JP2006044090A - Line head, manufacturing method thereof, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for eliminating periodic light amount unevenness of an SL array and to provide an image forming apparatus provided with this line head.
A line head is configured to irradiate a portion to be exposed with light through a lens array in which lens elements are arranged to expose the portion. A plurality of EL elements 3 each having a functional layer (light emitting layer 60) that emits light and emitting light from the functional layer toward the lens array are arranged on the substrate 2 to form a light emitting element array. . In the light emitting element row, the EL element 3 corresponding to the portion where the light amount guided by the lens array is small so as to correct the unevenness of the light amount of the lens array, the thickness of the light emitting layer 60 is thin, and the portion where the light amount guided by the lens array is large. For the EL element 3 corresponding to the above, the thickness of the functional layer of each EL element 3 is changed so that the thickness of the light emitting layer 60 is increased.
[Selection] Figure 3

Description

  The present invention relates to a line head used as exposure means in an image forming apparatus, a method for manufacturing the same, and an image forming apparatus including the line head.

  A line printer (image forming apparatus) is known as an electrophotographic printer. In this line printer, devices such as a charger, a line-shaped printer head (line head), a developing device, and a transfer device are arranged close to each other on the peripheral surface of a photosensitive drum serving as an exposed portion. That is, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum charged by the charger by selective light emission operation of a light emitting element provided in the printer head, and this latent image is formed. It is developed with toner supplied from a developing device, and the toner image is transferred onto a sheet by a transfer device.

  Incidentally, a light emitting diode or the like is generally used as the light emitting element of the printer head as described above. However, this has a problem that it is extremely difficult to arrange thousands of light emitting points with high accuracy. Therefore, in recent years, there has been proposed an image forming apparatus that includes, as an exposure unit, a light-emitting element array that uses an organic electroluminescent element (organic EL element) that can be accurately formed as a light-emitting element as a light-emitting element (for example, Patent Documents). 1).

  Further, in the electrophotographic line printer as described above, the radiated light from the printer head (line head) is usually applied to the SELFOC (registered trademark) lens array (trade name of Nippon Sheet Glass; hereinafter referred to as SELFOC (registered trademark)). A system in which an image is formed on a photosensitive drum by passing through a lens (SL) and a SELFOC (registered trademark) lens array is referred to as an SL array) is exposed. The SL array is a cylindrical lens element, and allows a wide range of images to be formed by arranging a large number of SL elements for erecting an equal magnification.

By the way, an image formed by the SL array is formed by overlapping images formed by one SL element, and the SL element has a light quantity distribution as if football is halved. Therefore, in the SL array, periodic unevenness in the amount of light occurs with the arrangement pitch of each SL element.
However, if there is such a periodic unevenness of the light amount, when the printer head (line head) and the SL array are combined, the light intensity in the main scanning direction becomes uniform due to the uneven light amount of the SL array. The print quality obtained by the deterioration of the exposure and the exposure accuracy is deteriorated.

Against this background, a technique has been proposed in which the thickness of the light emitting layer of the edge light emitting element is changed so as to eliminate unevenness in the light intensity period of the SL array, particularly when the edge light emitting element and the SL array are combined. (For example, refer to Patent Document 2).
JP 11-198433 A JP-A-5-330135

  However, in the case of a printer head (line head) having a general EL element that emits light from the substrate surface, such as bottom emission type or top emission type, instead of edge emission, the periodic light intensity unevenness of the SL array is eliminated. Such a technology has not been established, and therefore it is desired to provide such a technology.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for eliminating the periodic light amount unevenness of the SL array in a line head including a general EL element. An object of the present invention is to provide an image forming apparatus provided with a line head.

A line head according to the present invention is a line head configured to irradiate light to an exposed portion through a lens array in which lens elements are arranged, and to expose the portion.
A plurality of EL elements having a functional layer that emits light and emitting light from the functional layer toward the lens array to form a light emitting element array;
In the light emitting element array, the thickness of the functional layer is reduced for the EL element corresponding to the portion where the light amount guided by the lens array is small so that the light amount unevenness of the lens array is corrected. The EL element corresponding to many parts is characterized in that the thickness of the functional layer of each EL element is changed so that the thickness of the functional layer is increased.

A functional layer in an EL element, particularly a light emitting layer, usually has a relatively high electric resistance. Therefore, in the EL element, when the thickness of the functional layer (light emitting layer) is reduced, the value of current flowing through the functional layer is increased, and the light emission intensity (light emission amount) is increased (increased) accordingly. On the contrary, when the film thickness of the functional layer (light emitting layer) is increased, the value of current flowing through the functional layer is decreased, and the light emission intensity (light emission amount) is decreased (reduced) accordingly.
Therefore, according to this line head, since the film thickness of the functional layer of the EL elements forming the light emitting element array is changed corresponding to the part of the lens array (SL array), the light emission intensity of each EL element. (Light emission amount) changes, and it is possible to correct this by eliminating the periodic light amount unevenness of the lens array, and therefore it is possible to prevent exposure unevenness due to light amount unevenness, and further printing unevenness. become.

Further, in the line head, the functional layer includes at least an organic light emitting layer and a hole transport layer, and by changing the film thickness of the organic light emitting layer between the EL elements, It is preferable to change the thickness of the functional layer.
Thus, if the film thickness of the organic light emitting layer is changed between the EL elements by changing the film thickness of the light emitting layer having a relatively high electrical resistance, the light emission intensity of each EL element is changed by the change in the film thickness. The (light emission amount) changes more easily and reliably. Therefore, as described above, it is possible to eliminate the periodic light amount unevenness of the lens array and correct it, and therefore it is possible to prevent the exposure unevenness due to the light amount unevenness and the printing unevenness.

The method of manufacturing a line head according to the present invention includes a plurality of EL elements on a substrate, each having a functional layer that emits light, and emitting light toward a lens array in which lens elements are arranged from the functional layer. A method of manufacturing a line head by arranging a light emitting element array, comprising:
Forming a functional layer forming portion surrounded by a partition wall in each EL element forming region on the substrate;
Providing a functional layer material in the functional layer forming portion by a droplet discharge method and forming a functional layer,
In the step of forming the functional layer, in order to correct unevenness of the light amount of the lens array, the thickness of the functional layer is reduced at a portion where the light amount guided by the lens array is small, and the portion where the light amount guided by the lens array is large Is characterized in that the thickness of the functional layer is increased.

  According to this line head manufacturing method, the functional layer material is formed by the droplet discharge method so that the functional layer material is formed. Therefore, a desired amount of the functional layer material is accurately obtained for each functional layer forming portion. Therefore, the thickness of each functional layer can be adjusted accurately and easily to a preset thickness. Therefore, it is possible to reliably eliminate the periodic light amount unevenness of the lens array and correct it.

The image forming apparatus of the present invention is characterized in that the above-mentioned line head or the line head obtained by the above-described manufacturing method is provided as an exposure unit.
According to this image forming apparatus, as described above, the line head changes the film thickness of the functional layer in the EL element forming the light emitting element array corresponding to the part of the lens array (SL array). It is possible to eliminate the periodic light amount unevenness of the array and correct it, and therefore it is possible to prevent the exposure unevenness due to the light amount unevenness and the printing unevenness.

The present invention will be described in detail below.
First, the line head of the present invention will be described. FIG. 1 is a diagram schematically showing an embodiment of a line head according to the present invention, and reference numeral 1 in FIG. 1 denotes a line head. This line head 1 is used as an exposure unit of an image forming apparatus described later. As shown in FIG. 1, a plurality of organic EL (electroluminescence) elements 3 are arranged on a long and thin rectangular element substrate 2. A light emitting element array 3A, a driving element group including driving elements 4 for driving the organic EL elements 3, and a control circuit group 5 for controlling the driving of these driving elements 4 (driving element groups). It is. Further, a sealing substrate (not shown) is stuck on the element substrate 2 with an adhesive in a state where the organic EL element 3 is sealed.

  Here, as will be described later, each EL element 3 forming the light emitting element array 3A is a functional layer formed in a functional layer forming portion (opening 25a, opening 221a) surrounded by the inorganic partition wall 25 and the organic partition wall 221. The film thicknesses of the EL elements 3 are different from each other in accordance with the unevenness of the amount of light of an SL array (lens array), which will be described later. For example, when the light intensity unevenness of the SL array is ± 5% with respect to the average value, the intensity (light emission amount) of the emitted light is changed by changing the film thickness of the functional layer of each organic EL element 3. The average value is ± 5%.

  As shown in FIG. 1, power lines 7 and 8 are connected to the drive element 4, and a voltage is applied to the drive element 4 from a power source (not shown) via these power lines 7 and 8. It has become so. The drive element 4 (drive element group), the control circuit group 5, and the power supply lines 7 and 8 constitute drive control means. Based on such a configuration, the light emitting operation of the organic EL element 3 is controlled by the drive control means.

The configurations of the organic EL element 3 and the driving element 4 in the line head 1 will be described in detail with reference to FIGS. 2 (a) and 2 (b).
As the element substrate 2, as shown in FIG. 2A, in the case of a so-called bottom emission type in which the light emitted from the light emitting layer 60 is emitted from the pixel electrode 23 side, the emitted light is extracted from the element substrate 2 side. Therefore, a transparent or translucent material is used. For example, glass, quartz, resin (plastic, plastic film) and the like can be mentioned, and a glass substrate is particularly preferably used.

In the case of a so-called top emission type in which the light emitted from the light emitting layer 60 is emitted from the cathode (counter electrode) 50 side, the emitted light is extracted from the sealing substrate side that is the opposite side of the element substrate 2. Therefore, either a transparent substrate or an opaque substrate can be used. Examples of the opaque substrate include a thermosetting resin and a thermoplastic resin in addition to a ceramic sheet such as alumina and a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation.
In the present embodiment, a bottom emission type is adopted, and therefore transparent glass is used for the element substrate 2.

  On the element substrate 2, a circuit unit 11 including a driving TFT 123 (driving element 4) connected to the pixel electrode 23 is formed, and an organic EL element 3 is provided thereon. The organic EL element 3 includes a pixel electrode 23 functioning as an anode, a hole transport layer 70 for injecting / transporting holes from the pixel electrode 23, a light emitting layer 60 made of an organic EL material, and a cathode 50 in this order. It is configured by being formed. In the present embodiment, the hole transport layer 70 and the light emitting layer 60 form the functional layer of the present invention.

Here, when the organic EL element 3 and the driving TFT 123 (driving element 4) are shown in a schematic view corresponding to FIG. 1, it is as shown in FIG. In FIG. 2B, the power line 7 is connected to the source / drain electrode of the drive element 4, and the power line 8 is connected to the cathode 50 of the organic EL element 3.
In the organic EL element 3 having such a configuration, the holes injected from the hole transport layer 70 and the electrons from the cathode 50 are combined in the light emitting layer 60 as shown in FIG. By doing so, it emits light. Therefore, the organic EL element 3 has a low electric resistance of the functional layer composed of the hole transport layer 70 and the light emitting layer 60, and an increase in the amount of light emission and an increase in the light emission intensity due to an increase in current flowing in the functional layer. On the contrary, the electrical resistance of the functional layer is high and the current flowing in the functional layer is reduced, so that the light emission amount is reduced and the light emission intensity is weakened.

Further, in the present invention, as described above, each organic EL element 3 is formed such that the thickness of each functional layer is different corresponding to the unevenness of the light amount of the SL array (lens array) described later. That is, in the present embodiment, an inorganic partition wall 25 (partition wall in the present invention) made of a lyophilic insulating material such as SiO ₂ is formed on the pixel electrode 23, and the inorganic partition wall 25 is made of an insulating material. An organic partition 221 is formed. The functional layer forming portion in the present invention is formed by the inorganic partition wall 25, the opening 25 a of the inorganic partition wall 25 that is a region surrounded by the organic partition wall 221, and the opening 221 a of the organic partition wall 221.
The functional layer formed in the functional layer forming portion is composed of the hole transport layer 70 and the light emitting layer 60 as described above. In this embodiment, in particular, the film thickness of the light emitting layer 60 is periodically changed between the arranged organic EL elements 3, and the film thickness of the hole transport layer 70 is made constant, so that the film of the functional layer is formed. The thickness is periodically changed between the arranged organic EL elements 3.

The pixel electrode 23 that functions as an anode is formed of a transparent conductive material, particularly in the case of a bottom emission type, and specifically, ITO is preferably used.
As a material for forming the hole transport layer 70, in particular, a dispersion of 3,4-polyethylenediosithiophene / polystyrene sulfonic acid (PEDOT / PSS), that is, 3,4-polyethylenedioxy in polystyrene sulfonic acid as a dispersion medium. A dispersion in which thiophene is dispersed and further dispersed in water is preferably used.
In addition, as a forming material of the positive hole transport layer 70, various things can be used, without being limited to the said thing. For example, a material obtained by dispersing polystyrene, polypyrrole, polyaniline, polyacetylene or a derivative thereof in an appropriate dispersion medium such as the aforementioned polystyrene sulfonic acid can be used.

  As a material for forming the light emitting layer 60, a known light emitting material capable of emitting fluorescence or phosphorescence is used. In this embodiment, for example, a light emitting layer whose emission wavelength band corresponds to red is adopted, but of course, a light emission layer whose emission wavelength band corresponds to green or blue may be adopted.

  Specific examples of the material for forming the light emitting layer 60 include (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), and polyvinylcarbazole (PVK). ), Polythiophene derivatives, and polysilanes such as polymethylphenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as.

  Here, the hole transport layer 70 obtained from the PEDOT / PSS has a sufficiently low electric resistance and high conductivity as compared with the light emitting layer 60 made of, for example, the (poly) fluorene derivative. . Therefore, when the electrical resistance of the entire functional layer is considered, the influence of the change in the thickness of the hole transport layer 70 on the electrical resistance of the entire functional layer is small enough to be ignored. Therefore, in the present embodiment, as described above, the film thickness of the hole transport layer 70 is kept constant, and the film thickness of the functional layer is arranged by periodically changing the film thickness of the light emitting layer 60. The period is changed periodically between the organic EL elements 3. Specifically, by periodically changing the film thickness of the light emitting layer 60 in a range of about 80 nm ± 10 nm, the intensity of emitted light (light emission amount) is set to ± 5% with respect to the average value. ing.

  However, the thickness of the functional layer is changed in the present invention in order to change the light emission amount between the organic EL elements 3 in order to correct the unevenness of the light amount of the lens array as will be described later. Therefore, in order to change the electrical resistance of the functional layer in order to change the amount of light emission between the organic EL elements 3, it is not always necessary to change the film thickness of the entire functional layer. The thickness of the entire functional layer may be constant as long as only the thickness of the light-emitting layer 60 is changed. Even in such a case, the range of “the film thickness of the functional layer of each EL element was changed so as to correct the unevenness of the light amount of the lens array (SL array)” as defined in the present invention. It will be inside. That is, in the present invention, for example, between the functional layers of each organic EL element 3, the film thickness of the light emitting layer 60 is periodically changed within a predetermined range, and the film thickness of the hole transport layer 70 is also periodically changed. Alternatively, the total thickness of the light emitting layer 60 and the hole transport layer 70, that is, the thickness of the functional layer may be constant.

  Note that the hole transport layer 70 may be close to insulating depending on the material, and the electrical resistance of the film may be increased. In such a case, the thickness of the light emitting layer 60 is made constant, and the thickness of the hole transport layer having a high electrical resistance is periodically changed, whereby the resistance of the functional layer is reduced between the organic EL elements 3. The light emission intensity (light emission amount) may be changed periodically.

The cathode 50 is formed so as to cover the light emitting layer 60. For example, Ca is formed to a thickness of about 20 nm, and Al is formed thereon to a thickness of about 200 nm to form an electrode having a laminated structure, and the Al is reflected. It also functions as a layer.
Further, a sealing substrate (not shown) is stuck on the cathode 50 via an adhesive layer.

In addition, the circuit unit 11 is provided below the organic EL element 3 as described above. The circuit unit 11 is formed on the element substrate 2. That is, a base protective layer 281 mainly composed of SiO ₂ is formed on the surface of the element substrate 2 as a base, and a silicon layer 241 is formed thereon. A gate insulating layer 282 mainly composed of SiO ₂ and / or SiN is formed on the surface of the silicon layer 241.

In the silicon layer 241, a region overlapping with the gate electrode 242 with the gate insulating layer 282 interposed therebetween is a channel region 241a. The gate electrode 242 is a part of a scanning line (not shown). On the other hand, a first interlayer insulating layer 283 mainly composed of SiO ₂ is formed on the surface of the gate insulating layer 282 that covers the silicon layer 241 and on which the gate electrode 242 is formed.

  Further, in the silicon layer 241, a low concentration source region 241b and a high concentration source region 241S are provided on the source side of the channel region 241a, while a low concentration drain region 241c and a high concentration drain are provided on the drain side of the channel region 241a. The region 241D is provided to form a so-called LDD (Light Doped Drain) structure. Among these, the high-concentration source region 241S is connected to the source electrode 243 through a contact hole 243a that opens over the gate insulating layer 282 and the first interlayer insulating layer 283. The source electrode 243 is configured as a part of a power supply line (not shown). On the other hand, the high-concentration drain region 241D is connected to the drain electrode 244 made of the same layer as the source electrode 243 through a contact hole 244a that opens through the gate insulating layer 282 and the first interlayer insulating layer 283.

  On the first interlayer insulating layer 283 on which the source electrode 243 and the drain electrode 244 are formed, for example, a planarizing film 284 mainly composed of an acrylic resin component is formed. The planarizing film 284 is formed of a heat-resistant insulating resin such as acrylic or polyimide, and has surface irregularities caused by the driving TFT 123 (driving element 4), the source electrode 243, the drain electrode 244, and the like. It is a well-known thing formed in order to eliminate.

  A pixel electrode 23 made of ITO or the like is formed on the surface of the planarizing film 284 and connected to the drain electrode 244 through a contact hole 23a provided in the planarizing film 284. That is, the pixel electrode 23 is connected to the high concentration drain region 241D of the silicon layer 241 through the drain electrode 244.

  On the surface of the planarization film 284 on which the pixel electrode 23 is formed, the pixel electrode 23 and the above-described inorganic partition wall 25 are formed, and on the inorganic partition wall 25, an organic partition wall 221 is formed. On the pixel electrode 23, the hole transport layer 70 and the light emitting layer 60 are formed inside the opening 25 a formed in the inorganic partition wall 25 and the opening 221 a formed in the organic partition wall 221, that is, in the pixel region. Are stacked in this order from the pixel electrode 23 side, thereby forming a functional layer.

Next, an example of a method for manufacturing the line head 1 having such a configuration will be described.
First, as shown in FIG. 3A, a base protective layer 281 is formed on the surface of the element substrate 2, and a polysilicon layer or the like is further formed on the base protective layer 281. The circuit unit 11 is formed.
Next, a transparent conductive film to be the pixel electrode 23 is formed of ITO or the like so as to cover the entire surface of the element substrate 2. Then, by patterning this conductive film, the pixel electrode 23 that is electrically connected to the drain electrode 244 through the contact hole 23a of the planarizing film 284 is formed.

Next, an insulating material such as SiO ₂ is formed on the pixel electrode 23 and the planarizing film 284 by a CVD method or the like to form a partition layer (not shown) of the present invention, followed by known photolithography. The barrier rib layer is patterned using a technique and an etching technique. As a result, as shown in FIG. 3B, an opening 25a is formed for each pixel region of each organic EL element 3 to be formed, and at the same time, an inorganic partition wall 25 is formed.
Next, as shown in FIG. 3C, an organic partition 221 having an opening 221a is formed with a resin or the like at a predetermined position of the inorganic partition 25, specifically, a position surrounding the pixel region. As a result, a functional layer forming portion including the opening 25 a of the inorganic partition wall 25 and the opening 221 a of the organic partition wall 221 can be formed.

  Next, a region showing lyophilicity and a region showing liquid repellency are formed on the surface of the element substrate 2. In the present embodiment, each region is formed by plasma processing. Specifically, the plasma treatment includes a preheating step, a lyophilic step for making the surface of the organic partition wall 221 and the wall surface of the opening 221a, the electrode surface 23c of the pixel electrode 23, and the surface of the inorganic partition wall 25 lyophilic. The liquid barrier layer 221 includes a liquid repellent process for making the upper surface of the organic partition wall 221 and the wall surface of the opening 221a liquid repellent, and a cooling process.

That is, the base material (element substrate 2 including a bank or the like) is heated to a predetermined temperature, for example, about 70 to 80 ° C., and then plasma treatment using oxygen as a reaction gas under atmospheric pressure as a lyophilic process (O ₂ plasma treatment). I do. Next, a plasma treatment (CF ₄ plasma treatment) using methane tetrafluoride as a reaction gas under atmospheric pressure as a lyophobic process is performed, and then the substrate heated for the plasma treatment is cooled to room temperature. The lyophilic property and the liquid repellency are imparted to a predetermined location.

In this CF ₄ plasma treatment, the electrode surface 23c of the pixel electrode 23 and the inorganic partition wall 25 are also somewhat affected, but ITO that is the material of the pixel electrode 23 and SiO ₂ that is the constituent material of the inorganic partition wall 25, Since TiO _{2 and the} like have a poor affinity for fluorine, the hydroxyl group imparted in the lyophilic step is not substituted with the fluorine group, and the lyophilic property is maintained.

Next, the hole transport layer 70 is formed by a hole transport layer forming step. In this hole transport layer forming step, an inkjet method is particularly preferably employed as the droplet discharge method. That is, by this ink jet method, the hole transport layer forming material is selectively disposed on the electrode surface 23c and applied. As a material for forming the hole transport layer 70, for example, a material obtained by dissolving the PEDOT: PSS in a polar solvent such as isopropyl alcohol is used.
Thereafter, drying treatment and heat treatment are performed to form the hole transport layer 70 on the electrode 23.

  Here, in forming the hole transport layer 70 by the ink jet method, first, the ink jet head (not shown) is filled with a hole transport layer forming material, and the discharge nozzle of the ink jet head is formed in the inorganic partition wall 25. Opposite the electrode surface 23c located in the opening 25a, and moving the ink jet head and the base material (element substrate 2) relative to each other, droplets with a controlled liquid amount per droplet from the discharge nozzle are applied to the electrode surface 23c. Discharge. Next, the discharged liquid droplets are dried, and the hole transport layer 70 is formed as described above by evaporating the dispersion medium and the solvent contained in the hole transport layer material.

  At this time, the droplet discharged from the discharge nozzle spreads on the electrode surface 23c that has been subjected to the lyophilic treatment, fills the opening 25a of the inorganic partition wall 25, and faces the opening 25a. On the other hand, droplets are repelled and do not adhere to the upper surface of the organic barrier 221 that has been subjected to the liquid repellent treatment. Therefore, even if the liquid droplet is displaced from a predetermined discharge position and a part of the liquid droplet is applied to the surface of the organic partition wall 221, the surface is not wetted by the liquid droplet, and the repelled liquid droplet is the inorganic partition wall 25. Into the opening 25a.

In the present embodiment, the hole transport layer to be formed is formed by arranging the same amount of the hole transport layer forming material in all the pixel regions for forming the organic EL element 3, that is, the functional layer forming part. All the layers 70 have the same film thickness. However, as described above, the hole transport layer 70 has a low electrical resistance. Therefore, the variation in the film thickness of the hole transport layer 70 between the organic EL elements 3 is the resistance of the entire functional layer between the organic EL elements 3. Has little effect on the variation of Therefore, the thickness of the hole transport layer 70 is not necessarily constant between the organic EL elements 3.
Further, after this hole transport layer forming step, it is preferable to carry out in an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere in order to prevent oxidation and moisture absorption of various forming materials and formed elements.

  Next, as shown in FIG. 4A, the light emitting layer 60 is formed by the light emitting layer forming step. In the light emitting layer forming step, as in the formation of the hole transport layer 70, an ink jet method which is a droplet discharge method is suitably employed. That is, the light emitting layer forming material is ejected onto the hole transport layer 70 by an ink jet method, and then subjected to a drying process and a heat treatment, whereby the light emitting layer is formed in the opening 221a formed in the organic partition 221, that is, on the pixel region. 60 is formed.

Here, as described above, the light emitting layer 60 to be formed is formed with a different film thickness for each organic EL element 3, that is, for each pixel region, corresponding to unevenness of the light amount of the SL array (lens array). At that time, since the light emitting layer 60 is formed by arranging the light emitting layer forming material by the ink jet method (droplet discharge method) as described above, it is desired for each functional layer forming portion of each organic EL element 3. The amount of the light emitting layer forming material can be accurately arranged. Therefore, the film thickness of each light emitting layer 60 can be adjusted accurately and easily to a preset film thickness. The difference in film thickness for each organic EL element 3 will be described in detail in the description of the SL array described later.
The functional layer in the present invention can be formed by the formation process of the hole transport layer 70 and the formation process of the light emitting layer 60 described above.

  Next, as shown in FIG. 4B, a cathode 50 is formed by a cathode layer forming step. The cathode 50 generally employs a laminated structure such as an electron injection layer and a conductive layer in order to cause the EL element to emit light efficiently. For example, a metal material such as aluminum can be used. Unlike the formation of the hole transport layer 70 and the light emitting layer 6, the formation of the cathode 50 is performed by vapor deposition or sputtering, so that the formation material is not selectively disposed only in the pixel region. The forming material is provided on almost the entire surface of the element substrate 2. Therefore, in the present embodiment, the element substrate 2 and a metal mask (not shown) are aligned, and the cathode 50 is formed by vapor deposition or sputtering, so that the cathode is formed around the substrate as shown in FIG. 50 is not formed.

  Thereafter, as shown in FIG. 4C, the sealing substrate 30 is bonded by a sealing process. In this sealing step, a transparent adhesive 40 is applied between the transparent sealing substrate 30 and the element substrate 2, and the sealing substrate 30 and the element substrate 2 are bonded to each other so that bubbles do not enter.

Next, the usage pattern of the line head 1 obtained in this way will be described.
FIG. 5 is a diagram showing a usage pattern of the line head 1 in the image forming apparatus described later. As shown in FIG. 5, the line head 1 irradiates light to the photosensitive drum 32 that is an exposed portion in the present invention through the SL array 31 as the lens array in the present invention, forms an image, and exposes it. It is a thing. Here, the line head 1 and the SL array 31 are assembled together in a head case (not shown). At that time, alignment between these is performed, and the periodic unevenness of the light amount of the SL array 31 is eliminated by the line head 1 and corrected as described later.

The SL array 31 is formed by arranging a large number of cylindrical lens elements (SL elements) 31a as shown in FIG. 6A as shown in FIG. 6B. It has come to produce. That is, each SL element (imaging element) 31a has a light quantity distribution that halves football as shown in FIG. 6 (a). In the array 31, as shown in FIG. 6B, periodic unevenness in the amount of light accompanying the arrangement pitch of the SL elements (imaging elements) 31a occurs. Here, the light amount unevenness ΔE of the SL array 31 is expressed by the following equation.
ΔE = {(imax−imin) / imin} × 100 (%)
(Refer to FIG. 6B for imax and imin)

This light amount unevenness ΔE differs depending on the degree of image overlap between the adjacent SLs 31a and 31a and the number of rows of the SL array 31. However, the amount of light unevenness ΔE depends on the configuration shown in FIG. The pitch of unevenness in the amount of light can be expressed. Also, in the figure, the transmitted light amount has a distribution (unevenness) as shown in FIG. 7A with respect to the position of the SL array 31 in the column direction.
For example, if the SL array 20 made of Nippon Sheet Glass is used as the SL array 31, the lens period of the SL array 31, that is, the period of unevenness in the amount of light is 0.56 mm. In addition, when the SL array 31 is arranged in a zigzag pattern in two rows, the lens period (period of unevenness in the amount of light) is half, that is, 0.28 mm.

  Therefore, in such a line head 1 that irradiates light to the SL array 31, each organic EL element 3 in the light emitting element array 3 </ b> A is corrected so as to cancel out the lens period (period of unevenness in the amount of light). The thickness of the functional layer, that is, the thickness of the light emitting layer 60 in this embodiment is periodically changed. That is, as shown in FIG. 7B, for the organic EL element 3 corresponding to a portion where the amount of light transmitted (guided) by the SL array 31 is small, the thickness of the light emitting layer 60 (functional layer) is reduced, Reduce the electrical resistance of the entire functional layer. In addition, for the organic EL element 3 corresponding to a portion with a large amount of light transmitted (guided) by the SL array 31, the thickness of the light emitting layer 60 (functional layer) is increased, and the electrical resistance of the entire functional layer is increased. As a result, with respect to the intensity (light emission amount) of light emitted from the line head 1 toward the SL array 31, the electrical resistance and the light emission amount are correlated with each other, as shown in FIG. The curve can be the same as that in FIG. That is, the relationship between the film thickness (electrical resistance) and the amount of light emission is obtained in advance by experiments, simulations, and the like, and the film thickness is adjusted based on the obtained results, thereby obtaining the same curve as in FIG. be able to.

  In this way, the intensity (light emission amount) of the light emitted from the line head 1 is periodically changed so as to eliminate unevenness (unevenness in light amount) transmitted (guided) by the SL array 31. The light irradiated from the line head 1 and further transmitted through the SL array 31 becomes a uniform light amount (image forming light amount) at all image forming positions as shown in FIG. Therefore, the image is uniformly and uniformly formed on the photosensitive drum 32.

  The SL array 20 made of Nippon Sheet Glass is used as the SL array 31, and the correction period of the line head 1 is adjusted so as to correct 0.56 mm, which is the lens period of the SL array 31 (period of unevenness in the amount of light). 0.56 mm was used, and the thickness of the light emitting layer 60 of each organic EL element 3 was periodically changed so that the intensity (light emission amount) of the emitted light was ± 5% of the average value. When the photosensitive drum 32 was exposed and printed, the density variation was ± 1% or less. For comparison, when the same printing was performed using a line head in which the thickness of the light emitting layer 60 (functional layer) of the organic EL element 3 was constant, the density variation was about ± 5%. Therefore, it was found that the line head 1 of the present embodiment can satisfactorily prevent exposure unevenness due to light amount unevenness of the SL array 31 and print unevenness, and improve the quality of the obtained print.

As described above, in the line head 1 of the present embodiment, the thickness of the functional layer of the organic EL element 3 forming the light emitting element array 3A is changed corresponding to the portion of the SL array 31. It is possible to eliminate the periodic light amount unevenness of the array 31 and correct this, thereby preventing exposure unevenness due to the light amount unevenness and further printing unevenness and improving the quality of the obtained print.
In the line head 1 of the above embodiment, the light emitting element row 3A is formed by one row of organic EL elements 3. However, the present invention is not limited to this. For example, the organic EL elements 3 are arranged in two rows. May be arranged in a zigzag pattern to form the light emitting element array 3A.
Moreover, in the said embodiment, although the example using an organic EL element was shown as an EL element formed in the line head 1 of this invention, it is needless to say that an inorganic EL element may be used instead. .

  Next, an image forming apparatus provided with the line head 1 of the present invention will be described. FIG. 8 is a view showing a first embodiment of the image forming apparatus of the present invention, and reference numeral 80 in FIG. 8 denotes the image forming apparatus. This image forming apparatus 80 includes organic EL array line heads 101K, 101C, 101M, and 101Y, which are examples of the line head of the present invention, and four corresponding photosensitive drums (image carriers) 41K, These are arranged in 41C, 41M, and 41Y exposure apparatuses, respectively, and are configured as a tandem system.

  The image forming apparatus 80 includes a driving roller 91, a driven roller 92, and a tension roller 93, and an intermediate transfer belt 90 is stretched around each of the rollers so as to be circulated in the direction of the arrow (counterclockwise) in FIG. Is. Photosensitive drums 41K, 41C, 41M, and 41Y are arranged at predetermined intervals with respect to the intermediate transfer belt 90. These photosensitive drums 41K, 41C, 41M, and 41Y have a photosensitive layer as an image carrier on the outer peripheral surface thereof.

  Here, K, C, M, and Y in the symbols mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are for black, cyan, magenta, and yellow, respectively. The meanings of these symbols (K, C, M, Y) are the same for the other members. The photosensitive drums 41K, 41C, 41M, and 41Y are driven to rotate in the arrow direction (clockwise) in FIG. 8 in synchronization with the driving of the intermediate transfer belt 90.

Around each photosensitive drum 41 (K, C, M, Y), charging means (corona charger) 42 for uniformly charging the outer peripheral surface of the photosensitive drum 41 (K, C, M, Y), respectively. (K, C, M, Y) and rotation of the photosensitive drum 41 (K, C, M, Y) on the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y) The organic EL array line head 101 (K, C, M, Y) of the present invention that sequentially scans the line in synchronization with each other is provided.
Here, an SL array (not shown) is disposed between the organic EL array line head 101 (K, C, M, Y) and the photosensitive drum 41 (K, C, M, Y). The organic EL array line head 101 (K, C, M, Y), as described above, each organic EL element forming the light emitting element array 3A so as to eliminate the unevenness of the light amount of the SL array and correct it. For No. 3, the thickness of the functional layer was changed corresponding to the portion of the SL array.

  Further, a developing device 44 (K) that applies toner as a developer to the electrostatic latent image formed by the organic EL array line head 101 (K, C, M, Y) to form a visible image (toner image). , C, M, Y) and a primary transfer roller 45 as transfer means for sequentially transferring the toner image developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 90 as a primary transfer target. (K, C, M, Y) and a cleaning device 46 (K, C) as a cleaning means for removing toner remaining on the surface of the photosensitive drum 41 (K, C, M, Y) after being transferred. , M, Y).

  Here, each organic EL array line head 101 (K, C, M, Y) is installed such that each array direction is along the bus line of the photosensitive drum 41 (K, C, M, Y). Then, the emission energy peak wavelength of each organic EL array line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photosensitive drum 41 (K, C, M, Y) are set to substantially coincide with each other. Has been.

  The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer. The film thickness of the developed developer is regulated by a regulating blade, and the developing roller is brought into contact with or pressed against the photosensitive drum 41 (K, C, M, Y), whereby the photosensitive drum 41 (K, C, M, A developer is attached in accordance with the potential level of Y) and developed as a toner image.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). Primary transfer is sequentially performed on the transfer belt 90. The toner images that are sequentially superimposed on the intermediate transfer belt 90 to become a full color are secondarily transferred to the recording medium P such as paper by the secondary transfer roller 66 and further pass through the fixing roller pair 61 that is a fixing unit. Then, the toner image is fixed on the recording medium P and then discharged onto a paper discharge tray 68 formed on the upper part of the apparatus by a pair of paper discharge rollers 62.

  In FIG. 8, reference numeral 63 is a paper feed cassette in which a large number of recording media P are stacked and held, 64 is a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 65 is a secondary transfer. A pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion of the roller 66; a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 90; A cleaning blade 67 serves as a cleaning unit that removes toner remaining on the surface of the intermediate transfer belt 90 after the secondary transfer.

  Next, a second embodiment of the image forming apparatus according to the present invention will be described. FIG. 9 is a vertical side view of a four-cycle image forming apparatus. In FIG. 9, an image forming apparatus 160 is provided with a developing device 161 having a rotary configuration, a photosensitive drum 165 that functions as an image carrier, the SL array, and a line head (organic EL array line head) as main components. An image writing unit (exposure unit) 167, an intermediate transfer belt 169, a sheet conveyance path 174, a fixing unit heating roller 172, and a sheet feeding tray 178 are provided.

  The developing device 161 is configured such that the developing rotary 161a rotates in the direction of arrow A about the shaft 161b. The inside of the development rotary 161a is divided into four, and image forming units for four colors of yellow (Y), cyan (C), magenta (M), and black (K) are provided. Reference numerals 162a to 162d are arranged in the image forming units for the four colors. The developing rollers rotate in the direction of the arrow B, and the toner supply rollers 163a to 163d rotate in the direction of the arrow C. Reference numerals 164a to 164d are regulating blades that regulate the toner to a predetermined thickness.

  In FIG. 9, reference numeral 165 denotes a photosensitive drum that functions as an image carrier as described above, 166 a primary transfer member, and 168 a charger. Reference numeral 167 denotes image writing means serving as exposure means in the present invention, which comprises the line head of the present invention and an SL array. The photosensitive drum 165 is rotationally driven in the direction of arrow D, which is the direction opposite to the developing roller 162a, by a drive motor (not shown), for example, a step motor. The line head constituting the image writing unit 167 is disposed in a state where the alignment (optical axis alignment) is performed between the line head and a lens element (not shown) or the photosensitive drum 165.

  The intermediate transfer belt 169 is stretched between the driving roller 170a and the driven roller 170b. The driving roller 170 a is connected to the driving motor of the photosensitive drum 165 and transmits power to the intermediate transfer belt 169. That is, the drive roller 170a of the intermediate transfer belt 169 is rotated in the direction of arrow E which is the opposite direction to the photosensitive drum 165 by the drive motor.

  The paper transport path 174 is provided with a plurality of transport rollers, a pair of paper discharge rollers 176, and the like, so that the paper is transported. An image (toner image) on one side carried on the intermediate transfer belt 169 is transferred to one side of the paper at the position of the secondary transfer roller 171. The secondary transfer roller 171 is brought into contact with and separated from the intermediate transfer belt 169 by a clutch. When the clutch is turned on, the secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 so that an image is transferred onto a sheet.

  The sheet on which the image has been transferred as described above is then subjected to a fixing process by a fixing device having a fixing heater H. The fixing device is provided with a heating roller 172 and a pressure roller 173. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. When the paper discharge roller pair 176 rotates in the reverse direction from this state, the paper reverses its direction and advances in the double-sided printing conveyance path 175 in the direction of arrow G. 177 is an electrical component box, 178 is a paper feed tray for storing paper, and 179 is a pickup roller provided at the outlet of the paper feed tray 178.

  For example, a low-speed brushless motor is used as a drive motor for driving the transport roller in the paper transport path. For the intermediate transfer belt 169, a step motor is used because color misregistration correction is required. Each of these motors is controlled by a signal from a control means (not shown).

  In the state shown in FIG. 9, a yellow (Y) electrostatic latent image is formed on the photosensitive drum 165, and a high voltage is applied to the developing roller 162a, whereby a yellow image is formed on the photosensitive drum 165. Is done. When the yellow back side and front side images are all carried on the intermediate transfer belt 169, the development rotary 161a rotates 90 degrees in the direction of arrow A.

  The intermediate transfer belt 169 rotates once and returns to the position of the photosensitive drum 165. Next, two images of cyan (C) are formed on the photosensitive drum 165, and this image is carried on the yellow image carried on the intermediate transfer belt 169. Thereafter, the 90-degree rotation of the development rotary 161 and the one-rotation process after the image is carried on the intermediate transfer belt 169 are repeated in the same manner.

  For carrying four color images, the intermediate transfer belt 169 rotates four times, and then the rotation position is further controlled to transfer the image onto the sheet at the position of the secondary transfer roller 171. The paper fed from the paper feed tray 178 is transported by the transport path 174, and the color image is transferred to one side of the paper at the position of the secondary transfer roller 171. The sheet on which the image is transferred on one side is reversed by the discharge roller pair 176 as described above, and stands by on the conveyance path. Thereafter, the sheet is conveyed to the position of the secondary transfer roller 171 at an appropriate timing, and the color image is transferred to the other side. The housing 180 is provided with an exhaust fan 181.

In the image forming apparatuses 80 and 160 shown in FIGS. 8 and 9, the line head (organic EL array line head) of the present invention as shown in FIG. 1 is provided as an exposure unit.
Therefore, in these image forming apparatuses 80 and 160, as described above, it is possible to prevent exposure unevenness due to light amount unevenness of the SL array and print unevenness, and improve the quality of the obtained print.
The image forming apparatus including the line head of the present invention is not limited to the above-described embodiment, and various modifications can be made.

The schematic diagram which shows one Embodiment of the line head of this invention. (A) is a principal part sectional side view of a line head, (b) is a schematic diagram. Sectional drawing explaining the manufacturing method of an organic electroluminescent apparatus in order of a process. Sectional drawing for demonstrating the process following FIG. The schematic diagram for demonstrating the usage pattern of a line head. (A), (b) is explanatory drawing of SL array and its light quantity nonuniformity. (A)-(d) is a graph for demonstrating the effect | action of the line head of this invention. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus of the present invention. It is a schematic block diagram which shows 2nd Embodiment of the image forming apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Line head, 2 ... Element substrate, 3 ... Organic EL element (EL element),
3A ... Light emitting element array, 25 ... Inorganic partition, 31 ... SL array (lens array),
31a ... Lens element (SL), 32 ... Photosensitive drum (exposed part),
60 ... light emitting layer (functional layer), 70 ... hole transport layer (functional layer),
80, 160 ... image forming apparatus, 221 ... organic partition

Claims (4)

A line head configured to irradiate and expose light to an exposed portion through a lens array in which lens elements are arranged;
A plurality of EL elements having a functional layer that emits light and emitting light from the functional layer toward the lens array to form a light emitting element array;
In the light emitting element array, the thickness of the functional layer is reduced for the EL element corresponding to the portion where the light amount guided by the lens array is small so that the light amount unevenness of the lens array is corrected. A line head characterized in that the thickness of the functional layer of each EL element is changed so that the thickness of the functional layer of the EL element corresponding to many parts is increased.   The functional layer includes at least an organic light emitting layer and a hole transport layer, and the film thickness of the functional layer of each EL element is changed by changing the film thickness of the organic light emitting layer between the EL elements. The line head according to claim 1, wherein the line head is formed. A plurality of EL elements having a functional layer that emits light and emitting light toward a lens array in which lens elements are arranged from the functional layer are formed on a substrate to form a light emitting element array, A method of manufacturing a line head comprising:
Forming a functional layer forming portion surrounded by a partition wall in each EL element forming region on the substrate;
Providing a functional layer material in the functional layer forming portion by a droplet discharge method and forming a functional layer,
In the step of forming the functional layer, in order to correct unevenness of the light amount of the lens array, the thickness of the functional layer is reduced at a portion where the light amount guided by the lens array is small, and the portion where the light amount guided by the lens array is large A method for manufacturing a line head, comprising increasing the thickness of the functional layer. An image forming apparatus comprising the line head according to claim 1 or a line head obtained by the manufacturing method according to claim 4 as exposure means.

Images