer of 1 or more and 5 or less.
n represents 0 or 1.
p represents an integer of 5 or more and 500 or less.
q represents an integer of 1 or more and 5000 or less.
r represents an integer of 1 to 3,500.
The terminal group of the charge transporting polymer represented by any one of the general formulas (II), (III), (IV) and (V) is, for example, a hydrogen atom, a methyl group, an ethyl group, a phenyl group or the like. is there.

  In the general formulas (II), (III), (IV), and (V), Y, Y ′, Z, and Z ′ represent a divalent hydrocarbon group, specifically, the following formulas: The hydrocarbon group represented by (18)-(24) is mentioned.

In the above formulas (18) to (24), d and e represent an integer of 1 to 10, f and g represent 0, 1 or 2, and h and i represent 0 or 1.
R ¹³ and R ¹⁴ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group. Or a halogen atom, and V represents a group selected from the above formulas (8) to (17).

Specific examples of the charge transporting polymer represented by the general formula (II) are shown in Table 17, and specific examples of the charge transporting polymer represented by the general formula (III) are shown in Table 18. It was. Further, specific examples of the charge transporting polymer represented by the general formula (IV) are shown in Table 19, and specific examples of the charge transporting polymer represented by the general formula (V) are shown in Tables 20 to 24. It was shown to.
The charge transporting polymer is not limited to these specific examples.

  The numbers shown in the “Structure” column of “Partial Structure” shown in Tables 17 to 24 are the compounds of the numbers shown in the “Partial Structure” column shown in Tables 1 to 16 above ( In the case where two or more types of numbers are shown, the “structure” corresponding to each number corresponds to the above general formula (I-1) or specific example of the general formula (I-2). The ratio of the compound corresponding to the number shown in the column in the molecule is shown in the “ratio” column of “partial structure”.

Moreover, the structure shown in the column “Y” in Table 17 corresponds to Y in the general formula (II), and the numerical value shown in the column “m” corresponds to m in the general formula (II). The numerical value shown in the column “p” corresponds to p in the general formula (II).
Similarly, the structure shown in the column “Y” in Table 18 corresponds to Y in the general formula (III), and the structure shown in the column “Z” corresponds to Z in the general formula (III). Correspondingly, the numerical value shown in the column “m” corresponds to m in the general formula (III), and the numerical value shown in the column “p” corresponds to p in the general formula (III).

The structure shown in the column “B” in Table 19 corresponds to B in the general formula (IV), and the numerical value shown in the column “n” corresponds to n in the general formula (IV). The numerical value shown in the column “p” corresponds to p in the general formula (IV).
Similarly, the structure shown in the column “Y” in Tables 20 to 24 corresponds to Y in the general formula (V), and the structure shown in the column “Z” is in the general formula (V). The numerical value shown in the column “m” corresponds to m in the general formula (V), and the numerical value shown in the column “q” corresponds to q in the general formula (V). The numerical value shown in the column “r” corresponds to r in the general formula (V).

  Moreover, in the following description, when referring to the compound corresponding to the number X shown in the column of “Compound” shown in Tables 17 to 24, it is referred to as “Exemplary Compound (X)”.

Next, the electron accepting acceptor will be described.
The electron-accepting acceptor is not particularly limited as long as it oxidizes the charge transporting polymer. For example, a metal halide, Lewis acid, arylamine and metal halide or Lewis acid salt can be used. There may be mentioned at least one selected, and these may be used in combination of two or more.

Examples of the metal halide and Lewis acid include compounds represented by FeCl ₃ , AlCl ₃ , SbCl ₅ , AsF ₅ .
Examples of the salt of arylamine and metal halide or Lewis acid include salts represented by the following general formula (A).

In general formula (A), L represents a metal halide or a Lewis acid, and examples thereof include FeCl ₃ , AlCl ₃ , SbCl ₅ , AsF ₅ , and BF ₃ .
X ^- is a halogen ion, for example, fluorine ions, chlorine ions and the like.
Ar ^{11 to} Ar ¹³ are each independently a substituted or unsubstituted monovalent aromatic group having 6 to 30 carbon atoms, or a substituted or unsubstituted monovalent heterocyclic group having 4 to 30 carbon atoms. Represents.

The monovalent aromatic group is preferably an aromatic group having 6 or more carbon atoms, such as an aromatic ring (phenyl group), a polynuclear aromatic ring (eg, biphenyl, terphenyl, etc.), a condensed aromatic ring (eg, naphthalene, anthracene). , Phenanthrene, fluorene, etc.).
The heterocyclic group (a heterocyclic group containing a nitrogen atom (N), an oxygen atom (O), or a sulfur atom (S)) is preferably a heterocyclic group having 4 or more carbon atoms, such as a furyl group or a thienyl group. Group, pyridyl group, pyrazolyl group, isoxazolyl group, isothiazolyl group, imidazolyl group, oxazolyl group, thiazolyl group and the like.
Examples of the substituent for substituting the aromatic group or the heterocyclic group include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, etc.), a nitro group, a cyano group, an alkyl group having 1 to 24 carbon atoms, and 6 carbon atoms. An aryl group having 24 to 24 carbon atoms, an aralkyl group having 7 to 24 carbon atoms, an alkoxy group having 1 to 24 carbon atoms, a mono- or dialkylamino group having 6 to 24 carbon atoms, and an aryl group having 6 to 24 carbon atoms And mono- or diarylamino groups.

  A desirable salt among the salts represented by the general formula (A) includes, but is not limited to, tris (4-bromophenyl) aminium hexachloroantimonate (TBAHA).

  The hole injection layer 112 is, for example, a coating solution containing a material that injects the holes and a solvent that dissolves or disperses the material, or the charge transporting polymer and the electron accepting acceptor and the materials. It is formed by applying a coating solution containing a solvent to be dispersed. Examples of the formation method include spin coating and dipping.

Next, the insulating layer 113 will be described.
The insulating layer 113 is provided, for example, between the hole injection layer 112 and the cathode 115, and specifically, between the hole injection layer 112 and the light emitting layer 114 (excluding the region of the opening 113A of the insulating layer 113). ).
The opening 113A provided in the insulating layer 113 plays a role of defining the light emitting area of the organic electroluminescent element 101 (the area of the light emitting region when viewed from the thickness direction). Provided with an area smaller than the area, specifically, for example, it is preferable to provide the area equal to or smaller than the area of the region where the anode 111 and the cathode 115 overlap.

As the insulating layer 113, for example, the thickness of the insulating layer 113 made of silicon oxide (SiO ₂ ), polyimide, epoxy resin, fluorine resin, or the like is, for example, the thickness of the light emitting layer 114 (however, the thickness here is The thickness is preferably less than 1/2 of the thickness of the light-emitting layer 114, more preferably 1/4 or less.
The insulating layer 113 is formed by, for example, vapor deposition, vapor deposition (CVD), or the like.

Next, the light emitting layer 114 will be described.
The light emitting layer 114 has a thickness larger than the thickness of the insulating layer 113 (here, the thickness is a thickness from the surface of the insulating layer), and a part of the lower layer side portion is embedded in the opening 113A provided in the insulating layer 113. In this manner, the insulating layer 113 and the cathode 115 are provided. The light emitting layer 114 is in contact with the hole injection layer 112 through the opening 113 </ b> A of the insulating layer 113.

  For example, the light emitting layer 114 includes a light emitting material. Examples of the light-emitting material include chelate-type organometallic complexes, polynuclear or condensed aromatic ring compounds, perylene derivatives, coumarin derivatives, styrylarylene derivatives, silole derivatives, oxazole derivatives, oxathiazole derivatives, oxadiazole derivatives, polyparaphenylene derivatives , Polyparaphenylene vinylene derivatives, polythiophene derivatives, or polyacetylene derivatives.

Next, other layers will be described.
The organic electroluminescent device 101 according to the present embodiment includes a hole transport layer between the hole injection layer 112 and the light emitting layer 114, an electron transport layer or an electron injection layer between the light emitting layer 114 and the cathode 115, Further, a layer configuration in which a protective layer (sealing layer) provided to cover the cathode 115 may be provided.
Note that in the case where the hole transport layer is provided, the hole transport layer may be provided so as to be interposed between the hole injection layer 112 and the insulating layer 113, or the hole injection layer 112 and the light emitting layer are formed in the opening 113 A of the insulating layer 113. 114 may be provided so as to be interposed between the two.
However, in the case where the hole transport layer is formed by coating, the hole transport layer is preferably provided so as to be interposed between the hole injection layer 112 and the insulating layer 113.
Specifically, for example, as shown in FIG. 7, in the layer configuration of the organic electroluminescent element 101 according to the present embodiment, the hole transport layer is interposed between the hole injection layer 112 and the insulating layer 113. It is preferable that 112A is provided (an organic electroluminescent element 104 according to another embodiment).

  The organic electroluminescent element 101 described above has a layer structure in which the insulating layer 113 having the opening 113A is provided between the cathode 115 and the hole injection layer 112. With this layer configuration, the distortion of the light emission profile is suppressed.

Here, the organic electroluminescent element 101 is desired to be an element that has high luminous efficiency and does not impose a load on the driving circuit by using a low driving voltage.
For this purpose, the anode 111 and the cathode 115 must efficiently inject holes and electrons into the organic layer including the light emitting layer 114 and move to the light emitting layer.
However, in the element configuration in which the hole injection layer 112 and the light emitting layer 114 are simply laminated between the anode 111 and the cathode 115, the phenomenon that holes diffuse and the light emitting area increases, resulting in light emission. Efficiency tends to be low (see FIG. 3).
This phenomenon has a low specific resistance using a hole injecting material having high conductivity (for example, (eg, PEDOT-PSS, molybdenum oxide)) in order to inject holes into the light emitting layer 114 more efficiently ( For example, when a hole injection layer having a specific resistance of 10,000 Ωcm or less is employed, it tends to occur remarkably.

On the other hand, in order to regulate the diffusion of holes, an insulating layer 113 having an opening 113A is interposed between the anode 111 and the cathode 115, and the hole injection layer 112 and the light emitting layer 114 are stacked in the opening 113A. With such a layer structure, current is supplied only to the region between the anode 111 and the cathode 115 communicated through the opening 113A of the insulating layer 113, so that the injection direction of holes is restricted (that is, diffusion of holes). The holes are efficiently injected into the light emitting layer 114, and as a result, the light emission efficiency is improved (see FIG. 4).
However, with this layer structure, the hole injection layer 112 and the light emitting layer 114 are stacked in the opening 113A of the insulating layer 113, that is, in a state regulated by the inner wall of the opening 113A. A phenomenon in which the thickness of the hole injection layer 112) becomes nonuniform (specifically, for example, a phenomenon in which the thickness is reduced at the central portion of the opening 113A of the insulating layer 113 while the thickness is increased on the inner wall side of the opening 113A) may occur. Become more. If the thickness of the hole injection layer 112 becomes nonuniform, the amount of hole injection into the light emitting layer 114 also becomes nonuniform in the surface, and the light emission profile tends to be distorted (see FIG. 4).
This phenomenon tends to occur remarkably when the hole injection layer 112 is applied and formed using a conductive polymer.

Therefore, in the organic electroluminescent element 101 according to the present embodiment, the layer structure, that is, a lower layer (anode) than the insulating layer 113 having the opening 113A that regulates hole diffusion (that is, regulates the light emitting area of the element). 111), the hole injection layer 112 is provided without being restricted by the opening 113A of the insulating layer 113. Thereby, it is considered that the thickness of the hole injection layer 112 is easily made uniform, and the amount of hole injection into the light emitting layer 114 is also made uniform in the surface, and as a result, distortion in the light emission profile is suppressed ( (See FIG. 2).
In addition, the diffusion of holes is also restricted by the insulating layer 113 having the opening 113A, so that the light emission efficiency is improved and a low driving voltage is realized.

  Moreover, in the organic electroluminescent element 101 according to the present embodiment, as described above, a hole injecting material having high conductivity (for example, (for example, PEDOT-PSS, molybdenum oxide)) for restricting the diffusion of holes. Or a hole injection layer having a low specific resistance (for example, a specific resistance of 10000 Ωcm or less), a conductive polymer (particularly PEDOT-PSS), or a hole injection layer 112 is formed by coating. When this occurs, distortion of the light emission profile is likely to occur, but this is suppressed.

Further, in the organic electroluminescent device 101 according to the present embodiment, as described above, the hole injection layer 112 is configured to include the specific charge transporting polymer and the electron accepting acceptor,
Lower voltage driving is realized.
This is because the conductivity is considered to be improved.

  Moreover, in the organic electroluminescent element 101 according to the present embodiment, the emission efficiency is improved by providing the insulating layer 113 having the opening 113A smaller than the thickness of the light emitting layer 114. This is because the electron injection from the cathode 115 is considered to increase.

The layer structure of the organic electroluminescent element 101 according to this embodiment is not limited to the above structure, and it is only necessary that the insulating layer 113 having an opening is provided between the cathode 115 and the hole injection layer 112. Examples include the following forms.
1) As shown in FIG. 5, the light emitting layer 114 is embedded in the opening 113A of the insulating layer 113 having the opening 113A provided between the cathode 115 and the hole injection layer 112 (another configuration) Organic electroluminescent device 102 according to this embodiment)
2) As shown in FIG. 6, an insulating layer 113 having an opening 113A is provided between the cathode 115 and the light emitting layer 114, and a part of the upper layer side portion of the light emitting layer 114 is embedded in the opening 113A of the insulating layer 113. (Organic electroluminescence device 103 according to another embodiment).

  Even in the above-mentioned forms 1) and 2), distortion is suppressed in the light emission profile for the same reason as described above (see FIG. 2). In addition, the diffusion of holes is also restricted by the insulating layer 113 having the opening 113A, so that the light emission efficiency is improved and a low driving voltage is realized.

  The organic electroluminescent element according to the present embodiment is suitably used in fields such as a display device, electronic paper, a backlight, an illumination light source, an exposure device, a sign, and a signboard. Among these, it is particularly preferable to provide an exposure apparatus (exposure head) for an electrophotographic image forming apparatus that requires high luminous efficiency and low drive voltage.

(Exposure head, cartridge, image forming apparatus)
FIG. 8 is a schematic diagram showing the configuration of the image forming apparatus according to the present embodiment.

  As shown in FIG. 8, the image forming apparatus 10 according to the present embodiment includes a housing 11 that accommodates each component, a recording medium accommodating portion 12 that accommodates a recording medium P such as paper, and a recording medium P. An image forming unit 14 that forms a toner image, a transport unit 16 that transports the recording medium P from the recording medium storage unit 12 to the image forming unit 14, and a toner image formed by the image forming unit 14 is fixed to the recording medium P. The image forming apparatus includes a fixing device 18 and a recording medium discharge unit (not shown) from which the recording medium P on which the toner image is fixed by the fixing device 18 is discharged.

  The recording medium storage unit 12, the image forming unit 14, the transport unit 16, and the fixing device 18 are stored in the housing 11.

  The image forming unit 14 includes image forming units 22C, 22M, 22Y, and 22K that form toner images of cyan (C), magenta (M), yellow (Y), and black (K), and an image forming unit 22C, An intermediate transfer belt 24 as an example of an intermediate transfer body to which toner images formed by 22M, 22Y, and 22K are transferred, and toner images formed by image forming units 22C, 22M, 22Y, and 22K are transferred to the intermediate transfer belt 24. A primary transfer roll 26 as an example of a primary transfer member to be transferred; and a secondary transfer roll 28 as an example of a secondary transfer member for transferring a toner image transferred to the intermediate transfer belt 24 to a recording medium P. Yes.

  Each of the image forming units 22C, 22M, 22Y, and 22K includes a photoreceptor 30 that rotates in one direction (clockwise in FIG. 8) as an example of an image holder that holds a latent image.

  Around each photoconductor 30, a charging device 32 that charges the surface of the photoconductor 30 in order from the upstream side in the rotation direction of the photoconductor 30 and the surface of the charged photoconductor 30 are exposed to expose the surface of the photoconductor 30. An exposure head 34 as an exposure device that forms an electrostatic latent image, a developing device 36 that develops the electrostatic latent image formed on the surface of the photoreceptor 30 to form a toner image, and the toner image is transferred to the intermediate transfer belt 24. And a removing device 40 for removing the toner remaining on the surface of the photoreceptor 30 after being transferred to the surface.

  The photoconductor 30, the charging device 32, the exposure head 34, the developing device 36, and the removing device 40 are accommodated in the image forming units 22C, 22M, 22Y, and 22K and unitized. The image forming units 22 </ b> C, 22 </ b> M, 22 </ b> Y, and 22 </ b> K are process cartridges that are detachably attached to the housing 11 and can be replaced.

  Note that the photosensitive member 30, the charging device 32, the exposure head 34, the developing device 36, and the removing device 40 do not have to be unitized. For example, the image forming unit 22C, 22M, 22Y, and 22K are unitized by being provided with at least the exposure head 34 and the other, for example, at least one of the photoconductor 30, the charging device 32, and the developing device 36. That's fine.

  The intermediate transfer belt 24 is supported by a counter roll 42 facing the secondary transfer roll 28, a drive roll 44, and a support roll 46, and circulates in one direction (counterclockwise in FIG. 8) while being in contact with the photoreceptor 30. To move.

  The primary transfer roll 26 faces the photoconductor 30 with the intermediate transfer belt 24 interposed therebetween. Between the primary transfer roll 26 and the photoconductor 30, a primary transfer position where the toner image on the photoconductor 30 is primarily transferred to the intermediate transfer belt 24 is formed. At this primary transfer position, the primary transfer roll 26 transfers the toner image on the surface of the photoconductor 30 to the intermediate transfer belt 24 by a pressing force and an electrostatic force.

  The secondary transfer roll 28 faces the opposing roll 42 with the intermediate transfer belt 24 interposed therebetween. A secondary transfer position where the toner image on the intermediate transfer belt 24 is secondarily transferred to the recording medium P is formed between the secondary transfer roll 28 and the opposing roll 42. At this secondary transfer position, the secondary transfer roll 28 transfers the toner image on the surface of the intermediate transfer belt 24 to the recording medium P by a pressure contact force and an electrostatic force.

  The transport unit 16 includes a feed roll 50 that feeds the recording medium P accommodated in the recording medium storage unit 12, and a transport roll pair 52 that transports the recording medium P sent by the feed roll 50 to the secondary transfer position. ing.

  The fixing device 18 is disposed downstream in the transport direction from the secondary transfer position, and fixes the toner image transferred at the secondary transfer position to the recording medium P.

  A conveyance belt 54 as an example of a conveyance member that conveys the recording medium P to the fixing device 18 is disposed downstream of the secondary transfer position in the conveyance direction and upstream of the fixing device 18 in the conveyance direction.

  With the above configuration, in the image forming apparatus 10 according to the present embodiment, the recording medium P sent out from the recording medium storage unit 12 is first sent to the secondary transfer position by the transport roll pair 52.

  On the other hand, the toner images of the respective colors formed by the image forming units 22C, 22M, 22Y, and 22K are superimposed on the intermediate transfer belt 24 to form a color image. The color image formed on the intermediate transfer belt 24 is transferred to the recording medium P sent to the secondary transfer position.

  The recording medium P to which the toner image is transferred is conveyed to the fixing device 18, and the transferred toner image is fixed by the fixing device 18. The recording medium P on which the toner image is fixed is discharged to a recording medium discharge unit (not shown). As described above, a series of image forming operations are performed.

  The configuration of the image forming apparatus is not limited to the above-described configuration. For example, a direct transfer type image forming apparatus that does not have an intermediate transfer member may be used, and various configurations may be employed.

Next, the exposure head 34 will be described.
FIG. 9 is a perspective view showing the exposure head according to the present embodiment.

As shown in FIG. 9, each exposure head 34 includes, for example, a light emitting element array 60 (an example of a light emitting substrate) and an imaging unit 70.
The light emitting element array 60 includes, for example, a light emitting unit 60A composed of the light emitting elements 60B and a mounting substrate 61 (corresponding to the substrate 110 in FIG. 1) on which the light emitting elements 60B are mounted.

The light emitting element array 60 and the imaging unit 70 are separated so that the optical distance between the light emitting unit 60A (the light emitting element 60B) and the light incident surface 70A of the imaging unit 70 becomes the working distance of the imaging unit 70. And is held by a holding member (not shown).
Here, the working distance of the imaging unit 70 is a distance from the focal point of the lens used for the imaging unit to the incident surface of the imaging unit.
In the imaging unit 70, the light emitted from the light emitting unit 60A is incident from the light incident surface 70A and emitted from the light emitting surface 70B to form an image at a predetermined position, that is, the light emitted from the light emitting element 60B. By forming an image on the photoconductor 30, the photoconductor 30 is exposed to form a latent image (see FIG. 10).

The light emitting element array 60 will be described.
The light emitting element array 60 is, for example, a so-called bottom emission method in which light emitted from the light emitting unit 60A (light emitting element 60B) is extracted from the mounting substrate 61 side. Of course, a top emission method may be used.

  For example, the light emitting unit 60A includes a group of single light emitting elements 60B. Although not shown, the light emitting elements 60B are arranged linearly (in series) or zigzag along the longitudinal direction of the mounting substrate 61 to constitute the light emitting section 60A. The light emitting portion 60A configured by the group of light emitting elements 60B has a length longer than the image forming area of the photoconductor 30.

The imaging unit 70 will be described.
For example, the imaging unit 70 includes a lens array in which a plurality of rod lenses 71 are arranged. Specifically, for example, a refractive index dispersion type lens array called Selfoc lens array (SLA: Selfoc is a registered trademark of Nippon Sheet Glass Co., Ltd.) may be applied.

In the exposure head 34 according to the present embodiment described above, the organic electroluminescent element according to the present embodiment is applied.
For this reason, in the exposure head according to the present embodiment, the cartridge including the exposure head, and the image forming apparatus, exposure unevenness is suppressed.

  Hereinafter, the present invention will be described by way of examples. In addition, this invention is not limited only by these Examples.

Example 1
As shown below, the organic electroluminescent element having the layer structure shown in FIG. 1 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, PEDOT-PSS (trade name: Baytron AI4083) is applied at a thickness of 60 nm by a spin coating method so as to cover the anode on the glass substrate on which the anode is formed, and a hole injection layer (specific resistance: 1000 Ωcm) was formed.
Next, on the hole injection layer, sputtering is performed with SiO ₂ so that an area where an anode (ITO) formed by patterning in the lower layer overlaps with a cathode to be formed later is opened, and an opening with a thickness of 100 nm is formed. An insulating layer having a thickness was formed.
Next, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is applied by spin coating while the opening is embedded on the insulating layer. Then, a light emitting layer having a thickness (thickness from the surface of the insulating layer) of 80 nm was produced.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 1).

(Example 2)
In Example 1, an organic electroluminescent element was produced in the same manner as in Example 1 except that the thickness of the insulating layer was 40 nm.

(Example 3)
In Example 2, an organic electroluminescent element was produced in the same manner as in Example 2 except that the hole injection layer (specific resistance: 1000 Ωcm) was formed using MoO ₃ instead of PEDOT-PSS.

Example 4
In Example 2, except that the hole injection layer (specific resistance: 17 Ωcm) was formed using PEDOT-PSS (trade name: Baytron PH500P) instead of PEDOT-PSS (trade name: Baytron P AI4083). An organic electroluminescent device was produced in the same manner as in Example 2.

(Example 5)
In Example 2, a hole injection layer (specific resistance: 0.1 Ωcm) was formed using PEDOT-PSS (trade name: Bytron HC V4) instead of PEDOT-PSS (trade name: Baytron P AI4083). Produced an organic electroluminescent element in the same manner as in Example 2.

(Example 6)
As shown below, an organic electroluminescent element having the layer structure shown in FIG. 5 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, PEDOT-PSS (trade name: Baytron P AI4083) is applied at a thickness of 60 nm by a spin coat method so as to cover the anode on the glass substrate on which the anode is formed, and a hole injection layer (specific resistance) : 1000 Ωcm).
Next, on the hole injection layer, sputtering is performed with SiO ₂ so that an area where an anode (ITO) formed by patterning in the lower layer overlaps with a cathode to be formed later is opened, and an opening with a thickness of 100 nm is formed. An insulating layer having a thickness was formed.
Next, on the hole injection layer exposed in the opening of the insulating layer, 1% by mass of the light emitting material represented by the following structural formula (1) (weight average molecular weight Mw≈10 ⁵ ) is embedded so as to embed the opening. A coating solution dissolved in xylene was applied to produce a light emitting layer.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 5).

(Example 7)
As shown below, an organic electroluminescent element having the layer structure shown in FIG. 6 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, PEDOT-PSS (trade name: Baytron P AI4083) is applied at a thickness of 60 nm by a spin coat method so as to cover the anode on the glass substrate on which the anode is formed, and a hole injection layer (specific resistance) : 1000 Ωcm).
Next, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is applied by spin coating on the hole injection layer, and the thickness is 80 nm. A light emitting layer was prepared. Then, a part of the upper layer side portion of the light emitting layer was patterned so that a region where the anode (ITO) and a cathode to be formed later overlap each other was a convex portion (height 30 nm) and the other region was a concave portion.
Next, SiO ₂ was sputtered so that the concave portion was filled on the patterned concave portion of the light emitting layer, and an insulating layer was formed with a thickness of 30 nm. This insulating layer has an opening at the patterned convex portion of the light emitting layer.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially formed on the patterned convex portion of the light emitting layer exposed from the insulating layer 113. Evaporated to form a 180 nm thick cathode patterned with a width of 20 μm.
The organic electroluminescent element was produced by the above operation (see FIG. 6).

(Example 8)
As shown below, the organic electroluminescent element having the layer structure shown in FIG. 1 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, and patterning with a width of 20 μm was performed to form a 150 nm anode.
Next, a charge transporting polymer represented by the following structural formula (2) (exemplary compound (CTP-7): weight average molecular weight Mw = 5. 0 × 10 ⁴ ) was dissolved in 1% by mass monochlorobenzene, and TBAHA (electron-accepting acceptor) represented by the following structural formula (3) was added to the charge transporting polymer so as to be 30% by mass. The coating solution was applied at a thickness of 60 nm by spin coating to form a hole injection layer (specific resistance: 1000 Ωcm).
Next, on the hole injection layer, sputtering is performed with SiO ₂ so that an area where an anode (ITO) formed by patterning in the lower layer overlaps with a cathode to be formed later is opened, and an opening with a thickness of 100 nm is formed. An insulating layer having a thickness was formed.
Next, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is applied by spin coating while the opening is embedded on the insulating layer. Then, a light emitting layer having a thickness (thickness from the surface of the insulating layer) of 80 nm was produced.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 1).

Example 9
In Example 8, instead of the charge transporting polymer represented by the following structural formula (2), the charge transporting polymer represented by the following structural formula (4) (exemplary compound (CTP-109): Mw = 8. An organic electroluminescent element was produced in the same manner as in Example 8 except that 8 × 10 ⁴ ) was used.

(Example 10)
As shown below, an organic electroluminescent element having the layer structure shown in FIG. 7 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, on the glass substrate on which the anode is formed, PEDOT-PSS (trade name: Baytron AI4083) is applied at a thickness of 10 nm by a spin coating method so as to cover the anode, and a hole injection layer (specific resistance: 1000 Ωcm) was formed.
Next, a charge transporting polymer represented by the following structural formula (2) (exemplary compound (CTP-7): weight average molecular weight Mw = 5.0 × 10 ⁴ ) on the hole injection layer is 1% by mass. A coating solution in which TBAHA (electron-accepting acceptor) represented by the following structural formula (3) is added so as to be 30% by mass with respect to the charge transporting polymer dissolved in chlorobenzene is spin-coated at a thickness of 60 nm. The hole transport layer was formed by coating.
Next, on the hole transport layer, sputtering of SiO ₂ is performed so that an area where an anode (ITO) formed by patterning in the lower layer and an anode to be formed later are opened, and an opening with a thickness of 100 nm is formed. An insulating layer having a thickness was formed.
Next, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is applied by spin coating while the opening is embedded on the insulating layer. A light emitting layer having a thickness (thickness from the surface of the insulating layer) of 80 nm was prepared.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 7).

(Comparative Example 1)
As shown below, an organic electroluminescent element having the layer structure shown in FIG. 3 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, PEDOT-PSS (trade name: Baytron P AI4083) is applied at a thickness of 60 nm by a spin coat method so as to cover the anode on the glass substrate on which the anode is formed, and a hole injection layer (specific resistance) : 1000 Ωcm).
Next, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is applied by spin coating on the hole injection layer, and the thickness is 80 nm. A light emitting layer was prepared.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 3).

(Comparative Example 2)
In Comparative Example 1, an organic electroluminescent element was produced in the same manner as in Comparative Example 1 except that MoO ₃ was used instead of PEDOT-PSS to form a hole injection layer (specific resistance: 1000 Ωcm).

(Comparative Example 3)
Comparative Example, except that in Example 2, a hole injection layer (specific resistance: 17 Ωcm) was formed using PEDOT-PSS (trade name: Baytron PH500P) instead of PEDOT-PSS (trade name: Baytron P AI4083). In the same manner as in Example 1, an organic electroluminescent element was produced.

(Comparative Example 4)
In Example 2, a hole injection layer (specific resistance: 0.1 Ωcm) was formed using PEDOT-PSS (trade name: Bytron HC V4) instead of PEDOT-PSS (trade name: Baytron P AI4083). Produced an organic electroluminescent device in the same manner as in Comparative Example 1.

(Comparative Example 5)
As shown below, an organic electroluminescent device having the layer structure shown in FIG. 4 was produced.
First, an ITO (indium tin oxide) layer was formed on a glass substrate, patterned with a width of 20 μm, and an anode with a thickness of 150 nm was formed.
Next, on the glass substrate on which the anode is formed, SiO ₂ is sputtered so that a region where the anode (ITO) formed by patterning and the cathode to be formed later are opened, and the opening is formed with a thickness of 300 nm. An insulating layer having a thickness was formed.
Next, PEDOT-PSS (trade name: Bytron HC V4) was applied at a thickness of 60 nm by spin coating on the anode exposed from the opening of the insulating layer to form a hole injection layer (specific resistance: 1000 Ωcm). .
Next, on the hole injection layer exposed from the opening of the insulating layer, a coating solution in which 1% by mass of a light emitting material (weight average molecular weight Mw≈10 ⁵ ) represented by the following structural formula (1) is dissolved in xylene is spin-coated. The light emitting layer with a thickness of 80 nm was produced by coating by the method.
Next, using a mask having an opening pattern with a width of 20 μm formed so as to intersect with the patterned anode, a Ca layer and an Al layer are sequentially deposited on the light emitting layer, and patterned with a width of 20 μm and having a thickness of 180 nm. A cathode was formed.
The organic electroluminescent element was produced by the above operation (see FIG. 4).

(Evaluation)
With respect to the organic electroluminescent element produced in each example, the luminous efficiency and the luminous profile were examined.

-Luminous efficiency-
Evaluation of luminous efficiency was performed by measuring the current luminous efficiency (relative value) as follows.
The current density-luminescence luminance was measured, and the luminous efficiency at a constant luminance was calculated.

-Light emission profile-
The light emission profile was evaluated by measuring the width of the light emitting part.
The emission profile was measured with a CCD (Charge Coupled Device) camera, and the width was calculated.
In addition, it means that there are few distortions in a light emission profile, so that the half value width of a light emission part is near to the electrode width.

  From the above results, it can be seen that in this example, the light emission profile is good as well as the light emission efficiency as compared with the comparative example.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Housing | casing 12 Recording medium accommodating part 14 Image forming part 16 Conveying part 18 Fixing apparatus 22k, 22Y, 22M, 22C Image forming unit 24 Intermediate transfer belt 26 Primary transfer roll 28 Secondary transfer roll 30 Photoconductor 32 Charging Device 34 Exposure head 36 Developing device 40 Removal device 42 Opposite roll 44 Drive roll 46 Support roll 50 Sending roll 52 Transport roll pair 54 Transport belt 60 Light emitting element array 60A Light emitting element 60B Light emitting element 61 Mounting substrate 70 Image forming part 70B Image forming part Light exit surface 70A of the image forming portion Light entrance surface 71 Rod lens

Claims (8)

A cathode and an anode;
A light emitting layer provided between the cathode and the anode;
A hole injection layer provided between the anode and the light emitting layer;
An insulating layer provided between the cathode and the hole injection layer and having an opening;
An organic electroluminescent device comprising:   The organic electroluminescence device according to claim 1, wherein the specific resistance of the hole injection layer is 10,000 Ωcm or less.   The organic electroluminescent device according to claim 1, wherein the hole injection layer comprises 3,4-ethylenedioxy-polythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS). The hole injection layer contains one or more of the structures represented by any of the following general formulas (I-1) and (I-2) as a partial structure of a repeating unit, and the following general formula (II), The organic electroluminescent element according to claim 1 or 2, comprising a charge transporting polymer represented by any one of (III), (IV) and (V), and an electron accepting acceptor.

(In the general formulas (I-1) and (I-2), Ar represents a substituted or unsubstituted monovalent aromatic ring, a monovalent polynuclear aromatic ring having 2 to 10 substituted or unsubstituted aromatic rings, Or a substituted or unsubstituted monovalent fused aromatic ring having 2 to 10 aromatic rings, X represents a substituted or unsubstituted divalent aromatic group, k and l are each independently 0 or T represents a linear divalent hydrocarbon group having 1 to 10 carbon atoms or a branched divalent hydrocarbon group having 1 to 10 carbon atoms.

(In the general formulas (II), (III), (IV) and (V), A represents the general formula (I-1) or (I-2). B represents —O— (Y′—O). ) m _'-, or Z' .Y representing a, Y ', Z, and Z' each independently represents a divalent hydrocarbon group .m, and m ', the 1 to 5 independently Represents an integer, n represents 0 or 1. p represents an integer of 5 to 500. q represents an integer of 1 to 5000. r represents an integer of 1 to 3500.)   The organic electroluminescent element of any one of Claims 1-4 in which the thickness of the said insulating layer is thinner than the said light emitting layer. A light-emitting unit composed of the organic electroluminescent element according to any one of claims 1 to 5,
An image forming unit that causes light emitted from the light emitting unit to be incident from a light incident surface and emitted from the light emitting surface to form an image at a predetermined position;
An exposure head comprising: An exposure head according to claim 6,
A cartridge to be attached to and detached from the image forming apparatus. A latent image holding body for holding the latent image;
An exposure head for forming a latent image by irradiating the latent image holding member with light, wherein the exposure head according to claim 6;
A developing device for developing the latent image formed on the latent image holding member by the exposure head;
An image forming apparatus comprising: