Indication device

Abstract

The present invention provides a display device that reproduces the optical properties of printed display media, and in particular, a display device that gives the impression that the display device is a printed medium such as paper. [Solution] In a display device, the light beam emitted from pixels within a specific area of ​​the display panel is controlled by a predetermined ratio of diffuse reflectance in relation to the light beam of ambient light incident on that specific area, and the emitted light beam is determined by the product of the incident light beam and the diffuse reflectance. This makes it possible to give the display on the display device the feeling of being on a printed medium such as paper.

Description

Technical Field

[0001] The present invention relates to a display device, and particularly to a display device that reproduces the diffused reflected light of a printed display medium.

[0002] Conventionally, display devices such as liquid crystal display devices and organic EL display devices are known. In these display devices, a method of controlling the display brightness according to the illuminance of external light is also known. In conventional display devices such as liquid crystal displays using a backlight, a method of increasing the brightness to enhance visibility when the surroundings are bright, while reducing the brightness to eliminate flicker when the surroundings are dark is common. Also, in darker places, it is required to reduce the brightness from the perspective of power saving.

[0003] On the other hand, the development of reflective displays such as electrophoretic displays and reflective liquid crystal displays that display similar to the optical characteristics of printed display media on paper such as copy paper, photographs, calendars, etc., which reflect ambient light such as external light for display, has also been carried out.

[0004] Patent Document 1 discloses a technique in a display device for adjusting the brightness and color tone according to the brightness of external light, changing the brightness of the display device for each part, or reducing the brightness of the corresponding part for display when it becomes a shadow of an object and the illuminance of external light decreases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] While the prior art and the technology disclosed in Patent Document 1 describe adjusting the brightness and color tone according to the brightness of the ambient light to change the brightness of the display device, they only describe adjusting the brightness from the standpoint of readability and power saving. Although Patent Document 1 describes that it is possible to provide an atmosphere like writing on actual paper, this only shows that the brightness of the image contained in the area that is cast by the pen is reduced to make it appear as if the shadow of the pen is being reflected. In other words, when the ambient light intensity is reduced due to the shadow of an object, the brightness of the area in question is reduced to match the reduced ambient light intensity.

[0007] Furthermore, even with reflective displays that reflect ambient light, such as external light, when displaying in color, the reflected light is greatly reduced due to light absorption by the three primary color filters, which may significantly decrease visibility compared to printed media.

[0008] Therefore, the present invention aims to provide a display device that reproduces the optical properties of a printed display medium, giving the viewer the sensation that the display device is a printed medium like paper, and to convey information without causing any discomfort by displaying it in a way that makes it appear as if it were a familiar printed medium. [Means for solving the problem]

[0009] The present invention comprises a display panel and at least one light sensor, and is characterized in that, in order to reproduce diffusely reflected light to ambient light on a printed display medium, the light beam emitted from a pixel in a specific area within the display panel is controlled to a predetermined ratio of diffuse reflectance. With the above configuration, the light beam emitted from the pixels is controlled by a predetermined ratio of diffuse reflectance, making it possible for the display device to reproduce the diffuse reflected light of a printed display medium, thus giving the user the feeling that the display device is a printed medium such as paper.

[0010] Furthermore, the diffuse reflectance can also be set to a value of 1 or less. Since the amount of light emitted from printing media such as paper is generally less than the amount of light emitted from display devices, setting the diffuse reflectance value to 1 or less makes it possible to better control diffusely reflected light.

[0011] Furthermore, the light sensor may be configured to detect the three primary colors of light individually, determine the diffuse reflectance for each of the three primary colors, and control the light beam emitted from the pixel based on these diffuse reflectances. This allows for the determination of the diffuse reflectance for each of the three primary colors, taking into account light diffusion and spectral absorption in various types of printing media such as paper, and enables control of the light beam based on these diffuse reflectances, thereby allowing for more precise control of diffusely reflected light.

[0012] Furthermore, the light sensors may be arranged as a two-dimensional array. This makes it possible to appropriately reflect the distribution of incident light beam to the display panel in each region. In addition, various locations can be selected for placement, such as the surface of the rear substrate, the surface of the front substrate, or the surface of other transparent substrates.

[0013] Furthermore, a black absorbing area may be formed on the surface on which the pixel's light sensor is located. This makes it possible to block display light that would interfere with the light sensor detecting ambient light.

[0014] Furthermore, a color filter for the three primary colors may be provided on the light-receiving surface of the light sensor. In this case, it is preferable to use a color filter equivalent to the color filter for the three primary colors of the pixel. This makes it possible to make the sensitivity of the light-receiving surface of the light sensor the same as the sensitivity of the pixel.

[0015] Furthermore, the display panel may be laminated with an anti-reflective layer or an anti-glare layer. This makes it possible to suppress specular reflection, which does not occur in printed display media such as paper, but does occur in conventional display devices.

[0016] Furthermore, the angular dependence of the emitted light intensity of the pixels may be such that, based on Lambert's cosine law, it becomes an even diffusion distribution of a perfect diffuser plate, that is, there is no angular dependence on the luminance (the luminance is isotropic), or the half-value angle of the luminance (the angle until the value becomes half of the front luminance) is as wide as 120° or more in the full angle and has a light distribution that gently decreases from the direction perpendicular to the substrate surface. Thereby, it becomes possible to reproduce the optical characteristics of a printing display medium such as paper. Also, when using a liquid crystal element, the backlight serving as a light source may have a similar light distribution.

Advantages of the Invention

[0017] According to the present invention, a display device that reproduces the optical characteristics of a printing display medium is provided, and it is possible to give a feeling as if the display device were a printing medium such as paper.

Brief Description of the Drawings

[0018] [Figure 1] It is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention. [Figure 2] It is a diagram showing the detailed configuration of a liquid crystal panel. [Figure 3] It is a diagram showing the cross section of a liquid crystal panel and a backlight. [Figure 4] It is a diagram showing the relationship between a pixel and a photosensor. [Figure 5] It is a diagram showing the relationship between the intensity of incident light, the output signal of a photosensor, and the intensity of reflected light of a printing display medium in a liquid crystal panel. [Figure 6] It is a modified example of the structure of a liquid crystal panel. [Figure 7] It is an image of a display experiment using a backlight approximated to Lambertian light distribution and a liquid crystal element.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 10 includes a liquid crystal panel 11, an image processing unit 12, an A / D converter 13, a backlight power supply circuit 14, and a backlight 15. The liquid crystal panel 11 includes a panel drive circuit 17 and a display area 18. As will be described later, the display area 18 includes a plurality of pixel circuits and a plurality of optical sensors arranged two-dimensionally.

[0020] Display data D1 and an output control signal OC are input from the outside to the image processing unit 12 of the liquid crystal display device 10. Display data processing is performed within the image processing unit 12, and display data D2 is output to the liquid crystal panel 11. The display data D2 is input to the panel drive circuit 17 of the liquid crystal panel 11, and the panel drive circuit 17 writes data to the pixel circuits in the display area 18 based on the display data D2. As a result, an image is displayed in the display area 18.

[0021] The backlight 15 is composed of LEDs and irradiates light as backlight from the back of the liquid crystal panel 11. The backlight power supply circuit 14 supplies and cuts off power to the backlight 15 based on a control signal output from the image processing unit 12. Also, as will be described later, based on signals from the optical sensors, it also controls the driving of the liquid crystal panel 11 and the control of the backlight 15. The backlight 15 is composed of white LEDs, but it is also possible to configure it by combining red, green, and blue LEDs.

[0022] In the panel drive circuit 17, an operation of writing a voltage to the pixel circuits of the liquid crystal panel 11 is performed. At the same time, an operation of reading a voltage corresponding to the amount of light received from the optical sensor 2 (not shown in FIG. 1) of the liquid crystal panel 11 is also performed. The signal SS output from the optical sensor is output outside the liquid crystal panel 11 and input to the A / D converter 13. The A / D converter 13 converts the analog signal output from the optical sensor 2 into a digital signal. The image processing unit 12 controls the driving of the liquid crystal panel 11 and the control of the backlight 15 based on the digital signal output from the A / D converter 13 by the control described later.

[0023] Figure 2 shows a detailed configuration of the liquid crystal panel 11. The pixel array of the display area 18 is equipped with m scan signal lines G1 to Gm and 3n data signal lines Sr1 to Srn, Sg1 to Sgn, and Sb1 to Sbn, and m × 3n pixel circuits are formed at the intersections of the scan signal lines and data signal lines. Furthermore, the pixel array of the display area 18 is equipped with an optical sensor 2 corresponding to each pixel circuit, sensor readout lines Rw1 to Rwm, and sensor lines Srw1 to Srwn, Sgw1 to Sgwn, and Sbw1 to Sbwn.

[0024] The scan signal lines G1 to Gm are arranged in parallel to each other. The data signal lines Sr1 to Srn, Sg1 to Sgn, and Sb1 to Sbn are all arranged parallel to each other so as to be perpendicular to the scan signal lines G1 to Gm, and pixel circuits 1 are provided at the intersections of the scan signal lines G1 to Gm and the data signal lines Sr1 to Srn, Sg1 to Sgn, and Sb1 to Sbn. Pixel circuits 1 are provided in m numbers in the direction parallel to the scan signal lines and 3n numbers in the direction parallel to the data signal lines, arranged in a two-dimensional manner. In the direction parallel to the data signal lines, red, green, and blue color filters are provided in order to form R (red) pixel circuit 1r, G (green) pixel circuit 1g, and B (blue) pixel circuit 1b in order, with three types of pixel circuits forming one pixel.

[0025] The pixel circuit 1 comprises a TFT 3 and a liquid crystal capacitor 4. The gate terminal of the TFT 3 is connected to the scan signal line, and the source terminal is connected to one of the data signal lines. The drain terminal is connected to the electrode of the liquid crystal capacitor. A common voltage is applied to electrodes other than the one to which the drain terminal is connected.

[0026] Around the display area 18, a scanning signal line drive circuit 31, a data signal line drive circuit 32, a sensor row drive circuit 33, a sensor column drive circuit 34, and switches (35, 36) are provided. The scanning signal line drive circuit 31, the data signal line drive circuit 32, the sensor row drive circuit 33, and the sensor column drive circuit 34 correspond to the panel drive circuit 17 in Figure 1. The data signal line drive circuit 32 has 3n output terminals corresponding to 3n data signal lines. A switch is provided between the data signal line drive circuit 32 and each data line.

[0027] The brightness of pixel circuit 1 is determined by the voltage written to pixel circuit 1. To write a voltage to pixel circuit 1, a high-level voltage to turn on the TFT3 is applied to the scan signal line Gi (where i is an integer from 1 to m), and the voltage to be written is applied to the data signal line Sxj (where x is one of r, g, or b; j is an integer from 1 to n). By writing a voltage corresponding to the display data D2 to pixel circuit 1, it is possible to set the brightness of each pixel to the desired level.

[0028] Figure 3 shows a cross-section of the liquid crystal panel 11 and the backlight 15. The liquid crystal panel 11 has a structure in which a liquid crystal layer 42 is sandwiched between two glass substrates 41a and 41b. Glass substrate 41a is provided with three color filters 43r, 43g, and 43b, a black absorption section 44, and a counter electrode 45. Glass substrate 41b is provided with a pixel electrode 46 and data signal lines 47. In this example, a light sensor 2 is also provided on glass substrate 41b. The photodiode 6 in the light sensor 2 is provided near the pixel electrode 46. Alignment films 48 are provided on the opposing surfaces of the glass substrates (41a, 41b), and a polarizing plate 49 is provided on the surface opposite to the surface where the alignment films 48 are provided. In Figure 3, the surface on the glass substrate 41a side is the front surface, and the surface on the glass substrate 41b side is the back surface. The backlight 15 is provided on the back surface, which is on the glass substrate 41b side. In Figure 3, the light sensor 2 is located near the pixel electrode 46 on the glass substrate 41b side, but it can also be located on the glass substrate 41a side, on the surface facing the glass substrate 41b, or on the side surface of the glass substrate 41a or glass substrate 41b.

[0029] In the example shown in Figure 2, one light sensor 2 is provided for each pixel circuit and includes a photodiode 6. The sensor readout line Rwi is connected to the anode electrode of the photodiode 6, and the sensor lines (Srwj, Sgwj, Sbwj (where j is an integer from 1 to n)) are connected to the cathode electrode of the photodiode 6. When a reverse bias voltage is applied to the sensor lines (Srwj, Sgwj, Sbwj (where j is an integer from 1 to n)) from the sensor train drive circuit 14, a current corresponding to the amount of incident light flows through the photodiode 6, causing the voltage at the cathode terminal of the photodiode 6 to drop. This makes it possible to determine the amount of light detected by the light sensor 2.

[0030] Furthermore, in the example shown in Figure 2, a simple configuration is used in which photodiodes are connected at the wiring intersections in the matrix circuit section. However, a configuration in which field-effect transistors for line selection, amplification transistors, reset transistors, and transfer transistors are provided at the intersections, and photodiodes are connected to the outputs of the transistors, is also possible. By using such a connection configuration, it is possible to obtain clear photodetection signals such as current and voltage with low electrical noise from each photodiode. As semiconductors used in field-effect transistors, amorphous or polycrystalline silicon and metal oxides, which are used in existing thin-film transistors, can be used.

[0031] In the liquid crystal panel 11, light is emitted directly by a backlight 15 located on the back side, and the brightness is controlled by the pixel circuit 1. On the other hand, printed display media such as paper do not have a light-emitting source like the backlight in a liquid crystal panel, so light incident from the outside is reflected off the surface of the paper and enters the observer's eye as diffusely reflected light. Therefore, generally, the amount of light emitted is less compared to the direct light emitted by the backlight in a liquid crystal panel, and the amount of light is also lower in relation to the amount of light incident from the outside.

[0032] This invention focuses on the difference in emitted light between these liquid crystal panels and printed display media such as paper. By controlling the direct emitted light from the backlight of the liquid crystal panel to be equivalent to the diffuse reflected light on paper, it is possible to display content in a way that makes it appear as if it were printed on paper, even though the display is being performed using a liquid crystal panel.

[0033] Figure 5(a) is a graph showing the relationship between light intensity, which represents the intensity of light incident on a unit area of ​​the liquid crystal panel 11, and the voltage signal output from the light sensor 2. As shown in this graph, light intensity and voltage signal are roughly proportional, although an offset voltage (Vs) exists. Based on this relationship, it is possible to determine parameters through actual measurements and calculate the light intensity relative to the voltage signal based on the determined parameters.

[0034] Figure 5(b) is a graph showing the relationship between light intensity, which represents the intensity of light incident on a unit area, and the intensity of the printed display medium, such as paper, at that time. As shown in this graph, the relationship between light intensity and reflected light intensity is generally proportional. Based on this relationship, it is possible to determine parameters through actual measurements and then calculate the reflected light intensity in relation to the light intensity based on these parameters. As explained earlier, this proportionality constant is generally a value of 1 or less.

[0035] In detecting the amount of incident ambient light, and in driving pixels in a liquid crystal panel, the average value of the output from the light sensor provided for each pixel is taken. However, it is also possible to calculate the amount of incident light by multiplying the output from each light sensor by the diffuse reflectance for each pixel.

[0036] Furthermore, although the example of providing an optical sensor 2 for each pixel circuit was described as shown in Figure 4, it is also possible to provide one optical sensor for each pixel, or even one for every many pixels. It is also possible to provide one optical sensor for the entire liquid crystal panel, or to provide multiple optical sensors for the periphery of the liquid crystal panel. As shown in Figure 4, when an optical sensor is provided for each red, green, and blue sub-pixel, the same color filter as that provided for the pixel can be used for each optical sensor to individually detect the three primary colors of red, green, and blue with a sensitivity similar to that of the pixel. In such a configuration, for each of the three primary colors, the diffuse reflectance according to the type of printing medium, such as paper, is determined in advance by actually irradiating the printing medium with light and determining the value of the diffuse reflected light.

[0037] Furthermore, it is generally known that the diffuse reflectance (total light reflectance) of white paper used for copy paper is 85-91%, and that of newspaper is 40-50%. By using these diffuse reflectance values, differences in paper quality can be easily represented. It is also useful to store multiple diffuse reflectance values ​​and switch between them as needed. Moreover, even among white surfaces, the diffuse reflectance of white cloth is 60-70%, and that of white tiles is 70-80%, so by using these diffuse reflectance values, surfaces other than paper can also be reproduced. In addition, if the present invention is composed of a three-primary-color sensor and display pixels, it is necessary to calculate and use the diffuse reflectance for each of the three primary colors on the paper. This makes it easy to reproduce not only the brightness of the paper but also its hue.

[0038] Furthermore, on the liquid crystal panel side, the relationship between the amount of incident ambient light and the output of the light sensor, and the relationship between the pixel drive state and the amount of light emitted from the pixel are determined in advance for each of the three primary colors. Then, for each of the three primary colors, the pixels in the liquid crystal panel are driven so that the amount of light emitted from the pixels in the liquid crystal panel is equal to the amount of light emitted with a diffuse reflectance obtained by multiplying the amount of incident ambient light detected by the light sensor by the diffuse reflectance of a specific print display medium.

[0039] The following describes specific examples of pre-adjustment, calibration, and driving methods for LCD panels. The panel is illuminated with a standard white light source at maximum illuminance, and the maximum input and output values ​​of the light sensor are set accordingly. The output value of the light sensor is made proportional to the light intensity of the light sensor. For the standard white light source, it is recommended to use the D50 or D65 light source, which are white standard light sources defined by the International Commission on Illumination. Under the illuminance provided by these light sources, the diffuse reflectance of a commercially available standard diffuse white plate is set to an ideal 100%, and the luminance is calculated using the formula luminance = illuminance / π, or the luminance of the standard diffuse white plate is determined by measuring it with a luminance meter. The three primary color driving signals are then adjusted so that the luminance value obtained in this way matches the luminance of the display. The three primary color driving signals at this time are associated with the maximum values ​​of each color.

[0040] Furthermore, the display's drive signal is set to change in proportion to the output signal of the light sensor. These adjustments ensure that the balance of the three primary colors—chromaticity, color temperature, and hue—is maintained in the display even when the intensity of the illumination changes. When adjusting the display's brightness, the drive signal may be adjusted while maintaining a constant balance of the three primary colors, or the backlight source (such as an LED) may be adjusted to save power.

[0041] On the other hand, measure the reflectance of the three primary colors of the paper you want to simulate. The reflectance of the paper can be roughly considered as the ratio of the decrease in brightness when paper is used instead of a standard diffuse white board. If the reflectance of each of the three primary colors of the paper is known, the drive signal of the display can be calculated by multiplying the ratio of these reflectances (less than or equal to 1) by the maximum drive signal when using a standard diffuse white board. For example, to reproduce the reflected light of white copy paper where the reflectance of all three primary colors is equally 80%, the actual drive signal can be obtained by multiplying the drive signals of each of the three primary colors by 80%. If we assume that the reflected light of white copy paper has a Lambert distribution, the brightness of white copy paper can also be roughly approximated using the formula Brightness = Reflectance × Illuminance / π.

[0042] This allows the display's three primary color brightness to be automatically determined and controlled even when the lighting environment changes. For example, if the light source is switched from standard white light to lighting with different brightness and color temperature, the display's three primary color display will also change in accordance with the change in the light sensor's three primary color output, allowing the brightness and hue of white paper to be reproduced simultaneously on the display. Furthermore, when reproducing the reflected light of papers other than white copy paper (such as dull white paper or colored paper) on the display, the reflectance of the three primary colors of each paper can be determined using pre-determined values ​​or by measuring brightness. By multiplying these diffuse reflectances by the maximum drive level for each of the three primary colors, the drive level for each primary color can be determined. This allows the reflected light of papers with various diffuse reflectances to be reproduced as the display light.

[0043] Figure 6 shows a modified example of the liquid crystal panel structure in Figure 3. In the example in Figure 6, an anti-glare layer is provided on the outer surface of the polarizing plate 49 to suppress specular reflection. Unlike liquid crystal panels, printed display media such as paper do not have specular reflection on their surface. Therefore, by providing an anti-glare layer on the surface of the liquid crystal panel to suppress specular reflection, it is possible to make the display closer to that of printed display media such as paper. In addition, although an anti-glare layer is provided on the outer surface of the polarizing plate 49 in the example in Figure 6, it is also possible to provide a reflection suppression layer instead of an anti-glare layer.

[0044] Some papers and fabrics have patterns or designs on their surfaces. In such cases, the diffuse reflectance of the surface may differ depending on the presence or shape of the pattern. In these situations, by precisely determining the diffuse reflectance of each area of ​​the paper or fabric according to the pattern in advance, and then multiplying each area by the different diffuse reflectance according to the pattern when displaying it on the LCD panel, it becomes possible to reproduce the texture of the paper or fabric while also displaying the pattern by changing the brightness.

[0045] In these embodiments, we have described using liquid crystal displays, but these are not limited to liquid crystal displays and can also be applied to self-emissive displays such as organic EL displays. In the case of self-emissive displays, the driving method is the same as for liquid crystal displays; the light beam to be emitted is determined by the product of the incident light beam and the diffuse reflectance, and then driven.

[0046] While Lambertian light distribution is ideal for display devices, measurements of the half-angle of brightness of white copy paper revealed it to be approximately 160°, indicating a light distribution that gradually decreases from the direction perpendicular to the display surface. Therefore, a prototype backlight box (with a half-angle of brightness of 160°) with diffused LED light to approximate an isotropic Lambertian light distribution was fabricated and stacked with a commercially available liquid crystal element for display experiments. As a result, it was confirmed that a high-quality display image indistinguishable from color printed paper could be obtained, even when viewed from the front or at an angle. Figure 7 shows the results of comparing the prototype device with printed images under indoor lighting.

[0047] Furthermore, it has been confirmed that even when a strong diffuser plate is laminated to an existing light guide plate backlight, a light distribution distribution close to the Lambert distribution (half-angle of brightness of 160°) can be obtained. In this case, the stronger the diffusion effect of the diffuser plate, the closer the distribution becomes to the Lambert distribution, but there is a risk of a decrease in brightness. In addition, in the lamination relationship with polarizing plates, liquid crystal panels, light diffusion films, etc., if an air layer is present between them, Fresnel reflection occurs, and tilted light with a large incident angle undergoes total internal reflection and is not emitted to the outside, thus not contributing to the light for display. In this case as well, brightness may decrease and the display may become darker. To prevent this, it is preferable to construct a close-fitting structure such as bonding or matching oil injection in the lamination of various optical components. This prevents a decrease in the intensity of obliquely emitted light and can significantly suppress the decrease in the half-angle of brightness due to Fresnel reflection.

[0048] On the other hand, increasing the light diffusion effect to widen the light distribution in order to bring the backlight closer to Lambertian distribution leads to a problem of decreased front brightness. Therefore, from a practical standpoint, it is desirable for the half-angle of brightness of the display device or backlight to be 120° or more. For the liquid crystal elements stacked on the backlight, it is desirable to use a display operation method that provides wide viewing angle characteristics, such as the in-plane switching liquid crystal method (IPS) or the vertical alignment liquid crystal method (VA).

[0049] <1> A display panel having pixels arranged in two dimensions to emit display light, It comprises at least one light sensor for detecting ambient light, In order to reproduce diffuse reflected light to ambient light in a printed display medium, In a specific area within the display panel, the light beam emitted from a pixel within the specific area is controlled by the product of a predetermined ratio of diffuse reflectance and the light beam of ambient light incident on the specific area of ​​the display panel, as detected by the light sensor. A display device characterized by the following features. <2> The aforementioned diffuse reflectance is less than or equal to 1. Characterized by <1> The display device described above. <3> The aforementioned light sensor is capable of individually detecting light of the three primary colors, The aforementioned diffuse reflectance is determined for each of the three primary colors of light. The light beam emitted from the pixels within the specified region is controlled based on the diffuse reflectance determined for each of the three primary colors of light. Characterized by <1> or <2> The display device described above. <4> The aforementioned optical sensors are arranged as a two-dimensional array. Characterized by <1> ~ <3> A display device as described in any of the following. <5> The light sensor is provided on one of the following surfaces: the surface of the rear substrate on which thin-film transistors for driving the pixels are formed, the inner or outer surface of the front substrate, or the surface of another transparent substrate to be laminated. Characterized by <1> ~ <4> A display device as described in any of the following. <6> A black absorbing portion is formed on the surface of the pixel on which the light sensor is provided. Characterized by <5> The display device described above. <7> A color filter for the three primary colors is provided on the light-receiving surface of the aforementioned light sensor. Characterized by <3> ~ <6> A display device as described in any of the following. <8> The aforementioned pixels are composed of liquid crystal elements or organic EL elements that are voltage-driven by thin-film transistors. Characterized by <1> ~ <7> A display device as described in any of the following. <9> The display panel is laminated with an anti-reflective layer or an anti-glare layer. Characterized by <1> ~ <8> A display device as described in any of the following. <10> The angular dependence of the synchrotron radiation intensity of the aforementioned pixels is such that, based on Lambert's cosine law, it exhibits a uniform diffusion distribution similar to that of a perfect diffuser, or the half-angle of brightness is 120° or greater, and the light distribution decreases smoothly from the direction perpendicular to the substrate surface. Characterized by <1> ~ <9> A display device as described in any of the following. <11> The orientation characteristics of the backlight used in the liquid crystal element are such that they result in a uniform diffusion distribution like that of a perfect diffuser, or the half-value of the brightness is 40° or more and decreases smoothly from the direction perpendicular to the substrate surface. Characterized by <1> ~ <10> A display device as described in any of the following.

[0050] <1> A liquid crystal display panel having pixels arranged in two dimensions to emit display light, A light sensor that detects ambient light, Equipped with a backlight, The aforementioned backlight has a diffuser plate stacked on top of it. The aforementioned liquid crystal display panel has a structure in which a liquid crystal layer is sandwiched between two glass substrates. Polarizing plates are provided in a tight-fitting structure on the opposite surfaces of the two glass substrates that face each other, and anti-glare layers are provided in a tight-fitting structure on the outer surfaces of the pair of polarizing plates. The aforementioned pixels are composed of liquid crystal elements that are voltage-driven by thin-film transistors. In order to reproduce diffuse reflected light to ambient light in a printed display medium, With respect to the light beam of ambient light detected by the light sensor positioned corresponding to a specific area of ​​the liquid crystal display panel, the light beam emitted from the pixels within the specific area is controlled by the product of a predetermined ratio of diffuse reflectance and the light beam of ambient light detected by the light sensor positioned corresponding to the specific area. The three primary color drive signals that set the brightness of the pixels when reproducing diffusely reflected light from ambient light on the printed display medium are adjusted based on the formula diffuse reflectance × illuminance / π, using the illuminance based on the luminous flux of ambient light detected by the light sensor positioned corresponding to a specific area of ​​the liquid crystal display panel. According to the formula, when the ambient light illuminance becomes "0", the brightness of the pixels is set to "0". A liquid crystal display device wherein the diffuse reflectance used in a calculation formula for adjusting the driving signals of the three primary colors that set the brightness of the aforementioned pixels has a value of 1 or less. [Explanation of symbols]

[0051] 1 Pixel Circuit 2. Light sensor 6 Photodiodes 10 LCD display device 11 LCD panel 12 Image Processing Unit 13 A / D Converter 14. Backlight power supply circuit 15 Backlight 17 Panel drive circuit 18 Display area 31 Scanning signal line drive circuit 32. Data signal line drive circuit 33 Sensor row drive circuit 34 Sensor Array Drive Circuit 41 Glass substrate 42 liquid crystal layers 43 Color Filters 44 Black absorbent area 45 Counter electrode 46 pixel electrodes 48 Alignment film 49 Polarizing plate

Claims

[Claim 1] A display panel having pixels arranged two-dimensionally to emit display light, It is equipped with a light sensor that detects ambient light, In order to reproduce diffuse reflected light to ambient light in a printed display medium, With respect to the luminous flux of ambient light detected by the light sensor positioned corresponding to a specific area of ​​the display panel, the luminous flux emitted from a pixel within the specific area is controlled by the product of a predetermined ratio of diffuse reflectance and the luminous flux of ambient light detected by the light sensor positioned corresponding to the specific area. The drive signal for setting the brightness of a pixel when reproducing diffusely reflected light from ambient light on the printed display medium is adjusted based on the formula diffuse reflectance × illuminance / π, using the illuminance based on the luminous flux of ambient light detected by the light sensor positioned corresponding to a specific area of ​​the display panel. According to the formula, when the illuminance of ambient light becomes "0", the brightness of the pixel is set to "0". A display device wherein the diffuse reflectance used in the calculation formula for adjusting the drive signal that sets the brightness of the pixel has a value of 1 or less.

Images