JP2000098348A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the power consumption in a liquid crystal display device performing a display by simultaneously using both of a light from a light source and an external light. SOLUTION: Any one of first - third modes is selected alternatively (S2). In the case of the first mode, a sensor detecting environmental illuminance is turned on, and by adjusting the luminance of the light from the light source based on the detection result by the sensor, screen luminance is controlled so that the screen luminance becomes suitable for the environmental illuminance at that time (S3). In the case of the second mode, the sensor is turned on, and when the environmental illuminance obtained based on the detection result by the sensor is higher than a predetermined environmental illuminance, the light source is turned off, and when lower, the light source is turned on. In such a case, by turning the light source off, the power consumption is saved accordingly (S4). In the case of the third mode, the sensor is turned off, and the light source is turned on/off manually. In such a case, the sensor doesn't consume the power (S5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a non-light emitting type display panel such as a liquid crystal display panel.

[0002]

2. Description of the Related Art A display device having a non-light-emitting type display panel such as a liquid crystal display panel is roughly classified into a transmission-type display device using transmitted light and a reflection-type display device using reflected light. There is a reflective type for displaying, and a reflective and transmissive type that combines these two types. In the case of a reflective and transmissive display device, although not shown, a transflective semi-reflective plate is generally arranged on the back side of a non-emissive display panel, and a backlight is arranged on the back side. It has a structure. And when used as a transmissive type, the backlight is turned on, the light from the backlight is transmitted through the semi-transmissive semi-reflective plate and the display panel, and emitted to the front side of the display panel,
The display is thereby performed. On the other hand, when used as a reflection type, the backlight is not turned on, and external light incident from the front side of the display panel is transmitted through the display panel and reflected by the transflective plate, and the reflected light is displayed. The light is transmitted through the panel and emitted to the front side of the display panel, thereby performing display.

[0003]

By the way, in such a display device, display can be performed by simultaneously using both light from the backlight and external light. In this case, the illuminance of the external light is detected by the illuminance detection sensor, and the luminance of the light from the backlight is adjusted based on the detection result, so that the screen luminance is suitable for the illuminance of the external light at that time. It is conceivable to make the screen brightness. However, in an environment in which sufficient screen luminance can be obtained only by external light, when display is performed by simultaneously using both light from the backlight and external light, power is wasted. Further, since the illuminance detection sensor also consumes power, this power consumption cannot be ridiculous. It is an object of the present invention to be able to save power.

[0004]

According to the first aspect of the present invention,
A non-light-emitting display panel, and external light that is disposed on the back side of the display panel and emits light toward the back side of the display panel, and is incident on the front side of the display panel and transmitted through the display panel. Reflection and light emission means for reflecting light toward the back surface of the display panel, an illuminance detection sensor for detecting environmental illuminance, and light emission for controlling light emission of the reflection and light emission means based on a detection result by the illuminance detection sensor. Comprising a control means, by the light emission control means, based on a detection result detected by the illuminance detection sensor,
A first mode in which at least the brightness of the light from the reflection and light emitting means is adjusted to control the screen brightness to be a suitable screen brightness with respect to the environmental illuminance at that time; and a first mode in which the screen brightness is detected by the illuminance detection sensor. When the environmental illuminance obtained based on the detected result is higher than a preset environmental illuminance, the light emission of the reflection / light emission unit is turned off, and when the environment illuminance is low, the light emission of the reflection / light emission unit is turned on. And the second mode to be controlled can be selected alternatively. According to the first aspect of the present invention, when the second mode is selected, when the environmental illuminance is higher than a preset environmental illuminance, that is, when sufficient screen luminance is obtained only by external light, the reflection Since the light emission of the light emitting means is turned off, power can be saved. Next, according to a second aspect of the present invention, the light emission control means controls the illuminance detection sensor to be turned off, and controls the light emission of the reflection and light emission means to be manually turned on and off. The mode 3 can be alternatively selected. According to the second aspect of the present invention, the light emission of the reflection and light emission means is turned on,
In the case where the turning off is performed manually, the turning on and off may be controlled according to the degree of the environmental illuminance determined by the user. Therefore, there is no problem even if the illuminance detecting sensor is turned off, and power can be saved. Next, the invention according to claim 3 is characterized in that the light emission control means controls the illuminance detection sensor for at least one of the first and second modes during a preset time of day. It is provided with a function of turning off the illuminance detection sensor at other times. Further, the invention according to claim 4 is characterized in that the light emission control means has a function of changing a preset time for turning off the illuminance detection sensor according to a calendar. According to the third or fourth aspect of the present invention, when the preset time is, for example, from 6:00 pm to 5:00 am of the next day, this time zone is approximately several thousand lux even if it is a bright place at night. Therefore, it is not necessary to consider external light much, and therefore, there is no problem even if the illuminance detection sensor is turned off, so that power can be saved. Next, the invention according to claim 5, wherein the light emission control means turns on the illuminance detection sensor according to preset schedule data in at least one of the first and second modes. This is provided with a function of controlling turning off. According to the invention described in claim 5, in the schedule data set in advance,
If there is no need to use an illuminance detection sensor, there is no problem even if the illuminance detection sensor is turned off, so that power can be saved.

[0005]

FIG. 1 shows a main part of a reflection / transmission type liquid crystal display device to which an embodiment of the present invention is applied. This liquid crystal display device includes a non-light emitting type liquid crystal display panel 1. Although not shown in detail, the liquid crystal display panel 1 has a pair of glass substrates 2 and 3 bonded to each other with a substantially frame-shaped sealing material 4 interposed between the two glass substrates 2 and 3 inside the sealing material 4. Liquid crystal is sealed, and polarizing plates 5 and 6 are attached to the surfaces of the glass substrates 2 and 3. As the liquid crystal display panel 1 in this case,
Any of a segment system, a simple matrix system, an active matrix system, etc. may be used, and a TN (twisted nematic) type, STN (super twisted nematic) type, ECB (birefringence effect) type, etc. may be used. In short, any non-light-emitting type may be used.

On the back side of the liquid crystal display panel 1, a backlight (reflection / light emitting means) 11 having a reflection function is arranged. The backlight 11 includes an optical sheet 12 provided on the back surface of the liquid crystal display panel 1 and the optical sheet 12.
A light diffusion layer 13 provided on the back surface of the light diffusion layer 13;
An optical member 14 provided on the back surface of the optical member 14;
And a light source 16 provided on a predetermined one end surface side of the light guide 15.
The light source 16 includes a linear fluorescent tube 17 and a reflector 18 for reflecting light from the fluorescent tube 17 toward one end surface of the light guide 15.

As shown in FIG. 2, the light guide 15 is made of an acrylic resin or the like, and has a flat back surface and a predetermined one end surface perpendicular to the back surface.
The surface has a step-like structure that gradually becomes thinner from the light incident surface 21 side to the other end surface side. In this case, the step-like surface includes a plurality of step surfaces 22 parallel to the back surface and a step surface (light emitting surface) 23 perpendicular to these step surfaces 22. On each of the step surfaces 22, a reflection film 24 made of a deposited film of aluminum or the like is provided via a base film (not shown) made of silicon oxide. A reflection plate 25 is provided on the back surface of the light guide 15. The light guide 15 is disposed on the back surface side of the liquid crystal display panel 1 with its back surface appropriately inclined with respect to the liquid crystal display panel 1.

As shown in FIG. 2, the optical member 14 is made of an acrylic resin or the like, has a flat surface, and has a plurality of triangular projections 31 on the rear surface.
Are formed at a constant pitch. In this case, the interface between one side surface of the protrusion 31 and the air is a first optical interface 32, and the interface between the other side surface of the protrusion 31 and the air is a second optical interface 33. The interface between the back surface of the optical member 14 and the air between the projections 31 is a third optical interface 34. And the optical member 1
Numeral 4 is arranged on the light guide 15 with the apex of the protruding portion 31 approaching or in contact with the reflection film 24. In this state, the angle of the first optical interface 32 with respect to the step surface 22 of the light guide 15 (the angle of the first optical interface 32 on the side facing the step surface 23) is 90 ° or less, and the step surface 23
The surface is substantially parallel to or an inclined surface close thereto. The second optical interface 33 is an inclined surface whose angle with respect to a perpendicular to the surface of the optical member 14 is larger than the angle between the perpendicular and the first optical interface 32. The third optical interface 34 is a surface substantially parallel to the step surface 22 of the light guide 15 or an inclined surface close thereto. Note that the pitch of the projecting portions 31 of the optical member 14 is substantially the same as the pixel pitch of the liquid crystal display panel 1 or is a fraction of the pixel pitch. Further, the pitch of the step surface 22 of the light guide 15 is slightly larger than the pitch of the protruding portions 31 of the optical member 14.

The light diffusion layer 13 is formed by applying a transparent adhesive in which light scattering fine particles are dispersed on the surface of the optical member 14, for example. And the optical sheet 12
It is attached to the surface of the optical member 14 via the light diffusion layer 13. The liquid crystal display panel 1 is attached to the surface of the optical sheet 12 via a transparent adhesive or a double-sided adhesive sheet 35. As shown in FIG. 3, the optical sheet 12 has a transmission axis P and a reflection axis S that are substantially orthogonal to each other.
And transmits light of a polarization component (P polarization component) along the transmission axis P, and a polarization component (S polarization component) along the reflection axis S.
Light is reflected. That is, when light including both the P-polarized light component along the transmission axis P and the S-polarized light component along the reflection axis S is incident from the back surface side of the optical sheet 12, the incident light The light of the P polarization component along the transmission axis P is transmitted through the optical sheet 12, and the light of the S polarization component along the reflection axis S is reflected by the optical sheet 12.
Such a semi-transmissive and semi-reflective characteristic is the same for incident light from the surface side of the optical sheet 12.

When the liquid crystal display device is used as a transmission type, the fluorescent tube 17 is turned on. Then, the light from the fluorescent tube 17 and the reflected light reflected by the reflector 18 are incident on the light incident surface 21 of the light guide 15. The incident light is reflected by the reflection film 24 and the reflection plate 25 while being reflected by the light guide 1 as shown by a solid arrow in FIG. 2, for example.
5 travels in the horizontal direction, and is emitted from each step surface (light emitting surface) 23. The outgoing light is also applied to the first optical interface 32 of the optical member 14 as shown by the solid arrow in FIG.
And is totally reflected by the second optical interface 33, exits from the surface of the optical member 14, enters the light scattering layer 13 and is scattered. Of the scattered light, the light of the P-polarized component passes through the optical sheet 12 and is incident on the back surface of the liquid crystal display panel 1, and the light of the S-polarized component is reflected by the optical sheet 12. However, the light reflected by the optical sheet 12 is reflected by the reflection film 24 and is scattered again by the light scattering layer 13. Of the scattered light, the light of the P-polarized component passes through the optical sheet 12 and is incident on the back surface of the liquid crystal display panel 1, and the light of the S-polarized component is reflected by the optical sheet 12. By repeating such a process, most of the light emitted from each step surface 23 is incident on the back surface of the liquid crystal display panel 1. Note that the transmission axis of the optical sheet 12 and the transmission axis of the polarizing plate 6 on the back side of the liquid crystal display panel 1 are substantially parallel to each other. Then, the light incident on the back surface of the liquid crystal display panel 1 passes through the liquid crystal display panel 1 and is emitted to the front surface side of the liquid crystal display panel 1, whereby display is performed.

On the other hand, when the liquid crystal display device is used as a reflection type, external light is used without turning on the fluorescent tube 17. That is, external light (linearly polarized light) incident from the surface side of the liquid crystal display panel 1 is
Through. The transmitted light is transmitted through the optical sheet 12, the light diffusion layer 13 and the optical member 14 in order, as shown by a dotted arrow in FIG.
This reflected light passes through the optical member 14 and is diffused by the light diffusion layer 13. Most of the diffused light passes through the optical sheet 12 and is transmitted through the liquid crystal display panel 1 in the same manner as described above.
Is incident on the back surface of. This incident light is transmitted to the liquid crystal display panel 1
And is emitted to the front side of the liquid crystal display panel 1 to perform display.

Next, in this liquid crystal display device, the light source 1
A case in which display is performed by simultaneously using both the light from the light source 6 and the external light will be described. By the way, the suitable screen luminance of the liquid crystal display panel 1 (the luminance at which the display can be observed with sufficient brightness under the use environment) differs depending on the illuminance of the use environment (hereinafter referred to as environment illuminance). ,
Depending on the ambient illumination, the screen may be too dazzling or too dark. For example, under a high illuminance use environment exceeding 100,000 lux, such as under direct sunlight in summer, it will be too dazzling.

Therefore, in this liquid crystal display device, in order to obtain a suitable screen luminance that is not excessively dazzling even in a use environment of high illuminance exceeding 100,000 lux, such as in direct sunlight in summer, the liquid crystal display device is mainly provided with a reflective surface. The reflectance of the entire device determined by the reflectance of external light by the film 24 and the transmittance of light of the liquid crystal display panel 1 (the intensity of external light incident from the surface side of the liquid crystal display panel 1 and the reflection by the reflective film 24 (Ratio with the intensity of external light emitted to the front side of the liquid crystal display panel 1)
Is set lower than that of a normal reflective liquid crystal display device using only external light.

Further, by controlling the brightness of the light from the light source 16 in accordance with the ambient illuminance, the screen brightness of the liquid crystal display panel 1 due to both the light from the light source 16 and the external light is preferably adjusted in accordance with the environmental illuminance. The screen brightness is set. That is, in this liquid crystal display device, the light source 16
Light source control means (light emission control means) 41 is provided to control the brightness of light from the light source. Light source control means 41
Is an illuminance detection sensor 42 for detecting environmental illuminance, and means for controlling the luminance of light from the light source 16 based on the detection result detected by the illuminance detection sensor 42 (light source luminance adjustment unit 43 and light source driving unit 44) It consists of

The illuminance detection sensor 42 has a light receiving surface substantially parallel to the surface of the liquid crystal display panel 1 in order to measure the same environmental illuminance as the illuminance of external light incident on the surface of the liquid crystal display panel 1. It is arranged near the liquid crystal display panel 1. The light source luminance adjustment unit 43 sets the value of the luminance of the light from the light source 16 based on the detection result detected by the illuminance detection sensor 42, and sets the screen luminance of the liquid crystal display panel 1 to a predetermined luminance according to the environmental illuminance. It is adjusted to be within the range. The light source driving unit 44 drives the light source 16 (the fluorescent tube 17) such that the light source 16 emits light having a luminance corresponding to the luminance value from the light source luminance adjusting unit 43.

Next, the control of the brightness of the light from the light source 16 by the light source control means 41 in accordance with the ambient illuminance will be described with specific numerical values. First, FIG. 4 shows the relationship between the screen luminance of the liquid crystal display panel 1 and the environmental illuminance in this case. As a prerequisite, a suitable screen luminance of the liquid crystal display panel 1 according to the environmental illuminance is 20 to 200 nits at an ambient illuminance of 50 lux such as under a street lamp at night, such as in a room when indoor lighting is turned on. 1000
Lux ambient illuminance is 30-300 nits, and 30000 lux ambient illuminance such as shade of trees in fine weather is 400-4
000 nits, more preferably 20 to 60 nits at 50 lux environmental illuminance, 60 to 200 nits at 1000 lux environmental illuminance, and 1000 to 3000 nits at 30,000 lux environmental illuminance.

Now, the screen luminance L (nit) of the liquid crystal display panel 1 is I (lux) for the environmental illuminance, B (nit) for the luminance of light from the light source 16, and T for the light transmittance of the liquid crystal display panel 1. (%), The reflectance of the above-described device as a whole is R (%)
Is obtained from the following equation (1). L = I × R / 400 + B × T / 100 (1)

Therefore, first, the screen luminance L of the liquid crystal display panel 1 is 20 to 200 nits at an environmental illuminance of 50 lux, 30 to 300 nits at an environmental illuminance of 1000 lux,
The luminance of the light from the light source 16 is controlled by the light source control means according to the environmental illuminance so that the luminance represented by a quadratic function satisfying the range of 400 to 4000 nits at the environmental illuminance of 30,000 lux, respectively. That is, the control condition of the luminance of the light from the light source 16 in this case is obtained from the above equation (1), and is as shown in the following equation (2). −2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 ≦ L ≦ −3 × 10 ⁻⁷ × I ² + 0.113 × I + 150 ... (2)

In FIG. 4, curves M ₁ and M ₂ show the maximum and minimum values of the screen luminance L obtained from the above equation (2). That is, the curves M ₁ and M ₂ are expressed by the following equation (3):
It is a curve respectively represented by (4). L (M ₁ ) = − 3 × 10 ⁻⁷ × I ² + 0.113 × I + 150 (3) L (M ₂ ) = − 2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 (4) The range M between the two curves M ₁ and M ₂ is a range of a suitable screen luminance of the liquid crystal display panel 1 according to the environmental illuminance.

Next, second, the screen luminance L of the liquid crystal display panel 1 is set to 20 to 60 nits at an environmental illuminance of 50 lux.
60-200 nits at 300 lux lux, 300
The light source control means controls the luminance of the light from the light source 16 according to the environmental illuminance so that the luminance represented by a quadratic function that satisfies the range of 1000 to 3000 nits at the environmental illuminance of 00 lux. That is, the control condition of the luminance of the light from the light source 16 in this case is obtained from the above equation (1), and is as shown in the following equation (5). −9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 ≦ L ≦ −2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50 ... (5)

In FIG. 4, curves N ₁ and N ₂ indicate the maximum and minimum values of the screen luminance L obtained from the above equation (5). That is, the curves N ₁ and N ₂ are given by the following equation (6):
It is a curve respectively represented by (7). L (N ₁ ) = − 2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50 (6) L (N ₂ ) = − 9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 (7) The range N between the two curves N ₁ and N ₂ is a more preferable range of the screen luminance of the liquid crystal display panel 1 according to the environmental illuminance.

As described above, in this liquid crystal display device, the luminance of the light from the light source 16 is controlled by the light source control means 41 in accordance with the ambient illuminance, so that the screen luminance of the liquid crystal display panel 1 is represented by the curves M ₁ and M ₁ . A range M between the _two , more preferably a range N between the curves N ₁ and N ₂ . This allows
The screen brightness of the liquid crystal display panel 1 can be made favorable or more favorable in a wide range of environmental illuminance from low illuminance to high illuminance.

The two-dot chain line in FIG. 4 represents, for comparison, the screen luminance of a normal reflection type liquid crystal display device using only external light. The screen luminance indicated by the two-dot chain line changes linearly with the change in environmental illuminance. Then, in this conventional reflection type liquid crystal display device, ambient illuminance corresponding to the range M between curves M _1, M ₂ ranges from about 300 to about 5000 lux, the range between the curve N _1, N ₂ N
Is in the range of about 500 to about 2000 lux. Therefore, at a higher ambient illuminance, the screen of the liquid crystal display panel becomes too bright, and for example, under a high illuminance of more than 100,000 lux such as under direct sunlight in summer, the screen of the liquid crystal display panel becomes too dazzling. The display becomes difficult to see. On the other hand, if the ambient illumination is lower than that,
The screen of the liquid crystal display panel becomes too dark, and, for example, in a dark use environment such as outdoors at night, it is not possible to obtain a screen luminance enough to make the display visible.

Next, FIG. 5 shows a calculation relationship between the screen luminance of the liquid crystal display panel 1 and the environmental illuminance by only the light from the light source 16. As a precondition, first, the range of the environmental illuminance in which the screen luminance satisfying the above equation (2) is obtained using only the light from the light source 16 is 0 to about 120,000.
Secondly, the range of the ambient illuminance at which the screen luminance satisfying the above expression (5) is obtained using only the light from the light source 16 is 0 to about 63000 lux.

First, in FIG. 5, the curves M ₁₁ and M ₂₂ represent the maximum value (M _{1 in} FIG. 4) and the minimum value (M _{2 in} FIG. 4) of the screen luminance obtained by the above equation (2). ) Are curves respectively representing the screen luminance by only the light from the light source 16 for obtaining). Therefore, the screen brightness by only the light from the light source 16 for obtaining the screen brightness that satisfies the above equation (2) is in the range between these two curves M ₁₁ and M ₂₂ . Note that, in calculation, as shown in FIG.
Becomes more than lux screen brightness represented by the curve M ₂₂ 0
Since the light is emitted from the light source 16, the screen luminance does not become 0 nit or less. Therefore, at an ambient illuminance of about 300 lux or more, the above equation (2)
Screen brightness by only the light from the light source 16 for obtaining a screen brightness that satisfies is the range higher than or less 0 knitted screen brightness represented by curve M _11.

Second, in FIG. 5, the curves N ₁₁ and N ₂₂ represent the maximum value (N _{1 in} FIG. 4) and the minimum value (N _{2 in} FIG. 4) of the screen luminance obtained by the above equation (5). Light source 16 to obtain
7 are curves respectively representing the screen luminance by only the light from. Therefore, the screen brightness by only the light from the light source 16 for obtaining a screen brightness that satisfies the above expression (5) is in the range between the two curves N _11, N _22. In this case as well, the calculation shows that the environmental illuminance is about 800, as shown in FIG.
It becomes more than lux screen brightness represented by curve N ₂₂ 0
Since the light is emitted from the light source 16, the screen luminance does not become 0 nit or less. Therefore, also in this case, at an environment illumination of about 800 lux or more,
Light source 16 for obtaining a screen luminance satisfying the above equation (5)
Screen brightness by only the light from a range higher than or less 0 knitted screen brightness represented by curve N _11.

Next, a specific example of light source control in the liquid crystal display device will be described. First, FIG. 6 schematically shows a circuit configuration of the light source control means 41 in this case.
The light source control means 41 has a CPU 51. CP
U51 is connected to each unit through a bus line 52 such as a data bus. The ROM 53 is a memory in which a program and the like for performing circuit control are written. RAM
Numeral 54 is for temporarily storing data as described later. The operation input unit 55 is a data input unit for inputting various data using a power button, a mode selection button, a light source on / off button, a light source brightness adjustment knob, and the like. The mode selection button automatically selects a first mode described later when the power button is turned on, and each time the button is pressed thereafter, a second mode described later, a third mode described later, and a first mode described later. Are sequentially selected. The sensor input unit 56 receives and processes a light detection signal output from the illuminance detection sensor 42, and outputs light detection data corresponding to the signal. The light source driving unit 44 drives the light source 16.

Next, the operation of the light source control means 41 will be described with reference to the flowchart shown in FIG. First, in step S1, the power button is turned on (Ye
s) Then, the first mode is selected, and the first mode selection data is temporarily stored in the RAM 54. Next, in step S2, the CPU 51 determines that the mode selection data temporarily stored in the RAM 54 is the first mode, and executes the first mode (step S2).
3). In the first mode, the illuminance detection sensor 42 is turned on, and the luminance of the light from the light source 16 is controlled based on the detection result detected by the illuminance detection sensor 42. , For example, a screen luminance that becomes a center line between the curves N ₁ and N ₂ in FIG.

Next, in the state where the power button is on (step S1, Yes), when the mode selection button is pressed once, the second mode is selected, and the second mode selection data is temporarily stored in the RAM 54. It is memorized. Next, in step S2, the CPU 51 determines that the mode selection data temporarily stored in the RAM 54 is the second mode, and executes the second mode (step S2).
4). In the second mode, as shown in FIG. 8, the illuminance detection sensor 42 is turned on (step S11), and the environment illuminance obtained based on the detection result detected by the illuminance detection sensor 42 is set to a predetermined environment. When the illuminance is higher (Step S12, Yes), the light source 16 is turned off (Step S13), and when the illuminance is lower (Step S12, No), the light source 16 is turned on (Step S14). For example, as apparent from FIG. 5, when the environmental illuminance is 1000 lux (about room illumination when is lit room lighting) above, screen brightness represented by the curve M ₂₂ and curve N ₂₂ and the both 0 knitted or less Become. Therefore, when the ambient illuminance is 1000 lux or more, the above equation (2) is obtained even when the light source 16 is turned off.
And a screen luminance satisfying the above equation (5) can be obtained. Therefore, in the second mode, the light source 16 is turned off when the environmental illuminance is 1000 lux or more, and the light source 16 is turned on when the environmental illuminance is less than 1000 lux. Thus, the environmental illuminance is 1
Since the light source 16 is turned off at the time of 000 lux or more, power can be saved.

Next, when the power button is on (step S1, Yes), the mode selection button is
When the button is pressed twice, the third mode is selected, and the third mode selection data is temporarily stored in the RAM 54. next,
In step S2, the CPU 51 determines that the mode selection data temporarily stored in the RAM 54 is the third mode, and executes the third mode (step S2).
5). In the third mode, the illuminance detection sensor 42 is turned off, and the light source 16 is turned on and off manually. That is, in the third mode, the user determines the degree of the environmental illuminance, and operates the light source on / off button accordingly to turn on / off the light source 16. When the light source luminance adjustment knob is operated, the luminance of the light source 16 is adjusted.
In this case, since the illuminance detection sensor 42 is turned off, the illuminance detection sensor 42 does not consume power.

Next, in the second mode, the illuminance detection sensor 42 is turned off during a preset time (for example, from 6:00 pm to 5:00 am of the next day), and at other times (from 5:00 am to pm At 6:00), the case where the illuminance detection sensor 42 is turned on will be described with reference to the flowchart shown in FIG. First, in step S21, the CPU 51
The current time obtained by referring to an internal clock (not shown) is stored in the RAM.
It is determined whether or not it is within a time (PM6 to AM5) set in advance in 54. If it is within the set time (Yes), the CPU 51 turns off the illuminance detection sensor 42 and turns on the light source 16 (step S22). That is, 6 pm
Since the time zone from time to 5:00 am of the next day is about several thousand lux even if it is a bright place at night, it is not necessary to consider external light much. Therefore, even if the illuminance detection sensor 42 is turned off, There is no problem and therefore power can be saved. On the other hand, if it is outside the set time (No),
It proceeds to step S11 in FIG.

Next, a case in which the preset time is changed according to the calendar will be described with reference to a flowchart shown in FIG. First, in step S31, the CPU 51 causes the RAM 54 to temporarily store date data obtained by referring to the internal clock. Next, in step S32, the CPU 51 reads the sunset and sunrise times of the date written in the ROM 53, and temporarily stores the read both time data in the RAM. Next, in step S33, C
The PU 51 determines whether or not the current time obtained by referring to the internal clock is within the time data. If it is within both time data (Yes), the CPU 51 turns off the illuminance detection sensor 42 and turns on the light source 16. on the other hand,
If it is outside the both time data (No), the process proceeds to step S11 in FIG.

Next, the case where the light source control is performed according to the schedule data in the second mode will be described with reference to the flowchart shown in FIG. In addition,
The schedule data is temporarily stored in the RAM 54 in advance. For example, it is assumed that a meeting is held in a company (indoor) from what time to what time of the month and at what time.
Now, in step S41, the CPU 51 determines whether or not there is schedule data at the current time. If there is no schedule data (No), the process proceeds to step S21 in FIG. When there is schedule data (Ye
In s), in step S42, the CPU 51 determines whether the schedule data is indoors.
If it is not indoors (No), the process proceeds to step S21 in FIG. If it is indoors (Yes), step S43
In, the CPU 51 turns off the illuminance detection sensor 42 and turns on the light source 16. That is, in the office where the meeting is held (indoors), the light source 1
6 is turned on. In other words, when there is no need to use the illuminance detection sensor 42, there is no problem even if the illuminance detection sensor 42 is turned off, so that power can be saved.

In the above description, a case has been described in which the screen luminance is set to be the center line between the curves N ₁ and N ₂ in FIG. 4, for example, in the first mode. However, in this case, the light source 16 is kept turned on. Therefore, in the first mode, the light source 16 may be turned off when the environmental illuminance becomes higher than 1000 lux, as in the case of the second mode. In this way, power can be saved.

As is apparent from FIG. 5, as an example, when the ambient illuminance is 300 lux or less, the light source 16
Even if the luminance of the image is constant at 70 nits, a suitable screen luminance can be obtained. In addition, environmental illuminance is 300 to 2000
In the case of lux, a suitable screen luminance can be obtained even if the luminance of the light source 16 is fixed at 140 nits. Further, when the ambient illuminance is 2000 lux or more, a suitable screen luminance can be obtained even when the fluorescent tube 17 is turned off. Therefore, in the case of the first mode, the environmental illuminance is 30
When the brightness is 0 lux or less, the brightness of the light source 16 is set to 70 nits, and when the environmental illuminance is 300 to 2000 lux, the light source 1
The light source 16 may be turned off when the luminance of the light source 6 is 140 nits and the environmental illuminance is 2000 lux or more.

In the above description, in the second mode, the illuminance detection sensor 42 is turned off and the light source 16 is turned on as shown in step S22 in FIG. 9, step S34 in FIG. 10, and step S43 in FIG. Although the description has been given of the case where the operation is performed, such a case can be applied to the first mode.

In the above description, the case where the light source 16 is simply turned on when the speed is less than 1000 lux in the second mode has been described, but the present invention is not limited to this. For example, the luminance of the light source 16, controlled to screen brightness in FIG. 4 is shown by a curve M _2, and,
The light source 16 may be turned off at an environmental illuminance of 5000 lux or more at which the screen luminance becomes about 100 nits.

In the above description, the case where the fluorescent tube 17 is used has been described. However, the present invention is not limited to this, and a linear light emitting diode array or the like may be used. In the above description, the case where the present invention is applied to a liquid crystal display device has been described. However, the present invention is not limited to this, and can be applied to a display device having another non-light emitting type display panel.

[0039]

As described above, according to the first aspect of the present invention, when the second mode is selected, when the environmental illuminance is higher than the preset environmental illuminance, that is, when only the external light is used. When sufficient screen luminance is obtained, the light emission of the reflection and light emission means is turned off, so that power can be saved. According to the second aspect of the present invention, when turning on and off the light emission of the reflection and light emission means manually, it is sufficient to control the on and off in accordance with the degree of environmental illuminance determined by the user, Therefore, there is no problem even if the illuminance detection sensor is turned off, and power can be saved. According to the third or fourth aspect of the present invention, when the preset time is, for example, from 6:00 pm to 5:00 am on the next day, this time zone is approximately several thousand lux even in a bright place at night. Therefore, it is not necessary to consider external light so much. Therefore, there is no problem even if the illuminance detection sensor is turned off, and power can be saved. Furthermore, according to the fifth aspect of the present invention, when it is not necessary to use the illuminance detection sensor in the preset schedule data, there is no problem even if the illuminance detection sensor is turned off, and thus power is saved. can do.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a liquid crystal display device to which an embodiment of the present invention is applied.

FIG. 2 is a diagram illustrating the progress of light in a part of a liquid crystal display device.

FIG. 3 is a perspective view illustrating an optical sheet.

FIG. 4 is a diagram showing a relationship between screen luminance of a liquid crystal display panel and environmental illuminance.

FIG. 5 is a view showing a calculation relationship between screen luminance of a liquid crystal display panel and environmental illuminance only by light from a light source.

FIG. 6 is a schematic diagram of a circuit configuration of a light source control unit.

FIG. 7 is a flowchart illustrating the operation of light source control.

FIG. 8 is a flowchart illustrating a second mode.

FIG. 9 is a flowchart shown to explain another first example of light source control.

FIG. 10 is a flowchart shown to explain another second example of light source control.

FIG. 11 is a flowchart shown to explain another third example of light source control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 11 Backlight 16 Light source 17 Fluorescent tube 41 Light source control means 42 Illuminance detection sensor

Claims (5)

[Claims] 1. A non-light-emitting display panel, disposed on a back side of the display panel, emitting light toward the back side of the display panel, and being incident on the front side of the display panel to receive light. Reflection and light emission means for reflecting external light transmitted through the display panel toward the back surface of the display panel, an illuminance detection sensor for detecting environmental illuminance, and light emission of the reflection and light emission means based on a detection result by the illuminance detection sensor. Light emission control means for controlling the light emission control means, based on the detection result detected by the illuminance detection sensor, by adjusting at least the brightness of the light from the reflection and light emission means, A first control for controlling the screen luminance to be a screen luminance suitable for the environmental illuminance at that time.
Mode, when the environmental illuminance obtained based on the detection result detected by the illuminance detection sensor is higher than a preset environmental illuminance, turns off the light emission of the reflection and light emission means, and when the environment illuminance is low, the reflection is low. A display device characterized in that it is possible to alternatively select a second mode for controlling the light emission of the light emission means to be turned on. 2. The invention according to claim 1, wherein the light emission control means controls the illuminance detection sensor to be turned off so that the light emission of the reflection and light emission means is manually turned on and off. Wherein the third mode can be selected alternatively. 3. The method according to claim 1, wherein
In the light emission control means, in at least one of the first and second modes, the illuminance detection sensor is turned off during a preset time of day, and the illuminance detection is performed at other times. A display device having a function of turning on a sensor. 4. The invention according to claim 3, wherein the light emission control means has a function of changing a preset time for turning off the illuminance detection sensor according to a calendar. Display device. 5. The invention according to claim 1, wherein said light emission control means responds to preset schedule data in at least one of said first and second modes. A display device having a function of controlling on / off of the illuminance detection sensor.