JPH11212513A - Display with back light and audio device provided with this display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality of sound by preventing an AC driving frequency of EL(electroluminescence) from appearing in a sound signal as a noise. SOLUTION: In an AC voltage generation part 5 of an EL back light driving part, a resistance value RT of its external resistance 6 is properly selected to set a frequency fEL of the AC driving voltage applied to an EL 10, to 100 to 200 Hz lower than a conventional set value (400 Hz) and higher than the switching frequency of an LCD picture (for example, 70 Hz), Thus, the extent of coupling of oscillation sounds of the EL 10 and the extent of electromagnetic coupling of AC power applied to the EL 10 are reduced to reduce the AC driving frequency noise outputted from the receiver of a PHS terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a display having an AC-driven backlight and an audio apparatus having the display.

[0002]

2. Description of the Related Art Conventionally, OA equipment such as a personal computer and a word processor, audio equipment such as a headphone stereo, a mobile phone and a PHS (Pers.
Liquid crystal displays are often used in mobile communication devices such as onal handyphone system terminals. Recently, with the increase in the size of the display screen, a backlight is employed to obtain uniform brightness regardless of the display position. As a light source used for the backlight, there is a fluorescent lamp or the like. Recently, an EL (Electro Luminescence) element with low power consumption has attracted attention.

A backlight using an EL element has a light emitting mechanism of an AC electric field driving type, and emits light by applying an AC driving voltage. However, mobile phones and PHS
For devices that handle audio signals like terminals, EL
The frequency component of the AC driving voltage for causing the backlight to emit light is mixed into the audio signal by electromagnetic coupling, which may cause annoying noise in the output audio, thereby deteriorating the sound quality. Also, when a sheet-like EL element is used,
The application of the AC drive voltage causes the EL element to mechanically vibrate, and this vibration may appear as unpleasant noise in the voice band, which is not preferable.

[0004]

As described above, when a display employing an EL backlight is used in a device for handling audio signals, the frequency of an AC drive voltage supplied to the EL backlight enters the audio band by electromagnetic coupling. Therefore, annoying noise may be generated in the audio signal, and the audio quality may be degraded. Also, the EL element may cause mechanical vibration due to the frequency of the AC drive voltage, and this vibration may appear as noise in a voice band.

The present invention has been made in view of the above circumstances. A first object of the present invention is to prevent the AC driving frequency of a light emitter from appearing in a voice signal as noise, thereby improving the voice quality. And a sound device provided with the display.

A second object of the present invention is to provide a backlight-equipped display capable of reducing the occurrence of mechanical vibration of the illuminant, thereby improving the sound quality, and an audio device having the display. is there.

[0007]

In order to achieve the first object, a display device with a backlight according to the present invention and an audio device provided with the display device are provided with a light transmission type display medium,
A light-emitting element for illuminating the display medium; and an AC drive circuit for supplying an AC drive power to the light-emitting body to perform a light-emitting operation. A frequency setting means for setting a frequency outside the voice band is provided.

The frequency of the AC drive power is set so as to be out of the band of the frequency characteristic of the audio output unit or out of the band of the frequency characteristic of the audio transmission line for transmitting the audio signal. Therefore, according to the present invention, since the frequency of the AC driving power supplied to the light emitter is set outside the audio band, even if this frequency is mixed into the audio signal path by electromagnetic coupling, this is automatically recognized as noise audible to the ear. Problems output from the receiver of the device and the receiver of the communication partner device are prevented, and thus the deterioration of the received voice quality and the transmitted voice quality can be prevented. Further, even if the sheet-shaped light-emitting body causes mechanical vibration due to the application of the AC drive power, a problem that this vibration sound is mixed into the received voice as noise audible to the ear can be prevented.

Further, the present invention is characterized in that the frequency setting means sets the frequency of the AC drive power lower than the audio band and higher than the switching frequency of the screen of the display medium. This can prevent the screen of the display medium from flickering due to the AC drive frequency.

The present invention is also characterized in that the AC drive circuit includes a level control circuit for controlling an output level of the AC drive power. In this way, even if the luminance of the illuminant is reduced by setting the frequency of the AC drive power lower than the audio band, for example, the lowering of the brightness is compensated by increasing the output level of the AC drive power by the level control circuit. can do.

According to another aspect of the present invention, there is provided a light-transmitting display medium, a light-emitting element for illuminating the display medium, and a light-emitting element for supplying AC driving power to the light-emitting element. An audio device including a display having an AC drive circuit for performing an operation, a filter is inserted into an audio signal path in the audio device, and the filter is transferred through the audio signal path by the filter. The frequency component of the AC drive power is removed from the audio signal.

Therefore, according to the present invention, even if the AC driving power frequency for driving the light emitter enters the audio band by electromagnetic coupling, this frequency component is removed from the audio signal by the filter. For this reason, it is possible to prevent noise due to the AC drive power frequency from appearing in the received voice and from being transmitted to the communication partner device together with the transmitted voice signal, thereby keeping the received voice quality and the transmitted voice quality high.

[0013] On the other hand, in order to achieve the second object, another invention is to dispose a light transmitting type display medium and a illuminant for illuminating the display medium on a housing in a state where they are overlapped with each other. In the backlight-equipped display device described above, a buffer member for filling a gap between the luminous body and the supporting portion of the luminous body in the housing is interposed and installed. .

Therefore, according to the present invention, the gap between the luminous body and the supporting portion of the luminous body in the housing is more reliably filled. For this reason, due to the effect of mechanical vibration due to the AC driving frequency of the light emitter, a vibration sound called so-called chatter between the light emitter and the housing is less likely to be generated, thereby maintaining a high sound quality. Can be.

[0015]

FIG. 1 is a circuit diagram showing a first embodiment of an EL backlight driving section according to the present invention. In the figure, first, when the PHS terminal is in the standby state, the power supply control unit 4 sets the power supply switch 3 to the off state. For this reason, power is not supplied from the regulator 2 to the AC voltage generation unit 5, and the start switch 5H in the AC voltage generation unit 5 is in the OFF state.
No drive voltage is supplied to 0, and as a result, EL10 does not emit light.

On the other hand, in the PHS terminal, when a key input operation is performed or an incoming call arrives, the power supply control unit 4 sets the power supply switch 3 to the ON state. Then, the power supply voltage generated by the regulator 2 based on the output of the battery 1 is supplied to the AC voltage generation unit 5. Also, at this time, in the AC voltage generation unit 5, the start switch 5H is turned on, so that the oscillation circuit 5A and the output voltage control circuit 5G are each operated. The oscillating circuit 5A is a RC oscillating circuit of a comparator system, and has a resistance value RT of an external resistor 6.
Sets the oscillation frequency fosc.

The transistor 5B is switched in accordance with the oscillation frequency fosc. When the transistor 5B is turned on, a current flows from the regulator 2 to the boosting coil 7. At the moment when the transistor 5B is turned off, a back electromotive force is generated in the boosting coil 7, and the current flows to the EL 10 via the diode 8, whereby the EL 10 is charged. Note that the capacitor 9 stabilizes the voltage value charged in the EL 10 to prevent noise from being generated by the boosting coil 7.

Transistors 5C, 5D, 5E, and 5F are cross-connected. When output Q of output voltage control circuit 5G is at L level and NQ is at H level, transistors 5C and 5F are turned on.
D and 5E are turned off. Therefore, at this time, the EL / terminal side of EL10 is at the ground potential (GND),
The EL terminal side is charged. When the charging voltage on the EL terminal side of the EL 10 reaches a specified voltage (about 60 V), the output voltage control circuit 5G detects this, and Q is at H level, N
Q becomes L level. Therefore, the transistors 5C and 5C
F is turned off, and the transistors 5D and 5E are turned on. As a result, the EL terminal side of the EL 10 becomes the ground potential (GND), and the EL / side is charged. When the charging voltage on the EL / side reaches a specified voltage (about 60 V), the polarity of the EL10 charging terminal is inverted.

By repeating the above operation, an AC voltage is applied to the EL 10, and the EL 10 emits light.
FIG. 2 shows voltage waveforms at various points in the above operation.

By the way, in the first embodiment, E
The L backlight unit has an AC drive voltage frequency fEL of 100 to 200 Hz when boosting the resistance value RT of the external resistor 6 connected to the oscillation circuit 5A to a specified voltage (60 V) at the oscillation frequency fosc. It is set to become.

The reason why the AC frequency fEL applied to the EL 10 can be varied by appropriately setting the resistance value RT of the external resistor 6 will be described below. That is, the oscillation frequency fosc of the RC oscillation circuit 5A of the comparator system is inversely proportional to the resistance value RT of the external resistor 6. On the other hand, the AC drive frequency fEL is inversely proportional to the oscillation frequency fosc of the RC oscillation circuit 5A as shown in FIG. That is, when the oscillation frequency fosc increases, the AC drive frequency fEL at the time of raising the voltage to the specified voltage at the oscillation frequency fosc decreases.

FIG. 4 is an enlarged view of a part of FIG. In the figure, a is the max characteristic, and b is ty
The p characteristics and c are the min characteristics. These are caused by variations in EL elements. Here, in the type characteristic b,
In the case of RT = 100 kΩ, foscｋ228 kHz,
fEL ≒ 150 Hz.

FIG. 5 explains that fEL decreases as fosc increases. FIG. 5 shows EL1 when output Q of output voltage control circuit 5G is at L level and NQ is at H level.
It shows an EL terminal side charging voltage waveform of 0. When the oscillation frequency fosc of the oscillation circuit 5A is low, VCIL (Low) is applied to the base of the transistor 5B, and the collector current IL flows through the boosting coil 7 when the transistor 5B is on. At the moment when the transistor 5B is turned off, a back electromotive force is generated in the boosting coil 7, and the current flows to the EL 10 via the diode 8, thereby causing
L10 is charged.

On the other hand, the same operation is performed when the oscillation frequency fosc is high, but the collector current IL (High) <
Since it is IL (Low), the back electromotive force VR (High) generated in the boosting coil 7 is also smaller than VR (Low). Therefore, when the oscillation frequency fosc is high, the number of times of boosting per unit time is larger than when the oscillation frequency fosc is low.
The amount of charge per boost is smaller than when the oscillation frequency fosc is low, and generally the time until the specified voltage is reached as shown in FIG. 5 is increased, and the frequency of the AC drive voltage applied to the EL 10 is increased. fEL decreases.

As described above, by appropriately selecting the constant of the external resistor 6 of the oscillation circuit 5A, the frequency fEL of the AC driving voltage applied to the EL 10 can be set to 100 to 200 Hz.

In the PHS terminal having the display with the EL backlight, the frequency fEL of the AC driving voltage applied to the EL 10 is set to fEL lower than the audio signal band.
= 100 to 200 Hz, the following effects can be obtained.

That is, the receiver frequency characteristics of the PHS terminal (total characteristics including not only electrical characteristics but also acoustic characteristics)
Is shown in FIG. As can be seen from the figure, the coupling amount of the vibration sound of the EL 10 and the electromagnetic coupling amount of the AC power applied to the EL 10 are fEL = 1 as compared with fEL = 400 Hz.
Decrease by 10 dB at 50 Hz, 2 at fEL = 100 Hz
Decrease by 5 dB. Therefore, the AC drive frequency noise of the EL 10 output from the receiver of the PHS terminal is greatly reduced, and there is no practical problem.

FIG. 7 shows the sound transmission frequency characteristics. As shown in FIG.
The amount of electromagnetic coupling of the AC drive voltage applied to 10 is fEL =
It is almost zero compared to 400 Hz, that is, there is no coupling, and E is output from the receiver of the communication partner terminal during a call.
The AC driving frequency noise of L10 disappears, and there is no practical problem.

Further, the AC driving frequency fEL of EL10
= 100 to 200 Hz is higher than the switching frequency of the LCD screen (for example, 70 Hz), and thus the EL1 is displayed on the LCD screen.
There is no fear of flickering occurring with the AC drive frequency of 0.

By the way, the AC driving frequency f of the EL 10
When the EL is reduced from the conventional 400 Hz to 100 to 200 Hz, the efficiency is reduced and the luminance of the EL 10 is reduced. This is not so problematic when the device is used in a dark state such as at night, but may deteriorate in visibility when used in a bright condition such as in the daytime or in an office.

Therefore, in this embodiment, the EL backlight drive unit is provided with a luminance compensation function. That is, the luminance of the EL generally increases depending on the applied voltage V, and is expressed as B = F (V) exp (−const ./. V) (1). F (V) is a function of the slowly changing applied voltage V.

In the case where the EL emission color is generally used blue green, the emission luminance and the driving voltage
The relationship with the frequency is as shown in FIG. As is clear from the figure, the light emission luminance increases in proportion to the drive voltage and the frequency.

Therefore, from the above equation (1) and the characteristics shown in FIG. 8, if the AC drive voltage applied to the EL 10 (specified voltage for boosting) is set high, the decrease in the light emission luminance due to the decrease in the drive frequency is compensated. It is possible.

Therefore, in the AC voltage generation section 5 shown in FIG. 1, the detection threshold value of the output voltage of the output voltage control circuit section 5G is set high. For example, if the threshold is 60 to 8
Set to 0V. By doing so, the specified voltage for inverting the polarity of the charging terminal of the EL 10 can be increased.
When the AC voltage generator 5 is configured by a discrete circuit, the setting change of the threshold value can be realized only by performing a small-scale circuit change. On the other hand, when the AC voltage generation unit 5 is integrated, this is realized by setting the threshold value high by laser trimming or the like.
Further, if the threshold value is configured to be externally set by the CPU, it can be easily dealt with by changing software or setting data.

As described above, according to the first embodiment of the present invention, the AC voltage generator 5 of the EL backlight driving unit appropriately selects the resistance value RT of the external resistor 6 to apply the voltage to the EL 10. The frequency fEL of the AC drive voltage is set to 100
２００200 Hz is set.

Therefore, the coupling amount of the vibration sound of the EL 10 and the electromagnetic coupling amount of the AC power applied to the EL 10 are reduced, so that the AC driving frequency noise output from the receiver of the PHS terminal can be reduced to a practically acceptable level. Can be reduced to In addition, AC driving frequency noise output from the receiver of the communication partner terminal during a call can be reduced. That is, it is possible to improve the reception sound quality and the transmission sound quality of the PHS terminal having the display with the EL backlight.

In this embodiment, the LC drive frequency fEL of the EL 10 is set to 100 to 200 Hz,
The switching frequency is set higher than the switching frequency (for example, 70 Hz) of the D screen. Therefore, there is no fear that the LCD screen will flicker due to the AC driving frequency of the EL 10.

Further, in this embodiment, the EL backlight driving section is provided with a luminance compensation function. That is, the detection threshold value of the output voltage of the output voltage control circuit unit 5G is set to a high value, for example, 60 to 80V.
The specified voltage for inverting the polarity of the charging terminal 10 is increased.

Therefore, it is possible to compensate for a decrease in the emission luminance of the EL 10 due to a decrease in the AC drive frequency, thereby sufficiently securing visibility when used in a bright atmosphere such as in the daytime or in an office. be able to.

(Second Embodiment) In a second embodiment of the present invention, a filter is inserted in an audio signal path in a PHS terminal device, and an EL mixed in the audio signal by the filter is inserted.
The AC drive frequency noise is removed.

FIG. 9 is a circuit block diagram showing a schematic configuration of the PHS terminal device in this embodiment. In the figure, the transmission voice signal detected by the microphone 11 is
After being amplified by the transmission amplifier 12, it is input to the A / D converter 13, where it is converted into a digital signal. And
This digital transmission voice signal is transmitted to the TDMA encoder 1
After being inserted into the transmission slot allocated to the own device in 4, it is input to the digital modulation section 15. In the digital modulator 15, the intermediate frequency signal is digitally modulated by the signal output from the TDMA encoder 4, and the modulated wave signal is input to the transmitter 16. In the transmitting section 16, the modulated wave signal is converted into a radio channel frequency and then amplified to a predetermined transmission power.
7 to the base station.

On the other hand, a radio carrier signal arriving from a base station is received by an antenna 17 and then converted to an intermediate frequency by a receiver 18. And this received intermediate frequency signal is
After being digitally demodulated by the digital demodulation unit 19, T
Input to the DMA decoder 20. TDMA decoder 2
In the case of 0, the digital demodulated signal inserted in the reception slot allocated to the own device is extracted from the plurality of reception slots of the TDMA frame. Then, the extracted digital demodulated signal is converted into an analog signal by a D / A converter 21, further amplified by a receiving amplifier 22, supplied to a receiver 23, and output from the receiver 23.

By the way, the most downstream position of the analog transmission voice signal path, that is, the transmission amplifier 12 and the A / D converter 13
, A filter 32 is inserted, and a filter 32 is inserted at the most downstream position of the analog reception voice signal path, that is, between the reception amplifier 22 and the receiver 23.
These filters 31 and 32 are band elimination filters, and their transfer characteristics are set so as to block the frequency component (for example, 400 Hz) of the AC drive voltage applied to the EL and pass the other frequency bands.

FIG. 11 shows an example of the configuration of these filters 31 and 32, which is a twin-T type notch filter. The rejection frequency fN of this filter is represented by fN = 1 / 2πRC, and the rejection bandwidth QN is represented by QN = ρ / 2 (1 + ρ).

As described above, the band elimination filters 31 and 32 whose rejection frequencies are set to the EL AC drive frequency are inserted at the most downstream positions in the analog transmission voice signal path and the analog reception voice signal path, respectively. Even if the driving frequency is mixed into the transmission voice signal and the reception voice signal by electromagnetic induction, these EL AC driving frequency components are removed by the band elimination filters 31 and 32. Therefore,
The transmitted voice quality and the received voice quality are kept high.

When the band elimination filters 31 and 32 are constituted by the above-described twin-T type notch filters, it is difficult to make the stop band width QN sufficiently narrow.
The effect on the audio signal is inevitable.

Therefore, when higher voice quality is required, the band elimination filters 31 and 32 are constituted by notch filters using a bootstrap twin-T circuit. FIG. 10 shows an example of the circuit configuration. This filter inputs the output signal of the twin-T circuit to the non-inverting amplifier U1 and the inverting amplifier U2, adds and combines the output signals with the resistor VR1, and combines the combined output signal via the buffer amplifier U3 with the above twin- It is configured to return to the T circuit.

The transfer characteristic G (s) of this filter is expressed as shown in FIG. The stop frequency fN is represented by fN = 1 / 2πRC, and the stop bandwidth Q is represented by Q = QN / (1−β). Here, β indicates the feedback amount.

By using the filter having such a configuration, the rejection bandwidth can be further narrowed, so that the frequency component (for example, 40
0 Hz) can be more effectively removed to further enhance voice quality.

(Third Embodiment) A third embodiment of the present invention relates to an EL sheet and a housing for holding the EL sheet in order to reduce the occurrence of mechanical vibration noise of the EL sheet due to the EL AC drive frequency. A cushioning member is interposed between the body and the body.

FIG. 13 is a block diagram showing E according to the third embodiment.
FIG. 2 is an exploded perspective view showing a structure of a liquid crystal display with an L backlight. Referring to FIG.
The LCD cover 54 and the LCD sponge 55 are sequentially mounted via the D spacer, while a sheet-like EL 52 is disposed on the back side of the LCD 53. This unit is mounted on the main board 50 via the multi-spacer 51.

A flat cushion 56 is interposed between the back surface of the EL 52 and the multi-spacer 51, and the four side surfaces of the EL 52 and the multi-spacer 5 are provided.
1 and a side cushion 57 is interposed therebetween.
These cushions 56 and 57 are made of an elastic material such as silicon rubber, for example, and fill the gap generated between the EL 52 and the multi-spacer 51.

With such a configuration, the cushion 5
6 and 57, the EL 52 is closely mounted to the multi-spacer 51 without any gap. Therefore, when an AC drive voltage is applied to the EL 52, the vibration corresponding to the frequency is generated by the EL
Even if it occurs at 52, no rattling sound is generated due to the vibration of EL 52, whereby the received sound quality can be kept high.

(Other Embodiments) In the first embodiment, the frequency of the AC drive voltage applied to the EL 10 is set to a value lower than the audio band, but may be set to a value higher than the audio band. In this case, the luminous efficiency of the EL 10 can be increased, and higher luminous luminance can be obtained with a smaller driving voltage.

In the first embodiment, a fixed resistor having a fixed resistance value RT is used as the external resistor 6, but a variable resistor capable of changing the resistance value RT manually or by a control signal from a CPU is used. May be. If such a resistor is used, even if the AC drive frequency changes due to, for example, aging, this can be corrected. In particular, if the AC drive frequency is monitored by the CPU and the resistance value RT of the variable resistor is variably controlled based on the monitoring result, fluctuations in the AC drive frequency due to effects such as temperature change as well as aging can be obtained. Can be corrected.

In the second embodiment, the AC drive frequency component included in the audio signal is removed by inserting the analog band elimination filters 31 and 32 in the analog audio signal path. In the audio signal path, a digital filter may be inserted between the A / D converter 13 and the TDMA encoder 14 to remove the AC drive frequency component contained in the transmission audio signal by digital filtering. Good. The AC drive frequency component may be removed by changing the frequency characteristic of the receiver 23.

In the third embodiment, a cushioning material such as silicon rubber is used as the cushioning member. However, an elastic adhesive or adhesive may be used instead. Further, the multi-spacer itself may be made of an elastic material so that no gap is formed between the multi-spacer and the EL.

Each of the means described in the first, second and third embodiments may be implemented independently, or may be combined with each other. For example, the variable setting means for the AC drive frequency described in the first embodiment may be combined with the mechanical vibration suppression means described in the third embodiment,
The filter means described in the third embodiment may be combined with the mechanical vibration suppression means described in the third embodiment. In this way, more effective noise removal can be performed.

In addition, the type of the luminous body, the circuit configuration of the AC drive unit thereof, the configuration of the variable setting means of the AC drive frequency, the type, configuration and insertion position of the filter, the type and structure of the buffer member, the type of the audio device, The configuration and the like can of course be variously modified and implemented without departing from the gist of the present invention.

[0060]

As described in detail above, the backlight-equipped display device of the present invention and the audio device provided with the display device have a light-transmitting display medium, a light emitter for illuminating the display medium, and a light-emitting device. An AC drive circuit for supplying AC drive power to the body to perform a light emitting operation, wherein the AC drive circuit includes frequency setting means for setting the frequency of the AC drive power outside the audio band. Provided.

According to another aspect of the present invention, a light-transmitting display medium, a light emitter for illuminating the display medium, and an AC drive circuit for supplying AC drive power to the light emitter to perform a light emission operation are provided. A sound device having a display, wherein a filter is inserted into a sound signal path in the sound device, and the frequency of the AC drive power is reduced by the filter from the sound signal transferred through the sound signal path. The components are removed.

Therefore, according to these inventions, the AC drive frequency of the illuminant does not appear as noise in the audio signal, thereby improving the audio quality. An audio device including a display can be provided.

According to another aspect of the present invention, there is provided a backlight-equipped display device in which a light-transmitting display medium and a light-emitting body for illuminating the display medium are mounted on a housing in a mutually superposed state. A cushioning member is provided between the body and the supporting portion of the light-emitting body in the housing to fill a gap therebetween.

Therefore, according to the present invention, the gap between the illuminant and the supporting portion of the illuminant in the housing is filled, whereby the occurrence of mechanical vibration around the illuminant is suppressed, and the sound quality is improved. It is possible to provide a backlight-equipped display that can be improved and an audio device including the display.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an EL backlight driving unit in a PHS terminal including a display device with an EL backlight according to the present invention.

FIG. 2 is a voltage waveform diagram used for explaining the operation of the device shown in FIG.

FIG. 3 shows the oscillation frequency fosc of the RC oscillation circuit in the circuit shown in FIG. 1 and the frequency f of the AC drive signal supplied to EL.
FIG. 4 is a characteristic diagram showing a relationship with EL.

FIG. 4 is an enlarged view of a main part of the characteristic diagram shown in FIG. 3;

FIG. 5 is a voltage waveform diagram for explaining that the oscillation frequency fosc of the RC oscillation circuit and the frequency of the AC drive signal fEL supplied to the EL are in inverse proportion.

FIG. 6 is a diagram showing reception frequency characteristics including acoustic characteristics of a PHS terminal provided with a liquid crystal display with an EL backlight according to the present invention.

FIG. 7 is a diagram showing an audio transmission frequency characteristic of a PHS terminal including a liquid crystal display with an EL backlight according to the present invention.

FIG. 8 is a characteristic diagram showing that EL light emission luminance increases according to an AC drive voltage and its frequency.

FIG. 9 is a circuit block diagram illustrating a PHS terminal including a liquid crystal display with an EL backlight according to a second embodiment of the present invention.

FIG. 10 is a circuit diagram showing an example of a filter provided in the PHS terminal shown in FIG.

FIG. 11 is a circuit diagram showing another example of a filter provided in the PHS terminal shown in FIG. 9;

FIG. 12 is a view for explaining transfer characteristics of the filter shown in FIG. 10;

FIG. 13 is an exploded perspective view showing the structure of a liquid crystal display with an EL backlight according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Regulator 3 ... Power supply switch 4 ... Power supply control part 5 ... AC voltage generation part 6 ... External resistance for AC voltage frequency setting 7 ... Boost coil 8 ... Charging diode 9 ... Capacitor 10 ... EL 11 ... Microphone 12 ... Transmission amplifier 13 ... A / D converter 14 ... TDMA encoder 15 ... Digital modulation unit 16 ... Transmission unit 17 ... Antenna 18 ... Reception unit 19 ... Digital demodulation unit 20 ... TDMA decoder 21 ... D / A converter 22 ... Receiver amplifier 23 ... Receiver 31, 32 ... AC drive frequency removing filter 50 ... Main board 51 ... Multi spacer 52 ... EL 53 ... Liquid crystal display (LCD) 54 ... LCD cover 55 ... LCD sponge 56 ... Flat cushion 57 ... Side cushion

Claims (12)

[Claims] 1. A light-transmitting display medium, a light emitter for illuminating the display medium, and an AC drive circuit for supplying AC drive power to the light emitter to perform a light emitting operation. A backlight-equipped display device, wherein the drive circuit includes frequency setting means for setting the frequency of the AC drive power outside the audio band. 2. The display device with a backlight according to claim 1, wherein the frequency setting means sets the frequency of the AC drive power lower than a voice band and higher than a switching frequency of a screen of the display medium. 3. The backlight-equipped display device according to claim 1, wherein the frequency setting means sets the frequency of the AC driving power to a frequency outside a frequency characteristic band of an audio output unit. 4. The backlight-equipped display device according to claim 1, wherein said frequency setting means sets the frequency of the AC drive power outside a frequency characteristic band of an audio transmission line for transmitting an audio signal. 5. The backlight-equipped display device according to claim 1, wherein the AC drive circuit includes a level control circuit for controlling an output level of the AC drive power. 6. A light-transmitting display medium, a light emitter for illuminating the display medium, and an AC for supplying light to the light emitter with AC driving power whose frequency is set outside the audio band to perform a light emitting operation. An audio device comprising a display having a driving circuit. 7. The light emitting device according to claim 6, wherein the AC driving circuit supplies an AC driving power whose frequency is set to a frequency out of a frequency characteristic band of the audio output unit to the light emitting body to perform a light emitting operation. Audio device. 8. The AC driving circuit supplies an AC driving power whose frequency is set outside a frequency characteristic band of an audio transmission line for transmitting an audio signal to a light emitting body to cause the light emitting element to perform a light emitting operation. The audio device according to claim 6. 9. A display device comprising: a light-transmitting display medium; a light emitter for illuminating the display medium; and an AC drive circuit for supplying AC drive power to the light emitter to perform a light emitting operation. An audio device comprising: an audio signal path in the audio device, wherein a filter for removing a frequency component of the AC drive power from an audio signal transferred through the audio signal path is inserted. Audio device 10. A backlight-equipped display in which a light-transmitting display medium and a light-emitting body illuminating the display medium are mounted on a housing in a state of being superposed on each other, wherein the light-emitting body and the housing are A backlight-equipped display device, wherein a buffer member for filling a gap between the light-emitting body and a supporting portion of the body is interposed therebetween. 11. The cushioning member includes a flat cushioning member that fills a gap between a bottom surface of the light emitting body and a supporting portion of the bottom surface of the light emitting body in the housing, and a supporting portion of the light emitting body side surface and the light emitting body side surface in the housing. The display device with a backlight according to claim 10, further comprising: a side cushioning member that fills a gap between the backlight unit and the backlight unit. 12. An audio apparatus having a backlight-equipped display device in which a light-transmitting display medium and a light emitter for illuminating the display medium are mounted on a housing in a state of being superposed on each other, An audio device having a backlight-equipped display device, wherein a buffer member for filling a gap between the luminous body and a supporting portion of the luminous body in the housing is interposed therebetween.