JPH1090115A - Method and apparatus for evaluation of liquid-crystal display device as well as liquid-crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To objectively evaluate the liquid-crystal display device by quantitatively determining the quality of the display thereof. SOLUTION: An evaluation method for a liquid-crystal display device measures the quality of a display displayed in a display region 26 in which a plurality of rows comprising a plurality of pixels arranged in a row are arranged in parallel. In the evaluation method, a luminance which is different from that of a specific region or a pattern by a luminance is displayed in a peripheral region adjacent to the specific region in the display region 26, and the luminance in an arbitrary position of the peripheral region is measured. Then, the luminance in the peripheral region or a luminance which is identical to that of the pattern by the luminance or a pattern by a luminance is displayed on nearly the whole face of the display region 26, the luminance in the same position as the arbitrary position is measured, and the quality of the display is evaluated on the basis of the measured luminance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a liquid crystal display device, an evaluation device thereof, and a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices include word processors, personal computers,
Widely used for portable information terminal equipment and other monitors. Currently, liquid crystal display devices for such applications are of an active matrix type in which a nematic liquid crystal is interposed between a plurality of pixel electrodes arranged in a matrix and active electrodes such as thin film transistors (TFTs) as switching elements. Liquid crystal display devices have become mainstream. Such a liquid crystal display device is used for its purpose of use.
Display color and brightness are important factors that determine the display quality.

However, these display colors and brightness are often very slightly different from each other, and it is necessary to determine whether the display color and brightness of the manufactured liquid crystal display device are desired or different. Is difficult.

Conventionally, the evaluation of the display quality such as the display color and brightness of the liquid crystal display device has been performed by visual inspection. However, such visual inspections are not quantitative, and there are individual differences among persons to be evaluated, and they vary delicately depending on the environment to be inspected. Therefore, it is difficult to obtain sufficiently objective evaluations. is there. In order to obtain a more accurate evaluation, it was necessary to perform a visual inspection with a large number of people and evaluate the evaluation of a certain number of people or more collectively.

[0005]

As described above, conventionally,
The evaluation of display quality, such as the display color and brightness of a liquid crystal display device, is performed by visual inspection.However, such visual inspection is not quantitative, and there are individual differences depending on the person to be evaluated. It is difficult to obtain an evaluation with sufficient objectivity because it changes subtly depending on the environment in which it is performed. In order to obtain a more accurate evaluation, it was necessary to perform a visual inspection with a large number of people and evaluate the evaluation of a certain number of people or more collectively.

However, such an evaluation method is poor in objectivity and low in reliability. In addition, there is a problem that it is practically impossible to apply the method to each of mass-produced liquid crystal display devices.

[0007] The present invention has been made in view of the above problems, and has as its object to quantify the display quality of a liquid crystal display device so that it can be objectively evaluated.

[0008]

In a method for evaluating a display quality in which a plurality of pixels arranged in one line are displayed in a display region in which a plurality of columns are arranged in parallel in a plurality of columns, a liquid crystal display device adjacent to a specific region of the display region is evaluated. A luminance or luminance pattern different from that of the specific region is displayed in the peripheral region, the luminance of an arbitrary position in the peripheral region is measured, and almost the same luminance or luminance as the luminance or luminance pattern of the peripheral region described above is measured over almost the entire display region. The pattern was displayed, and the luminance at the same position as the above-mentioned arbitrary position was measured, and the display quality was evaluated based on the measured luminance at these positions.

Further, the specific area is defined as 3 to 85 of the display area.
%.

Further, the specific area is set to black, and the peripheral area is set to a halftone brighter than black.

The specific area is set to white, and the peripheral area is set to a halftone darker than white.

Also, the luminance Y1 at an arbitrary position in the peripheral area measured by displaying a pattern of luminance or luminance different from that of the specific area in the peripheral area adjacent to the specific area, and the luminance or luminance of the peripheral area over substantially the entire display area. From the luminance Y2 at the same position as the above-mentioned arbitrary position measured by displaying the luminance pattern or the luminance pattern substantially the same as the luminance pattern, the C value represented by C = | Y1−Y2 | / Y2 × 100 (%) is obtained. After the calculation, the display quality was evaluated based on the C value.

In a liquid crystal display evaluation apparatus for evaluating the display quality displayed in a display area in which a plurality of pixels arranged in one row are arranged in a plurality of rows in a row, a plurality of pixels are specified in a peripheral area adjacent to the specified area in the display area. A driving device that displays a pattern of luminance or luminance different from that of the region, a measuring device that measures luminance at an arbitrary position in the peripheral region, and luminance of the peripheral region over almost the entire surface of the display region and luminance at an arbitrary position in the peripheral region. Alternatively, there is provided an arithmetic unit for performing arithmetic processing on the luminance at the same position as the arbitrary position measured by displaying the luminance pattern or the luminance pattern substantially the same as the luminance pattern.

In addition, the evaluation device displays the luminance Y1 at an arbitrary position in the peripheral area measured by displaying a luminance or a luminance pattern different from the specific area in the peripheral area adjacent to the specific area.
And the luminance Y2 at the same position as the above-mentioned arbitrary position measured by displaying the luminance or luminance pattern of the peripheral region almost over the entire display area and displaying the same luminance or luminance pattern, C = | Y1-Y2 | / Means for calculating a C value represented by Y2 × 100 (%).

Further, in a liquid crystal display device having a display area in which a plurality of pixels arranged in one row are arranged in a plurality of rows in parallel,
A luminance Y1 at an arbitrary position in the peripheral region measured by displaying a pattern of luminance or luminance different from that of the specific region in a peripheral region adjacent to the specific region of the display region, and a luminance or luminance of the peripheral region over substantially the entire display region. From the luminance Y2 at the same position as the above-described arbitrary position measured by displaying a pattern having substantially the same luminance or luminance as that of the pattern No. 2, a C value represented by C = | Y1-Y2 | / Y2 × 100 (%) is calculated as 2 0.5 or less.

[0016]

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

FIG. 1 shows an example of the configuration of an active trix type liquid crystal display device to which the present invention is applied. The liquid crystal display device 1 includes a pair of glass substrates 2 and 3 opposed to each other.
Among them, a plurality of pixel electrodes 5 having active elements such as TFTs as switching elements 4 are arranged in a line on the inner surface of one substrate 2, and this arrangement is arranged in a plurality of lines in an orthogonal direction. 4 and pixel electrode 5
An alignment film 6a is provided thereon. Also, the other substrate 3
A color filter 7, a counter electrode 8 on the color filter 7, and an alignment film 6 on the counter electrode 8.
b is provided. Liquid crystal 9 is interposed between the alignment films 6a and 6b of the pair of glass substrates 2 and 3.
Furthermore, a polarizing plate 10 is provided on the outer surface of each of the substrates 2 and 3.
a and 10b are stuck. In such a liquid crystal display device 1, a display region is formed by the plurality of pixel electrodes 5 and the counter electrode 8 which face each other via the liquid crystal 9.

FIG. 1B shows an example of a switching element. In FIG.
Is a signal line for supplying a display signal to each pixel electrode 5,
Reference numeral 13 denotes a gate line for supplying a gate signal for controlling the supply of the display signal.

FIG. 2 shows a configuration of an evaluation device for evaluating the display quality of the liquid crystal display device. The evaluation device includes a driving device 15 for controlling display of a display area of the liquid crystal display device 1.
And a measuring device 16 for measuring the luminance of the display of the liquid crystal display device 1 and an arithmetic device (not shown) for evaluating the display quality of the liquid crystal display device 1 based on the luminance measured by the measuring device 16. Become.

The measuring device 16 comprises a support 17 for supporting the liquid crystal display device 1, a camera 18 for measuring luminance, and a support 19 for supporting the camera 18 for measuring luminance. These supports 17 and 19 support the liquid crystal display 1 by arrows 20 and 20 so that the camera 18 can be directly opposed to the luminance measurement point of the liquid crystal display 1 supported by the support 17. Move up and down, left and right as indicated by 21,
And it is formed in a structure that can be turned as shown by the arrow 22. Further, the support base 19 is formed in a structure that can move the camera 18 in the vertical and horizontal directions indicated by arrows 23 and 24.

As will be described later, the arithmetic unit performs the display when the central portion of the display area of the liquid crystal display device 1 is black or white and the peripheral portion surrounding the central portion is gray (halftone). Brightness Y1 (average value) at any position in the periphery
And luminance Y2 (average value) at the same position as the above-mentioned arbitrary position when the above-mentioned central portion is displayed in the same gray as the peripheral portion when the display is made black or white on the entire surface of the display area.
From this, there is an arithmetic processing means for calculating a C value represented by C = | Y1-Y2 | / Y2 × 100 (%).

In this embodiment, the display quality of the following crosstalk is evaluated. The crosstalk is shown in FIG.
As shown in (a), the rectangular portion of the central portion 27 of the display area 26 of the liquid crystal display device is black or white, and the central portion 2
The luminance of the central portion 27 is lower than that of the peripheral portion 28, and the luminance of the central portion 27 is higher when the central portion 27 is white, so that the peripheral portion 28 surrounding the rectangular portion 7 becomes gray. in this case,
The rectangular portion of the central portion 27 is called a black window.
On the other hand, as shown in FIG. 3B, the rectangular portion of the central portion 27 is white, and the luminance of the central portion 27 is
A case where the image is displayed with a higher luminance than that is called a white window.

As an example, when a display called the above-mentioned black window is performed, the peripheral portion 28, which is a gray display having a higher luminance than the central portion 27, should originally have the same brightness and color at all points. However, actually, the points A1, A2, and A3 shown in FIG. 3A may look different in brightness and color. In this case, the points A1 and A
4 is called horizontal crosstalk, and the case where points A2 and A3 have different brightness and appear as shown in FIG. 4 (b) is called vertical crosstalk. Talk. On the other hand, the same phenomenon can be confirmed even when the white window is set.

When such crosstalk occurs, the display becomes uneven and the display becomes unsightly. In addition, there is a possibility that the display may be mistaken.

Although the cause of the occurrence of such crosstalk is not clear, it is considered that the coupling between the pixel electrode and the signal line or the amount of charge written into the pixel electrode differs between the window portion and its peripheral portion. .

The evaluation of the display quality will be described for the black window shown in FIG. The liquid crystal display device 1 is mounted on the support 17 shown in FIG.
As shown in the figure, the central portion 27 of the display region 26 is set as a specific region, the central portion 27 is black, and the adjacent peripheral portion 28 surrounding the central portion 27 has a gray halftone of higher luminance than that. The liquid crystal display device 1 is driven. In this case, the size of the black window in the central portion 27 is set to 3 to 85% of the display area 26 so that crosstalk is likely to occur.
Then, the liquid crystal display device 1 and the luminance measuring camera 18 supported by the support base 19 are appropriately moved in the directions of arrows 20 to 24, and the camera 18 is directly opposed to an arbitrary point on the peripheral portion 28, in the illustrated example, a point A1. The brightness y of the point A1
Measure 1. Next, as shown in FIG. 5 (b), the liquid crystal display device 1 is arranged such that the entire surface of the display area 26 has a gray raster pattern substantially the same as the peripheral portion when the display is performed with the central portion being black. To drive the point A1
The luminance y2 at the same point B1 is measured.

The measurement of the luminances y1 and y2 at the point A1 is repeated by changing the driving conditions of the liquid crystal display device 1, and the following equation is obtained from the average values Y1 and Y2 as follows: C = | Y1−Y2 | / Y2 × 100 (% ) Calculate the C value represented by This C value is a so-called crosstalk ratio indicating the degree of crosstalk. According to the experiments performed by the inventors, if C ≦ 2.5, visual observation can be performed without concern for crosstalk. Therefore, the display quality can be evaluated based on the C value.

If C ≦ 2.5, it can be determined that the liquid crystal display device has good display quality.

That is, in the conventional evaluation method, even if crosstalk is generated by setting the specific area of the display area to black as described above, since the visual inspection is performed, the evaluation largely depends on the subjectivity of the inspector. There was a large variation in the judgment. In addition, the driving conditions at the time of inspection are various, and an objective and quantitative evaluation cannot be performed. However, according to the above method, the display quality can be objectively and quantitatively evaluated. Further, only a liquid crystal display device of a certain quality can be provided by the objective and quantitative evaluation.

The same evaluation can be performed for a white window as shown in FIG.

Hereinafter, as a specific evaluation object, a black window having a size of 11.5 cm × 8.5 cm and a brightness of 0.31 cd / m ² was formed at the center of the display area for an SVGA-LCD having a diagonal dimension of 29 cm. Table 1 shows the results measured by the above method while changing the driving conditions of the liquid crystal display device.

[0032]

[Table 1] In Table 1, in the case of the driving conditions 3 and 4, the condition of C ≦ 2.5 is satisfied, and it can be seen that good display is obtained.

In the above embodiment, the case where the display quality is evaluated by the crosstalk generated in the peripheral portion when the central portion of the display area is black has been described.
The black portion is not particularly limited to the center of the display area.

Also, in the above embodiment, the case where the luminance measurement is performed in a display having no specific pattern has been described. For example, a specific luminance measuring pattern is displayed in a display area, and the luminance of the pattern is measured. Even when the measurement is performed, the display quality can be evaluated objectively and quantitatively.

[0035]

As described above, a luminance or a luminance pattern different from that of the specific area is displayed in the peripheral area adjacent to the specific area of the display area, and the luminance of an arbitrary position in the peripheral area is measured.
When the luminance or luminance pattern substantially the same as the luminance or luminance pattern of the peripheral region is displayed on almost the entire display area and the luminance at the same position as the arbitrary position is measured to evaluate the display quality, the display of the liquid crystal display device is evaluated. Quality can be evaluated objectively and quantitatively.

Further, a driving device for displaying a luminance or a luminance pattern different from the specific region in a peripheral region adjacent to the specific region of the display region, and a measuring device for measuring the luminance of an arbitrary point in the peripheral region are provided. And an arithmetic unit for arithmetically processing the luminance at the same position as the arbitrary position measured by displaying and measuring a luminance or luminance pattern substantially equal to the luminance or luminance pattern of the peripheral region over substantially the entire display area. The display quality of the liquid crystal display device can be objectively and quantitatively evaluated with a simple configuration.

Further, the liquid crystal display device is provided with a luminance Y1 at an arbitrary position in the peripheral area measured by displaying a luminance or a luminance pattern different from that of the specific area in a peripheral area adjacent to the specific area of the display area. From the luminance Y2 at the same position as the arbitrary position measured by displaying the luminance or luminance pattern substantially the same as the luminance or luminance pattern of the peripheral area on almost the entire surface, C = | Y1-Y2 | / Y2 × 100 ( %) Is set to 2.5 or less, it is possible to provide a liquid crystal display device having a good display quality and a constant quality.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a configuration of a liquid crystal display device according to an embodiment of the present invention, and FIG. 1B is a diagram illustrating a main configuration thereof.

FIG. 2 is a diagram showing a configuration of an evaluation device for evaluating the display quality of the liquid crystal display device.

FIGS. 3A and 3B are diagrams for explaining crosstalk when evaluating the display quality of the liquid crystal display device. FIGS.

FIG. 4A is a diagram for explaining horizontal crosstalk, and FIG. 4B is a diagram for explaining vertical crosstalk.

FIGS. 5A and 5B are diagrams for explaining a method of evaluating display quality based on the crosstalk, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 5 ... Pixel electrode 9 ... Liquid crystal 15 ... Driving device 16 ... Measuring device 18 ... Brightness measuring camera 26 ... Display area 27 ... Central part 28 ... Peripheral part

Claims (8)

[Claims] 1. A method for evaluating a display quality in a display area in which a plurality of pixels arranged in a row are displayed in a display area in which a plurality of rows are arranged in a plurality of rows, comprising: Display a pattern of brightness or brightness different from the specific area, measure the brightness at any position in the peripheral area, and apply the same brightness or brightness pattern as the brightness or brightness pattern of the peripheral area to almost the entire display area. And measuring the luminance at the same position as the arbitrary position, and evaluating the display quality based on the measured luminance at these positions. 2. The method according to claim 1, wherein the specific area is set to a size of 3 to 85% of the display area. 3. The method for evaluating a liquid crystal display device according to claim 1, wherein the specific area is set to black, and the peripheral area is set to a halftone brighter than black. 4. The method for evaluating a liquid crystal display device according to claim 1, wherein the specific area is set to white and the peripheral area is set to a halftone darker than white. 5. A luminance Y1 at an arbitrary position of the peripheral area measured by displaying a luminance or a luminance pattern different from that of the specific area in a peripheral area adjacent to the specific area, and the peripheral area is provided over substantially the entire display area. From the luminance Y2 at the same position as the above-mentioned arbitrary position measured by displaying the luminance or the luminance pattern substantially the same as the luminance or luminance pattern, C = | Y1-Y2 | / Y2 × 100 (%) 2. The method for evaluating a liquid crystal display device according to claim 1, wherein a C value is calculated, and the display quality is evaluated based on the C value. 6. An evaluation device for a liquid crystal display device for evaluating a display quality displayed in a display area in which a plurality of pixels arranged in one row are arranged in a plurality of rows in parallel, wherein a display area includes a peripheral area adjacent to a specific area. A driving device that displays a luminance or a luminance pattern different from the specific region, a measuring device that measures luminance at an arbitrary position in the peripheral region, and a luminance at an arbitrary position in the peripheral region and almost the entire surface of the display region. An arithmetic unit for arithmetically processing the luminance at the same position as the arbitrary position measured by displaying and measuring the luminance or the luminance pattern substantially equal to the luminance or the luminance pattern of the region. . 7. The evaluation device displays a luminance or a luminance pattern different from that of the specific area in a peripheral area adjacent to the specific area and measures the luminance Y1 at an arbitrary position in the peripheral area.
From the luminance Y2 at the same position as the above-mentioned arbitrary position measured by displaying the luminance or luminance pattern of the peripheral region substantially the same as the luminance or luminance pattern of the peripheral region on almost the entire surface of the display area, C = | Y1-Y2 | / Y2 7. A device for evaluating a liquid crystal display device according to claim 6, further comprising means for calculating a C value represented by × 100 (%). 8. A liquid crystal display device having a display area in which a plurality of pixels arranged in a row are arranged in a plurality of rows in parallel, wherein a brightness or brightness pattern different from the specific area is provided in a peripheral area adjacent to the specific area of the display area. And the luminance Y1 at an arbitrary position in the peripheral area measured and displayed, and the luminance or luminance pattern substantially the same as the luminance or luminance pattern of the peripheral area almost all over the display area. A liquid crystal display device wherein a C value represented by C = | Y1−Y2 | / Y2 × 100 (%) from the luminance Y2 at the same position as the position is 2.5 or less.