JPS5848096B2 - exiyouhiyoujisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device for displaying, for example, the time of a digital watch or other numerical values.

For example, when constructing a wristwatch with a digital display, not only is the display device required to be as compact as possible, but the power capacity that can be installed is limited, so the power consumption for display is limited. is required to be sufficiently small.

For this reason, many display devices of this type use liquid crystals.

However, this liquid crystal display device utilizes the property that the arrangement state of liquid crystal molecules changes when a voltage is applied, and displays characters and figures by changing the light transmission state.

In other words, unlike light emitting diodes, EL, etc., which display characters and figures by self-emission, they can be displayed very effectively in bright places, but in dark places such as at night, it is difficult to read and distinguish the displayed characters. This makes it difficult.

This invention has been made in view of the above points, and provides a liquid crystal display device that allows displayed characters to be read reliably even in a dark place and effectively improves the design effect of the display. This is what we are trying to provide.

An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show the structure, in which an upper transparent substrate 11 made of glass or the like on the display side and a lower transparent substrate 12 made of glass or the like on the back side are separated by a spacer 13 at a small distance. These upper and lower transparent substrates 11.1 are arranged oppositely.
A nematic liquid crystal 14 having positive dielectric anisotropy is filled in the space surrounded by the spacer 2 and the spacer 13.

The molecules of the liquid crystal 14 are arranged in a helical structure parallel to the transparent substrates 11.12 and twisted approximately 90 degrees between the transparent substrates 11.12.

Polarized light beams 15 and 16 whose polarization angles are perpendicular to each other are attached to the outer surfaces of the upper and lower transparent substrates 11 and 12, respectively, and a common electrode 1γ is formed from tin oxide or the like on the entire inner surface of the upper transparent substrate 11 where the liquid crystal 14 is present. It is made of a transparent conductor.

Further, on the inner surface of the lower transparent substrate 12, a plurality of segment electrodes 18 for forming character shapes are formed with a transparent conductor made of tin oxide or the like, as shown in A of FIG. As shown by the broken line in B, a background electrode 19 is formed of a transparent conductor in a range excluding the segment electrodes 18.

Then, on the surface of the lower transparent substrate 12 having the polarizing plate 16, a diffusion plate made of transparent plastic or the like is formed with a light diffusion pattern 20 corresponding to the letter shape by a large number of through holes, etc. 21 are arranged opposite each other, and light is emitted from the side surface of the diffuser plate 21 by a light source 22 such as a lamp.

Further, a reflecting plate 23 made of aluminum or the like is provided on the back side of the diffuser plate 21 so that the light from the light source 22 is effectively guided toward the liquid crystal 14 .

That is, in the liquid crystal display device configured as described above, when a voltage is applied between the common electrode 1γ and the segment electrode 18, the portion corresponding to the shape of the segment electrode 18 to which this voltage is applied is The molecules of the liquid crystal 14 are rearranged in the direction of the electric field, that is, in the direction perpendicular to the transparent substrates 11 and 12, and the helical structure collapses, so the optical rotation in that part is lost, and the light is blocked by the polarizing plate 15, so that characters and figures are displayed.

In this case, due to the properties of liquid crystal, an alternating voltage signal is applied between the segment electrode 18 and the common electrode 1γ.

Therefore, the display voltage signal circuit at this time is configured as shown in FIG. 4, for example.

That is, the timekeeping section 24 generates a segment signal for displaying and driving time information associated with timekeeping, and a drive signal of, for example, 32 Hz that drives the liquid crystal in an alternating current manner. The voltage signal is supplied to exclusive OR circuits 25 and 26 that combine the voltage signals, and the segment signal is supplied to the OR circuit 25.

Further, the drive signal is coupled to the ground electrode 19 .

Furthermore, this circuit is provided with a switch 2γ that is turned on when reading the displayed characters in a dark place, and when it is turned on, the voltage v
DD is supplied to the drive circuit 28 of the light source 22 to turn on the light source 22, and is also supplied to the exclusive OR circuit 26.

That is, when the drive signal from the timer 24 is in a state as shown in A in FIG. 5, the voltage signal shown in B in the same figure is supplied to the selected segment electrode 18 to be driven for display, and at this time, the character/figure is expressed. A voltage signal as shown in C in the same figure is coupled to the unselected segment electrodes 18 that are not necessary for this purpose.

At this time, if the switch 2γ is not turned on and is in the off state, the common electrode 1γ is connected to the fifth
The same voltage signal E as the drive signal shown in Figure A is coupled to the segment electrode 18 to which the signal shown in Figure B is coupled.
The liquid crystal 14 in the part corresponding to A loses its optical rotation, and
The required characters and figures are displayed as shown in .

In short, a driving potential difference is applied between the common electrode 11 and the selected segment electrode 18 in such a relationship that one side is a high voltage and the other is a low voltage, or vice versa.
The arrangement of the molecules of No. 4 is perpendicular to the transparent substrate 11, 12, and optical rotation is lost. However, a voltage with the same waveform is applied between the common electrode IT and the non-selected segment electrode 18, resulting in a drive potential difference. The arrangement of the molecules of the liquid crystal 14 in this part has a helical structure and has an optical rotation view.

Further, when it is desired to read the display in a dark place such as at night, the switch 2γ is turned on to turn on the light source 22.

And what is common at this time? &Jj 1 7 is operated by the exclusive OR circuit 26, and the common electrode 1γ is connected to F in FIG.
A signal as shown in is supplied.

Therefore, from the relationship between the voltage signal as shown in C in FIG. 5 for the non-selected segment ta pole 18 for expressing a character figure, and the voltage signal for the ground electrode 19 as shown in D in FIG. Contrary to the above case, the liquid crystal 1 of the part corresponding to the non-selected segment 18 and the ground electrode 19 part
4 loses optical rotation.

That is, the portion of the liquid crystal 14 corresponding to the displayed character figure has optical rotation, and the diffused light from the light source 22 from the light diffusion pattern 20 of the diffusion plate 21 is displayed via the portion of the liquid crystal 14 and the polarizing plate 15. As shown in FIG. 6B, characters are displayed using light.

That is, by irradiating light from the light source 22 onto the diffuser plate 21 from the side, the light is focused on the light diffusion pattern 20 provided on the diffuser plate 21 corresponding to the shape corresponding to the segment electrode 18. The light diffusion pattern 20 itself appears as if it were emitting light.

For this reason, the non-selected segments 18 other than the segment electrodes 1B necessary for forming characters are driven as described above, and the liquid crystal 14 is made opaque so that a part of the light diffusion pattern 20 from which the light is emitted is By blocking the screen (/), characters and figures made of light will be displayed.

That is, since the displayed characters appear to emit light, it is possible to obtain a light with higher brightness than simply using the diffuser plate 21, and a great effect is obtained in that information can be displayed more clearly and with higher contrast.

Although the above embodiment uses a FEM twisted nematic type liquid crystal display device, it is needless to say that the present invention is not limited to this and can be similarly implemented in a DSM type liquid crystal display device or other liquid crystal display devices.

Further, in the above embodiment, the light diffusion pattern 20 is formed by providing a through hole in the diffusion plate 21, but it does not have to be a through hole, but may be formed by providing a groove.

Alternatively, a fluorescent substance made of tritium, promethium, etc. may be applied to the lower surface of the diffuser plate 21, and the fluorescent substance may be excited by the light from the light source 22 to utilize afterglow properties.

Further, a plurality of light sources 22 may be used, and a light emitting diode or the like may be used.

Further, the diffusion plate 21 is not limited to the one shown in the embodiments, but it can be made of glass or the like, and the effect can be further improved by making the upper surface rough to scatter light.

That is, any structure can be used as long as it can effectively guide light in the display direction.

Furthermore, in this embodiment, the light diffusion pattern 20 is provided on the diffusion plate 21 itself;
Instead of having 0 engraved thereon, a layered structure with a separately provided member having a light diffusion pattern engraved thereon may be used.

Further, a half mirror is interposed between the diffuser plate 21 and the lower transparent substrate 12, and the half mirror blocks incident external light from the display surface of the display device, and the light from the light diffusion pattern 20 of the diffuser plate 21 is further reduced. It is effective if it is effectively guided toward the display surface.

In short, it goes without saying that various changes may be made without departing from the gist of the present invention.

As described above, according to the present invention, a liquid crystal display device is obtained which can display characters effectively, especially in a dark place, and can be effectively used for digital display of a clock, for example.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a display device according to an embodiment of the present invention, FIG. 2 is a sectional view of the same, FIG. 3 is a diagram showing the state of segment electrodes and ground electrodes of the display device, and FIG. FIG. 5 is a diagram showing the drive control circuit of the display device, FIG. 5 is a diagram explaining the state of a voltage signal for drive control, and FIGS. 6A and 6B are diagrams showing display modes, respectively. 11... Upper transparent substrate, 12... Lower transparent substrate, 13... Subaru, 14...
・Liquid crystal, 15.16...Polarizing plate, 1γ...
・Common electrode, 18...Segment electrode, 19・
...Ground electrode, 20...Light diffusion pattern, 21
... Diffusion plate, 22 ... Light source.

Claims (1)

[Claims] 1 A common electrode and a plurality of segment electrodes representing character figures are formed on the surfaces of a pair of transparent plates facing each other with a liquid crystal interposed therebetween, and a background is further formed on the transparent plate surface having the segment electrodes in a portion other than the segment electrode portion. A ground electrode is formed, and a light guide plate having a light diffusion pattern corresponding to the character shape is provided on the outer surface of one of the transparent plates opposite to the direction of the display surface, and a light guide plate is provided on the side of the light guide plate. A liquid crystal display comprising: a light source; when the light source is turned on, a liquid crystal drive voltage is applied between a non-selected segment electrode and a common electrode and between a background electrode and a common electrode; display island