TWI408651B - Liquid crystal display - Google Patents

Abstract

This invention discloses an active matrix liquid crystal display device (LCD), an operating method and an electrode device thereof. The liquid crystal display device comprises a pixel array and a voltage source. The pixel array is composed of a plurality of pixel elements. The voltage source supplies signal voltages to the pixel array for controlling brightness of the pixel array and displaying an image; different signal voltages are applied to adjacent pixel elements or sub-pixels, respectively. An averaged brightness of the adjacent elements or sub-pixels displays a typical gamma curve while viewing right from the front, displays a constant level within a specified color level (signal voltage) range while viewing at a skew angle from the front and displays an image to a visibly unidentifiable degree when viewed at a skew position from the front. This invention applies signal voltages with different level to adjacent pixels to change the image contrast, such than the image displays anormal predetermined image when viewing from the front and displays an image that cannot be identified when viewing at a skew position, thereby guaranteeing the privacy projection.

Description

Liquid crystal display device

The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device having an anti-peep function.

In the active matrix type liquid crystal display device, two transparent substrates are provided, and pixel electrodes are provided on the opposite surfaces thereof, and a liquid crystal layer is disposed between the gaps of the two transparent substrates, and the pixel electrodes on the transparent substrate surface are arranged in a matrix to display In the pixel, a switching element for ON and OFF switching is provided next to each pixel electrode.

In general, liquid crystal display devices are expected to be able to see a display screen from a wide-angle position as much as possible, that is, a wide-angle field of view is required. However, for example, when the liquid crystal display device is used in a portable product, it may be used in a place where a tram or the like is mixed, and at this time, it may be undesirable for a person around to see the display screen. Therefore, the use of the privacy mode requires the user to clearly see the display screen, and it is difficult for the person other than the user to see the display screen.

In response to the above requirements, the range of the image signal of the conventional liquid crystal display device must be narrowed, so that the range of the color gradation (signal voltage) is also narrowed, the contrast becomes poor, and the pixel display when viewed from the front is also generated. The problem of deterioration.

For example, a method of changing the viewing angle of a liquid crystal display panel is proposed in Japanese Patent Laid-Open Publication No. Hei 09-230377. This method is implemented by a vertical alignment type nematic (VAN) liquid crystal mode. In the VAN mode, in order to prevent voyeurism, the angle of view having a tilt range becomes very narrow, and the use in the privacy mode is insufficient.

Further, for example, Japanese Patent Laid-Open Publication No. 2007-17988 proposes to use two liquid crystal display panel display pixels for switching liquid crystal display between a first mode in which a wide angle is visible and a second mode in which only a narrow angle is visible. However, this method uses a two-piece panel, the device becomes thicker, and there is also a problem of high cost.

The object of the present invention is to solve the above problems, which does not require special processes or controls. Simply speaking, when viewed from the front, normal brightness and contrast image display can be maintained, while from a deviation from the front side, by specific The color or the interlaced pattern or the like is displayed without being clearly displayed, and thus a liquid crystal display device usable in a privacy mode is provided.

According to the present invention, an active matrix type liquid crystal display device including a pixel array and a voltage source can be provided. A pixel array is composed of a plurality of pixel elements. The voltage source supplies a plurality of signal voltages to the pixel array for controlling the brightness of the pixel array and displaying the image. Among them, adjacent pixel elements will respectively give different levels of signal voltage. The average brightness of adjacent pixel elements exhibits a general gamma curve as the signal voltage changes in relation to the front view active matrix type liquid crystal display device to display the desired image. And the average brightness of the adjacent pixel elements is maintained at a fixed value within a specific color gradation (signal voltage) when the gradation of the active matrix type liquid crystal display device is shifted with the change of the signal voltage. Change the image contrast to show an unrecognizable image. Therefore, the image viewed from the front can display the original image, and when viewed from the oblique surface, the image is difficult to see due to the contrast change.

The active matrix type liquid crystal display device described above, wherein the pixel element is For a pixel or a sub-pixel divided by a pixel, for example, a pixel of one color is further divided into two.

The active matrix type liquid crystal display device described above further includes a storage device and a look-up table. The storage device is configured to store pixel data to be input to the pixel array; the comparison table is connected to the storage device, and records a plurality of voltage values corresponding to the pixel data, which can output different voltage values to the adjacent pixel elements. In order to distinguish between the brightness of the front view and the squint in the privacy mode enabled state.

The active matrix type liquid crystal display device described above further includes a switch that communicates with the look-up table and can be controlled to switch the active matrix type liquid crystal display device to selectively enter a privacy mode enabled state or a privacy mode disabled state. .

In the active matrix type liquid crystal display device described above, when the active matrix type liquid crystal display device selectively enters the privacy mode disabled state, another comparison table connected to the storage device is used to output a voltage to the pixel array.

The active matrix type liquid crystal display device described above, wherein the voltage value is recorded in a digital form in a look-up table, and the active matrix type liquid crystal display device further includes a digital analog converter, which is in communication with the comparison table for applying The voltage value is converted to an analog form before the voltage value reaches the adjacent pixel element.

In the active matrix type liquid crystal display device described above, the specific signal voltage range is 20% to 80% of the signal voltage range which is output to the entire gamma curve of the pixel array.

In the active matrix type liquid crystal display device described above, in order to make it difficult to see the original image from the oblique angle, at least two different fixed luminances are mixed in a specific color gradation (signal voltage) range. For example, the pixel array has a first region and a second region, wherein the average brightness of the first region within a specific signal voltage range is maintained at one The fixed value, while the average brightness of the second region within a specific signal voltage range is maintained at another fixed value, and thus the contrast is changed when the active matrix type liquid crystal display device is obliquely viewed at an offset angle.

The active matrix type liquid crystal display device described above, wherein the first region and the second region are horizontally adjacent to each other or vertically adjacent to each other.

In the active matrix type liquid crystal display device described above, the pixel array includes a plurality of first regions and second regions, and the first region and the second region are arranged in a checkerboard shape at an interval.

According to the present invention, an electronic device having the active matrix type liquid crystal display device described above can be provided for displaying data.

According to the present invention, there is provided a method of operating the active matrix type liquid crystal display device described above in a privacy mode, comprising: causing an active matrix type liquid crystal display device to enter a privacy mode enabled state; and applying different The signal voltage is applied to adjacent pixel elements of the pixel array such that adjacent pixel elements produce an average brightness. Wherein, the average brightness of the adjacent pixel elements is a gamma curve when the positive-acting active matrix type liquid crystal display device changes according to the change of the signal voltage to display the expected image; and the average brightness of the adjacent pixel elements is related to the signal voltage. The change is related to the offset-angle squint active matrix type liquid crystal display device, which is maintained at a fixed value within a specific signal voltage range to change the image contrast to an unrecognizable extent.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The first figure shows the relationship of brightness (or brightness) to color gradation (or gray level, signal voltage). Such a curve is often referred to as a gamma curve. Curve 1 is a general gamma curve line. In general, the brightness increases in an exponential relationship with respect to the color system. On the other hand, the curve 2 is a change in luminance corresponding to the gradation when the user sees the oblique angle of 60 degrees from the front side as in the second figure. Generally, each pixel system respectively applies a voltage corresponding to the color gradation shown on the horizontal axis of the first graph, and displays a picture according to the individual pixels, wherein the brightness is represented by the brightness of the curve 1 from the front side and the brightness of the curve 2 from the slope side. Said.

For example, when a certain voltage V is applied to one pixel corresponding to the gradation, the brightness seen from the front is expressed by a function I ₀ (V) of V. This is the gamma curve 1. Conversely, in the case where a certain voltage V is applied to one pixel corresponding to the gradation, the luminance seen from the oblique angle of 60 degrees from the front is expressed by a function I ₆₀ (V) of V. This is the gamma curve 2. In other words, since the brightness from the front is represented by curve 1, and the brightness from the oblique angle of 60 degrees from the front is represented by curve 2, the difference in brightness between a certain signal and a certain signal is in principle only used for curve 1. The difference between the change and the change of curve 2 is expressed. Therefore, the image viewed from the oblique surface and the image viewed from the front are almost the same image, but the displayed image is not clear.

Therefore, according to the present invention, the image contrast is changed by applying different signal voltages to adjacent pixels, so that the image viewed from the front is a generally expected image, and the image displayed on the oblique surface is unrecognizable, ensuring privacy. maintain. For example, when the signal voltages V ₁ and V ₂ are respectively applied to the adjacent pixels 1 and 2, the brightness from the front is the average of the pixels 1 and 2, that is, (I ₀ (V ₁ )+I ₀ (V ₂ ))/2, and the brightness seen from the oblique angle of 60 degrees from the front side is (1 ₆₀ (V ₁ ) + I ₆₀ (V ₂ ))/2. At this time, (I ₀ (V ₁ )+I ₀ (V ₂ ))/2 is known as the original γ curve, and the generally expected image can be seen from the front. In order to indicate that, for example, the curves 3 and 4 have a fixed luminance (I ₆₀ (V ₁ )+I ₆₀ (V ₂ ))/2 in a specific signal voltage range, V ₁ and V ₂ must be set in advance, In order to change the image contrast, the image seen from the oblique angle of 60 degrees from the front is difficult to recognize. In other words, the curves 3 and 4 are curves set to destroy the original image display function (i.e., the screen display for giving different signal voltages to each pixel to obtain different brightness), so that the brightness seen from the slope does not change with the change of the signal voltage. In this way, the brightness of each pixel changes from the front to the gamma curve with respect to the change of the signal voltage, showing the originally expected image, and the change in brightness from the oblique angle of 60 degrees from the front is tied to a specific signal voltage. Within the range, a fixed brightness is presented. When all the pixels have the same brightness, the image contrast deteriorates, making the original image illegible.

In addition, for example, (I ₆₀ (V ₁ )+I ₆₀ (V ₂ ))/2 obtained by pixels of a column or some fixed columns is a curve 3, and is obtained by interleaving one column or some columns of pixels (I ₆₀ (V ₁ )+I ₆₀ (V ₂ ))/2 is the curve 4, and the high-luminance region I and the high-luminance region I see when viewed from the oblique angle of 60 degrees from the front side as shown in the third diagram (A) can be obtained. Low-brightness area II The two brightnesses are vertically interlaced. In other words, if two kinds of gamma curves are used in different regions, the contrast of the image from the oblique surface can be made worse, and there is a more complicated shadow effect. In addition, the high-brightness area I and the low-brightness area II may be arranged such as horizontal interlace and checkerboard interleave (interval arrangement) as shown in the third (B) and third (C) drawings, thereby making the oblique view The image has a more complex shadow effect, making it more difficult to recognize.

In the pixel matrix included in the active matrix type liquid crystal display device of the present invention described above, the voltage supply is differentiated in units of pixels. In addition to this, the pixel matrix can also differentiate the voltage supply in units of sub-pixels obtained by pixel division. However, in the case of undivided pixels, in order to obtain two voltages, two pixels are used, and the resolution is halved. In order to solve this problem, one pixel (or sub-pixel) is divided into two as described above, and two voltage signals are given to maintain the original resolution.

The fourth figure is a block diagram of a pixel display mode of an active matrix type liquid crystal display device according to the present invention, which is described by taking different voltages simultaneously to adjacent sub-pixels. In the fourth figure, the liquid crystal display device has a pixel array to include a plurality of pixels 21. Each of the pixels 21 is divided into a plurality of primary colors R, G, and B provided in the longitudinal direction and the lateral direction of the matrix, and is divided into sub-pixels 22 and sub-pixels 23. The liquid crystal display device further includes a voltage source, and supplies a signal voltage to the pixel array for controlling the brightness of the pixel array to display an image. First, the pixel data 27 is stored in the memory 26, and the pixel data output from the memory 26 is converted into voltage data by the digital analog (D/A) converter 24 according to the comparison table 25. The comparison table 25 is coupled to the digital analog converter 24 and the memory 26, and records the voltage value of the corresponding pixel data in a digital form, which can respectively output different voltage values to the sub-pixels 22 and 23 to distinguish The brightness of the front view and squint in the privacy mode enabled state. The digital analog converter 24 is operative to convert the voltage value to an analog form prior to applying a voltage value to the sub-pixels 22, 23. At this time, the output signal voltages V ₁ and V ₂ set in the comparison table correspond to the γ curve 1 when the display device is viewed from the front, and the curve when the display device is viewed from the slant. The output signal voltages V ₁ and V ₂ are applied to the sub-pixel 22 and the sub-pixel 23, respectively.

Although the devices in the above embodiments are used to process sub-pixels, they can also be used to process adjacent pixels to obtain almost the same effect.

In addition, an optional system can be designed to switch between a privacy mode disable state (ie, only the original image is displayed) and a privacy mode enable state (ie, need to make the slave switch). The image viewed from the front is the original image, and the image viewed from the bevel is the case where the image is different from the original image). In general, an image with a wide field of view is displayed, and an image viewed from a slope is difficult to recognize only when a privacy mode such as a mixed place is necessary. In the fourth figure, the switch table 28 is used to convert the look-up table to output a signal voltage to the pixel array, wherein a general control can be selected. A table (such as the comparison table 25) and another privacy mode coupled to the memory 26 are shown in a comparison table (not shown). In this way, the display device according to the present invention can have a wider field of view when the privacy mode is not used, and can be implemented in a place where it is appropriate.

In addition, in order to make the image viewed from the slope in the privacy mode more difficult to recognize, the signal voltage range used can be narrowed. In order for the luminance in the gamma curve relative to the signal voltage to remain as fixed as curve 3 or 4, it is generally necessary to limit the overall signal voltage to a certain range. Therefore, if only the two gamma curves have a fixed brightness in a specific signal voltage range, the image viewed from the bevel can exhibit exactly the same brightness in one area, and the shadows appear in two areas that mix different brightnesses. Effect. The brightness of the two gamma curves is a fixed specific signal voltage range, which can be selected from 20% to 80% of the overall range of the signal voltage. Within this range, the brightness in each region can be exactly the same from the slope. .

A liquid crystal display device according to the present invention, the method of operating in a privacy mode, comprising: causing a liquid crystal display device to enter a privacy mode enabled state; and respectively applying different signal voltages to adjacent pixels of the pixel array to cause adjacent pixels to be generated An average brightness. Wherein, the average brightness of the adjacent pixels is a gamma curve when the liquid crystal display device is displayed in accordance with the change of the signal voltage to display the expected image; and the average brightness of the adjacent pixels is related to the offset of the signal voltage. When squinting the liquid crystal display device at an angle, it is maintained at a fixed value within a specific signal voltage range to change the image contrast to an unrecognizable extent.

The liquid crystal display device according to the present invention can be used for displaying data in a liquid crystal display portion of an electronic device such as a personal computer, a notebook computer, a personal digital assistant (PDA), a digital camera, a mobile phone, or a car navigation system. Especially for the application of portable electronic devices such as notebook computers, PDAs, and mobile phones.

The components included in the schema of this case are listed as follows:

1 ‧‧‧The curve of the color gradation and brightness when viewed from the front (γ curve)

2 ‧‧‧A curve of color gradation and brightness when viewed from a 60 degree tilt angle from the front

3 ‧‧‧Examples of the change of color gradation and brightness when two different voltages are applied to adjacent pixels

4 ‧‧‧Another example of the change of color gradation and brightness when two different voltages are applied to adjacent pixels

I ‧‧‧High brightness area

II ‧‧‧Low-light areas

21 ‧ ‧ pixels

22 ‧‧‧Subpixels

23 ‧‧‧Subpixels

24 ‧‧‧Digital Analogue (D/A) Converter

25 ‧‧‧ comparison table

26 ‧‧‧Memory

27 ‧‧‧Pixel data

28 ‧‧‧Switch

The first graph shows the relationship between the excellent order (signal voltage) and the brightness.

The second figure is a schematic view of the position of the user and the liquid crystal display screen viewed from a tilt angle of 60 degrees from the front.

The third figure (A) is a picture in which two kinds of luminances are longitudinally staggered when viewed from a tilt angle of 60 degrees from the front.

The third figure (B) is a picture in which two kinds of luminances are seen to be horizontally staggered when viewed from a tilt angle of 60 degrees from the front.

The third graph (C) is a screen in which two kinds of luminances are seen in a checkerboard pattern when viewed from a tilt angle of 60 degrees from the front.

The fourth figure is a block diagram of a pixel display mode of the active matrix type liquid crystal display device of the present invention.

1 ‧‧‧The curve of the color gradation and brightness when viewed from the front (γ curve)

2 ‧‧‧A curve of color gradation and brightness when viewed from a 60 degree tilt angle from the front

3 ‧‧‧Examples of the change of color gradation and brightness when two different voltages are applied to adjacent pixels

4 ‧‧‧Another example of the change of color gradation and brightness when two different voltages are applied to adjacent pixels

Claims (19)

An active matrix type liquid crystal display device includes: a pixel array including a plurality of pixel elements; and a voltage source for supplying a plurality of signal voltages to the pixel array for controlling brightness of the pixel array to display an image Wherein the signal voltages of different levels are applied to adjacent pixel elements respectively; wherein an average brightness of the adjacent pixel elements is related to the change of the signal voltages in view of the active matrix type liquid crystal display device Presenting a gamma curve to display a desired image; and wherein the average brightness of the adjacent pixel elements is slanted at an angle to the active matrix type liquid crystal display device according to the change of the signal voltages Maintaining a fixed value over a particular signal voltage range to change an image contrast to display an unrecognizable image; a storage device for storing pixel data to be input to the pixel array; and a look-up table, Communicating with the storage device, wherein a plurality of voltage values corresponding to the pixel data are recorded, which can output different electrical powers Such a pixel value to adjacent elements, to distinguish a privacy mode can be activated at a state when a front perspective view of the brightness. The active matrix type liquid crystal display device of claim 1, wherein the adjacent pixel elements are adjacent pixels or adjacent sub-pixels divided by a pixel. The active matrix type liquid crystal display device according to claim 1, further comprising a switch connected to the comparison table and controlled to switch the active matrix The liquid crystal display device selectively enters the privacy mode enabled state or a privacy mode disabled state. An active matrix type liquid crystal display device according to claim 3, wherein when the active matrix type liquid crystal display device selectively enters the privacy mode disabled state, another comparison table connected to the storage device is used. The output voltage is applied to the pixel array. According to the active matrix type liquid crystal display device of claim 1, wherein the voltage values are digitally recorded in the look-up table, and the active matrix type liquid crystal display device further includes a digital analog converter, and The look-up table is in communication for converting the voltage values to an analog form before applying the voltage values to the adjacent pixel elements. The active matrix type liquid crystal display device of claim 1, wherein the specific signal voltage range is 20% to 80% of a signal voltage range which is output to one of the gamma curves of the pixel array. The active matrix type liquid crystal display device of claim 1, wherein the pixel array has a first region and a second region, and the average brightness of the first region in the specific signal voltage range is maintained at The fixed value, and the average brightness of the second region within the particular signal voltage range is maintained at another fixed value. The active matrix type liquid crystal display device of claim 7, wherein the first region and the second region are horizontally adjacent to each other. The active matrix type liquid crystal display device of claim 7, wherein the first region and the second region are vertically adjacent to each other. The active matrix type liquid crystal display device of claim 7, wherein the pixel array comprises a plurality of the first region and the second region, the first region and the The second zones are arranged in a checkerboard shape at an interval. An electronic device having an active matrix type liquid crystal display device according to claim 1 of the patent application scope for displaying data. The electronic device according to claim 11 of the patent application may be selected from a personal computer, a notebook computer, a personal digital assistant (PDA), a digital camera, a mobile phone, or a navigation system. A method for operating an active matrix type liquid crystal display device in a privacy mode, comprising: causing the active matrix type liquid crystal display device to enter a privacy mode enable state; and respectively applying different signal voltages to a pixel array Adjacent pixel elements to generate an average brightness; wherein the average brightness of the adjacent pixel elements exhibits a gamma curve as a function of the signal voltages in relation to the active matrix type liquid crystal display device to display An expected image; and wherein the average brightness of the adjacent pixel elements is within a specific signal voltage range as the signal voltage changes in relation to the active matrix type liquid crystal display device at an offset angle Maintaining a fixed value to change an image contrast reveals an unrecognizable image. The method of claim 13, wherein the adjacent pixel elements are adjacent pixels or adjacent sub-pixels divided by a pixel. According to the method of claim 13, further comprising the step of selectively causing the active matrix type liquid crystal display device to selectively enter the privacy mode enabled state or a privacy mode disabled state. The method of claim 13, wherein the specific signal voltage range is 20% to 80% of a range of signal voltages outputted to one of the gamma curves of the pixel array. The method of claim 13, wherein the pixel array has a first region and a second region, and the average brightness of the first region in the specific signal voltage range is maintained at the fixed value, and the average brightness is maintained at the fixed value. The average brightness of the second zone over the particular signal voltage range is maintained at another fixed value. The method of claim 17, wherein the first zone and the second zone are horizontally or vertically adjacent to each other. The method of claim 17, wherein the pixel array comprises a plurality of the first region and the second region, and the first regions and the second regions are arranged in a checkerboard shape at an interval.