JPS589391B2 - electronic clock lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an illumination device for an electronic timepiece equipped with a light-receiving electro-optical display device.

Conventionally, electronic wristwatches equipped with light-receiving electro-optic display devices such as liquid crystal display devices have been inferior to needle-type displays or luminescent displays such as light-emitting diodes in terms of display clarity in dark places.

To improve this point, the currently most common method is
Lighting is done using incandescent bulbs.

However, this method required a light-guiding space below the liquid crystal for the passage of light from the incandescent bulb, which was an obstacle to making the wristwatch thinner.

In addition, since the reflective surface in daylight is far away from the liquid crystal surface, there is a drawback that the displayed image becomes double when viewed from an oblique direction.

Regarding the lighting effect, since the light source is a point light source or a line light source, a brightness gradient occurs on the liquid crystal display surface, and a sufficient lighting effect cannot be obtained.

On the other hand, a method has been considered to place a reflective surface coated with a phosphorescent, self-luminous, or self-luminous substance behind the liquid crystal display element, but this method does not provide enough light, and in some cases may cause radiation damage. There were also problems and the lighting method was not sufficient.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a method for increasing sufficient illumination effects using a thin surface light source. , by placing an electroluminescent board (hereinafter referred to as EL board) in parallel with the liquid crystal display device and closing a lighting switch controlled by an external operating member provided on the watch case, the built-in EL board drive circuit is activated. is activated to cause the EL plate to emit light.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a sectional view of a liquid crystal display device according to the present invention, where A is the liquid crystal display device and B is an EL plate placed on the back side of the liquid crystal display device.

To explain the liquid crystal display device, A1 and A2 are two glass plates, and A3 is a twisted nematic liquid crystal.

A4 and A5 are electrodes facing each other with the liquid crystal in between.

A6 and A7 are polarizing plates whose polarization axes are orthogonal to each other.

A8 is a liquid crystal sealant.

It is well known that in such a liquid crystal display device, when a voltage is applied between the upper electrode A4 and the lower electrode A5, the area where both electrodes overlap becomes opaque; The electrode A4 is divided into appropriate segments to obtain a display pattern suitable for display purposes.

On the other hand, to explain the EL board, a transparent electrode thin film B4 is formed on a transparent or light-diffusing translucent substrate B1 such as opal glass formed by the method described below, an insulating film B5 such as barium titanate, and an electroluminescent film B1. Substance B3
A metal plate B2 coated with the following layers is brought into close contact with the metal plate B2 and bonded with an organic adhesive, and a moisture-proof seal B6 is provided around the periphery.

The transparent electrode may be formed by etching a metal thin film obtained by vapor deposition into a mesh shape, by vapor-depositing indium oxide, or by hydrolyzing and sintering tin oxide.

Zinc sulfide mixed with a small amount of copper is usually used as electroluminescent material.

By using the transparent electrode B4 and the metal plate B2 as opposing electrodes and applying an AC voltage of 100 to 200 cm between them,
Electroluminescent material B3 emits light and emits light through transparent electrode B4 and transparent substrate B1.

FIG. 2A shows light rays under daylight according to the present invention, and the light rays l1 incident on the non-display part of the liquid crystal display device A are shown in FIG.
is reflected and scattered by the light-emitting layer, insulating layer, or other layer of EL board B and reaches the observer's eyes, but the light ray l2 that enters the display area shown by diagonal lines in the figure is absorbed by the liquid crystal display device. The light ray l2 reflected by the EL plate B and returned is weak.

Therefore, a difference in brightness appears on the liquid crystal display device A.

However, the sharpness of the display is not determined simply by the ratio of the intensities of the light rays l1 and l2, but is also largely controlled by the overall brightness and color tone, and often depends on the state of the reflective surface.

When the EL plate B is used as a reflective surface, a good reflective surface is obtained due to the bright yellow-green color of the electroluminescent material mainly composed of zinc sulfide and the white color of the barium titanate layer below it.

In addition, in order to obtain a clear display regardless of the positional relationship between the incident light source and the observer's eyes, it is necessary for the reflective surface to perform diffuse reflection, but zinc sulfide crystals have a maximum length of 10 μm to 20 μm on the irregular side. Since it is granular, it has a large scattering effect on incident light.

It has been described above that EL plate B has excellent characteristics as a reflective surface under daylight.

On the other hand, the opening in Figure 2 shows the light rays when the EL plate emits light in a dark place.

EL excited by an AC voltage of 100■~200■
The light rays emitted from the plate B enter the liquid crystal display device A from the bottom surface, but the light ray l3 that enters the non-display area reaches the observer's eyes, and the light ray l4 that enters the display area shown by diagonal lines in the figure It is absorbed and attenuated by the liquid crystal display device.

This causes a difference in brightness and darkness on the display surface, but since the EL board B emits light uniformly over its entire surface, a clear display is obtained without any brightness gradient.

Furthermore, by selecting an electroluminescent material, the spectrum of emitted light can be changed, allowing for colorful displays.

A light-scattering/transmissive plate may be sandwiched between the liquid crystal cell A and the EL plate B to serve both of the functions of reflecting daylight and transmitting illumination light at night.

Further, in the polarizing plate A7, such a material may be used for the carrier plate of the polarizing layer.

Furthermore, the liquid crystal cell A and the EL plate B may be integrated into a laminated structure.

FIG. 3 shows an example of an inverter circuit for driving the EL board having the configuration shown in FIG. 1, and is built into a watch.

The battery E also serves as a power source for the clock function, and only when the EL board needs to emit light, it supplies current to the booster circuit by closing the lighting switch SW, which is controlled by an external operating member provided on the exterior case of the clock. .

Transistor Q1 Resistor R1 Capacitor C and 3rd winding L1
, L2, and L3, the EL plate B constitutes a collector-tuned anticoupling oscillation circuit with a collector-tuned capacitor.

As can be inferred from its structure, the EL board B has a capacitor component CE connected in series.

In addition, the three windings L1, L2, and L3 are all wound in the same direction,
The winding start terminal is marked with a black dot in the figure.

By making the number of turns of the winding L3 sufficiently larger than the number of turns of the other two windings L1 and L2, a high AC voltage is generated in the collector tuning circuit, and the EL plate is excited to emit light.

FIG. 4 shows a base-tuned anti-coupling oscillation circuit using the same circuit elements as the EL plate drive circuit shown in FIG. 3, and obtains the same effect as the booster circuit shown in FIG. 3.

FIG. 5 shows an example of a circuit system for driving an EL board at an appropriately divided frequency when the clock mechanism itself has an oscillation source, such as a crystal oscillation type battery clock.

In the figure, T is a transformer having a primary winding L1 and a secondary winding L2, and the number of turns of the winding L2 is approximately 100 times the number of turns of the winding L1.

C is a capacitor that blocks the direct current of the transformer,
G is a gate for controlling the driving frequency signal given from the clock mechanism with the lighting switch SW.

Battery E supplies power to the clock mechanism and gate G.

When the lighting switch SW is closed in this circuit, a DC rectangular wave voltage with a peak value approximately equal to the battery voltage is applied to the primary winding L1 of the transformer T by the output of the gate G, and the secondary winding L2
The EL plate B serving as the load emits light due to the high voltage induced in the EL plate B.

The embodiments of the present invention have been described above, which enable surface illumination of a liquid crystal display device and uniform illumination without brightness gradients.

In addition, the beauty and variety of the electroluminescent colors emitted by the electroluminescence enhances the commercial value of the watch.Furthermore, the thin EL plate and its close contact with the back of the liquid crystal display reduce the thickness of the watch. It has become possible to prevent double images under light.

Furthermore, the voltage for the EL drive can be obtained from the battery and booster circuit that are shared with the clock mechanism, and by controlling the operation of the booster circuit with a lighting switch, battery consumption is prevented, which has not been put into practical use in the past. This made it possible to incorporate EL panels into watches, which had been considered difficult.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the liquid crystal display device and the EL board, Fig. 2 A shows the optical path of light rays incident on the liquid crystal display device from the outside, and Fig. 2 A shows the optical path of the light rays emitted from the EL board. The cross-sectional view, FIG. 3, FIG. 4, and FIG. 5 are circuit diagrams of an inverter circuit that generates a high-voltage AC voltage to drive the EL board. A...Liquid crystal display device, B...Electroluminescence board, E...Battery, SW...
...Lighting switch.

Claims (1)

[Claims] 1. An electronic timepiece equipped with a light-receiving electro-optical display device and using a battery as a driving source, comprising an electroluminescent plate disposed on the bottom surface of the electro-optic display device and converting the battery voltage into an AC high voltage. and a lighting switch that is controlled by an external operating member to operate the voltage boosting circuit, and when the lighting switch is operated, the electroluminescent plate emits light to illuminate the electro-optical display device. An illumination device for an electronic watch characterized by performing the following.