JP2000218856A - Optical printer head - Google Patents

Abstract

(57) Abstract: An optical printer head capable of obtaining a good continuous latent image in the main scanning direction even when the temperature of a lens changes. A plurality of light emitting element array chips on which a large number of light emitting elements are linearly arranged are provided on a base plate.
A plurality of lenses 3 corresponding to the light emitting element array chips 2 are disposed one-to-one with the light emitting element array chips 2 above the base plate 1, and light from the light emitting elements of the light emitting element array chips 2 is arranged above the base plate 1. In an optical printer head that forms a latent image by forming an image via the lens 3,
A transparent plate 5 having the same directionality as the lens 3 and the refractive index temperature dependency is provided between the light emitting element array chip 2 and the corresponding lens 3 in a state where the transparent plate 5 is not in contact with all the light emitting element array chips 2. It is arranged in.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printer head such as an LED printer head incorporated as an exposure means in an electrophotographic printer or the like.

[0002]

2. Description of the Related Art A conventional optical printer head is, for example, shown in FIG.
As shown in the figure, on the upper surface of the base plate 11 on which a predetermined circuit pattern is formed, a plurality of light emitting element array chips 12 in which a large number of light emitting elements are arranged at regular intervals, linearly arranged and mounted, It has a structure in which a plurality of lenses 13 are arranged above the chip 12 in one-to-one correspondence with the light emitting element array chip 12, and the light emitting elements of the light emitting element array chip 12 are provided with image data from the outside. And selectively emit light on the basis of the external photoconductor P via the corresponding lens 13.
And forms a predetermined latent image on the photoconductor P to function as an optical printer head.

[0003] In such a conventional optical printer head, a certain interval is provided between adjacent light emitting element array chips 12-12. Therefore, if the light from the light emitting element array chips 12 is directly irradiated on the photoconductor P, an area where the light is not irradiated is formed on the surface of the photoconductor P. By irradiating them in a line on the photoconductor P, a latent image continuous in the main scanning direction (the arrangement direction of the light emitting element array chips 12) is formed.

[0004]

In order to obtain a good continuous latent image in the main scanning direction by using the above-described conventional optical printer head, all the light emitting element array chips 12 are fixed on the base plate 11. In addition to being arranged at intervals, the lens 13 must be positioned with extremely high accuracy (mounting accuracy: within ± 5 μm) with respect to each light emitting element array chip 12.

However, in the above-described conventional optical printer head, the lens 13 is formed of an acrylic resin, a polycarbonate resin, or the like, and the lens 13 formed of these materials has a negative refractive index temperature dependency. ing.
Therefore, when the temperature of the lens 13 rises due to the use of the optical printer head or heat transfer from a device disposed around the optical printer head, the imaging magnification is increased due to the decrease in the refractive index of the lens 13, As a result, the latent images of the adjacent light emitting element array chips 12 partially overlap each other, and black streaks of the print are generated. On the other hand, when the lens 13 is used under extremely low temperature conditions, the imaging magnification is reduced due to the increase in the refractive index of the lens 13, and as a result, continuous imaging in the main scanning direction occurs. However, there is a disadvantage that the printed latent image cannot be obtained and white streaks of the printed image occur.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an optical printer head according to the present invention has a light emitting element array chip in which a large number of light emitting elements are linearly arranged on a base plate. A plurality of lenses are arranged in a row, and a plurality of lenses corresponding to the light emitting element array chip in a one-to-one correspondence are disposed above the base plate, and light from the light emitting elements of the light emitting element array chip is provided. In an optical printer head for forming a latent image by forming an image through the lens, a transparent plate having the same refractive index and temperature dependency as the refractive index between the light emitting element array chip and the corresponding lens. Are arranged in a non-contact state with respect to all the light emitting element array chips.

In the optical printer head of the present invention, a plurality of light emitting element array chips in which a large number of light emitting elements are linearly arranged are arranged in a row on a base plate, and the light emitting elements are arranged above the base plate. In an optical printer head, a plurality of lenses corresponding to the array chip are provided in one-to-one correspondence, and a latent image is formed by forming light of the light emitting element of the light emitting element array chip through the lens. Between the lens and the image plane,
It is characterized in that a transparent plate having a directionality having a different refractive index temperature dependency from the lens is provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a configuration of an optical printer head according to one embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining a light path of the optical printer head of FIG.
Denotes a base plate, 2 denotes a light emitting element array chip, 3 denotes a lens, and 5 denotes a transparent plate.

The base plate 1 is made of, for example, glass or ceramic material, and has a predetermined pattern of circuit wiring (not shown) attached and formed on the upper surface thereof.

The base plate 1 serves as a supporting base material for supporting the circuit wiring and the light emitting element array chip 2 described above. For example, when the base plate 1 is made of glass, a plate having a predetermined thickness is formed by a conventionally known floating method or the like. It is manufactured by forming a body and cutting and processing it into a predetermined rectangular shape.

A plurality of light emitting element array chips 2 are arranged and mounted on the upper surface of the base plate 1 with a predetermined interval therebetween.

The light emitting element array chip 2 has a large number of light emitting elements 2a linearly arranged on the upper surface thereof. When power is supplied from an external power supply in accordance with driving of a driver IC (not shown). Each of the light emitting elements 2a selectively emits light individually based on the image data. The light emitted from the light emitting element 2a is transmitted to an external photoconductor P through a lens 3 described later.
Is irradiated.

As such a light emitting element array chip 2, for example, 128 light emitting diode elements (light emitting elements)
LED array chips or the like in which are linearly arranged are used.
Is heated to a high temperature in a furnace, and AsH ₃ and P
A gas containing an appropriate amount of H ₃ and Ga is brought into contact with the substrate surface to form n.
GaAsP single crystal of type semiconductor is grown and then GaAs
A window film of Si ₃ H ₄ is deposited on the surface of the sP single crystal, and the window hole is exposed to a gas of Zn to form n-type semiconductor GaAs.
It is manufactured by diffusing Zn into a part of the sP single crystal to form a p-type semiconductor and having a pn junction.

For example, in the case of forming an A4 size, 600 dpi optical printer head, four 850 dpi light emitting element array chips 2 each having 128 light emitting elements 2a as one unit.
And the terminals (not shown) of the light emitting element array chip 2 and the circuit wiring of the base plate 1 are connected to a connection member (not shown) such as a solder or a thin metal wire. The light emitting element array chip 2 is mounted on the upper surface of the base plate 1 by bonding using a not shown). In this case, the pitch of the light (beam) irradiated on the photoconductor P is 42.3 μm.

Above the base plate 1 on which the light emitting element array chips 2 are mounted, a plurality of lenses 3 corresponding to the light emitting element array chips 2 one by one are arranged.

The lens 3 is arranged so that its optical axis is located substantially at the center of the corresponding light emitting element array chip 2. The light from the light emitting element array chip 2 is enlarged at a predetermined magnification, and Acts to illuminate and image P.

The lenses 3 are manufactured by injection molding a transparent resin such as an acrylic resin or a polycarbonate resin, or by press-molding a transparent inorganic material such as glass, and held on a lens plate 4a. In this state, it is supported and fixed at a position separated from the light emitting element array chip 2 by a predetermined distance. The lens plate 4a is manufactured by injection molding a plastic material such as a liquid crystal polymer.

A lens 3 is provided between the lens 3 and the light emitting element array chip 2 corresponding to the lens 3.
If the transparent plate 5 having the same refractive index temperature dependency in the same direction as the definition (the definition: the rate of change of the refractive index with temperature change), that is, the refractive index temperature dependency of the lens 3 is a negative value, the negative A transparent plate 5 having a refractive index temperature dependency of
If the refractive index temperature dependency is a positive value, the transparent plate 5 having the positive refractive index temperature dependency is provided.

For example, when the lens 3 is formed of an acrylic resin, a polycarbonate resin, or the like, the refractive index temperature dependence of the lens 3 is a negative value, so that the transparent plate 5 also has a negative refractive index temperature dependence. It is formed of a material. Such a transparent plate
The material of 5 is the same as the material of the lens 3, such as acrylic resin (PMMA) or polycarbonate resin (PC).
And the like. The refractive index decreases as the temperature of the transparent plate 5 increases, and the refractive index increases as the temperature decreases. For example, when the transparent plate 5 is made of PMMA, the rate of change in the refractive index is -1.25 × 10 ^-4 / ° C., and the wavelength 7
The refractive index for light of 40 nm is 1.48 at a temperature of 0 ° C.
To 9489, to 1.486989 under 20 ° C temperature condition, and to 40 ° C
It becomes 1.484489 under the temperature condition of.

When the transparent plate 5 is formed using PC, the rate of change in the refractive index is -1.4.times.10.sup.- ⁴ / .degree.

The transparent plate 5 needs to have a large area capable of transmitting light from all the light emitting element array chips 2. In the case of an A4 head, a length of about 216 mm is conventionally known by injection molding. Formed.

The transparent plate 5 is placed on the base plate 1 via a spacer 4b thicker than the thickness of the light emitting element array chip 2, and the light emitting element array chip 2 and the transparent plate 5 are separated by the spacer 4b. It is kept in contact. The spacer 4b is formed of a resin or the like having a lower thermal conductivity than the base plate 1 so that the heat of the base plate 1 is not easily conducted to a transparent plate 5 described later. For example, the thickness of the light emitting element array chip 2 is 0.3 mm. In this case, the thickness of the spacer 4b is set to 0.4 mm to 0.6 mm.

In this embodiment, the spacer 4b having a thickness of 0.4 mm is used.
A transparent plate 5 made of PMMA having a thickness of 11.1 mm is placed thereon. The thickness of the transparent plate 5 is the second surface (upper surface) of the lens 3.
From the viewpoint of reducing the temperature dependence of the height and the angle of the light beam emitted from. If the height H2 of the light beam emitted from the second surface and the angle U2 'of the light beam are constant irrespective of the temperature, the height HP of the light beam on the photoreceptor surface P can be constant, and the dot displacement due to the temperature change can be suppressed. Incidentally, in the conventional example, H2 and U2 'change with the temperature change, and as a result, HP shift occurs.

The effect of arranging the transparent plate 5 having the same refractive index and temperature dependency as the lens 3 between the light emitting element array chip 2 and the lens 3 has the effect that H2 and U2 'are affected by temperature. Is to keep it constant. Before the light from the light emitting element 2a of the light emitting element array chip 2 enters the lens 3, a transparent plate
5, but when the temperature rises as compared to the reference temperature, the refractive index becomes smaller as in the case of the lens 3, so that U1 becomes smaller as compared with that at the reference temperature. By making U1 smaller, the change in the ray angle due to the smaller refractive index of the lens 3 is cancelled. Conversely, when the temperature decreases compared to the reference temperature, the refractive index of the transparent plate 5 increases, so that U1 increases as compared with the reference temperature. Increasing U1 cancels out changes in the ray angle due to an increase in the refractive index of the lens 3.

The thickness of the transparent plate 5 is determined by using the refractive index of the transparent plate 5, the refractive index of the lens 3, the curvature of the first surface and the curvature of the second surface of the lens 3, and the light height H2 of the second surface and the second surface. Light exit angle U2 '
The optimum thickness is determined as a condition under which the temperature dependence of is small.

When the temperature rises by 20 degrees from the reference temperature (20 ° C.) with respect to the specific ray height and ray angle when the temperature changes, the first refractive index of the lens 3 is changed due to the change in the refractive index of the transparent plate 5.
The incident angle of light on the surface (lower surface) is 0.0004 compared to the reference temperature.
However, since the refractive index of the lens 3 also decreases from 1.486989 to 1.484489 as in the case of the transparent plate 5, the increase in U1 'due to the change in the refractive index of the lens 3 is negated, and H2 is slightly smaller than that at the reference temperature. Only a change of 0.14 μm. Changes in U1 'and U2' compared to the reference temperature are also 0.0001,
As a result, the HP only increases by about 0.5 μm as compared with the reference temperature.

When the temperature is lowered by 20 degrees from the reference temperature (20 ° C.), the light incident angle on the first surface becomes larger by about 0.0004 as compared with the reference temperature due to the change in the refractive index of the transparent plate 5. The refractive index of lens 3 was 1.4868989, as in transparent plate 5.
Rises to 1.489489, so the decrease in U1 'due to the change in the refractive index of lens 3 is negated.
Changes only by 0.14 μm. The change in U1 ′ and U2 ′ compared to the reference temperature is also 0.0001, and as a result, HP
Is only about 0.5 μm smaller than at the reference temperature.

As described above, the transparent plate 5 having the same directional (negative) refractive index and temperature dependency as the lens 3 is disposed between the light emitting element array chip 2 and the lens 3. By correcting the deviation of the image forming position, the reference temperature ± 20
Even if a temperature change occurs, the change in the imaging position on the photoconductor surface P can be suppressed to 1 μm or less, and it is possible to construct an optical printer head of high printing quality with almost no white or black stripes. .

In this embodiment, the transparent plate 5 is kept in a non-contact state with respect to all the light emitting element array chips 2, and therefore, the temperature of the light emitting element array chips 2 is increased with the use of the optical printer head. Even if the temperature rises to 40 ° C. to 50 ° C., the transparent plate 5 is hardly affected by the rise. Therefore, the temperature of the transparent plate 5 does not locally rise and the refractive index of the transparent plate 5 does not locally change, and the shift of the imaging position caused by the change in the refractive index of the lens 3 due to the transparent plate 5 does not occur. Correction can be made reliably.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the transparent plate 5 having the same directional refractive index and temperature dependence as the lens 3 is arranged between the light emitting element array chip 2 and the lens 3.
Instead, as shown in FIG. 3, the refractive index temperature dependency of the direction different from that of the lens 3 between the lens 3 and the photoconductor (imaging plane) P, that is, the refractive index temperature dependency of the lens 3 is negative. When the value is a value, a transparent plate 5 'having a positive refractive index temperature dependency (a characteristic in which the refractive index increases as the temperature rises) may be provided. In this case, the same effect as in the above-described embodiment can be obtained. Can be obtained.

In the above-described embodiment, the transparent plate 5 is constituted by a single plate. Alternatively, the transparent plate 5 may be constituted by stacking a plurality of plates having different refractive index temperature dependences. .

Further, in the above embodiment, the light emitting diode element is used as the light emitting element 2a. However, an optical printer head may be constituted by using other light emitting elements, for example, an EL element, a fluorescent element, a plasma element and the like. Of course.

[0034]

According to the optical printer head of the present invention, even if the temperature of the lens fluctuates with the use of the optical printer head and the refractive index of the lens changes, the position of the image forming position caused by the change is changed. The misalignment can be satisfactorily corrected by the transparent plate, whereby a good continuous latent image can be obtained in the main scanning direction, and black streaks and white streaks of the print can be effectively prevented.

According to the optical printer head of the present invention,
By holding the transparent plate in a non-contact state with all the light emitting element array chips, even if the temperature of the light emitting element array chip rises with the use of the optical printer head, the transparent plate will be affected. Less is. Therefore, the temperature of the transparent plate does not locally increase and the refractive index of the transparent plate does not locally change, and the shift of the imaging position due to the change in the refractive index of the lens is reliably corrected by the transparent plate. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical printer head according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a light path of the optical printer head of FIG. 1;

FIG. 3 is a sectional view of an optical printer head according to another embodiment of the present invention.

FIG. 4 is a sectional view of a conventional optical printer head.

[Explanation of symbols]

1 ... base plate, 2 ... light emitting element array chip, 2a ... light emitting element, 3 ... lens, 5,5 '... transparent plate, P ... imaging surface (photoconductor)

Claims (2)

[Claims] 1. A plurality of light emitting element array chips in which a large number of light emitting elements are linearly arranged on a base plate, and a plurality of light emitting element array chips are arranged in a row, and one by one with the light emitting element array chips above the base plate. A plurality of lenses corresponding to each other are arranged, and an optical printer head for forming a latent image by forming light of the light emitting element of the light emitting element array chip through the lens is provided. Between the corresponding lens,
An optical printer head, wherein a transparent plate having the same refractive index temperature dependency as the lens and having the same directionality is disposed in a non-contact state with respect to all the light emitting element array chips. 2. A plurality of light-emitting element array chips in which a large number of light-emitting elements are linearly arranged on a base plate, and a plurality of light-emitting element array chips are arranged in a row, and one-to-one with the light-emitting element array chips above the base plate. A plurality of lenses corresponding to each other are arranged, and an optical printer head for forming a latent image by forming light of the light emitting element of the light emitting element array chip through the lens is provided. An optical printer head, wherein a transparent plate having a directionality different in refractive index temperature dependency from the lens is disposed between the lens and the lens.