JP5498648B2 - Driving method of display device - Google Patents

Description

  The present invention relates to a display device driving method, and more particularly to a display device driving method using a time gray scale method.

  In recent years, active matrix display devices using digital video signals have been actively researched and developed. Such active matrix display devices include a light receiving display device such as a liquid crystal display (LCD) and a self light emitting display device such as a plasma display. As a light-emitting element used in a self-luminous display device, an organic light-emitting diode (OLED) has attracted attention. OLED is also called an organic EL element, an electroluminescence (EL) element, or the like (a display using an EL element is called an EL display). A self-luminous display device using an OLED has advantages such as higher pixel visibility than a liquid crystal display, no need for a backlight, and high response speed. The luminance of the light emitting element is controlled by the value of current flowing therethrough.

  In such an active matrix display device, it is known to use a time gray scale method as a method of performing gray scale display using a digital video signal.

The time gray scale method is a method of expressing a gray scale by controlling the length of a light emitting period or the number of times of light emission. In other words, one frame period is divided into a plurality of subframe periods, and each subframe is weighted such as the number of times of light emission and the time of light emission, and the total amount of weighting (the total number of times of light emission and the sum of the time of light emission) The gradation is expressed by making a difference. As an example, one frame is divided into five subframes SF1 to SF5 in FIG. 34, and weighting is performed so that the ratio of the lighting periods of these subframes is 2 ⁰ : 2 ¹ : 2 ² : 2 ³ : 2 ⁴ Show the case. Also, FIG. 35 shows the relationship between the selection pattern of lighting / non-lighting of these subframes and the number of gradations. As can be seen from these figures, by controlling lighting / non-lighting of the subframes SF1 to SF5, 32 gradations of 0 to 31 can be displayed (the gradation number 1 represents the minimum unit of gradation change). . Since 1 bit is required to instruct lighting / non-lighting of each subframe, a 5-bit digital signal is required to control the five subframes SF1 to SF5. In general, an M-bit digital video signal is used to control M subframes having a power of power of 2 to display 2 ^M gradations (that is, the number of gradations is 0 to 2 ^M −1). It can be carried out. In this specification, a time gray scale method for performing gray scale display using a plurality of subframes with different weights is referred to as a binary code time gray scale method. Also, a bit of a digital signal that controls a large weight subframe (for example, SF5) is referred to as an upper bit, and a bit of a digital signal that controls a small weight subframe (for example, SF1) is referred to as a lower bit. Note that the weights of the subframes do not necessarily have to be powers of 2, and all the subframes may not necessarily have different weights. The weight (lighting period, number of blinks) of a certain subframe may be equal to or less than a value obtained by adding 1 to the sum of the weights of subframes with smaller weights (that is, lower-order). Thereby, all gradations can be expressed continuously. For example, if the ratio of the lengths of the lighting periods of the subframes is 1: 1: 2: 3, all gradations from 0 to 7 can be expressed continuously.

  In such a display device using the binary code time gradation method, when displaying a moving image, a false contour (or pseudo contour) is perceived in a portion where gradation is smoothly changed without originally generating a boundary. May be. It is known that such a pseudo contour is likely to occur when pixels having greatly different lighting patterns are adjacent such that one of adjacent pixels is gradation 15 and the other is gradation 16. It has been proposed (see Patent Documents 1 to 8).

For example, in Patent Document 2, seven subframes (upper subframes) having substantially equal weights are controlled by the upper 7 bits of, for example, a 12-bit digital signal representing gradation, and the remaining five lower bits are converted into a binary system. It is disclosed to control a plurality of sub-frames according to the weighting. In this device, the seven upper subframes are continuously arranged in one frame period, and the upper subframes are sequentially and cumulatively lit as the gradation increases. That is, the upper subframe that is lit at a small gradation is also lit at a larger gradation. Such a gradation method is called a superposition time gradation method.
Japanese Patent No. 2903984 Japanese Patent No. 3075335 Japanese Patent No. 2639311 Japanese Patent No. 3322809 JP-A-10-307561 Japanese Patent No. 3585369 Japanese Patent No. 3489884 JP 2001-324958 A

  As described above, various methods for reducing pseudo contours have been proposed, but the effect of pseudo contour reduction is not yet sufficient.

  For example, FIG. 36 shows subframe lighting patterns for each number of gradations when the invention described in Patent Document 2 is used to represent 32 gradations. In this figure, the lower two subframes SF1 and SF2 have a power of power of 2 (1: 2) and are used in the binary code time gray scale method (in this specification, such subframes are represented as binary codes). Subframes SF3 to SF9 have the same weight (4) and are used for the overlapping time gray scale method. By combining the overlay gradation method and the binary code gradation method in this way, the pseudo contour can be reduced to some extent.

  However, in the driving method of the conventional display device described in FIG. 36, seven subframes are used for the overlay time gray scale method, two subframes are used for the binary code time gray scale method, and a total of nine subframes are used. Compared with the binary code time gray scale method (FIG. 35) that requires only five subframes to represent the same gray scale, the number of subframes is greatly increased. Therefore, the number of bits of the digital signal for controlling it increases, and there are problems such as an increase in device scale and an increase in power consumption due to an increase in frequency.

  Further, in the conventional display device driving method shown in FIG. 36, the lighting sequence of the sub-frames in one frame is SF1, SF2,. . . , SF9 in this order. In this case, for example, both of the subframes SF1 and SF2 used in the binary code time gray scale method are turned on at the gradation number 11, whereas both of the subframes SF1 and SF2 are not lighted at the gradation number 12. And the subframe SF5 used for the overlapping time gray scale method that is temporally separated from the subframes SF1 and SF2 is lit. As a result, the lighting patterns of the gradation number 11 and the gradation number 12 are greatly different, and a pseudo contour is easily generated.

  In view of such problems, it is a main object of the present invention to provide a display device driving method capable of reducing pseudo contours while suppressing an increase in the number of subframes as much as possible.

  Another object of the present invention is to provide a display device driving method capable of reducing the generation of pseudo contours in a display device having a plurality of subframe groups driven by different gradation methods. .

  In order to solve the above problem, according to one aspect of the present invention, there is provided a driving method of a display device that expresses gradation by dividing one frame into a plurality of subframes, and each of the plurality of subframes is moderate. A plurality of middle subframes used in the superposition time gray scale method, at least one upper subframe used in the binary code time gray scale method having a higher weight than the middle subframe, At least one lower subframe used in a binary code time gray scale method and having a smaller weight than the lower subframe, and for each frame, a middle subframe, an upper subframe, and There is provided a method for driving a display device, characterized in that lighting or non-lighting of each lower subframe is selected. Note that “medium weighting” means neither a subframe having the minimum weight nor a subframe having the maximum weight. Further, the plurality of middle-order subframes do not necessarily have the same weight.

  Preferably, the lower subframe includes a weighted 1 subframe and a weighted 2 subframe. Alternatively, the lower subframe may consist of a weighted 1 subframe.

  Preferably, the plurality of middle subframes have the same weight, at least one of the upper subframes is divided into a plurality of divided subframes, and at least one of the plurality of divided subframes is a middle subframe. Q times the frame (Q is an integer not less than 1 and not more than the total number of middle subframes), and Q middle subframes and at least one of the divided subframes can be substituted for each other. Can be. When Q is 1, any one of the middle subframes and at least one of the divided subframes can be replaced. In the present application, “same weight” includes a case where there is a slight difference due to an error or the like.

  When the upper subframe has at least two subframes, at least one of the at least two upper subframes is divided into a plurality of divided subframes, and at least one of the plurality of divided subframes is another upper subframe. It is preferable to have the same weight as at least one of the frames so that at least one of the divided subframes and at least one of the other upper subframes can be substituted for each other.

  According to another aspect of the present invention, there is provided a driving method of a display device that expresses gradation by dividing one frame into a plurality of subframes, and the plurality of subframes have the same weighting and overlap time. A first subframe group including a plurality of subframes driven by a gray scale method; and a second subframe group including a plurality of subframes having a smaller weight than the subframes of the first subframe group. The second subframe group is adjacently arranged in one frame to form a subframe region, and the subframe of the second subframe group is fully lit from all lit by increasing the number of gradations. Whenever the subframe belongs to the first subframe group, the subframe that is temporally adjacent to the subframe region is included. The driving method of a display device, characterized in that frame has to grow solid from OFF are provided.

  Alternatively, a driving method of a display device that expresses gradation by dividing a frame into a plurality of subframes, and the plurality of subframes have a plurality of weights that have the same weighting and are driven by an overlapped time gradation method. A first subframe group including subframes, and a second subframe group including a plurality of subframes having a smaller weight than the subframes of the first subframe group. Whenever the subframe of the second subframe group changes from full lighting to full non-lighting, the highest weighting among the subframes belonging to the second subframe group among the subframes belonging to the first subframe group is given. The sub-frame that is temporally adjacent to the sub-frame that has it is changed from non-lighting to lighting. Driving method is provided in that the display device.

  According to another aspect of the present invention, there is provided a driving method of a display device that expresses gradation by dividing one frame into a plurality of subframes, and includes one or a plurality of subordinate subframes including a subframe having a weight of 1 A frame and one or a plurality of upper subframes having a higher weight than the lower subframe, and representing the number of gradations using selective lighting of the lower subframe and the upper subframe and image processing A method for driving a display device.

  Preferably, the image processing can be a dither diffusion method or an error diffusion method.

  Also, the lower subframe preferably has a subframe having a weight of 1 and a subframe having a weight of 2.

  Preferably, the display device having the driving method of the present invention is a light emitting device such as an organic EL display, an inorganic EL display, a plasma display, a field emission display (FED), a surface electric field display (SED), or a digital micro display. A reflective display device such as a mirror device (DMD), a grating light valve (GLV), or a reflective liquid crystal display, or a liquid crystal display device such as a ferroelectric liquid crystal display or an antiferroelectric liquid crystal display may be used.

  According to one aspect of the present invention, pseudo contour can be reduced by a plurality of middle subframes having a medium weighting and used in the superposition time gray scale method. Furthermore, an increase in the total number of subframes can be suppressed by at least one higher-order subframe that has a greater weight than the middle subframe and is used in the binary code time gray scale method. Further, fine gradation can be efficiently represented by at least one lower subframe having a smaller weight than the middle subframe and used in the binary code time gradation method.

  According to another aspect of the present invention, a first subframe group including a plurality of subframes having the same weighting and driven in a superposition time gray scale method, and smaller than the subframes of the first subframe group And a second subframe group including a plurality of subframes having weights. When the second subframe group is arranged adjacent to each other in one frame to form a subframe region, the subframe of the second subframe group is changed from all lighting to all non-lighting due to an increase in the number of gradations. Whenever it changes to lighting, the subframe lighting pattern is changed from non-lighting to lighting by changing the subframe temporally adjacent to the subframe region among the subframes belonging to the first subframe group. Since it can be made as small as possible, the pseudo contour can be reduced.

  According to still another aspect of the present invention, in a display device including a lower subframe including a subframe having a weight of 1 and one or more upper subframes having a weight greater than the lower subframe, the lower subframe includes: Since there are no subframes (middle subframes) having weights between the upper subframes, the number of gradations that cannot be expressed depending on the combination of lighting / non-lighting of the subframes is represented by the lower subframe and the upper subframe. By representing using selective lighting and image processing, it is possible to avoid a pseudo contour that may occur when a middle subframe is used. In addition, when displaying gradation using image processing, the lower subframes are also selectively turned on, so that minute differences between gradations can be expressed without using complicated image processing. It is possible to eliminate the need for an expensive IC or the like for performing proper image processing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
FIG. 1 is a diagram illustrating a lighting pattern of subframes according to a preferred embodiment of the present invention. This embodiment has three middle subframes that are driven in a superimposed time gray scale scheme with the same medium weight (4) to represent 32 (2 ⁵ ) gray scale numbers from 0 to 31. SF1 to SF3, the uppermost subframe SF4 having a large weight (16), and two lower subframes SF5 and SF6 having a small weight (1, 2) and driven in a binary code time gray scale method. doing. Also in this embodiment, similarly to the conventional example, various gradation numbers can be expressed by selectively lighting the subframes SF1 to SF6. In addition, the lighting order of the subframes in one frame may be changed for each frame, in the order of SF1 to SF6, in order from the smallest weight to the largest, vice versa, or randomly. Can take.

  According to such a configuration, the pseudo contour can be reduced by driving the middle subframes SF1 to SF3 having a medium weighting by the overlapping time gray scale method. In addition, since there is a subframe SF4 having a larger weight than the subframes SF1 to SF3 driven by the overlapping time gray scale method, the total number of subframes can be six. Therefore, the number of subframes of the prior art shown in FIG. Further, fine gradation can be efficiently expressed by the lower subframes SF5 and SF6 driven by the binary code time gradation method. As described above, according to the present invention, it is possible to effectively reduce the generation of the pseudo contour by introducing the subframe driven by the superposition time gray scale method while suppressing the increase in the total number of subframes. it can.

  FIG. 2 shows a modification of the embodiment of FIG. In the embodiment of FIG. 2, a subframe SF7 with a weight of 32 is added, and there are a total of seven subframes, which can represent 64 gray levels with 0 to 63 gray levels. Different. That is, in the embodiment of FIG. 2, the upper subframes SF4 and SF7 are driven in a binary code time gray scale method. In the embodiment of FIG. 1, only the uppermost subframe SF6 has a higher-order subframe having a higher weight than the subframes SF1 to SF3 driven by the superposition time gray scale method. The driving of only one subframe is also included in the binary code time gray scale method.

  The embodiment of FIG. 2 also has three subframes SF1 to SF3 having a medium weighting (4), so that the pseudo contour is reduced. In addition, since there are upper subframes SF6 and SF7 driven by the binary code time gray scale method, the total number of subframes is 7, and an increase in the number of subframes is suppressed. Further, fine gradation can be efficiently expressed by the lower subframes SF5 and SF6 driven by the binary code time gradation method. As described above, the present invention can be applied to display devices having various gradation numbers (or bit numbers), and can reduce the occurrence of pseudo contours while suppressing an increase in the number of subframes.

  FIG. 3 is a diagram illustrating a lighting pattern of subframes based on a modification of another embodiment of FIG. In the embodiment of FIG. 3, the highest-order subframe SF4 in FIG. 1 is divided into two subframes (referred to as divided subframes) SF4a and SF4b each having a weight of 8 as shown in FIG. Different. The weight (8) of each of the subframes SF4a and SF4b is equal to twice the weight (4) of the middle subframes SF1 to SF3 used in the superposition time gray scale method. Thereby, among the subframes SF1, SF2, SF3, and SF6 that are lit at the gradation number 14, different subframe lighting patterns (14 ′) are additionally set by replacing the subframes SF1 and SF2 with the subframe SF4a. . Similarly, by replacing any two of the three middle sub-frames SF1 to SF3 with sub-frames SF4a or SF4b for the number of gradation levels of 15, three different sub-frame lighting patterns (15 ′, 15 ″) 15a), the lighting pattern with the gradation number 15 does not overlap the lighting pattern with the lighting pattern with the gradation number 16 at all, whereas these three sub-frame lighting patterns have the subframe SF4a or SF4b overlaps, and thus is more similar to the lighting pattern of gradation number 16. In the embodiment of FIG. Frame SF4b) is placed in any two of the middle subframes SF1 to SF3 (subframes SF2 and SF3 in the example of FIG. 3). In other words, one different sub-frame lighting pattern (16 ′) is added to the number of gradations 16. This sub-frame lighting pattern (16 ′) and a sub-frame lighting pattern of 15 gradations are added. In comparison, the sub-frames SF2 and SF3 are lit in common, so that the 16 ′ lighting pattern is more similar to the 15 lighting pattern than the 16 lighting pattern. It is possible to prepare a plurality of subframe lighting patterns and change which one is used for each row, for each column, for each pixel, for each frame, etc. Thereby, for example, a certain pixel A has a gradation number of 15 (SF1 to SF1). SF3, SF5, and SF6 are turned on), and when the gradation number 16 is expressed in the pixel B adjacent to the pixel A, the lighting pattern of any one of 15 ′, 15 ″, and 15a By, it is possible to reduce the pseudo contour.

  It should be noted that the subframe lighting patterns with gradations of 14, 15, and 16 can be other than those shown in the drawing, and a plurality of subframe lighting patterns can be provided with gradations other than the gradations of 14, 15, and 16. It is possible to set. In the embodiment of FIG. 3, the subframe SF4 having a weight of 16 is divided into two subframes SF4a and SF4b each having a weight of 8. However, the present invention is not necessarily limited to this. For example, it is possible to divide into weight 12 and weight 4 subframes. In this case, the weight 12 subframe can be replaced with three subframes SF1 to SF3, and the weight 4 subframe is subframe. It can be replaced with any one of the frames SF1 to SF3. In general, a plurality of middle subframes having the same weight used in the superposition time gray scale method and at least one upper subframe used in the binary code time gray scale method having a larger weight than the middle subframe. And subdividing at least one of the upper subframes into a plurality of divided subframes, and at least one of the plurality of divided subframes is Q times the middle subframe (Q is 1 or more and less than the total number of middle subframes) The intermediate number of Q sub-frames and at least one of the divided sub-frames can be substituted for each other, and a plurality of sub-frames can be used for a predetermined number of gradations using the weights. A lighting pattern can be set.

  FIG. 4 is a diagram showing a lighting pattern of subframes based on a modification of the further embodiment of FIG. In the embodiment of FIG. 4, the uppermost subframe SF4 in FIG. 1 is divided into three subframes SF4a and SF4b each having a weight of 4, and one subframe 4c having a weight of 8. Different from FIG. Thus, the number of divisions of the upper subframe is not limited to two and is arbitrary. Each of the weighted 4 subframes SF4a and SF4b can be substituted for one of the weighted 4 subframes SF1 to SF3 used in the overlapping time gray scale method. Also, the subframe 4c having a weight of 8 can be substituted for two of the subframes SF1 to SF3 having a weight of 4. Accordingly, in the embodiment of FIG. 4, among the subframes SF1, SF2, SF3, and SF6 that are lit at the gradation number 14, a different subframe lighting pattern (14 ′) is added by replacing the subframe SF1 with the subframe SF4a. Is set. Similarly, five different subframe lighting patterns (15 ′, 15 ″, 15a, 15b, and 15c) are added for the gradation number 15, and one different subframe lighting pattern for the gradation number 16. In this case, the different subframe lighting patterns that can be added are not limited to those shown in the figure, and it is easy to understand that other subframe lighting patterns can be set. 4 also represents the number of gradations for which a plurality of subframe lighting patterns are set in a certain pixel, as in the embodiment of FIG. The pseudo contour can be reduced by selectively using one of the sub-frame lighting patterns.

FIG. 5 is a diagram showing still another embodiment of a subframe lighting pattern according to the present invention. In this embodiment, three intermediate subframes having the same medium weight (2) and driven in an overlapped time gray scale method to represent 32 (2 ⁵ ) gray scales with 0 to 31 gray scale levels. SF1 to SF3, upper subframes SF4 and SF5 having different weights (16, 32) and driven by the binary code time gray scale method, and driving by the binary code time gray scale method having a small weight (1). And one lower subframe SF6. The embodiment of FIG. 5 also has three sub-frames SF1 to SF3 having a medium weight (2), so that the pseudo contour is reduced. In addition, since there are upper subframes SF4 and SF5 driven by the binary code time gray scale method, the total number of subframes is 6, which suppresses the increase in the number of subframes. As described above, the present invention can also be applied to a case where the lower subframe driven by the binary code time gray scale method includes only one lowermost subframe (SF6), and can reduce the pseudo contour. it can.

  FIG. 6 is a diagram showing a modification of the embodiment of FIG. 6 is different from FIG. 5 in that the uppermost subframe SF5 in FIG. 5 is divided into two subframes SF5a and SF5b each having a weight of 8. Each of the subframes SF5a and SF5b having a weight of 8 can be substituted for the upper subframe SF4 having the same weight of 8. Accordingly, in the embodiment of FIG. 6, among the subframes SF1, SF2, SF3, SF4, and SF6 that are lit at the gradation number 15, different subframe lighting patterns (15 ′) are obtained by replacing the subframe SF4 with the subframe SF5a. Is additionally set. Thereby, when displaying the gradation number 15 with a certain pixel, the lighting pattern (15) for turning on the subframes SF1 to SF4 or the subframes SF1 to SF3 and SF5a is turned on according to the number of gradations of adjacent pixels. The pseudo contour can be reduced by selectively using the lighting pattern (15 ′). Also in this case, the number of gradations in which a plurality of subframe lighting patterns can be set is not limited to 15. For example, for any one having 8 to 14 gradations, subframe SF5a or SF5b is used instead of subframe SF4. By turning on, another subframe lighting pattern can be added.

  FIG. 7 is a diagram illustrating a subframe lighting pattern according to another embodiment of the present invention. This embodiment has nine subframes SF1 to SF9, and these nine subframes are divided into two subframe groups. That is, the subframes SF3 to SF9 have the same weight (4) and form the first subframe group used for the superposition time gray scale method, and the subframes SF1 and SF2 are smaller than the superposition subframes SF3 to SF9. And a second subframe group used for the binary code time gray scale method. As shown in the figure, 32 gradations (0 to 31) can be displayed by selecting lighting / non-lighting of these subframes SF1 to SF9. In the embodiment of FIG. 7, the lighting order of the subframes SF1 to SF9 in one frame is assumed to be in numerical order (that is, SF1, SF2,..., SF9). That is, in one frame, the left side (temporal front side) is the binary code subframe region (or the second subframe group) and the right side (temporal rear side) overlaps with subframes SF2 and SF3 as a boundary. Subframe regions having different driving methods such as subframe regions (or first subframe groups) are in contact with each other. In the embodiment of FIG. 7, when the subframes SF1 and SF2 used in the binary code time gray scale method change from full lighting to full non-lighting due to the increase in the gray scale number (ie, the gray scale number 3 → 4, 7 → 8). Among the subframes used in the superposition time gray scale method, the subframe SF3 temporally adjacent to the binary code subframe region is changed from non-lighting to lighting. Therefore, in the number of gradations in which one or both of the subframes SF1 and SF2 used in the binary code time gradation method, such as the number of gradations 5 to 7, 9 to 11, and 13 to 15, are turned on, the subframe SF3 is used. Instead of the other superposed subframes are lit.

  Thus, whenever the lower subframes SF1 and SF2 driven in the binary code time grayscale method change from full lighting to full non-lighting due to the increase in the number of gray scales, the upper superposed subframe (or the first subframe) By making the subframe SF3 temporally adjacent to the binary code subframe area among the subframes belonging to the frame group light up, the change in the subframe lighting pattern is minimized and the pseudo contour is reduced. be able to.

  In the embodiment of FIG. 7, the subframes SF1 and SF2 driven by the binary code time gray scale method and the subframes SF3 to SF9 driven by the superposition time gray scale method are adjacent to each other. It is not limited to this. For example, as shown in FIG. 8, instead of the lower subframes SF1 and SF2 driven by the binary code time gray scale method, three subframes SF1 each having a weight of 1 and driven by the overlapping time gray scale method are used. , SF2a, and SF2b. That is, in the embodiment of FIG. 8, two overlapping subframe regions (or subframe groups) having subframes with different weights are adjacent to each other. Also in this case, when the three superimposition subframes SF1 to SF3 having a weight of 1 included in the lower superimposition subframe area change from all lighting to all non-lighting due to an increase in the number of gradations, the upper superposition subframe area The embodiment of FIG. 7 is configured such that, among the seven overlapping subframes SF3 to SF9 having a weight of 4 included in the subframe SF3, the subframe SF3 adjacent to the lower overlapping subframe region changes from non-lighting to lighting. The same effect as described can be obtained. Of the different subframe regions that are in contact with each other as described above, the lower subframe region may be either the binary code time gray scale method or the overlapping time gray scale method.

  FIG. 9 is a diagram illustrating a sub-frame lighting pattern based on another embodiment of FIG. This embodiment has ten subframes SF1 to SF10, and the lower three subframes SF1 to SF3 have weights of powers of 2 (1: 2: 4). The subframes SF4 to SF10 have the same weighting (8) larger than the subframes SF1 to SF3, and are used in the superposition time gray scale method, and 64 gray scales (selection of lighting / non-lighting of these subframes) 0 to 63) can be displayed. Also in this embodiment, the lighting order of the subframes SF1 to SF10 in one frame is the numerical order (ie, SF1, SF2,..., SF10), and the lower subframes SF1 to SF3 are binary code subframe regions. The upper subframes SF4 to SF10 form a superposed subframe region, and both subframe regions are in contact between the subframes SF3 and SF4. In the embodiment of FIG. 9, when the subframes SF1 to SF3 used in the binary code time gray scale method change from full lighting to full non-lighting due to an increase in the gray scale number (ie, the gray scale number 7 → 8, 15 → 16). Etc.), SF4, which is a subframe adjacent to the binary code subframe region among subframes used in the superposition time gray scale method, is changed from non-lighting to lighting. Therefore, in the number of gradations in which any and all of the subframes SF1 to SF3 used in the binary code time gradation method, such as the gradation numbers 9 to 15 and 17 to 23, are turned on, other than the subframe SF4. The superimposed subframe is illuminated. When subframes SF1 to SF3 change from full lighting to full non-lighting due to an increase in the number of gradations, SF4, which is a subframe adjacent to the lower binary code subframe area, is turned on among the superposed subframes. The pseudo contour can be reduced by minimizing the change in the subframe lighting pattern. Thus, the present invention can be applied to any gradation.

  FIG. 10 is a diagram showing a subframe lighting pattern based on a modification of the embodiment of FIG. In the embodiment of FIG. 10, the overlapping subframe SF4 adjacent to the binary code subframe region is lit continuously for two gradations (for example, gradation numbers 8 and 9, gradation numbers 16 and 17, etc.). Different from the embodiment of FIG. As described above, when the subframes SF1 to SF3 included in the lower subframe region change from full lighting to full nonlighting due to the increase in the number of gradations, the subframes SF1 to SF3 (binary) among the upper superposed subframes. In order to enable SF4, which is a subframe adjacent to the code subframe area), to change from blinking to lighting, subframe SF4 is not lit at all gradation levels of subframes SF1 to SF3. It is only necessary that SF4 is not turned off at all other gradation levels.

  FIG. 11 is a diagram showing a subframe lighting pattern according to still another aspect of the present invention. The embodiment of FIG. 11 has six subframes SF1 to SF6, and the lower two subframes SF1 and SF2 have weights of powers of 2 (1: 2) in the binary code time gray scale method. The subframes SF3 to SF6 have the same weighting (16) larger than the lower two subframes SF1 and SF2, and are used in the overlapping time gray scale method. In the embodiment of FIG. 11, since there are no intermediate weighted subframes (4 and 8), the gradation numbers 0 to 3, 16 to 19, 32 to 35, and 48 to 51 are subframes SF1 to SF6. Although it can be expressed by a combination of lighting / non-lighting, other gradation numbers, that is, the gradation numbers 4-15, 20-31, 36-37, and 52-63 are the lighting / non-display of the subframes SF1 to SF6. Cannot be represented by a combination of lights. In this embodiment, the number of gradations that cannot be expressed by the combination of lighting / non-lighting of these subframes SF1 to SF6 is expressed using image processing such as a dither diffusion method or an error diffusion method. That is, the gradation number 4 to 15 is displayed by lighting SF3 (weighting 16) and using image processing, and the gradation number 20 to 31 is lighting SF3 and SF4 (total weighting 32) and performing image processing. The gradation numbers 36 to 37 are displayed by turning on SF3 to SF5 (total weight 48) and using image processing, and the gradation numbers 52 to 63 are SF3 to SF6 (total weight 64). ) Is turned on and displayed by using image processing. Here, according to the present invention, since the embodiment of FIG. 11 has lower subframes SF1 and SF2 having small weights (1, 2), these lower subframes are displayed when displaying gradation using image processing. By selectively lighting SF1 and SF2, it is possible to express a minute difference between gradations without using complicated image processing, thereby enabling an expensive IC or the like for performing complex image processing. It can be unnecessary. Further, it is possible to avoid a pseudo contour that may occur when the binary code time gray scale method is performed by additionally using subframes having medium weights such as weights 4 and 8.

  FIG. 12 is a diagram showing a subframe lighting pattern based on a modification of the embodiment of FIG. The embodiment of FIG. 12 is the same as the embodiment of FIG. 11 in that it has two lower subframes SF1 and SF2 that have a power of power of 2 (1: 2) and are used in the binary code time gray scale method. 11 is different from the embodiment of FIG. 11 in that instead of four subframes each having a weight 16 as upper subframes used in the superimposing gradation method, eight subframes SF3 to SF10 each having a weight 8 are provided. . Since this embodiment also does not have a subframe with an intermediate weight (4), the number of gradations is 4 to 7, 12 to 15, 20 to 23, 28 to 31, 36 to 39, 44 to 47, 52 to 52. 55 and 60 to 63 cannot be expressed by a combination of lighting / non-lighting of the subframes SF1 to SF10, and are expressed using image processing such as a dither diffusion method or an error diffusion method. Since the embodiment of FIG. 12 also has lower subframes SF1 and SF2 having small weights (1, 2), not only the upper subframes but also these lower subframes SF1 and SF2 are displayed for gradation display using image processing. By selectively lighting up, it is possible to express minute differences between gradations without using complex image processing, thereby eliminating the need for expensive ICs or the like for performing complex image processing. be able to. In addition, it is possible to avoid a pseudo contour that may occur when the binary code time gray scale method is performed by additionally using a subframe having an intermediate weight of weight 4.

  FIG. 13 is a diagram showing a subframe lighting pattern based on a modification of the embodiment of FIG. The embodiment of FIG. 13 is the same as the embodiment of FIG. 12 in that it has eight subframes SF2 to SF9 each having a weighting of 8 driven in a superposition gray scale method, but a lower subframe having a small weighting. 12 is different from the embodiment of FIG. 12 in that only the subframe SF1 with weight 1 is included. In the embodiment of FIG. 13, the number of gradations 2 to 7, 10 to 15, 18 to 23, 26 to 31, 34 to 39, 42 to 47, 50 to 55, and 58 to 63 are turned on / off of the subframes SF1 to SF9. Since it cannot be expressed by a combination of non-lighting, it is expressed using image processing such as dither diffusion method or error diffusion method. Since the embodiment of FIG. 13 also has the lower subframe SF1 having a small weight (1), not only the upper subframe but also the lower subframe SF1 is selectively used when displaying gradations displayed using image processing. By turning on the light, it is possible to express a minute difference between gradations without using complicated image processing. In addition, it is possible to avoid a pseudo contour that may occur when the binary code time gray scale method is performed by additionally using a subframe having an intermediate weight of weight 4. As described above, the number of sub-frames having a small weight for expressing a minute difference between gradations is arbitrary, but it is preferable to have at least a sub-frame having a weight 1 (that is, a minimum weight).

  So far, the case where the lighting period increases linearly in proportion to the number of gradations has been described. Then, next, an embodiment in which the present invention is applied when gamma correction is performed will be described. The gamma correction refers to a non-linear lighting period that increases as the number of gradations increases. Even if the luminance increases linearly in proportion, the human eye does not feel that it is brighter in proportion. The higher the brightness, the less the difference in brightness is felt. Therefore, in order for the human eye to feel the difference in brightness, it is preferable to take a longer lighting period as the number of gradations increases, that is, to perform gamma correction.

  The gamma correction method is to enable display with a larger number of bits (number of gradations) than the actual number of bits (number of gradations) to be displayed. For example, when displaying with 6 bits (64 gradations), in reality, 8 bits (256 gradations) can be displayed. And when actually displaying, it displays by 6 bits (64 gradations) so that the brightness | luminance of the number of gradations becomes nonlinear. Thereby, gamma correction can be realized.

As an example, FIG. 14 shows a method of selecting a subframe in a case where 6 bits (64 gradations) can be displayed and gamma correction is performed and 5 bits (32 gradations) are displayed. The embodiment of FIG. 14 is similar to the embodiment of FIG. 2 in that three intermediate subframes SF1 to SF3 having the same medium weight (4) and driven in a superposition time gray scale method, Two higher-order subframes SF4 and SF7 having a larger weighting (16, 32) than the subframes SF1 to SF3 and driven in a binary code time gray scale method, and a smaller weighting (1, 2) than the middle-order subframes SF1 to SF3 ) And two lower subframes SF5 and SF6 driven in a binary code time gray scale method. In 6-bit display, the number of gray scales is 0 by selectively lighting these subframes SF1 to SF7. 64 (2 ⁶ ) gradations of 63 to 63 can be displayed. The gamma correction in the 5-bit display is realized by assigning the gradation numbers from 0 to 63 in the 6-bit display to the gradation numbers 0 to 31 in the 5-bit display. That is, in FIG. 14, the number of gradations in 5 bits up to 12 is the same as the number of gradations in 6 bits. However, when the number of gray scales with 5 bits after gamma correction is 13, light is actually turned on by a subframe selection method with 14 bits of gray scale levels. Similarly, when the number of gradations with 5 bits after gamma correction is 14, display is actually performed with 16 gradations with 6 bits, and when gradation number with 5 bits after gamma correction is 15, Actually, the display is performed with 18 bits of 6-bit gradation. In this way, a correspondence table between the number of gradations of 5 bits after gamma correction and the number of gradations of 6 bits may be created and displayed accordingly. Thereby, gamma correction can be realized.

  It should be noted that the correspondence table between the number of gradations of 5 bits after gamma correction and the number of gradations of 6 bits can be changed as appropriate. Therefore, it is possible to easily change the degree of gamma correction by changing the correspondence table.

  The number of bits to be displayed p (p is a natural number) and the number of gamma-corrected bits q (q is a natural number) are arbitrary values. When displaying with gamma correction, it is desirable to increase the number of bits p as much as possible in order to express gradation smoothly. However, if it is made too large, there will be adverse effects such as an increase in the number of subframes. Therefore, it is desirable that the relationship between the number of bits q and the number of bits p is q + 2 ≦ p ≦ q + 5. As a result, it is possible to realize that the number of subframes does not increase too much while the gradation is expressed smoothly.

  As described above, the present invention can also be applied to the case where gamma correction is performed to increase the lighting period (luminance) nonlinearly with respect to the number of gradations.

  So far, the gradation expression method, that is, the subframe selection method has been described. Next, the appearance order of subframes will be described.

  As an example, FIG. 15 shows a pattern example of the appearance order of subframes in the case of FIG. In FIG. 15, the subframes SF4 to SF10 (first subframe group) driven by the overlapping time gray scale method are shown without shading, and the subframes SF1 to SF3 driven by the binary code time gray scale method are shown. (Second subframe group) is shown by shading.

  The first pattern is SF1, SF2, SF3, SF4, SF5, SF6, SF7, SF8, SF9, SF10. The subframes SF1 to SF3 in the binary code time gray scale method are first arranged together (that is, adjacent to each other) to form a binary code subframe region. In this case, as shown in FIG. 2, whenever the binary code subframes SF1 to SF3 change from full lighting to full non-lighting, the subframe SF4 adjacent to the binary code subframe region changes from non-lighting to lighting. To.

  The second pattern is SF4, SF5, SF6, SF7, SF8, SF9, SF10, SF1, SF2, SF3. The subframes SF1 to SF3 in the binary code time gray scale method are arranged lastly and form a binary code subframe region. In this case, the subframe SF10 in contact with the binary code subframe region is driven like the subframe SF4 in FIG. That is, whenever the binary code subframes SF1 to SF3 change from full lighting to full non-lighting, the subframe SF10 changes from non-lighting to lighting.

  The third pattern is SF4, SF5, SF6, SF7, SF1, SF2, SF3, SF9, SF10, SF8. The subframes SF1 to SF3 in the binary code time gray scale method are arranged together in the middle to form a binary code subframe region. In this case, since there are two superposed subframes SF7 and SF9 in contact with the binary code subframe region, either one may be driven as in the subframe SF4 in FIG. That is, whenever the binary code subframes SF1 to SF3 change from all lighting to all non-lighting, the subframe SF7 or SF9 changes from non-lighting to lighting.

  The fourth pattern is SF4, SF5, SF1, SF6, SF7, SF2, SF8, SF9, SF3, SF10. The subframes SF4 to SF10 in the overlapping time gray scale method are sequentially arranged. The subframes SF1 to SF3 in the binary code time gray scale method are also sequentially arranged. Then, after two subframes in the overlapping time gray scale method are arranged, one subframe in the binary code time gray scale method is arranged. The binary code subframes SF1 to SF3 are distributed in one frame and do not form a unified binary code subframe region. In this case, one of the superposed subframes SF9 and SF10 adjacent to the subframe SF3 having the maximum weight among the binary code subframes may be driven as the subframe SF4 in FIG.

  The fifth pattern is SF4, SF5, SF2, SF6, SF7, SF1, SF8, SF9, SF3, SF10. This is a randomized subframe appearance order in the binary code time gray scale method for the fourth pattern. Also in this case, it is preferable to drive either the superposed subframe SF9 or SF10 adjacent to the subframe SF3 having the maximum weight among the binary code subframes as the subframe SF4 in FIG.

  The sixth pattern is SF4, SF8, SF1, SF5, SF10, SF2, SF6, SF9, SF3, SF7. In this case, the appearance order of the subframes in the overlapping time gray scale method is made random with respect to the fourth pattern. In this case, one of the superposed subframes SF9 and SF7 adjacent to the subframe SF3 having the maximum weight among the binary code subframes may be driven as the subframe SF4 in FIG.

  The seventh pattern is SF4, SF8, SF2, SF5, SF10, SF1, SF6, SF9, SF3, SF7. This is a random pattern of the subframe appearance order in the overlapping time gray scale method and the subframe appearance order in the binary code time gray scale method for the fourth pattern. Also in this case, it is preferable to drive either the superposed subframe SF9 or SF7 adjacent to the subframe SF3 having the maximum weight among the binary code subframes as the subframe SF4 in FIG.

  The eighth pattern is SF4, SF5, SF1, SF6, SF2, SF7, SF8, SF9, SF3, SF10. This is because, after two subframes in the superimposition time gray scale method are arranged, one subframe in the binary code time gray scale method is arranged, and one subframe in the superposition time gray scale method is arranged. One subframe in the code time gray scale method is arranged, three subframes in the superposition time gray scale method are arranged, and one additional subframe is arranged. In this case, one of the superposed subframes SF9 and SF10 adjacent to the subframe SF3 having the maximum weight among the binary code subframes may be driven as the subframe SF4 in FIG.

  The ninth pattern is SF4, SF5, SF6, SF7, SF1, SF2, SF8, SF9, SF10, SF3. This is because, after four subframes in the superposition time gray scale method are arranged, two subframes in the binary code time gray scale method are arranged, and three subframes in the superposition time gray scale method are arranged. One subframe in the code time gray scale method is arranged. In this case, it is preferable to drive the overlapping subframe SF10 adjacent to the subframe SF3 having the maximum weight among the binary code subframes as the subframe SF4 in FIG.

  In this way, it is desirable to arrange subframes in the binary code time gray scale method between subframes in the superposition time gray scale method so that the subframes are not unevenly distributed. As a result, the eyes are deceived and pseudo contours can be reduced.

  Note that the order of appearance of subframes may change. For example, the appearance order of subframes may change between the first frame and the second frame. Further, the appearance order of the subframes may be changed depending on the position.

  The normal frame frequency is 60 Hz, but is not limited to this. The pseudo contour may be reduced by increasing the frame frequency. For example, the operation may be performed at a frequency that is about twice that of a normal frequency of 120 Hz.

(Embodiment 2)
In this embodiment, an example of a timing chart is described. As an example, the subframe selection method shown in FIG. 1 is used. However, the subframe selection method is not limited to this, and the method can be easily applied to other subframe selection methods and other gradation numbers.

  In addition, the order in which the subframes appear is SF1, SF2, SF3, SF4, SF5, and SF6 as an example, but is not limited to this, and can be easily applied to other orders.

  First, FIG. 16 shows a timing chart in the case where a period for writing a signal to a pixel and a lighting period are separated. First, in a signal writing period, a signal for one screen is input to all pixels. During this time, the pixels are not lit. After the signal writing period ends, the lighting period starts and the pixels are lit. The length of the lighting period at that time is 1. Next, the next subframe starts, and a signal for one screen is input to all pixels in the signal writing period. During this time, the pixels are not lit. After the signal writing period ends, the lighting period starts and the pixels are lit. The length of the lighting period at that time is 2.

  By repeating the same, the lighting periods are arranged in the order of 4, 4, 4, 16, 1, and 2.

  As described above, the driving method in which the signal writing period and the lighting period are separated from each other is preferably applied to the plasma display. In the case of using for a plasma display, an initialization operation or the like is required. However, it is omitted for simplicity.

  This driving method is also preferably applied to an organic EL display, a field emission display, a display using a digital micromirror device (DMD), and the like.

  FIG. 17 shows a pixel configuration in that case. The gate line 1607 is selected, the selection transistor 1601 is turned on, and a signal is input from the signal line 1605 to the storage capacitor 1602. Then, the current of the driving transistor 1603 is controlled according to the signal, and current flows from the first power supply line 1606 through the display element 1604 to the second power supply line 1608.

  Note that in the signal writing period, the potential of the first power supply line 1606 and the second power supply line 1608 is controlled so that no voltage is applied to the display element 1604. As a result, the display element 1604 can be prevented from being lit during the signal writing period.

  Next, FIG. 18 shows a timing chart in the case where a period for writing a signal to a pixel and a lighting period are not separated. When a signal writing operation is performed in each row, the lighting period starts immediately.

  In a certain row, a signal is written, and after a predetermined lighting period ends, a signal writing operation in the next subframe is started. By repeating this, the length of the lighting period is arranged in the order of 4, 4, 4, 16, 1, 2.

  This makes it possible to arrange many subframes within one frame even if the signal writing operation is slow.

  Such a driving method is preferably applied to a plasma display. In the case of using for a plasma display, an initialization operation or the like is required, but the description is omitted here.

  In addition, this driving method includes a light emitting device such as an organic EL display, an inorganic EL display, a plasma display, a field emission display (FED), a surface electric field display (SED), a digital micromirror device (DMD), and a grating. It is also suitable to apply to a reflective display device such as a light valve (GLV) or a reflective liquid crystal display, or a liquid crystal display device such as a ferroelectric liquid crystal display or an antiferroelectric liquid crystal display.

  An example of the pixel configuration is shown in FIG. The first gate line 1807 is selected, the first selection transistor 1801 is turned on, and a signal is input from the first signal line 1805 to the storage capacitor 1802. Then, the current of the driving transistor 1803 is controlled according to the signal, and current flows from the first power supply line 1806 through the display element 1804 to the second power supply line 1808. Similarly, the second gate line 1817 is selected, the second selection transistor 1811 is turned on, and a signal is input from the second signal line 1815 to the storage capacitor 1802. Then, the current of the driving transistor 1803 is controlled according to the signal, and current flows from the first power supply line 1806 through the display element 1804 to the second power supply line 1808.

  The first gate line 1807 and the second gate line 1817 can be controlled separately. Similarly, the first signal line 1805 and the second signal line 1815 can be controlled separately. Therefore, it is possible to input signals to the pixels for two rows at the same time, so that the driving method as shown in FIG. 18 can be realized.

  Note that the driving method as shown in FIG. 18 can be realized by using the circuit of FIG. A timing chart in that case is shown in FIG. As shown in FIG. 20, one gate selection period is divided into a plurality (two in FIG. 20). Then, each gate line is selected within the divided selection period, and a corresponding signal is input to the signal line 1605 at that time. For example, in one gate selection period, the first half selects the i-th row and the second half selects the j-th row. Then, it is possible to operate as if two rows are selected at the same time in one gate selection period.

  Such a driving method can be applied in combination with the present invention.

  Next, FIG. 21 shows a timing chart in the case of performing an operation of erasing the pixel signal. In each row, a signal writing operation is performed, and the pixel signal is erased before the next signal writing operation is performed. In this way, the length of the lighting period can be easily controlled.

  In a certain row, a signal is written, and after a predetermined lighting period ends, a signal writing operation in the next subframe is started. If the lighting period is short, a signal erasing operation is performed to turn off the light. By repeating such an operation, the lighting periods are arranged in the order of 4, 4, 4, 16, 1, and 2.

  In FIG. 21, the signal erasing operation is performed when the lighting periods are 1 and 2, but the present invention is not limited to this. The erase operation may be performed in other lighting periods.

  This makes it possible to arrange many subframes within one frame even if the signal writing operation is slow. Further, when performing an erasing operation, it is not necessary to acquire erasing data in the same manner as a video signal, so that the driving frequency of the source driver can be reduced.

  Such a driving method is preferably applied to a plasma display. In the case of using for a plasma display, an initialization operation or the like is necessary, but it is omitted for simplicity.

  This driving method is also preferably applied to an organic EL display, a field emission display, a display using a digital micromirror device (DMD), and the like.

  The pixel configuration in that case is shown in FIG. The first gate line 2107 is selected, the selection transistor 2101 is turned on, and a signal is input from the signal line 2105 to the storage capacitor 2102. Then, the current of the driving transistor 2103 is controlled according to the signal, and current flows from the first power supply line 2106 through the display element 2104 to the second power supply line 2108.

  When the signal is to be erased, the second gate line 2117 is selected, the erase transistor 2111 is turned on, and the drive transistor 2103 is turned off. Then, no current flows from the first power supply line 2106 to the second power supply line 2108 through the display element 2104. As a result, a non-lighting period can be created and the length of the lighting period can be freely controlled.

  In FIG. 22, the erase transistor 2111 is used, but another method may be used. This is because it is only necessary to forcibly create a non-lighting period, so that no current is supplied to the display element 2104. Therefore, a non-lighting period may be created by arranging a switch in a path through which a current flows from the first power supply line 2106 to the second power supply line 2108 through the display element 2104 and controlling the on / off of the switch. Alternatively, the gate-source voltage of the drive transistor 2103 may be controlled so that the drive transistor is forcibly turned off.

  An example of a pixel configuration in the case where the driving transistor is forcibly turned off is shown in FIG. A selection transistor 2201, a driving transistor 2203, an erasing diode 2211, and a display element 2204 are provided. The source and drain of the selection transistor 2201 are connected to the signal line 2205 and the gate of the driving transistor 2203, respectively. The gate of the selection transistor 2201 is connected to the first gate line 2107. The source and drain of the driving transistor 2203 are connected to the first power supply line 2206 and the display element 2204, respectively. The erasing diode 2211 is connected to the gate of the driving transistor 2203 and the second gate line 2217.

  The storage capacitor 2202 serves to hold the gate potential of the driving transistor 2203. Therefore, although it is connected between the gate of the driving transistor 2203 and the first power supply line 2206, the present invention is not limited to this. It is only necessary that the gate potential of the driving transistor 2203 be arranged so as to be held. In the case where the gate potential of the driving transistor 2203 can be held using the gate capacitance of the driving transistor 2203 or the like, the holding capacitor 2202 may be omitted.

  As an operation method, the first gate line 2207 is selected, the selection transistor 2201 is turned on, and a signal is input from the signal line 2205 to the storage capacitor 2202. Then, the current of the driving transistor 2203 is controlled according to the signal, and current flows from the first power supply line 2106 to the second power supply line 2108 through the display element 2104.

  When the signal is to be erased, the second gate line 2117 is selected (here, set to a high potential), the erasing diode 2211 is turned on, and a current flows from the second gate line 2117 to the gate of the driving transistor 2203. To. As a result, the driving transistor 2203 is turned off. Then, no current flows from the first power supply line 2206 to the second power supply line 2208 through the display element 2204. As a result, a non-lighting period can be created and the length of the lighting period can be freely controlled.

  When it is desired to hold the signal, the second gate line 2117 is not selected (here, set to a low potential). Then, since the erasing diode 2211 is turned off, the gate potential of the driving transistor 2203 is held.

  The erasing diode 2211 may be anything as long as it has a rectifying property. A PN-type diode, a PIN-type diode, a Schottky diode, or a Zener-type diode may be used.

  Alternatively, a transistor may be used by diode connection (gate and drain connected). A circuit diagram in that case is shown in FIG. As the erasing diode 2211, a diode-connected transistor 2311 is used. Here, an N-channel type is used, but the present invention is not limited to this. A P-channel type may be used.

  As another circuit, the driving method shown in FIG. 21 can be realized by using the circuit shown in FIG. A timing chart in that case is shown in FIG. As shown in FIG. 20, one gate selection period is divided into a plurality (two in FIG. 20). Then, each gate line is selected within the divided selection period, and a signal (a video signal and a signal for erasing) corresponding to the gate line is input to the signal line 1605 at that time. For example, in one gate selection period, the first half selects the i-th row and the second half selects the j-th row. When the i-th row is selected, such a video signal is input. On the other hand, when the j-th row is selected, a signal that turns off the driving transistor is input. Then, it is possible to operate as if two rows are selected at the same time in one gate selection period.

  Such a driving method can be applied in combination with the present invention.

  Note that the timing chart, the pixel configuration, and the driving method shown in this embodiment mode are examples, and the present invention is not limited to this. The present invention can be applied to various timing charts, pixel configurations, and driving methods.

  Note that the appearance order of the subframes may change depending on the time. For example, the appearance order of subframes may change between the first frame and the second frame. Further, the appearance order of the subframes may be changed depending on the position. For example, the appearance order of the subframes may be changed between the pixel A and the pixel B. In addition, by combining them, the appearance order of subframes may change with time and change with position.

  Note that although a lighting period, a signal writing period, and a non-lighting period are arranged in one frame period in this embodiment mode, the present invention is not limited to this. Other operation periods may be arranged. For example, a period in which the voltage applied to the display element has a polarity opposite to that of the normal voltage, that is, a so-called reverse bias period may be provided. By providing the reverse bias period, the reliability of the display element may be improved.

  Note that the pixel structure described in this embodiment is not limited thereto. Any structure can be applied as long as it has a similar function.

  Note that the description in this embodiment can be implemented in free combination with the content described in Embodiment 1.

(Embodiment 3)
In this embodiment mode, an example of a display device using the driving method of the present invention will be described.

  A plasma display is a typical display device. A pixel of a plasma display can take only two states of light emission and non-light emission. Therefore, the time gray scale method is used as one of means for increasing the gray scale. Therefore, the present invention can be applied to that portion.

  Note that in a plasma display, it is necessary to initialize a pixel in addition to writing a signal to the pixel. Therefore, it is desirable that the subframes are sequentially arranged in the portion using the superposition time gray scale method, and that no subframe in the binary code time gray scale method is inserted therebetween. By arranging subframes in this way, the number of pixel initializations can be reduced. As a result, the contrast can be improved.

  However, if subframes in the binary code time gray scale method are arranged together, a pseudo contour is generated due to the portion. Therefore, it is desirable to arrange the subframes in the binary code time gray scale method so as to be dispersed within one frame as much as possible. When subframes in the binary code time gray scale method are used, it is necessary to perform initialization corresponding to each subframe. Therefore, even if the subframes in the binary code time gray scale method are distributed and arranged, it does not cause a big problem. On the other hand, in the case of the overlapping time gray scale subframe, if the lit subframes are arranged continuously, it is not necessary to perform initialization. Therefore, it is desirable that the subframes are sequentially arranged as much as possible.

  Therefore, in the case of using a combination of the superimposing time gray scale subframe and the binary code time gray scale subframe, the subframe appearing in the superposition time gray scale is turned on as the order of appearance of the subframes. It is desirable that the subframes in the binary code time gray scale method are arranged in a distributed manner between the subframes in the superposition time gray scale method. As a result, the number of initializations can be reduced, the contrast can be improved, and the occurrence of pseudo contours can be reduced.

  Examples of display devices other than plasma displays include organic EL displays, field emission displays, displays using digital micromirror devices (DMD), ferroelectric liquid crystal displays, and bistable liquid crystal displays. These are all display devices that can use the time gray scale method. By applying the present invention to these display devices, pseudo contour can be reduced while using the time gray scale method.

  For example, in the case of an organic EL display, it is not necessary to initialize pixels. Therefore, it does not happen that light is emitted during initialization and the contrast is reduced. Therefore, the appearance order of subframes can be set arbitrarily. It is desirable to disperse them so that pseudo contours do not occur as much as possible.

  Therefore, the superframe time gray scale subframes are arranged so that the lit subframes are continuous, and the binary code time grayscale subframes are arranged between the superposition time grayscale subframes. It may be arranged in a distributed manner. As a result, the overlapping time gray scale subframes are arranged to some extent within one frame. Therefore, when changing from the first frame to the second frame, it is possible to reduce the occurrence of a pseudo contour at the change. So-called moving image pseudo contour can be reduced. In addition, since the subframes in the binary code time gray scale method are arranged in a distributed manner, pseudo contour can be reduced.

  In addition, the superframe time gray scale subframes may be distributed and the binary code time grayscale subframes may be distributed. As a result, the pseudo contour caused by the binary code time gray scale method is mixed with the superframe time gray scale subframe, so that the effect of reducing the pseudo contour as a whole is enhanced.

  Note that the description in this embodiment can be implemented in free combination with the contents described in Embodiments 1 and 2.

(Embodiment 4)
In this embodiment, structures and operations of a display device, a signal line driver circuit, a gate line driver circuit, and the like are described.

  As shown in FIG. 25, the display device includes a pixel array 2401, a gate line driver circuit 2402, and a signal line driver circuit 2410. The gate line driver circuit 2402 sequentially outputs a selection signal to the pixel array 2401. The gate line driver circuit 2402 includes a shift register, a buffer circuit, and the like.

  In addition, the gate line driver circuit 2402 often includes a level shifter circuit, a pulse width control circuit, and the like. The signal line driver circuit 2410 sequentially outputs video signals to the pixel array 2401. The shift register 2403 outputs a pulse that sequentially selects gate lines. In the pixel array 2401, an image is displayed by controlling the light state according to the video signal. A video signal input from the signal line driver circuit 2410 to the pixel array 2401 is often a voltage. In other words, the display elements arranged in each pixel and the elements that control the display elements change states according to the video signal (voltage) input from the signal line driver circuit 2410. Examples of the display element arranged in the pixel include an EL element, an element used in an FED (field emission display), a liquid crystal, a DMD (digital micromirror device), and the like.

  Note that a plurality of gate line driver circuits 2402 and signal line driver circuits 2410 may be provided.

  The signal line driver circuit 2410 is divided into a plurality of parts. Roughly, as an example, it is divided into a shift register 2403, a first latch circuit (LAT1) 2404, a second latch circuit (LAT2) 2405, and an amplifier circuit 2406. The amplifier circuit 2406 may have a function of converting a digital signal into an analog signal or a function of performing gamma correction.

  Further, the pixel has a display element such as an EL element. A circuit that outputs a current (video signal) to the display element, that is, a current source circuit may be provided.

  Therefore, the operation of the signal line driver circuit 2410 will be briefly described. The shift register 2403 receives a clock signal (S-CLK), a start pulse (SP), and a clock inversion signal (S-CLKb), and sequentially outputs sampling pulses according to the timing of these signals.

  The sampling pulse output from the shift register 2403 is input to the first latch circuit (LAT1) 2404. The first latch circuit (LAT1) 2404 receives a video signal from the video signal line 2408, and holds the video signal in each column in accordance with the timing at which the sampling pulse is input.

  When the first latch circuit (LAT1) 2404 completes holding the video signal up to the last column, a latch pulse (Latch Pulse) is input from the latch control line 2409 during the horizontal blanking period, and the first latch circuit (LAT1) The video signals held in 2404 are transferred all at once to the second latch circuit (LAT2) 2405. After that, the video signal held in the second latch circuit (LAT2) 2405 is input to the amplifier circuit 2406 for one row at the same time. A signal output from the amplifier circuit 2406 is input to the pixel array 2401.

  While the video signal held in the second latch circuit (LAT2) 2405 is input to the amplifier circuit 2406 and is input to the pixel array 2401, the shift register 2403 outputs a sampling pulse again. That is, two operations are performed simultaneously. Thereby, line-sequential driving becomes possible. Thereafter, this operation is repeated.

  Note that the signal line driver circuit and a part thereof (such as a current source circuit and an amplifier circuit) do not exist on the same substrate as the pixel array 2401, and may be configured using, for example, an external IC chip.

  Note that the structures of the signal line driver circuit, the gate line driver circuit, and the like are not limited to those in FIGS. For example, a signal may be supplied to the pixel by dot sequential driving. An example of the signal line driver circuit 2510 in that case is shown in FIG. A sampling pulse is output from the shift register 2503 to the sampling circuit 2504. A video signal is input from the video signal line 2508, and the video signal is output to the pixel 2501 in accordance with the sampling pulse.

  Note that as described above, the transistor in the present invention may be any type of transistor, and may be formed on any substrate. Therefore, the circuits as shown in FIGS. 25 and 26 may all be formed on a glass substrate, may be formed on a plastic substrate, or may be formed on a single crystal substrate. It may be formed on an SOI substrate or on any substrate. Alternatively, part of the circuit in FIGS. 25 and 26 may be formed on a certain substrate, and another part of the circuit in FIGS. 25 and 26 may be formed on another substrate. That is, all the circuits in FIGS. 25 and 26 may not be formed over the same substrate. For example, in FIGS. 25 and 26, the pixel array 2401 and the gate line driver circuit 2402 are formed using a TFT over a glass substrate, and the signal line driver circuit 2410 (or part thereof) is formed over a single crystal substrate. Then, the IC chips may be connected to each other by COG (Chip On Glass) and placed on the glass substrate. Alternatively, the IC chip may be connected to the glass substrate using TAB (Tape Auto Bonding) or a printed board.

  Note that the contents described in the present embodiment correspond to those using the contents described in the first to third embodiments. Therefore, the contents described in Embodiments 1 to 3 can be applied to this embodiment.

(Embodiment 5)
Next, a pixel layout in the display device of the present invention will be described. As an example, FIG. 27 shows a layout diagram of the circuit diagram shown in FIG. Note that the circuit diagram and the layout diagram are not limited to FIGS. 24 and 27.

  Power supplies for the selection transistor 2601, the driving transistor 2603, the erasing transistor 2611, and the display element 2604 are provided. The source and drain of the selection transistor 2601 are connected to the signal line 2605 and the gate of the driving transistor 2603, respectively. The gate of the selection transistor 2601 is connected to the first gate line 2107. The source and drain of the driving transistor 2603 are connected to the power supply line 2606 and the display element 2604, respectively. The diode-connected erase transistor 2611 is connected to the gate of the drive transistor 2603 and the second gate line 2617. The storage capacitor 2602 is connected between the gate of the driving transistor 2603 and the power supply line 2606.

  The signal line 2605 and the power supply line 2606 are formed by the second wiring, and the first gate line 2107 and the second gate line 2617 are formed by the first wiring.

  In the case of the top gate structure, the film is formed in the order of the substrate, the semiconductor layer, the gate insulating film, the first wiring functioning as the gate electrode, the interlayer insulating film, and the second wiring functioning as the source / drain electrodes. In the case of the bottom gate structure, the film is formed in the order of the substrate, the first wiring functioning as the gate electrode, the gate insulating film, the semiconductor layer, the interlayer insulating film, and the second wiring functioning as the source / drain electrodes.

Note that the contents described in this embodiment can be implemented by being freely combined with the contents described in Embodiments 1 to 4.

(Embodiment 6)
In the present embodiment, hardware for controlling the driving method described in the first to fifth embodiments will be described.

  A rough block diagram is shown in FIG. A pixel array 2704 is arranged on the substrate 2701. In many cases, the signal line driver circuit 2706 and the gate line driver circuit 2705 are provided. In addition, a power supply circuit, a precharge circuit, a timing generation circuit, and the like may be arranged. In some cases, the signal line driver circuit 2706 and the gate line driver circuit 2705 are not provided. In that case, what is not arranged on the substrate 2701 is often formed in an IC. In many cases, the IC is disposed on the substrate 2701 by COG (Chip On Glass). Alternatively, an IC may be disposed on a connection board 2707 that connects the peripheral circuit board 2702 and the board 2701.

  A signal 2703 is input to the peripheral circuit board 2702. Then, the controller 2708 controls and the signal is stored in the memory 2709, the memory 2710, or the like. In the case where the signal 2703 is an analog signal, it is often stored in the memory 2709 or the memory 2710 after analog-digital conversion. Then, the controller 2708 outputs a signal to the substrate 2701 using a signal stored in the memory 2709, the memory 2710, or the like.

  In order to realize the driving method described in Embodiment Modes 1 to 5, the controller 2708 controls the appearance order of subframes and outputs a signal to the substrate 2701.

  Note that the contents described in this embodiment mode can be implemented by being freely combined with the contents described in Embodiment Modes 1 to 5.

(Embodiment 7)
An example of a structure of a mobile phone including a display device and a display device using the driving method of the present invention in a display portion will be described with reference to FIG.

  The display panel 5410 is incorporated in a housing 5400 so as to be detachable. The shape and dimensions of the housing 5400 can be changed as appropriate in accordance with the size of the display panel 5410. A housing 5400 to which the display panel 5410 is fixed is fitted into a printed board 5401 and assembled as a module.

  The display panel 5410 is connected to the printed board 5401 through the FPC 5411. A signal processing circuit 5405 including a speaker 5402, a microphone 5403, a transmission / reception circuit 5404, a CPU, a controller, and the like is formed over the printed board 5401. Such a module is combined with the input means 5406 and the battery 5407 and housed in the housings 5409 and 5412. The pixel portion of the display panel 5410 is arranged so as to be visible from an opening window formed in the housing 5412.

  In the display panel 5410, a pixel portion and some peripheral driver circuits (a driver circuit having a low operating frequency among a plurality of driver circuits) are formed over a substrate using TFTs, and some peripheral driver circuits (a plurality of driver circuits) are formed. A driving circuit having a high operating frequency among the circuits) may be formed over the IC chip, and the IC chip may be mounted on the display panel 5410 by COG (Chip On Glass). Alternatively, the IC chip may be connected to a wiring formed on the glass substrate using TAB (Tape Auto Bonding) or a printed board. Note that FIG. 30A shows an example of a configuration of a display panel in which some peripheral drive circuits are formed integrally with a pixel portion on a substrate and an IC chip on which other peripheral drive circuits are formed is mounted by COG or the like. is there. 30A includes a substrate 5300, a signal line driver circuit 5301, a pixel portion 5302, a scanning line driver circuit 5303, a scanning line driver circuit 5304, an FPC 5305, an IC chip 5306, an IC chip 5307, a seal, and the like. A stop substrate 5308 and a sealant 5309 are provided. With such a structure, low power consumption of the display device can be achieved, and the use time by one charge of the mobile phone can be extended. In addition, the cost of the mobile phone can be reduced.

  In addition, by performing impedance conversion of a signal set to the scanning line or the signal line using a buffer, the pixel writing time for each row can be shortened. Therefore, a high-definition display device can be provided.

  In order to further reduce power consumption, a pixel portion is formed on a substrate using TFTs as shown in FIG. 30B, and all peripheral drive circuits are formed on an IC chip. The display panel may be mounted by COG (Chip On Glass) or the like. 30B includes a substrate 5310, a signal line driver circuit 5311, a pixel portion 5312, a scanning line driver circuit 5313, a scanning line driver circuit 5314, an FPC 5315, an IC chip 5316, an IC chip 5317, a seal, and the like. A stop substrate 5318 and a sealant 5319 are provided.

  Then, by using the display device of the present invention and its driving method, an image with reduced pseudo contour can be displayed. Therefore, even an image whose gradation is slightly changed like human skin can be displayed with a reduced pseudo contour.

  The configuration described in this embodiment is an example of a mobile phone, and the display device of the present invention is not limited to the mobile phone having such a configuration, and can be applied to mobile phones having various configurations.

(Embodiment 8)
FIG. 31 shows an EL module in which a display panel 5701 and a circuit board 5702 are combined. A display panel 5701 includes a pixel portion 5703, a scan line driver circuit 5704, and a signal line driver circuit 5705. On the circuit board 5702, for example, a control circuit 5706, a signal dividing circuit 5707, and the like are formed. The display panel 5701 and the circuit board 5702 are connected to each other through a connection wiring 5708. An FPC or the like can be used for the connection wiring.

  The control circuit 5706 corresponds to the controller 2708, the memory 2709, the memory 2710, and the like in the seventh embodiment. The control circuit 5706 mainly controls the appearance order of subframes.

  In the display panel 5701, a pixel portion and some peripheral driver circuits (a driver circuit having a low operating frequency among the plurality of driver circuits) are formed over the substrate using TFTs, and some peripheral driver circuits (a plurality of driver circuits) are formed. A driver circuit having a high operating frequency among the circuits) is formed over the IC chip, and the IC chip is preferably mounted on the display panel 5701 by COG (Chip On Glass) or the like. Alternatively, the IC chip may be mounted on the display panel 5701 using TAB (Tape Auto Bonding) or a printed board. Note that FIG. 30A shows an example of a configuration in which some peripheral drive circuits are formed integrally with a pixel portion on a substrate and an IC chip on which other peripheral drive circuits are formed is mounted by COG or the like. With such a structure, low power consumption of the display device can be achieved, and the use time by one charge of the mobile phone can be extended. In addition, the cost of the mobile phone can be reduced.

  In addition, by performing impedance conversion of a signal set to the scanning line or the signal line using a buffer, the pixel writing time for each row can be shortened. Therefore, a high-definition display device can be provided.

  In order to further reduce power consumption, a pixel portion is formed using a TFT on a glass substrate, all signal line driver circuits are formed on an IC chip, and the IC chip is displayed on a COG (Chip On Glass) display. It may be mounted on a panel.

  Note that a pixel portion is formed using a TFT over a substrate, all peripheral driver circuits are formed over an IC chip, and the IC chip is mounted on a display panel by COG (Chip On Glass). FIG. 30B shows an example of a configuration in which an IC chip in which a pixel portion is formed over a substrate and a signal line driver circuit is formed over the substrate is mounted by COG or the like.

  With this EL module, an EL television receiver can be completed. FIG. 32 is a block diagram illustrating a main configuration of an EL television receiver. A tuner 5801 receives video signals and audio signals. The video signal includes a video signal amplifying circuit 5802, a video signal processing circuit 5803 that converts a signal output from the video signal into a color signal corresponding to each color of red, green, and blue, and uses the video signal as input specifications of the drive circuit. Processing is performed by a control circuit 5706 for conversion. The control circuit 5706 outputs a signal to each of the scan line side and the signal line side. In the case of digital driving, a signal dividing circuit 5707 may be provided on the signal line side, and an input digital signal may be divided into m pieces and supplied.

  Of the signals received by the tuner 5801, the audio signal is sent to the audio signal amplifier circuit 5804, and the output is supplied to the speaker 5806 via the audio signal processing circuit 5805. The control circuit 5807 receives control information on the receiving station (reception frequency) and volume from the input unit 5808 and sends a signal to the tuner 5801 and the audio signal processing circuit 5805.

  A television receiver can be completed by incorporating an EL module into a housing. A display portion is formed by the EL module. In addition, speakers, video input terminals, and the like are provided as appropriate.

  Of course, the present invention is not limited to a television receiver, and is applied to various uses as a display medium of a particularly large area such as a monitor of a personal computer, an information display board in a railway station or airport, an advertisement display board in a street, etc. can do.

  As described above, by using the display device of the present invention and its driving method, an image with a reduced pseudo contour can be seen. Therefore, even an image whose gradation is slightly changed like human skin can be displayed with a reduced pseudo contour.

(Embodiment 9)
Electronic devices to which the present invention can be applied include desktop, floor-standing, or wall-mounted displays, video cameras, digital cameras, goggles-type displays (head-mounted displays), navigation systems, sound playback devices (car audio, audio components, etc.), Recording on a recording medium such as a computer, a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), or an image playback device (specifically, Digital Versatile Disc (DVD)) equipped with a recording medium For example, a device having a display capable of playing back and displaying the recorded video and still images. Specific examples of these electronic devices are illustrated in FIGS.

  FIG. 33A shows a desktop, floor-standing, or wall-mounted display, which includes a housing 301, a support base 302, a display portion 303, a speaker portion 304, a video input terminal 305, and the like. The present invention can be used for a display device constituting the display unit 303. Such a display can be used as an arbitrary information display device such as a personal computer, a TV broadcast receiver, and an advertisement display. As a result, it is possible to provide a display capable of displaying without false contours.

  FIG. 33B shows a digital camera, which includes a main body 311, a display portion 312, an image receiving portion 313, operation keys 314, an external connection port 315, a shutter 316, and the like. The present invention can be used for a display device constituting the display unit 312. As a result, it is possible to provide a digital camera that can display without false contours.

  FIG. 33C illustrates a computer, which includes a main body 321, a housing 322, a display portion 323, a keyboard 324, an external connection port 325, a pointing mouse 326, and the like. The present invention can be used for a display device constituting the display portion 323. As a result, it is possible to provide a computer that can perform display without false contours. The computer includes a so-called notebook computer equipped with a central processing unit (CPU), a recording medium, and the like, and a so-called desktop computer separated.

  FIG. 33D illustrates a mobile computer, which includes a main body 331, a display portion 332, a switch 333, operation keys 334, an infrared port 335, and the like. The present invention can be used for a display device constituting the display portion 332. As a result, it is possible to provide a mobile computer that can perform display without false contours.

  FIG. 33E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 341, a housing 342, a first display portion 343, a second display portion 344, and a recording medium. (DVD etc.) A reading unit 345, operation keys 346, a speaker unit 347 and the like are included. Although the first display unit 343 mainly displays image information and the second display unit 344 mainly displays character information, the present invention can be used for display devices that constitute the first and second display units 343 and 344. . As a result, it is possible to provide an image reproduction device that can perform display without false contours. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.

  FIG. 33F illustrates a goggle type display (head mounted display), which includes a main body 351, a display portion 352, and an arm portion 353. The present invention can be used for a display device constituting the display portion 352. As a result, it is possible to provide a goggle type display capable of performing display without false contours.

  FIG. 33G shows a video camera, which includes a main body 361, a display portion 362, a housing 363, an external connection port 364, a remote control receiving portion 365, an image receiving portion 366, a battery 367, an audio input portion 368, operation keys 369, and the like. . The present invention can be used for a display device constituting the display portion 362. As a result, it is possible to provide a video camera that can display without false contours.

  FIG. 33H illustrates a mobile phone, which includes a main body 371, a housing 372, a display portion 373, a sound input portion 374, a sound output portion 375, operation keys 376, an external connection port 377, an antenna 378, and the like. The present invention can be used for a display device constituting the display portion 373. As a result, a mobile phone that can display without false contours can be provided.

  The display unit of the electronic device as described above may be a self-luminous type using a light emitting element such as an LED or an organic EL for each pixel, or may use another light source such as a backlight like a liquid crystal display. However, in the case of a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained.

  In addition, the electronic device is often used as a TV receiver when displaying information distributed through an electronic communication line such as the Internet or CATV (cable TV), and in particular, the opportunity to display moving image information has increased. ing. When the display unit is a self-luminous type, the response speed of a light emitting material such as an organic EL is much faster than that of liquid crystal, which is suitable for such moving image display. Moreover, it is preferable also in performing time-division driving. If the light emission luminance of the light emitting material is increased, the light containing the output image information can be enlarged and projected by a lens or the like and used for a front type or rear type projector.

  In the self-luminous display unit, the light emitting part consumes power, and thus it is desirable to display information so that the light emitting part is minimized. Therefore, when a display unit mainly including character information such as a portable information terminal, particularly a mobile phone or a sound reproducing device is a self-luminous type, the character information is formed by the light emitting part with the non-light emitting part as the background. It is desirable to drive.

  As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields.

6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 6A and 6B are diagrams illustrating a display device driving method according to an embodiment of the present invention. 4A and 4B illustrate a structure of a driving method of a display device of the present invention. 4A and 4B illustrate a structure of a driving method of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. 4A and 4B illustrate a structure of a driving method of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. 4A and 4B illustrate a structure of a driving method of a display device of the present invention. 4A and 4B illustrate a structure of a driving method of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 14 illustrates an electronic device to which the present invention is applied. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 14 illustrates an electronic device to which the present invention is applied. FIG. 6 illustrates a structure of a display device of the present invention. FIG. 14 illustrates an electronic device to which the present invention is applied. 8A and 8B illustrate a structure of a conventional display device driving method. 10A and 10B illustrate a driving method of a conventional display device. 8A and 8B illustrate another example of a conventional display device driving method.

Explanation of symbols

301 Housing 322 Housing 342 Housing 363 Housing 372 Housing 1601 Selection transistor 1602 Holding capacitor 1603 Driving transistor 1604 Display element 1605 Signal line 1606 First power supply line 1607 Gate line 1608 Second power supply line 1801 First selection transistor 1802 Holding Capacitor 1803 Drive transistor 1804 Display element 1805 First signal line 1806 First power line 1807 First gate line 1808 Second power line 1811 Second selection transistor 1815 Second signal line 1817 Second gate line 2101 Selection transistor 2102 Storage capacitor 2103 Drive Transistor 2103 Drive transistor 2104 Display element 2105 Signal line 2106 First power line 2107 First gate line 2108 Second power line 2111 Erase transistor 2117 Second gate line 22 1 Selection Transistor 2202 Retention Capacitor 2203 Drive Transistor 2204 Display Element 2205 Signal Line 2206 First Power Line 2207 First Gate Line 2208 Second Power Line 2211 Erase Diode 2217 Second Gate Line 2311 Transistor 2401 Pixel Array 2402 Gate Line Driver Circuit 2408 Video Signal line 2410 Signal line drive circuit 2508 Video signal line 2510 Signal line drive circuit 2601 Selection transistor 2602 Retention capacitor 2603 Drive transistor 2604 Display element 2605 Signal line 2606 Power supply line 2611 Erase transistor 2617 Second gate line 2701 Substrate 2702 Peripheral circuit board 2704 Pixel Array 2705 Gate line drive circuit 2706 Signal line drive circuit 2707 Connection board 2708 Controller 2709 Memory 2710 Memory 5 00 substrate 5301 signal line driver circuit 5302 pixel portion 5303 scanning line driver circuit 5304 scanning line driver circuit 5305 FPC
5306 IC chip 5307 IC chip 5308 Sealing substrate 5309 Sealing material 5310 Substrate 5311 Signal line driver circuit 5312 Pixel portion 5313 Scan line driver circuit 5314 Scan line driver circuit 5315 FPC
5316 IC chip 5317 IC chip 5318 Sealing substrate 5319 Sealing material 5400 Housing 5401 Printed circuit board 5402 Speaker 5403 Microphone 5404 Transmission / reception circuit 5405 Signal processing circuit 5406 Input means 5407 Battery 5409 Housing 5410 Display panel 5411 FPC
5412 Housing 5701 Display panel 5702 Circuit board 5703 Pixel portion 5704 Scanning line driving circuit 5705 Signal line driving circuit 5706 Control circuit 5707 Signal dividing circuit 5708 Connection wiring 5802 Video signal amplification circuit 5803 Video signal processing circuit 5804 Audio signal amplification circuit 5805 Audio signal Processing circuit

Claims (6)

A method of driving a display device that divides one frame into a plurality of subframes to express gradation,
The plurality of subframes are:
A first subframe group that is driven in a superposition time gray scale method and includes a plurality of subframes having the same weighting;
A second subframe group comprising a plurality of subframes having a smaller weight than a subframe of the first subframe group;
The second subframe group is arranged adjacent to each other in one frame to form a subframe region,
Whenever the sub-frame of the second sub-frame group changes from full lighting to full non-lighting due to an increase in the number of gradations, the sub-frame region among the sub-frames belonging to the first sub-frame group is temporally changed. The adjacent subframe is changed from non-lighting to lighting, and the lighting / non-lighting state of subframes other than the subframes changing from non-lighting to lighting is changed among the subframes belonging to the first subframe group. the driving method of a display device characterized by being so free. A method of driving a display device that divides one frame into a plurality of subframes to express gradation,
The plurality of subframes are:
A first subframe group that is driven in a superposition time gray scale method and includes a plurality of subframes having the same weighting;
A second subframe group comprising a plurality of subframes having a smaller weight than a subframe of the first subframe group;
Whenever the subframe of the second subframe group changes from full lighting to full nonlighting due to an increase in the number of gradations, the second subframe group among the subframes belonging to the first subframe group is changed to the second subframe group. A subframe that is temporally adjacent to a subframe having the largest weight among subframes belonging to the subframe changes from non-lighting to lighting, and among the subframes belonging to the first subframe group, from the non-lighting. A driving method of a display device, characterized in that lighting / non-lighting states of sub-frames other than sub-frames that change to lighting are not changed .   3. The display device driving method according to claim 1, wherein a plurality of subframes of the second subframe group are used in a binary code time gray scale method. 4.   The display device driving method according to claim 1, wherein a plurality of subframes of the second subframe group are used in an overlapping time gray scale method. 5. The sub-frame that changes from non-lighting to lighting is also lit at the next gray level after the gray level at which the second sub-frame group changes from full lighting to all non-lighting . The driving method of the display device according to any one of the above.   6. The display according to claim 1, wherein the display device includes an organic electroluminescence display, an inorganic electroluminescence display, a plasma display, a field emission display, a surface electric field display, a digital micromirror device, and a grating light valve. A display device driving method comprising: a display having a liquid crystal display; a reflective liquid crystal display; a ferroelectric liquid crystal display; or an antiferroelectric liquid crystal display.

Images