JP2003023525A - Light-emitting unit, illuminating device using the same unit and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high speed image reading by improving the radiating performance of a light-emitting unit substrate, and increasing illuminating luminance by increasing the maximum currents running through the light-emitting element. SOLUTION: A light-emitting unit 20 is constituted by forming an open window 21a for mounting light-emitting elements on a resin light-emitting unit substrate 21, associated with a lead frame 22. The lead frame is provided with lead terminals 22a and inner leads and light-emitting element mounting and connecting parts 22b exposed in the open window 21a. Light emitting elements 23a, 23b, and 23c are mounted on the lead frames 22b exposed inside the open window 21a, the electrodes of the light-emitting elements are connected through a metal wire 24 to the lead frames, and the open window is sealed with transparent resin. The lead frames 22 are formed of iron copper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting unit, an illuminating device for illuminating a document, and a contact type image reading device (image sensor) incorporating the same.

[0002]

2. Description of the Related Art A contact image sensor is used as a device for reading a document in a facsimile device, a copying machine, an image scanner device or the like. This contact image sensor includes a line illumination device that linearly illuminates the document surface over the main scanning range.

As a line illuminator, one using a light guide is known. For example, Japanese Patent Laid-Open No. 8-163
Japanese Unexamined Patent Application Publication No. 320 and Japanese Unexamined Patent Application Publication No. 10-126581 (Japanese Patent No. 2999431) describe a line illumination device using a rod-shaped or plate-shaped light guide and an image reading device using the same.

In the above-mentioned line illuminator, a light guide body is provided which emits light incident from an end face from an emission face provided along the length direction while reflecting the light on the inner face, and light emission provided on the end face side of the light guide body. It is composed of a unit. The light emitting unit is provided with an opening window for mounting a light emitting element on a resin light emitting unit substrate provided with a lead frame,
The lead frame includes a lead terminal portion serving as an external connection terminal, an internal lead portion, and a light emitting element mounting / connecting portion exposed in the opening window, and the light emitting element is bonded to the lead frame exposed in the opening window. The electrode of the light emitting element and the lead frame are connected with a metal wire, and the opening window is sealed with a transparent resin. Phosphor bronze is used as the material of the lead frame.

[0005]

By increasing the brightness of the line illuminator and thereby increasing the brightness of the illumination light that illuminates the reading surface of the original, it is easy to speed up image reading. However, when the energizing current of the light emitting element is increased in order to increase the brightness of the line illuminator, the amount of heat generated by the light emitting element increases accordingly, and the light emission efficiency decreases, so that there is a problem that the brightness is difficult to increase.

When the light emitting element is energized, the junction temperature rises simultaneously with the light emission (heat is generated from the light emitting element itself). Since the generated heat escapes to the light emitting unit substrate side and is finally radiated into the air, the rise in the junction temperature depends on the heat radiation characteristic of the light emitting unit substrate and is substantially proportional to the energized current. That is, if the heat dissipation characteristics of the light emitting unit substrate are good, the rate of increase in junction temperature will be small.

On the other hand, energizing (lighting) the light emitting element at high temperature accelerates the deterioration of the light emitting element. Therefore, it is desirable to suppress the temperature rise of the light emitting element as much as possible in order to prolong the life of the light emitting element. Therefore, the maximum current that can be passed through the light emitting unit increases as the heat radiation performance of the light emitting unit substrate improves. The heat dissipation performance of the light emitting unit substrate varies depending on its shape, material and the like. Conventionally, phosphor bronze has been used as the material for the lead frame of the light emitting unit substrate. That is, phosphor bronze can be used as a material of a lead frame if the brightness has been conventionally required, but the thermal conductivity is not sufficient to obtain higher brightness.

[0008]

In order to solve the above problems, a light emitting unit according to the present invention has a lead frame mounted on a light emitting unit substrate on which a light emitting element is mounted and having a thermal conductivity of 250 W / (m · K). ) The above copper alloy or aluminum alloy is used. As the light emitting unit substrate, a resin or ceramic substrate can be considered.

Examples of the copper alloy include beryllium bronze and iron-containing copper. As specific component ratios of iron-containing copper, iron (Fe) is 0.02 to 0.5% by weight and phosphorus (P) is. 0.005 to 0.10% by weight, and the balance is copper (Cu).
By adjusting the proportions of iron and phosphorus to the above-mentioned proportions, the strength can be increased while maintaining high thermal conductivity. The more preferable composition ratio of iron and phosphorus is that iron (Fe) is 0.05 to 0.15.
% By weight, 0.015 to 0.04% by weight of phosphorus (P), and the balance copper (Cu).

In addition to the above materials, pure metals such as gold, silver, aluminum, copper, and tungsten are listed as materials having high thermal conductivity. However, gold and silver are expensive and impractical, and aluminum and copper have sufficient strength. But tungsten is difficult to process

In particular, the thermal conductivity of iron-containing copper having the above composition ratio is as large as about 364 W / (m · K). Therefore, if the lead frame is formed of iron-containing copper, the heat dissipation performance of the light emitting unit substrate is improved. Can be made. Accordingly, even if the current supplied to the light emitting element is increased, the temperature rise of the light emitting element can be suppressed and the illumination brightness can be increased.

Further, the thickness of the lead frame of the light emitting unit is t (mm), and the thickness of the light emitting unit substrate is T (m).
m), the thickness of the light emitting element is D (mm), and the height of the bonding wire is d (mm), 0.1 mm ≦ t ≦
(T-D-d) is preferable. A particularly preferable range is T / 2 ≦ t ≦ (T−D−d).

The width of the lead frame of the light emitting unit is W (mm), and the interval between the lead frames is P (m).
m) and the thickness of the lead frame is t (mm),
It is preferable that P / 2 ≦ W ≦ (P−t). A particularly preferred range is (P-2t) ≤W≤ (P-t).

As an illuminating device using the above light emitting unit, the light emitting unit is arranged on the end face side of the rod-shaped light guide, and the light incident from the light emitting unit is reflected in the inner surface of the rod-shaped light guide in the length direction. A light emitting unit is arranged on the side surface in the thickness direction of the plate-shaped light guide so that the light is emitted from the emission surface provided along the light-emitting unit, and the light incident from the light-emitting unit is reflected on the inner surface of the plate-shaped light guide. However, it includes an illuminating device that allows light to be emitted from the upper surface or the lower surface of the plate-shaped light guide.

Further, by incorporating the above-mentioned illuminating device into the image reading device, the illumination brightness of the original can be increased and the speed of image reading can be increased.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a cross-sectional view of an image reading device incorporating a line illumination device, FIG. 2 is an exploded perspective view of the line illumination device, and FIG. 3 is a perspective view showing an example of a light scattering pattern formed on the back surface of a light guide. .

As shown in FIG. 1, in the image reading apparatus, each recess 1a, 1b is formed in a frame (housing) 1, a line illumination device 10 is arranged in the recess 1a, and a photoelectric conversion element (line image) is provided in the recess 1b. Sensor board 4 with sensor 3
And a rod lens array 5 for image formation at equal magnification is held in the frame 1. A glass plate 2 is provided on the top of the frame 1. And the line lighting device 1
The light emitted from the emission surface 11a of 0 is applied to the original G through the glass plate 2, and the reflected light from the original G is detected by the photoelectric conversion element (line image sensor) 3 through the rod lens array 5 to detect the original. Read G. The frame 1 is moved in the sub-scanning direction of FIG. 2 with respect to the glass plate 2 to read a desired area of the document G.

As shown in FIG. 2, the line lighting device 10 includes:
The light guide body 11 is loaded in a white light guide body case 12 so that the emission surface 11a is exposed, and one or a plurality of light emitting elements (for example, light emitting diodes) 23 as a light emitting source is provided at one end of the light guide case 12. The light emitting unit 20 provided is attached. The light guide 11 is made of a translucent material such as glass or acrylic, and the cross-sectional shape in the direction orthogonal to the main scanning direction (longitudinal direction) has a basic rectangular shape, and the corners are chamfered. It is the emission surface 11a.

As shown in FIG. 3, on the back surface of the light guide 11,
The light-scattering pattern 11b for scattering the light from the light-emitting source incident from the incident surface is formed by screen-printing white paint or the like.

This line illuminating device 10 introduces light from a light emitting source into the light guide 11 from one end (incident surface) of the light guide 11 and transmits light propagating in the light guide 11 to the light guide. The light is scattered by the light scattering pattern 11b formed on the back surface, and the scattered light is emitted from the emission surface 11a (see FIG. 1).

On the side close to the incident surface, the intensity of the light incident from the light emitting source is large, and as the distance from the incident surface is large, the intensity of the light becomes smaller. Therefore, as shown in FIG. 3, the light-scattering pattern forming region is widened as the distance from the incident surface increases so that the light emitted from the emitting surface 11a becomes uniform over the entire length in the main scanning direction.

As shown in FIGS. 1 and 2, by covering the light guide 11 with the light guide case 12, the light guide 11 is protected and scattered light is wastefully emitted to the outside of the light guide. Is prevented and the intensity of the emitted light is increased.

FIG. 4 is a front view of the light emitting unit, FIG. 5 is a side sectional view of the light emitting unit, and FIG. 6 is a perspective view showing the structure of the lead frame of the light emitting unit.

The light emitting unit substrate 21 is formed by insert-molding a lead frame 22 in a substrate resin, and has an opening window 21a for mounting the light emitting element 23 (23a, 23b, 23c). Lead frame 22
Is a portion (lead terminal portion) 22a exposed for supplying power to the light emitting element 23 from the outside and a portion exposed in the opening window 21a for mounting the light emitting element 23 (light emitting element mounting /
It is composed of a connection part) 22b and a part (internal lead part) 22c hidden in the substrate resin. In addition, the lead frame 22
Has a silver plating on its surface in order to increase the light reflectance and improve the wire bonding property.

The light emitting unit 20 is a light emitting unit substrate 2
The light emitting element 23 (23a, 23b, 23c) is adhered onto the lead frame 22b exposed in the opening window 21a of No. 1,
The light emitting element 23 (23a, 23b, 23c) and the lead frame 22b are connected by a metal wire 24, and the transparent resin 25
The structure is sealed with. The through hole 26 provided in the light emitting unit substrate 21 is used when the line lighting device is assembled.
It is used to fix the light emitting unit 20 to the light guide case 12.

FIG. 7 is a wiring diagram of the light emitting elements in the light emitting unit. FIG. 7 shows an example of a line illuminator for color reading. There are various combinations of colors, numbers, and connections of the light emitting elements 23 mounted in the light emitting unit 20 depending on the purpose of reading. When the light emitting unit 20 is energized, the light emitting element 23 emits light. Increasing the energizing current also increases the emission brightness.

Conventionally, phosphor bronze was used as the material of the lead frame 22, but iron-containing copper was used as the material of the lead frame 22 in this embodiment. The comparison with the conventional material is shown below. Component (unit: wt /%) Iron-containing copper: Fe0.1, P0.03, residual Cu Phosphor bronze: Sn6.0, P0.045, residual Cu Thermal conductivity (unit: W / (m · K) Iron-containing copper: 364 Phosphor bronze: 86.7 Iron-containing copper has a thermal conductivity close to that of pure copper, which is a material having a particularly high thermal conductivity, of 391 W / (m · K).

FIG. 8 is a graph showing measured data of junction temperature. By changing the material of the lead frame 22 from phosphor bronze to copper containing iron, the heat dissipation characteristics are improved, and the rise in the junction temperature of the light emitting element 23 can be suppressed. As a result, the current value that can flow at the same junction temperature can be increased by about 30%.

FIG. 9 is a view showing another embodiment of the lead frame, and FIG. 10 is a view showing still another embodiment of the lead frame. As shown in FIG. 9, the lead frame 22
The heat dissipation characteristics can be further improved by increasing the plate thickness t. With respect to the plate thickness t of the lead frame 22, the light emitting element 23
It is possible to increase the thickness up to a size obtained by subtracting the thickness D of the wire and the height d of the bonding wire. From the viewpoint of the strength of the lead frame, the plate thickness t needs to be 0.1 mm or more. As a specific plate thickness t, 0.1 mm ≦ t ≦ (T−D−
d). Furthermore, as a preferable range, T / 2 ≦ t ≦
(T-D-d).

Further, as shown in FIG. 10, by widening the width W of the external lead terminal portion 22a of the lead frame 22, the heat dissipation characteristics can be further improved. The width W can be increased to a distance at which lead frames are not short-circuited, but in view of productivity, it is desirable to increase the width to a size obtained by subtracting the thickness t from the distance P between the lead frames. As a specific width W (mm), P / 2 ≦ W
≦ (P−t). Furthermore, as a preferable range,
(P-2t) ≦ W ≦ (P-t).

FIG. 11 is a sectional view showing another embodiment of the image reading device, and FIG. 12 is an exploded perspective view of the illumination device incorporated in FIG. 11. In the image reading device shown in FIG. The original G is read by detecting the reflected light from the photoelectric conversion element (line image sensor) 3 through the rod lens array 5, but in this embodiment, in addition to the above functions, In addition, the illumination device 30 is attached to the OHP document G.
The photoelectric conversion element 3 can also read the transmitted light of the document G. Similar to the reading apparatus of FIG. 1, in these embodiments, the frame 1 is moved with respect to the glass plate 2 to read a desired area of the original G.

The illumination device 30 has the light emitting unit 2 on the side surface in the thickness direction of the plate-shaped light guide 31 made of transparent acrylic resin.
0 is attached, the plate-shaped light guide 31 is housed in a white case 32, a white reflection plate 33 is provided on the upper surface serving as a reflection surface, and a diffusion sheet 34 is provided on the lower surface serving as an emission surface.

[0033]

As described above, according to the present invention, the heat dissipation performance of the light emitting unit substrate can be improved, so that the temperature rise of the light emitting element can be suppressed even if the current supplied to the light emitting element is increased. The illumination brightness can be increased.
By incorporating the line illumination device according to the present invention into the image reading device, the illumination brightness of the original can be increased,
It is possible to speed up image reading.

[Brief description of drawings]

FIG. 1 is a sectional view of an image reading device incorporating a line illumination device.

FIG. 2 is an exploded perspective view of a line lighting device.

FIG. 3 is a perspective view showing an example of a light scattering pattern formed on the back surface of the light guide.

FIG. 4 is a front view of a light emitting unit.

FIG. 5 is a side sectional view of a light emitting unit.

FIG. 6 is a perspective view showing a structure of a lead frame of the light emitting unit.

FIG. 7 is a wiring diagram of light emitting elements in a light emitting unit.

FIG. 8 is a graph showing measured data of junction temperature.

FIG. 9 is a view showing another embodiment of the lead frame.

FIG. 10 is a view showing still another embodiment of the lead frame.

FIG. 11 is a sectional view showing another embodiment of the image reading apparatus.

FIG. 12 is an exploded perspective view of the lighting device incorporated in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Frame (housing), 2 ... Glass plate, 3 ... Photoelectric conversion element (line image sensor) 4, Sensor substrate, 5 ... Rod lens array, 10 ... Line illumination device, 11 ... Light guide, 11a ... Emission surface, 11b ... light scattering pattern, 20 ...
Light emitting unit, 21 ... Light emitting unit substrate, 21a ... Opening window, 22 ... Lead frame, 22a ... Lead terminal portion, 2
2b ... Light emitting element mounting / connecting portion, 22c ... Internal lead portion,
23 ... Light emitting element, 24 ... Metal wire, 25 ... Transparent resin,
30 ... Lighting device, 31 ... Plate-shaped light guide.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5C051 AA01 BA04 DB29 DB34 DC05                       DD01 DE04                 5C072 AA01 BA03 BA12 CA05 CA14                       DA02 DA04 DA25 EA07

Claims (7)

[Claims] 1. A light emitting unit in which a lead frame is arranged on a light emitting unit substrate on which a light emitting element is mounted, wherein the lead frame has a thermal conductivity of 250 W / (m · K).
A light emitting unit comprising the above copper alloy or aluminum alloy. 2. A light emitting unit in which a lead frame is arranged on a light emitting unit substrate on which a light emitting element is mounted, wherein the lead frame has a width of W (mm), a lead frame interval of P (mm), and a lead frame plate. Thickness is t (mm)
In this case, P / 2 ≦ W ≦ (P−t) is satisfied. 3. The light emitting unit according to claim 1, wherein the copper alloy contains iron (Fe) of 0.02 to.
A light emitting unit comprising 0.5% by weight of phosphorus, 0.005 to 0.10% by weight of phosphorus (P), and the balance being iron-containing copper having a composition of copper (Cu). 4. The light emitting unit according to claim 1, wherein the lead frame has a plate thickness of t (m
m), the thickness of the light emitting unit substrate is T (mm), the thickness of the light emitting element is D (mm), and the height of the bonding wire is d.
(Mm), 0.1 mm ≤ t ≤ (T-D-d)
The light emitting unit is characterized in that 5. The light incident from a light emitting unit provided on the end face side of the rod-shaped light guide in the length direction is reflected by the inner surface of the rod-shaped light guide while being emitted from an emission face provided along the length direction. The lighting device according to claim 1, wherein the light emitting unit is specified in any one of claims 1 to 4. 6. The light incident from a light emitting unit provided on the side surface in the thickness direction of the plate-shaped light guide is reflected by the inner surface of the plate-shaped light guide while being emitted from the upper surface or the lower surface of the plate-shaped light guide. The lighting device according to claim 1, wherein the light emitting unit is specified by any one of claims 1 to 4. 7. An illuminating device according to claim 5 or 6, a line image sensor, and a rod lens array for converging reflected light or transmitted light from a document to the line image sensor are incorporated in a housing. An image reading device characterized in that