Bookbinding apparatus that creates book by bonding a plurality of sheets using toner

A bookbinding apparatus comprising:

• a first photosensitive member;
• a first light source that forms a first electrostatic latent image corresponding to an original area and a second electrostatic latent image corresponding to an adhesive area by irradiating the first photosensitive member with light;
• a first developing member that forms a first toner image and a second toner image by developing the first electrostatic latent image and the second electrostatic latent image using toner in a first color;
• a first primary transferring member that transfers the first toner image and the second toner image formed by the first developing member to an intermediate transfer member;
• a second photosensitive member;
• a second light source that forms a third electrostatic latent image corresponding to the original area and a fourth electrostatic latent image corresponding to the adhesive area by irradiating the second photosensitive member with light;
• a second developing member that forms a third toner image and a fourth toner image by developing the third electrostatic latent image and the fourth electrostatic latent image using toner in a second color;
• a second primary transferring member that transfers the third toner image and the fourth toner image formed by the second developing member to the intermediate transfer member;
• a secondary transferring member that transfers the first toner image, the second toner image, the third toner image, and the fourth toner image from the intermediate transfer member to a sheet;
• a fixing unit that fixes the first toner image, the second toner image, the third toner image, and the fourth toner image to the sheet;
• and
• a bonding unit that creates a book by bonding a plurality of sheets on which the first toner image, the second toner image, the third toner image, and the fourth toner image have been formed with use of the second toner image and the fourth toner image,
• wherein
• an irradiation amount of the light for forming the second electrostatic latent image is larger than an irradiation amount of the light for forming the first electrostatic latent image,
• wherein the first light source includes
• a first light emitting element, and
• a first optical system that directs light output from the first light emitting element to a surface of the first photosensitive member,
• wherein, in a scanning direction of the light that is parallel to a rotation axis of the first photosensitive member, the first optical system has a first image height defined as a position in the scanning direction within a first image formation range extending from a writing start position to a writing end position of the light on the surface of the first photosensitive member, the first image height representing a coordinate along the scanning direction that increases from the writing start position toward the writing end position,
• wherein a first peak position at which an optical efficiency of the first optical system between the first light emitting element and the surface of the first photosensitive member peaks in the scanning direction is located between (i) a center position of the first image height of the first image formation range and (ii) a surface area on the first photosensitive member in which the second electrostatic latent image is formed,
• wherein the second light source includes
• a second light emitting element, and
• a second optical system that directs light output from the second light emitting element to a surface of the second photosensitive member, and
• wherein, in a scanning direction of the light that is parallel to a rotation axis of the second photosensitive member, the second optical system has a second image height defined as a position in the scanning direction within a second image formation range extending from a writing start position to a writing end position of the light on the surface of the second photosensitive member, the second image height representing a coordinate along the scanning direction that increases from the writing start position toward the writing end position, and
• wherein a second peak position at which an optical efficiency of the second optical system between the second light emitting element and the surface of the second photosensitive member peaks in the scanning direction is located between (i) a center position of the second image height of the second image formation range and (ii) a surface area on the second photosensitive member in which the fourth electrostatic latent image is formed.