JP2003260812A - Optical print head and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small optical print head wherein a crosstalk is suppressed and a light beam of each element is collected on a photosensitive body by sufficient resolution and contrast, and to provide an image forming apparatus using the optical print head. <P>SOLUTION: There is disclosed the optical print head whereby a predetermined pattern is formed on an image carrier body 5 by projecting a modulated light beam from a light emitting section 2 of a light emitting element array 1 or a modulated light beam passing through a shutter section 2 of a light shutter element array to the image carrier body 5. Microlenses are arranged on arrangement positions respectively corresponding to the light emitting sections 2 of the light emitting element array 1 or the shutter sections 2 of the shutter element array 1 with a transparent body 3 and a low refractive index layer 6 having a refractive index lower than that of the transparent body 3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printing head and an image forming apparatus using the same, and more particularly to a ball lens corresponding to each element of a light emitting element array such as an organic EL array or an optical shutter element array. The present invention relates to an optical printing head for arranging the above and condensing the light flux from each element on the photoconductor and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made for using an organic EL array as an exposure head for an image forming apparatus.
The related items are as follows.

In Japanese Unexamined Patent Publication No. 10-55890, an organic EL array is collectively manufactured on an insulating substrate such as glass,
A separate driver IC is combined and a condensing rod lens array is used to form an image of the light emitting portion of the organic EL array on the photosensitive drum.

In Japanese Patent Laid-Open No. 11-198433,
The one-chip organic EL array having a plurality of rows is used, and the optical system for forming an image of the light emitting portion on the photosensitive drum is unknown. The EL layer of the organic EL array is deposited by vapor deposition.

In Japanese Patent Laid-Open No. 2000-77188, a microlens is formed on the upper surface of the substrate by an in-exchange method,
A microlens is formed on the back surface of the substrate by a method using a photoresist or a replica method, and an organic EL array having a resonator structure is deposited by vapor deposition in alignment with the microlens.

Japanese Unexamined Patent Publication No. 10-12377 relates to a method for manufacturing an active matrix type organic EL display body, in which an organic light emitting layer is formed on a glass substrate having a thin film transistor by an ink jet method.

In Japanese Patent Laid-Open No. 2000-323276,
The hole injecting layer and the organic light emitting layer of the organic EL element are formed by providing partition walls and applying them by an inkjet method.

In Japanese Patent Laid-Open No. 2001-18441, a printer is constructed by forming a light emitting layer and a TFT layer for controlling the light emission inside the photosensitive drum.

In addition to the organic EL array, various proposals have been made to use an LED array or a liquid crystal shutter array as an exposure head for an image forming apparatus. In these cases, the light emitting portion of the LED array or the liquid crystal shutter array is also used. Many proposals use a condensing rod lens array or a microlens array to condense the light flux from the shutter portion onto the photosensitive drum.

[0010]

In the above prior art, when an organic EL array or the like is used for an exposure head of a printer such as an electrophotographic system, the light emitting portion of the organic EL array or LED array or the shutter portion of the liquid crystal shutter array is used. When a condensing rod lens array is used to condense the luminous flux of the above on the photosensitive drum, the optical path length becomes long and the size becomes large.
Since the shutter portions are not arranged one-to-one with respect to each shutter portion, periodic light amount unevenness occurs, and further, since the condensing rod lens is sophisticated in terms of manufacturing method, an increase in cost cannot be avoided.

In the case of using a microlens array, each microlens is arranged in a one-to-one correspondence with each light emitting portion and each shutter portion. There is a problem that crosstalk is likely to occur, which is incident on pixel positions that do not correspond through the microlenses that do not correspond to, and that leads to a reduction in resolution and the like.

The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a light emitting element array such as an organic EL array, an LED array or an optical shutter element array such as a liquid crystal shutter array. The crosstalk of the optical printing head, which arranges the microlenses corresponding to the elements, is reduced, and the light flux from each element is condensed on the image carrier such as the photoconductor with sufficient resolution and contrast. An object of the present invention is to provide a small optical printing head and an image forming apparatus using the same.

[0013]

A first optical printing head of the present invention that achieves the above object transmits a modulated light beam from a light emitting section of a light emitting element array or a modulated light beam transmitted through a shutter section of an optical shutter element array. In an optical printing head for projecting on an image carrier to form a predetermined pattern on the image carrier, a predetermined thickness is provided at an alignment position corresponding to each light emitting portion of the light emitting element array or each shutter portion of the optical shutter element array. Hemispherical microlenses are arranged through the transparent body, and the light incident on the hemispherical microlenses adjacent to the hemispherical microlenses at the corresponding positions from the light emitting section or the shutter section is the hemispherical refracting surface. The thickness of the transparent body is set so that the transparent body does not face the image carrier even if it is totally reflected or refracted. .

In the second optical printing head of the present invention, the modulated light flux from the light emitting portion of the light emitting element array or the modulated light flux transmitted through the shutter portion of the optical shutter element array is projected on the image bearing member. In the optical printing head for forming a predetermined pattern on a hemispherical microlens via a transparent body of a predetermined thickness at an alignment position corresponding to each light emitting portion of the light emitting element array or each shutter portion of the optical shutter element array. It is arranged such that at least a part of the light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the light emitting unit or the shutter unit is totally reflected by the hemispherical refracting surface. It is characterized in that the thickness of the transparent body is set.

In the first and second optical printing heads,
The thickness of the transparent body is preferably set to 50% or less of the arrangement pitch of the light emitting portions of the light emitting element array or the arrangement pitch of the shutter portions of the optical shutter element array.

In the third optical printing head of the present invention, the modulated light flux from the light emitting portion of the light emitting element array or the modulated light flux transmitted through the shutter portion of the optical shutter element array is projected on the image bearing member. In the optical printing head that forms a predetermined pattern on the transparent body, the transparent body and the refractive index lower than that of the transparent body are sequentially arranged at alignment positions corresponding to the light emitting sections of the light emitting element array or the shutter sections of the optical shutter element array. The microlenses are arranged through the low refractive index layer having a refractive index.

In this case, whether the low refractive index layer is an air layer,
Alternatively, it is preferably made of any one of magnesium fluoride, silica airgel, and fluororesin.

The above microlenses can be made of glass or plastic.

Further, it is desirable that the above microlenses have an antireflection coating.

In the third optical printing head, the microlenses may be hemispherical lenses or ball lenses.

The present invention includes an image forming apparatus equipped with the above-described optical printing head as an exposure head for writing an image on an image carrier, one of which is, for example, an image carrier. At least two image forming stations each having a charging unit, an exposure head, a developing unit, and a transfer unit are provided around the image forming apparatus, and the transfer medium passes through each station to form a color image by a tandem system. There is.

In the present invention, the light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the light emitting portion or the shutter portion is totally reflected or refracted by the hemispherical refracting surface. The thickness of the transparent body is set so as not to face the image carrier, or at least a part of the light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the light emitting part or the shutter part is The thickness of the transparent body is set so as to totally reflect on the hemispherical refracting surface, or transparent at the alignment position corresponding to each light emitting portion of the light emitting element array or each shutter portion of the optical shutter element array. Since the microlens is arranged through the body and the low refractive index layer having a refractive index lower than that of the transparent body, crosstalk light and stray light are reduced. It can be. Further, when the low refractive index layer is interposed, the distance between the microlens and the light emitting section or the shutter section can be increased without causing crosstalk, and thereby the microlens magnification can be reduced. Since the energy density on the image carrier can be increased and the focused spot diameter can also be reduced, sufficient resolution and contrast can be obtained.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The optical printing head of the present invention and an image forming apparatus using the same will be described below with reference to embodiments.

FIG. 1 is a schematic cross-sectional view showing the structure of the optical printing head of the first embodiment of the present invention. The surface of the light emitting portion 2 is an organic EL, LED or the like, or a liquid crystal shutter or the like. The shutter unit 2 of the light emitting element array 1 is arranged.
Alternatively, the optical shutter element array 1 is configured. In the case of the optical shutter element array 1, the shutter section 2 itself does not emit light, but by disposing an illumination light source (backlight) behind it, the shutter section 2 becomes a secondary light source. Unless otherwise specified, the optical shutter unit 2 is also called the light emitting unit 2, and the light modulator array 1 including the light emitting device array 1 and the optical shutter device array 1 is also included.
Call.

In the present embodiment, the hemispherical lens is provided on the opposite surface of the transparent body 3 through the transparent body 3 having a protective function, in an alignment position corresponding to each light emitting portion 2 of the light modulation element array 1 in a one-to-one correspondence. The micro lens 4 is adhered and fixed. Then, the light flux from each light emitting unit 2 passes through the transparent body 3 and is condensed by the microlens 4 on the image carrier 5 such as a photoconductor (in the case of electrophotography) that constitutes the projection target at a predetermined magnification. It is arranged.

By appropriately selecting the thickness of the transparent body 3 as will be described later, the light incident on the refracting surface (hemispherical surface) of the microlens 4 corresponding to the light emitting portion 2 is incident on the corresponding microlens 4. The light is focused on the image carrier 5 by. A predetermined line pattern emitted by the light modulation element array 1 can be written on the image carrier 5 by this condensed light flux.

On the other hand, of the light emitted from the light emitting section 2 and incident on the adjacent microlens 4, the light near the microlens 4 corresponding to the light emitting section 2 is the refracting surface (hemispherical surface) of the adjacent microlens 4. Is incident at an incident angle larger than the critical angle and is totally reflected, and does not reach the image carrier 5. Therefore, this light does not become crosstalk light.

Of the light emitted from the light emitting section 2 and entering the adjacent microlens 4, the light entering the side opposite to the microlens 4 corresponding to the light emitting section 2 is the refracting surface of the adjacent microlens 4. Since it is refracted by (hemispherical surface) and further enters the adjacent microlens 4, it does not reach the image carrier 5. Therefore, this light also does not become crosstalk light.

In order to satisfy such conditions, the transparent body 3
By selecting the thickness of, it is possible to print with less crosstalk between pixels.

Specific numerical examples of this embodiment will be shown below.

Refractive index of transparent body 3: 1.73 Thickness of transparent body 3: 20 μm Shape of microlens 4: hemispherical, diameter: 80 μm Refractive index of microlens: 1.95 Pitch of light emitting part 2: 80 μm The size of the part 2 is 10 μm, and the distance between the microlens 4 and the image carrier 5 is 300 μm. An optical path tracing diagram in such a specific example is shown in FIG. 2 and its light amount distribution diagram is shown in FIG. It is clear from FIGS. 2 and 3 that there is almost no crosstalk in this specific numerical example.

In this numerical example, when the transparent body 3 is too thick and has a thickness of 40 μm or more, crosstalk occurs as shown in FIG. 4 and the resolution and the contrast deteriorate. Therefore, the thickness of the transparent body 3 is preferably 50% or less, more preferably 30% or less of the arrangement pitch of the light emitting units 2.

FIG. 5 is a schematic sectional view showing the structure of the optical printing head of the second embodiment of the present invention. In this embodiment, a transparent member provided on the surface of the light modulation element array 1 is used. Three
The air layer 6 is interposed between the microlenses 4 and the microlenses 4 that are aligned in correspondence with the respective light emitting portions 2 of the light modulation element array 1.

With this structure, the light that is about to enter the refracting surface (convex surface) of the microlens 4 corresponding to the light emitting portion 2 passes through the air layer 6, and the corresponding microlens 4 causes the image on the image carrier 5. Is focused on. A predetermined line pattern emitted by the light modulation element array 1 can be written on the image carrier 5 by this condensed light flux.

On the other hand, of the light emitted from the light emitting section 2 and entering the adjacent microlens 4, the light near the microlens 4 corresponding to the light emitting section 2 is the refracting surface (convex surface) of the adjacent microlens 4. ) At an incident angle larger than the critical angle and is totally reflected and does not reach the image carrier 5. Therefore, this light does not become crosstalk light.

Of the light emitted from the light emitting section 2 and entering the adjacent microlens 4, the light entering the side away from the microlens 4 corresponding to the light emitting section 2 is critical to the air layer 6. Since the light enters at an angle of incidence equal to or larger than the angle, the light is totally reflected at the boundary with the air layer 6, and thus does not reach the image carrier 5. Therefore, this light also does not become crosstalk light.

Thus, the light emitting section 2 and the microlens 4 are
The air layer 6 having a lower refractive index than the transparent body 3 at an appropriate position between
By interposing, the printing with less crosstalk between pixels becomes possible. In addition, in order to provide the air layer 6 between the transparent body 3 and the microlens 4, it may be fixed by an outer frame so as to provide a space between the transparent body 3 and the microlens 4, or between the substrates of the liquid crystal cell. Beads and the like similar to the spacers that provide a space may be interposed between the transparent body 3 and the substrate of the microlens 4.

Specific numerical examples of this embodiment will be shown below.

Refractive index of transparent body 3: 1.73 Thickness of transparent body 3: 50 μm Thickness of air layer 6: 5 μm Shape of microlens 4: hemispherical, diameter of 80 μm Refractive index of microlens 4: 1.52 Pitch of light emitting part 2: 80 μm Size of light emitting part 2: 10 μm Distance between microlens 4 and image carrier 5: 300 μm FIG. 6 is an optical path tracing diagram in such a specific example, and FIG. 7 is a light amount distribution diagram thereof. Shown in. It is clear from FIGS. 6 and 7 that there is almost no crosstalk in this specific numerical example.

As a comparative example, FIG. 8 shows an optical path tracing diagram in the case where an air layer having a low refractive index layer is not used and an adhesive having a refractive index of 1.52 is used instead. In this case, crosstalk has occurred.

In this embodiment, crosstalk does not occur even if the transparent body 3 is thicker than in the first embodiment. Therefore, it becomes possible to reduce the magnification of the image of the light emitting unit 2 on the image carrier 5 by the microlens 4, and the condensing performance is improved. Further, the refractive index of the microlens 4 can be lowered, and a plastic lens can be used as the microlens 4.

The same effect can be obtained by using a low refractive index layer such as silica airgel (refractive index: 1.03) instead of the air layer 6.

When a substance having a refractive index of around 1.3 such as magnesium fluoride (MgF ₂ ; refractive index: 1.38) or fluororesin (refractive index: 1.34) is used instead of the air layer 6. , The effect of totally reflecting the crosstalk light on the low refractive index layer is reduced, but the light having a large angle is totally reflected, so that it has an effect of reducing stray light.

FIG. 9 is a schematic sectional view showing the structure of the optical printing head of the third embodiment of the present invention. In this embodiment, the glass ball lens 7 and the light modulation element array 1 are used. The light emitting units 2 are arranged in an array corresponding to the respective light emitting units 2.
The light beam from the lens is focused on the image carrier 5 at a predetermined magnification by the ball lens 7 at a corresponding position. As a low refractive index layer having a function of totally reflecting the crosstalk light, a fluororesin coating layer 8 having a refractive index of 1.34 is provided on the surface of the transparent body 3, and a ball lens 7 and a transparent adhesive 9 are provided thereon. It is fixed by adhesion. The transparent body 3 has a refractive index of 1.52, and the glass of the ball lens 7 has a refractive index of 1.7.
8 As shown in FIG. 9, the light incident on the ball lens 7 in front of the light emitting unit 2 is condensed on the image carrier 5, and the light emitted from the light emitting unit 2 at a large angle is irradiated with the fluororesin coating layer 8.
The light is totally reflected at the interface of (3), does not enter the ball lens 7, and does not reach the image carrier 5. Therefore, stray light is reduced and printing quality is improved.

Here, the ball lens 7 is a single positive lens made of a transparent spherical body, and has a focal length determined by the refractive index of the transparent body, the refractive index of the surroundings, and the radius.

FIG. 10 shows a hemispherical micro-lens on both surfaces of a transparent substrate 11 as a microlens 10 for condensing the light flux from the air layer 6 and the light emitting portion 2 on the image carrier 5 to totally reflect the crosstalk light. An example is shown in which the lens 4 is prepared by aligning the lenses 4 on the front and back by an inkjet method or the like.
An air layer 6 is formed between the transparent body 3 and the transparent substrate 11 via a spacer 12. The crosstalk and the stray light reducing action are clear from the above-mentioned embodiment.

In any of the above embodiments, the antireflection coating or the antistatic coating may be applied to the surfaces of the microlenses 4, 7, 10.

Here, an example of an organic EL array usable as the light modulation element array 1 will be described.

In the organic EL array 20 of this example, as shown in the plan view of FIG. 11, two rows of arrays 31, 31 'are arranged in parallel and their pixels are arranged in a staggered pattern.
Each array 31, 31 ′ is composed of a large number of pixels 32 arranged in a straight line, each pixel 32 has the same configuration, and an organic EL light emitting section 22 and a T for controlling light emission of the organic EL light emitting section 22 are arranged.
It consists of FT33.

In FIG. 12, the organic EL light emitting portion 22 of one pixel 32 is shown.
A cross-sectional view including the TFT 33 and the TFT 33 is shown, which will be described in the order of manufacturing. First, the TFT 33 is formed on the glass substrate 21. Although various methods for manufacturing the TFT 33 are known. For example, a silicon oxide film is first deposited on the glass substrate 21, and then an amorphous silicon film is deposited. next,
This amorphous silicon film is irradiated with excimer laser light to be crystallized to form a polysilicon film to be a channel. After patterning this polysilicon film, a gate insulating film is deposited and a gate electrode made of tantalum nitride is further formed. Subsequently, the source / drain portion of the N-channel TFT is formed by ion implantation of phosphorus, and the source / drain portion of the P-channel TFT is formed by ion implantation of boron. After activating the ion-implanted impurities, the first interlayer insulating film is deposited, the first contact hole is opened, the source line is formed, the second interlayer insulating film is deposited, the second contact hole is opened, and the metal pixel electrode is formed. Do it sequentially,
An array of TFTs 33 is completed (see, for example, "Polymer type organic EL display" in 8th Electronic Display Forum (2001.4.18)). Here, this metal pixel electrode serves as the cathode 34 of the organic EL light emitting portion 22 and also serves as the reflective layer of the organic EL light emitting portion 22, and is a metal thin film electrode of Mg, Ag, Al, Li or the like. It is formed.

Next, partition walls (banks) 29 having holes 35 corresponding to the organic EL light emitting portions 22 and having a predetermined height are formed. The partition 29 can be formed by an arbitrary method such as a photolithography method or a printing method, as disclosed in JP-A-2000-353594. For example, when the lithography method is used, an organic material is applied according to the height of the bank by a predetermined method such as spin coating, spray coating, roll coating, die coating, or dip coating, and a resist layer is applied thereon. And the partition wall 29
A mask is applied according to the shape, and the resist is exposed and developed to leave the resist adapted to the shape of the partition 29.
Finally, the partition wall material is etched to remove the partition wall material other than the mask. Further, the bank (convex portion) may be formed by two or more layers in which the lower layer is an inorganic material and the upper layer is an organic material. Further, as disclosed in Japanese Patent Laid-Open No. 2000-323276, the material forming the partition wall 29 is not particularly limited as long as it has durability against the solvent of the EL material, but it is treated with fluorocarbon gas plasma treatment to obtain Teflon ( Organic materials such as acrylic resins, epoxy resins, and photosensitive polyimides are preferable because they can be registered trademarks). It may be a laminated partition wall having an inorganic material such as liquid glass as a lower layer. Further, the partition wall 29 is preferably made black or opaque by mixing carbon black or the like into the above material.

Then, immediately before applying the ink composition for the light emitting layer of the organic EL, the substrate provided with the partition walls 29 is subjected to continuous plasma treatment of oxygen gas and fluorocarbon gas plasma. As a result, for example, the surface of the polyimide forming the partition walls 29 is made water-repellent and the surface of the cathode 34 is made hydrophilic, so that the wettability on the substrate side for finely patterning the inkjet droplets can be controlled. As an apparatus for generating plasma, an apparatus for generating plasma in vacuum or an apparatus for generating plasma in the atmosphere can be used as well.

Next, the ink composition for the light emitting layer is discharged from the head 71 of the ink jet type printing apparatus 70 into the hole 35 of the partition 29, and patterning is applied on the cathode 34 of each pixel. After coating, the solvent is removed and heat treatment is performed to form the light emitting layer 36.

Incidentally, the ink jet method referred to in the present invention is a piezo jet method for ejecting an ink composition by utilizing mechanical energy of a piezoelectric element or the like, and bubbles are generated by utilizing heat energy of a heater to generate bubbles. Any of the thermal methods of ejecting the ink composition based on the generation may be used ("Fine Imaging and Hard Copy", 1999.
Issued 1.7 (Corona Inc.) p. 43). In FIG.
A configuration example of a piezo jet type head is shown. The inkjet head 71 includes, for example, a stainless nozzle plate 72 and a vibrating plate 73, which are joined together via a partition member (reservoir plate) 74. A partition member 74 is provided between the nozzle plate 72 and the vibration plate 73.
This forms a plurality of ink chambers 75 and a liquid pool (not shown). The interiors of the ink chamber 75 and the liquid pool are filled with the ink composition, and the ink chamber 75 and the liquid pool communicate with each other through the supply port. Furthermore, the nozzle plate 7
No. 2 is provided with a nozzle hole 76 for ejecting the ink composition from the ink chamber 75 in a jet shape. On the other hand, the ink jet head 71 is provided with an ink introduction hole for supplying the ink composition to the liquid pool. Further, on the surface of the vibrating plate 73 opposite to the surface facing the ink chamber 75, the piezoelectric element 7 is made to correspond to the position of the ink chamber 75.
8 are joined. This piezoelectric element 78 has a pair of electrodes 7.
The piezoelectric element 78 is located between 9 and bends so that the piezoelectric element 78 projects outward when energized. This increases the volume of the ink chamber 75. Therefore, the ink composition corresponding to the increased volume flows into the ink chamber 75 from the liquid reservoir through the supply port. Next, when the energization of the piezoelectric element 78 is released, both the piezoelectric element 78 and the diaphragm 73 return to their original shapes.
As a result, the space 75 also returns to its original volume, so the ink chamber 75
The pressure of the ink composition inside rises, and the ink composition is ejected from the nozzle holes 76 toward the substrate provided with the partition walls 29.

After forming the light emitting layer 36 in the hole 35, the ink composition for the hole injection layer is discharged from the head 71 of the ink jet printing apparatus 70 onto the light emitting layer 36 in the hole 35, and then on the light emitting layer 36 of each pixel. Then, patterning is applied.
After coating, the solvent is removed and heat treatment is performed to form the hole injection layer 37.

The light emitting layer 36 and the hole injection layer 37 described above are used.
The order of may be reversed. It is desirable to dispose a layer more resistant to moisture on the surface side (the side farther from the substrate 21).

Further, the light emitting layer 36 and the hole injection layer 37 are formed by a known spin coating method, dip method or vapor deposition method instead of being formed by applying the ink composition by the ink jet method as described above. You can also

The material used for the light emitting layer 36 and the material used for the hole injection layer 37 are described in, for example, JP-A-10-.
Various publicly known ones such as No. 12377 and Japanese Patent Laid-Open No. 2000-323276 can be used, and the details are omitted.

A light emitting layer 36 and a hole injection layer 37 are sequentially formed in the holes 35 of the partition 29, and then a transparent electrode 38 serving as an anode of the organic EL is deposited on the entire surface of the substrate by a vacuum deposition method to form holes. The transparent electrode 38 is connected to the injection layer 37. Examples of the material of the transparent electrode 38 include a tin oxide film, an ITO film, a composite oxide film of indium oxide and zinc oxide, and a photolithography method, a sputtering method, a pyrosol method or the like can be adopted in addition to the vacuum deposition method. .

In this way, the organic EL array 20 usable as the light modulation element array 1 is manufactured.

By the way, the optical printing head 101 in which the crosstalk of the present invention is reduced as described above (in this embodiment, the organic EL array 20 of FIGS. 11 and 12 is used as the light modulation element array 1, and FIG. 14) is adopted in FIG.
As shown in the side view in FIG. 1, each organic EL light emitting section 22 (on the light emitting section 2 of the light modulation element array 1 is arranged on the surface S distant from the optical printing head 101 by the working distance WD in the same array pattern as the pixel array. The corresponding luminous flux from () is collected. Therefore, the surface S is relatively moved in the direction orthogonal to the longitudinal direction of the optical printing head 101, and the light emission of each organic EL light emitting section 22 of the optical printing head 101 is controlled by the TFT 33. A predetermined pattern can be recorded on S.

Therefore, in the present invention, the optical printing head 101 using the above-described organic EL array is used as an exposure head of an electrophotographic color image forming apparatus, for example. FIG. 15 shows four similar photoconductor drums 41K, 41C, 41M corresponding to four similar optical printing heads 101K, 101C, 101M, 101Y of the present invention.
It is a front view which shows the whole schematic structure of one example of the color image forming apparatus of the tandem system arrange | positioned at the exposure position of 41Y, respectively. As shown in FIG. 15, this image forming apparatus includes a driving roller 51, a driven roller 52, and a tension roller 53.
An intermediate transfer belt 50 that is tensioned by and is circulated and driven to circulate in the direction of the arrow (counterclockwise) in the drawing is provided, and four image carriers are arranged at a predetermined interval with respect to the intermediate transfer belt 50. Photoconductors 41K, 41C, 41M and 41Y having a photosensitive layer are arranged on the outer peripheral surface of the body. K, C, M, and Y added after the symbols mean black, cyan, magenta, and yellow, respectively, and indicate that they are photoconductors for black, cyan, magenta, and yellow, respectively.
The same applies to other members. Photoconductor 41K, 41
C, 41M, and 41Y are rotationally driven in the direction of the arrow (clockwise) in the figure in synchronization with the driving of the intermediate transfer belt 50, but the photosensitive members 41 (K, C, M, and Y) are exposed to light around them. Charging means (corona charger) 42 (K, C, M, Y) for uniformly charging the outer peripheral surface of the body 41 (K, C, M, Y)
And the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y), the photoconductor 41 (K, C, M, Y).
The optical printing head 101 (K, using the organic EL array as described above of the present invention, which sequentially scans in line in synchronization with the rotation of
C, M, Y) and this optical printing head 101 (K, C,
The developing device 44 (K, which applies toner as a developer to the electrostatic latent image formed by M, Y) to form a visible image (toner image).
C, M, Y) and the developing device 44 (K, C, M, Y)
The primary transfer roller 45 (K, C, M, Y) as a transfer unit that sequentially transfers the toner image developed in step 1 to the intermediate transfer belt 50 that is the primary transfer target, and the photoreceptor 4 after the transfer.
1 (K, C, M, Y) as a cleaning means for removing the toner remaining on the surface of the cleaning device 46.
(K, C, M, Y).

Here, each optical printing head 101 (K, C,
M, Y) is separated from the surface of the corresponding photoconductor 41 (K, C, M, Y) by the working distance WD, and each optical printing head 10 is moved.
The array direction of 1 (K, C, M, Y) is the photosensitive drum 41.
It is installed along the bus line of (K, C, M, Y). Then, the emission energy peak wavelength of each optical printing head 101 (K, C, M, Y) and the photoconductor 41 (K, C, M, Y).
The sensitivity peak wavelength is set to substantially match.

The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer,
The one-component developer is conveyed to the developing roller by, for example, a supply roller, the film thickness of the developer adhered to the surface of the developing roller is regulated by a regulating blade, and the developing roller is moved to the photoconductor 41 (K,
C, M, Y) to contact or press the photoconductor 41
The toner is developed as a toner image by attaching a developer according to the potential level of (K, C, M, Y).

The black, cyan, magenta, and yellow toner images formed by the four-color monochromatic toner image forming station are transferred to the primary transfer rollers 45 (K, C, M, and
The primary transfer bias applied to Y) sequentially primary-transfers the toner images onto the intermediate transfer belt 50, and the toner images in full color are sequentially superposed on the intermediate transfer belt 50. The image is secondarily transferred onto the recording medium P, is fixed on the recording medium P by passing through the fixing roller pair 61 which is a fixing portion, and is discharged onto the paper discharge tray 68 formed on the upper part of the apparatus by the paper discharge roller pair 62.

In FIG. 15, 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 one by one from the paper feed cassette 63, and 65 is a double roller. A pair of gate rollers that define the timing of supplying the recording medium P to the secondary transfer portion of the next transfer roller 66, and 66 is a secondary transfer unit that forms a secondary transfer portion with the intermediate transfer belt 50. The rollers 67 are cleaning blades as a cleaning unit that removes the toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer.

The optical printing head of the present invention and the image forming apparatus using the same have been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0068]

As is apparent from the above description, according to the optical printing head of the present invention and the image forming apparatus using the same,
Light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the light emitting part or the shutter part is totally reflected by the hemispherical refracting surface, or does not go to the image carrier even if refracted. The thickness of the transparent body is set to, or at least a part of the light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the light emitting part or the shutter part is totally reflected by the hemispherical refracting surface. The thickness of the transparent body is set so as to reflect light, or the transparent body and the refractive index of the transparent body are arranged at the alignment positions corresponding to the light emitting portions of the light emitting element array or the shutter portions of the optical shutter element array, respectively. Since the microlens is arranged via the low refractive index layer having a lower refractive index, crosstalk light and stray light can be reduced. Further, when the low refractive index layer is interposed, the distance between the microlens and the light emitting section or the shutter section can be increased without causing crosstalk, and thereby the microlens magnification can be reduced. Since the energy density on the image carrier can be increased and the focused spot diameter can also be reduced, sufficient resolution and contrast can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a configuration of an optical printing head according to a first embodiment of the present invention.

FIG. 2 is an optical path tracing diagram in a specific numerical example of the first embodiment.

FIG. 3 is a light amount distribution chart in a specific numerical example of the first embodiment.

FIG. 4 is an optical path trace diagram of a comparative example with respect to the first embodiment.

FIG. 5 is a schematic sectional view showing a configuration of an optical printing head according to a second embodiment of the present invention.

FIG. 6 is an optical path tracing diagram in a specific numerical example of the second embodiment.

FIG. 7 is a light amount distribution chart in a specific numerical example of the second embodiment.

FIG. 8 is an optical path tracing diagram of a comparative example with respect to the second embodiment.

FIG. 9 is a schematic cross-sectional view showing the structure of the optical printing head of the third embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing the structure of an optical printing head of another embodiment of the present invention.

FIG. 11 is a plan view of an example of an organic EL array that can be used as a light modulation element array in the present invention.

12 is a cross-sectional view of one pixel of the array of FIG.

FIG. 13 is a diagram showing a configuration example of a piezo jet type head in an inkjet type.

FIG. 14 is a side view showing how light is condensed by the optical printing head of the present invention.

FIG. 15 is a front view showing the overall schematic configuration of an example of a tandem type color image forming apparatus in which the optical printing head of the present invention is arranged.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light modulation element array (light emitting element array, optical shutter element array) 2 ... Light emitting portion (shutter portion) 3 ... Transparent body 4 ... Microlens 5 ... Image carrier 6 ... Air layer 7 ... Ball lens 8 ... Fluororesin coat Layer 9 ... Transparent adhesive 10 ... Microlens 11 ... Transparent substrate 12 ... Spacer 20 ... Organic EL array 21 ... Glass substrate 22 ... Organic EL light emitting part 23 ... Transparent member 24 ... Transparent adhesive (UV curable type, thermosetting type) 25 ... Shading pattern layer 29 ... Partition walls (bank) 31, 31 '... Array 32 ... Pixel 33 ... TFT 34 ... Cathode 35 ... Hole 36 ... Light emitting layer 37 ... Hole injection layer 38 ... Transparent electrode 41 (K, C, M) , Y) ... Photosensitive drum 42 (K, C, M, Y) ... Charging means (corona charger) 44 (K, C, M, Y) ... Developing device 45 (K, C, M, Y) ... Primary Transfer roller 46 (K, C, M, Y) ... cleaning device 50 ... intermediate transfer belt 51 ... drive roller 52 ... driven roller 53 ... tension roller 61 ... fixing roller pair 62 ... paper discharge roller pair 63 ... paper feed cassette 64 ... pickup roller 65 ... gate roller pair 66 ... two Next transfer roller 67 ... Cleaning blade 68 ... Paper ejection tray 70 ... Inkjet printing device 71 ... Head 72 ... Nozzle plate 73 ... Vibration plate 74 ... Partition member (reservoir plate) 75 ... Ink chamber 76 ... Nozzle hole 78 ... Piezoelectric element 79 Electrode 101 (K, C, M, Y) ... Optical printing head S using an organic EL array ... Surface P ... Recording medium

Claims (11)

[Claims] 1. An optical printing method for projecting a modulated light beam from a light emitting section of a light emitting element array or a modulated light beam transmitted through a shutter section of an optical shutter element array onto an image carrier to form a predetermined pattern on the image carrier. In the head, a hemispherical microlens is arranged at an alignment position corresponding to each light emitting portion of the light emitting element array or each shutter portion of the optical shutter element array via a transparent body of a predetermined thickness, and the light emitting portion or the The light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the shutter portion is totally reflected by the hemispherical refracting surface or is refracted so as not to go to the image carrier. An optical printing head characterized in that the thickness of the transparent body is set. 2. Optical printing for forming a predetermined pattern on the image carrier by projecting the modulated light beam from the light emitting section of the light emitting element array or the modulated light beam transmitted through the shutter section of the optical shutter element array onto the image carrier. In the head, a hemispherical microlens is arranged at an alignment position corresponding to each light emitting portion of the light emitting element array or each shutter portion of the optical shutter element array via a transparent body of a predetermined thickness, and the light emitting portion or the The thickness of the transparent body is set such that at least a part of the light incident on the hemispherical microlens adjacent to the hemispherical microlens at the corresponding position from the shutter portion is totally reflected by the hemispherical refracting surface. An optical printing head characterized by this. 3. The thickness of the transparent body is set to 50% or less of the arrangement pitch of the light emitting portions of the light emitting element array or the arrangement pitch of the shutter portions of the optical shutter element array. The optical printing head according to 1 or 2. 4. An optical printing method for projecting a modulated light beam from a light emitting section of a light emitting element array or a modulated light beam transmitted through a shutter section of an optical shutter element array onto an image carrier to form a predetermined pattern on the image carrier. In the head, a transparent body and a low-refractive index layer having a refractive index lower than that of the transparent body are sequentially arranged at alignment positions corresponding to the respective light-emitting sections of the light-emitting element array or the shutter sections of the optical shutter element array. The optical printing head is characterized in that a microlens is arranged. 5. The optical printing head according to claim 4, wherein the low refractive index layer is an air layer. 6. The low refractive index layer is magnesium fluoride,
The optical printing head according to claim 4, wherein the optical printing head is made of either silica airgel or fluororesin. 7. The optical printing head according to claim 1, wherein the microlenses are made of glass or plastic. 8. The microlens is provided with an antireflection coating.
The optical printing head according to any one of 1. 9. The optical printing head according to claim 4, wherein the microlenses are hemispherical lenses or ball lenses. 10. An image forming apparatus comprising the optical printing head according to claim 1 as an exposure head for writing an image on an image carrier. 11. The image forming apparatus is provided with at least two image forming stations having a charging unit, an exposure head, a developing unit, and a transfer unit around the image carrier, and a transfer medium passes through each station. 11. The image forming apparatus according to claim 10, wherein the image forming apparatus is a tandem type color image forming apparatus that forms a color image.