JPH0419526Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention provides a liquid crystal cell in front of the reflective film, and when it detects strong light such as the headlights of a following car entering the reflective film, it controls the liquid crystal cell and reduces its transmittance. This invention relates to a liquid crystal anti-glare mirror switch that reduces glare.

Unlike those that switch reflectance mechanically, this type of LCD anti-glare mirror switch is electrically controlled, so there is no shock or rattling caused by mechanical operation.
It has a long lifespan and operates correctly. However, when the operating power source is turned off while the liquid crystal is being driven, that is, when the engine switch in an automobile is turned off, striped or spot-like unevenness may remain on the surface of the liquid crystal cell. Such unevenness is unsightly, especially when the power is turned off and then used again immediately.
If such unevenness appears on the anti-glare mirror, it becomes difficult to see the mirror, which is not desirable.

By the way, it was found that the reason why such unevenness occurs is based on the following reason. In other words, even if the ignition switch is turned off in a car, many loads such as motors are connected to the power supply circuit, so
The power supply voltage decreases relatively gradually, and the power supply voltage to the liquid crystal anti-glare mirror switch also gradually decreases.
Therefore, the oscillation amplitude of the liquid crystal drive oscillator also gradually decreases. On the other hand, the threshold value of the liquid crystal in each part of the liquid crystal cell is not uniform, so when the drive signal amplitude gradually decreases, the liquid crystal turns on and off unevenly in each part.
Since the area of the liquid crystal cell in an anti-glare mirror is large, there are minute variations in the spacing between the electrodes, which causes variations in the threshold value, and as a whole, the driving voltage does not pass through the threshold value of the liquid crystal at once. In addition, each part passes through the liquid crystal threshold unevenly, resulting in uneven stripes and spots.

The purpose of this invention is to provide a liquid crystal anti-glare mirror switching device that provides a uniform strong reflection state over the entire surface without leaving any unevenness even when the power is turned off while the liquid crystal is being driven.

According to this invention, when the operating power supply voltage of the switching device falls below a predetermined value, a comparator detects this, and the output of the comparator changes rapidly. Cut off the power supply voltage of the cell drive circuit. Therefore, the driving voltage of the liquid crystal cell suddenly drops and good shutoff is performed, and no unevenness remains in the liquid crystal cell.

Next, an embodiment of the liquid crystal anti-glare mirror switch according to this invention will be described with reference to the drawings. FIG. 1 shows a cross section of a liquid crystal anti-glare mirror, in which a liquid crystal cell 11 has a liquid crystal 14 sealed between transparent substrates 12 and 13 such as glass. A reflective film 16 is then formed by vapor deposition of aluminum or the like to constitute a liquid crystal anti-glare mirror. Although not shown in the figure, transparent electrodes are formed on the inner surfaces of the substrates 12 and 13, respectively. As the liquid crystal of this liquid crystal cell 11, for example, a cholesteric liquid crystal is used.

FIG. 2 shows an example of a liquid crystal anti-glare mirror switching device according to this invention.The terminal 21 is supplied with the output of the ignition switch, and when the switch is on, the operating power supply terminal of the switching device is connected to the power supply stabilizing circuit 22. A constant voltage is applied to 23. This terminal 23
The power supply voltage is applied to the sensor section 24 and the determination section 25 to operate them. The sensor section 24 is composed of an IC 27 including a light receiving element 26, a transistor 28, etc., and supplies an electric signal to the determination section 25 at a level corresponding to the light incident on the mirror shown in FIG. The determination unit 25 converts the electrical signal from the sensor unit 24 into either a binary DC signal. That is, when the light from the following vehicle is not received, the determination unit 25 outputs a high level H, and when the strong light from the following vehicle is received by the mirror, the light receiving element 2
6 detects this and outputs a low level L from the determining section 25. The output of the determination section 25 is supplied to the NOR gate 31. A signal of low level when the headlight is turned on and high level when the headlight is turned off is supplied from the terminal 32 to the other input side of the NOR gate 31.

The output of the Noah gate 31 is passed through the switch 33,
Further, the signal is supplied to an oscillator 35 through a chattering absorption circuit 34. The oscillator 35 starts oscillating when its input becomes low level L;
The output of 5 is applied to the base of a driving transistor 37 through an inverter 36. Also, oscillator 3
The output of No. 5 is applied to the base of a driving transistor 41 through a NOR circuit 38 and an inverter 39. These driving transistors 37, 4
1 collectors are respectively connected to the opposing electrodes of the liquid crystal cell 11, and are also connected to the power supply terminal 23 through resistors 42 and 43, respectively.

A manually operated switch 44 is connected to the other switching side of the switch 33, and the manually operated switch 44 can be switched between the power terminal 23 and ground. The power supply terminal 23 is connected to the terminal 32 through a resistor 45, a light emitting diode 46, and a switch 47 that operates in conjunction with the switch 33. The power supply terminal 23 is connected through a resistor 45, a light emitting diode 48, and a switch 49 that operates in conjunction with the switch 44.
is connected to the terminal 32 through the other switching side of the switch.

In this embodiment, comparators 51 and 52 are provided, and the power supply terminal 23 is grounded through a resistor 53 and a Zener diode 54. A reference voltage is obtained at the Zener diode 54, and the reference voltage is applied to each inverter of the comparators 51 and 52. given to the input side. Further, the power supply terminal 23 is grounded through resistors 55 and 56, and the power supply terminal 23 is connected to the voltage dividing point of the resistors 55 and 56.
3 is detected, and the detected voltage is sent to the comparator 51,
52 non-inverting inputs. comparator 51,
The output side of 52 is a transistor 3 to be driven respectively.
7,41 collector.

In this configuration, when the changeover switch 33 is connected to the Noah gate 31 side, the switch 4
7 is the light emitting diode 46 side. When the headlight is not on, that is, during the daytime, the terminal 32 is at a high level H, and this high level H is given to the NOR gate 31, and the output of the NOR gate 31 is determined by the high level or low level of the output of the determining section 25. Regardless, it becomes a low level L, and this low level is applied to the oscillator 35, causing the oscillator 35 to enter an oscillating state. This oscillation output is given to the drive transistor 37 through the inverter 36, and is also given to the drive circuit 41 through the NOR circuit 38 and the inverter 39. Therefore, these drive circuits 37 and 41 are driven with opposite polarities, and are located opposite to each other in the liquid crystal cell 11. An alternating voltage is applied between the electrodes, and the liquid crystal cell 11 enters a transmissive state, that is, a strongly reflective state. In this state, the light emitting diode 46 does not emit light.

At night, or in a tunnel, the headlight terminal 32 is at a low level L, and the light emitting diode 46 is lit to indicate that the anti-glare mirror is under automatic control. Further, the terminal 32 side of the NOR gate 31 becomes low level. In this state, when the headlight from the following vehicle is not incident, the level of light input from the light receiving element 26 is small, the output of the determination unit 25 is high level H, and the output of the NOR gate 31 is low level L, so that The oscillator 35 enters an oscillating state and the liquid crystal cell 11 is driven in the same manner as described above, the liquid crystal cell 11 enters a transmitting state and the anti-glare mirror becomes a state of high reflectance.

However, when light from the following vehicle enters the light receiving element 26, the output of the determination unit 25 becomes a low level L, the output of the NOR gate 31 becomes a high level H, and the oscillation of the oscillator 35 stops, and the driving transistor 37,
41 are both conductive, no voltage is applied between the electrodes on both sides of the liquid crystal cell 11, and the liquid crystal cell 11 is in a cut-off state with low transmittance.
Incident light is reflected by the surface of 1, and its reflectance becomes weak. Therefore, there is no possibility that the driver will be strongly exposed to the strong headlight light from the following vehicle.

When the switch 33 is connected to the switch 44 side,
Along with this, the switch 47 is connected to the switch 49 side. In this state, switch 44 is connected to power terminal 2.
When connected to the third side, the oscillator 35 stops oscillating, the transmittance of the liquid crystal cell 11 decreases, and the reflectance of the anti-glare mirror decreases. When the switch 44 is connected to the ground side, the oscillator 35 oscillates, and the liquid crystal cell 11 enters a transmissive state, resulting in strong reflection.

When the ignition switch is turned off, terminal 2
The power supply voltage at 1 gradually decreases. Since the stabilizing operation of the power supply stabilizing circuit 23 is not performed sufficiently, the voltage at the power supply terminal 23 also gradually decreases. When the voltage at the power supply terminal 23 drops below a predetermined value, that is, the reference voltage determined by the Zener diode 54, the outputs of the comparators 51 and 52 are inverted from the high level H to the low level L. Therefore, the collectors of the drive transistors 37 and 41 become low level. Driving of this liquid crystal cell 11 stops instantaneously. That is, even when the oscillator 35 is oscillating, the supply of the oscillation output to the liquid crystal cell 11 is instantaneously interrupted. Therefore, even if the voltage at the power supply terminal 21 gradually decreases, the driving of the liquid crystal cell 11 is instantaneously cut off, and there is no risk of uneven stripes or spots occurring on the liquid crystal cell 11 as described above.

In Figure 2, by controlling the headlights on and off, it is detected that it is night time or that the person is in a tunnel, and the anti-glare mirror is automatically switched. A sensor 61 receives external light, and supplies the output of this light to a day/night determination circuit 62 to determine whether it is daytime or night, or whether it is outside or inside the tunnel. For example, in the daytime, the output of the determination circuit 62 is increased. It may be applied to the NOR gate 31 as a level H instead of the output from the terminal 32 in FIG. In this case, at night, the output of the judgment circuit 62 is at a low level L, and the output of the judgment circuit 62 is given to the base of the transistor 64 through the inverter 63. When the output of the judgment circuit 62 is at a high level, the transistor 64 is turned off,
In the case of a low level, transistor 64 is conductive, and depending on the switching state of switch 47, diode 46 or 48 is made conductive through transistor 64.

For example, as shown in FIG. 4, the oscillator 35 is kept in constant oscillation, the output of the oscillator 35 is supplied to the NOR gate 65, the output of the NOR gate is supplied to the NOR gate 66, and the output of the chattering absorption circuit 34 is supplied to the NOR gate 65. , 66, and the output of the power supply terminal 23 is passed through the resistor 42 and further through the inverter 67 to the NOR gate 6.
5,66. NOR gates 65 and 66 are drive circuits for liquid crystal 11, and their outputs are supplied to opposing electrodes of liquid crystal 11, respectively.

In this configuration, when the output of the NOR gate 31 is at a low level L, the output of the oscillator 35 is supplied to the liquid crystal cell 11 through the NOR gates 65 and 66, and the liquid crystal cell 11 enters a transmissive state. On the other hand, the output of the NOR gate 31, that is, the chattering absorption circuit 3
When the output of 4 becomes high level, the Noah gate 65, 6
6 becomes a low level, liquid crystal driving to the liquid crystal cell 11 is stopped, and the liquid crystal cell 11 enters a cut-off state. When the voltage at the power supply terminal 23 falls below a predetermined value, the output of the comparator 51 becomes a low level as shown above, the output of the inverter 67 becomes a high level, and therefore the output of the oscillator 35 and the output of the chattering absorption circuit 34 Noah Gate 65,6 regardless of
6 becomes low level, and driving to the liquid crystal cell 11 is stopped.

Alternatively, as shown in FIG. 5, the output of the chattering absorption circuit 34 is supplied to the exclusive OR circuit 68, and the voltage of the power supply terminal 23 is applied to the exclusive OR circuit 68. Therefore, exclusive OR circuit 68 acts as an inverter, and the output of exclusive OR circuit 68 is supplied to exclusive OR circuit 69. The output of the oscillator 35 is supplied to the NOR circuit 71 and also to the exclusive OR circuit 69. The output of the exclusive OR circuit 69 is supplied to a NOR circuit 72, and the outputs of the NOR circuits 71 and 72 are supplied to both electrodes of the liquid crystal cell 11. The output of the power supply terminal 23 is the exclusive OR circuit 7
The output of the comparator 51 is also supplied to the exclusive OR circuit 73 thereof. Therefore, the exclusive OR circuit 73 also acts as an inverter, and when the output of the comparator 51 is at a high level, the output of the exclusive OR circuit 73 is at a low level and the NOR circuits 71,
The output of 72 is output according to each of the other inputs.

When the output of the chattering absorption circuit 34 is at a low level, the output of the exclusive OR circuit 68 is at a high level, and in this high level state, the output of the exclusive OR circuit 69 is an inversion of the output of the oscillator 35. This is supplied to the NOR circuit 72, and the liquid crystal cell 11 is driven in this state. However, when the output of the exclusive OR circuit 68 is low level, the exclusive OR circuit 69 outputs the oscillator 35.
In order to output the output as it is, the NOR circuit 71,
The outputs of 72 have the same phase, and the liquid crystal cell 11 is not driven. When the voltage at the power supply terminal 23 falls below a predetermined value, the output of the exclusive OR circuit 73 becomes high level, and the output becomes low level regardless of the other input to the NOR circuits 71 and 72, and the liquid crystal cell 11 is not driven. .

As described above, according to the liquid crystal anti-glare mirror switch according to this invention, even if the power is cut off while the liquid crystal is being driven, the drive to the liquid crystal is instantly cut off, and there is no risk of unevenness in the liquid crystal cells.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view showing a liquid crystal anti-glare mirror;
FIG. 2 is a connection diagram showing an example of a liquid crystal anti-glare mirror switch according to this invention, and FIGS. 3 to 5 are circuit diagrams showing other examples. 11...Liquid crystal cell, 16...Reflection film, 23...
Power terminal, 24...sensor section, 25...judgment section,
26... Light receiving element, 35... Oscillator, 37, 41
... Drive transistor, 51, 52 ... Comparator,
71, 72, 65, 66...Nor gate for driving.

Claims (1)

[Scope of utility model registration request] The light irradiated onto the mirror is received by a light receiving element, the output of the light receiving element is converted into one of the binary DC signals according to the level, and the converted DC signal is sent to the light receiving element. The oscillation circuit is set to an oscillation state by a signal indicating that the mirror is not receiving light, and the oscillation output controls the drive circuit to bring the liquid crystal cell provided in front of the reflective film of the mirror into a state of high light transmittance. , the oscillation of the oscillation circuit is stopped by the DC signal indicating that the light receiving element is receiving light, and the light transmittance is controlled to be small without applying voltage to the liquid crystal cell. However, if the oscillation circuit fails when the power supply is normal, a DC voltage is applied to the liquid crystal cell to maintain a high light transmittance. a comparator that detects that the voltage has fallen below the specified value and rapidly reduces its output; and a cutoff means that uses the output of the comparator to control the drive circuit of the liquid crystal cell to cut off voltage application to the liquid crystal cell. LCD anti-glare mirror switch equipped with.