Rod lens array unit, production method of rod lens array unit, LED print head, image sensor head, image forming apparatus, and image reader

A rod lens array unit includes at least a rod lens array that includes a plurality of rod lenses arranged in a line, each of the rod lenses having an optical axis extending in an optical axis direction, and a pair of side plate parts stacked so as to sandwich the rod lens array. Wherein, end faces of the side plate parts in the optical axis direction of the rod lens array are positioned inside an end face of the rod lens array in the optical axis direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119 to Japanese Patent Application No. 2015-071984 filed on Mar. 31, 2015, the entire contents which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a rod lens array unit including a rod lens array, a production method of the rod lens array unit, an LED print head including the rod lens array unit, an image sensor head including the rod lens array unit, an image forming apparatus including the LED print head, and an image reader including the image sensor head.

BACKGROUND

Generally, a rod lens array unit including a rod lens array in which a plurality of distributed index type rod lenses (hereinafter referred to as “rod lenses”) are arranged along a predetermined direction is used as, for example, an LED print head used as an exposure device such as an LED (light Emitting Diode) printer, etc., and an image sensor head used as a reader such as an image scanner, etc. In a rod lens array unit, it is desired to reduce the variation in focal length of the rod lenses along the arrangement direction of the plurality of rod lenses included in the rod lens array. Further, it is desired that an excellent optical performance of the rod lens array unit is maintained by forming each of the end faces of the plurality of rod lenses as a mirror finished surface. Therefore, a method is proposed, in which, at the time of producing the rod lens array unit, a rod lens array is arranged between a pair of side plates that sandwiches and holds the rod lens array, and the edge part of the rod lens array and the side plates are cut to align the lengths of the plurality of rod lenses and finish the end faces of the rod lens array into mirror finished surfaces (for example, see Patent Document 1).

Japanese Unexamined Patent Application Publication No. 2005-181949

However, at the time of producing the rod lens array unit, for example, chips, etc., may remain at the edge parts of the side plates when cutting the edge parts of the rod lens array together with the side plates in a state in which the rod lens array is arranged between a pair of side plates. When the chips, etc., adhere to the end faces of the rod lens array, there was a problem that a stable optical performance could not be achieved.

The present invention aims to provide a rod lens array unit capable of achieving a stable optical performance, a production method of the rod lens array unit, an LED print head including the rod lens array unit, an image sensor head including the rod lens array unit, an image forming apparatus including the LED print head, and an image reader including the image sensor head.

SUMMARY

A rod lens array unit disclosed in the application includes at least a rod lens array that includes a plurality of rod lenses arranged in a line, each of the rod lenses having an optical axis extending in an optical axis direction, and a pair of side plate parts stacked so as to sandwich the rod lens array. Wherein, end faces of the side plate parts in the optical axis direction of the rod lens array are positioned inside an end face of the rod lens array in the optical axis direction. In the invention, the sandwiching by the side plate parts means that the side plate part may be in a physical-contact with the rod lens array, also may have one or more middle layers in a space created between the side plate part and the rod lens array. Putting other way, the side plate parts are directly or indirectly able to sandwiches the rod lens array.

An LED print head disclosed in the application includes a plurality of semiconductor light emitting element arrays, a board in which the semiconductor light emitting element arrays are arranged, the rod lens array unit discussed above, and a folder that holds the rod lens array unit and the board in a manner such that surfaces of the semiconductor light emitting element arrays are positioned at a focal position of the rod lens array provided in the rod lens array unit.

An image sensor head disclosed in the application includes a plurality of semiconductor light receiving element arrays, a board in which the semiconductor light receiving element arrays are arranged, the rod lens array unit discussed above; and a folder that holds the rod lens array unit and the board in a manner such that surfaces of the semiconductor light receiving element arrays are positioned at a focal position of the rod lens array provided in the rod lens array unit.

An image forming apparatus disclosed in the application includes the LED print heads discussed above.

An image reader disclosed in the application includes the image sensor head discussed above.

A method for producing a rod lens array unit disclosed in the application includes i) respectively fixing a first side face and a second side face of a rod lens array including a plurality of rod lenses to a first side plate and a second side plate with adhesive, ii) forming a first long notch that penetrates the first side plate, iii) forming a second long notch that penetrates the second side plate at a position corresponding to the first long notch; and, iv) cutting the rod lens array with a cutting width narrower than either a width of the first long notch or a width of the second long notch in the second long notch.

According to the rod lens array unit of the present invention, a stable optical performance can be achieved.

According to the LED print head of the present invention, a stable irradiation performance can be achieved.

According to the image sensor head of the present invention, a stable light receiving performance can be achieved.

According to the image forming apparatus of the present invention, a stable print quality can be achieved.

According to the image reader of the present invention, a stable image reading quality can be achieved.

According to the production method of the rod lens array unit of the present invention, a production method of a rod lens array unit capable of achieving a stable optical performance can be provided.

DETAILED DESCRIPTION OF EMBODIMENT(S)

<Structure of Rod Lens Array Unit101>

FIG. 1is a perspective view showing a rod lens array unit101according to Embodiment 1 of the present invention.FIG. 2is an enlarged perspective view showing a partial region A1of the rod lens array unit101shown inFIG. 1.

The rod lens array unit101as shown inFIG. 1andFIG. 2has a plane symmetry structure in which the plane passing through the optical axes of the plurality of rod lenses102ais a symmetrical plane. In the rod lens array unit101, the structures of both end sides of the rod lens array unit101in the shorter direction (optical axis direction) are the same. For this reason, only the structure of one end side will be explained and the explanation for the structure of the other end side will be omitted.

The rod lens array unit101includes a rod lens array102bincluding a plurality of rod lenses102a, and a first side plate103aand a second side plate103bas a pair of side plate parts stacked in a manner such that the rod lens array102bis sandwiched. The end faces of the first side plate103aand the second side plate103bin the optical axis direction of the rod lens array102bare positioned inside (inward of or within) the rod lens array102bthan the end faces of the rod lens array102bin the optical axis direction of the rod lens array102b.

The end face of the rod lens array102bforms a first principal surface102cand the end faces of the first side plate103aand the second side plate103bform second principal surfaces104c. The first principal surface102cand the second principal surfaces104care arranged on both sides of the rod lens array102bin the optical axis direction. The second principal surfaces104care positioned inside the first principal surface102cin the optical direction.

The rod lens array unit101has a stacked structure in which the rod lens array102bis fixed with an adhesive (filling adhesive) so that a first distance D1, which is a distance between the side face of the rod lens array102band the first side plate103a(second side plate103b), is maintained between the first side plate103aand the second side plate103b.

The rod lens array unit101includes an adhesive part102arranged between the first side plate103aand the second side plate103band fixing the rod lens array102band the first side plate103aand the second side plate103b.

The adhesive part102includes a filling adhesive layer104as a first adhesive layer. The filling adhesive layer104is a layer in which a filling adhesive as a first adhesive is filled in the space around the rod lens array102b. The filling adhesive layer104includes a first filling adhesive layer104aand a second filling adhesive layer104b.

The rod lens array102band the adhesive part102form a protruded part102dwhich protrudes outward in the optical axis direction of the rod lens array102bthan the second principal surface104c. The protruded parts102dare formed on both end sides in the shorter direction of the rod lens array unit101, and include the region from the first principal surface102cto the second principal surface104c. The distance (face spacing) between the first principal surface102cand the second principal surface104cin the shorter direction is shown as a second distance D3.

As shown inFIG. 2, the first principal surface102cis a surface including the end face of the rod lens array102bat both end sides in the shorter direction (optical axis direction of the rod lens array102b) of the rod lens array unit101and provided along the longer direction (Y) of the rod lens array unit101.

The second principal surface104cis a face provided along the longer direction of the rod lens array unit101on both end sides in the shorter direction of the rod lens array unit101. Specifically, the second principal surface104cis a surface including a portion of the end face of the rod lens array unit101in the shorter direction and the end face of the first side plate103ain the shorter direction of the rod lens array unit101. The second principal surface104cis also a surface including a portion of the end face of the rod lens array unit101in the shorter direction and the end face of the second side plate103bin the shorter direction of the rod lens array unit101. The width of the second principal surface104cis shown as D2.

The boundary of the first principal surface102cand the second principal surface104cis located within a range shown as the first distance D1.

The distance (face spacing) between the first principal surface102cand the second principal surface104cin the shorter direction is the second distance D3as described above. Since the second distance D3is D3>0, a step104dis formed on both sides of the rod lens array unit101in the shorter direction as a step part.

The width Z1between the first principal surfaces102cprovided on both sides of the rod lens array unit101in the shorter direction is a final finished width of the rod lens array unit101.

It is preferable that the first distance D1, which is a distance between the side face of the rod lens array102band the first side plate103a, and the first distance D1, which is a distance between the side face of the rod lens array102band the second side plate103bbe, for example, 0.1 mm≦D1≦1.0 mm. It is preferable that the second distance D3be, for example, 0 mm≦D3≦1.0 mm.

The rod lens array102bin which a plurality of rod lenses102aare arranged in an array (array form) has a refractive index distribution. For the rod lens102a, for example, plastic materials are used, and acrylic resins including methacrylate (MMA), polymethyl methacrylate (PMMA), etc., can be used. Further, in this specification, an “array” includes the meaning of a linear (or straight) arrangement, a curved (or waved) arrangement, a zigzag arrangement, etc.

For the first side plate103aand the second side plate103b, materials low in machinability are used, and for example, glass cloth epoxy resin, glass, ceramics, phenol resin, epoxy resin, acrylic resin, ABS resin (for example, an ABS resin in which glass fillers are added), etc., can be used.

In this specification, “materials low in machinability” refers to materials including materials in which the Vickers hardness is 100 HV or higher. Further, “materials low in machinability” is also referred to as “materials poor in machinability”.

It is preferable that the first side plate103aand the second side plate103bbe small in linear expansion coefficient for temperature and humidity. Specifically, it is preferable that the value of the linear expansion coefficient for temperature and humidity, etc., for the first side plate103aand the second side plate103bbe, for example, 15 ppm/° C. or lower. It is preferable that the water absorption rate of the first side plate103aand the second side plate103bbe, for example, 0.1% or lower.

For the filling adhesive forming the filling adhesive layer104(including the first filling adhesive layer104aand the second filling adhesive layer104b), for example, silicone adhesive, epoxy adhesive, urethane adhesive, etc., can be used. In this specification, “the filling adhesive” includes the first filling adhesive and the second filling adhesive.

However, even in the case of using any of the materials, it is preferable that the filling adhesive as the first adhesive has a curing shrinkage ratio of 3% or lower. That is to reduce the effects of the optical characteristics, etc., of the rod lens array102bwith the stress caused by the curing shrinkage. Further, it is preferable that the water absorption rate of the first filling adhesive layer104aand the second filling adhesive layer104bbe, for example, 0.1% or lower.

According to the rod lens array unit101of Embodiment 1, the end faces of the first side plate103aand the second side plate103bin the optical axis direction of the rod lens array102bare positioned inside the end face of the rod lens array102bin the optical axis direction of the rod lens array102b. This prevents dust, etc., adhered to the periphery of the rod lens array102b(for example, second principal surface104c) from adhering to the end face of the rod lens array102b, realizing a stable optical performance of the rod lens array unit101. The optical axis direction (or shorter direction) is shown with Y, the perpendicular direction (or longer direction) with respect to X is shown with X. X direction may be referred as a main scanning direction. The thick direction with respect to X and Y directions is shown with Z.

By using materials low in machinability or materials small in linear expansion coefficient for temperature and humidity for the first side plate103aand the second side plate103b, a rod lens array unit101small in size variation regardless of a change in operating environment (surrounding environment), such as, e.g., a change in temperature or a change in humidity, and a change in temperature from self-heating, can be provided.

<Production Method of Rod Lens Array Unit101>

Generally, for a rod lens constituting a rod lens array, there are a lens made of a glass material and a lens made of a plastic material. In the production method of the rod lens array using such a rod lens, since there may be variations in the position or the shape of the tips of the plurality of rod lenses in the optical axes arranged in a predetermined direction, the tips (end faces) of the rod lens parts of the rod lens arrays in the optical axis direction eventually need to be evenly leveled. Therefore, for example, in a rod lens array using rod lenses made of a glass material, the rod lens end faces are finished by polishing the tip of the rod lens part. Further, in a rod lens array made of a plastic material, for example, the finishing of the rod lens end faces is performed by cutting the tip of the rod lens using a linear cutter equipped with cutting blades.

The method for finishing the lens cross-section in which the tip of the rod lens made of a plastic material is cut using a linear cutter can simplify the production step in comparison to the method of finishing the rod lens cross-section in which the tip of the rod lens part made of a glass material is polished. Therefore, the production efficiency of the rod lens array can be improved by producing rod lens arrays using rod lenses made of a plastic material. However, when cutting the tips of the rod lenses of rod lens arrays using a linear cutter, in a conventional production method of rod lens array units, it was difficult to only cut the rod lens part of the rod lens array. Therefore, in some cases, the side plates, etc., arranged around the rod lens parts also had to be cut. Therefore, it is desirable that the side plates, etc., arranged around the rod lenses be constituted by a material that does not damage the cutting blade of the linear cutter.

For the side plate arranged around the rod lenses, a plate material, such as, e.g., phenol resin, ABS resin, epoxy resin, and acrylic resin, is used. In the case of using such material for the side plate, there was a problem that the dimensional variations in the rod lens array unit occurred due to the changes in the operation environment such as a change in humidity or a change in temperature.

Therefore, as explained in the aforementioned <Structure of Rod Lens Array Unit101>, by using a material low in machinability for the first side plate103aand the second side plate103b, the dimensional variations of the rod lens array unit101can be decreased regardless of the change in operational environment such as a change in humidity and a change in temperature.

However, when producing such a rod lens array unit101, in the finishing step of the rod lens end face using a linear cutter, it is desirable that damages to the cutting blade from contacting the material low in machinability (for example, side plate including glass materials) be avoided. Therefore, next, a production method of the rod lens array unit101in consideration of a case in which a material low in machinability are used for the first side plate103aand the second side plate103bwill be explained.

The method of producing the rod lens array unit101includes the following steps:

respectively fixing a first side face and a second side face of the rod lens array102bincluding a plurality of rod lenses102ato the first side plate103aas a first side plate and the second side plate103bas a second side plate with adhesive;

forming a slit107as a first long notch that penetrates the first side plate103a;

forming, at a position corresponding to the slit107, another slit107as a second long notch that penetrates the second side plate103b; and

cutting, in the slit107as a second long notch, the first side plate103a, the second side plate103b, and the rod lens array102bwith a cutting width D7narrower than a width D6of the first long notch and the width D6of the second long notch.

These steps will be specifically explained.

FIG. 3Ashows a first filling adhesive application step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 3Bis an enlarged perspective view showing a partial region A2of the first side plate103aand the first filling adhesive layer104aas shown inFIG. 3A.

As shown inFIG. 3AandFIG. 3B, a first filling adhesive is applied to the surface of the first side plate103ato form a first filling adhesive layer104a. It is desired that the first filling adhesive be in liquid form. It is desired that the film thickness D4of the first filling adhesive layer104abe set to be thicker (longer) than the first distance D1so that the first distance D1, which is the distance (interval) between the side face of the rod lens array102b(side faces of the plurality of rod lenses102a) and the first side plate103a, is secured. Further, it is preferable that the film thickness D4of the first filling adhesive layer104abe at a degree of a film thickness causing no gap between the outer circumferential surface of the rod lens array102band the first side plate103a.

FIG. 4Ashows a rod lens arrangement step of the production method of the rod lens array unit101according to Embodiment 1, andFIG. 4Bis an enlarged perspective view showing a partial region A3of the plurality of rod lenses102aarranged on the array board105shown inFIG. 4A.

As shown inFIG. 4AandFIG. 4B, a plurality of rod lenses102aare arranged on the array board105in which a plurality of grooves (ditches) are formed in a manner such that the array pitches P of the plurality of rod lenses102aare constant. The grooves of the array board105can be made by, for example, cutting or etching a board in which the main material is aluminum or glass, in consideration of the shapes and the dimensions of the rod lenses102a.

By arranging the plurality of rod lens102ain an orthogonal direction of each of the optical axes of the plurality of rod lenses102a, the rod lens array102bcan be obtained.

FIG. 5Ashows a rod lens bonding step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 5Bis an enlarged perspective view showing a partial region A3of the plurality of rod lenses102aadhered to the first filling adhesive layer104ashown inFIG. 5A.

A surface of the first side plate103ain which the first filling adhesive layer104ais formed is put in close contact with a side face (first side face) of the plurality of rod lenses102a(rod lens array102b) arranged on the array board105to adhere the rod lens array102bto the first filling adhesive layer104a.

When adhering the rod lens array102bto the first filling adhesive layer104a, for example, the first side plate103ais pressed using a pressing machine to press-bond the first filling adhesive layer104aand the rod lens array102b. When press-bonding, it is preferable that a load control and positioning be performed for the press-bonding so that the first distance D1between the rod lens array102band the inner surface of the first side plate103ais secured.

When the viscosity of the first filling adhesive layer104ais a low viscosity such as, for example, 10 [Pa·s] or lower, in this step c1, the first filling adhesive layer104amay be preheated to increase the viscosity of the first filling adhesive layer104aor to harden the first filling adhesive layer104a. By increasing the viscosity of the first filling adhesive layer104aor by hardening the first filling adhesive layer104a, the variations in the first distance D1and the pitch P in the later steps can be suppressed.

FIG. 6Ashows a rod lens transfer step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 6Bis an enlarged perspective view showing a partial region A5of the rod lens array102bfixed to the first side plate103aand the first filling adhesive layer104ashown inFIG. 6A.

By pulling up the first side plate103ato which the rod lens array102bis fixed from the array board105, the rod lens array102bis moved (transferred) onto the first filling adhesive layer104afrom the array board105. For the purpose of suppressing the variations in the first distance D1or the pitch Pin later steps, the first filling adhesive layer104amay be preheated in this step d1.

FIG. 7Ashows a second filling adhesive application step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 7Bis an enlarged perspective view showing a partial region A6of the second filling adhesive layer104bformed on the rod lens array102bshown inFIG. 7A.

A second filling adhesive is applied to the side face (second side face) of the rod lens array102bobtained in step d1 to form a second filling adhesive layer104b. It is preferable that the second filling adhesive be in liquid form. It is preferable that the film thickness D5of the second filling adhesive layer104bbe set to be thicker (longer) than the first distance D1so that the first distance D1between the rod lens array102band the second side plate103bis secured in the later step (step f1: second side plate adhering step) when the second side plate103band the rod lens array102bare fixed. Further, it is preferable that the film thickness D5of the second filling adhesive layer104bbe at a degree of a film thickness causing no gap between the rod lens array102band the second side plate103b.

FIG. 8Ashows a second side plate bonding step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 8Bis an enlarged perspective view showing a partial region A7of the rod lens array sheet100shown inFIG. 8A.

In Step f1, the side faces of the second filling adhesive layer104band the second side plate103bare adhered to produce the rod lens array sheet100.

When adhering the second side plate103band the second filling adhesive layer104b, it is desired that a load control and positioning be performed for the press-bonding so that the first distance D1between the rod lens array102band the inner surface of the second side plate103bis secured. When the viscosity of the second filling adhesive layer104bis a low viscosity such as, for example, 10 [Pa·s] or lower, in this step f1, the second filling adhesive layer104bmay be preheated to increase the viscosity of the second filling adhesive layer104bor to harden the second filling adhesive layer104b. By increasing the viscosity of the second filling adhesive layer104b, variations of the first distance D1can be suppressed.

FIG. 9Ashows a slit forming step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 9Bis an enlarged perspective view showing a partial region A8of the rod lens array sheet100shown inFIG. 9A.

For example, using an end mill106, a plurality of slits107each having a slit width D6and a depth D2are formed on both sides of the rod lens array sheet100(surfaces of the first side plate103aand the second side plate103b). The plurality of slits107are formed so that the pitches (widths Z2) of the plurality of slits107are constant along a direction parallel to the optical axis direction of the rod lens array102b. The slit width D6shows a length in a direction parallel to the optical axis direction of the rod lens array102b. The depth D2shows a length in a direction orthogonal to the optical axis direction of the rod lens array102b.

The slit width D6is set to be longer than a width D7, which is a cutting width when cutting the rod lens array sheet100in a later step (step h1: cutting step). The central position of the slit width D6is a cutting position of the rod lens array sheet100in a later step (step h1: cutting step).

The depth D2is a depth in which at least the first side plate103aand the second side plate103bare completely cut (penetrated) in the slit107and may be set to a degree of a depth causing no damage to the surface of the rod lens array102b. In other words, the depth D2is set to a depth in which the bottom part of the slit107is positioned within the range of the first distance D1.

The width Z2may be determined in consideration of the width D8for cutting and finishing the end face of the rod lens array102bin the optical axis direction in a later step (step h1: cutting step). Herein, the width Z2is determined from the center point of one slit width D6to the center point of another slit width D6in the optical axis direction (X).

FIG. 10Ashows a cutting step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 10Bis an enlarged perspective view showing a partial region A9of the cut rod lens array sheet100aas shown inFIG. 10A.

For example, using a dicing saw108, the rod lens array sheet100is cut so that the cut width is a width D7which is narrower than the slit width D6at the central position of the slit width D6formed in step g1. By cutting the rod lens array sheet100, both end faces (cross-sections) of the rod lens array102bin the optical axis direction are formed. The width D7may be set to a width (length) in which a cutting blade110fixed to a tip of a later explained cutter wheel109does not come in contact with the first side plate103aand the second side plate103bwhen the end face of the rod lens array102bin the optical axis direction is cut by a width D8in a later step (step i1: cutting step).

FIG. 11Ashows a cutting step in the production method of the rod lens array unit101according to Embodiment 1, andFIG. 11Bis an enlarged perspective view showing a partial region A10of the cut rod lens array sheet100aas shown inFIG. 11A.

Both of the end faces (cross-sections) in the optical axis direction of the rod lens array102bformed in step h1, for example, are cut only by the width D8using a cutting blade110to perform mirror finishing on both end faces of the rod lens array102bin the optical axis direction. By performing mirror finishing on both end faces of the rod lens array102bin the optical axis direction, the width Z1in the shorter direction of the rod lens array unit101is determined. The width D8may be determined in consideration of the width Z1at the time of the final finishing.

The rod lens array unit101is completed according to the aforementioned steps. In the production method of the rod lens array unit101explained above, an example in which a plurality of rod lenses102aare arranged in one line in the main scanning direction (direction that is orthogonal to the optical axes of the plurality of rod lenses102a) in one rod lens array unit101, but the number of the arrays of the plurality of rod lenses102ais not limited to one.

For example, when stacking two arrays of rod lens arrays102bin the main scanning direction, similarly to the method explained from step a1 to step d1, a plurality of rod lenses102aarranged as the first array is adhered to the first filling adhesive layer104a, and further, a plurality of rod lenses102aarranged as the second array is arranged on the first array of the plurality of rod lenses102a. When arranging the second array of the plurality of rod lenses102aon the first array of the plurality of rod lenses102a, the second array of the plurality of rod lenses102amay be stacked on the first array of the plurality of rod lenses102aso that the first array of the plurality of rod lenses102aand the second array of the plurality of rod lenses102aare arranged in a manner such that they are displaced by P/2 from each other in the main scanning direction.

After arranging the second array of the plurality of rod lenses102aon the first array of the plurality of rod lenses102a, the second filling adhesive layer104bis formed on the second array of the plurality of rod lenses102ain the same manner as in step e1, and the gap between the second array of plurality of rod lenses102ais filled with the second filling adhesive layer104b. For the purpose of adhesive-curing this stacked structure, the second filling adhesive layer104bmay be subjected to both of or one of heat processing and moisturizing. The following steps may be the same as step f1 to step i1.

According to the production method of the rod lens array unit101according to Embodiment 1, a filling adhesive layer104in which the first distance D1is secured between the rod lens array102b, and the first side plate103aand the second side plate103bis formed, so that damages to the side face of the rod lens array102bcan be suppressed when processing the slit on the first side plate103aand the second side plate103b(step g1).

Even when the first side plate103aand the second side plate103bincluding a material low in linear expansion coefficient for temperature and humidity or a material low in machinability is used for the rod lens array unit101, the slit processing (step g1) is performed so that both end faces of the first side plate103aand the second side plate103bin the optical axis direction of the rod lens array unit101are positioned inside both end faces of the rod lens array102bin the optical axis direction. Therefore, when performing mirror finishing (step i1) of both end faces of the rod lens array102bin the optical axis direction, damages to the cutting blade of the cutting apparatus (for example, linear cutter) can be suppressed.

<Structure of Rod Lens Array Unit201>

FIG. 12is a perspective view showing a rod lens array unit201according to Embodiment 2 of the present invention.FIG. 13is an enlarged perspective view showing a partial region A11of the rod lens array unit201shown inFIG. 12.

The rod lens array unit201as shown inFIG. 12andFIG. 13has a plane symmetry structure in which a plane passing through the optical axes of the plurality of rod lenses202ais a symmetrical plane. In the rod lens array unit201, since the structure of both end sides of the rod lens array unit201in the shorter direction are the same, only the structure of one end side will be explained and the explanation for the structure of the other end side will be omitted.

The rod lens array unit201includes a rod lens array202bincluding a plurality of rod lenses202aand a first side plate203aand a second side plate203bas a pair of side plate parts stacked in a manner such that the rod lens array202bis sandwiched. The end faces of the first side plate203aand the second side plate203bin the optical axis direction of the rod lens array202bare positioned inside the end faces of the rod lens array202bin the optical axis direction of the rod lens array202b.

The end faces of the rod lens array202bform a first principal surface202c, and the end faces of the first side plate203aand the second side plate203bform a second principal surface204c. The first principal surface202cand the second principal surface204care arranged on both sides of the rod lens array202bin the optical axis direction, and the second principal surface204cis positioned inside the first principal surface202cin the optical direction of the rod lens array202b.

The rod lens array unit201has a lamination structure in which a side face adhesive layer205aas a second adhesive layer (first side face adhesive layer) and a side face adhesive layer205bas a second adhesive layer (second side face adhesive layer) are stacked between the filling adhesive layer204(first filling adhesive layer204a) and the first side plate203aand between the filling adhesive layer204(second filling adhesive layer204b) and the second side plate203b, respectively. The side face adhesive layers205aand205bare made of a second adhesive, and the viscosity of the second adhesive before hardening is higher than the viscosity of the first adhesive forming the filling adhesive layer204before hardening. Further, in the example shown inFIG. 12andFIG. 13, both side faces of the rod lens array202bare adhered to the side face adhesive layers205aand205b, respectively.

The rod lens array unit201is provided between the first side plate203aand the second side plate203b, and has an adhesive part202for fixing the rod lens array202band the first side plate203aand the second side plate203b.

The adhesive part202includes a filling adhesive layer204as a first adhesive layer and side face adhesive layers205aand205bas second adhesive layers. The filling adhesive layer204is a layer in which a filling adhesive as a first adhesive is filled in the gap around the rod lens array202b. The filling adhesive layer204includes a first filling adhesive layer204aand a second filling adhesive layer204b. The side face adhesive layer205ais provided between the filling adhesive layer204(the first filling adhesive layer204a) and the first side plate203aand fixes the filling adhesive layer204(the first filling adhesive layer204a) and the first side plate203a. The side face adhesive layer205ais provided between the filling adhesive layer204(the second filling adhesive layer204b) and the second side plate203band fixes the filling adhesive layer204(the second filling adhesive layer204b) and the second side plate203b.

The rod lens array202band the adhesive part202form a protruded part202dwhich protrudes outward of the second principal surface204cin the optical axis direction of the rod lens array202b. The protruded part202dis formed on both end sides of the rod lens array unit201in the shorter direction and includes the region from the first principal surface202cto the second principal surface204c.

As shown inFIG. 13, the first principal surface202cis a surface including the end face of the rod lens array202bat both end sides in the shorter direction (optical axis direction of the rod lens array202b) of the rod lens array unit201, and is provided along the longer direction of the rod lens array unit201.

The second principal surface204cis a surface provided along the longer direction on both end sides of the rod lens array unit201in the shorter direction of the rod lens array unit201. Specifically, the second principal surface204cis a surface including a portion of the end face of the side face adhesive layer205aof the rod lens array unit201in the shorter direction and the end face of the first side plate203aof the rod lens array unit201in the shorter direction. The second principal surface204cis also a surface including a portion of the end face of the side face adhesive layer205bof the rod lens array unit201in the shorter direction and the end face of the second side plate203bof the rod lens array unit201in the shorter direction. The width of the second principal surface204cis shown as D2.

The boundary of the first principal surface202cand the second principal surface204cis located within the range shown as the first distance D1, which is a distance between the side face of the rod lens array202band the first side plate203a(second side plate203b).

The distance (face spacing) between the first principal surface202cand the second principal surface204cin the shorter direction is shown as a second distance D3. Since the second distance D3is D3>0, a step204dis formed on both sides of the rod lens array unit201in the shorter direction as a step part.

The rod lens array202bin which a plurality of rod lenses202aare arranged in an array has a refractive index distribution. For the rod lens202a, for example, plastic materials are used.

As the material for forming the side face adhesive layers205aand205b, for example, silicone adhesive, epoxy adhesive, urethane adhesive, etc., in liquid or dry film form may be used. It is preferable that the adhesive for forming the side face adhesive layers205aand205bhave a higher viscosity before hardening in comparison to the adhesive for forming the filling adhesive layer204, and for example, it is preferable that the viscosity before hardening be 10 [Pa·s]. The film thickness D1can may set as, for example, a thickness in the range of 0.1 mm to 1.0 mm. The materials used for the components other than the side face adhesive layers205aand205bof the rod lens array unit201may be the materials used for the components of Embodiment 1.

According to the rod lens array unit201of Embodiment 2, the end faces of the first side plate203aand the second side plate203bof the rod lens array202bin the optical axis direction are positioned inside the rod lens array202bthan the end face of the rod lens array202bin the optical axis direction of the rod lens array202b. This prevents dust, etc., adhered to the periphery of the rod lens array202b(for example, second principal surface204c) from adhering to the end face of the rod lens array202b, realizing a stable optical performance of the rod lens array unit201.

By using a material low in machinability or a material small in linear expansion coefficient for temperature and humidity for the first side plate203aand the second side plate203b, a rod lens array unit201small in size variation regardless of the changes in operating environment (surrounding environment) such as a change in temperature or a change in humidity, a change in temperature from self-heating, etc., can be provided.

<Production Method of Rod Lens Array Unit201>

Next, the production method of the rod lens array unit201will be explained.

The method of producing a rod lens array unit201includes the following steps:

respectively fixing a first side face and a second side face of a rod lens array202bincluding a plurality of rod lenses202ato a first side plate203aas a first side plate and a second side plate203bas a second side plate with adhesives;

forming a first long notch that penetrates the first side plate203a; a step for forming, at a position corresponding to the first long notch, a second long notch that penetrates the second side plate203b; and

for cutting, in the second long notch, the first side plate203a, the second side plate203b, and the rod lens array202bwith a cutting width narrower than the width of the first long notch and the width of the second long notch.

The production method of the rod lens array unit201further includes a step for applying a first adhesive (a first filling adhesive and a second filling adhesive) to the rod lens array202band a step for applying a second adhesive to the first side plate203aand the second side plate203b. These steps will be specifically explained.

<Step a2: First Side Face Adhesive Layer Forming Step>

FIG. 14Ashows a first side face adhesive layer forming step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 14Bis an enlarged perspective view showing a partial region A12of the first side plate203ain which the side face adhesive layer205aas shown inFIG. 14Ais formed.

As shown inFIG. 14AandFIG. 14B, by applying an adhesive (second adhesive) in liquid form or laminating an adhesive (second adhesive) in dry film form to the first side plate203a, a side face adhesive layer205a(first side face adhesive layer) with a film thickness D1is formed.

FIG. 15Ashows a first filling adhesive application step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 15Bis an enlarged perspective view showing a partial region A13of the first filling adhesive layer204aformed on the first side plate203aand the side face adhesive layer205ashown inFIG. 15A.

A first filling adhesive as a first adhesive is applied on the side face adhesive layer205aon the first side plate203aobtained in step a2 to form a first filling adhesive layer204a. It is desired that the first filling adhesive be in liquid form. It is desired that the film thickness D4of the first filling adhesive layer204ais at a degree of a film thickness causing no gap between the rod lens array202band the side face adhesive layer205ain a later step (step d2: rod lens bonding step).

FIG. 16Ashows a rod lens arrangement step of the production method of the rod lens array unit201according to Embodiment 2, andFIG. 16Bis an enlarged perspective view showing a partial region A14of the plurality of rod lenses202aarranged on the array board206shown inFIG. 16A.

As shown inFIG. 16AandFIG. 16B, a plurality of rod lenses202aare arranged on the array board206in which a plurality of grooves (grooves) are formed in a manner such that the array pitches P of the plurality of rod lenses202aare constant. The grooves of the array board206can be made by, for example, cutting or etching the board in which the main material is aluminum or glass, in consideration of the shapes and the dimensions of the rod lenses202a.

FIG. 17Ashows a rod lens bonding step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 17Bis an enlarged perspective view showing a partial region A15of a part of the plurality of rod lenses202aadhered to the first filling adhesive layer204ashown inFIG. 17A.

A surface of the first side plate203ain which the first filling adhesive layer204ais formed is put in close contact with the plurality of rod lenses202aarranged on the array board206(the rod lens array202b) to fill the first filling adhesive in the gap around the rod lens array202bto perform press-bonding so that the side face adhesive layer205acomes in direct contact with the side face of the rod lens array202b(the first side face).

When press-bonding, it is preferable that a load control and positioning be performed for the press-bonding so that the first distance D1formed between the rod lens array202band the first side plate203aby the side face adhesive layer205aas a spacer is secured.

When the viscosity of the first filling adhesive layer204ais a low viscosity such as, for example, 10 [Pa·s] or lower, in this step d2, the first filling adhesive layer204amay be preheated to increase the viscosity of the first filling adhesive layer204aor to harden the first filling adhesive layer204a. By increasing the viscosity of the first filling adhesive layer204aor by hardening the first filling adhesive layer204a, the variations in the array pitch P in the later steps can be suppressed.

FIG. 18Ashows a rod lens transfer step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 18Bis an enlarged perspective view showing a partial region A16of the rod lens array202bfixed to the first side plate203aand the first side face adhesive layer205ashown inFIG. 18A.

By pulling up the first side plate203ain which the rod lens array202bis fixed from the array board206, the rod lens array202bis moved (transferred) onto the side face adhesive layer205afrom the array board206. To suppress the variations in the array pitch P in later steps, the first filling adhesive layer204aor the side face adhesive layer205amay be preheated in this step e2.

FIG. 19Ashows a second filling adhesive application step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 19Bis an enlarged perspective view showing a partial region A17of the second filling adhesive layer204bformed on the rod lens array202bshown inFIG. 19A.

A second filling adhesive as a first adhesive is applied to the side face (second side face) of the rod lens array202bobtained in step e2 to form a second filling adhesive layer204b. It is preferable that the second filling adhesive be in liquid form. It is preferable that the film thickness D5of the second filling adhesive layer204bbe set to be a degree of a film thickness causing no gap between the rod lens array202band the side face adhesive layer205bin a later step (step h2: second side plate bonding step) when the second side plate203band the rod lens array202bare fixed.

<Step g2: Second Side Face Adhesive Layer Forming Step>

FIG. 20Ashows a second side face adhesive layer forming step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 20Bis an enlarged perspective view showing a partial region A18of the second side plate203bin which the side face adhesive layer205bas shown inFIG. 20Ais formed.

As shown inFIG. 20AandFIG. 20B, by applying an adhesive (second adhesive) in liquid form or laminating an adhesive (second adhesive) in dry film form on the second side plate203b, a side face adhesive layer205b(second side face adhesive layer) with a film thickness D1is formed.

<Step f2: Second Side Plate Bonding Step Step>

FIG. 21Ashows a second side plate bonding step in the production method of the rod lens array unit201according to Embodiment 2, andFIG. 21Bis an enlarged perspective view showing a partial region A19of the rod lens array sheet200shown inFIG. 21A.

In Step h2, the second filling adhesive layer204band the side face adhesive layer205bon the second side plate203bare adhered to produce the rod lens array sheet200. Specifically, the second filling adhesive layer204bobtained in step f2 and a surface of the second side plate203bin which the side face adhesive layer205bis provided are arranged so as to face each other, and the second side plate203bis pressed (press-bonded) so that the side face adhesive layer205bcomes in direct contact with the rod lens array202b. With the press-bonding, the first filling adhesive and the second filling adhesive are filled around the rod lens array202b, and the rod lens array202bin which the first filling adhesive and the second adhesive are filled is sandwiched and fixed to the surfaces of the first side plate203aand the second side plate203bin which the second adhesive is applied.

When press-bonding, it is desired that a load control and positioning be performed for the press-bonding so that the first distance D1, which is formed by the side face adhesive layer205bas a spacer between the rod lens array202band the second side plate203b, is secured. After completing the step h2, the stacked structure (rod lens array sheet200) obtained in step h2 is subjected to either or both of a heat treatment and a humidifying treatment to perform curing and bonding.

Further, the rod lens array unit201may be produced by executing similar processing as the processing in <step g1: slit forming step>, <step h1: cutting step>, and <step i1: machining step> explained in Embodiment 1.

In the slit forming step of Embodiment 1, the depth D2of the slit of the rod lens array unit101is set to a depth in which the bottom part of the slit107is positioned within the range of the first filling adhesive layer104aand the second filling adhesive layer104b. However, in the slit forming step of Embodiment 2, the depth of the slit formed in the rod lens array unit201is set as a depth in which the bottom part of the slit is positioned within the range of the side face adhesive layer (that is, the side face adhesive layer205aor205b).

The rod lens array unit201is completed by the aforementioned steps. In the production method of the rod lens array unit201explained above, an example was explained, in which a plurality of rod lenses202aare arranged in one array in the main scanning direction (direction that is orthogonal to the optical axes of the plurality of rod lenses202a) in one rod lens array unit201. However, the number of the arrays of the plurality of rod lenses202ais not limited to one array.

For example, when stacking two arrays of the rod lens arrays202bin the main scanning direction, based on the method explained in step a2 to step e2, a plurality of rod lenses202aarranged as a first array is arranged on the side face adhesive layer205, and similarly, a plurality of rod lenses202aarranged as a second array is arranged on the side face adhesive layer205b. The rod lens array202bon the side face adhesive layer205aand the rod lens array202bon the side face adhesive layer205bare arranged so as to face each other so that the first plurality of rod lenses202aand the second plurality of rod lenses202aare arranged in a manner as to be displaced by P/2 in the main scanning direction, and the filling adhesive may be filled between each of the rod lens arrays202bto stack the two rod lens arrays202b.

According to the production method of the rod lens array unit201relating to Embodiment 2, by securing the first distance D1between the rod lens array202b, and the first side plate203aand the second side plate203b, damages to the side face of the rod lens array202bcan be suppressed when processing the slit on the first side plate103aand the second side plate203.

Even when using the first side plate203aand the second side plate203bincluding materials small in linear expansion coefficient for temperature and humidity or materials low in machinability for the rod lens array unit201, since the slit processing is performed so that both end faces of the first side plate203aand the second side plate203bof the rod lens array unit201in the optical axis direction are positioned inside both end faces of the rod lens array202bin the optical axis direction, when performing mirror finishing on both end faces of the rod lens array202bin the optical axis direction, damages to the cutting blade of the cutting device (for example, linear cutter) can be suppressed.

Since the side face adhesive layer205ais formed between the first filling adhesive layer204aand the first side plate203ausing an adhesive higher in viscosity (viscosity) than the adhesive forming the first filling adhesive layer204a, when fixing the rod lens array202band the first side plate203a, the variations of the first filling adhesive layer204and the side face adhesive layer205aon the first side plate203acan be reduced, and the arrangement of the rod lens array202bcan be stably performed.

The diameter Φ of the rod lens varies according to the size of apparatus. In a case of the embodiments shown in the application, the preferred range of the diameter Φ is from 0.3 mm to 1.0 mm (inclusive). Additionally, the first distance D1is preferred to be from 0.1 mm to 1.0 mm, thereby the ratio of D1/Φ being preferably ranged from 0.1 to 3.3 (inclusive). The second distance D3is preferred to be from 0.05 mm to 1.0 mm, thereby the ratio of D3/Φ being preferably ranged from 0.05 to 3.3 (inclusive). Here, the first distance D1may be defined as a gap between the side face of the rod lens array and the side plate part in the thick direction. Simply, it may be calculated by a formula of (D9−Φ)/2. The D9means a thickness of the filling adhesive layer104in the thick direction (Z). SeeFIG. 8B. The second distance D3may be defined as a protrusion distance from the second principal surface104cin the optical axis direction.

<Structure of LED Print Head600>

FIG. 22is a perspective view showing an LED print head600according to Embodiment 3 of the present invention.FIG. 23is an enlarged perspective view showing the structure of the LED print head600including the cross-sectional configuration of the LED print head600shown inFIG. 22taken along a line segment C60-C-60. The LED print head600is used as, for example, an exposure device for exposing a surface of a photosensitive drum in an image forming apparatus such as a printer.

The LED print head600includes a plurality of semiconductor light emitting element arrays611, a COB (Chip On Board)612as a board (print wiring board) in which a plurality of semiconductor light emitting element arrays611is arranged linearly by die bonding, a rod lens array unit601, and a folder609for holding the rod lens array unit601and the COB612. The plurality of semiconductor light emitting element arrays611on the COB612is not limited to the linearly arranged configuration, and may be arranged in a zigzag manner on the COB612.

For the rod lens array unit601, any one of the rod lens array units101,201,301,401, and501explained in Embodiments 1 to 5 may be utilized. Therefore, the rod lens array units601and the rod lens arrays602as shown inFIG. 22andFIG. 23, depending on any one of the rod lens array units101,201,301,401, and501utilized for the rod lens array unit601, corresponds to any of the rod lens arrays102b,202b,302b,402b, and502b.

The semiconductor light emitting element array611is a chip in which a plurality of semiconductor light emitting elements such as LEDs (light emitting diodes) are arranged, and is, for example, a LED array chip. The rod lens array unit601and the COB612are adhered to the folder609using, for example, an ultraviolet curing type adhesive.

The rod lens array unit601and the COB612are fixed to the folders609so that the light emitting surfaces of the plurality of semiconductor light emitting element arrays611are positioned at a position (focal position) which is distant only by the focal length of the rod lens array602including the plurality of rod lenses provided in the rod lens array unit601. That is, the rod lens array unit601and the COB612are fixed to the folder609at a position in which the distance L1between the surface of the rod lens array602in the optical axis direction and the light emitting surfaces of the plurality of the semiconductor light emitting element arrays611is equal to the focal length of the rod lens array602. It is preferable that the rod lens array unit601be adhered to the folder609so that, when the LED print head600is assembled into an image forming apparatus such as a printer, the distance between the surface of the rod lens array602in the optical axis direction and a photosensitive drum surface is equal to the focal length of the rod lens array602.

A hole610as a positioning part is formed at a predetermined position near both ends of the top face of the folder609in the longitudinal direction. The hole610can be used for, for example, the positioning to determine the relative position of the LED print head600with respect to a printer main body configuration when mounting the LED print head600in an image forming apparatus such as a printer.

The sealing material613is arranged in the gap between the rod lens array unit601and the folder609, and the gap between the COB612and the folder609to prevent contaminants such as toners from entering into the folder609. As the sealing material613, for example, silicone is used.

In the LED print head600, the light emitted by the semiconductor light emitting element array611is collected by the rod lens array unit601to expose the irradiation target surface (for example, photosensitive drum surface). For example, when the LED print head600is mounted in an image forming apparatus such as a printer, the LED print head600irradiates light corresponding to the image data input in the image forming apparatus and forms the electrostatic latent image on the surface of the photosensitive drum.

According to the LED print head600of Embodiment 3, since any one of the rod lens array units101,201,301,401, and501explained in Embodiments 1 to 5 may be utilized for the rod lens array unit601, a stable irradiation performance can be realized.

By using a material small in machinability or a material small in linear expansion coefficient for temperature and humidity for the side plate of the rod lens array unit601, the variations in the relative positional relationship of the rod lens array unit601and the semiconductor light emitting element array611can be suppressed regardless of the changes in the operating environment such as a change in temperature or a change in humidity, or a change in temperature from self-heating from the COB612.

Furthermore, even when the sealing material613deforms due to the temperature change, etc., in the surrounding environment, the adherence of the sealing materials613to the end face of the rod lens array602can be reduced since steps as step parts are formed on both sides of the rod lens array units601in the shorter direction.

<Structure of Contact Image Sensor Head700>

FIG. 24is a perspective view showing a contact image sensor head700as an image sensor head of Embodiment 4 of the present invention.FIG. 25is an enlarged perspective view showing the structure of the contact image sensor head700including the cross-sectional configuration of the contact image sensor head700shown inFIG. 24taken along the line segment C62-C-62. The contact image sensor head700as an image sensor head, for example, can be used as a reader for receiving reflected light from mediums when light is irradiated by a medium in an image reader such as an image scanner.

The contact image sensor head700includes a plurality of semiconductor light receiving element arrays703, a COB (Chip On Board)704as a board (print wiring board) in which a plurality of semiconductor light receiving element arrays703are arranged linearly by die bonding, a light guiding body705in which light sources are arranged inside, a rod lens array unit701, and a folder707for holding the rod lens array unit701and the COB704.

For the rod lens array unit701, any one of the rod lens array units101,201,301,401, and501explained in Embodiments 1 to 3 may be utilized. Therefore, the rod lens arrays702of the rod lens array units701shown inFIG. 24andFIG. 25correspond to any of the rod lens arrays102band202bdepending on any one of the rod lens array units101and201applied to the rod lens array unit701,

The semiconductor light receiving element array703is a chip in which a plurality of light receiving elements for sensing reflected light from mediums such as manuscripts and converting it into electric signals is arranged. The rod lens array unit701and the COB704are, for example, adhered to the folder707using an ultraviolet curing type adhesive. The rod lens array unit601and the COB704are fixed to the folders707so that the light receiving surfaces of the plurality of semiconductor light receiving element arrays703are positioned at a position (focal position) which is distant only by the focal length of the rod lens array702including the plurality of rod lenses provided in the rod lens array unit701. That is, the rod lens array unit701and the COB704are fixed to the folder707at a position in which the distance L2between the surface of the rod lens array702in the optical axis direction and the light emitting surfaces of the plurality of the semiconductor light receiving element arrays703is equal to the focal length of the rod lens array702. Further, it is preferable that the rod lens array unit701be adhered to the folder707so that, when the contact image sensor head700is assembled into an image reader such as a scanner, the distance between the surface of the rod lens array702in the optical axis direction and a manuscript provided on a platen is equal to the focal length of the rod lens array702.

Further, the example of the contact image sensor head700is not limited to the example shown inFIG. 24andFIG. 25. For example, a sealing material for preventing contaminants such as dust from entering into the folder707may be arranged in the gap between the rod lens array unit701and the folder707, and the gap between the COB704and the folder707. As the sealing material, silicone is used, for example.

The contact image sensor head700, when it is assembled into an image reader such as a scanner, reads a manuscript when a light source arranged inside the light guiding body705emits light. The rod lens array unit701collects the reflected light from the manuscript, and the semiconductor light receiving element array703receives the light.

According to the contact image sensor head700of Embodiment 4, since any one of the rod lens array units101and201explained in Embodiments 1 and 2 is applied to the rod lens array unit701, a stable light receiving performance can be realized.

Further, by using materials small in machinability or materials small in linear expansion coefficient for temperature and humidity for the side plate of the rod lens array unit701, the variations in the relative positional relationship of the rod lens array unit701and the semiconductor light receiving element array703can be suppressed regardless of the changes in operating environment such as a change in temperature or a change in humidity, or a change in temperature from self-heating from the COB704.

Further, since a step is formed as a step part on both sides of the rod lens array unit701in the shorter direction, the rod lens array unit701can be stably fixed to the folder707.

<Structure of LED Printer800>

FIG. 26is a cross-sectional view showing a structure of an LED printer800as an image forming apparatus according to Embodiment 5 of the present invention. The LED printer800is a printer in which the LED print head600explained in Embodiment 3 is applied to an exposure device.

The LED printer800as an image forming apparatus forms a black and white image or a color image with an electrographic system using yellow (Y), magenta (M), cyan (C), and black (K) developers. The LED printer800is provided with four process units802Y,802M,802C, and802K corresponding to each of the colors, yellow (Y), magenta (M), cyan (C), and black (K). Each of the process units802Y,802M,802C, and802K are arranged in parallel along the carrying path806of a recording medium804such as a sheet, etc.

Each of the process units802Y,802M,802C, and802K includes a photosensitive drum80as an image carrier, a charging device810for charging the surface of the photosensitive drum808and arranged around the photosensitive drum808, and an exposure device812forming electrostatic latent images on the surface of the charged photosensitive drum808by irradiating light corresponding to the externally inputted image data. For the exposure device812, the LED print head600explained in Embodiment 3 is utilized.

Each of the process units802Y,802M,802C, and802K is further provided with a developing device814for supplying toner as a developer to the surface of the photosensitive drum808on which the electrostatic latent images are formed, and a cleaning device816for removing the toners remaining on the surface of the photosensitive drum808. Further, the photosensitive drum808rotates in the arrow direction by receiving a driving force from a drive mechanism constituted by a drive source, gears, etc.

Furthermore, the LED printer800includes a sheet cassette818for storing recording mediums804such as sheets, etc., and a hopping roller820for separating and carrying the recording mediums804one by one. On the downstream side of the hopping roller820in the carrying direction of the recording medium804, pinch rollers822aand822band registration rollers824aand824bfor carrying the recording medium804toward the process units802Y,802M,802C, and802K by correcting the skew of the recording medium804, are provided, sandwiching the recording medium804with the pinch rollers822aand822b. The hopping roller820and the registration rollers824aand824brotate interlocking with the drive source such as a motor, gears, etc.

The LED printer800is further provided with a transfer roller826arranged so as to face each of the photosensitive drums808in each of the process units802Y,802M,802C, and802K. The transfer roller826is constituted by a semiconductive rubber, etc. The LED printer800is provided with a fuser device834, ejection rollers828a,828b,830a, and830b, and a stacker832.

In the LED printer800, the electrical potential of the photosensitive drum808and the electrical potential of the transfer roller826are set so that the toner image formed on the photosensitive drum808is transferred to the recording medium804.

The recording medium804loaded in the sheet cassette818is separated and carried one by one by the hopping roller820. The recording medium804supplied from the sheet cassette818passes through the registration rollers824aand824b, and the pinch rollers822aand822bto sequentially pass between the photosensitive drum808and the transfer roller826in each of the process units802Y,802M,802C, and802K. The recording medium804passes between the photosensitive drum808and the transfer roller826in each of the process units802Y,802M,802C, and802K, and the toner images of each color are sequentially transferred to the recording medium804, and then heat or pressure is applied by the fuser device834to fuse the toner images of each color on the recording medium804. The recording medium804in which toner images are fused is ejected to the stacker832by the ejection rollers828a,828b,830a, and830b.

Further, the example of the LED printer800shown inFIG. 26shows a configuration example in a case in which printing is performed only on one side of the recording medium804, but a sheet reversing device to be used for reversing the recording medium804when printing on both faces of the recording medium804may also be provided.

According to the LED printer800of Embodiment 5, since the LED print head600explained in Embodiment 3 is used as the exposure device812, stable print quality can be realized.

<Structure of Image Scanner900>

FIG. 27is a perspective view showing an exterior of an image scanner as an image reader according to Embodiment 6. The image scanner900is a contact image scanner that is a flat bed type to which the contact image sensor head700illustrated in Embodiment 4 is applied.

As shown inFIG. 27, the image scanner900as an image reader includes a housing902, a platen904on which a manuscript is placed and a cover906(or platen cover) that presses the manuscript placed on the plater904downwardly from the upside. Inside the housing902, the contact image sensor head700, guides908aand908b, a stepping motor910, a drive belt912, a control circuit914and a flexible flat cable916are arranged.

The contact image sensor head700is supported such that the head is linearly movable along the pair of the guides908aand908bfixed to the housing902. In order to allow the contact image sensor head700to slide along the guides908aand908bin the sub scanning direction (or not main direction), the contact image sensor head700is connected to the drive belt912connected to the stepping motor910. The control circuit914for controlling the image sensor head700makes wire connections to the contact image sensor head700through the flexible flat cable916.

With the image scanner900according to Embodiment 6, the contact image sensor head700illustrated in Embodiment 4 can be used, thereby realizing secure image reading quality.