JP2983692B2 - Optical print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical print head in which light emitting diode arrays are arranged.

[0002]

2. Description of the Related Art Conventionally, an optical print head using a light-emitting diode array uses a light-emitting diode array having a length of 4 to 10 mm in an aligned manner, and even if the light-emitting diode array is a seam of the array. A large number of light emitting areas are arranged on the substrate so as to keep a predetermined interval of 0.5 to 0.01 mm corresponding to the printing resolution.
A radiator plate is used as in Japanese Patent Application Laid-Open No. 2-211972.

On the other hand, as a method of aligning a light emitting diode array with an accuracy corresponding to a printing resolution as described above, a light emitting diode is fixed on a small substrate in advance as disclosed in Japanese Patent Application Laid-Open No. 59-90975. Then, there is a method of aligning the small substrate on a large base, and this method has good alignment workability especially when the optical print head becomes long.

[0004]

In the case of laminating a plate-like body under a heating element as described above, Japanese Unexamined Patent Publication No.
As shown in the publication, the coefficient of thermal expansion of the laminate is gradually reduced or increased.

However, in the above-described optical print head, if the thermal expansion coefficient of the laminate is changed in this manner, the gap between the seams of the light emitting diode array is widened and white lines are generated between print dots, thereby deteriorating print quality. Conversely, the gap between the joints is narrowed, and the light emitting diode arrays themselves may collide with each other and be damaged or peel off from the substrate. Therefore, if a predetermined interval is set in consideration of a change in the interval between the joints of the light emitting diode array due to heat generation, a change in ambient temperature during storage (for example, storage temperature range +
(70 degrees to -20 degrees) includes a lower temperature range than the temperature change during driving, so that the light emitting diode arrays collide during storage.

[0006]

SUMMARY OF THE INVENTION In consideration of the above points, the present invention reduces the amount of change in the gap between seams due to temperature, and comprises a heat sink and a long base mounted on the heat sink. When,
It consists of a substrate smaller than the base placed on the base, and a light emitting diode array aligned on the base,
A plurality of the substrates are arranged on the base along the alignment direction of the light emitting diode array, and the thermal expansion coefficient of the substrate is smaller than both the thermal expansion coefficient of the light emitting diode array and the thermal expansion coefficient of the base.

[0007]

The temperature of the heat generated from the light emitting diode array decreases while propagating through the substrate having a small coefficient of thermal expansion, and the heat generated from the light emitting diode array is transmitted to a base having a large thermal expansion. Thus, it is considered that the extension of the base is compensated for by the extension of the substrate and the extension of the light emitting diode, and the synergistic effect thereof reduces the amount of change in the gap at the joint.

When a plurality of light emitting diodes are fixed on a substrate, the distance between the joints fluctuates only on the substrate by an amount corresponding to the difference between the thermal expansion of the substrate and the thermal expansion of the light emitting diode. The more accurate the length prediction,
Also, the fixing work of the light emitting diode array becomes easy.

[0009]

FIG. 1 is a plan view of an optical print head according to an embodiment of the present invention, and FIGS. 2 and 3 are side views of a main part in a longitudinal direction and a lateral direction thereof. In FIGS. 1 and 2, wiring means such as a wire bond is omitted for explanation. In these figures, reference numeral 1 denotes a heat radiating plate made of aluminum or the like, which is longer than the main scanning length of the printer, and is provided with a fixing means to the printer as required.

Reference numeral 2 denotes a base mounted on a heat sink, which is made of nickel-iron alloy (42Ni-Fe) or the like and has a width of 10 to 50.
mm, but the length is a long base having at least the main scanning length of the printer (210 to 1000 mm). 3
Is a substrate smaller than the base 2 disposed on the base 2 and made of a ceramic mixed resin substrate, and has a printed pattern (not shown) on the surface. Reference numeral 4 denotes a light-emitting diode array fixed and aligned on the substrate 3 in one row. On the surface thereof, light-emitting regions 41 and individual electrodes (not shown) arranged in one or two or three rows in a staggered arrangement are provided. And a common electrode (not shown) is provided on the back surface. The light emitting areas 41 are arranged at a pitch of 0.5 to 0.01 mm corresponding to the printing resolution of the optical printer, and are arranged in a line (staggered arrangement) so as to cover the entire main scanning length of the optical printer through the plurality of substrates 3. Is the number of columns).

In these configurations, a plurality of light emitting diode arrays 4 are respectively fixed on a substrate 3 with a conductive adhesive or the like, and wiring is applied to a driving integrated circuit 5 by wire bonding or the like. Reference numeral 3 is fixed to the base 2 with an adhesive or a screw, and the base 2 is pressed against a heat radiating plate by a clamper 6. The terminal (flexible substrate) connected to the substrate 3 is led out by being sandwiched between clampers 6.

In such a configuration, the respective coefficients of thermal expansion and thermal conductivity are as follows. Light emitting diode: thermal expansion coefficient 6.4 × 10 ^-6 / thermal conductivity 5
4.0 w / m · k conductive adhesive: thermal expansion coefficient 40 to 80 × 10 ⁻⁶ / thermal conductivity 2.1 w / m · k substrate: thermal expansion coefficient 3.8 × 10 ⁻⁶ / thermal conductivity 0 .9w / m
・ K base: thermal expansion coefficient 4.6 × 10 ⁻⁶ / thermal conductivity 14.6w /
mk radiator plate: thermal expansion coefficient 23.0 × 10 ⁻⁶ / thermal conductivity 236.
0 w / m · k A ceramic plate that has been conventionally used as a substrate or a base has a coefficient of thermal expansion of 7.0 × 10 ⁻⁶ / thermal conductivity of 20.0 w / m · k. As described above, the coefficient of thermal expansion of the substrate 3 is smaller than any of the coefficient of thermal expansion of the light emitting diode array 4 and the coefficient of thermal expansion of the base 2.

In this configuration, as the substrate 4, 215.
When an optical print head for the A0 plate is configured by using four 5 mm-long optical print heads, the distance between the substrates 4 is set to 0.01 m.
m, the distance between the light emitting diode arrays 4 having a length of 8 mm is 10 μm, and when driven at a black ratio of 90%, the temperature of the light emitting diode array 4 is 75 degrees, the temperature of the heat sink 1 is 45 degrees, and the substrate distance is −2.9 μm. The distance between the light emitting diode arrays 4 at the seam of the substrate 3 was -4.2 [mu] m, and the distance between the light emitting diode arrays 4 on the substrate 3 was -1.3 [mu] m. This is because when a ceramic which has been conventionally used as a substrate is used, the distance between the substrates is -10.5 μm under the same conditions, and the distance between the light emitting diode arrays 4 at the seam of the substrate 3 is -1.
The distance between the light emitting diode arrays 4 on the substrate 3 is 1.5 μm, which is significantly smaller than that of −0.5 μm. Actually, a lower black ratio is used in the optical printer, and the dot interval at the seam when printing one hundred standard documents continuously fluctuated by an average of -0.78 [mu] m. In the storage temperature range of 70 to -20 degrees, the variation of the joint was +8 m to -7 m.

The reason why the variation of the dot interval between the light emitting diodes is small is considered as follows.
That is, the heat generated from the light emitting diode propagates through the substrate, propagates through the base, and is released to the outside at the heat radiating plate, but the temperature decreases while propagating through each plate. Therefore, if the coefficient of thermal expansion of the substrate at high temperature is small, it acts to compensate for the thermal expansion of the base, and the light emitting diode array has the largest amount of elongation at the highest temperature. It is considered that the amount of change is extremely small. Further, when a plurality of light emitting diodes are fixed on the substrate, the distance between the joints varies only by an amount corresponding to the difference between the thermal expansion of the substrate and the thermal expansion of the light emitting diode on the substrate.

[0015]

As described above, even when an optical printer is formed by using a plurality of divided substrates, the intervals between the light emitting diode arrays are small and change, and the ease of assembling by using the divided substrates remains unchanged. Can be used.

[Brief description of the drawings]

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

FIG. 2 is a side view of a main part in a longitudinal direction of FIG.

FIG. 3 is a side view in the short direction of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat sink 2 Base 3 Substrate 4 Light emitting diode array

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-118169 (JP, A) JP-A-61-111587 (JP, A) JP-A-61-202859 (JP, A) JP-A-56-118 142081 (JP, A) JP-A-62-211972 (JP, A) JP-A-2-127442 (JP, U) JP-A-4-94649 (JP, U) JP-A-62-104957 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 H01L 33/00

Claims (1)

(57) [Claims] And 1. A heat radiating plate, a long base placed on the radiator plate, and the smaller substrate than the base disposed on the said base, is provided in alignment on the substrate Light emitting diode
And the substrate is the light emitting diode array.
A plurality of substrates are arranged on the base along the alignment direction, and
The coefficient of thermal expansion is based on the coefficient of thermal expansion of the light emitting diode array.
An optical printhead, wherein the optical printhead is smaller than any of the thermal expansion coefficients of the table .